Shift Work: Health, safety and social effects a case of ...dspace.sctimst.ac.in/jspui/bitstream/123456789/2165/1/MPH_5990.pdf · Mrs.Jayanthi Bai, administrator, KMML. I am indebted

i

Shift Work: Health, safety and social effects

a case of rapidly rotating schedules

among male industrial workers

Dr. Anoop Velayudhan

Dissertation submitted in partial fulfillment of the requirements for

the award of the degree of

Master of Public Health

Achutha Menon Centre for Health Science Studies

Sree Chitra Tirunal Institute for Medical Sciences and Technology

Thiruvananthapuram, Kerala.

October 2011

ii

Acknowledgements

I extend my heartfelt gratitude to Dr.K.RThankappan , Dr.Sundari Ravindran,

Dr.V.Raman Kutty, Dr.Sankara Sarma , Dr.Mala Ramanathan , Dr. Kannan Srinivasan ,

Dr.Biju Soman, Dr.Manju Nair and Dr.Ravi Prasad Varma. I could see so far, only because I

stood on the shoulders of these giants.

I would like to thank my guide Dr.Ravi Prasad Varma, who put up with all my

idiosyncrasies and mistakes. In the language of this thesis‘s subject, he has always awakened

me when I was asleep, directed me whenever I was clueless, consoled me when I was

confused, and also asked me to rest and sleep when I was weary. He has never accepted

anything less than my best efforts.

This thesis owes its existence to Dr. Mohandas, Occupational Health specialist at

Travancore Titanium, who brought my attention to the problems of shift work, the need and

potential of research in it.

I would like to thank Dr.Ashalatha for giving me her time, technical help and

encouragement during this study. I thank Sunitha for teaching me the neuropsychology tests

and Dr.Ailey Alexander for discussing them with me.

I thank the management and staff of Kerala Minerals and Metals Ltd and also

Travancore Titanium for allowing me to conduct this study there. I am indebted to

Mrs.Bindu, administrator, Travancore Titanium, Dr.Bipin Pillai Medical Superintendent, and

Mrs.Jayanthi Bai, administrator, KMML.

I am indebted to Kerala State Council for Science Technology and Environment who

provided partial funding for this research and made my expenses, thus bearable.

I am grateful to all the workers who participated in this study and helped me during

the course of survey. They have taught me lessons about life in 3 months than I could have

learnt on my own in 3 years.

This thesis would not have been possible without the support of all my friends at

Achutha Menon Centre for Health sciences. Thanks to them, I found joy in every moment, in

the last two years. I am indebted to Dr. Ashish Anand, a dear friend and philosopher who

spared his time and best efforts to read and correct this work, while mending broken bones.

At last, I thank my family for their love, care and for simply being there for me, no

matter what. My parents and wife have been my ultimate strength and love. My Uncle

Mr.Aundeeshwaran, my brother and sister along with my friends helped me in various stages

of work and encouraged me to push myself further. I thank them too.

iii

Certificate

I hereby certify that the work embodied in this dissertation entitled ―Shift

Work: Health, safety and social effects-a case of rapidly rotating schedules

among male industrial workers‖ is a bona fide record of original research work

undertaken by Dr. Anoop Velayudhan, in partial fulfillment of the requirements

for the award of the degree of ‗Master of Public Health‘ under my guidance and

supervision.

Dr.Ravi Prasad Varma P

Assistant Professor

Achutha Menon Centre for Health Science Studies,

Sree Chitra Tirunal Institute for Medical Sciences and Technology,


28th October, 2011.

iv

Declaration

I hereby declare that the work embodied in this dissertation entitled ―Shift

Work: Health, safety and social effects-a case of rapidly rotating schedules

among male industrial workers‖ is the result of original research and has not

been submitted for any other university or institution.

Dr. Anoop Velayudhan, MPH-2010,

Achutha Menon Centre for Health Science Studies,

Sree Chitra Tirunal Institute for Medical Sciences and Technology,


28th

October, 2011.

