Kari-Pekka Martimo - UEF · Kari-Pekka Martimo Musculoskeletal disorders, disability and work...

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Musculoskeletal disorders, disability and work

People and WorkResearch Reports 89

Kari-Pekka Martimo

Musculoskeletal disorders, disability and w

ari-Pekka Martim

oMusculoskeletal disorders (MSD) are the most important causes of temporary and permanent work disability. The aim of this thesis was to examine the role of work in the disability caused by MSD from various perspectives: primary prevention using lifting advice and devices, perception of work-relatedness, measurement of productivity loss, and secondary/tertiary prevention through ergonomic intervention or part-time sick leave. The original articles include a systematic review, two surveys, a randomised controlled trial, and a study protocol. The results support the early use of a biopsychosocial model for effective management of disability.

People and Work

Editor in chief Harri Vainio

Scientific editors Raoul Grönqvist Irja Kandolin Timo Kauppinen Kari Kurppa Anneli Leppänen Hannu Rintamäki Riitta Sauni

Editor Virve Mertanen

Address Finnish Institute of Occupational Health Topeliuksenkatu 41 a A FI-00250 Helsinki Tel. +358- 30 4741 Fax +358-9 477 5071 www.ttl.fi

Layout Juvenes Print / Katja Hakala Cover Picture Sami Rantanen ISBN 978-951-802-987-1 (paperback) 978-951-802-988-8 (PDF) ISSN-L 1237-6183 ISSN 1237-6183 Press Tampereen Yliopistopaino Oy – Juvenes Print, Tampere 2010

MUSCULOSKELETAL DISORDERS, DISABILITY AND WORK

Kari-Pekka Martimo

People and Work Research Reports 89

Finnish Institute of Occupational Health, Helsinki, Finland

DOCTORAL DISSERTATION

Supervisors: ProfessorEiraViikari-Juntura FinnishInstituteofOccupationalHealth Helsinki,Finland

DocentMariAntti-Poika UniversityofHelsinki Helsinki,Finland ProfessorKajHusman FinnishInstituteofOccupationalHealth Helsinki,Finland

Reviewers: DocentMarjaMikkelsson UniversityofTurkuand Päijät-HämeSocialandHealthCareGroup Lahti,Finland

ProfessorHannuVirokannas UniversityofOulu Oulu,Finland

Opponent: ProfessorSakariTola MutualPensionInsuranceCompanyVarma Helsinki,Finland

ABSTRACT

Musculoskeletaldisorders(MSD)arethemostimportantcauseoftem-poraryworkdisabilityinFinland,andtogetherwithmentaldisorders,theyaccountforthemajorityofpermanentdisabilitypensions.Themostcommonmusculoskeletalproblemintheworkingpopulationislowbackpain(LBP),whichtogetherwithsomeupperextremitydisorders(UED)hasthestrongestscientificevidenceofallMSD,thatworkingconditionshavearoleintheaetiology.

Thisthesisconsistsoffivestudiesrepresentingthreepossibleap-proachestoreducingdisabilityduetoMSDatwork;preventionofthedisordersbyreducingtheirwork-relatedriskfactors(primarypreven-tion),preventionofdisabilityasaconsequenceoftheexistingMSD(secondaryprevention),andpreventionoftheexacerbationofdisability(secondaryandtertiaryprevention).Thestudiesexamineworkactivityasariskfactor,butalsoasanindicatorofthelevelofdisabilityandasanopportunityforrehabilitation.

Themethodsusedinprimarypreventiontochangeworkingroutinesarenotsupportedbyevidencegatheredinasystematicreviewshow-ingthatwidelyadaptedtraininginliftingtechniquesdoesnothelptopreventLBP.Earlierstudiesingeneralhaveshownonlymodesteffectsofwork-relatedinterventionsintheprimarypreventionofMSD.Intermsofsecondaryprevention,thecross-sectionalsurveyrevealedthatmanyworkerswithMSDconsiderthemselvesaspartiallyabletoworkinsteadofeithertotallyableorunable.Theyalsofrequentlyperceivetheirmusculoskeletalhealthproblemsasbeingrelatedtowork,andthebeliefwasshowntocorrelatewithself-assesseddisability.Manyworkers,however,considerthattherearepossiblechangesthatcouldbeinitiatedintheworkplacetogivethemsupportinworkingdespitetheirMSD.

ABSTRACT

Accordingtoanothersurvey,medicallyverifiedUEDcausesignificantproductivitylossatwork,evenwhentheemployeesdonotneedsickleavebecauseofthesymptoms.ThislostproductivityisusuallynotincludedineconomicevaluationsoftheconsequencesofMSDatwork.IntheassessmentofemployeeswithMSD,productivitylossshouldbetakenintoconsiderationinadditiontocollectingdataonself-assessedwork-relatednessofthedisorder.Ifthedisordercannotbemedicallycured,thenthechallengeforallparties,i.e.theemployee,employerandhealthserviceprovider,istoaccommodateworkinordertoavoiddeteriorationofthesymptomsduetowork,and,ontheotherhand,impairmentofworkoutputbecauseofthesymptoms.

Earlyergonomicinterventiontogetherwithadequatemedicalcarerestoreddecreasedon-the-jobproductivityassociatedwithUEDbetterthanmedicalcarealone.Thisrandomisedcontrolledtrialaddstotherelativelyscarcebodyofworkontheeffectivenessofergonomicinterven-tions.TheresultsalsoencourageoccupationalhealthpersonneltotryforanearlyinteractionwiththesupervisorandtoanergonomicworksitevisitifUEDisthemaincomplaintoftheemployee.Comparedtoregularhealthcarepractices,thestudyinterventionwasinitiatedatanearlierstage.MostoftenintheacutephaseofMSD,apurelybiomedicalmodelofdisabilityisapplied.Onlywhenthedisabilitybecomesprolonged,aremorework-orientedactionstaken.Accordingtothepresentresults,however,ergonomicinterventionislesseffectivewhenappliedatamoreseverestageofUED.

BasedonthefindingthatpartialworkabilityiscommonamongemployeeswithMSD,thebeneficialeffectsofmodifiedworkonreturntoworkinearlierstudies,andthepositiveattitudestopart-timesickleavereportedinotherNordiccountries,arandomisedcontrolledtrialwasdesignedandinitiatedtocomparepart-timesickleaveandconven-tionalsicknessabsenceinthemanagementofMSD.Duringpart-timesickleave,theemployeeisadvisedandsupportedtocontinueworkingsothattherecoveryprocessisnotendangered,andbothworkingtimeandworktasksaremodifiedincollaborationwiththesupervisor.Theresultsofthistrialcanbeexpectedin2011.

ThisthesisshowsthatdisabilitycausedbyMSDcanbemanagedeffectively,especiallyintheoccupationalhealthservices.Despitetheevidencethatliftingadvicehasnoeffectivenessinprimaryprevention,

ABSTRACT

thesecondstudydiddetectencouragingresultsatthelevelofsecondaryprevention.ThisapproachchallengesthemanagementofworkerswithMSDutilisingonlythebiomedicalmodel.Theresultsencouragetheadaptationofabiopsychosocialmodel,wherethemainfocusisshiftedfrompossibleanatomiccausestowardsmorecomplexsystemsofworkdisability.Inthismodel,theimportanceofstakeholderinteractions(forexample,family,supervisor,co-workers,employer,andinsurancecompany)isstressedtogetherwiththecrucialroleoftheindividual.

ThemajorityofbarriersandfacilitatorsofstayingatworkdespiteMSDarerelatedmoretopsychosocial,workplaceandmanagementissuesratherthantothephysicaldisorderitself.Therefore,thediseasediagnosisperspectiveinthemanagementofMSDhastobesupplementedbyadisabilitydiagnosis,byinvestigatingitscausalpsychosocialandenviron-mentalfactors.Theapproachsupportseffectivedisabilitymanagementstrategies,whichpreventunnecessarysicknessabsenteeismandallowemployeestoremainproductiveatworkdespiteMSD.

YhTEENvETO

OhimeneväätyökyvyttömyyttäaiheuttavatSuomessaenitentuki-jaliikuntaelinsairaudet.Yhdessämielenterveyshäiriöidenkanssaneovatyleisinsyypysyviintyökyvyttömyyseläkkeisiin.Tavallisinliikuntaelinvai-vatyöikäisilläonalaselkäkipu.Kaikistaliikuntaelinvaivoistaselkäkivunjajoidenkinyläraajasairauksiensuhteenonenitennäyttöä,ettätyölläjatyöolosuhteillaonmerkitystänäidenvaivojensynnyssä.

Tämäväitöskirjakoostuuviidestäosatutkimuksesta,jotkaedustavatkolmeamahdollisuuttavähentääliikuntaelinsairauksistaaiheutuvaatyökyvynlaskua;ennaltaehkäisemällävaivojavähentämälläniidentyö-peräisiäriskitekijöitä(primaaripreventio),vähentämälläolemassaolevistavaivoistaaiheutuvaatyökyvynlaskua(sekundaaripreventio)sekäestä-mällätyökyvynlaskunpaheneminen(sekundaari-jatertiaaripreventio).Väitöskirjakäsitteleetyötoimintaariskitekijänä,muttamyöstyökyvynmittarinajakuntoutumismahdollisuutena.

Primaaripreventiossakäytetyttyöskentelytapoihinkohdistuneetmenetelmättulevatkyseenalaistetuiksitässätutkimuksessa.Järjestel-mällisessäkirjallisuuskatsauksessaosoitetaan,ettälaajaltikäytössäolevanostotekniikoidenopettamineneiautakaanehkäisemäänalaselkäkipuataakankäsittelyssä.Aikaisemmatkintutkimuksetovatyleensäosoitta-neet,ettätyöperäisilläinterventioillaonvainvaatimattomiavaikutuksialiikuntaelinvaivojenprimaaripreventiossa.Sekundaaripreventionosaltapoikittaistutkimuksessaosoitetaan,ettämonettyöntekijätovatmieles-täänliikuntaelinvaivastahuolimattaosittaintyökykyisiäsensijaan,ettäpitäisivätitseäänjokotäysintyökykyisinätaityökyvyttöminä.Heidänmielestäänliikuntaelinvaivatovatuseinmyöstyöperäisiä,millätutki-muksessaosoitetaanolevanyhteyttäitsearvioituuntyökyvynlaskuun.

YHTEENVETO

Monientyöntekijöidenmielestätyöpaikallaonkuitenkinmahdolli-suuksiasellaisiinmuutoksiin,jotkaauttavatheitäselviytymääntyössäänliikuntaelinvaivastahuolimatta.

Toisenpoikkileikkaustutkimuksenmukaanlääkärintoteamaylä-raajavaivaaiheuttaamerkittäväätuottavuudenalenemaatyössämyössilloin,kuntyöntekijäeioleoireidenvuoksisairauslomantarpeessa.Tätätuottavuudenalenemaaeiyleensähuomioida,kunarvioidaanliikuntaelinvaivojenaiheuttamiataloudellisiaseurauksiatyössä.Lii-kuntaelinoireisentyöntekijäntutkimisessatulisihuomioidasairaudestaaiheutuvatuottavuudenlaskusamoinkuintyöntekijänomaarviovaivantyöperäisyydestä.Vaikkasairauttaeivoilääketieteellisestiparantaa,työn-tekijän,työnantajanjaterveydenhuollonyhteinenhaasteonmukauttaatyötäniin,ettävältetäänsekätyöstäaiheutuvaoireidenpaheneminenettäoireistajohtuvatyöntuloksenheikkeneminen.

Yhdistämällävarhaisiaergonomisiatoimenpiteitäasianmukaiseenlääketieteellisenhoitoonvoidaanpalauttaayläraajavaivoihinliittyväalen-tunuttyötuottavuusparemminkuinpelkällälääketieteellisellähoidolla.Tämäsatunnaistettukontrolloitututkimustukeetähänmennessävä-häistänäyttöäergonomistentoimenpiteidenvaikuttavuudesta.Tuloksetmyöskannustavattyöterveyshenkilöstöäolemaanvarhaisessavaiheessayhteydessäesimieheenjakäymääntyöpaikalla,mikälityöntekijänpää-ongelmaonyläraajavaiva.Verrattunaterveydenhuollontavanomaiseentoimintaantutkimuksentoimenpiteetaloitettiinvarhaisemmassavaihees-sa.Useimmitenliikuntaelinvaivanakuutinvaiheenhoidossasovelletaanvainpuhtaastilääketieteellistämallia.Vastakuntyökyvynlaskupitkittyy,ryhdytääntyöhönliittyviintoimenpiteisiin.Tulostenmukaanergono-misettoimenpiteetovatkuitenkinvähemmänvaikuttavia,josniihinryhdytäänvastayläraajavaivanmuututtuavakavammaksi.

Osittainentyökykyonyleistäliikuntaelinvaivoistakärsivillätyönteki-jöillä.Lisäksiaikaisemmintutkimuksissaonosoitettu,ettämukautetullatyöllävoidaannopeuttaatyöhönpaluutasairauslomanjälkeen.KunvielämuissaPohjoismaissaonkuvattumyönteistäsuhtautumistaosa-aikaiseensairauspoissaoloon,viidesosajulkaisukuvaasatunnaistetunkontrolloiduntutkimuksen,jossaverrataanosa-aikaistajaperinteistäsairauspoissaoloaliikuntaelinsairauksienhoidossa."Osasairausvapaan"aikanatyöntekijääohjataanjatuetaanjatkamaantyössääntoipumistavaarantamatta,kun

YHTEENVETO

sekätyöaikaaettätyötehtäviämuokataanyhteistyössäesimiehenkanssa.Tämäntutkimuksentuloksetovatkäytettävissävuonna2011.

Tämäväitöskirjaosoittaa,ettäliikuntaelinvaivoistaaiheutuvaatyö-kyvynlaskuavoidaanhoitaatehokkaastierityisestityöterveyshuollossa.Vaikkatutkimustenmukaannosto-opetusprimaaripreventionaeiolevaikuttavaa,toinenosajulkaisuosoittaa,ettäsekundaaripreventiossasaadaankannustaviatuloksia.Tämähaastaapelkänlääketieteellisenmallinkäytönjakannustaabiopsykososiaalisenmallinhyödyntämiseenliikuntaelinvaivoistakärsivientyöntekijöidenhoidossa.Päähuomiosiirretäänmahdollisistarakenteellisistasyistäkohtityökyvyttömyyteenliittyviämonimutkaisempiajärjestelmiä,joissapainotetaansekäsosiaa-lisiavuorovaikutussuhteita(esim.perhe,esimies,työkaverit,työnantajajavakuutusyhtiö)ettäyksilönkeskeistäasemaa.

Suurinosaliikuntaelinvaivankanssatyössäjatkamisenesteistäjamahdollistajistaliittyyenemmänpsykososiaalisiintekijöihinsekätyöhönjajohtamiseenkuinfyysiseenvaivaansinänsä.Siksidiagnoosinlisäksiliikuntaelinvaivojenhoidossaontutkittavatyökyvyttömyyttäaiheuttaviajaylläpitäviäpsykososiaalisiajaympäristöönliittyviätekijöitä.Tämälähestymistapaluomahdollisuuksiatukeatyökykyä,välttäätarpeetonsairauspoissaolojaedesauttaatyöntekijöidentyössäjatkamistatuottavastiliikuntaelinvaivastahuolimatta.

ACKNOWLEDgEMENTS

ThisthesisistheresultofmyworkconductedintheFinnishInstituteofOccupationalHealthstartingatthebeginningof2005.TheCentreofExpertise"HealthandWorkAbility"anditsteamof"Work-relatedDiseases"havebeenmybestpossibleschoolandsupportinmyaspira-tiontohigheracademiclevel.IamforevergratefultoDocentHelenaLiira,whoinitiallysuggestedthatIwouldcombineresearchandpracticalwork.IamalsothankfultotheFinnishInstituteofOccupationalHealththatmadeitpossibletotakethiscrucialstepintotheintriguingworldofmusculoskeletalresearch.

Themainprerequisitesforadoctoralstudenttosucceedarethesupervisors.IcouldneverhavemadethisstepwithoutProfessorEiraViikari-Juntura,whoalwayswasavailablewhenIneededher.Iadmirethepositiveenergyshecantransmiteveninsituationswhenherappro-priatecorrectionswerefollowedbyhoursofextrawork.Theeffortwasalwaysworthdoing,becausetheresultwasbothapersonallygratifyinglearningexperienceandamuchbetteroutcome.

Ialsooweverymuchtomyothersupervisors,DocentMariAntti-PoikaandProfessorKajHusman.Theybothhavebeenpersonallyveryimportanttome,notonlyduringthepresentendeavour.Bothcolleagueshavebeenmytutorsfromthebeginningofmycareerinthefieldofoc-cupationalhealth,andthereforewithoutthemIcouldnothavebecometheoccupationalhealthprofessionalthatIam.

WhatIappreciatemostinmycolleaguesandco-authorsistheteamspiritthatwehavesharedduringthepreparationoftheoriginalarticles.IamespeciallygratefultoJosVerbeek,MD,PhD,whotaughtmethefinessesoftheCochranemethodology,aswellastoProfessor

ACKNOWLEDGEMENTS

JaroKarppinenandDocentEsa-PekkaTakala,fortheinspiringdiscus-sionsaroundmusculoskeletalresearch.IwanttothankalsoRahmanShiri,MD,PhD,forbeingalwaysreadytosharehisexpertiseinthestatisticalanalyses.IhavealsobeenveryluckytoworktogetherwithHelenaMiranda,MD,PhD,whoseideasaboutmusculoskeletalpainanditsmanagementhaveinspiredmenotonlytoincludetheminthescientificworks,butalsotoimplementtheminpracticeasanoc-cupationalphysician.

Icouldnothavedoneallthiswithoutmycolleaguesandco-authorsLeenaKaila-Kangas,JohannaKausto,RitvaKetola,MarttiRechardt,RitvaLuukkonen,MerjaJauhiainen,AndreaFurlan,andPaulKuijer.Iwanttoexpressmywarmestthankstothem,aswellastoProfessorHilkkaRiihimäki,whoneverfailedtogiveherpositiveencouragementtomeasajuniorresearcher.Another"seniorcitizen",whomIwishtothank,isDocentKirstiLaunis.Fromher,Ilearntthatsometimestheresultsarelimitedbythechosenmethod,and,therefore,researchisnotsimplylookingforthetruth,butrathertryingtofindthepathtothetruth.

Iamalsogratefultotheofficialreviewers,DocentMarjaMikkels-sonandProfessorHannuVirokannas,fortheirvaluablecommentsforimprovingthemanuscript,aswellastoEwenMacDonaldforrevisingthelanguage.

IthasbeenimportantthatIhavebeenabletosharemyworktimebe-tweenresearchandpracticalworkasanoccupationalphysician.Withoutthepositiveattitudeofmysupervisorsandemployers,firstAriHimmaatM-realCorp.andsubsequentlyTapioVirtaatMehiläinen,Icouldnothavehadtheopportunitytoconductthisacademicwork.Therefore,Iwanttoexpressmygratitudetobothofthem,withoutforgettingallthesupportthatIhavereceivedfrommycolleaguesatMehiläinenOc-cupationalHealthCare.

Sometimestheboundarybetweenworkandleisureisveryvague.Ihaveenjoyedenormouslythescientificdiscussions(andalsothelessscientificones)withJormaMäkitalo,MD,PhD,JuhaLiira,MD,PhD,andProfessorPeterWesterholm.Inaddition,SirkkuVuorma,MD,PhD,andDocentMattiHöyhtyäaremyoldestfriends,whosestepsIhavefollowedfirstinfolkdancingandtheninPhDstudies.Fortunately

ACKNOWLEDGEMENTS

Ihavebeenblessedwithmanydearfriends,whohavesupportedmeinalltheirownways.Thankyouforthat!

Finally,thereasonforeverythingismyfamily,mymotherToini,fatherJaakko,andbrotherArto.IamalsothankfulformyextendedfamilyinVaasafortheirfriendship.Thelastandthewarmestthanksgotomypartner,Sami.YourloveandcareistheairthatIbreathe.Thisworkisdedicatedtoyou.

Helsinki, May 3, 2010

Kari-Pekka Martimo

ABBREvIATIONS

CCT controlledclinicaltrial(nonrandomised)CI confidenceintervalCTS carpaltunnelsyndromeFIOH FinnishInstituteofOccupationalHealthGEE generalizedestimatingequationICF InternationalClassificationofDisability, FunctioningandHealthLBP lowbackpainMSD musculoskeletaldisordersOH(S) occupationalhealth(services)OR oddsratioQQ QuantityandQualitymethodRTW returntoworkRCT randomisedcontrolledtrialUED upperextremitydisordersWHO WorldHealthOrganisation

LIST Of ORIgINAL PUBLICATIONS

I MartimoKP,VerbeekJ,KarppinenJ,FurlanAD,TakalaEP,KuijerPPFM,JauhiainenM,Viikari-JunturaE(2008).Effectoftrainingandliftingequipmentforpreventingbackpaininliftingandhandling:systematicreview.BMJ336(7641):429–31

II MartimoKP,VaronenH,HusmanK,Viikari-JunturaE(2007).Factorsassociatedwithself-assessedworkability.OccupMed(Lond)57(5):380–2.

III MartimoKP,ShiriR,MirandaH,KetolaR,VaronenH,Viikari-JunturaE(2009).Self-reportedproductivitylossamongworkerswithupperextremitydisorders.ScandJWorkEnvironHealth35(4):301–8.

IV MartimoKP,ShiriR,MirandaH,KetolaR,VaronenH,Viikari-JunturaE(2010).Effectivenessofanergonomicinterventiononproductivityofworkerswithupperextremitydisorders:–arandomisedcontrolledtrial.ScandJWorkEnvironHealth36(1):25–33.

V MartimoKP,Kaila-KangasL,KaustoJ,TakalaEP,KetolaR,RiihimakiH,LuukkonenR,KarppinenJ,MirandaH,Viikari-JunturaE(2008).Effectivenessofearlypart-timesickleaveinmusculoskeletaldisorders(Studyprotocol).BMCMusculoskel-etalDisorders9:23doi:10.1186/1471-2474-9-23

CONTENTS

1.INTRODuCTION........................................................ 16

2.REVIEWOfCONCEpTS............................................... 19 2.1.Musculoskeletaldisorders........................................ 19 2.1.1.General...................................................... 19 2.1.2.Lowbackpain............................................. 19 2.1.3.upperextremitydisorders............................ 20 2.1.4.Work–relatedmusculoskeletaldisorders......... 21 2.2.Disability............................................................... 22 2.2.1.Biomedicalmodel........................................ 23 2.2.2.Biopsychosocialmodel................................. 24 2.2.3.Othermodels.............................................. 25 2.3.Disabilityandwork................................................. 26 2.3.1.Sicknessabsenteeism................................. 27 2.3.2.Sicknesspresenteeism (productivitylossatwork)............................ 29 2.3.3.Returntowork............................................ 31 2.3.4.Work–relatedinterventions........................... 31

3.pREVIOuSSTuDIESONMuSCuLOSKELETAL DISORDERS,DISABILITYANDWORK........................... 34 3.1.Work–relatedriskfactorsof musculoskeletaldisorders........................................ 34 3.1.1.Background................................................ 34 3.1.2.Lowbackpain............................................. 38 3.1.3.upperextremitydisorders............................ 41 3.1.4.Work–relatedinterventionsin preventingmusculoskeletaldisorders............. 44 3.2.Work–relatedriskfactorsofsicknessabsence............ 46 3.2.1.General...................................................... 46 3.2.2.Lowbackpain............................................. 47 3.2.3.upperextremitydisorders............................ 51 3.2.4.preventionofsicknessabsence causedbymusculoskeletaldisorders.............. 51 3.3.Work–relateddeterminantsofsicknesspresenteeism... 54 3.3.1.preventionofsicknesspresenteeism associatedwithmusculoskeletaldisorders...... 58 3.4.Determinantsofreturntowork................................ 59 3.4.1.Workerperceptionsandexpectations............. 60 3.4.2.Workenvironmentandworkorganisation....... 61 3.4.3.Roleofthemedicalprovider........................ 64

CONTENTS

4.CONCEpTuALfRAMEWORKOfTHESTuDY................... 67

5.STuDYquESTIONSANDHYpOTHESES......................... 71

6.MATERIALANDMETHODS........................................... 73 6.1.Studypopulations.................................................. 73 6.2.Methods................................................................ 74 6.2.1.Systematicreview(StudyI)......................... 74 6.2.2.Surveys(StudiesII–III)............................... 75 6.2.3.Randomisedcontrolledtrials(StudiesIV–V)..... 77 6.3.Statisticalanalyses................................................. 79 6.3.1.Systematicreview(StudyI)......................... 79 6.3.2.Surveys(StudyII–III)................................. 79 6.3.3.Randomisedcontrolledtrials(StudiesIV–V).... 80

7.RESuLTS.................................................................. 82 7.1.Trainingandliftingdevicesforpreventing backpain(StudyI)................................................ 82 7.2.factorsassociatedwithself–assessed workability(StudyII)............................................. 86 7.3.Self–assessedproductivitylosscaused byupperextremitydisorders(StudyIII)................... 89 7.4.Effectivenessofanergonomicintervention onproductivityloss(StudyIV)................................. 92 7.5.Earlypart–timesickleavein musculoskeletaldisorders(StudyV)......................... 96

8.DISCuSSION............................................................ 97 8.1.Mainfindings......................................................... 97 8.1.1.primarypreventionoflowbackpain andrelateddisability................................... 97 8.1.2.factorsassociatedwithperceiveddisability...... 98 8.1.3.productivitylossasanindicatorofdisability..... 100 8.1.4.Secondarypreventionofdisability................. 101 8.1.5.Comparisonoftwodisability managementmethods................................. 102 8.2.Methodologicalconsiderations.................................. 103 8.2.1.Studydesigns............................................. 103 8.2.2.Studypopulations....................................... 106 8.3.Implicationsforfutureresearch............................... 108 8.4.policyimplicationsandrecommendations.................. 109 8.5.Conclusions........................................................... 111

REfERENCES...............................................................113

1. INTRODUCTION

Oneofthemostcrucialaspectsoflifeishealth.Thisdoesnotmeanonlytheabsenceofsymptoms,illnessandmorbidity(WHO2001).Healthalsomaintainscapacitytoattainone’sowngoalsthroughtarget-orientedactions,i.e.,paidorunpaidwork.TheWorldHealthOrganisation(WHO)hasclassifiedhealthandfunctioningusingthreedifferentdo-mains:bodyfunctionsandstructures,activity(levelofcapacity;whatapersoncandoinastandardenvironment),andparticipation(levelofperformance;whatapersoncandointheirusualenvironment)(WHO2001).IntheInternationalClassificationofFunctioning,DisabilityandHealth(ICF),theterm“functioning”isusedtorefertoallbodyfunc-tions,activitiesandparticipation.Similarly,theterm“disability”referstoallimpairments,activitylimitationsandparticipationrestrictions.

Disabilityisexplainedas“somethingthatrestrictsorlimits”.There-fore,theFinnishtranslation“työkyvyttömyys”(workincapacity)fortheterm“workdisability”canbeconsideredasmisleading.Itreinforcesthefalseunderstandingthatworkdisabilityisadichotomousfactor,i.e.youhaveeitherfullcapacity(“työkykyinen”)oryouareentirelyincapacitated(“työkyvytön”).ThisisnotsupportedbyICF,whichviewsdisabilityandfunctioningasinteractionsbetweenhealthconditions(diseases,disor-dersandinjuries)andcontextualfactors(externalenvironmentalandinternalpersonalfactors)(figure1).Disabilityinvolvesdysfunctioningatoneormoreofthethreedomains(impairments,activitylimitations,andrestrictedparticipation).Restrictionsandbarrierstoperformanceoffunctionalactivitiesorrolesinwhichapersonengagesinthecontextofhisorherlifearealsoconsideredtohaveaninfluenceuponhealthoutcomesandthehealthrecoveryprocess.ICFhasutilizedabiopsycho-socialmodelofdisability(explainedinmoredetailsinchapter2.2.2.).

