Occupational and Environmental Medicine 1997;54:681-685

Musculoskeletal symptoms and job strain amongnursing personnel: a study over a three year period

Malin Josephson, Monica Lagerstrom, Mats Hagberg, Ewa Wigaeus Hjelm

AbstractObjectives-To examine the variation ofsymptoms from the neck, shoulders, andback over a three year period amongfemale nursing personnel and the relationbetween job strain and musculoskeletalsymptoms.Methods-At a county hospital the femalenursing personnel answered a question-naire at baseline and then once a year overa period of three years. There were 565,553, 562, and 419 subjects who answeredthe questionnaire at the first, second,third, and fourth survey, respectively. Ofthe study group, 285 nursing personnelanswered the questionnaire on four occa-sions. Ongoing symptoms of the neck,shoulders, and back were assessed bymeans of a 10 point (0-9) scale with theverbal end points "no symptoms" and"very intense symptoms." Cases weredefined as nursing personnel reportingongoing symptoms, score >6, from at leastone of the body regions. For assessmentsofjob strain, a Swedish version ofKarasekand Theorell's model was used.Results-Of the 285 subjects, 13% weredefined as cases at all four assessments,and 46% varied between cases and notcases during the study period. In therepeated cross sectional surveys the esti-mated rate ratio (RR) for being a case wasbetween 1.1 and 1.5 when comparing thegroup with job strain and the group with-out job strain. For the combination of jobstrain and perceived high physical exer-tion the estimated RR was between 1.5 and2.1. When the potential risk factors wereassessed one, two, or three years beforethe assessment ofsymptoms the estimatedRR for becoming a case was between 1.4and 2.2 when comparing the group withjob strain and the group without jobstrain.Conclusion-Almost halfofthe healthcareworkers varied between being a case andnot, over a three year period. The analysisindicated that job strain is a risk factor formusculoskeletal symptoms and that therisk is higher when it is combined withperceived high physical exertion.

(Occup Environ Med 1997;54:681-685)

Keywords: nursing personnel; musculoskeletal symp-toms; job strain

An association between psychosocial job fac-tors and musculoskeletal disorders has beenshown in several studies.' 7Theorell et at foundthat high mental demands were associated withself reported muscle tension and musculo-skeletal symptoms. In a cross sectional studyamong homecare workers an association be-tween low decision latitude and symptomsfrom the neck, shoulders, and low back wasfound. For those with a high physical load theassociation was strengthened.9The combination of high mental demands

and low decision latitude, job strain, has beenpointed out as an important factor, both forcardiovascular diseases and also for othernegative health outcomes."0 In a cross sectionalstudy among men and women employed indifferent occupations, job strain was associatedwith musculoskeletal symptoms." A recentlypublished cross sectional study among health-care workers indicated an association betweenjob strain and low back symptoms.'2Most investigations of the association be-

tween job factors and musculoskeletal symp-toms have been cross sectional. In crosssectional studies the information on job factorsand symptoms are assessed at the same point intime and the direction of the association is notclear. The self reported assessment of potentialrisk factors for musculoskeletal symptoms maybe affected by self reporting biasing factors.Subjects with symptoms may overreport thepoor job factors and those with no symptomsmay underestimate the exposure. " Further-more, musculoskeletal symptoms may in-crease, decrease, or pass off.'4 The variability ofsymptoms is an important factor when design-ing, conducting, and interpreting epidemio-logical studies.The first aim of this study was to investigate

the variation ofmusculoskeletal symptoms overa three year period. How large is the turnoverfrom symptoms to no symptoms, and viceversa, in yearly repeated surveys? The secondaim was to investigate the relation between jobstrain and muskuloskeletal symptoms. Will anassociation be found both if all data arecollected at the same point in time and whenthe job factors are assessed before the assess-ment of symptoms?