v

TABLE OF CONTENTS

CHAPTERS

LIST OF TABLES

LIST OF FIGURES

ABSTRACT

CHAPTERS

Number Chapter Name Page No

1 Introduction 1

2 Literature review 2

2.1 Definition of shift work sleep disorder 2

2.1.1 Circadian rhythm disorders 2

2.1.2 Shift work 3

2.1.3 Shift work sleep disorder 3

2.2 Magnitude of problem 5

2.2.1 Public health importance 5

2.2.2 Reasons for shift work 6

2.2.3 Prevalence of shift work sleep disorder 6

2.3 Biomedical theory-Normal sleep and shift work sleep

disorder 10

2.3.1 The circadian system 11

2.3.2 Types of circadian rhythm disturbances 13

2.3.3 Shift work sleep disorder 14

2.4 Diagnostic and therapeutic features 15

2.4.1 Diagnosis 15

vi

2.4.2 Differential diagnosis 16

2.4.3 Treatment 16

2.5 Impact of shift work sleep disorder 17

2.5.1 How shift work affects health 17

2.5.2 Gastrointestinal disorders 18

2.5.3 Cardiovascular disorders 19

2.5.4 Mental health 20

2.5.5 Accidents 20

2.5.6 Social and domestic problems 20

2.5.7 Cognition and executive functions 21

2.6 Prognosis 21

2.7 Current recommendations 22

2.8 Rational of study 22

2.9 Research question 23

2.10 Objectives 23

3 Methodology 24

3.1 Study design 24

3.2 Cross sectional study 24

3.2.1 Study setting 24

3.2.2 Sampling unit 24

3.2.3 Sample size 24

3.2.4 Sample selection 24

3.2.5 Inclusion and exclusion criteria 25

3.2.6 Data collection 25

3.2.7 Data storage 27

vii

3.2.8 Data entry, analysis and statistical measures 27

3.2.9 Variables used in the study 27

3.2.9.1 Dependent variables 27

3.2.9.2 Independent variables 29

3.3 Ethical Considerations 29

3.3.1 Risk to participants 29

3.3.2 Privacy and confidentiality 30

3.3.3 Benefits 30

3.3.4 Informed consent process 30

3.3.5 Funding 31

4 Results

4.1 General description of survey outcome 32

4.2 Univariate analysis -Demographic description of study

subjects 32

4.3 Bivariate analyses 32

4.3.1 Types of shift cross tabulated against

morbidities and co-morbidities 35

4.3.1.1 Sleep disorders 35

4.3.1.2 Symptoms suggestive of Gastro

intestinal, cardiovascular and

mental health status of workers 37

4.3.1.3 Occupational health issues 38

4.3.2 Associations of insomnia or Excessive

sleepiness with various factors 41

4.4 Multivariate analysis 46

4.5 Clinical tests 48

viii

5 Discussion and conclusion 52

5.1 Discussion 52

5.1.1 Relation of work schedule with sleep-

Prevalence of insomnia or excessive

sleepiness 52

5.1.2 Shift work and its correlations 53

5.1.3 Insomnia or Excessive Sleepiness and its

correlations 54

5.1.4 Clinical tests 55

5.2 Strength and Limitations 57

5.3 Conclusions 58

ix

List of Tables

Table No. Title Page no

1 Mean age, BMI, years in service of workers 33

2 Age of workers segregated into five year age groups 34

3 Marital status and Habits of workers 35

4 Insomnia, Excessive Sleepiness and Insomnia or Excessive

sleepiness among workers

37

5 Symptoms suggestive of health problems among workers 38

6 Health problems(self reported) among workers 39

7 Accidents ,injuries and job satisfaction among workers 40

8 Social and domestic situation among workers 41

9 Bivariate analysis-Associations of Insomnia or Excessive

sleepiness

42


sleepiness

43


sleepiness

44


sleepiness

45

13 Multivariate analysis-factors associated with insomnia or

excessive sleepiness-Model 1

46



47



47

16 Clinical test scores among workers-RAVLT 49

17 Repeated Measures anova test of five rounds of RAVLT 50

18 Clinical test scores among workers-Trail A, Trail B and Digit

span

51

x

List of Figures

Figure no. Title Page

1 Entertainment of sleep wake cycle by light. 11

2 A The Normal sleep cycle 12

2 B Sleep cycle in a shift worker 13

3 Conceptual framework :Disease mechanisms in shift

work

18

xi

ABSTRACT

Background: This study was designed to examine the effects of shift work on the health and

lives of Industrial workers and to ascertain the prevalence of shift work sleep disorders and to

find its associations

Methods: It is a cross sectional study using self administered questionnaires.482 male

industrial workers of age > 18 years with mean age, participated in the study. Demographic

variables and work related factors were collected. General Job satisfaction, Insomnia scores,

Epworth Sleepiness score, and the Standard shift work Index were used to capture general

health, social and domestic situations. Clinical tests were done on a subset of the workers (30

regular and 30 shift worker) .Data was entered during Epidata ver 3.1 and analyzed using

spss ver.17

Results: Age adjusted prevalence of Insomnia or Excessive sleepiness among Shift workers

is 33.79% and Age adjusted prevalence of Insomnia or Excessive sleepiness among Regular

workers is 12.59%.Sleep disorder (insomnia or excessive sleepiness ) among workers. Work

schedule and Angina were found to be significantly associated with Sleep disorder (insomnia

or excessive sleepiness).Shift workers were found to be 2.71 times more likely to be

associated with sleep disorder, than their regular work counterparts (95% CI=1.58-4.66).Also

workers with Self reported Angina were 1.07 times more likely to be having Sleep disorder

(95% CI 1.08-6.13) than those without self reported angina.