1INTRODuCTION

Health condition

(disorder or disease)

Personal Factors

EnvironmentalFactors

Body Functions& Structure

ParticipationActivity

FigurE 1. interactions between the components of iCF (WHO 2001)

AccordingtoICF,thedisabilityprocessinitiatedbyahealthconditionisinfluencedbybothenvironmentalandpersonalfactors.Environmentalfactorscanincludesocialattitudes,architecturalcharacteristics,legalandsocialstructure,aswellasclimateandterrain.Thepersonalfactorsaregender,age,copingstyles,socialbackground,education,profession,pastandcurrentexperienceofhealthconditions,overallbehaviourpattern,personality,andotherfactorsthatinfluencetheperceptionofdisabilitybytheindividual.

Disabilitydoesnotmeantotallossoffunctioninginanyofthethreedomains.Despiteofamedicalcondition(forexample,seropositivityforHumanImmunodeficiencyvirus),apersonmaybefullyfunctionalinboththeactivityandparticipationdomains.Inaddition,andparticularlywithparticipation,restrictions(problemsanindividualmayexperienceininvolvementinlifesituations)canbeconsideredasproblemscreatedbyanunaccommodatingphysicalenvironmentasaresultofattitudesandotherfeaturesofthesocialenvironment.

Latelythepositiveeffectsofworkhavegainedincreasingattention(Waddelletal.2006).Workoftenplaysaroleinpromotingbothphysicalandmentalhealth:physicalactivity(forexample,work)isusuallyas-sociatedwithimprovementinphysicalcapacity,whilegoalachievement,

1INTRODuCTION

socialinteractions,andself-realisationinworkaresourcesofsatisfactionandenhancedself-esteem(WHO1985).Therefore,insteadofleavingworklife,peoplewithdisabilitiesshouldbeencouragedtocontinueinemployment,providedthatworkisadaptedtohumangoals,capacitiesandlimitations,andoccupationalhazardsareundercontrol.

2. REvIEW Of CONCEPTS

2.1. Musculoskeletal disorders

2.1.1. general

Themusculoskeletalsystemcomprisesofbonesandjointswiththeiradjacentstructures,aswellasmuscles,tendonsandligaments.Thisstudyisconcernedwithdisabilitycausedbyorassociatedwithmusculoskeletaldisorders(MSD).InFinland,MSDarethemostimportantcausesoftemporarydisability(lastinglessthanoneyear)(Kansaneläkelaitos2008).MSDalongwithrespiratoryinfectionsarethemostcommonreasonsfortheuseofprimaryhealthservices.Inaddition,MSDandmentaldisordersaccountforthemajorityofpermanentdisabilitypensionsinFinland.

”Disorder”inthisstudyreferstoanycomplaint,symptomordiseaseofthemusculoskeletalsystem.Complaintisanexplicithealthproblemexperiencedbyanindividual.Disease,ontheotherhand,isaclinicallyverifiableentitythatisdetectedinaclinicalexamination.Standardizedclinicalexaminationprotocolsformanycommonmusculoskeletalsymp-tomsareavailableinordertoachieveamorereliableandcomparablediagnosis(Sluiteretal.2001).

Lowbackpain(LBP)andupperextremitydisorders(UED)arescru-tinizedinthisthesis,sinceLBPisthemostcommonmusculoskeletalcauseofdisabilityandthereisstrongevidenceofwork-relatednessforbothUEDandLBP(Punnettetal.2004).

2.1.2. Low back pain

LBPisdefinedaspaininthelumbarand/orglutealregionwithorwith-outradiationtothelowerextremities.Itisoftencategorisedaccording

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tothedurationofthesymptoms:acutepainwithlessthan4–6weeks,sub-acutebetween4–6and8–12weeksandchronicaspainofmorethan8–12weeksofduration.However,"long-lasting"or"prolonged"shouldbepreferredinsteadof"chronic"inordertoavoidunnecessarylabellingoftheemployeewithLBPbeing"chronically"ill.

VariousdiagnosesandpathologicalconditionsmaymanifestwithLBP.However,theoverwhelmingmajorityofbackpaincasesremainnonspecific.About85 %ofpatientswithisolatedLBPinprimarycarecannotbegivenanyprecisepathoanatomicaldiagnosis,andtheassocia-tionbetweensymptomsandimagingresultsisweak(Deyoetal.2001).Inabout3 %ofcasesthereasonsforLBPareneoplasia,infection,visceralpainorsystemicdisease.

Despitethefactthatbackpainisnotalifethreateningcondition,itconstitutesamajorpublichealthproblemintheWesternindustrialisedsocieties.LBPaffectsalargenumberofpeopleeachyearandisthecauseofseverediscomfortandfinanciallosses(Maniadakisetal.2000).Oneimportantfeatureofworkerswithnonspecificbackpainisthatasmallproportionofcases(<10 %)accountsformostofthecosts(>70 %)(Dionneetal.2005).Duetoitshighprevalence,backpainisaleadingreasonforphysicianvisits,hospitalisationsandotherhealthandsocialcareserviceutilisation.

TheseverityandtypeofbackpainchangewithageeventhoughLBPiscommonalreadyinadolescenceandearlyadulthood(Mikkels-sonetal.1997).Itbecomesmoreseverearoundtheageof40,showingdifferentdevelopmentofnonspecificandradiatingLBP.Accordingtoalongitudinalstudyofarepresentativepopulation,moderateaswellasmajornonspecificLBPdeclineswithage,whereastheincidenceofmajorradiatingLBPincreaseswithage(Shirietal.2010).

2.1.3. Upper extremity disorders

SofttissueMSDoftheupperlimbandshoulderregioncompriseaheterogeneousgroupofconditionsrangingfromspecificupperlimbconditions,likedeQuervain'stenosynovitis,epicondylitis,rotatorcufftendinitis,andcarpaltunnelsyndrome(CTS),tonon-specificregionalpainsyndromes.Labelssuchas"repetitivestraininjury","cumulativetraumadisorder"and"work-relatedupperlimbpain"havebeenoften

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used(Walker-Boneetal.2005),butshouldbeappliedwithcaution,becausetheyalreadyincludeanassumptionoftheaetiologyofthedisorder.Inaddition,"non-specificforearmpain"hasbeenadoptedasthediagnosticlabelforpatientspresentingwithforearmpainwithoutphysicalsigns(Walker-Boneetal.2005;vanTulderM2007).SomeagreedsystemsofclassificationofUEDhavebeendevelopedtoimprovethequalityofepidemiologicalresearch(Harringtonetal.1998;Sluiteretal.2001;Helliwelletal.2003).

UEDarecommonintheworkforce.Inapopulation-basedstudyofFinnishadults,theprevalenceofaclinicallydiagnosedUEDwashighestforrotatorcufftendinitisandCTS(both3.8 %),followedbylateralepicondylitis(1.1 %),bicipitaltendinitis(0.5 %),andmedialepicondylitis(0.3 %)(Shirietal.2007).InFinland,1070work-relatedMSDwerereportedtotheregisterofwork-relateddiseasesin2007representing17 %ofallconfirmedorsuspectedoccupationaldiseases(Karjalainenetal.2009).Themostcommondiagnoseswererelatedtotheupperextremities;epicondylitis(halfofallcases),tenosynovitis,andCTS.

2.1.4. Work-related musculoskeletal disorders

MSDaremultifactorialintheirorigin,andwhenaffectingworkers,theycanbework-relatedinanumberofways:MSDmaybepartiallycausedbyadverseworkconditions;theymaybeaggravated,acceleratedorex-acerbatedbyworkplaceexposures;andtheymayimpairworkcapacity.Itisalsoimportanttorememberthatpersonalcharacteristics(includinggeneticfactors),aswellasenvironmentalandsocioculturalfactorsusu-allyplayaroleasriskfactorsforwork-relateddiseases(WHO1985).Inaddition,duetothehighprevalenceandrecurrenceratesofMSD(especiallyLBP),cautionhasbeenadvisedinrelatingthesedisordersexclusivelytotheworkplace(Werneretal.2009).

AccordingtotheFinnishWorkandHealthSurveyconductedin2006(Kauppinenetal.2007),28 %ofthe2229interviewedemployeesreportedlong-termorrecurrentphysicalorpsychologicalsymptomsthathadbeencausedorworsenedbyworkduringthelastmonth.Dependingonthelocationofthesymptoms,63–91 %ofthosewithmusculoskeletalsymptomsconsideredthemtoberelatedtowork.

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Asystematicreviewshowedthatpotentiallywork-relateddiseasesarecommoningeneralpractice(Weeversetal.2005).Highprevalenceratesofpotentiallywork-relateddiseaseswerefoundforLBP,neckpainandshoulderpain.AccordingtotheresultsofaNorwegiansurvey,themajorityofcaseswithMSDwereassessedasbeingwork-relatedbyboththestudyparticipantsandtheexperts:80 %versus65 %forpainintheneckorshoulderregionand78 %versus72 %forarmpain(Mehlumetal.2009).

IthasbeenarguedintheNetherlandsthattoolittleattentionispaidtothepossiblework-relatednessofhealthcomplaints,andthatthiscanbeamajorcauseofsicknessabsenceanddisability(Buijsetal.2005).Ifthephysicianscannotrelatethepatients’healthcomplaintstoworkfactors,theyareatriskofmakinganinadequateassessmentortheymaymisseffectivetherapeuticmeasures.Thiscanleadtounnecessarylongsicknessabsenceperiods,and,evenpossibly,permanentdisability.

2.2. Disability

Disabilityisstudiedinthisthesisfromtheperspectiveofproblemsintheparticipationatwork,“occupational/workdisability”.Theterm“dis-ability”,however,willbeusedforsimplicity.Thespecialfocusisontherelationofdisabilityandwork,howworkaffectstheemployee’shealthandfunctioningatwork,andhowamedicalconditioncanimpactontheemployee’sabilitytocontinueworking,payingspecialattentiontocontextual,personalandenvironmentalfactors.

Occupationalorworkdisabilityisusuallydefinedastimeoffwork,reducedproductivity,orworkingwithfunctionallimitationsasaresult(outcome)ofeithertraumaticornon-traumaticclinicalconditions(Schultzetal.2007b).

Theredoesnotexistonesinglemodelofdiagnosisandrehabilitationofpain-relatedoccupationaldisability,butmany,oftencompetingandconflicting,modelscurrentlyexist.Thecoreissueistoselecttherightmodelfortherightservicerecipientattherighttime.

Inthecontextofworkdisability,observationalstudieshavedem-onstratedthatadversedisabilityoutcomesareinextricablylinkedwithcommunicationfailuresbetweentheemployeeandthecareprovider,and

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descriptionofsuccessfulprogrammesoftenciteeffectiveorimprovedcommunicationasanimportantelementintheirsuccess(Pranskyetal.2004).Therefore,effectivecommunicationcanbeseenasaprerequisiteforsuccess,regardlessofthespecificapproachtodisabilitymanagementandprevention.

2.2.1. Biomedical model

Thebiomedical model (alsocalledasthe"diseaseparadigm")isthepre-dominantframeworkusedbyalargegroupofhealthcareprofessionalsasmosthealthcaresystemsarestillbasedonapurelymedicalmodelofillnessandinjury.Inthismodel,illnessisconsideredtobeaconse-quenceoftheill-functioningofthehumanorganismasa"biologicalmachine",andthediseaseisdescribedasalinearsequencefromcausefactortopathology,tosymptomsormanifestations(Schultzetal.2000).Thesecondtenetofthebiomechanicalmodelholdsthatsymptomsanddisabilityaredirectlyrelatedto,andproportionateto,theseverityofbiologicalpathology.Thereforeaccordingtothistheory,eliminationofpathologicalcauseswillinevitablyresultincureorimprovement.Interventionstudiesemployingthisapproachhavefocusedontheroleofspecificmedicaltreatmentsorclinicalapproachesintendedtopreventprolongeddisability(Pranskyetal.2004).

Communicationinthebiomedicalmodelisoftenunidirectional(physiciantoemployerandpatient),notinteractive,asphysiciansissuedefinitivepronouncementsaboutcause,diagnosisandfunction.Inad-dition,patientsusuallyadheretothebiomedicalmodeldiffusedinthemedia,meaningthattheirexpectationsmaybeinconsistentwithothermodelsthatwouldbestsuittheircondition(Loiseletal.2005).

Consideringthecomplexnatureofpain,solelyfocussingonbiomedi-calpathologyresultsinalackofconsiderationofthemultidimensionalnatureofthephenomenon,thevarietyofreactionstopain,andthechangingnatureofinjuryandpainovertime(Schultzetal.2000).Thisexclusiveattentiononobjectivelyidentifiedpathologynegatestheim-portanceofpatient-centredmeasuresofpain,symptomsanddisability."Objective"measuresofpathology,however,havebeenshowntopredictdisabilityratherpoorly,andapathophysiologicalexplanationcannotbeofferedinallMSD.Thesearchforwhatisusuallyanelusive"medi-

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calexplanation"ofpaininmostcasesprolongsthediagnosticprocessneedlessly.Asaresult,thismodel,whenappliedtononspecificpainconditions,canincreasechronicityandhumansufferingandimposeafinancialburdenonhealthcareandcompensationsystems.

Forthosekindsofinjuriesandillnesseswherehealingprocessesarehighlypredictableandtheriskofre-injuryislow(minorlacerations,trauma,orfractures),thebiomedicalmodelperformswell(Pranskyetal.2004).Thismodelisrelevantwithrespecttomedicaldecisionmaking,particularlywithregardtouncomplicated,physicalinjuriesorpainorbothinitsacutestages,aswellasintheidentificationofmedical"redflags",i.e.,rulingoutofseriousmedicalconditions,suchastumours,infectionsandfractures(Schultzetal.2000).

2.2.2. Biopsychosocial model

Fromanepidemiologicalperspective,itappearsthatnon-clinicalfac-torsaremorelikelythanclinicalatexplaininglong-termdisabilitycases(Loisel2009).Therefore,itisnotaquestionofimprovingclinicalcareinordertoachievebettertreatmentresults.Thebiopsychosocial approachhasbeenmodifiedinmanydifferentformsandisgenerallythemostcommonlyconsideredandconsensualframeworkforunderstandingthemultidimensionalaspectsofmanyhealthproblems(Schultzetal.2007b).Thebiopsychosocialmodelrecognizesthattherelationshipsbetweenpain,physicalandpsychologicalimpairment,functionalandsocialdis-abilityarefarfromsimple;painandresponsetoMSDarecomplexandinteractingphenomena(Schultzetal.2000).Thisapproachdemandsaconceptualshiftfromthelinearwayofthinkingofthebiomedicalmodeltoanopensystemperspective.

Researchonthistopichasyieldedsubstantialevidenceonthede-terminantsofworkdisability.Thesedeterminantscanbelinkedtotheworker(personal),workplacedesignororganisation(workplace-related),healthcaresystem,compensationsystemorthenatureofthelocalcultureandsociety(Loisel2009).Theparadigmshiftfromabiomedicaltoabiopsychosocialmodelofdisabilitytransfersresponsibilityforoutcomesfromthehealthcareprovider-patientrelationshiptoamulti-playerdeci-sion-makingsystemwhichisinfluencedbycomplexprofessional,legal,administrative,andcultural(societal)interactions(Loiseletal.2005).

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Basedontheprinciplesofthebiopsychosocialmodel,inthecase management model,theclientisanactiveparticipantintherehabilita-tionprocess,andtherehabilitationteamonlyfacilitatesthisprocess(Schultzetal.2000).Thetherapeuticfocusistherestorationoffullfunction,notsymptomremovalor"cure",andtherestorationofemploymentstatuswithminimaldelayisoneofthemajorgoalsoftreatment(Schultzetal.2000).Earlyinterventiondesignedtorestorephysicalorrolefunction,increaseactivitylevels,andtoachieveworkmaintenanceorworkre-entryisconsideredtoexpeditethereturntowork(RTW)process.

Casemanagementisessentialwhentheclient'streatmenthastobecoordinated,plannedandmonitored.Thisemphasisstemsfromthebeliefthatthelongerthepainanddisabilitypersist,themoredifficulttheywillbetotreat.Thereforeidentificationofthosefactorsthatpredictpoorprognosisforcontinueddisabilityandidentificationofthoseworkersathighriskforcontinuedworkdisabilityareimportantcomponentsofearlyintervention(Schultzetal.2000).

2.2.3. Other models

Themajortenetoftheinsurance model (alsocalledasforensic,compensa-tionorthe"perverseincentives"model)isthatclaimantswhoanticipatefinancialbenefitsthroughcompensation,pendinglitigation,specialservicesorconsiderations,suchasjobtransferorreducedworkload,arelikelytobedishonestabouttheirsymptoms(Schultzetal.2000).Thereisastrongmoralisticelementinthismodelwhereitisnecessarytoclearlydifferentiatebetween"honest"and"dishonest"claimants.Theinsurancemodelnurturesaclimatewhereintheclaimantmustvigorouslyproveandproveagainhisorherdisabilitywithobjective,verifiable,repeatablemedicalevidenceofimpairment.

Anothersubgroupofthemedicalmodelisthepsychiatric modelwiththebasictenetthatpainiseitherorganicorpsychologicalinitsorigin(Schultzetal.2000).Painthatcannotbeattributedtophysicalcausesmustbepsychological,andpatientswithundiagnosed,intractablepainareapsychologicallyhomogenousgroup.Thediagnosisofamentaldisordercanentitleapatienttoreceiveservicesandbenefitsthatmightnototherwisehavebeenavailable.However,thepsychiatricframework

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forpainhasproventobeineffectiveforrehabilitationandcanbediag-nosticallymisguiding(Schultzetal.2000).

Thephysical rehabilitation modelcanalsoberelatedtothebiomedi-calmodel,becauseitsfocusindisabilitymanagementandpreventionstrategiesisonimprovedphysicalconditioning(Pranskyetal.2004).ThismodelassumesthatRTWoutcomescanbeimprovedbymuscle-strengtheningexercisesinaclinicalorworkplacesettingthatsimulatesactualworkingconditions.Onelimitationofthismodel,however,isthatworkenvironmentsmaybedifficulttosimulateespeciallywhen,inreallife,psychosocialandorganisationalfactorsaresignificantcontributorstodisability(Pranskyetal.2004).Inaddition,thetraditionalrehabili-tationmodelseemsone-sided:disabilitymanagementsimplyfocusesonimprovingworkercapabilitiestomatchjobdemandswithoutanythoughtofredesigningormodifyingjobstomatchworkerlimitations.

Ajob-match modelfordisabilitymanagementusesananalyticalstrat-egytoassessthematchbetweenanindividualwithfunctionallimitationsandaparticularjob(Pranskyetal.2004).Thismodelmayproveusefulforworkplaceaccommodationeffortswherebiomechanicalrequirementsareuniform,andergonomicrisksarerelativelyeasytodefine(forexample,assembly-lineworkers,keyboardoperators).Thisapproachassumesthattheworkercapabilitiesareeasilyquantifiedinrelationtojobtasks,allphysicaldemandsarecapturedbyphysicalmeasures,andthatdemandsarestaticovertime.Theseassumptionsarerarelyrealisticinthemodernworkenvironment.Inaddition,thejob-matchmodeldoesnotaddresspsychosocialfactorsorhowanemployee-jobmismatchistranslatedintotheappropriateaccommodation(Pranskyetal.2004).

2.3. Disability and work

Theprocessoffallingill,beingabsentfromwork,recoveringandthenreturningtoworkhasbeenrepresentedschematically(EuropeanFoun-dationfortheImprovementofLivingandWorkingConditions1997).Theonsetofdisabilityisviewedintermsofanimbalancebetweenthepersonandtheenvironment(figure2).Dependingontheopportunityandneedforabsenteeism("absenteeismbarrier"),healthproblemsmayresultinabsenteeismandincapacitytowork.RTWdependsonthe

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courseoftheillnessandthe"reintegrationbarrier",whichreferstothetotalityoffactorswhichaffectthecourseoftheillnessandRTW.Thiswholeprocessisinfluencedbyindividualfactors,companyandworkplacefactors,aswellasfactorspertainingtothesurroundingsociety.

Thedefinitionsofdurationofoccupationaldisabilityrangefromcumulative,asinthedurationofalldayslostfromworkstartingwiththedateoftheonsetofsymptoms,throughcategorical,forexampleRTWstatus(yes/no),tocontinuous,suchastimetoRTW.Inaddition,predictorsofdisabilityandpredictorsofRTWoftendiffer(Schultzetal.2007b).

2.3.1. Sickness absenteeism

Whenamedicalconditionissevereenoughitimpedesjobperformancetothedegreethattheemployeeisnotabletocontinueworkingbecauseofexcessivelylowfunctionalcapacityinrelationtotheexplicitorimplied

CapacityAbsenteeism

barrierreintegration

barrier

BalanceHealth

problemsreturn to

workAbsence of

Workload

individual factors

company/workplace factors

societal factors

FigurE 2. The process of becoming ill, being absent from work, recovering and return to work (European Foundation for the improvement of Living and Working Conditions 1997)

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jobdemands.Otherreasonsforabsencefromworkarethattheexposureatworkmakesthesymptomsworseormedicalcareandrehabilitationrequiresthattheemployeecannotbepresentatwork.Whentheemployeeabstainsfromworkingbecauseofadisablingmedicalcondition,thisiscalledsick-nessabsence(orsickleave),andthephenomenonsicknessabsenteeism.

Sicknessabsenceismeasuredbyaskingtheemployeehowmuchtimeheorshehasmissedfromworkbecauseofillhealth.Theotherandmorereliablealternativeistorelyonstatisticscollectedbyemployersonhowmuchtimetheemployeeshavebeenabsentfromworkbecauseofillness.Ifthestatisticsarenotavailable,self-reporteddatahavebeenfoundtobereliableandvalid,whentherecallperiodsareshort(i.e.,1–2weeks)(Mattkeetal.2007).Evenwhentherecallperiodisuptooneyear,theagreementbetweenthenumberofself-reportedandthenumberofrecordedsicknessabsencedaysisrelativelygood(Ferrieetal.2005;Vossetal.2008).Iftherecallperiodsarelonger,theresultsneedtobeviewedwithcaution.

Thefollowingbasicmeasureshavebeensuggestedforassessingsickleaves:frequency(totalnumberofsickleaveperiods/allemployees),length(sick-leavedays/sick-listedpersons), incidence(newspells/(numberofemployeesxnumberofdaysminusallsick-leavedays)),cumulativeincidence(numberofemployeeswithsickleaveperiods/allemployees),andduration(sick-leavedays/sickleaveperiods)(Hensingetal.1998).Itisalsobeneficialtoseparateshortandlongtermabsenceperiods,asonlymedicallycertified(longterm)absenceshavebeenshowntoserveasaglobalmeasureofhealth,butnotshortselfcertifiedabsences(Kivimäkietal.2003).

InalargeprospectivecohortstudywithFinnishmunicipalemploy-ees,themeasuresofsicknessabsence(longtermabsenceperiodsandsickdays)wereshowntobestrongpredictorsofallcausemortalityandmortalityduetocardiovasculardisease,cancer,alcoholrelatedcauses,andsuicide(Vahteraetal.2004).Medicallycertifiedabsencesduetocirculatorydiseases,surgicaloperations,andpsychiatricdiagnoses(butnotMSD)wereassociatedwithincreasedmortalityalsoamongBritishcivilservants(Headetal.2008).

InasurveyamongFinnishlabourunionmembers(Böckermanetal.2009),absenteeismcausedbyanyreasonwaspositivelyassociatedwithparticipationinshiftorperiodwork,whereasregularovertime

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wasassociatedwithlesssicknessabsenteeism.Thepossibilitytostayathomeuptothreedayswithoutanycertificatewasnotassociatedwithanyincreaseinsicknessabsenteeism.

2.3.2. Sickness presenteeism (productivity loss at work)

Healthdisordersdonotcausemerelyabsencefromwork,butalsode-creasedon-the-jobperformancewhileatwork,whichiscalled"sicknesspresenteeism".Theshorterterm"presenteeism"willbeusedinthistexttodescribeproductivitylossatworkduetoMSD,evenifpresenteeismcanalsobecausedbyfactorsotherthanhealth(forexample,organisa-tionaldysfunctionordistractingdomesticproblems).Asystematicreviewcovering37studiesconcludedthatseveralhealthconditions,suchasasthmaandallergies,aswellashealthriskfactors,likeobesityandphysi-calinactivity,areassociatedwithpresenteeism(Schultzetal.2007a).

However,themeasurementofproductivityanditslossatworkisdifficult.Insomeprofessions,liketelephonecustomeroperators,pro-ductivitycanbemeasuredobjectivelyusingkeystrokesorthenumberofreceivedtelephonecallsastheindicator.Ontheotherhand,particu-larlyininformationandservice-typeoccupationstheoutputatworkisdifficulttoquantify.Therefore,amultitudeofworkplaceproductivitymeasurementinstrumentshavebeencreatedandevaluated(Mattkeetal.2007).Nonetheless,themostcommonapproachofmeasuringpresenteeismisassessmentofperceivedimpairment,accomplishedbyaskingemployeeshowmuchtheirillnesseshindertheminperformingcommonmental,physical,andinterpersonalactivitiesandinmeetingjobdemands(Mattkeetal.2007).

Theconsequencesofpresenteeismhavebeenstudiedfromtheor-ganisationalaswellasfromtheindividualperspective.IntheNorthAmericanliterature,thefocushasbeenonhealthandproductivityasabusinessstrategy(Goetzeletal.2007).Thisapproachisbasedonthefindingthathealth-relatedproductivitycostsaresignificantlygreaterthanmedicalorpharmacycostsalone(onaverage2.3to1),andthatchronicconditionssuchasdepression/anxiety,obesity,arthritis,andback/neckpainareespeciallyimportantcausesofproductivityloss(Loeppkeetal.2009).Sinceemployersaretheultimatepurchasersofhealthcareservices

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forthemajorityofemployeesintheUnitedStates,thesefindingshavepromptedemployerstodevelopandevaluatethecost-effectivenessofhealthandproductivityinterventions.

IntheEuropeanliterature,moreattentionhasbeenpaidtothecon-sequencesofpresenteeismattheindividuallevel,basedonthefindingsthat63–83 %ofemployeesreportedhavingworkeddespiteillnessonatleastoneoccasionduringthepreviousyear(Bergströmetal.2009).Sicknesspresenteeismseemstobemoresensitivetoworktimearrange-mentsthansicknessabsenteeism,eventhoughthedirectionofcausalitycouldnotbeexploredinacross-sectionalstudy(Böckermanetal.2009).

AccordingtoaSwedishreviewonsicknessabsenteeismandpresentee-ism,nostudieswerefoundontheconsequencesofsicknesspresenteeismfortheindividual(SBU2004).Productivityloss,however,iscommonbothbeforeandafterperiodsofsicknessabsence(Brouweretal.2002).Perhapsthereforepresenteeismhasbeenassociatedwithmoresicknessabsenteeisminseveralstudies.ASwedishprospectivestudy(Bergströmetal.2009)concludedthatworkingdespitethefactthattheemployeefeltthatsickleaveshouldhavebeentakenwasastatisticallysignificantrisk(relativerisk1.4–1.5)forfuturesickleaveofmorethan30days.Inthesamestudy,however,takingsickleaveduringthebaselineyearwasanevengreaterriskfactorforfuturesickleave;relativeriskwas1.5–5.4dependingonthenumberofdaysonsickleave.Therefore,sickleavemaynotbeanalternativetosicknesspresenteeism,iffuturesicknessabsenteeismistobeprevented.