Subjects and methodsAn education and training programme forhealthcare personnel was performed at acounty hospital in the north of Sweden.'5 Allpersonnel on wards with patients who requireddaily care-for example, help to move from thebed to a chair and daily hygiene, participated in

Department ofErgonomics, NationalInstitute for WorkingLife, S-171 84 Solna,SwedenM JosephsonM LagerstromM HagbergE Wigaeus Hjelm

Division ofOccupational Medicineat Karolinska Institute,Huddinge UniversityHospital, S-141 86Huddinge, SwedenM Josephson

Correspondence to:Dr Malin Josephson,Division of Ergonomics,National Institute forWorking Life, S-171 84Solna, Sweden.

Accepted 24 March

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the programme. The personnel were educatedfor one day once a year in patient transfer tech-nique, physical fitness exercise, and stressmanagement. The registration to the pro-gramme was made collectively for all personnelat one ward.The participants in the education and train-

ing programme completed a self administeredquestionnaire once a year. At the first threeassessments the subjects completed the ques-tionnaire before the yearly course day. At thefourth assessment, the subjects filled in a ques-tionnaire without a subsequent course. Thestudy period was 1991-4; thus it was threeyears between the first and the fourth assess-ment.At the repeated cross sectional surveys, the

data analysed were based on 565, 553, 562, and419 subjects, respectively. Non-nursing malepersonnel were excluded from the study groupbecause they were so few. Two participantsrefused to fill in the questionnaire at the firstsurvey. At the first, second, third, and fourthassessments, 16, 17, 15, and 16 subjects,respectively did not answer the questions con-cerning ongoing musculoskeletal symptomsand were dropped from the analysis. Thedecrease in number of subjects in the lastassessment compared with the years before wasmainly due to changes of working places, reor-ganisations, and staff cuts. Because of turnoverof personnel, retirement, child care leave,notices of leaving, and staff cuts, only 50% ofthe initial study group (285 workers) answeredthe questionnaire four times; the first, second,third, and fourth assessments. The first crosssectional survey is referred to as the baselineassessment.

Questionnaires were distributed by theOccupational Health Service.Name and department were preprinted on

the questionnaires. The questionnaires con-tained about 100 questions on individualfactors, physical exposure at work, psychoso-cial factors, patient handling, and musculo-skeletal symptoms.Most of the participants were employed as

registered nurses (table 1). Of the workers,70% were working a shift schedule involvingdays, evenings, and weekends, 22% workedonly night shifts. The work involved three ormore patient transfers per working day for 77%of the subjects. The wards were well equippedwith modern lifting devices. All patients' bedswere equipped with draw sheets and plastic,which were used for patient transfers in thebed. For patient transfers between the bed anda trolley or a wheelchair, hoists fixed to the

Table 1 The study group

OthersRegistered State Auxiliary (assistants Mean Frequency

Repeated cross nurses enrolled nurses and pupils) age B 45 yearssectional surveys n (/O6) nurses (0o) (0o) ('/o) (y)(0%)

First 565 39 35 25 2 40 37Second 553 41 34 23 2 42 43Third 562 42 37 19 2 42 45Fourth 419 44 39 13 5 43 49Closed cohortBaseline (first

survey) 285 47 32 19 2 43 49

ceiling or separate hoists were used. The hoistswere constructed with a U shaped sling whichwas put under the patients during the transfers.

SYMPTOMS

Neck, shoulder, and back symptoms wereassessed by a modified version of the Nordicmusculoskeletal questionnaire. The itemswere "Have you had any symptoms in the past12 months?" and "Do you have any ongoingsymptoms?". The question about symptomsduring the past 12 months had two responsealternatives: yes and no. Ongoing symptomswere assessed by a 10 point (0-9) scale with theverbal end points "no symptoms" and "veryintense symptoms". Cases were defined asnursing personnel who reported ongoingsymptoms, score >6, from at least one of thebody regions.