Fewer shift workers reported that their work schedule interfered with domestic things

to do (45.7%) compared to regular workers (56%).Fewer shift workers (39%) than regular

work mates (60.1%) reported that their work interfered with non domestic things to do.

Contrary to expectation, accidents were lesser among shift worker (3.9%) than regular

workers (11.9%)

Shift work seems to affect memory (both immediate and delayed) among workers, as

suggested by Ray‘s Auditory Verbal Learning test, done among other neuro psychological

test

1

CHAPTER 1.INTRODUCTION

"And God divided the light from the darkness, and God called the light day, and the darkness

He called night. And the evening and the morning were the first day‖ (Genesis 1:4–5, King

James Version).

Under normal circumstances, the synchronization of our inherent time rhythms with

each other and with environmental rhythms (external time cues) maximizes our waking and

sleeping performance and promotes overall well-being. Unfortunately ‗Night work‘ or

working at night is opposed to the innate drive to sleep at night and work during the daytime.

Shift work in general and rotating work schedules commonly known as shift

schedules, causes disruption of biological rhythms, which is called circadian

desynchronization. The effects of such erratic work schedules are various. It has a negative

influence on performance efficiency, health and social well-being. It also makes

concentration difficult, which increases the possibility of errors or accidents-a risk both to the

worker and to the public. It causes disturbance of gastrointestinal systems and elevated risk of

cardiovascular disease. A shift work schedule affects not only the worker but also his family,

due to the different time table a shift worker follows, thus debilitating his personal life.

The importance of sleep can never be underscored and effects of its deprivation never

fully comprehendible. The problems of shift workers are the major focus here. Sans sleep,

sans health, sans safety shift workers are specifically denied of the tender loving care of the

universal physician as Sophocles described.

"Sleep, thou patron of mankind, Great physician of the mind who does nor pain nor sorrow

know, Sweetest balm of every woe."

2

CHAPTER 2. LITERATURE REVIEW

Literature regarding shift work and shift work sleep disorder was searched for in

books, journal articles and textbooks of sleep medicine and of neurology. The internet was

the predominant medium used. Journal publications, research papers, theses were referred to

understand and correlate available facts and nuances of the problem. Formatively, goggle

search yielded figures, report and other newspaper and grey literature on shift work and sleep

deprivations. For legitimate articles, PubMed repository was searched using MeSH term for

Shift work sleep disorder which was-―Sleep disorder, Circadian Rhythm‖.1048 article were

found on Pub Med (305 full free text,95 reviews).

The following themes were prepared to guide specific facets regarding the interest of

research and review shall also be written along the same lines.

A) Definition of Shift work Sleep Disorder

B) Magnitude of problem (Public Health importance, global and national

scene)

C) Biomedical theory-Normal sleep cycle and Shift work disorder

D) Current Diagnostic and Therapeutic techniques

E) Dynamics of Problem-determinants and associations

F) Impact of Shift work disorder-on Health, its Economical & Social consequences

G) Prognostic factors

H) Recommendations

2. 1. Definition of Shift work Sleep Disorder

2.1.1. Circadian rhythm disorders:

The twenty four hour intrinsic rhythm of the body is called circadian system. It exerts

a powerful influence, directly through its regulation of metabolism, and indirectly through its

3

interference or promotion of sleep. Disorders of sleep that arise as a result of disruption of

this rhythm are called circadian rhythm sleep disorders.1

Circadian rhythm sleep disorder can result from alterations in the endogenous

circadian clock (delayed sleep phase [DSP], advanced sleep phase [ASP], free running type,

and irregular sleep-wake cycle) or changes in the physical environment in relation to the

endogenous clock (shift work disorder and jet lag).2In most circadian disorders, the problem

is that the patient cannot sleep when sleep is desired, needed, or expected. As a result of sleep

episodes occurring irregularly, the corresponding wake periods may occur at undesired times.