Alargeprospectivecohortstudywitha3-yearfollow-upamongBrit-ishcivilservantsshowedthattheincidenceofseriouscoronaryeventswastwiceashighamongemployeeswhodidnottakesickleavedespitepoorperceivedhealthatbaseline,comparedtothose"unhealthy"employeeswithmoderatelevelsofsicknessabsenteeism(Kivimäkietal.2005).Thisphenomenonhasbeenlaterstudiedthoughithasnotbeenpossibletodetectanyevidencethatworkingwhileillwouldactasashort-termtriggerforcoronaryevents(Westerlundetal.2009).Accordingtotheauthors,twopotentialexplanationsremain.Workingwhileillmightcontributetoacumulativepsychologicalburdenwithpathophysiologicconsequences,orthatsicknesspresenteeism,insteadofbeingacausalagent,isonlyamarkerofalifestyleinwhichsymptomsareignoredandmedicalcareisnotsought(Westerlundetal.2009).

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2.3.3. Return to work

RTWcanbeconceptualisedasthe"process"ofreturninganinjuredworkertowork(forexample,graduatedRTWorjobaccommodation)orasthemeasurablefinalcommonoutcomeofdisability:thestatusofworkingornotworking(Schultzetal.2007b).RTWasanoutcomemayinvolvereturntothepre-injuryemployerorthepre-injuryjob,withorwithoutaccommodation(Schultzetal.2007b).Consequently,theperspectiveson,andmeasurementsof,RTWinresearchandpracticevarywidelyanddependonthestakeholdersinvolvedintheevaluationprocess.

Insteadoffocusingonthecharacteristicsofworkdisability,themainemphasisshouldbeontheactionsassociatedwithsuccessfulworkre-sumption.Therefore,RTWhasbeenpresentedasanevolvingprocesscomprisingoffourkeyphases:offwork,workre-entry,retention,andadvancement(Youngetal.2005).TheendofeachRTWphasemarkstheachievementofimportantRTWoutcomes:theabilitytoattemptworkre-entry,theabilitytoperformsatisfactorily,theabilitytomaintainemployment,andtheabilitytoadvanceinone'scareer.

SicknessabsenteeismandRTWaredependentoneachother;disabilitycanbemeasuredbothasprolongedsickleaveanddelayedRTW.Therefore,itissometimesdifficulttodifferentiatewhetherthestudyhasbeenconcernedwithsicknessabsenteeismorRTW.Inthisthesis,thestudieshavebeencategorisedaccordingtothemainout-comemeasure;thelengthofsicknessabsenceorsuccessfulRTW.Theformerstudiesarelabelledasstudiesonsicknessabsenteeism,andthelatterasstudiesonRTW.

2.3.4. Work-related interventions

Thedefinitionof"work-relatedintervention"usedinthisthesishasbeenadoptedfromarecentCochranereviewoninterventionsfocusingonchangesintheworkplaceorequipment,workdesignororganisation(includingworkingrelationships),workingconditionsorworkingenvi-ronment,andoccupational(case)managementwithactivestakeholderinvolvementof(atleast)theworkerandtheemployer(vanOostrometal.2009).

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AccordingtoColeetal(Coleetal.2003),workplaceinterventionstoreducemechanicalexposurescanbeexecutedateightdifferentlevels:

1. Businesssector(forexample,ergonomicbestpractices)2. Organisationorcompany(forexample,ergonomicpolicy,audit)3. Plantorworkplace(forexample,ergonomicchangeteams)4. Lineordepartment(forexample,reorganisedflow)5. Workgroup(forexample,safetyclimatetraining,jobrotation)6. Job(forexample,jobenlargement,regularbreaks)7. Worker(forexample,ergonomictraining,workstationadjustment)8. Taskortool(forexample,sharpeningimprovements,newtrimming

tools,liftassists)

HealthcareactivitiesaimedatpreventingMSDandrelateddisabil-itycanbedividedintothreetheoreticalcategories(NationalResearchCouncilandInstituteofMedicine2001).Primary preventionoccurswhentheinterventionisundertakenbeforeworkersatriskhaveacquiredaconditionofconcern,forexample,educationalprogramstoreducethenumberofnewcases(incidence)ofLBP.Secondary preventionoccurswhentheinterventionisundertakenafterindividualshaveexperiencedtheconditionofconcern,forexample,introductionofjobredesignforworkerswithsymptomsofCTS.TertiarypreventionstrategiesaredesignedforindividualswithchronicallydisablingMSD;thegoalistoachievemaximalfunctionalcapacitywithinthelimitationsofthatindividual'simpairments.

Similarthree-levelapproachhasbeenintroducedtodisabilityman-agement,inwhichthemainfocusisnotontheclinicalsymptomsbutonrelateddisability(Loisel2009):(A)Primarypreventionconsistsoflookingatthework-relatedfactorsinordertopreventnotonlysymp-tomsordisordersbutalsorelateddisability;(B)Secondarypreventionincludespayingattentiontotheworkerswithsymptomsordisorders,andinstigating actionstohelptheseworkersrecoverorimprovetheirworkingsituationinsteadofsickleaveorlowerproductivityatworkduetohealthproblems;(C)Tertiarydisabilitypreventionisconceptualisedbyinterventionsthatpreventunnecessaryprolongationofsicknessab-senteeismandsupportsafeRTW.

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Organisationalexperimentstoimproveoccupationalhealthareusu-allyregardedaslaboratory-basedexperimentsinthenaturalsciences,evenifinorganisationstheconditionsaretotallydifferent.Theprerequisitesoftemporalpriority,controloverimportantvariables,andrandomal-locationofsubjectstotreatmentorcontrolgroupsareusuallyhardtofulfil(Griffiths1999).Intheircomprehensivereviewoninterventionstoreducework-relatedMSD(Silversteinetal.2004),SilversteinandClarkereportedthatitwasextremelydifficulttorandomiseengineeringcontrolsinmultipleworkplaces,andmucheasiertorandomisepersonalbehaviour(exercise,education,medicaltreatment).Manystudieshavebeenconfrontedwithchangesinworkplacesthatareunplannedbytheresearchersandbeyondtheircontrol.Stableworkplaceswithlargenum-bersofworkersperformingthesameworkarelargelyathingofthepast.

Quiteevidentlytheavailableresearchondisabilityismethodologi-callydifferentfromtheepidemiologicalstudiesonoccupationalrisksofMSD.Thelatterarescientificallymorerigorousinconfirmingcause-and-effectrelationshipsandallowingprediction.Studiesondisability,however,includelesstangiblefactors,suchasthedesign,management,andorganisationofwork,whereitisunrealistictoexpectthattherewouldbeanaturalscientificparadigmtoexplainthesehighlycomplex,constantlychangingsystemsandtopredictthespecificeffectsonindi-vidualbehaviourandhealth(Griffiths1999).Thishasledtothefactthatstudiesondisabilityhaveappliednotonlyquantitativebutalsomorequalitativemethodologies.

3. PREvIOUS STUDIES ON MUSCULOSKELETAL DISORDERS, DISABILITY AND WORK

Thefollowingreviewisdescriptiveandprimarilybasedontheresultsofrecentlypublishedreviewsgatheredfromthemainoccupationalhealth(OH)journals.Inaddition,selectedindividualstudieshavebeenincludediftheyhavebeenpublishedrecently,ortheyareconsideredespeciallyinterestinginthecontextofthisthesis.

3.1. Work-related risk factors of musculoskeletal disorders

3.1.1. Background

Athoroughcomprehensionofthecausalassociationbetweenoccupa-tionalexposuresandMSDisnecessaryifonewishestoestablishoc-cupationalguidelinesfortheprimarypreventionofMSD,toidentifypotentialworkmodificationsforthesecondaryprevention,andtopro-videguidanceforthestakeholdersinvolvedintheprocessoflong-termdisability.This,however,isnotasimpletasktoaccomplish.

Epidemiologicalresearchreliesupontheuseofdiagnosticcriteriacapableofseparatingstatesofdiseasewithdifferentcauses,prognosis,orresponsetotreatment(Walker-Boneetal.2005).Inmoststudiesonbackpain,theoperationalisationbasedonthesymptomreportingdoesnotallowexaminationoftheriskfactorsfordifferentgroupsofbackpain,classifiedbasedoncharacteristicssuchastheduration,frequency,

3pREVIOuSSTuDIESONMuSCuLOSKELETALDISORDERS,DISABILITYANDWORK

intensity,andlocalisationofthepain(Hoogendoornetal.1999).LatelyaDelphiconsensusprocesswasusedinordertoreachasubstantialagree-mentonLBPoutcomesthatwouldbecombinableintoameta-analysis(Griffithetal.2007).

ManystudiesinthefieldofMSDarecross-sectionalsurveysrelyingonself-reportedsymptomsastheindicatorsofMSD.Thisapproachhastwomajoraspectswhichneedtobetakenintoconsideration.First,theweaknessincross-sectionalstudiesisthedifficultytodistinguishcauseandeffect,aswellasriskfactorsthatprolong(andnotcause)thedisorder.Second,thedeterminantsofspecificMSDseemtodifferfromthoseofsubjectivecomplaintswithoutclinicalfindings(Mirandaetal.2005).Suchcomplaintsmaybeindicatorsofadversepsychologicalandpsychosocialfactorsratherthanthepresenceofanunderlyingpathologiccondition.

Informationonexposuresinthestudiesisoftenself-reportedandnotsupportedbyobjectiveobservationsormeasurements.Non-random(biased)associationsmayariseifsubjectswithorwithoutsymptomshaveadifferentrecallofexposures,orifthosewithexposuresthatworrythempaymoreattentiontotheirsymptoms(Viikari-Junturaetal.1996;Walker-Boneetal.2005).Inaddition,theassessmentmethodsforpsy-chosocialriskfactorsvary,becausethereisapoorconsensusabouthowthesefactorsshouldbemeasured.Severalreviewshavenotedthatthereisalackofconsistencyinhowkeyaspectsofthepsychosocialenviron-ment,suchasjobdemands,autonomy,andworkplacesupportandjobsatisfaction,aremeasuredinindividualstudies(Macfarlaneetal.2009).Thereisalsovariationinboththedomainsinvestigatedandtheapproachtocollectingdomain-specificdata.

Physicalloadisassumedtohavebothanacuteandacumulativeeffectontheoccurrenceofbackpain(Hoogendoornetal.1999).Aloadthatexceedsthefailuretoleranceofthetissue,evenifonlyappliedonce,cancausebackpain.However,thecumulativeloadresultingfromlowermagnitudeloadsmaybeevenmoreimportant.Insuchcases,backpainisassumedtobetheresultofarepeatedapplicationofloadsorthelong-termapplicationofasustainedload.

PainisthemainsymptominmostMSDandtheobjectivefindingsareusuallybasedonfunctionalrestrictionscausedbypain.Painperception,ontheotherhand,isdependentonmanyindividual,psychologicaland

socialfactors,insteadofpathophysiologicalaspects.Therefore,anygivenriskfactorisunlikelytocausemusculoskeletalsymptomsormedicallyverifiabledisordersinallemployees,butthecontextpartlydetermineswhetherdisturbingpainisperceivedornot.

Theeffectsoftheworkenvironmentonhealthmaybemediatedbyatleasttwopathways,assuggestedinthemodeldepictedinfigure3(Coxetal.1994).Ithasbeenarguedthatthephysico-chemical andthepsycho-physiological mechanismsdonotofferalternativeexplanations,buttheyarepresentandinteracttodifferentextentsinallsituations.Whilemanyoftheeffectsofthephysicalenvironmentaremediateddirectlybythephysico-chemicalmechanism,anxietyandfearaboutthatenviron-mentmayalsohaveapsycho-physiologicalimpact.Inturn,theeffectsonhealthofthepsychosocialandorganisationalenvironmentsarelargelymediatedbypsycho-physiologicalprocesses,thoughcertainissues,likeworkplaceviolence,mayhaveadirecteffectthroughphysicalinjury.

indirect effects and moderation of effects

of physical hazards

Occupational health

Hazards in physical work environment

directeffects

Physico-chemicalpathway

mediation

indirect effects and moderation of effects of psychosocial and

organisational hazards

Cognitive and psycho-physiological pathway

mediation

Hazards in psychosocial and organisational work environments

FigurE 3. Work environment and occupational health: a model suggested by Cox and Ferguson (1994)

Fourexplanationsfortheassociationbetweenpsychologicalworkcharacteristicsandmusculoskeletalsymptomshavebeenproposed(Hoogendoornetal.2000);(1)psychosocialworkcharacteristicscandirectlyinfluencethebiomechanicalloadthroughchangesinposture,movementandexertedforces;(2)psychosocialworkcharacteristicsmaytriggerphysiologicmechanisms,suchasincreasedmuscletensionorincreasedhormonalexcretionthatmayinthelongtermleadtoorganicchangesandthedevelopmentorintensificationofmusculoskeletalsymp-tomsormayinfluencepainperceptionandthusincreasesymptoms;(3)psychosocialfactorsmaychangetheabilityofanindividualtocopewithanillnesswhich,inturn,couldinfluencethereportingofmusculoskeletalsymptoms;(4)theassociationmaywellbeconfoundedbytheeffectofphysicalfactorsatwork.

Insystematicreviewsontheeffectivenessofthework-relatedinter-ventions,fivelevelsofevidencehavebeenusedtosummarisetheresults.MostreviewsadapttheclassificationsuggestedbytheCochraneCol-laborationBackReviewGroup(vanTulderetal.2003).Accordingtothisclassification,"strong evidence"referstoconsistentfindingsamongmultiplehighqualityrandomisedcontrolledtrials(RCTs);"moderate evidence"referstoconsistentfindingsamongmultiple lowqualityRCTsand/ornonrandomisedcontrolledclinicaltrials(CCTs)and/oronehighqualityRCT;"limited"referstoonelowqualityRCTand/orCCT;"conflicting"referstoinconsistentfindingsamongmultipletrials(RCTsand/orCCTs);and"no evidence"referstothefactthatnoRCTsorCCTshavebeenidentified.Thisclassificationwasmodifiedquiterecently(Furlanetal.2009)labellingthelevelsaccordingtothequalityoftheevidenceas"high","moderate","low","verylowqual-ity",or"noevidence".

Inconclusion,researchonMSDfacesmanychallengesrelatedtotheappropriatestudymethodsandoutcomes,exposureandsymptomverifi-cation,andthetheoreticalmodelsexplainingtheeffectsofbothphysicalandpsychosocialexposuresandtheirinteraction.Thereisalargebodyofevidencealreadyavailable,butmorehighqualityresearchisdefinitelyneeded.IftheassociationbetweenworkandMSDisrelatedtoagreaterlikelihoodofsymptomsanddisabilitythanthedisorderitself,thisshouldbereflectedinthepreventionactivitiesandergonomicmeasures.

PreviousresearchhasfoundoveronehundredpotentialriskfactorsforLBP(Bakkeretal.2009).AsummaryoftheoccupationalriskfactorsofLBPdiscussedherearepresentedintable1.

Table 1. Work-related risk factors of lbP

Risk factors Reference

Physical risk factors

Manual material handling, including lifting, moving, carrying, and holding loads, as well as bending and twisting; whole-body vibration

Patient handling, high level of physical activity

Whole-body vibration, nursing tasks, heavy physical work, working with one's trunk in a bent and/or twisted position

Occupational bending or twisting

(Hoogendoorn et al. 1999)

(Bakker et al. 2009)

(Wai et al. 2009)

Psychosocial risk factors

Low social support in the workplace

High job demands and low job satisfaction

Low job control and low supervisor support

(Macfarlane et al. 2009)

(Kaila-Kangas et al. 2004)

Accordingtoareviewofphysicalloadduringworkasariskfactorforbackpain(Hoogendoornetal.1999),thereisstrongevidencethatmanualmaterialhandling,includinglifting,moving,carrying,andholdingloads,aswellasbendingandtwistingareriskfactorsforbackpain.Themagnitudeoftheriskestimate(relativerisk/oddsratio)rangedfrom1.5to3.1formanualhandling.Thereisalsostrongevidencethatwhole-bodyvibration

isariskfactorforbackpain(effectestimate4.8),andmoderateevidencethatpatienthandlingandahighlevelofphysicalactivityareriskfactorsforbackpainwiththemagnitudeoftheriskestimatesrangingfrom1.7to2.7(forpatienthandling)andfrom1.5to9.8(forheavyphysicalwork).Inthesensitivityanalysis,however,noevidencewasfoundfortheeffectofheavyphysicalload(Hoogendoornetal.1999).

TheresultsbyHoogendoornetal.arechallengedbyamorerecentsystematicreview.Thisincluded18prospectivecohortstudiesevaluatingspinalmechanicalloadduringworkand/orleisuretimeactivitiesasriskfactorsfornonspecificLBPinpatients(>18yearsofage)freeofLBPatbaseline(Bakkeretal.2009).TheconclusionwasthatthereareseveralhighqualitystudieswithconsistentfindingsthatLBPisnotassociatedwithprolongedstanding/walkingorsittingatwork.Accordingtothisreview,evidenceisconflictingforwhole-bodyvibration,nursingtasks,heavyphysicalwork,andworkingwiththetrunkinabentand/ortwistedpositionasriskfactorsforLBP.

TheconclusionsofBakkeretalhavebeencriticised(Takalaetal.2010).First,theresultsoftheincludedstudiesshouldbeconsideredas"inconsistent",not"conflicting",becausenoneofthestudiesindicatedthatthenon-exposedgroupwouldhaveahigherriskthantheexposedgroup.Second,eveninstudieswithoutstatisticallysignificantresults,trendsdidexistforanelevatedriskwithincreasedlevelsofexposure.

Fivecase-controlstudiesandfiveprospectivecohortstudieswereincludedinanotherrecentsystematicreviewonoccupationalbendingortwistingandLBP.TheconclusionwasthatthereviewedevidencewasconflictingandnotsupportiveofanyclearcausalrelationshipbetweenoccupationalbendingortwistingandLBP(Waietal.2009).However,theresultsdidsuggestthatbendingactivitiesinvolvinghigherdegreesoftrunkflexionwereassociatedwithdisablingtypesofLBPincertainworkingpopulations.

Inadditiontophysicalloadfactorsthereisalsoevidencethatpsycho-socialfactorsplayaroleintheaetiologyofLBP.Forsymptom-freepeople,thereisstrongevidencethatindividualpsychosocialfindingsareariskfac-torfortheincidence(onset)ofLBP.However,thesizeoftheeffectissmall(Waddelletal.2001).Areviewofreviewshasalsobeenpublishedontheassociationsbetweenworkplacepsychosocialfactorsandmusculoskeletalpain(Macfarlaneetal.2009).Thisreviewclaimedthatoutofthespecific

work-relatedpsychosocialfactorsconsidered,theimportantfactorswerejobdemands,support,jobautonomyandjobsatisfaction.Withrespecttobackpain,themostconsistentconclusions(4reviewspositiveoutof6)werewithhighjobdemandsandlowjobsatisfaction.Thereviewempha-sisedtheimportanceofdevelopingstandardisedmethodsforconductingevaluationsofexistingevidence,andtheimportanceofinvestigatingnewlongitudinalstudiestoclarifythetemporalrelationshipbetweenpsycho-socialfactorsandmusculoskeletalpainintheworkplace.

Oneoftheincludedreviews(Hoogendoornetal.2000)foundalsostrongevidenceforlowsocialsupportatworkasariskfactorforLBP.However,thisresultwassensitivetochangesintheratingsystemandthemethodologicalqualityofthestudies.Theauthorsconsideredalsothattheeffectforlowjobsatisfactioncouldbeapossibleresultofinsuf-ficientadjustmentforpsychologicalworkcharacteristicsandphysicalloadatwork.Theyconcludedthatthereseemedtobeevidenceforaneffectofpsychologicalfactorsatworkbutthattheevidencefortheroleofspecificwork-relatedpsychologicalfactorshasnotbeenestablishedyet(Hoogendoornetal.2000).

PsychosocialriskfactorsseemtovaryaccordingtothetypeofLBP.InaFinnishprospectivecohortstudy(Kaila-Kangasetal.2004),lowjobcon-trolandlowsupervisorsupportatbaselinewereassociatedwithincreasedriskofhospitalisationforbackdisordersinthe17yearfollow-up.Therewasnosimilarassociationforintervertebraldiscdisorders.Instead,ithasbeenshowninanotherFinnishstudythatphysicallydemandingworkwasariskfactorforsciaticaamongmen(Kaila-Kangasetal.2009).Theriskincreasedwiththelengthoftheexposureforthefirst20years,butdecreasedthereafter.Thisstudyfoundalsoaremarkablyhighprevalenceofsciaticaamongthosewhowerenotworking.Inthisgroup,sciaticawasstronglyassociatedwithpreviousworkexposures.Theseresultsindicatethatprematurehealth-relatedselectionoutofheavyworkhadoccurred.

TheresultsofphysicalloadexposuresasriskfactorsforLBPinmostreviewshavebeenratherinsensitivetoslightchangesintheassessmentoftheoutcomesandthemethodologicalqualityofthestudies.This,however,doesnotapplytotheresultsforpsychologicalfactors.Thisindicatesthatthebodyofevidencesupportingtheroleofphysicalloadasariskfactorforbackpainissomewhatmoreconsistentthanthatforthepsychosocialfactors.

Table2showstheknownoccupationalphysicalriskfactorsforUED.ThemostcommonlyreportedriskfactorsforUEDasagrouparerepetitivemovements,force,andhand-armvibration,whereaspsychosocialorworkorganisationalriskfactorsincludehighjobdemand,lowdecisionlatitude,lowsocialsupport,aswellasfewrestbreakopportunities(Punnettetal.2004).

Table 2. Work-related risk factors of UeD

Diagnosis Risk factors ReferencePhysical risk factors

uED in general

repetitive movements, force, and hand-arm vibration

For men: High level of physical demand, high repetitiveness of task, postures with arms at or above shoulder levels, tasks with full elbow flexion For women: Postures with extreme wrist bending and use of vibrating hand tools

(Punnett et al. 2004)

(roquelaure et al. 2009)

Epicondylitis repetitive movements of the arms and forceful activities

Handling heavy tools or loads, high hand grip forces, repetitive movements, and work with vibrating tools

(Shiri et al. 2006)

(van rijn et al. 2009a)

CTS Work tasks with vibrating tools, handgrip with high forces, repetitive movements of the hands, and prolonged work with flexed or extended wrist

(Shiri et al. 2009; van rijn et al. 2009b)

Shoulder pain

Physically strenuous work, working with trunk forward flexed or with a hand above shoulder level

Overhead work, repetitive work with shoulder, lifting, pushing or pulling

(Miranda et al. 2001)

(Walker-Bone et al. 2005)

rotator cuff tendinitis

Cumulative working with hand above shoulder level (Miranda et al. 2005)

Forearm pain repetitive tasks (Macfarlane et al. 2000)Psychosocial risk factors

uED in general

High job demand, low decision latitude, low social support, few rest break opportunities

Both high and low job demands

For men: High psychological demand For women: Low level of decision authority in women

(Punnett et al. 2004)

(Macfarlane et al. 2009)

(roquelaure et al. 2009)

Shoulder pain Mental stress

Monotonous work, high job demands and psychological distress

(Miranda et al. 2001)

(Andersen et al. 2003)

Forearm pain Poor satisfaction with level of support from colleagues/supervisor (Macfarlane et al. 2000)

TheriskfactorsforUEDdifferaccordingtothespecificdiagnosis.Handlingofheavytoolsorloadsandrepetitivemovementsareassoci-atedwithlateralepicondylitis,whereasrepetitivemovements,forcefulactivitiesandworkingwithvibratingtoolsareriskfactorsformedialepicondylitis(Shirietal.2006;vanRijnetal.2009a).

Worktasksdemandinghandgripwithhighforcesortheuseofvi-bratingtoolsareassociatedwithanincreasedprevalenceofCTS(Shirietal.2009).Theassociationisstrongerifthesetaskswereaccompaniedbyrepetitivemovementsofthehandorwrist.Inaddition,prolongedworkwithaflexedorextendedwristhasbeenshowntobeariskfactorforCTS(vanRijnetal.2009b)

Consistentfindingshavebeenfoundforrepetitivemovements,vibrationanddurationofemploymentasoccupationalriskfactorsofshoulderpaininareviewwith29cross-sectionalstudies(vanderWindtetal.2000).Nearlyallstudiesthathaveassessedpsychosocialriskfac-torshavereportedatleastonepositiveassociationwithshoulderpain,buttheresultswerenotconsistentacrossstudiesforhighpsychologicaldemands,poorcontrolatwork,poorsocialsupport,orjobdissatisfaction.

Anotherreviewconcludedthatthework-relatedriskfactorsforshoulderpainareoverheadwork,repetitiveworkwiththeshoulder,andlifting,pushingorpulling(Walker-Boneetal.2005).Evidencesuggeststhatcumulativeintensiveshoulderworkparticularlyincor-poratingcombinationsofexposuresisassociatedwithasignificantlyincreasedprevalenceofshoulderdisorders.Thework-relatedfactorsaspredictorsofshoulderpaindifferaccordingtothenatureofthedisorder.Aprospectivestudyfoundthatmentalstressandphysi-callystrenuouswork,aswellasworkingwithtrunkforwardflexedorwithahandabovetheshoulderlevelincreasedincidentshoulderpain,whereaspersistentsevereshoulderpainwasassociatedwithoverloadatworkandworkingwithahandabovetheshoulderlevel(Mirandaetal.2001).

Withrespecttothepsychosocialfactors,monotonouswork,highjobdemandsandpsychologicaldistresswerethreeexposuresthathavebeenshowntoincreasetheriskofshoulderpaininaprospectivestudyamongworkersinindustrialandservicecompanies.Furthermore,poorwork-placesupportfromcolleagues/supervisorsandpsychologicalmorbidityincreasetheriskofadhesivecapsulitis(Andersenetal.2003).

Thegenderoftheemployeealsoseemstoplayaroleinriskfac-torsofUED.InaFrenchstudywherespecificUEDwerediagnosedbytrainedOHphysicians,theriskfactorsdifferedbetweenmenandwomen(Roquelaureetal.2009).Highlevelofphysicaldemands,highrepetitivenessofthetask,postureswiththearmsatoraboveshoulderlevels,andtaskswithfullelbowflexionincreasedtheriskofUEDinmen.Inwomen,UEDwereassociatedwithpostureswithextremewristbendinganduseofvibratinghandtools.PsychosocialriskfactorswereonlymodestlyassociatedwithUED,highpsychologicaldemandsinmenandalowlevelofdecisionauthorityinwomen.Anotherstudyfoundsimilarresultsandtheauthorsconcludedthatgenderdifferencesinresponsetophysicalworkexposuresmayreflectgendersegregationinworkandpotentialdifferencesinforceproducingcapacity(Silver-steinetal.2009).

Thereisevidencethatbothindividualpsychologicalfactors(worryanddistress)andworkplacefactorscorrelatewiththeonsetofpaininUED(Shawetal.2002b).Theavailableevidencealsosuggeststhatpsy-chologicalandoccupationalpsychosocialvariableshaveanimportantroleintheaetiologyofshoulderpain.Inareviewofreviews(Macfarlaneetal.2009)thereweresixreviewsconductedonneck/shoulderandforearmpainandpsychologicalfactors(altogether85individualstudies)whichconcludedthatbothhighandlowjobdemandswereassociatedfactors.Lowjobdemandsincludedthejobbeingevaluatedasmonotonousorwithinsufficientuseofskills.

Non-specificforearmpainhasbeenshowntobeassociatedwithre-petitivetasks(Macfarlaneetal.2000).Inthesamestudy,newonsetfore-armpainwasindependentlypredictedbypsychologicaldistress,aspectsofillnessbehaviour,aswellaspsychosocialfactorssuchassatisfactionwiththelevelofsupportfromcolleagues/supervisor.Infact,non-specificshoulderpainseemstobemorehighlyrelatedtopsychosocialandin-dividualpsychologicalfactors,whereaschronicrotatorcufftendinitisisrelatedtocumulativeloadingontheshoulder,ageandinsulin-dependentdiabetesmellitus(Mirandaetal.2005;Viikari-Junturaetal.2008).

Asaconclusion,itseemsthatthemorespecificthedisorder,themoreconvincingistheevidencethatcertainphysicalloadexposuresatworkareriskfactors.Psychosocialriskfactorsseemtoplayamoresignificantpartintheaetiologyofmorenon-specificUED.Therefore,thechallenge

inmanagingwork-relatedUEDistomakethecorrectdiagnosisinordertofindthebestwork-relatedintervention.