JOB STRAINFor assessments of job strain a Swedish versionof Karasek and Theorell's model was used.'0 17The index of "mental demands" included fiveitems: excessive work, conflicting demands,time to do work, fast and hard work; score vari-ation 5-20, the higher the score the higher thedemands. "Decision latitude" included sixitems: learning new things, high levels of skilland creativity, repetitious job, and authority todecide what to perform and how to perform thejob; score variation 6-24, the lower the score,the lower the decision latitude. The Cronbacha coefficient was used for estimating the inter-nal consistency among the questions. Thecoefficient can be interpreted as a correlationcoefficient, it ranges in value from 0 to 1.'" Forthe demand index the coefficient was 0.69 and0.51 for decision latitude. The internal consist-ency for decision latitude can be considered aslow, which may lead to an underestimation ofthe association with musculoskeletal symp-toms.High demands were defined as a score >14

(the highest 30%), based on the first survey,low decision latitude as a score < 16 (the lowest37%), based on the first survey. The combina-tion of high mental demands and low decisionlatitude was defined as job strain.

PERCEIVED EXERTIONA modified scale that rated perceived exertionwas used to assess perceived physical exertionduring a normal working day.'9 20 The rangewas set from 0, resting, to 14, maximalexertion. In the first survey, 66% rated up tohard (score <8) and 21% rated hard (score=9)perceived physical exertion. High exertion,defined as a score >10, was reported by 13%.

TREATMENT OF DATAIn the repeated cross sectional analysis thestudy group was dynamic-that is, all employ-ees answering the questionnaire on each occa-sion were included in the analysis. In the followup analysis the study group was a closedcohort; no employees entered the study group.The turnover from case to non-case, or fromnon-case to case, between baseline and the one,two, and three years of follow up were assessed.

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Table 2 Prevalence of neck symptoms, shoulder symptoms,upper back symptoms, lower back symptoms and symptomsfrom at least one of the body regions

Episodes of Ongoing Ongoingsymptoms the symptoms, symptoms,past 12 score 2-9 score 6-9

Body region months (%o) (Oo) (%o)

Neck 53 40 18Shoulders 60 50 20Upper back 30 24 8Lower back 64 49 16Neck, shoulders, upper

back, lower back 84 69 33

Ongoing symptoms from the neck, shoulders, and back wereassessed by means of a 10 point (0-9) scale: first survey, n=565.

In the cross sectional analysis the risk factorsand the symptoms were reported at the samepoint in time. In the follow up the symptomswere assessed one, two, and three years afterthe potential risk factors were assessed. Con-sidered as potential risk factors were age (¢45years or <45 years), occupation (not registerednurse or registered nurse) patient transfers ( ¢ 3per working day or <3 per working day), highphysical exertion, and job strain. In the crosssectional analysis the rate ratio (RR) was usedto describe the relative occurrence of casesbetween exposed and unexposed nurses. In thefollow up analysis RR was used to describe therelative occurrence of cases at the time for thefollow up between exposed and unexposednurses at baseline. In the follow up analysis allsubjects defined as cases at baseline wereexcluded.The data were divided into subgroups to

consider modification of effect, and to controlfor confounding. Mantel-Haenszel weightedstatistics were calculated to combine thesubgroup specific estimated RR into a singleoverall estimate.' Because of missing data,numbers varied between estimates of theprevalence and the estimated RR.

ResultsSYMPTOMSThe prevalence of symptoms at the first surveyvaried according to the definition and the bodyregions (table 2). The prevalence of episodes ofsymptoms during the past 12 months was10%-15% higher than with ongoing symp-toms, score 2-9 (table 2). The highestprevalence, 20%, for ongoing symptoms, score>6, was for shoulder symptoms (table 2).Ongoing neck or shoulder symptoms, score >6,and no symptoms from the back were reportedby 13% of nurses, 10% reported only backsymptoms, and 10% reported neck, shoulder,and back symptoms.