Consequently, the patient complains of Insomnia or Excessive Sleepiness (ES).1 Today, large

proportions of the population in any nation have work schedules that interfere with night

sleep and therefore have people suffering from disturbed sleep and excessive sleepiness .3

However, sleep disorders connected with shift work have not received much clinical

attention despite the fact that the severity of the sleep impairment in shift and night work is as

high as that in traditional insomnia and seems to affect three fourths of those who work shifts

or at night.4

2.1 2. Shift work:

Shift work as per the standard definition, itself is defined as essentially involving

hours of employment during non-standard or alternative hours, i.e., work outside of the

typical day schedule of 8 a.m. to 5 p.m.5

2.1.3. Shift work sleep disorder:

Shift work sleep disorder or shift work disorder (SWSD or SWD) is defined by the

International Classification of Sleep Disorders as consisting of symptoms of insomnia or

4

excessive sleepiness that occur as transient phenomena in relation to work schedules (ICSD

category 307.45-1).1The work is usually scheduled during the habitual hours of sleep (i.e.,

shift work–rotating or permanent shifts), roster work, or irregular or undetermined hours of

work. The sleep complaint typically consists of an inability to maintain a normal sleep

duration when the major sleep episode is begun in the morning (6 a.m. to 8 a.m.) after a night

shift. The reduction in sleep length usually amounts to one to four hours. Subjectively, the

sleep period is perceived by the worker as unsatisfactory and not refreshing. The insomnia

appears despite the patient‘s attempts to optimize environmental conditions for sleep. The

condition usually persists for the duration of the work-shift period. Excessive sleepiness

usually occurs during shifts (mainly night) and is associated with the need to nap and is

associated with impaired mental ability because of the reduced alertness.

The Diagnostic and Statistical Manual of Mental Disorders-IV defines shift work

sleep disorder as ‗‗report of difficulty falling asleep, staying asleep, or non-restorative sleep

for at least one month‘‘ and it must be associated with ‗‗a work period that occurs during the

habitual sleep phase.‘‘ There are also required effects on impairment of wakefulness.

ICSD gives the Diagnostic Criteria for Shift Work Sleep Disorder (307.45-1) as

A. The patient has a primary complaint of insomnia or excessive sleepiness.

B. The primary complaint is temporally associated with a work period (usually night work)

that occurs during the habitual sleep phase.

C. Polysomnography and the MSLT demonstrate loss of a normal sleep-wake pattern (i.e.,

disturbed chronobiologic rhythmicity).

D. No medical or mental disorder accounts for the symptoms.

E. The symptoms do not meet criteria for any other sleep disorder producing

insomnia or excessive sleepiness (e.g., time-zone change [jet lag] syndrome).

5

Severity Criteria:

Mild: Mild insomnia or mild excessive sleepiness, the sleep deficit is often one to two hours.

Moderate: Moderate insomnia or moderate excessive sleepiness, the sleep deficit is often two

to three hours. Severe: Severe insomnia or severe excessive sleepiness, the sleep deficit is

greater than three hours.

Duration Criteria:

Acute: 7 days or less. Sub acute: More than 7 days but less than 3 months. Chronic: 3

months or longer

2.2. Magnitude of problem (Public Health Importance, Global and national scenario)

2.2.1. Public Health importance

Work patterns of a substantial proportion of the population now extend beyond

regular day-work hours; variable schedules (often including evening or night work) and

rotating shifts are both widespread and expanding.

In a 2005 European survey, 28% of the workforce had variable work patterns, 10%

had evening or night schedules, while 17% worked two-shift or three-shift rotating schedules

.7 Similarly, analyses of U.S. survey data showed that, in 1997, 27.6% of the workforce had

flexible work schedules, while 16.8% of full-time employees had ‗alternative‘ schedules

involving work outside normal day time hours (06.00-18.00 hrs), 6.4% of whom worked

night or rotating shifts.8These proportions varied by occupation; rotating shifts were

particularly common in security services (16.3%), mining (12.5%), and catering (8.7%), but

infrequent among professionals and managers (1.7%). Night work was prevalent in health

care, manufacturing, and manual occupations. Global trends towards a ‗24-hour society‘

6

suggest that these proportions are likely to rise; thus, the implications of shift work for

physical and mental health is not only a matter of current concern but also one that is likely to

become increasingly important in the future .9,10,11

Shift work poses a serious public health

risk, as it can impair an individual‘s ability to perform effectively and may lead to

occupational, traffic or even domestic accidents.

. 2.2.2. Reasons for shift work

Society and employer reasons for shift work are aplenty. A major reason is that

modern technology has made it possible to work day and night. This ―24-hour society‖ of

ours requires that key services be provided at all times. Critical services include public safety,

such as police and fire protection, military defense, health care, transportation and public

utilities, such as electrical power, water and telephone. Certain industries must operate 24

hours per day because the production process is much longer than 8 hour and must be

performed continuously.12

Chemicals and manufacturing industries need to be operated

continuously in order to be profitable.