3.1.4. Work-related interventions in preventing musculoskeletal disorders

InterventionstudiesaimingatthepreventionofMSDusuallyincludeallavailableemployeesintheworkplaceregardlessofwhethertheyhavehadthedisorderpreviouslyornot.Consequently,it ishardlyeverpossibletodistinguishbetweenprimaryandsecondarypreventionstudies.Theinterventionisdirectedtoboththosewithorwithoutpriorsymptomsandrelateddisability,andthosewithpresentsymptoms.Thesesubgroups,however,areusuallytakenintoconsiderationinthestatisticalanalyses.

Multicomponentinterventionshaveagreaterchancethansingleinterventionsintheirsuccessinreducingwork-relatedMSDaccordingtoacomprehensivereview(Silversteinetal.2004).Modifyingindividualfactorsisnotparticularlyusefulinpreventingwork-relatedMSD,butexerciseappearstobeeffectiveinmitigatingsomeoftheconsequences.Inaddition,participatoryapproacheshavebeenoften,thoughnotal-ways,successful.

Thereviewoftheevidenceontheeffectivenessoflumbarsupports,educationandexerciseintheprimarypreventionofbackpainintheworkplacewasupdatedin2004(vanPoppeletal.2004).Accordingtofivenewpapersaddedtotheelevenpreviouslyavailabletrials,therewasstillnoevidencetosupporttheuseoflumbarsupportsoreducationinthepreventiononbackpain.Moreover,evenwhenincludingtheresultsofthenewtrials,therewasstillonlylimitedevidencetosupporttheeffectivenessofexercise.

ExerciseinterventionstopreventLBPamongemployeeshaveanef-fectonnewepisodesofLBPaccordingtoanothersystematicliteraturereviewontheeffectivenessofLBPinterventionsintheworkplace(Tveitoetal.2004).Instead,education,lumbarsupportsormultidisciplinaryinterventionsshowednosupportfortheireffectivenessinpreventingbackpain.Similarconclusionswerereachedinanotherreview(Bosetal.2006):trainingandeducationalonewerenotsufficienttoachieveanydecreaseinmusculoskeletalsymptoms,butinadditiontoergonomic

intervention(i.e.,theuseofadditionalmechanicalorotheraidequip-ment),adecreaseofmusculoskeletalsymptomscouldbeattained.

Amixedlevelofevidencewasobservedforthegeneralquestion,whetherofficeinterventionsamongcomputerterminalusershaveanyeffectonmusculoskeletalorvisualhealth(Breweretal.2006).Thisre-viewincludednotonlyRCTs,butstudiesusingdifferentstudydesigns.Moderateevidencewasobservedfor(1)noeffectofworkstationadjust-ment,(2)noeffectofrestbreaksandexercise,and(3)positiveeffectofalternativepointingdevicesonmusculoskeletaloutcomesincomparisontoaconventionalmouse.Mixedorinsufficientevidenceofeffectwasobservedforallotherinterventions.

Thereisnoevidencetosupportthebenefitsofproductionsystems/organisationalcultureinterventions(Boococketal.2007).Thatreviewidentifiednosingle-dimensionalormulti-dimensionalstrategyforinterventionthatwasconsideredasbeingeffectiveacrossoccupationalsettings.Trialshavemainlyincludedcomputerterminalworkersandshownonlyamodesteffectofworkplaceadjustments,exerciseandad-viceasapproachesforpreventingandmanagingneck/upperextremitymusculoskeletalconditions.

Burtonetal(Burtonetal.2009)haveconcludedthateffectivein-terventionsforUEDrequireamultimodalapproachinwhichspecifictreatmentwouldbecoupledwithworkplaceaccommodation.Theyalsoemphasizedthatanintegrativeapproachbyallstakeholders(employer,workerandhealthprofessional)wasafundamentalrequirementinfacili-tatinganearlyreturntowork.Othershaveemphasizedtheimportanceofcommunicatingwithsupervisors.Theirneedsandchallengeshavetobeidentifiedinadditiontotailoringtheprogramtoaccommodateproduction,work-taskneeds,andtobeasmarginallydisruptiveaspos-sible(Feuersteinetal.2006).

Inaclusterrandomisedcontrolledtrial(Haukkaetal.2010)kitchenworkersintheinterventiongroupwereencouragedtoactivelyparticipateinworkanalysis,planning,andimplementingtheergonomicchangesaimedtodecreasephysicalandmentalworkload.Duringthefollow-up,nofavourable,evenadverse,effectsonthepsychosocialfactorsatworkwerefound.Inaddition,theseauthorshavereportedpreviouslythattherewasnoevidencefortheeffectivenessoftheinterventioninreducingtheperceivedphysicalloadorpreventingMSD(Haukkaetal.

2008).However,asignificantlyreducedriskoffutureshoulderpainwasobservedinasubgroupofemployees,whoseworktasksperceivedasthemoststrenuouswerereduced(Pehkonenetal.2009).

TheabovementionedRCTwasincludedinthereviewontheeffec-tivenessofergonomicworkplaceinterventionsonLBPandneckpain(Driessenetal.2010).Thisreviewacceptedonlyrandomisedcontrolledtrials,whichincludedinterventionstargetedatchangingthebiomechani-calexposureattheworkplaceoronchangingtheworkorganisation.Theresultswerethatthereislowtomoderatequalityevidencethatthesekindsofinterventionsarenotanymoreeffectivethannoergonomicinterven-tiononshortandlongtermLBPandneckpainincidenceorprevalence,shortandlongtermLBPintensity,andshorttermneckpainintensity.Therewaslowqualityevidencethataphysicalergonomicintervention(forexample,armboard)wassignificantlymoreeffectiveonthereduc-tionofneckpainoverthelongtermthannoergonomicintervention.

Inconclusion,theresultsofpreviousstudiesonwork-relatedriskfactorsforMSDhavenotbeenconfirmedininterventionstudies.Thisiseitherduetothefactthatinterventionstudieshavefailedtomodifyallrelevantwork-relatedfactorsattheworkplace,orthatmusculoskeletalsymptomsanddisordersareonlypartlycausedbywork-relatedfactors,andtheotherrelevantfactorsarebeingleftoutsidethescopeoftheinterventions.

3.2. Work-related risk factors of sickness absence

3.2.1. general

PainandothersymptomscausedbyMSDcanleadtosignificantpersonaldistress,lossoffunctionanddisability.Identifyingthefactorsassociatedwithdecreasedmusculoskeletalfunctionmayleadtothedevelopmentofmoreeffectiveinterventions.Toolsforearlyidentificationofworkerswithmusculoskeletalsymptomswhoareatahighriskofprolongeddis-abilitywouldhelptofocusclinicalattentiononthepatientswhoneeditmost,whilehelpingtoreduceunnecessaryinterventions(andcosts)amongothers(Dionneetal.2005).Bytargetingspecifictreatmentandrehabilitationtopotentialhigh-riskcasesearly,onecouldarguethatit

shouldbepossibletopreventadverseoutcomesincludingunnecessaryprolongationofdisability.

ClinicalpracticeguidelineshaveprovidedusefulalgorithmsforthemedicalmanagementofLBP,butthesedonotaddresscertainfactorsthatmayinfluenceLBPrelateddisability(Shawetal.2001).Basedontheevidencethatmultiplefactorscontributetodisability,interventionsthataddressmedical,workplace,andpsychosocialissuesshould,intheory,bemorelikelytoproduceimprovedoutcomesthantraditionalmedicaltreatmentalone.

Attentionhastobepaidtothefactthatagreatdealofavailableevi-denceonMSDandrelateddisabilityhasfocusedondisordersconsideredasbeingwork-related.Inmanycountriesthisentitlestheworkertofileaworker'scompensationclaimfollowedbytherighttofreemedicalcareorotherbenefits.Ithasbeenshownearlierthatwork-relatedLBPisdistinctfromsimilarnon-work-relatedconditionsinthatasuddenonsetisusu-allyreported,anddisabilityoutcomesareusuallylessfavourabledespitemoreintensivetreatments(Shawetal.2005).ThissamephenomenonislikelytoapplytootherMSDaswell,takingintoconsiderationthesignificanceoftheindividual'sownperceptionsonthedisabilityoutcome(formore,seechapter3.4.1.).

AccordingtoaFinnishstudyinvestigatingworkerspredominantlyengagedinphysicalwork(Taimelaetal.2007),self-ratedfutureworkabilityandperceivedmusculoskeletalimpairmentwerestrongdetermi-nantsofsicknessabsence.Amongthosesusceptibletotakingsickleave,theestimatedmeannumberofabsencedaysincreasedby14 %foreachincreaseofoneunitoftheimpairmentscoreonascalefromzerototen.

AccordingtotheannualstatisticsoftheFinnishSocialInsuranceInsti-tution,backpain(M40–54inInternationalClassificationofDisease)accountedfor14 %ofallcompensateddisabilitydays,and40 %ofalldisabilitydayscausedprimarilybyMSD(Kansaneläkelaitos2008).Thedirectfinancialcostsduetoback-relateddisabilitydayswas113M€totheSocialInsuranceInstitution(15 %oftotalcosts).

Table3showswork-relatedriskfactorsofsicknessabsenceduetoLBP.Thereisepidemiologicalandclinicalevidencethatcareseekingand

backdisabilitydependmoreoncomplexindividualandwork-relatedpsychosocialfactorsthanonclinicalfeaturesorthephysicaldemandsofwork(Waddelletal.2001).

Table 3. Work-related risk factors of sickness absence due to lbP

Risk factors ReferencePhysical risk factors

Harmful biomechanical loads

Exposure at work to trunk flexion, trunk rotation and lifting

Doing heavy physical work

Heavier occupations with no modified duty

(Wickström et al. 1998)

(Steenstra et al. 2005)

(Shaw et al. 2001)

Psychosocial risk factors

Lack of recognition and respect at work

Perceived control and low support at the workplace

Self-reported job demands

Low job satisfaction/job dissatisfaction

(Wickström et al. 1998)

(Shaw et al. 2001; Werner et al. 2009)

(Shaw et al. 2001)

(Truchon et al. 2000; Hoogendoorn et al. 2002)

Psychological risk factors

Negative beliefs about LBP, poor coping abilities

Distress (psychological distress, depressive symptoms, and depressive mood)

Pain avoidance beliefs, pain coping, psychological distress, problem solving orientation

Subjective negative appraisal of one's ability to work

(Werner et al. 2009)

(Shaw et al. 2001; Pincus et al. 2002)

(Shaw et al. 2002b)

(Truchon et al. 2000)

Other High level of disability, social isolation, receiving a high level of compensation

Delayed reporting, severity of pain and functional impact, shorter job tenure

(Steenstra et al. 2005)

(Shaw et al. 2001)

Nocoresetofpredictorsexistsforsicknessabsenceingeneral,accord-ingtoasystematicreviewonevidenceofpredictorsforsicknessabsenceinpatientswithnon-specificLBP(Kuijeretal.2006).Thereviewstud-iedseparatelythepredictorsforabsencethreshold(i.e.,thedecisiontoreportsick)andRTWthreshold(i.e.,decisiontoreturntowork).Withrespecttotheabsencethreshold,nopredictorswerefoundforfactorspredictingsicknessabsenceatthemomentoffollow-upmeasurement,andnoconsistentevidencewasfoundfortotalnumberofsickleavedays.

Inanon-systematicreviewthedeterminantsofsicknessabsenceduetoLBPwerestudiedseparatelyforthecharacteristicsofthesick-listedworker,thecharacteristicsofthesick-listingperson(thedoctor),work-place,andtheculturalandeconomicconditionsofthesociety(Werneretal.2009).ThisevidenceshowsthatnegativebeliefsaboutLBP,co-morbidities,andpoorcopingabilitiesseemtobethemostimportantdeterminantsforclaimingsickleaveforLPB.Moreover,thedoctorwillusuallyfollowthepatient'sdemandstobegivensickleave.Theem-ployee'sperceivedsupportandcontrolattheworkplaceseemtobeofimportanceinpreventingsickleave.Nationaldifferencesineconomiccompensationforsickleaveappeartobeassociatedwithdifferencesinratesofsicknessabsence.

AccordingtotheresultsofaFinnishstudy,thetake-upofsickleaveattributedtoLBPwaspredictedbyexposuretoharmfulbiomechanicalloads(rateratio3.1).Inaddition,lackofrecognitionandrespectatworkpredictedsickleavecausedbyLBP(rateratio2.0)(Wickströmetal.1998).

Self-reportedjobdemandsappeartobebetterpredictiveofdisabilitythanmoreobjectivejobassessmentmeasures(Shawetal.2001).Workerself-reportsofgreaterphysicaldemandsofthejobappeartobepredictiveofchronicLBPdisability,whereasmoreobjectivemeasuresofphysicaldemandsarenot.Althoughworkerperceptionsofergonomicexposuremaydifferfrommoreobjectiveworkplaceassessmentstrategies,botharesubjecttoerror,butworkerreportappearstobemorestronglycorrelatedwithdisabilityoutcomes.Theauthorsconcluded,thatself-reportsmaybemoreaccurateinidentifyingunusualorhighriskdemands.However,themodestcorrelationbetweenpain,functionallimitations,andworkdisabilitysuggeststhattheseoutcomesmaydevelopsomewhatindepend-entlyfromeachotherduringtherecoveryperiodfollowingacuteLBP(Shawetal.2009a).

Accordingtoareviewonpsychologicalfactorsaspredictorsofchronic-ity/disability,themostconsistentfindingwasthatdistress(psychologicaldistress,depressivesymptoms,anddepressivemood)isasignificantpre-dictorofunfavourableoutcome,particularlyinprimarycare(Pincusetal.2002).Thiseffectwasindependentofclinicalfactors,suchaspainandfunctionatbaseline.Inaddition,therewasmoderateevidenceforsoma-tisationhavingaroleintheprogressiontopersistentsymptomsand/ordisability,buttheeffectsizewasfoundtovary.TheauthorsconcludedthatpsychologicalfactorsplayanimportantroleinthetransitiontochronicLBP,andthattheymaycontributeatleastasmuchasclinicalfactors.

AnumberofpsychologicalvariableshavebeenshowntomediatethefunctionallimitationsofMSD,especiallychronicLBP.Thesefactorsincludepainavoidancebeliefs,paincoping,psychologicaldistress,andproblemsolvingorientation(Shawetal.2002b).

Ina3-yearprospectivecohortstudyonriskfactorsofsicknessabsenceduetoLBP(Hoogendoornetal.2002),significantrateratios,rangingfrom2.0–3.2,werefoundforexposureatworktotrunkflexion,trunkrotation,lifting,andlowjobsatisfaction.Inaddition,non-significantrateratiosofabout1.4werefoundforlowsupervisorsupportandlowco-workersupport.

Inareviewwithonlyinceptioncohortstudies(Steenstraetal.2005),thepatientswithLBPwiththehighestriskforlongtermabsencewereolderfemalescharacterisedbyradiatingpain,highlevelofdisabilityandsocialisolation,doingheavyphysicalwork,andreceivingahighlevelofcompensation.ItseemsthatinspiteoftheeffectofhistoryofLBPonrecurrencesofbackpain,ahistoryofLBPdoesnotinfluencethedura-tionofsickleaveduetoLBP.

Asystematicreviewofstudiesonthebiopsychosocialfactorspre-dictiveofnotreturningtoworkduetoLBPexamined18prospectivestudies(Truchonetal.2000).Thework-relatedpredictivefactorswereasubjectivenegativeappraisalofone'sabilitytoworkandjobdissatisfac-tion.Theimportanceofcertainpsychologicalvariables,likeattitudesandbeliefs,aswellascopingstrategies,wasalsoemerging.

Areviewofstudiesassessingthevalueofvariousprognosticfactorstopredictextendeddisabilityafteranacuteepisodeof"occupationallyattributed"LBPfoundthatsignificantprognosticfactorsincludelowworkplacesupport,personalstress,shorterjobtenure,priorepisodes,

heavieroccupationswithnomodifiedduty,delayedreporting,severityofpainandfunctionalimpact,radicularfindings,andextremesymptomreporting(Shawetal.2001).

ItislogicalthatclinicaldataalonedoesnotpredictreliablytheriskofsicknessabsenceinLBP.Painasasubjectiveexperienceandfunctionallimitationsinrelationtoworkdemandsmaycomplicatethepossibili-tiestocontinueworking.MoreresearchisneededtocreatealternativemethodsofsupportingworkingdespitethepresenceofLBP,takingintoaccountthecumulatingevidenceofthebenefitsofstayingactiveinthemanagementofMSD.

UEDcauseremarkabledisabilityresultinginlostproductivity.Forexample,inWashingtonStatein1990–1998,theaveragetimelostfromworkwas170–251dayspercompensationclaimrelatedtoUED(Silversteinetal.2002).

Across-sectionalstudywasperformedamongworkersrepresentingavarietyofoccupationsbutsharingacommonworkers'compensationandemployeehealthbenefitprogram(Shawetal.2002b).Theresultsshowedthatfactorsotherthanpainexplainedtwiceasmuchvariabilityinupperextremityfunctionallimitationasexplainedbypainalone.Thissuggeststhatfunctionallimitationmaypersistsomewhatindependentlyofpainamelioration.Aftercontrollingforpainandgenderinamultipleregressionanalysis,thefactorscontributingtofunctionallimitationwerenon-painrelatedupperextremitysymptoms(forexample,sleepdistur-bance,numbness,tingling),symptomsinbothhands,feelingsofbeingoverwhelmedbypain,lowconfidenceinproblemsolvingabilities,andhigherergonomicriskfactorexposuresatwork.

3.2.4. Prevention of sickness absence caused by musculoskeletal disorders

Thischapterevaluatesinterventionsaimingatreducingthefrequencyofmusculoskeletalsicknessabsence(totalnumberofspells/allemployees)orthelengthofmusculoskeletalsicknessabsence(sick-leavedays/sick-listedpersons).

Thetreatmentchosenbythephysicianiscrucialfortherecoveryprocess.Acontrolledtrialshowedthataslittleastwodaysofbedrestinstructedbythephysicianleadtoaslowerrecoverythantheavoidanceofbedrest,aswellastolongersickleaves(Malmivaaraetal.1995).ThisstudyofworkerswithacuteLBPsuggeststhatavoidingbedrestandmaintainingordinaryactivityleadtothemostrapidrecovery.

Screeningformedical"redflags"anddiagnostictriageisimportantintheexclusionofseriousspinaldiseasesandnerverootproblems(Waddelletal.2001).Sinceindividualandwork-relatedpsychosocialfactorsplayanimportantroleinthepersistenceofsymptomsanddis-ability,screeningfor"yellowflags"canhelptoidentifythoseworkerswithLBPwhoareatriskofdevelopingchronicpainanddisability.Laterthesystemof"yellowflags"wasrefinedandworkplacefactorswerecategorisedeitheras"blackflags"includingactualworkplaceconditionsthatcanaffectdisability,or"blueflags"includingindividualperceptionsaboutwork,whetheraccurateorinaccurate,thatcanaffectdisability(Shawetal.2009b).

Blueflagshavebeenconceptualisedasworkerperceptionsofastress-ful,unsupportive,unfulfilling,orhighlydemandingworkenvironment.Blackflagsincludebothemployerandinsurancesystemcharacteristicsaswellasobjectivemeasuresofphysicaldemandsandjobcharacteristics(Shawetal.2009b).Ithasbeenclaimedthatabetterunderstandingofthemeaning(thoughts,beliefsandattitudes)thatpatientsattributetotheirpaincouldbeacriticalsteptowardimprovingreturntoworkoutcomes(Loiseletal.2005).

Althoughworkingconditionswithuncomfortableworkingposi-tions,liftingorcarryingloads,pushingandpullingloadsaswellastheuseofvibratingtools,haveallbeenfoundtobeassociatedwithsicknessabsence,ithasbeenstatedthatmanyyearsofimplementingergonomicadaptationshavenotreducedtheincidenceofsicknessabsence(Werneretal.2009).

ACochranereview(vanOostrometal.2009)hasbeenpublishedfocusingstrictlyonrandomisedcontrolledtrials.Theresultsshowedthatwhencomparedtousualcare,thereismoderate-qualityevidencetosupporttheuseofworkplaceinterventionscarriedoutclosetotheworkplaceandincollaborationwiththekeystakeholdersinordertopreventworkdisabilityandreducesicknessabsenceamongworkers

withMSD.Noevidencewasfoundforthebenefitsofworkplacein-terventionsonhealthoutcomes(forexample,painorfunctionalsta-tus).ThiswasconsideredassupportforthehypothesisthatRTWandresolutionofsymptomsarenotequivalent.Inotherwords,workplaceinterventionstendtoaddresstheworkdisabilityproblemandnottheunderlyingmedicalproblem.

Thesupervisors'roleinthemanagementofmusculoskeletalpainhasbeenevaluatedinacontrolledcasestudy(Shawetal.2006).Elevensupervisorsinaninterventiongroupand12supervisorsinadelayedinterventioncontrolgroupfromthesameplantwereprovidedwithtwo2-hourtrainingworkshopsseparatedby4to7days.Thefundamentalmessageintheworkshopswasthatsupportive,proactive,andcollabora-tivecommunicationswithemployeesaboutergonomicriskfactorsandmusculoskeletalpainanddiscomfortwouldbelikelytoreducedisabilitycostsandimproveemployeemorale,productivityandretention.Work-ers'compensationclaimsdatainthesevenmonthsbeforeandaftertheinterventionshoweda47 %reductioninnewclaimsandan18 %reductioninactivelost-timeclaimsversus27 %and7 %,respectively,inthecontrolgroup.Accordingtothatstudy,improvingtheresponseoffrontlinesupervisorstoemployees'work-relatedhealthandsafetyconcernscouldachievesustainablereductionsininjuryclaimsanddis-abilitycosts.

Basedoninterviewswith30employeesShawetal.(2003b)devel-oped11commonthemesfortheroleofsupervisorstopreventwork-placedisabilityafterinjury:accommodationtoreduceergonomicrisksordiscomfort,communicatingwithworkers,responsiveness,concernforwelfare,empathy/support,effortstounderstandtheemployee'ssituation,fairness/respect,follow-up,shareddecisionmaking,coor-dinatingwithmedicalproviders,andobtainingco-workersupportofaccommodation.

Severalstudiesperformedindifferentcountrieshaveshownamis-matchbetweenpublicbeliefsaboutbackpainandcurrentscientificevidence(Buchbinderetal.2008).Sincebeliefsandattitudesaboutbackpainareassociatedwiththedevelopmentofchronicity,itisapparentthatstrategiesareneededthatalignpublicviewswithcurrentevidence.MediacampaignsinScotlandandNorwayhighlightingtheawarenessofstayingactivethroughanepisodeofLBPdidnotchangesickness

behaviourdespiteimprovedbeliefsinthegeneralpublic.However,anearliercampaigninAustraliawasfollowedbyacleardeclineinthenumberofclaimsforbackpain,ratesofcompensateddaysandcostsofmedicalcare.ThepossibleexplanationforthisisthatonlyinAustraliawerespecificadvertisementsaimedatemployersshowingthebenefitsofreintegratingemployees,theimportanceofmodifiedwork,andthepenaltiesinvolvedfornoncompliance(monetaryfines).

InNorway,inadditiontoamediacampaignaimingatimprovingbeliefsaboutLBPinthegeneralpublic,aprojecttrainedpeeradvisersinsixparticipatingworkplaces(Werneretal.2007).Thetaskofthispeeradviserwastoprovideinformationaimedatreducingfearofthepain,supportiveadvice,andarrangingformodificationsofworkloadsforalimitedperiodoftime.Eventhoughtheprevalenceofbackpainremainedconstantthroughoutthestudyperiod(threeyears),thecombinationofpeersupportgivenbyatrainedforeman,unionleaderorpersonnelofficerandmodifiedworkloadseemedtohavesupplementaleffectstoageneralmediacampaigninreducingsicknessabsenceduetoLBPandimprovementsinbeliefsaboutbackpain.

3.3. Work-related determinants of sickness presenteeism

Intherecentpast,theworker'sabilityorcapacitytoproducegoodsordeliverserviceswhilesufferingfromMSDhasbeenofparticularinterestintheareaofoccupationalresearch.Escorpizohasproposedthatworkproductivitywithinthecontextofwork-relatedMSDisdeterminedbythehealthconditionitself,thecapacity,desireanddifficultyofworking,aswellaswork-lifebalanceandnon-occupationalfactors(Escorpizo2008).Themeasurementofworkproductivityiscrucialtoinitiating,evaluating,andmonitoringdisabilitymanagement,forexample,em-ployeewellnessandergonomicprograms,andclinicalinterventionsinthemanagementofMSD.

InaFinnishpostalsurveyoflabourunionmembers(Böckermanetal.2009),presenteeism("presentatworkinspiteofsickness")wasassociatedwithpermanentfull-timework,shiftorperiodwork,regularovertime,overlongweeklyworkingtime,andefficiencyrequirements

atwork.Ontheotherhand,lowerlevelsofpresenteeismwereassoci-atedwiththepossibilityofreplacementbyasubstitute,matchbetweendesiredandactualworkinghours,andthepossibilityoftakingashortsickleavewithouttheneedforsicknesscertificate.

Accordingtoasystematicreviewonemployeehealthandpresenteeism(Schultzetal.2007a),thestudiesintheliteraturefocusingonMSDaresurprisinglyrare.Mostoftheearlierstudieshaveassessedproductivitylossrelatedtoself-reportedsymptoms,whereasthereisaverylimitednumberofstudiesonproductivitylossassociatedwithclinicallydiag-nosedMSD.Thenatureofthemusculoskeletalconditionpresumablyaffectsproductivity,andtheriskfactorsforproductivitylossrelatedtovariousdisordersmayvary.Littleisknownoftheeffectsofthemuscu-loskeletaldiagnosesonproductivityloss.

SomeNorth-AmericansurveysonpresenteeismhavenotfocusedonlyonMSDbutalsoonotherhealthconditions.Amongworkersparticipatinginatelephonesurveymeasuringbothabsenteeismandreducedperformanceduetocommonpainconditions,thosereport-ingbackpainhadaveragelostproductivetimeof5.2hoursperweek(Stewartetal.2003).Themajority(77 %)ofthelostproductivityduetoanypainconditionwasexplainedbyreducedperformancewhileatworkandnotbyworkabsence.Inanothersurvey(Loeppkeetal.2007),backorneckpainwasthetopmedicalconditionaccountingforannualmedical,drug,andproductivitylosscostsper1000fulltimeemployeesinalltypesofcompanies.

Table4liststheknownwork-relateddeterminantsofsicknesspresen-teeismduetoMSD.Poorhealthhasbeenproposedtobeaprerequisiteforsicknesspresenteeism.Inaddition,severalotherfactorsrelatedtoworkandpersonalcircumstanceshavealsobeenassociatedwithpresenteeism,suchaslowreplaceabilityorhighattendancerequirements,forexample,havingtocompensateforallworknotdoneafteraperiodofabsence,lackofworkresources,timepressure,jobstress,jobinsecurity,andlongworkhours(Bergströmetal.2009).Personalfactors,despitehavingasomewhatweakerrelationtopresenteeismthanworkfactors,includedfinancialproblems,lackofindividualboundaries,over-commitmenttowork,conservativeattitudestowardsicknessabsence,ageandlimitededucation(Bergströmetal.2009).