Table 3 Prevalence of cases * in cross sectional surveysrepeatedyearly

Prevalence of Prevalence ofCross sectional Subjects in cases in the cases in thesurveys repeated the repeated repeated closed cohortyearly surveys (n) surveys (%o) (n285) (%o)

The prevalence of cases, defined as nursingpersonnel reporting ongoing symptoms, score

>6, from at least one of the body regions, was

stable at the four assessments (table 3). In therepeated cross sectional surveys the prevalenceof cases was between 33% and 36%, and in theclosed cohort between 34 and 35% (table 3). Inthe closed cohort, 13% were defined as cases at

all four assessments, 46% varied between cases

and non-cases, 41% were defined as non-cases

at all four assessments. If the definition hadbeen a rating between two and nine, 36%would have varied between cases and non-

cases, 27% varied between reporting episodesof symptoms during the past 12 months or not.The frequency of turnover from case tonon-case or vice versa, was 10%-14% betweenbaseline and the one, two, and three year followup, (table 4). Of those who were defined as

cases at baseline, 69% were defined as cases atthe one year follow up, 62% at the two year fol-low up, and 67% at the three year follow up.

POTENTIAL RISK FACTORSAt the first survey, 13% reported high physicalexertion, 18% at the fourth survey, 10%reported job strain at the first survey, 20%three years later. Of those who reported highphysical exertion at the first survey, 54%(33/61) also reported high mental demands,and 30% (18/61) reported job strain. Thecombination ofno patient transfers at work andhigh exertion was only reported by one subject.The highest associated with being a case was

the combination of job strain and high physicalexertion (table 5). In the repeated cross

sectional surveys the estimated adjusted RR forbeing a case was between 1.1 and 1.5 whencomparing the groups with and without jobstrain (table 6). When comparing the highexertion group with the others, the estimatedadjusted RRwas between 1.4 and 1.8 (table 6).For the combination of job strain and exertionthe estimated RR was between 1.5 and 2.1(table 6).

In the follow up analysis the estimated RRfor becoming a case was between 1.4 and 2.2when comparing the groups with and withoutjob strain (table 7). When comparing the highexertion group with the others the estimatedRR was between 1.3 and 1.6 (table 7). Onlyone subject in the closed cohort reported jobstrain, high perceived exertion, and no symp-

Table 4 Frequency of cases * both at baseline and at thefollow upfrequency that became cases, andfrequency thatbecame non-cases at the one, two, and three yearfollow ups,n=285

Frequency FrequencyFrequency of that became that becamecases both at cases at the non-cases at

baseline and at follow up the follow upthe follow up assessment assessment

Years assessment (%,) (0Io) (°/0)

Baseline, 1 yearfollow up 24 12 10

Baseline, 2 yearfollow up 2 1 14 13

Baseline, 3 yearfollow up 23 13 12

* Cases were defined as nursing personnel reporting ongoing *Cases were defined as nursing personnel reporting ongoing

symptoms, score B 6 from at least one of the body regions. symptoms, score ¢ 6 from at least one of the body regions.

First survey 565 33 34Second survey 553 35 35Third survey 562 36 35Fourth survey 419 36 35

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Table 5 Estimated crude RRfor being a case. * (Based on data from the first survey)

Frequency Frequency ofexposed cases exposed

Potential risk factor n (%o) (%o) RR (95% CI)

Age (> 45y) 565 37 43 1.3 (l.Oto 1.6)Occupation (not registered nurse) 565 61 67 1.2 (1.0 to 1.6)Transfers (> 3/working day) 565 77 77 1.0 (0.8 to 1.3)Physical exertion (rating >hard) 565 13 20 1.7 (1.3 to 2.3)Job strain (demands score > 14,

decision latitude score < 16) 505 10 16 1.7 (1.2 to 2.4)Job strain and physical exertion 505 4 8 2.3 (1.4 to 3.6)

*Cases were defined as nursing personnel reporting ongoing symptoms, score > 6, from at leastone of the body regions.

Table 6 Cross sectional surveys repeated yearly: estimated adjusted RRfor being a case*with the potential risk factorjob strain (demands score ¢ 14, decision latitude score S 16)

Cross sectional surveys Frequency of Frequency exposedrepeated yearly n exposed (o/6) of the cases (s0o) RR(95% CI)t

First 505 10 17 1.5 (1.1 to 2.1)Second 506 11 15 1.1 (0.8 to 1.6)Third 506 16 24 1.5 (1.2to 2.0)Fourth 372 18 21 1.1 (0.8to 1.6)Physical exertion (>hard) RR (95% CI)tFirst 505 12 19 1.5 (1.1 to2.1)Second 506 15 23 1.5 (1.2 to 2.1)Third 506 16 24 1.4 (1.1 to 1.8)Fourth 372 20 31 1.8 (1.4to 2.4)Job strain and physical

exertiont: RR (95% CI)§First 505 4 8 2.1 (1.4 to 3.3)Second 506 4 8 2.0 (1.3to 3.0)Third 506 6 9 1.5 (1.Oto 2.3)Fourth 372 6 10 1.6 (l.Oto 2.5)

* Cases were defined as nursing personnel reporting ongoing symptoms, score > 6, from at leastone of the body regions.t Adjusted for age, occupation, and physical exertion by the method of Mantel Haenszel.t Adjusted for age, occupation, and job strain by the method of Mantel Haenszel.§ Adjusted for age and occupation by the method of Mantel Haenszel.

Table 7 Follow up analysis: estimated RR *for becoming a case at the one, two, or threeyearfollow ups

Frequency RR (95% CI) for RR (95% CI) forthat became becoming a case when becoming a case whena case at the comparing the groups with comparing high with

Year follow up and withoutjob strain not high exertion group

Baseline, 1 year follow up 19% 2.2 (0.8 to 6.0) 1.3 (0.5 to 3.3)Baseline, 2 year follow up 22% 1.4 (0.5 to 4.0) 1.4 (0.6 to 3.3)Baseline, 3 year follow up 24% 1.5 (0.6 to 3.5) 1.6 (0.8 to 3.4)

Those who were defined as cases at the baseline were excluded from the analysis: the potential riskfactors were assessed at the baseline; n= 172.* RR adjusted for age and occupation by the method of Mantel Haenszel.t Cases were defined as nursing personnel reporting ongoing symptoms, score ¢ 6, from at leastone of the body regions.

toms in the baseline assessment. No follow upanalysis concerning the combination of per-ceived exertion and job strain could beconducted.

DiscussionSTUDY GROUPWhen generalising from this study it is impor-tant to note that the study period was adynamic time at the hospital. An education andtraining programme for the employees wasongoing and also the healthcare system wasreorganised, leading to staff cuts at thehospital. An evaluation of the training andeducation programme has been presented else-where and was not the aim of this study.'5The proportion of nursing personnel who

reported job strain increased over the threeyear period. The increased prevalence of jobstrain may have been associated with staff cuts,

reorganizations, and new work requirements.There was no difference in the frequency ofsymptoms at the first survey between the groupwho ended their employment and those whoremained in the study.

SYMPTOMSThe prevalence of ongoing symptoms was sta-ble over the study period. In the closed cohortthe proportion who developed new symptomswas the same as the proportion who recoveredfrom symptoms. Almost half of the nursingpersonnel varied between being a case or notduring the study period. The case group wasnot stable either if the definition of cases wasongoing symptoms or if the definition was epi-sodes of symptoms the past 12 months. A casedefinition of absence from work due tomusculoskeletal symptoms might have pro-duced different prevalence and associations.'4The cases in this study were healthy enough towork although they reported ongoing symp-toms. The symptoms reported may not havebeen known to the occupational healthcareservice, or the employers, or may not have ledto absence from work. A high proportion of thecases had both neck or shoulder symptoms andsymptoms from the back. A larger study groupwould have been necessary if the intentions hadbeen to separate the risk factors for neck orshoulders and the back.