Table 4. Work-related determinants of sickness presenteeism

Determinants Reference

Individual factors

Poor health, financial problems, conservative attitudes toward sickness absence, age, limited education

Worse physical health, more functional disability

Musculoskeletal complaints, worse physical, mental and general health, recent absenteeism

Physical exercise fewer than 8 times during the last month

(Bergström et al. 2009)

(Lötters et al. 2005)

(Meerding et al. 2005)

(Hagberg et al. 2002)

Work-related factors

Permanent full-time work, shift or period work, regular overtime, overlong weekly working time, and efficiency requirements at work

Low replaceability or high attendance requirements at work for example, having to compensate for all work after a period of absence, lack of work resources, time pressure, job insecurity, and long work hours

Working overtime, computer mouse use for more than 0.5 h/day

(Böckerman et al. 2009)

Psychosocial and psychological factors

Job stress, lack of individual boundaries, over-commitment to work

Poorer relations with the supervisor

Job demands

(Lötters et al. 2005)

Reducedproductivityafter2-to6-weeksicknessabsenceduetoMSDwasquantifiedinaprospectivecohortstudyusingself-admin-isteredquestionnaires(Löttersetal.2005).Reducedproductivitywasprevalentfor60 %oftheworkersaftertheyreturnedtowork,andfor40 %stillatthe12-monthfollow-up.Worsephysicalhealth,

morefunctionaldisabilityandpoorerrelationswiththesupervisorwereassociatedwithproductivitylossshortlyafterreturntowork.Recurrentsickleavewasthegreatestpredictorofproductivitylossatthefollow-up.

Twoquestionnairesonproductivityloss("HealthandLaborQues-tionnaire"and"QuantityandQuality")werecomparedamongtwopopulationsdoingjobswithhighphysicaleffort(Meerdingetal.2005).Abouthalfoftheworkerswithhealthproblemsonthelastworkingdayreportedreducedworkproductivity.Thiswassignificantlyassociatedwithmusculoskeletalcomplaints,worsephysical,mentalandgeneralhealth,andrecentabsenteeism.Self-reportedproductivityusingaQuantityandQuality(QQ)instrumentcorrelatedsignificantlywithobjectiveworkoutput.

InaSwedishstudy(Hagbergetal.2002)amongwhite-collarcom-puterusers8 %ofallemployeesreportedreducedproductivityduetomusculoskeletalsymptoms.Themeanmagnitudeofreductionwas15 %forwomenand13 %formen.Workingovertimeandjobdemandswereriskfactorsforself-reportedreducedproductivityduetoneckandbacksymptoms,whereasphysicalexercisefewerthan8timesduringthelastmonthwasariskfactorforproductivitylossduetoneck,shoulderandupperlimbpain(Hagbergetal.2007).Inaddition,computermouseuseformorethan0.5h/daywasariskfactorforreducedproductivityowingtoshoulderandupperlimbsymptoms.

Inastudyof654computerworkerswithneck/shoulderorhand/armsymptoms(vandenHeuveletal.2007),productivitylosswasin-volvedin26 %,andmoreoften(36 %)incasesreportingbothneck/shoulderandhand/armsymptoms.Mostoftheproductivitylossinthearm/handcaseswasduepresenteeismandsicknessabsenteeismwaspresentinonly11 %ofthecases.Overallproductivitylosswasassociatedwithpainintensity,higheffortregardlessoftherewardlevel,andlowjobsatisfaction.

Inaone-yearfollow-upstudyamong771youngadultswhoreportedneckorupperextremitysymptoms,butnoproductivitylossatbaseline,theriskfactorsofproductivitylossweresymptomsinseverallocations,longerpersistenceofsymptoms,andcomputerterminaluseof8–14hours/weekduringleisuretime(Boströmetal.2008).Astrongerrela-tionshipwasfoundifthreeorfourriskfactorswerepresent.

Inaddition,severalstudieshavefound,somewhatunexpectedly,thattheyoungeremployeesreportmorehealth-relatedproductivitylossthanolderemployees(Hagbergetal.2002;Collinsetal.2005;Alaviniaetal.2009).

3.3.1. Prevention of sickness presenteeism associated with musculoskeletal disorders

InaDutchstudy(vandenHeuveletal.2003),workerswithcomplaintsintheneckorupperlimbwererandomizedintoacontrolgroup,oneinterventiongroupencouragedtotakeextrabreaks,andanotherinter-ventiongroupencouragedtoperformexercisesduringtheextrabreaks.Afteran8-weekperiod,thesubjectsintheinterventiongroupwithbreaksonlyshowedhigherproductivity(morekeystrokes)thanthecontrolgroup.Thestrokeaccuracyrateinbothinterventiongroupswashigherthaninthecontrolgroup.However,therewerenosignificantdifferencesbetweenthethreegroupsinthereportedseverityorfrequencyofthecomplaintsbeforeandaftertheintervention.

Inanotherstudy(Rempeletal.2006),agroupofcomputertermi-nalworkersintheUnitedStateswasrandomisedtoreceiveergonomicstrainingonly,trainingplusatrackballorforearmsupport,ortrainingandbothatrackballandaforearmsupport.Despitethefactthattheforearmsupportcombinedwithergonomictrainingseemedtopreventupperbodymusculoskeletalsymptoms,therewerenosignificantdiffer-encesbetweentheinterventiongroupsineitherthecompanytrackedproductivitymeasuresorinself-assessedproductivity.

Cost-effectivenessofanactive implementationstrategyfortheDutchphysiotherapyguidelineforLBPhasbeenstudiedinaRCTincludingalsoproductivitycostsasanoutcomemeasure(Hoeijenbosetal.2005).Abouthalfofthepatientsatbaselinereportedproduc-tivitylossduetoLBPcorrespondingtoalmost2hoursonaverageperday.Comparedtobaseline,significantlymorepatientswereseenwithoutanyproductivitylossinboththeinterventionandcontrolgroupafter6(56 %and64 %,respectively)and12weeks(71 %inbothgroups).Thedifferencesbetweenthetwogroups,however,werenotstatisticallysignificant.

3.4. Determinants of return to work

TheprimarygoalsofemployeerehabilitationandRTWprogramsmayappeartobethepayer'sinterestinreducingdisabilitycosts,butthereareadditionalincentives:humanrightslegislationinmanycountriesprohibitsdiscriminationinemploymentpracticesonthebasisofdis-abilitystatus(Brookeretal.2001).

AccordingtoasystematicreviewofthequantitativeliteratureonworkplacebasedRTWinterventions,thereisstrongevidencethatworkdisabilitydurationissignificantlyreducedbyworkaccommodationoffersandcontactbetweenhealthcareproviderandtheworkplace(Francheetal.2005).Moderateevidencewasfoundthatdisabilitydurationisalsoreducedbyinterventionswhichincludeearlycontactwiththeworkerbytheworkplace,ergonomicworksitevisits,andthepresenceofaRTWcoordinator.Thus,forthesefiveinterventioncomponents,therewasmoderateevidencethattheyreducecostsassociatedwithworkdisabilitydurationbuttherewasinsufficientorlimitedevidenceforthesustain-abilityoftheseeffects.

Aconsensuspanelof33researchersandstakeholdersselectedkeyfactorsinbackdisabilitypreventionfollowingaliteraturesearchontheassessmentofwhichfactorsthatpredictordeterminedisability(Guzmanetal.2007).ExistingresearchevidencehadlargelyfocusedonRTW.Amongthefactorswithahighimpactonoccupationalparticipationwerecareproviderreassurance(strongconsensus),expectationofrecoveryanddecreasedfears(moderateconsensus),andincreasedknowledgeoftheindividualwithbackpainandappropriatemedicalcare(lowconsensus).Ontheotherhand,therewasmajordisagreementastotheimpactofincreasedjobsatisfaction,decreasedpain,increasedfitness,improvedfunction,improvedworkstationdesign,decreasedphysicalworkload,andliftingdevices.

ManyoftheRTWstudieshavebeencarriedoutinNorthAmericawiththesettingbeingaworker’scompensationsystem.Therefore,ithasbeenclaimedthatthereisaneedforcomparativedatafromotherjuris-dictionswithdifferentinsuranceschemesandsocialpolicyframeworksincorporatingalternativelegislativeimperativesandeconomicincentives(Brookeretal.2001).Thisinformationcouldclarifytherelationship

betweensocietalfactorsandtheavailabilityandqualityofworkplace-basedRTWprograms.

ThebarriersofrecoveryandRTWwereinvestigatedamongemployeeswithwork-relatedUED(Shawetal.2003a).Casemanagersidentifiedupto21barrierspercasewithinfivedomains:signsandsymptoms(36 %ofallbarriers),workenvironment(27 %),medicalcare(13 %),functionallimitations(12 %),andcopingoftheemployee(12 %).

Ina2-yearprospectivecohortstudyamongpatientswithbackpaininprimarycaresettings,theoutcomemeasurewas"RTWingoodhealth"at2yearscombiningpatient'soccupationalstatus,functionallimitationsandrecurrencesofworkabsence(Dionneetal.2005).Thebestpredictivemodelincludedsevenbaselinevariables,suchasthepa-tient'srecoveryexpectations,previousbacksurgery,painintensity,anddifficultyinsleeping.Thismodelwasparticularlyefficientatidentifyingthosepatientswithnowork-relatedfunctionalproblems.

3.4.1. Worker perceptions and expectations

Asystematicreview(Kuijeretal.2006)gatheredevidenceforpredictorsofthedecisiontoreturntowork("RTWthreshold").Consistentevidencewasfoundforownexpectationsofrecoveryinthatpatientswithhigherexpectationsofrecoveryhadlesssicknessabsencedaysatthemomentoffollow-upmeasurement.

TheimportanceofpsychosocialfactorsonRTWwasstudiedinasystematicreview(Ilesetal.2008)whichevaluated24studies.Thesestudiesproducedstrongevidencethatrecoveryexpectationandmoderateevidencethatfear-avoidancebeliefswouldbepredictiveofworkoutcomeinnon-chronic,non-specificLBP.Workers'ownbeliefsthattheirLBPwascausedbyworkandtheirownexpectationsabouttheirinabilitytoreturntoworkwereclaimedtobeparticularlyimportant(Waddelletal.2001).

Non-medicalfactors,especiallythoserelatedtoworkplaceconcerns,perceptionsofinjuryseverity,andexpectationsforrecovery,wereassoci-atedwithbackdisabilitydurationinaninceptioncohortstudy(Shawetal.2005).Patients(183female,385male)sufferingarecentonsetLBPcompletedaquestionnaire,andaftertheinitialvisittheclinicianscom-pletedanadditionalquestionnaire.Functionallimitationandworkstatuswereassessedonemonthafterthepainonset.Accordingtotheresultsof

thatstudy,psychosocialfactorsseemedtomoderatethedisablingeffectsofpain,evenwithinthefirstweeksafterpainonset.Accordingtotheavailableevidence,subjectiveinterpretationsandappraisalsofpatientswouldbemorepowerfulpredictorsofpostbackinjuryrecoverythanphysicalexaminationvariables(Shawetal.2005).

Individuals'subjectiveperceptionsofpersonalandenvironmentalissuesinfluenceRTW.Itwasstatedthatthepersonalmeaningofdisabil-ityandRTWrelevancywouldbetwokeyconstructsinunderstandingRTWfromtheindividual'sperspective(Shawetal.2002a).Throughouttheexperienceofbecomingbetterandreturningtowork,theworkersassessedtheimpactofpersonalandexternalfactorsthatcontributedtotheirworkdisability.Theyalsoevaluatedtheirperformancecapabilities,andexaminedtheimportanceofworkandtheconsequencesofworkdisabilitywithintheirlifecircumstances.

Basedontheoriesoffearandavoidancebehaviour,Waddelletal.pos-tulatedthatpatients'beliefsabouthowphysicalactivityandworkaffecttheirLBParestronglyrelatedtosicknessabsenceduetoLBP(Waddelletal.1993).Inamorerecentlongitudinalstudythebeliefsaboutbackpainwerestudiedinrelationtorecoveryrateover52consecutiveweeks(Elferingetal.2009).Higherlevelsofwork-relatedfear-avoidancebeliefs(i.e.,beliefsregardingtheinevitableconsequencesofLBPinthefuture)predictedgreaterweeklyLBPandimpairment.Fasterrecoveryandpainreliefovertimewereseeninthosewhoreportedlesswork-relatedfearavoidanceandfewernegativebackbeliefs.

Inastudyofpatientswithoperativelytreatedhanddisordersorinjuries(Opsteeghetal.2009),threefactors,i.e.higherpainintensity,accidentattributedtoworkandsymptomsofpost-traumaticstress,werethemostimportantdeterminantsofdelayedRTW.Inanotherprospec-tivecohortstudy(Baldwinetal.2007),baselinephysicalfunctioningandoverallmentalandphysicalhealthstatusweremorepredictiveofspecificpatternsofpost-injuryemploymentthanpainintensitymeasures.

3.4.2. Work environment and work organisation

PsychosocialandphysicalworkenvironmentriskfactorswereexaminedaspredictorsofRTWinaDanishprospectivestudy(Labriolaetal.2006).Contrarytopreviousstudies,nosignificantassociationwasfound

betweenworkplacesizeandthethreeRTWoutcomes(RTWwithinfourweeks/oneyearoftheonsetofsicknessabsenceanddurationofsicknessabsence).Lowmeaningofwork,stoopingortwistingtheback,liftingheavyloadsandrepetitivejobtaskssignificantlydecreasedthechanceofRTWwithinfourweeksoftheonsetofsicknessabsence.ThechanceofRTWafteroneyearofsicknessabsencewasdecreasedbybeingexposedtoastoopedworkpositionandhavingtodorepetitivejobtasks.Thedurationofsicknessabsencewasprolongedbylowskilldiscretion,lowmeaningofwork,liftingheavyloadsatwork,andpushingandpulling.

ModifieddutyandworkplaceaccommodationshavebeenshowntopreventprolongedworkabsencesforworkerswithMSDbydecreasingexposuretonormalworkdemandsaftermedicalevaluationandtreat-ment.Thiswasthemainfindingofareviewonthebasisof13highqualitystudies(Krauseetal.1998).Injuredworkerswhowereofferedmodifiedworkreturnedtoworkabouttwiceasoftenasthosewhowerenotgiventhisoption.

Alaterreportstrengthenedtheevidencethatworkplaceoffersofarrangementstohelptheworkerreturntoworkareassociatedwithreducedcompensationbenefitduration(Brookeretal.2001).Theaccommodationcouldbeachievedinseveralways,i.e.modifiedoralternatetasks,gradedworkexposure,worktrials,workstationredesign,activityrestrictions,reducedhours,orothereffortstotemporarilyreducephysicalworkdemands.Akeyconcernfromtheworker'sperspectiveisthatmodifiedworkarrangementsprovideasafeworkplaceenvironmentthatfacilitatesrecoveryfrominjuryratherthanexacerbatingit.Itwasreportedthatanyinterventionthatreducesabsencefromregularworkwaslikelytoreducelong-termchronicity,withallofitspersonalandfinancialcosts(Loiseletal.1997).

TheroleofasupervisorisvitalforthesuccessfulRTWofanemployee.Accordingtotheexistingevidence,theinterpersonalaspectsofsupervi-sionmaybeasimportantasphysicalworkaccommodationtofacilitateRTWafterinjury(Shawetal.2003b).Asystematicreviewofthequalita-tiveliteratureonreturntoworkafterinjuryhasbeenpublishedinordertobetterunderstandthedimensions,processes,andpracticesofRTW(MacEachenetal.2006).Thatreviewnotedtherelevanceofrecognisingthecomplexitiesrelatedtobeliefs,rolesandperceptionsofthemanyplayers.Goodwillandtrustwerethecrucialconditionsthatwerecentral

tosuccessfulRTWarrangements.Inaddition,itwasobservedthatthereareoftensocialandcommunicationbarrierstoRTWandintermediaryplayershavethepotentialtoplayakeyroleinfacilitatingtheprocess.

Ithasbeenclaimedthatthemosteffectiveapproachestodisabilitypreventionarethosethatmaintainanopenandeffectivecommunica-tionamongworkers,physicians,andemployersinordertofacilitateasmoothandbroadlysupportedreintegrationintotheworkplace(Shawetal.2005).Thus,employerswhoprovideasupportiveandaccommodat-ingapproachtodisabilitymanagementmaynotbeabletoonlyreducedisabilitycostsbutalsoimproveworkerperceptionsoftheirfunctionalhealthaftertheinjury.

Inastudyofcasemanagementserviceforwork-relatedUED(Shawetal.2004),thetypesofaccommodationsobtainedbycasemanag-ersappearedtoberelativelyinexpensiveandincludedafullrangeofenvironmental,equipment,andadministrativechanges.Theseaccom-modationswereconsistentwithreducingupperextremitypain,eitherdirectlybyaddressingworkstationdesign(forexample,keyboard,deskedges)orindirectlybyalteringtheworkprocess(forexample,breaks,jobrotation).Inanotherreportfromthesamestudy(Lincolnetal.2002),theaccommodationswereclassifiedintothefollowingeightgeneralcategories:administrative,computer-related,furnishing,workstationlayout,environmental,accessories,lifting/carryingaids,andpersonalprotectiveequipment.

Beingcontactedbysomeonefromtheworkplacewasnotassociatedwithareductionintimereceivingcompensationbenefits(Brookeretal.2001).Itislikelythatmerelycontactingtheworkerintheabsenceofotherinterventionsisnotassociatedwithafasterreturntowork.Al-ternatively,perhapsthenatureofthecontactthatoccurredduringthestudywasnotconducivetofacilitatingafasterreturntowork.Althoughworkerswhowereofferedmodifiedworktendedtoreceivecompensationbenefitsforashortertime,theydidnotseemtohavereducedpainscores(Brookeretal.2001).Infact,asmallminorityofworkersexperiencedsubstantiallymorepainthanexpectedwhentheyresumedtheirwork.Theauthorsofthatreportrecommendedthatworkerandworkplaceas-sessmentsbeforeandafterthereturnoftheworkertoworkmayhelptoensurethatemployeesarenotreturnedtoworktooearlyortoworkplacesituationsthatreactivatetheirpain.

3.4.3. Role of the medical provider

TreatmentstudiesonacuteLBPhavereportedone-monthRTWratesfrom70to90 %dependingonrecruitmentproceduresandinitialriskfactors.Thisratehasshownremarkableconsistencydespitejurisdictionaldifferencesinemploymentanddisabilitybenefits(Shawetal.2005).AhighrateofRTWshouldnotbeinterpretedasacompleteresolutionofpain,sincemostemployeescontinuesufferingfrompainandrelatedproductivitylossatwork(Shawetal.2009a).

Accordingtotheresultsofaliteraturereview(Hlobiletal.2005),theoptimalRTWinterventionforsubacuteLBPmightbeamixtureofexercise,education,behaviouraltreatment,andergonomicmeasures,butitwasnotclearwhichcomponent,orwhichcombinationofcom-ponents,wasthemosteffective.ThesamereviewconcludedthatRTWinterventionsusedintheearlier,acutephaseofLBPdidnotappeartobeeffectivewithrespecttoabsencefromwork.Thismaybebecauseofthefavourable,self-limitingcourseofLBPandabsencefromworkdur-ingthisacutephase.

Apopulation-basedRCTonbackpainmanagement(Loiseletal.1997)concludedthatchangestojobsandworkstationsusingpartici-patoryergonomicapproachwerepreferabletoworker-focusedstrate-giessuchasworkhardening(alternatingdaysattheoriginaljobwithprogressivelyincreasedtasksanddaysreceivingfunctionaltherapy).Inthatstudy,anintegratedclinical-occupationalmodelofmanagementofbackpainwastwotimesmoreeffectiveinincreasingtherateofreturntoregularworkthantheusualmedicalcare.

ThereisalsomoderateevidencethatthepresenceofaRTWcoordi-natorwouldbeassociatedwithasignificantreductionofworkdisabilityduration(Francheetal.2005).SixpreliminarycompetencydomainsofRTWcoordinatoractivitieshavebeenidentified(Shawetal.2008):(1)ergonomicandworkplaceassessment;(2)clinicalinterviewing;(3)socialproblemsolving;(4)workplacemediation;(5)knowledgeofbusinessandlegalissues;and(6)knowledgeofmedicalconditions.

Professionalcasemanagersmaybethesolutiontomanyofthecom-municationproblemsinvolvedindisabilitymanagement.Theseindi-vidualscouldidentifybarrierstoRTW,restorenormalcommunicationbetweenemployerandemployees,andengagethemedicalproviderinthis

process(Pranskyetal.2004).Thenursecasemanagermaysuccessfullylegitimisethepatient’sviewpointandthusinitiateabidirectionaldialogueaboutRTWdirectlywiththeemployer.Thus,itwasclaimedthatitwasthisrestorationofcommunicationmorethananyotherinterventionthatmayhaveaccountedforthesuccessesofthismodel.However,aspatientsarenotaccustomedtocommunicatetheirconcerns,preferences,andexpectations,patienttrainingwouldbedesirabletoachievefullyeffectivebidirectionalinterchange(Pranskyetal.2004).

ParticipatoryergonomicshasbeenseenasonepromisingapproachtorehabilitationofworkerssufferingfromMSD.Loiseletal.havedescribedaprogramwithfoursteps(Loiseletal.2001):First,theergonomistmeetstheworkertocollectdataonpersonalcharacteristics.Jobdescriptionsaresoughtfromboththeworkerandhis/hersupervisor.Secondly,ameet-ingisorganisedintheworkplacewiththeworkerandthesupervisortocomparethejobdescriptions,makealistoftheriskfactorsforbackpain,andtoidentifyworkorganisationandjobdemandsrelevanttothebackpain.Thirdly,theergonomistvisitstheworkplacetoobservetheworktasksperformedbyanotherworker.Finally,theparticipatoryworkgroupmeetstoidentifyimprovementsintheworktasks.Finalacceptanceofthesesolutionsistheemployer'sresponsibility.

ErgonomicjobmodificationasacomponentofaRTWrehabilita-tionprogramisgenerallybelievedtohavepositiveeffectswithworkershavingsicknessabsenceduetobackpain(Silversteinetal.2004).Ithasbeenshown,however,thatdoctor-patientcommunicationsabouttheworkplaceandRTWareimportant,butnotsufficientintheabsenceofergonomicandorganisationalchangesintheworkplace(Dasingeretal.2001;vanDuijnetal.2005).Therefore,RTWcoordinatorsaspartofhealthserviceshavebeenclaimedtorepresentaneffectivestrategyforpromotingRTW.Accordingtoaliteraturereview(Shawetal.2008),theprincipalactivitiesofRTWcoordinationinvolveworkplaceassess-ment,planningfortransitionalduty,andfacilitatingcommunicationandagreementamongstakeholders.

InordertopromoterecoveryandearlyRTW,part-timesicknessabsenceispossibleinsomecountries(forexample,Finland,Sweden,Norway,andDenmark).However,theeffectivenessofpart-timesickleavehasbeenpoorlystudied(Kaustoetal.2008).ANorwegiancluster-randomisedstudyon"activesickleave"(returntoadjustedworksup-

portedbysocialsecurityafterconventionalsickleavehadlasted16daysormore)showednobeneficialeffects,partlybecausethepart-timesickleavesystemwassoseldomused(Scheeletal.2002).

Almostallindividualstakingpart-timesickleavedoseemtobecon-tentwiththisarrangement;92 %ofemployeesonpart-timesickleaveinaSwedishsurveyexpressedsatisfaction(Sieurinetal.2007).Two–thirdsofthoseonfull-timesickleaveconsideredpart-timesickleaveasapotentiallygoodalternativeforthem.However,somedisadvantageshavealsobeendetected:aSwedishstudywithafollow-upof1.5yearsfoundthatpart-timesickleavestendedtolastlongerthanconventionalsickleaves(Eklundetal.2004).

4. CONCEPTUAL fRAMEWORK Of ThE STUDY

Theconceptualframeworkforthestudyispresentedinfigure4.Ahealthyemployeemightdevelopsymptomsordisordersduringem-ployment(stepA).Inacaseofsymptomdevelopment,theconditioneitherallowstheemployeetocontinueworkingoralternativelytheemployeemaybeabsentfromwork(stepB).Whileatworkwiththedisorder,theemployeemayhavefullcapacitytoperformworkdutiesorhe/shemightexperienceimpairedfunctioningtosuchadegreethatproductivityatworkisreduced(stepC).Thosewhobecomesick-listedeitherreturntoworkortheirdisabilitybecomesprolonged,evenpermanent(stepD).ThisthesisaimstostudythesefourstepsusingMSDasanexample.

4CONCEpTuALfRAMEWORKOfTHESTuDY

STEP B

STEP A STEP C

Healthyemployee

No symptoms or MSD

At workNormal

productivity

reduced productivity

Symptoms or/and MSD

On sick leave

return to work

Prolonged or permanent disability

rCT on effects of part-versus full-time sick leave on

(Study V)

Productivity loss due to uED and effects of a workplace intervention?

(Studies iii, iV)

impact of disease and workplace

characteristics on work ability?

(Study ii)

Prevention of LBP caused by

exposure to lifting at work?

(Study i)

Primary prevention

Secondary prevention

Tertiary prevention

STEP D

FigurE 4. Theoretical framework of the study and the research questions

Step A

Thereisawealthofreportsinthemedicalliteratureonthehealthrisksthatworkcanposetoanemployee.Theaimofoccupationalsafetyleg-islationistosafeguardthehealthandsafetyoftheemployeesthroughriskidentification,eliminationofrisk,ormanagementoftheresidualrisk,iftheriskcannotbefullyeliminated.

Healthproblemsinworkingageadults,however,arenotfullypre-ventable.Thereisahighbackgroundprevalenceofmusculoskeletalsymptomseveninthegeneralpopulation,andworkcanhavearoleasanadditionalriskfactorforMSD(Waddelletal.2006).AccordingtothegeneralprinciplesofpreventionintheEUframeworkdirectiveonhealthandsafetyatwork(89/391),combatingtherisksatsourceandadaptingtheworktotheindividualshouldalwaysbegivenpriorityoverindividualprotectivemeasuresandinstructionstotheworkers.

Step B

ThedisordermaycauseimpairmentintheactivityandparticipationdomainsoftheICFmodel.Atwork,thistypicallymeansthattheem-ployeecannotcontinueworking,butinsteadremainsabsentfromwork.Contextualfactorsseemtoplayamajorroleinthisprocess(Johanssonetal.2004;Shawetal.2009b).Ithasbeenshownthat(long-term)sicknessabsenceanddisabilityduetoMSDdependmoreonindividualandwork-relatedpsychosocialfactorsthanonbiomedicalfactorsorthephysicaldemandsatwork(Walker-Boneetal.2005).

Step C

SicknessabsenteeismasareflectionofdisablinghealthconditionisoneofthemajoroutcomesappliedinOHresearch.Duringthelastyears,however,moreattentionhasbeenpaidtotheimpactofhealthconditionsamongthoseemployeeswhocontinueatwork.Thefactthathealthproblemscauseinterferencewithworkhasbeenverifiedlately,andthetermsicknesspresenteeismhasbeenintroducedtoclarifythisphenomenon.

Step D

Absencefromworkisbeneficialfortherecoveryfromcertainillnesses.InMSDandmentaldisorders,however,itisobviousthatprolongedsicknessabsenceisamajorriskfactorforpermanentdisability.Again,thisislargelynotexplainedbymedicalgrounds,butpsychologicalandcontextualfactorsareessentialintheRTWprocess(Loiseletal.2005).

Inordertoavoidthenegativeconsequencesofprolongedsickleave,thedisabilityhastobemanagedseparatelyfromthemanagementofthemedicalconditionitself.Theriskfactorsand,hence,themeanstoenhanceRTWprocessaredifferentfromthoseoftheunderlyinghealthdisorder.

5. STUDY qUESTIONS AND hYPOThESES

1. Can the increased risk of LBP associated with heavy lifting at work be reduced by training the employees in correct lifting techniques or assistive devices? (StudyI)

BasedontheavailableevidenceonmanualmaterialhandlingasariskfactorforLBP,thehypothesisevaluatedinthissystematicreviewwasthat trainingcorrecttechniquesinliftingheavyloadsatworkand/orassistivedevicescouldreducetheriskofbackinjury(StepA).

2. What is the impact of disease and workplace characteristics on perceived work ability among employees seeking medical advice? (StudyII)

HowdoworkersvisitingtheirOHphysicianswithdifferentdiseases,andespeciallyMSD,assesstheircurrentworkability,andwhataretherelationshipsbetweentheworkers'perceptionsorexpectationsandself-assesseddisability?Thehypothesistestedwasthatperceivedpartialworkabilityandwork-relatednessofhealthproblemswouldbecommonandinterrelated(StepB).