RISK ANALYSIS

Job strain can be assessed by different methods.In the present study each subject answeredquestions and was given a score of demandsand decision latitude. According to this twodimensional model job strain occurs when thedemands are high and the decision latitude low.The Cronbach a coefficient for the indices wasrather low. It has been proposed that specificindex construction may be necessary for thehealthcare sector. Working with human suffer-ing and sickness involves special psychologicalwork factors and requirements.22 Job demandsin nursing are probably a mix betweenphysically demanding job tasks and mentaldemands. In occupations involving care andpatient handling perhaps the perception ofmental and physical demands are hard to sepa-rate. Transferring a patient, who may be old,confused, and anguished, involves both physi-cal and mental requirements.

All nursing personnel in the study wereworking in the same hospital and with patientswho required daily care. The participants hadrather similar work: taking care of peoplerequiring health care. The demands anddecision latitude model has been mainly devel-oped for the purpose of comparing differentoccupations. The individual biasing factorsbecome stronger when comparing people inthe same work sector.'0 23 If the average ratingfor a specific occupational group is used, theimportance of individual biasing factors de-creases. To reflect differences between peoplein the same occupation it would be useful todevelop more precise questions about thework. The questions used are rather general.Furthermore, psychosocial job factors involve

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more dimensions than just demands and adecision latitude.24 Many of the women in thestudy group were threatened by reorganisa-tions and unemployment. However, the assess-ments did not reflect this.

Perceived physical exertion was assessed byone item in the questionnaire. The questionwas intended to assess perceived physical exer-tion, but may have reflected a mix of physicaland psychological work factors. Reporting highexertion was associated with whether or not thework involved patient transfers, but also withreported mental demands. According to previ-ous studies cardiovascular load or individualphysical capacity were probably not reflectedby the modified scale that rated perceived exer-tion used as an item in the questionnaire. 25The cross sectional analyses provides infor-

mation about the association between jobfactors and symptoms. During the data processboth univariate and multivariate analyses wereconducted. To facilitate interpretation, strati-fied univariate analyses and weighted estimatesof RR were presented in the paper. In crosssectional studies of musculoskeletal symptomsit has been recommended not to estimate theRR by logistic regression.26 The high preva-lence of musculoskeletal symptoms and theinfluence of exposure on the duration of theproblems make the interpretation of the oddsratio uncertain and difficult. Our longitudinaldata examined if those who reported relativelypoor job factors one, two, or three years agomore often reported ongoing musculoskeletalsymptoms. The analyses of the follow up dataare simplistic partly because of the studydesign. The data are collected once a year andthere is no information about the exposure fac-tors or the symptoms between the assessments.The estimated RR can hardly be translated to arisk for getting symptoms, just a risk to reportsymptoms at a special point in time.The association between job strain and

symptoms was clear in the baseline assessmentand in the survey two years later. In the secondand fourth surveys the association was moreuncertain. If only the first survey had been per-formed, the conclusion would have been arather strong association between job strainand ongoing symptoms. Had we only done thestudy a year later, our conclusion would havebeen more uncertain. In the follow up, the 95%confidence intervals were wide, but there was atendency to an association.

Different models of the pathways betweenpsychological job factors and musculoskeletalsymptoms are possible. The work technique inthe case of patient transfers may decrease whenthe employees perceive job strain and highexertion, and this may lead to increased load onthe musculoskeletal system. Furthermore, themuscle tension may increase when the employ-ees perceive job strain, or the job strainincreases the perception of symptoms.2

ConclusionAlmost half of the healthcare workers variedbetween being and not being a case over a threeyear period. The analysis indicated that job

strain is a risk factor for musculoskeletal symp-toms and that the risk is higher when it is com-bined with perceived high physical exertion.

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