3. How much productivity at work is impaired by medically verified UED?(StudyIII)

Productivitylosswhileatworkhasbeenshowntobecommonamongworkersreportingmusculoskeletalsymptoms.ThehypothesisforthissurveywasthatdiagnosedUEDwouldimpairworkperformanceeventhoughactualsickleavewouldnotbeneeded(StepC).

5STuDYquESTIONSANDHYpOTHESES

4. Can productivity loss at work be reduced by an ergonomic in-tervention?(StudyIV)

Thestudyhypothesiswasthatproductivitylossatworkcouldbeusedasanoutcomeindicatorininterventionstudiesand,duringrecoveryfromUED,anindividuallytailoredergonomicinterventioncouldreduceproductivitylosscomparedtousualmedicalcare(StepC).

5. How can the effectiveness of part-time sick leave be evaluated in the management of MSD?(StudyV)

ThehypothesiswasthatarandomisedcontrolledtrialcouldbedesignedandimplementedintheFinnishOHStoinvestigatetheeffectsofpart-timesickleaveonreturntofull-timework(StepD).

6. MATERIAL AND METhODS

6.1. Study populations

Inallindividualstudies,theparticipantswereworkingadults.Studiesincludedinthesystematicreview(studyI)wereperformedinhealthorhomecare(eightstudies)oramongbaggagehandlersorpostalworkers(threestudies).Thetotalnumberofparticipantsinthereviewwas18492.StudyIIincluded723employeesfromthechemicalindustryorpublicsector,whereas168to177employeesinstudiesIII–IVcamefromthehealthcareandcommercialsectors.

Therearesomedifferencesbetweenthestudieswithrespecttothehealthstatusofthestudypopulationsandtheuseofhealthservices(table5).Withtheexceptionofonestudy(II),inwhichpatientswereeligibleirrespectiveofanyhealthproblemsnecessitatingaconsultationwiththeOHphysician,allotherstudies(I,III–V)inthisthesisincludeonlysubjectswithMSD.

Table 5. Description of the included studies.

Type of study Population Study intervention

Main outcome

Study I

Systematic review Workers frequently exposed to heavy lifting

Lifting advice and/or devices

LBP and related sickness absence

Study II

Survey (questionnaire)

Workers seeking medical advice at OHS

- Self-assessed work ability, work-relatedness of the health problem

Study III

Survey (baseline assessment of rCT)

Workers with medically verified uED

- Self-assessed uED-related productivity loss at work

Study IV

rCT Workers with medically verified uED

Ergonomic advice and worksite visit

Self-assessed uED-related productivity loss at work

Study V

rCT(protocol)

Workers with medically verified MSD and in need of instant sick leave

Part-time sick leave

return to full-time work

6MATERIALANDMETHODS

Thesystematicreview(studyI)summarisingtheevidenceonthepre-ventiveeffectsoftrainingandliftingequipmentonbackpainincludedstudieswithemployeesexposedtoheavyliftingatworkwhowerenotactivelyseekingtreatmentforcurrentbackpain.

Thesurvey(studyII)includedeachemployeeduringthestudyperiodcomingfortheirfirstappointmentwithanOHphysicianbecauseofanyhealthproblem.StudiesIIIandIVfocusedonlyonemployeeswithsymp-tomsintheupperextremitiesandnoneedforsickleave,whereasstudyVincludesallworkerswithanyMSDnecessitatingsickleave.TheemployeeswereexcludediftheconditionnecessitatedmedicalcareinstudyI,sickleaveinstudiesIII–IV,orthepainintensityscorewassevenormoreonascalefromzerototeninstudyV;ifthedisorderwascausedbymajortrauma,infection,orauto-immunedisease;ifthedisorderwascomplicatedbyanysevereco-morbidityorcondition(malignancy,fibromyalgia,mentaldisorder,occupationalinjuryordisease,scheduledorpriorsurgery);orthefollow-upinstudiesIV–Vwouldhavebeencomplicatedbyotherfactors(retirement,pregnancy,orotherlongerleavefromwork).

6.2. Methods

Theincludedfivestudiesrepresentthreedifferenttypesofstudies:systematicreview,survey(cross-sectionalquestionnaireandbaselineassessment)andRCT(table5).

6.2.1. Systematic review (Study I)

Thecurrentinterestinevidence-basedmedicinehasledtoanextensiveincreaseinthepublicationofsystematicreviewsandtothedevelopmentofmethodologicalguidelinesforsystematicreviews,becauseasystematicapproachisknowntobelesssusceptibletobiasthananarrativeapproach(vanTulderetal.1997;vanTulderetal.2003).

Thissystematicreviewincludedallstudieswithinterventionsthatmodifytechniquesforhandlingheavyobjectsorpatientsmanually,ifthestudyusedbackpain,consequentdisability,orsickleaveasthemainoutcome.Interventionsthatwerepermittedincludededucationalclasses,individualtrainingandinstructions,posters,leaflets,videos,audiotapes,orcombinationsofseveralinterventions.Inordertofindall

6MATERIALANDMETHODS

relevantresearchreports,thesearchstrategydevelopedbytheCochranebackreviewgroupwasutilized(vanTulderetal.2003).TheprimarysearchfocusedonRCTswithasecondarysearchoncohortstudieswithaconcurrentcontrolgroup.

TheliteraturesearchwascarriedoutbetweenAugustandNovember2005.Searchstrategies,useddatabasesandthedetaileddescriptionofthereviewprocessaregivenintheCochraneLibraryversionofthereview(Martimoetal.2007).

Inordertomakeasecondaryanalysisusingrelevantcohortstudieswithaconcurrentcontrolgroup,thesensitivesearchstrategyforOHinterventionstudieswasapplied(Verbeeketal.2005).Twoauthorsscreenedtheobtainedtitlesandabstractsforeligibility.

ThemethodologicalqualityoftherandomisedtrialswasassessedusingthecriteriaandclassificationrecommendedbytheCochraneBackReviewGroup(vanTulderetal.2003).Thequalityofastudywasconsideredashighifmorethanhalfofthecriteriawerefulfilled.Fortheappraisalofcohortstudies,anothersetofcriteria(Slimetal.2003),validatedfornon-randomisedstudies,wereused.

Theprimaryanalysisofthereviewwasbasedontheevidencefromrandomisedtrialsonly.Inthesecondaryanalysisusingthecohortstud-ies,theresultsofeachcomparisonweresummarisedinaqualitativemanner.Thereafter,theconclusionswerecomparedfromtheprimaryandsecondaryanalyses.

6.2.2. Surveys (Studies II–III)

InstudyII,patientsattendingamedicalconsultationattwoOHcentres(oneinchemicalindustryandtheotherinpublicsectorinthecapitalarea)weregivenananonymousquestionnairebeforemeetingthephysician(N=12).Age,genderandoccupationwerecollectedtogetherwiththeresponsetoanopen-endedquestiononthenatureanddurationofthemaindiseaseorsymptomthatnecessitatedtheconsultation.Onlythefirstconsultationofeachpatientduringthestudyperiodwasincluded.

Patientassessedwork-ability(fullyorpartlyabletowork,disabled)andwork-relatednessofthehealthproblem("causedoraggravatedbywork"),andthepotentialofwork-relatedinterventionsinalleviatingthe

6MATERIALANDMETHODS

symptoms.Patientsweretoldthattheirphysicianswouldnotseetheirresponses.Thephysicianswereaskedtoanswerthesamequestionsim-mediatelyaftertheconsultation.Onlypatientswhogavethesamereasonforthevisitasindicatedbytheirphysicianwereincludedintheanalysis.

StudyIIIwasalsocarriedoutincollaborationwiththreeOHunits.Allsubjectsaged18to60yearswereconsideredaspotentiallyeligible,iftheywereseekingmedicaladviceintheoccupationalhealthservices(OHS)becauseofupperextremitysymptomsthathadstartedorwereexacerbatedlessthan30dayspriortothemedicalconsultation('earlysymptoms').WithinthreedaysafterseekingmedicaladviceintheOHS,thesubjectwasexaminedattheFinnishInstituteofOccupationalHealth(FIOH)byaphysician,whodidnotparticipateinanalysingthedata.Theclinicaldiagnosiswasmadebyapplyingstandardizeddiagnosticcriteriaforeachsymptomentity(Sluiteretal.2001).

TheoutcomeofstudyIIIwasself-assessedproductivitylossatwork.ItwasassessedwithtwoquestionsabouttheimpactofUEDonworkperformance(QQmethod)duringtheprecedingfullworkday(Brouweretal.1999).Thefirstquestionwas:'Assesstheimpactofyourupperextremitysymptomsandmarkonascalefrom0("practicallynothing")to10("regularquantity")howmuchworkyouwereabletoperformascomparedtoyournormalworkday'.Thesecondquestionwas:'Assesstheimpactofyourupperextremitysymptomsandmarkonascalefrom0("verypoorquality")to10("regularquality")thequalityofyourworkascomparedtoyournormalworkday'.ThetranslationofthequestionsintoFinnishwasmadebasedontheoriginalDutchversionanditsEng-lishtranslationadheringtotheirwordingandstyleascloselyaspossible.ThevalidityoftheoriginalQQmethodhasbeenstudiedincomparisonwithothermeasurements(Brouweretal.1999;Meerdingetal.2005).Self-reportedproductivityonthismethodhasbeenshowntocorrelatewellwithobjectiveworkoutput(Meerdingetal.2005).

Adichotomousvariableforproductivityloss(yes/no)wasformedsothatthosewhoscoredavalue0–9ineitherofthetwoquestionswereclassifiedas'reportingproductivityloss',andwerecomparedtothosewhoscored10inbothquestions.Themagnitudeofproductivityloss(i.e.,howmuchproductivitywasreduced)wascalculatedusingtheformula[1–(quality/10)x(quantity/10)]x100 %,modifiedfromanearlierstudy(Hoeijenbosetal.2005).

6MATERIALANDMETHODS

ThesubjectwasaskedtoratetheintensityofpaincausedbyUEDonascalefrom0to10(0correspondingto"nopain"and10to"theworstpossiblepain")andpaininterferencewithwork,leisuretimeandsleepduringthelastsevendays(from0,"nointerferenceatall",to10,"theworstpossibleinterference").SickleavesduetoUEDduringthepreceding12monthswerealsoinquired.

Fortheassessmentofphysicalexposuresatwork,theOHphysicianinterviewedthesubjectaboutthefrequencyofliftingloadsweighing5kgormore;workingwithhand(s)abovetheshoulderlevel;andwhetherworktasksrequiredfrequentorsustainedelevationsofthearms.Work-ingatakeyboard,prolongedforcefulgripping,aswellaspinchgripthateitherrequiredforcefulexertionordeviatedwristposture,werealsoinquired.Eachfactorwasdichotomizedusingacut-offofbeingexposedfor10 %oftheworktimeduringtheworkday.

JobstrainwasmeasuredwiththeJobContentQuestionnaire(Karaseketal.1998).Smokinghabitsandleisurephysicalactivitywereinquired,andwaistcircumferencewasmeasured.Fear-avoidancebeliefswereas-sessedusingfouritemsadaptedfromWaddelletal:"Physicalactivitymakesmysymptomsworse","Ifmysymptomsbecomeworse,itmeansthatIshouldstopwhatIwasdoing","Mypainiscausedbywork",and"Ishouldnotcontinueinmypresentjobbecauseofthesymptoms"(Waddelletal.1993;Estlander2003).

6.2.3. Randomised controlled trials (Studies Iv–v)

InstudyIV,theeffectivenessofaworkplacerelatedinterventionwasstudiedusingself-assessedproductivitylosscausedbyUEDasthemainoutcome.InformationfromstudyIIIservedasbaselinefortheinter-vention,andthefollow-uptimewas12weeks.Randomizationintointerventionandcontrolgroupswasperformedbythephysicianusingtablesofrandomnumbersinthreeblocks(symptomsinwristorforearm,elbow,orshoulder)andsealedenvelopes.Basedonpowercalculations,thetargetwastoinclude500subjectsinthestudy.

Allsubjectsreceivedthebestcurrentpracticetreatment(Varonenetal.2007).Thesupervisorsoftheemployeesintheinterventiongroupwerecontactedbyphonebythephysiciantodiscusspotentialaccom-modationsatwork.Afewdaysaftertheclinicalexamination,anoccu-

6MATERIALANDMETHODS

pationalphysiotherapistvisitedtheworkplace.TheaimoftheworksitevisitwastoinvestigateergonomicimprovementsthatwereconsideredbeneficialfortherecoveryfromtheUED.Theassessmentincludedthephysicalworkenvironmentandtheavailabletoolsorinstruments,work-ingpostures,forcerequirements,workpaceandbreaksduringwork,aswellasassessingtheemployee'spossibilitiestocontinueworking.Theproposalswerediscussedtogetherwiththeemployeeandthesupervisorwhothenmadethefinaldecisiononthetechnicalandadministrativechangesrequiredtomodifytheworkload.

Theprimaryoutcomemeasurewasself-assessedproductivitylossatwork,asdescribedinstudyIII,measuredatbaseline,eightweeksand12weeks.Inaddition,theemployeeswereinquiredaboutthenumbersofsickleaveepisodesduetoanyreason,andexclusivelyduetoUED,dur-ingfollow-up.Thecontentsoftheergonomicinterventionsasreportedbythephysiotherapistsduringtheworkplacevisitswerealsoanalysed.

Theprotocolofthesecondinterventionstudy(studyV)aimstoassessthehealtheffectsofearlypart-timesickleavecomparedtoconventionalfull-daysickleave.Thisprotocolwasdesignedbasedontheresultsofpreviouslypublishedstudiesonpart-timesickleave(Kaustoetal.2008).Thefeasibilityofthestudydesignwasdiscussedandmodifiedwiththerepresentativesfromtheparticipatingworkplaces.PriortotheRCT,theprotocolandthequestionnairesweretestedbyoneOHSunitinapilotstudybasedonvoluntaryparticipationofsomeemployeesinpart-timesickleave.ThefinalprotocolwasapprovedbytheCoordinatingEthicsCommitteeofHospitalDistrictofHelsinkiandUusimaa.

ThisstudyVison-goingandthereforeonlytheprotocolisdescribedinthisthesis.InthosepatientswithMSDseekingmedicaladviceandfulfillinginclusioncriteria,theOHphysicianinvitesthesubjectsintothestudy.Thephysicianalsoinformstheemployeeaboutthestudyanditsaims,andiftheemployeeagreestoparticipate,informedconsentwillbesigned.Thisincludesapermissiontocontactthesupervisor,preferablyduringthepatient’svisit,inordertoinvestigatewhetherwork-relatedarrangementsforpart-timesickleavewouldbefeasible,inthecasethattheemployeeisallocatedtotheinterventiongroup.Ifthesupervisordisagrees,thentheworkerwillbeexcludedfromthetrial.

Oncetheagreementsfromtheemployeeandthesupervisorareobtainedandbeforetherandomisation,thephysiciandeterminesthe

6MATERIALANDMETHODS

lengthofthesicknessabsencebasedonsymptoms,clinicalfindingsandbackgroundinformation.Subsequently,iftheemployeeisallocatedtopart-timesickleave(interventiongroup),dailyworkloadwillbereducedbylimitingtheworkingtime.Also,ifnecessary,remainingworktaskscouldbemodifiedsothatworkingispossibledespitethepresenceofsymptoms.Inthecontrolgroup,workloadiseliminatedbyfull-timesickleave.Bothgroupsreceiveappropriatemedicaladvice,andtheneedformedicaltreatmentsandacontrolvisitaredeterminedasusual.

6.3. Statistical analyses

6.3.1. Systematic review (Study I)

Fortheeligiblestudiesthatdidnotadjustforclusterrandomisation,thedesigneffectwascalculatedbasedonafairlylargeassumedintraclustercorrelationof0.10(Campbelletal.2001),followingthemethodsdefinedintheCochranehandbook(Deeksetal.2005).Thelengthoffollow-upwascategorizedasshortterm(lessthanthreemonths),intermediate(threeto12months)orlongterm(morethan12months).Thisclas-sificationisusedforthedescriptionoftheresults.

Forcomparisonswithdichotomousoutcomesandsufficientdata,theadjustedresultsofeachtrialwereplottedasoddsratios(ORs).Forcomparisonswithsimilarinterventionsbutwithbothdichotomousandcontinuousoutcomemeasurements,aneffectsizewascalculatedbasedonthelogarithmoftheORforstudieswithdichotomousoutcomes,andonthestandardisedmeandifferenceforstudieswithcontinuousoutcomes(Chinn2000).TheORsofstudieswerecombinedthatcomparedsimilarinterventionsandhavingmeasuredbackpainorbackinjurywithasimilarfollow-uptime.Theeffectsizesofstudieswithsimilarinterventionsthatmeasuredsicknessabsencerateordisabilityscoreatasimilarfollow-uptimewerecombinedbyusingthegenericinversevariancemethodusingthesoftwareasimplementedinRevMan4.2.forbothmeta-analyses.

6.3.2. Surveys (Study II–III)

InstudyII,factorsassociatedwithself-assessedworkabilitywerestudiedinamultinomiallogisticregressionmodel(SPSS®Programme,version

6MATERIALANDMETHODS

12.0.1).Theoutcomevariablewasworkabilityinthreelevels('able','par-tiallyable',and'unable').Theexplanatoryvariablesweregender,agegroup,occupationalstatus,OHcentre,durationofsymptoms,diseasegroup,work-relatednessofdiseaseandpotentialofwork-relatedinterventions.

LogisticregressionmodelswereusedinstudyIIItostudythedeter-minantsofproductivityloss.TheresultsarepresentedwithORswith95 %confidenceintervals(95 %CI).Multivariablemodelsincludedage,genderandthosevariablesassociatedwithproductivitylosswithaP-value<0.20inthegender-adjustedorage-andgender-adjustedmodels.Duetothecollinearityofpainintensityandpaininterference,nomutualadjustmentwasperformed,whereastheireffectswereassessedinseparatemodelsadjustedfortheothercovariates.Inadditiontotheseparateeffectsofpainintensity,excessivejobstrainandphysicalloadfactorsonproductivityloss,theirjointeffectswerealsoestimated,sinceitwashypothesizedthatthesevariablescouldactsynergistically.Multi-plicativeinteractionswerealsotestedbyincludinginteractionproductsinthemultivariablemodel.Thepossibleeffectmodificationbyagewasalsoinvestigatedwithstratifiedanalysesusingmedianage(45years)ascut-off.STATA,version8.2,softwarewasusedfortheanalyses.

6.3.3. Randomised controlled trials (Studies Iv–v)

DatainstudyIVwereanalysedaccordingtotheintention-to-treatprinciple.Missingdataonproductivityat12weeks(7inthecontrolgroupand8intheinterventiongroup)weresubstitutedwiththevalueat8weeks.Threeoutcomeswereused:proportionofproductivityloss(dichotomized),magnitudeofproductivityloss(continuous)andchangeinmagnitudeofproductivitylossfrombaseline(continuous).At8and12weeks,thetestfordifferences(two-tailed,P<0.05)waschi-squaredtestfortheproportionandtwo-samplet-testformagnitudeandchange.Generalizedestimatingequation(GEE)wasappliedtoanalyserepeatedmeasuresdata(Hanleyetal.2003).Thelinkfunctionwasspecifiedas"logit"forthedichotomizedoutcome.Inadditiontotheallocationgroupandfollow-uptime,age(continuous),gender,exposuretophysicalworkloadfactors(liftingloads>5kg,armelevationsatoraboveshoulderlevel,orforcefulorpinchgrip)andfear-avoidancebeliefs(continuous)wereincludedascovariatesinthemodels.

6MATERIALANDMETHODS

Itwasalsointendedtoidentifysomemodifiablesubgroupvariablesthatcouldaffecttheeffectivenessoftheintervention.Subgroupanalyseswereperformedbyusingthefollowingvariables:jobdemand,jobcontrol,fear–avoidancebeliefs(alldichotomizedusingthemedian),exposuretophysicalworkloadfactors,andpriorsicknessabsenceduetoUED.Totakeintoaccountthedifferenceinthemagnitudeofproductivitylossbetweentheinterventionandcontrolgroupatbaseline,thechangesinproductivitylossduringthefollow-upwereutilizedinthesub-groupanalyses.STATA,version10,software(StataCorpLP,CollegeStation,TX,USA)wasusedfortheanalyses.

InstudyV,asurvivalanalysiswillbeusedtostudythetimetoRTWintheinterventionandcontrolgroup.Theamountofsickleavedayswillbeanalysedat12and24months,andtheassociationsbetweentheoutcomesandbackgroundvariableswillbeanalysedusinggenerallinearmodels.Inaddition,thechangeinsymptomsanddisabilityindiceswillbestudiedatvarioustimepointsusinggenerallinearmodelsforrepeatedmeasurements.

Thecostsandbenefitstotheemployee,employerandsocietywillbeestimatedinbothstudygroups.CostsduetolostworkingtimewillbeanalysedseparatelytakingintoaccountthecompensationfromtheSocialInsuranceInstitutiontotheemployerduringfull-orpart-timesickleave.Dataoncostsoftheusedhealthservices,medications,andmedicalaids(duetothemainhealthproblem)willalsobecollected.Inaddition,theanalysiswillincludethecompensationofthelostworkinputusingstand-ins(salary,trainingtime)orovertime(performedbythecolleaguesofthestudysubjects),aswellasthetimethesupervisorusedtoaccommodatethenewworkarrangements.Allanalyseswillbemadebasedonanintention-to-treatprinciple.

Thenon-monetarybenefitswillbestudiedbasedonself-assessedpro-ductivityatwork(Brouweretal.1999),aswellasthereductionofpainanddisabilitymeasuredonascalefrom0to10.Ifthereisadifferencebetweenthegroupsintheoutcomemeasurements,acost-effectivenessanalysiswillbeundertakendividingthecostsbytheunitsofdifferenceintheoutcome.Ifthereisnosignificantdifferencebetweenthestudygroupsinanyofthehealthrelatedoutcomes,theanalysisoftotalcostsinbothgroupswillbeappliedindrawingthefinalconclusions.

7. RESULTS

7.1. Training and lifting devices for preventing back pain (Study I)

Altogether,3547titleswerefoundastheresultoftheprimarysearchstrategyinninedatabases.Thesensitivesearchstrategyprovided47additionaltitles.Another17referenceswerefoundinamanualsearch.Thusfromthetotalof3611articles,101wereselectedforcloserevalua-tion.Eighty-ninearticlesdidnotmeettheinclusioncriteria.Twoarticles(Fanelloetal.1999;Fanelloetal.2002)reportedonthesamestudy.Consequently,11studieswereincludedinthereview.

Fouroftheincludedstudieswereclusterrandomised(Daltroyetal.1997;vanPoppeletal.1998;Yassietal.2001;Krausetal.2002),twowereindividuallyrandomised(Reddelletal.1992;Mülleretal.2001),andfivewerecohortstudies(Dehlinetal.1981;Feldsteinetal.1993;Best1997;Fanelloetal.1999;Hartvigsenetal.2005).Two(Daltroyetal.1997;vanPoppeletal.1998)randomisedtrialsandallcohortstudieswerelabelledashighquality.Thecharacteristicsoftheincludedstudiesaredescribedintable6.

Inthreerandomisedtrials(Mülleretal.2001;Yassietal.2001;Krausetal.2002)andallfivecohortstudies,manualhandlingwasrelatedtopatientcare.Postalworkerswerestudiedinone(Daltroyetal.1997),andbaggagehandlersintwo(Reddelletal.1992;vanPoppeletal.1998)trials.Inallofthejobsstudied,theparticipantswereexertingsufficientstrainonthebackleavingampleroomforalleviationbyeffectiveinter-ventions.Thenumberofparticipantsinrandomisedtrialsvariedfrom51to12,772,andthefollow-uptimefrom6monthsto5.5years.Thecohortstudiesincluded45to345participants,andthefollow-uptimesvariedfrom8weeksto2years.

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Thetraininginterventionsfocusedonliftingtechniques,andtheirdura-tionvariedfromasinglesessiontoonceaweektrainingforaperiodoftwoyears(Table7).Inthreestudies,thetrainingwassupportedbyfollow-upandfeedbackattheworkplace.Theadvocatedliftingtechniqueswerenotdescribedindetail.Theinvolvementofsupervisorswasclearlyindicatedinthreestudies,andtheencouragementtouseavailableliftingaidswasstatedinfivestudies.Aprofessionalinstructorwasusedinmoststudies.

Compliancewiththeinstructionsandwiththeuseofassistivede-viceswasmonitoredinfivestudies(Feldsteinetal.1993;Best1997;vanPoppeletal.1998;Yassietal.2001;Hartvigsenetal.2005).Threestudiesreportedpositivechangesinliftingtechniquesinthreestudiesandthereweremarginalornochangesintwostudies.Inaddition,onestudy(Daltroyetal.1993)hasreportedseparatelythattheinterventionresultedinincreasedknowledgebutnotinanysignificantimprovementofmanualhandlingbehaviour.

Comparisonbetweengroupsreceivingtrainingornointerventionintworandomisedtrials(vanPoppeletal.1998;Yassietal.2001)in-dicatedthattherewasnodifferenceintheamountofbackpain(OR0.99,95 %CI0.54to1.81)orrelateddisability(effectsize0.04,95 %CI–0.50to0.58)atintermediatefollow-up.Thesameresultwasob-tainedinanotherrandomisedtrial(Reddelletal.1992),whichwasnotincludedinthemeta-analysisbecauseinsufficientdatawerereported.Onerandomisedtrial(Krausetal.2002)showednoeffectinbackpainatlong-termfollow-up(OR1.07,95 %CI0.06to17.96).Theresultsofthreecohortstudiessupportedthoseoftherandomisedstudiesatshort-term(Dehlinetal.1981;Feldsteinetal.1993)andlong-termfollow-up(Fanelloetal.1999).

Trainingcomparedtominoradvice(video)inonerandomisedtrial(Daltroyetal.1997)didnotshowaneffectonbackpainatlong-termfollow-up(OR1.08,95 %CI0.56to2.08).Thisconclusionwassup-portedbytheresultsoftwocohortstudies(Best1997;Hartvigsenetal.2005)usingin-houseorientationorlessextensivetrainingasthecontrolinterventions.

Comparisonoftrainingandlumbarsupportusedidnotyieldasignificantdifferenceinbackpainatintermediatefollow-upaccordingtoonerandomisedtrial(Reddelletal.1992).Anotherrandomisedtrial(Krausetal.2002)cametoasimilarconclusionwithrespecttolong-termfollow-up(OR1.04,95 %CI0.06to17.38).

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Trainingandphysicalexercisewerecomparedinonerandomisedtrial(Mülleretal.2001)andnodifferenceinbackpainwasfoundattheintermediatefollow-up.Theresultsofonecohortstudy(Dehlinetal.1981)providedsupporttotheconclusionmadeattheshort-termfollow-up.

Agroupreceivingtrainingandassistivedeviceswascomparedtothegroupsreceivingtrainingonlyornointerventionatallinonerandomisedtrial(Yassietal.2001).Nodifferenceinbackpainwasshownininterme-diatefollow-upofeithercomparison(OR0.42,95 %CI0.04to4.99).Inaddition,therewasnodifferenceinrelationtobackrelateddisability.

7.2. factors associated with self-assessed work ability (Study II)

Atotalof971consecutivepatientswereenrolledby12physicians.Questionnairescompletedbyboththepatientandthephysicianwereavailablefor950visits(98 %).Thestatisticalanalysesfocusedon723(76 %)visits,wherethereasonforthecontactgivenbythepatientandthediagnosismadebythephysicianwereinthesamemajordiseasegroup.

MSD(39 %)wasthemostcommonreasonforthevisit,followedbyrespiratory(17 %),cardiovascular(11 %),dermatological(9 %),mental(7 %),and"other"disorders(16 %).Inmostcasesthedurationofthesymptomswaslongerthansixmonths.Respiratorysymptomshadlastedforlessthantwoweeksinhalfofthecases.

Table 8. Self-assessed ability to work by the main diagnosis of the visit

Disease groupSelf-assessed ability to work

N able (%)

Partially able (%)

Unable (%)

Cannot say (%)

Musculoskeletal 283 51 28 16 5

respiratory 125 58 24 10 8

Cardiovascular 83 80 16 4 1

Dermatological 67 96 4 0 0

Mental 47 40 30 23 6

Other 118 74 19 6 2

TOTAL 723 63 22 11 4

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Sixty-threepercentofthepatientsreportedbeingabletoworkdespitetheirhealthproblem(table8).Intotal,partialworkabilitywasreportedby22 %andfulldisabilityby11 %ofthepatients.Thosewithmentaldisordersreportedfullorpartialdisabilitymostoften(in53 %ofthecases),followedbythosewithMSD(44 %).

Thepatientsregardedmental(85 %)andMSD(74 %)mostoftenasbeingatleastpossiblywork-related(table9).Thephysiciansweremorecautiousinassessingwork-relatednessineverydiseasecategory.Ingeneral,theyregardedthereasonaswork-relatedin13 %andpossiblywork-relatedin21%ofthevisits.Thedisordersmostoftenregardedaswork-relatedbythephysicianswerementalproblems(26 %)andMSD(22 %).

Table 9. Work-relatedness assessed by patients and physicians by the main diagnosis of the visit

N Not work-related (%)

Possibly work-related (%)

Work-related (%)

Cannot say (%)

Musculoskeletal 283

- Patients 18 41 33 8

- Physicians 42 34 22 2

respiratory 125

- Patients 51 32 6 10

Cardiovascular 83

- Patients 31 51 8 10

Dermatological 67

- Patients 66 12 6 16

Mental 47

- Patients 13 36 49 2

Other 118

- Patients 49 24 9 18

TOTAL 723

- Patients 34 35 20 11

7RESuLTS

Work-relatedinterventionswereconsideredasbeneficialbythepa-tientsinonethirdofthecases,mostfrequentlywhenthereasonforthevisitwasamentalproblem(56 %)orMSD(39 %).

Inthemultinomiallogisticregressionmodel,genderhadnoeffectonself-assessedworkability(table10),butolderagemarkedlyincreasedtheriskofdisability.Bluecollaremployeesranahigherriskofbothpartialandfulldisabilitycomparedtoupperwhitecollaremployees.Ashortdurationofthesymptomswasassociatedwithbothpartialandfulldisabilitytowork.

Table 10. Odds ratios (OR) and 95 % confidence intervals (CI) for the adjusted effects of the patient and disease characteristics on self-assessed ability to work

Self-assessed ability to workPartially ablea Unablea

Predictor OR 95% CI OR 95 % CIGender (male vs. female) 1.1 0.6–2.0 0.9 0.4–2.2

age (reference category '35 years or less')

– 35–44 years 1.2 0.6–2.5 4.8 1.2–18.6

– 45–54 years 1.1 0.5–2.2 4.3 1.1–17.1

– 55 years or older 1.6 0.7–4.0 8.9 1.9–41.4

Occupational group (reference category 'upper white collar')

– lower white collar 1.8 0.8–4.3 2.4 0.6–9.2

– blue collar 6.5 2.6–16.4 8.1 2.0–33.2Duration of the symptoms before the visit (reference category 'more than 6 months')

– 2–6 months 1.0 0.4–2.2 1.5 0.5–4.3

– 2 weeks to 2 months 2.0 0.8–4.5 0.6 0.1–2.6

– less than 2 weeks 3.4 1.6–7.5 3.7 1.3–10.7

Disease group ('other disease incl. skin diseases' as reference category)

– musculoskeletal 2.5 1.2–5.1 7.7 2.2–26.6

– respiratory 2.4 1.1–5.6 2.7 0.7–10.6

– cardiovascular 1.7 0.6–4.5 2.0 0.3–14.1

– mental 2.1 0.7–6.4 17.5 3.5–86.3

Assessment of work-relatedness

– 'possible' vs. 'no' 2.9 1.4–6.0 1.3 0.4–3.7

– 'yes' vs. 'no' 5.2 2.1–12.8 12.8 3.9–41.9

Potential of work-related interventions

– 'possible' vs. 'no' 1.6 0.8–3.0 0.5 0.2–1.2

– 'yes' vs. 'no' 2.0 0.9–4.6 0.2 0.1–0.8

OH centre (A vs. B) 1.1 0.5–2.2 3.4 1.2–9.7a reference category patients with self-assessed normal ability to work

7RESuLTS

MSDincreasedtherisksofbothpartialandfulldisability.Thehigh-estriskoffulldisabilitywasobservedformentaldisorders.Theriskofpartialworkabilitywasincreasedforrespiratorydiseases.Self-assessedwork-relatednessofthediseaseincreasedtherisksofbothpartialandfulldisabilitytowork,whereastheriskoffulldisabilitywassignificantlyreduced,ifthepatientconsideredwork-relatedinterventionsasbeingbeneficial.

TheOHcentrehadastatisticallysignificanteffectondisability,buteliminatingthisvariablefromthemodeldidnotaffecttheriskestimatesoftheothervariables.

7.3. Self-assessed productivity loss caused by upper extremity disorders (Study III)

Therecruitmentwasendedasplannedeventhoughthetargetof500studysubjectswasnotachieved.Thiswasduetothesmallerthanexpectednumberofsubjectsfulfillinginclusioncriteria,aswellastherelativelyslowrecruitingprocessingeneral.Altogether222subjectsparticipatedinthestudy.Forty-fivesubjectswereexcludedbecausetheydidnotmeetthecriteriaforeligibility,leaving177subjectstothestudy.Afterexclu-sionofafurtherninesubjectswithmissinginformationonproductivity,168subjects(95 %)wereincludedintheanalyses.Themostcommonoccupationswerenursesandotherhealthcareworkers(64 %),secretariesandotherclericalworkers(25 %),andwarehouseworkers(8 %).Themajority(87 %)werefemale,andtheaverageagewas45years.

ThemostprevalentUEDwereepicondylitis(29 %),specificshoulderdisorder(28 %)andnon-specificupperlimbpain(26 %).Thesubjectsreportedpainintensityandpaininterferencewithworktobeonaver-age4.7(max10)and4.8,respectively.Paininterferencewithsleepwassomewhatlower(3.3).SicknessabsenceduetoUEDduringthelast12monthswasreportedby37 %ofthesubjects.Workingatakeyboardandliftingloadswerethemostcommonphysicalworkloadfactors.Highjobstrainwasreportedby27 %ofthesubjects.Everyseventhsubjecthadelevatedscoresonfear-avoidancebeliefs,andeverysecondperceivedtheirdisorderasbeingwork-related.

Morethanhalfofthesubjects(56 %ofwomen,59 %ofmen)reportedthattheUEDhaddecreasedtheirproductivity.Theaverage

7RESuLTS

productionlosswas34 %duringthepreviousworkday,correspondingtoanaverageof19 %lossofproductivityamongallstudysubjects.

Ageandgenderwerenotassociatedwithproductivityloss(table11),andneitherweresmokinghabits,waistcircumferenceorphysicalactivity.Subjectsinthediagnosticcategory"other",mainlywithmedianorulnarnerveentrapment,wereatthehighestriskofproductivityloss.

Table 11. Odds ratios (OR) of productivity loss adjusted for gender and age* or gender alone** according to background characteristics

Characteristic all* 20-45 yrs** 46-64 yrs**OR 95 % CI n OR 95 % CI n OR 95 % CI

gender

Female (reference category) 67 79

Male 1.2 0.4-3.0 13 1.5 0.4-4.9 9 0.9 0.2-3.6

Age (continuous) 1.00 0.97-1.04 - -

Diagnosis

Epicondylitis (reference category) 25 24

Shoulder disorder 1.5 0.6-3.5 21 1.4 0.4-4.6 26 1.6 0.5 -4.9

Wrist tenosynovitis 1.7 0.5-5.3 8 4.2 0.6-26.3 9 0.8 0.2-3.7

Nonspecific pain 1.9 0.8-4.4 23 2.3 0.7-7.4 20 1.5 0.4-5.0

Other 6.2 1.2-31.4 3 9 3.5 0.6-20.4

Pain intensity

1st tertile (reference category) 26 27

2nd tertile 3.7 1.6-8.2 28 3.3 1.1-10.3 27 4.0 1.3-12.6

3rd tertile 3.0 1.4-6.6 26 3.1 0.99-9.6 30 2.9 0.98-8.6

Pain interference with work

2nd tertile 2.7 1.2-5.9 24 1.9 0.5-6.4 30 3.6 1.2-10.5

3rd tertile 6.2 2.6-14.4 32 6.7 2.0-22.3 23 5.1 1.5-16.9

Pain interference with leisure time

2nd tertile 1.7 0.8-3.7 32 1.4 0.4-4.2 25 2.2 0.7-6.5

3rd tertile 1.8 0.8-3.8 27 1.4 0.4-4.3 28 2.2 0.7-6.2

Pain interference with sleep

2nd tertile 1.6 0.7-3.4 31 0.7 0.2-2.2 25 4.2 1.3-13.5

3rd tertile 2.5 1.1-5.5 23 1.0 0.3-3.2 33 6.0 1.9-18.6

Table 11. continues...

7RESuLTS

Characteristic all* 20-45 yrs** 46-64 yrs**OR 95 % CI n OR 95 % CI n OR 95 % CI

Physical exposures at work

Lifting loads, >5 kg

No (reference category) 52 68

Yes 2.1 0.99-4.5 28 1.9 0.7-5.1 18 2.3 0.7-7.2

Arm elevations or above shoulder

Yes 1.9 0.7-4.9 13 2.1 0.5-7.6 9 1.6 0.3-6.8

Forceful or pinch grip

Yes 1.5 0.5-4.4 11 1.5 0.4-5.8 6 1.6 0.2-9.1

Working at a keyboard

Yes 0.7 0.3-1.4 41 1.4 0.5-3.5 41 0.4 0.2 -1.1

Previous sickness absence (past 12 months)

Yes 2.2 1.1-4.3 34 3.4 1.3-8.7 28 1.5 0.5-3.7

High job strain

Yes 1.3 0.6-2.8 23 3.9 1.3-11.8 20 0.5 0.2-1.4

Elevated score on fear-avoidance beliefs

Yes 3.5 1.2-9.9 11 4.6 0.9-23.1 13 2.8 0.7-10.9

Painintensity,paininterferencewithwork,andfear-avoidancebeliefswereassociatedwithproductivityloss.Paininterferencewithsleepwasalsoassociatedwithproductivityloss,butonlyintheolderagegroup.

Withrespecttothephysicalexposuresatwork,onlyliftingatworkshowedanassociationwithproductivityloss.Highjobstrainandpriorsickleavewereassociatedwithproductivityloss,butonlyamongtheyoungersubjects.Iftheyoungersubjectswereconvincedaboutwork-relatednessofthedisorder(responseinthethirdtertile),theprevalenceofproductivitylosswasincreased(OR4.5,95 %CI1.2–16.6).Nosimilarassociationwasfoundintheoldersubjects.

7RESuLTS

Inamutuallyadjustedmodelwithgender,age,painintensity,physicalexposuresatwork,previoussicknessabsence,highjobstrainandfear-avoidancebeliefs,onlypainintensityandfear-avoidancebeliefsshowedassociationswithproductivityloss.PaininterferencewithworkwasalsoassociatedwithproductivitylosswithanORof2.5(95 %CI1.1–5.7)forthe2ndtertileand5.7(95 %CI2.2–14.3)forthe3rdtertile,whenitwasincludedinthemodelinsteadofpainintensity.Intheyoungerworkersonlyhighjobstrain,andintheolderworkersonlypaininter-ferencewithsleep,remainedstatisticallysignificantafteradjustmentfortheotherfactors.

Theseparateandjointeffectsofphysicalworkloadfactors,painin-tensityandjobstrainonproductivitylosswerealsostudied.Ingeneralintheyoungersubjects,acombinationofanytwoofthesefactorswasassociatedwithahigherdegreeofproductivitylossthanthepresenceofonlyonefactor.Highjobstrainseemedtocontributemosttotheproductivitylossandphysicalexposurestheleast.Whentheinterac-tionproductswereincludedinthelogisticregressionmodels,onlytheinclusionoftheinteractionbetweenphysicalloadsandpainintensityimprovedthegoodness-of-fitofthemodel.

7.4. Effectiveness of an ergonomic interven-tion on productivity loss (Study Iv)

Atotalof177participantswererandomisedtotheintervention(91subjects)andcontrolgroup(86subjects).Duringthe12weekfollow-up,theparticipationratewas87 %intheinterventiongroupand88 %inthecontrolgroup.

Mostparticipantswerefemaleinbothgroups.Therewasnomajordif-ferenceinthedistributionofageandlife-stylerelatedriskfactorsbetweentheinterventionandcontrolgroup.Painintensity,paininterferencewithwork,leisuretimeandsleep,aswellastheprevalenceofprevioussickleavesandhighjobstrainwerealsosimilarinthetwogroups.Bothgroupshadsimilarmeanscoresforthefear-avoidancebeliefs;however,elevatedscoresonfear-avoidancebeliefswerefoundalmosttwiceasoftenintheinterventiongroupasinthecontrolgroup(18 %versus11 %).Specificshoulderdisordersweremoreprevalent(35 %versus21 %)

7RESuLTS

andexposuretoliftingatworkwasmorefrequent(38 %versus18 %)inthecontrolgroupthanintheinterventiongroup.Allcasesof“otherUED”belongedtotheinterventiongrouponly.

Fromatotalof531potentialobservations,465(88 %)wereincludedintheanalyses.Nineobservationsatbaseline,36at8weeksand21at12weekswereexcluded.Incomparisonwiththoseincludedintheanalyses,theexcludedsubjectswereyounger(meanage42versus46years),theyhadhigherscoresonpainintensity(5.4versus4.7),andtheyhadbeenmoreoftenonsickleavepriortotheenrolment(57 %versus36 %).Inaddition,theexcludedemployeesweretwiceasoftenexposedtoliftingatworkthantheemployeesincludedintheanalyses(46 %versus28 %).

Withrespecttothe66excludedobservations,30(46 %)wereinthecontrolgroupand36(55 %)intheinterventiongroup.Thoseexcludedfromtotheinterventiongroupmorecommonlyreportedexposuretolifting>5kg(53 %versus34 %),andhadahigherlevelofpainintensity(mean5.6versus5.1),paininterferencewithwork(mean5.5versus4.7),paininterferencewithleisuretime(mean5.4versus4.2),andpaininterferencewithsleep(mean4.2versus2.4)atbaselineincomparisontotheexcludedsubjectsinthecontrolgroup.Ontheotherhand,excludedsubjectsintheinterventiongrouplessfrequentlyreportedproductivityloss(among39subjects,magnitude13 %versus30 %)andelevatedscoreonfear-avoidancebeliefs(0versus18.5 %)thanthoseexcludedinthecontrolgroup.Nodiffer-enceswerefoundwithrespecttoage,jobstrainandsicknessabsencepriortotheenrolment.

Eightweeksaftertheenrolment,almostallsubjects(92 %)intheinterventiongroupbutonly8 %inthecontrolgroupreportedthatanoccupationalphysiotherapisthadvisitedtheirworkplace.Theer-gonomicassessmentwasmostoftenmadetogetherwiththeemployeealone,andthesupervisorhadparticipatedin17 %oftheassessments.Atotalof412implementedorplannedmeasureshadbeenidentified.Themajority(60 %)wererelatedtoguidingtheemployeeinselfcare,workingposture,useoftoolsandinstruments,usingbothhandsinworktasks,andreorganisinghowtheworkwasdone.Therecom-mendationstobeimplementedintheimminentfuture(25 %ofthemeasures)includedpurchasinganewaidortool,andreorganisingworkoritsenvironment.Themodificationsatworkmadeduringthevisit

7RESuLTS

(16 %ofthemeasures)includedchangestothekeyboardandmonitor,structuresoftheworkplace(includingarmrests),andadjustmentstothetableandthechair.

Productivitylossatbaselinewasreportedby53.8 %intheinterven-tiongroupand57.9 %inthecontrolgroup(figure5).At8weeks,boththeproportionandmagnitudeofproductivitylosswerelowerintheinterventionthaninthecontrolgroup.However,thedifferenceswerenotstatisticallysignificant.At12weeks,theproportionandmagnitudeofproductivitylosswerestatisticallysignificantlylowerintheinterventionthaninthecontrolgroup(proportion25 %versus51 %andmagnitude7 %versus18 %,respectively,P=0.001forboth).

TheanalysisofrepeatedmeasuresusingGEErevealedstatisticallysignificantdifferencesintheproportionandmagnitudeofproductivitylossbetweentheinterventionandcontrolgroupafteradjustmentforage,gender,physicalworkloadfactors,fear-avoidancebeliefsandfollow-

Baseline (N = 168) 8 weeks (N = 141) 12 weeks (N = 156)

Proportion (control)Proportion (intervention)Magnitude (control)Magnitude (intervention)

FigurE 5. Proportion and magnitude of productivity loss (on a logarithmic scale) at baseline, eight and twelve weeks after the intervention in the con-trol and intervention groups.

7RESuLTS

uptime.Therewasaninteractionbetweeninterventionandtime,theproportion(P=0.009)andmagnitude(P=0.033)ofproductivitylossbeinglowerintheinterventiongroupthaninthecontrolgrouponlyat12weeks.

Intheemployeeswithoutanyproductivitylossatbaseline,15.6 %intheinterventiongrouphaddevelopedproductivitylossat8weeks,whereasthisproportionwasalmosttwo-foldinthecontrolgroup.Themagnitudeofproductivitylosswas3.7 %and8.1 %,respectively.At12weekstherewasalmosta4-folddifferenceintheproportionandan8-folddifferenceinthemagnitudebetweentheinterventionandcontrolgroup.WithGEEanalyses,thedifferenceswerenotedtobestatisticallysignificant.

Amongemployeeswithproductivitylossof10–20 %atbaseline,thereductioninmagnitudeofproductivitylosswasmoreprominentintheinterventiongroupthanoccurredinthecontrolgroupat8weeksand12weeks.At12weeksalsotheproportionofproductivitylosswaslowerintheinterventionthaninthecontrolgroup.Ifthebaselineproductivitylosswashigherthan20 %,therewerenosignificantdif-ferencesbetweenthestudygroupsintermsofproductivitylossduringthefollow-up.

Theimprovementofproductivityat12weekswassignificantlybetterintheinterventiongroupthaninthecontrolgroupinthesubsampleofsubjectswithnoworkingatakeyboardatworkbutexposuretootherphysicalworkloadfactors(P=0.033),withlowjobdemands(P=0.036),amongthosewithnosicknessabsenceduetoUEDbeforethestudy(P=0.043),aswellasthosewithlowfearavoidance(P=0.033).Theimprovementdidnotdifferbetweeninterventionandcontrolgroupsinthosewithloworhighjobcontrol.

Amongthosewhohadbeenonsickleaveforanyreasonduringfourweeksprecedingthefollow-upat12weeks,therewasnodifferenceinthechangeofproductivitybetweentheinterventionandcontrolgroups.Incontrast,thoseindividualsintheinterventiongroupwhohadnotbeenonsickleave,hadahigherimprovementinproductivityat12weekscomparedwiththecontrolgroup(6.5versus2.4%,P=0.033).

Therewasnodifferencebetweenthecontrolandinterventiongroupinpainintensityat12weeks(mean2.6versus2.9)orinpaininterfer-encewithwork(mean2.4versus2.5).

7RESuLTS

7.5. Early part-time sick leave in musculoskeletal disorders (Study v)

Duringthepilotstudythereweresomechallengesrelatedtofindingeli-gibleindividualsattheOHS,anextraworkloadontheOHphysiciansinimplementingtheinterventiontotheemployeesandthesupervisors,aswellasthemanypracticalissuesrelatedtoadministrativequestionsatworkduringpart-timesickleave.However,thearrangementsattheworkplacewereusuallyconsideredasbeingfeasibletoimplementandtheattitudeofthesupervisorsandco-workerswasmostlypositiveandsupportive.ThisprovidedanimpetustoinitiatetheactualRCTatthebeginningof2008.TherecruitmentperiodofthisstudyendedinDe-cember2009,butthefollow-upwillnotenduntilDecember2010,andthereportingoftheresultswillstartin2011.

8. DISCUSSION

8.1. Main findings

8.1.1. Primary prevention of low back pain and related disability

Wefoundnoevidencethattrainingwithorwithoutliftingequipmentwouldbeeffectiveinthepreventionofbackpainorconsequentdisabil-ity(studyquestionNoI).Thereasonmaybethateithertheadvocatedtechniquesdidnotreducetheriskofbackinjury,ortrainingdidnotleadtoanadequatechangeinliftingandhandlingtechniques.Therewerenodifferencesintheresultsbetweentheanalysesfromstudieswithdifferentdesignsorwithdifferenttypesofliftingandhandling.Tworandomisedcontrolledtrialspublishedlaterlentsupporttothepresentresults(Jensenetal.2006;Lavenderetal.2007).

Oneexplanationforthelackofanyeffectcouldbethattheinterven-tionwasnotappropriate.Astrainingmethodsbecomemoreengaging,workersacquiremoreknowledgeandthenumberofinjuriesdeclines(Burkeetal.2006).Accordingly,thetrainingmethodswereclassifiedbasedonlearners’participation,butthereviewfailedtodetectamorepositiveoutcomeforstudiesthatinvolvedmoreintensetrainingmethods.

Theriskofbackpainmightberelatednottoincorrecthandlingtechniquesbuttootherwork-relatedfactorsinherentinthepopulationsstudied(suchasnon-neutral,bent,orrotatedtrunkpostureswithoutliftingorhandling,orpsychosocialstrain).Itwasnotpossibletotestthishypothesis,however,becausenoneofthestudiesdescribedthecontextoftheinterventioninsufficientdetailtoenablefurtheranalysis.Ithasalsobeenarguedthatthesizeoftheeffectofwork-relatedphysicaldemands

8DISCuSSION

islessthanthatofotherindividual,non-occupationalandunidentifiedfactors(Waddelletal.2001).

OnereasonwhytrainingincorrectliftingtechniquesandassistivedevicesdidnotreduceLBPorrelateddisabilityismostlikelythecom-plexityoftheimpactofphysicalandpsychosocialriskfactorsatwork.AsproposedbythemodelofCoxetal(Figure3),evenphysicalloadfactorswhichhaveaninfluenceontheworker’shealtharemediatedthroughcognitiveandpsycho-physiologicalpathways.Thus,thereductionofonlyphysicalloadatworkdoesnot,therefore,automaticallyresultinthereductionofmusculoskeletalsymptomsanddisability.Theneedforinfluencingsimultaneouslyonbothphysicalandpsychosocialexposurehasbeenseenasthemoreeffectiveapproachtothereductionofdis-ability(Coteetal.2008),preferablyincollaborationwiththeworkers(Hignettetal.2005).

8.1.2. factors associated with perceived disability

TheresultsofstudyIIindicatedthatperceivedpartialdisabilityiscom-mon,especiallyinmentalproblemsandMSD.Thesetwodisordersarealsomostoftenregardedaswork-relatedbythepatientsandtheirphysicians.MSDandmentaldisordersassuch,aswellasperceivedwork-relatednessofthehealthproblem,arestronglyassociatedwithimpairmentinself-assessedworkability(studyquestionNoII).

Accordingtothepatients,74 %ofMSDcasesweredefinitelyorpossiblycausedormadeworsebywork,whereasOHphysiciansfounddefinitework-relatednessinonly22 %andapossibleconnectionin34 %ofthecases.ThesefiguresarecomparabletotheresultsofaNor-wegianstudy,wherepainintheneck,shoulderandarmwasconsideredasbeingwork-relatedby78–80 %ofthesubjects(Mehlumetal.2009).Inthatstudy,thephysiciansusedspecificcriteriaforwork-relatedness,andtheyassessedwork-relatednessas"probably","possibly"and"notwork-related".Thesedifferencesexplainwhyinthepresentstudythephysicians'assessmentswerelowerthantheexperts'assessmentsintheNorwegianstudy(56 %versus65–72 %).Moreover,intheNorwegianstudy,thephysicianknewthestudysubject’sassessmentbeforemakinghis/herownevaluation.

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Anotherstudyhascomparedtheassessmentsofwork-relatednessmadebypatientsonsickleaveascomparedwiththeassessmentbytheirOHphysicians(Girietal.2009).Onceagain,thepatientsmoreoftenbelievedthattheillnesshasbeencausedbyworkthanOHphysi-cians(30 %versus16 %),andthattheillnesswasmadeworsebywork(60 %versus44 %).InadditiontoMSDandotherillnesses,37 %ofthepatientshadamentalproblemasthereasonforabsence,whichmayhaveinfluencedthepatients'assessmentsofwork-relatednessoftheirailments.

Thisstudyshowedthatthepatients'negativeperceptionsabouttheirillnessandworkwouldbeassociatedwithimpairedabilitytowork.Thiswasacross-sectionalstudyand,therefore,itisnotknownifthepatientswereabsentfromworkbecauseoftheillnessaftertheconsulta-tion.However,laterstudieshavefoundevidencethatemployeeswithnegativeperceptionsabouttheirillnessarelesslikelytoreturntoworkthanthosewithpositivebeliefs(Elferingetal.2009;Girietal.2009)

Thisstudyrevealedthattheriskofperceiveddisabilitywaslowerifthepatientfoundbenefitsinpotentialwork-relatedinterventions.Inapreviousstudy(Tellnesetal.1990),apotentialforpreventionwasfoundin37 %ofthehealthproblemsunderlyingsicknesscertificates.Inthisstudy,work-relatedinterventionswereinitiatedexactlyasoftenasinanotherFinnishstudy,where9 %ofthevisitstoOHphysiciansincludedorledtowork-relatedinterventions(Räsänenetal.1997).Thereasonforthisfigurebeingconsiderablylowerthantheprevalenceofwork-relateddiseasesmaybethatwork-relatedinterventionshavebeeninitiatedalreadyduringearliervisitstotheOHphysician.

Basedontheresults,partialabilityofanemployeetoworkcanpos-siblyberestored,maintainedandpromotedbyactionsdirectedattheindividual,butitshouldalsoincludemodifyingtheworkenvironmentandorganizingworkaccordingtotheindividual’scapabilities.Inaddi-tion,recognitionofwork-relateddiseasesisimportantfortheappropriateassessmentofpatient'sill-healthandfortheeffectivenessoftherapeuticinterventions.Identifyingwork-relatednesshasthepotentialalsoformoreadequateprevention,notonlyconcerningtheindividualpatientsbutalsotheirco-workers,andforlessabsenteeismfromwork.

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8.1.3. Productivity loss as an indicator of disability

InstudyIII,morethanhalfofthesubjectswithclinicallydiagnosedUEDreportedthatthedisorderimpairedtheirproductivityinvariousphysicalaswellassedentaryoccupations(studyquestionIII).Onaverage,work-erswithUEDreportedthatonethirdoftheirregularproductivityhasbeenlost,whichinanormalworkdaywouldcorrespondto2.5hoursofactiveworkingtime.

Ourresultsareconsistentwithcurrentknowledge,i.e.,painin-tensity,paininterferencewithwork,andliftingatworkareassociatedwithself-reportedproductivityloss(Hagbergetal.2007;Boströmetal.2008).Nostudieshavesofarreportedabouttheroleoffear-avoidancebeliefsinproductivityloss.Conceptually,fearfulbeliefsmaycontrib-uteconsiderablytoproductivitylosssincetheyserveasanadaptivereactiontopainwithsomeworkactivitiesbeingavoidediftheyareanticipatedtoproducepainandfearedsincetheycancause'damage'.BeliefsthatworkdeteriorateschronicLBPhavebeenshowntoincreasetheriskofbothworklossanddisabilityindailyactivities(Waddelletal.1993).Ingeneral,fear-avoidancebeliefsarestrongpredictorsoffuturedisability(Ilesetal.2008).However,itseemsthatthisisthefirststudytoreportfear-avoidancebeliefsaffectingproductivitylossinnon-chronicconditions.

Unlikethepreviousstudies,noassociationwasfoundbetweenageandproductivityloss(Collinsetal.2005;vandenHeuveletal.2007;Alaviniaetal.2009).However,itwasfoundthatagemodifiedtheeffectsofotherfactors,particularlythecombinedeffectsofphysicalwork,jobstrainandpainintensity,onproductivityloss.Thestrongestdeterminantsofproductivitylossinyoungerworkerswerehavingtwoofthefollowingfactors;intensivepain,highjobstrain,andphysicalwork.Olderwork-ers'productivitywasnotaffectedbythecombinationofthesefactors.

Similarresults,indicatingthattheyoungerworkersmaybemoresusceptibletotheeffectsofwork,havebeenfoundforexampleinaprospectivestudyonthepredictorsoflow-backpain(Mirandaetal.2008),aswellasinrelationtosicknessabsence(Taimelaetal.2007).Theage-modificationinproductivitylossmaypartlybeexplainedbyhealth-basedselectioninwhichworkerswithhealthproblemsaremorelikelytoleaveajob.Otherpossibleexplanationsareyoungeremployees'(ortheir

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supervisors’)higherexpectationsfordailyperformance,aswellasolderworkers'betterskillstocompensateforhealth-relatedproductivityloss.

8.1.4. Secondary prevention of disability

TheresultsofstudyIVshowthatanearlyergonomicinterventioninadditiontomedicalcarecanhelptoreducework–relatedproductivitylossassociatedwithUEDcomparedtomedicalcareonly(studyquestionIV).Thefactthatthedifferencebetweenthecontrolandinterventiongroupwaslargestat12weeksaftertheenrolment,suggeststhattheresultisbasedonactualimpactoftheinterventionratherthanonthesubjects'satisfactionwiththeadditionalattentiontheyhadreceivedfromtheOHS.Manyofthenewaidsortoolsrecommendedbytheoccupationalphysiotherapistswerenotpurchaseduntillaterduringthecourseofthestudy.Thismayfurtherexplainwhythedifferencebetweenthestudygroupswasfoundonlyat12weeks.

Onepossibleexplanationfortheimprovedproductivityisthattheinterventionmanagedtomodifytheemployees'adverseworkstyles,whichhasbeenshowntobeariskfactorforupperextremitypainandfunctionallimitations(Nicholasetal.2005;Meijeretal.2008).Thecon-tactsbythephysicianandthephysiotherapistmightalsohavepromotedabetterunderstandingofthenatureandconsequencesofthedisorderattheworkplace.Consequently,theemployeeandthesupervisorwereabletoadjusttheworkrequirementstobettermeettherestrictionsduringrecoveryandthenthephysiotherapist'spracticalsuggestionssupportedtheimplementationofthesechanges.

Althoughtheinterventionshowedbeneficialeffectsonproductivity,nodifferenceinpainintensitywasfoundbetweenthegroupsat12weeks.Therefore,painreliefdoesnotexplaintheresults.Sincethedifferenceinproductivityat12weekswasseenalsointhesubgroupwithnosick-nessabsenceduringthefollow-up,theresultscannotalsobeduetotheinterveningimpactofsicknessabsenteeism.

Asubstantialeffectoftheinterventionwasseenamongthoseem-ployeeswithnooronlymildproductivitylossatbaseline.Theothersubgroupanalysesshowedthatthosewithlessfear-avoidancebeliefs,morephysicalloadfactorsatwork,orlowjobdemandsbenefittedmorefromtheintervention.Thissuggeststhattheimpactoftheintervention

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onproductivitycouldbemediatedbyareductioninphysicalloadfactors.Iftheconditioncausedmorefunctionalimpairment(productivitylosswasmorethan20 %atbaselineortherewasprevioussickleaveduetoUED),itwasfoundthattheinterventionwasnoteffective.WhenthedisabilitycausedbyUEDwastoosevere,itseemsthatergonomicinter-ventionshavelesspotentialforrestoringnormalperformanceatwork.

8.1.5. Comparison of two disability management methods

ThetargetofthisprotocolwastodescribeaRCTwithastudyinterven-tionofadjustingwork(bothworktimeanddemands)toaccommodatethedisabledemployeesothatheorshewouldbeabletocontinueworkingduringrecoveryfromaMSD(studyquestionNoV).ThisisbelievedtobethefirstRCTtoinvestigatetheeffectivenessofearlypart-timesickleaveincomparisontoconventionalfull-timesickleaveinmusculoskeletalsymptoms.TheresultsandtheincreasedknowledgewillleadtoabetterdecisionmakingprocessregardingthemanagementofdisabilityrelatedtoMSD.

Despitethefactthatpart-timesicknessabsencehasbeenmadepossibleinmanyjurisdictions,thisoptionhasnotbeenstudiedinarandomisedcontrolledsetting(Kaustoetal.2008).Inaddition,there-sultsofstudyIIshowthatmorethaneveryfourthemployeecomingtomedicalconsultationbecauseofMSDreportedthattheywerepartiallyabletocontinueworkingdespitethedisorder(table8).

Aspointedoutearlier(Durandetal.2007),inthistypeofinterven-tionworkbecomesanobjectoftheinterventionitselfposingseveralmethodologicalchallenges.Inadditiontothemedicaljudgementbythephysician,theinterventionrequiresactionsanddecisionsmadebytheemployee,supervisor,colleaguesandemployer–eachwiththeirownvalues,objectives,interests,andtraining(Loiseletal.2005).

Sicknessabsenceisusuallyconsideredasaconsequenceofahealthdisorderratherthanitstreatmentand,therefore,inmoststudies,ithasbeenusedasanoutcomemeasure.Inthistrial,however,themodeofsickleave(part-orfull-time)isusedasaninterventiontoaffecttheoutcome,i.e.,thequantityofsickleave(cumulativenumberofsickleavedays).Thepotentialbenefitoftheintervention,i.e.,thedifferenceinthetotal

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numberoffull-orpart-timesickleavedaysbetweentheinterventionandcontrolgroups,willmostlybeattributedtotheneedforeitheradditionalpart-orfull-timesickleaveduringthefollow-upperiod.

8.2. Methodological considerations

8.2.1. Study designs

Thestrengthofthiscombinationofstudiesisthattheyfollowthecourseofdisability(figure4)recognisingthefourpotentialstepsintheinterven-tions.Thestudiesrepresentsystematicreview,surveys(bothcross-sectionalquestionnaireandbaselineassessment),andrandomisedcontrolledtrials.

Systematic review

ThestrengthofthereviewisthatitadheredtothesystematicandrigorousCochranemethodsinsearchingtheliterature,selectingtheinterventionsandstudydesigns,aswellassynthesisingthedata.

Themeasurementoftheoutcomesintheprimarystudiesvariedleadingtoconsiderabledifferencesinthereportedincidencesofbackpain.Anotherlimitationwasthatalltherequireddatacouldnotbeextractedfromallstudies,limitingthepossibilitiesofpoolingthedata.Inaddition,theresultsofmostofthestudieshadtobeadjustedfortheeffectofclusterrandomisationthathadnotbeentakenintoaccountbytheoriginalauthors.

ItisnotpossibletoexcludethepossibilitythatthestudiesandthereviewlackedthepowertodetectasmallbutpossiblyrelevantdifferenceintheincidenceofLBP.Itis,however,highlyunlikelythatpoolingtheresultsofmorestudieswouldhavefoundasignificantbeneficialeffect.ThisisbecausealmostallstudiesshowedanORthatwasnearto1,andtheappliedcomparisonswereallrathersimilar,especiallyastheuseofalumbarsupportcanbeconsideredequaltonointerventionwithrespecttothepreventionofbackpain(Jellemaetal.2001).Onlyonestudyshowedamorepositive,butstillnon-significant,outcome(Yassietal.2001).Thiscouldbebecausethetypeoftheinterventionwasdifferent(“nostrenuouslifting”).

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Surveys

InstudyII,onemayquestionwhetherthepatientswerecompetenttoassesstheworkrelatednessoftheirsymptoms.Itcanbearguedthatthepatient'sassessmentisbasedmoreonillness-relatedproblemsatworkratherthanonoccupationalcontributorsoftheillness,leadingtoover-reportingofwork-relatedness.Differentperceptionsofwork-relatednessbypatientsandtheirphysicianshavebeenregardedasacriticalpointofaneffectiveconsultationprocess(Plomp1993).Theworkers'confidenceintheOHphysicianisalsobasedontheirassessmentsofthephysician'smedicalexpertiseandhis/herunderstandingoftheworkersandtheirproblems(Plomp1992).Inthisstudy,however,thevalidityofpatients'assessmentsofwork-relatednessissupportedbythesimilaroccupationalexposuresreportedbythepatientsandtheirphysicians.

Onepotentialsourceofsystematicerrorinthetwosurveysisthesocalled"commonsourcebias".Whenboththeoutcome(perceiveddisabilityorself-assessedproductivityloss)andthestudyvariables(forexample,work-relatednessofthedisorderorfear-avoidancebeliefs)areinquiredfromtheemployee,thismightleadtoacommonsourcebias(Podsakoffetal.2003).Peoplerespondingtoquestionsposedbyresearch-erscanhaveadesiretoappearconsistentandrationalintheirresponsesandmightsearchforsimilaritiesinthequestionsbeingaskedofthem.However,resultssimilartothosedescribedinstudyIIandIIIhavebeenreportedalsoinotherstudiesusingmoreobjectivedatasources.

Incontrasttopreviousstudies,theincludedsubjectsinstudiesIII–IVwereexaminedbyatrainedphysicianusingstandardizeddiagnosticcri-teria.Onthewhole,validatedquestionswereusedtocollectinformationonseveralbackgroundvariables.However,unmeasuredconfoundingforexampleduetonon-occupationalormotivationalissuesmayhaveaffectedtheresults.

Thedifficultyinquantifyingproductivity,particularlyininforma-tionandservice-typeoccupations,hasledtoamultitudeofmeasure-mentinstrumentsbasedonself-reporting.TheQQmethodbyBrouwerwasadaptedbyspecifyingittoconcernUED,evenifitwasoriginallydesignedtobeusedforanydisease.ThestrengthoftheQQmethodisthattheeffectofthehealthconditiononthequantityandthequalityofproductivitycanbedifferentiated.Moreover,unlikethesituation

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withmanyotherquestionnaires,thereisareferenceagainstwhichthelosscanbecompared,i.e.,therespondentsareaskedtoratetheattainedquantityandqualityofdailyworkcomparedtothatoftheirregularworkday.Naturally,thereareotherreasonsforlostproductivitythatarenotrelatedtohealth.However,theQQmethodtakesintoaccounttheseotherreasonsforproductionlossbyusingtheregularworkperformanceasaninternalstandard.

Moreover,theself-assessmentswereunlikelytohavebeenaffectedbyrecallproblemssincetherecallperiodofproductivitywasshortinthisstudy.Formostemployees,theprecedingfullregularworkingdaywasthedaybeforetheconsultationoratmostitwaswithinoneweek.Theshorttimeframealsomeansthattheproductivitylossassessedinthisstudydidnotnecessarilyreflectlongerlastingproductivityloss.ConsideringthenatureofclinicalUED,itis,however,unlikelythatthesituationwouldchangerapidlyfromonedaytothenext.

Randomised controlled trials

Therandomisedcontrolleddesignisconsideredastheleastsusceptibletobiasinscientificinterventionresearch.InstudyIV,theinterventionandcontrolgroupswerecomparablewithoutanymajordifferencesotherthantheinterventionitself.Theergonomicinterventionreachedalmostallsubjectsintheinterventiongroupandmorethan400improvementswereproposed.

Liftingatworkandspecificshoulderdisorderswere,however,some-whatmoreprevalentinthecontrolgroup,whereastheproportionofelevatedscoresinfear-avoidancebeliefswashigherintheinterventiongroup.Thesubgroupanalysesinthisstudyshowedthatthoseemployeeswhowereexposedtolifting,forcefulgrippingorelevatedarmposturesorwhohadlessfear-avoidancebeliefsbenefittedfromtheinterventionmorethanthosewhohadlessphysicalexposuresatworkormorefear-avoidancebeliefs.Therefore,thesedifferencesatbaselinemighthavedilutedthebenefitsoftheintervention.Anotherfactthatmighthavehadasimilareffectontheresultsisthemethodtoreplaceproductivitydataat12weekswiththevaluesat8weekswhichhadtobedonefor8subjectsintheinterventiongroup;thismayhaveoverestimatedtheremainingproductivitylossat12weeks.

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Sincetherearenoobjectivemeasuresforproductivityinmostoccupa-tions,thegenerallyacceptedmethodistouseself-assessedproductivityaswasdoneinthisstudy.Inpreviousinterventionstudiesamongem-ployeeswithsymptomsintheupperextremitiesandneckregion,bothobjectiveandself-assessedproductivityhavebeenmeasured(vandenHeuveletal.2003;Rempeletal.2006).Incomparisontothesestudies,theweaknessofthispresentstudyisthatthatnoobjectivemeasurementofproductivitycouldbeused,whereasthestrengthisthatthedisordersweremedicallyverifiedusingstandardizeddiagnosticcriteria.

InstudyVcomparingtheeffectsofpart-andfull-timesicknessabsence,itisessentialthatthephysiciandeterminesthelengthofthedisabilitybeforeallocation,andadherestothisevaluationwhenprescribingeitherpart-orfull-timesickleave.Thisistoavoidbiasthatmightoccurifthelengthofthesickleaveisdetermineddifferentlyforpart-andfull-timesickleave.Thereisariskforbiasrelatedtothepossiblecontrolvisit,duringwhichtheallocationtofurtherpart-orfull-timesickleaveisagainopentoboththephysicianandtheemployee.Inadditiontorecurrenceofsickleave,aninappropriatelytimedreturntoregularworkineithergroupcouldbeanticipatedtoresultinsecondaryoutcomes,suchaspain,functionalstatus,employeesatisfactionandfinancialcoststotheemployer.

Despitetheextensiveamountofquantitativedatacollectedinthistrialonindividual,ergonomic,psychosocialandeconomicfactors,itisnotpossibletoquantifyalltheaspectsofthearrangementsmadeattheworkplacesduringpart-timesickleave.Acknowledgingthepotentialeffectofthiscontextualprocessontheoutcomeoftheintervention,allrelevantqualitativedatawillbecollectedduringthestudyfromtheemployeeandthesupervisor.

8.2.2. Study populations

Thestudieshaveincludedonlyworkingindividualsrepresentingawiderangeofemployeesinseveraloccupations.StudiesII–Vincludedonlyworkerswhosemusculoskeletalsymptomswereverifiedbyaphysician,whereasself-reportedLBPwasregisteredinstudyI.

Thereview(studyI)includedstudieswithemployeesexposedtoheavyliftingatwork.Theoriginalaimwastoincludeonlypreventionstudieswithworkerswithoutbackpainatbaseline.However,intheeli-

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giblestudiestherewerealwayssomeworkersalreadysufferingfrombackpainatbaseline.Therefore,thisinclusioncriterionhadtobechangedtoworkerswhowerenotactivelyseekingtreatmentforcurrentbackpain.

ThepreviouslyreportedprevalencesandmagnitudesofproductivitylossassociatedwithMSDhavebeenlowerthanthatestimatedinstudyIII(Hagbergetal.2002;vandenHeuveletal.2007).Themainreasonmaybethatthepreviousstudieshaveincludedsubjectswithself-reportedsymptoms,whereasinthisstudy,subjectswiththesymptomshadsoughtmedicaladvice,andformostofthem,thephysiciandiagnosedaspecificUED.Hence,theirconditionwasmoresevereandspecificthansimplyanexperienceofpain.

ThesubjectsinstudiesIIIandIVwereactivelyworkingindividualsfromthreecompanieswithvaryingexposuretowork-relatedfactors.Theseindividualswereseekingmedicaladvicefortheirupperextremitysymptoms.Theintendednumberofstudysubjectswasnotgathered.Duetotherelativelysmallpopulation,theresultsarenotveryprecise,asindicatedbythewidthoftheconfidenceintervalsinstudyIII,andthereweresomebaselinedifferencesinstudyIV.However,despitethelimitedstudysize,theresultssupportthepositiveeffectsofanearlyergonomicintervention.

TheparticipationrateinstudyIVcanbeconsideredashigh(88 %)duringthe12weeks’follow-up.However,duetotheincompletein-formation atbaselineandlosstofollow-up,someselectionmayhaveoccurred.Itwasanalyzedwhetherthoseindividualslosttofollow-upallocatedinitiallytointerventionorcontrolgroupdifferedwithrespecttobaselinevariables.Theconclusionwasthatthedrop-outs andthosewithincompletedata inthe interventiongroup reported ahigher exposuretoliftingandhadhigherlevelsofpainintensityandpaininterferencewithwork,leisuretimeandsleepthanthoseinthecontrolgroup.Ontheotherhand, lessproductivitylossandfear-avoidancebeliefswerereportedbythedrop-outsinitiallyintheinterventiongroup.Ifaselec-tionbiasduetonon-participationhadaffectedtheseresults,itseems,however,unlikelythatitcausedanysignificantoverestimationintheobservedimpactoftheintervention.

TheOHSstaffswererequestedtorecommendstudyparticipationtoallpotentiallyeligiblesubjects,butthereisnoinformationaboutwhetherthiswasthecase.Furthermore,itisnotknownhowmanysubjectsde-

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clinedtoparticipate.ItistruethatafterbeingexaminedattheFIOH,nonedeclined.Thiswasoriginallyanergonomicinterventionstudy,anditcouldbethatthoseindividualswithmoreseveresymptoms(andlowerproductivity)werelesslikelytoparticipate.

8.3. Implications for future research

Thescopeofthethesisisverywide,andthereforeitspotentialtoad-equatelyanswerallstudyquestionsissomewhatlimited.Muchresearchhastobeperformedinthefuture,beforeasignificantlybetterunder-standingaboutMSD,disabilityandworkwillbeachieved.

ThesystematicreviewonLBPandliftingadvicerevealedthatthereisaneedformoreandbetterqualityresearchwithstandardisedoutcomemeasurement,appropriatepower,andadjustmentfortheclustereffect.Suchstudiesshouldbedirectedata“noliftingpolicy”.Inadditionabetterunderstandingisneededofthecausalchainbetweenexposuretobiomechanicalstressorsatworkandthesubsequentdevelopmentofbackpaintoenablethedevelopmentofnewandinnovativewaystopreventbackpain.

SincemostoftheemployeesinstudiesonUEDandassociatedproductivitylosswerefemaleandworkinginahealthcareorofficeenvironment,thegeneralisationoftheresultsoftheinterventionhastobesomewhatlimited.MoreresearchisneededonproductivitylossandMSDinotherworkenvironments,suchasheavyindustry.

AstheinterventioninstudyIVhadtwoparts,telephonecon-tactwiththesupervisorbythephysicianandworkplacevisitbythephysiotherapist,itisimpossibletodifferentiatewhethertheybothwerecrucialfortheeffectorifone(andwhich)wouldsuffice.Therefore,moreresearchisneededfortoclarifywhichwerethecrucialpartsoftheintervention,butalsoinordertoverifytheresultsindifferentoc-cupationalsettings.

OnecanalwayscriticizethattheresultsofstudiesII–VperformedintheFinnishOHSmaynotbevalidandapplicableinothercountrieswithadifferentkindofsocialsecurityandOHSsystem.Thisisajus-tifiablecriticism,becauseasignificantamountofstudiesonMSDanddisabilityhavebeenperformedincountrieswherethejurisdictionsmake

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adistinctionbetweenwork-relatedMSDandotherMSD.Itisclearthatallsocialsecuritysystemsprobablyhavesomeeffectoninterven-tionsaimedatdisabilitymanagement,butthisshouldnotdiscourageresearchespeciallytryingtotranslatesuccessfulmodelsinonecountryforimplementationinanother.

8.4. Policy implications and recommendations

ThestudiesofthisthesiswereperformedinFinland,withtheexceptionofthestudiesincludedinthesystematicreview(studyI).Inaddition,mostofthestudiesareresultsofcollaborationbetweenFIOHandOHSunits.Therefore,theresultsareapplicabletotheFinnishsocialsecurityandOHcaresystem,andsomeconclusionsaswellasrecommendationscanbemadebasedonthefindings.

Inadditiontopreventiveservices,theFinnishOHScanalsoofferprimaryhealthcarelevelcurativeservicestotheemployees.Thisofferspossibilitiesforbettermanagementofemployeeswithdisabilitiesinadditiontoearlierrecognitionofhealthandsafetyrisksatworkduringmedicalconsultations.Asinhealthcareingeneral,itcanbearguedthatthedisabilitymanagementbyOHphysicianshasbeenmainlybasedonthebiomedicalmodelwithtoolittleemphasisplacedonassociatedwork-related,psychosocialandpsychologicalfactors(fordetailsseechapter2.2.).

TheactivitiesoftheOHSpersonnelshouldbedirectedmoretowardsdisabilitymanagementinordertomeetthedemandsoftheorganisationsandsocietyonOHS.In2005,tertiarydisabilitymanagementservicestoenableandsupportsafeRTWwereavailableinlessthanhalfoftheFinnishOHunits(Kivistöetal.2008).Thecontentsoftheserviceswerebasedonthecurrentscientificevidence,butwithsubstantialvariation.

Theresultsofthisthesischallengethebiomedicalmodelofdisabilitypreventionandmanagement.TheadaptationofbiopsychosocialmodelinthedisabilitymanagementcreatesneedsfortrainingofbothOHSpersonnelandtheworkplaces,aswellasfinancialincentivesfortheem-ployerstoappreciatethevalueandtosupporttheretentionofemployeeswithdisabilities.Whennomedicalcureisattainable,theindividual's

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potentialscanbeidentifiedandsupportedinordertoenablehisorhersuccessfulreturntothemodifiedwork.

MSDaremultifactorialintheirnature,andtherefore,apartfromac-cidentprevention,theirelimination (primaryprevention)bythemeansofwork-relatedinterventionsisnotrealistic.Thereismoreevidenceavailable,towhichthisstudyadds,thatrecognitionofMSDshouldleadtoearlyanalysisofboththework-relatedconsequencesandtheem-ployee'sownperceptionsconcerningthedisorder.InsteadofkeepingtheemployeeoutofworkbecauseofMSD,workactivitiescanbemodifiedandthenegativeconsequencesofthedisorderminimised.

MostcasesofLBPandmanyofUEDarenon-specific,andtheso-called“objective”measuresofpathologyhavebeenpoorinpredictingdisability.Thereisconvincingevidencethatsecondaryandtertiarypre-ventionofdisabilityiseffectiveif,afteradequatemedicalassessment,thebiopsychosocialaspectsofthedisorderandrelateddisabilityaretakenintocarefulconsideration.Workplace,supervisorandcolleaguesshouldbeincludedinthemanagementofdisabilityatanearlierstageifthedisabilityislikelytobeprolonged.AsinstudiesIV–V,thisnecessitatescollaborationandcommunicationnotonlybetweenthecareproviderandtheemployee,butalsoattheworkplacewiththesupervisorandthecolleagues.Thisapproachmostlikelyleadstostrongerinvolvementandgreaterinterestamongsupervisorsinimprovingtheworkenviron-mentandsupporttheemployeewithMSD.Asaconsequence,withanimprovementofthesupervisor'sroleandknowledgerelatedtoMSD,theresultscanbenefitalsoallemployees,withorwithoutsymptoms.

Basedonthefindingsofthisstudythefollowingrecommendationscanbemade

1. Themethodsusedforprimarypreventionofwork-relatedMSDshouldbescrutinised.Inthosecaseswheretheireffectivenessisnotsupportedbyscientificevidence,theresourcesbeingallocatedtothemshouldbedirectedtomoreeffectivemethods.Healthprofessionalsinvolvedintrainingandadvisingworkersonmanualmaterialhan-dlingshouldmodifythecontentssothatnosingleliftingtechniqueisadvocatedforliftingandhandling.Instead,theaimshouldbetoreduceliftinginthefirstplace,andtopreventworkaccidentsrelatedtohandlingheavyobjects.

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2. Thebenefitsofprimary,secondaryandtertiarypreventionofdisabilityaresupportedbycredibleevidence.PreventionofMSDatworkisdif-ficultbecauseoftheirhighprevalenceandcomplexaetiology.However,thereareevidence-basedmethodswhichareabletopreventtherelateddisability.InthesurveillanceofMSDintheOHS,theemployees'ownperceptionsofworkingconditionsandtheireffectsonmusculoskeletalhealthshouldbeusedinsteadofsimplyrelyingonexperts'assessments.

3. Inthesecondarypreventionofdisability,lostproductivityatworkduetoMSDshouldbetakenintoconsideration.ThisisimportantwhensupportingworkerswithMSDincontinuingworking,andwhenundertakingeconomicevaluationsoftheconsequencesofdisabilityatworkandoftheinterventionstoreducethem.Oftensicknessabsenteeism,painorfunctionalstatusmightbetooinsensi-tiveasoutcomestodetectpossiblebenefitsofinterventions.

4. Aprerequisiteforsecondarypreventionofdisabilityisbetterknowl-edgeanduseofalternativemodelsofthebiomedicalapproach.AtOHS,moreeffortsshouldbeplacedonearlyergonomicinterventionsinvolvingboththeemployeesandtheirsupervisorsinsteadofwastingtoomuchtimeinpurelymedicalinterventions.Inthisapproach,thebiopsychosocialmodelofdisabilitymanagementismorelikelytobenefittheemployeethanthebiomedicalmodel.

5. Whenassessingtheworkabilityoftheemployeeandhis/herneedforsickleave,attentionshouldbepaidnotonlytothemedicalcon-ditionbutalsotothepsychosocialandpsychologicalriskfactorsofthedisability.Thisispivotalforrecommendingtheuseofpart-timesickleaveormodifiedworkinsteadoftraditionalsickleaveinthemanagementofMSD.

8.5. Conclusions

ThefivestudiesofthisthesisaimedatansweringfivequestionsrelatedtoMSD,disabilityandwork.• TheresultsofstudyI,asystematicliteraturereview,donotsupport

theuseoftraininginliftingtechniqueswithorwithoutassistivedevicesasawayofpreventingLBPandrelateddisabilityamongworkersfrequentlyexposedtoheavylifting.

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• AccordingtostudyII,MSDareresponsiblemoreoftenforself-assessedpartialworkabilitythanfullinabilitytowork,andworkersmoreoftenthantheirphysiciansassessmanyofthehealthproblemsasbeingcausedorexacerbatedbywork.Self-assessedwork-relatednessofthedisorderisassociatedwithperceiveddisability.

• InstudyIII,workerswhodidnotneedsicknessabsencenonethelessassessedUEDtocausemajorproductivitylossatwork.

• InstudyIV,themanagementofUEDrelatedproductivitylossshowedthatearlyergonomicinterventionattheworkplaceissuperiortomedicalcareonly.

• ThechallengeofdesigninganRCTtostudytheeffectivenessofpart-timesickleaveamongworkerswithMSDwasapproachedintheprotocoldevised instudyV.

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ORIgINAL PUBLICATIONS I–v

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Cover picture: Sami Rantanen

Musculoskeletal disorders, disability and work

People and WorkResearch Reports 89

Kari-Pekka Martimo

Musculoskeletal disorders, disability and w

ari-Pekka Martim

oMusculoskeletal disorders (MSD) are the most important causes of temporary and permanent work disability. The aim of this thesis was to examine the role of work in the disability caused by MSD from various perspectives: primary prevention using lifting advice and devices, perception of work-relatedness, measurement of productivity loss, and secondary/tertiary prevention through ergonomic intervention or part-time sick leave. The original articles include a systematic review, two surveys, a randomised controlled trial, and a study protocol. The results support the early use of a biopsychosocial model for effective management of disability.

Kari-Pekka Martimo - UEF · Kari-Pekka Martimo Musculoskeletal disorders, disability and work...

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