2.2.3. Prevalence of shift work sleep disorder

Depending on the country, at least between five to eight percent of the population is

exposed to night work. Thus prevalence of SWD may be roughly estimated to be between

two to five percent of the total population.13

An authoritative and well defined study by Drake and colleagues report that the true

prevalence of SWSD is 10.0% among shift workers, and gives an overall prevalence of 1%

.14

The study was done In the general population of Detroit in USA.2036 day-shift, 360

rotating-shift, and 174 night-shift workers participated. This study used Minimum

International Classification of Sleep Disorders.1 In this study, ES was defined by an Epworth

7

Sleepiness Scale(ESS)7 score of the total sample mean + 1 standard deviation (effectively, an

ESS score of ≥13, compared with the more commonly applied ES diagnostic score of ≥10).

Insomnia was diagnosed using Diagnostic and Statistical Manual of Mental Disorders. Drake

and colleagues reported that 32.1% and 26.1% of night-shift and rotating-shift workers,

respectively, met their pre specified ES and/or insomnia criteria, compared with 18.0% of day

workers.

Calculating the ―true‖ prevalence of ES and insomnia—and therefore SWD—in

night-shift and rotating-shift workers was reported to be approximately 14.1% and 8.1%,

respectively. When it is considered that approximately 6% of all workers in the United States

perform night or rotating shift work, the overall prevalence of SWD in the general population

was estimated to be approximately 1%.This study simply deducted the prevalence of SWD

among day workers from those of shift workers. This prevalence may not correct, as this

value seems to be actually the excessive risk or prevalence among shift workers.

Also, this result is lower than the 2% to 5% estimated in the ICSD–2 coding manual

and some sleep specialists have argued that the figure put forward by Drake and colleagues is

conservative.15

However, Drake and colleagues had also applied the more usual ES diagnostic

measure of an ESS score of ≥10 and, using this criterion, found a much higher prevalence of

ES in their study population: 44.8% of night-shift workers and 35.8% of rotating-shift

workers were found to have ES and therefore would also be considered to have SWD,

provided their symptoms persisted for ≥1 month.

A 2007study of 4471 US police officers reported that 2.0% of this population had

SWD, which was defined by the occurrence of both insomnia and ES in associated with a

recurrent schedule of work that overlapped the normal rest period.16

8

During the 1998 Helsinki Heart Study, researchers had also examined the occurrence

of insomnia and/or ES over a 3month period in a population of approximately 3000 middle

aged men participating in a coronary heart disease prevention trial.17

Persistent insomnia was

reported by approximately 50% of rotating- and night-shift workers, whereas persistent ES

was reported by approximately 25% of shift workers overall; those with ES and/or insomnia

therefore met the diagnostic criteria for SWD.

Contrastingly, a study using the Multiple Sleep Latency Test in a population of shift-

working, long-haul bus drivers reported that the criteria for ES were met by 38% to 42% of

subjects.18

Also in contrast, in a study among Italian police officers, insomnia or hypersomnia

were reported by a significantly higher proportion of shift-working personnel compared with

their day-working colleagues (insomnia, 25.9% vs 15.8% , hypersomnia 4.9% vs 2.2%).19

Alternatively, other studies have reported the prevalence of unplanned napping at

work, which may be indicative of ES or sleep deprivation. For example, in a study of almost

700 registered female nurses, approximately 35% and 32% of participants working rotating

or night shifts, respectively, reported episodes of unplanned sleep at work and may therefore

have been at risk for developing shift work disorder.20

In another study of 400 shift workers it

was found that the proportion with a very negative attitude to work hours constituted 8% and

were mainly characterized by marked sleepiness and sleep complaints.21

Summarily, the estimates of the prevalence of shift work sleep disorders have used

different criteria, measures of insomnia or sleepiness and different methodologies. Today,

little overt data exist for the prevalence of SWD. Although the occurrence of insomnia and/or

ES has been studied in various shift-working populations, frequently only one symptom is

analyzed.22

9

Interestingly, Population based polls have found a different prevalence among

respondents. NSF's 2005 Sleep in America poll says that shift workers are more likely to

suffer from insomnia as well as excessive daytime sleepiness. Their poll found a higher

prevalence (61% vs. 47% and 30% vs. 18% respectively).22

If data from United states census is extrapolated, the estimated prevalence of sleep

related disorders in 2004 India would be reportedly 156,628,027 from a population of

10,650,706,072.23

Data available and sleep specialists in United States affirm to these figures

presently.15, 22

Dr. Anuj Chandra, a Chattanooga sleep specialist who has been a leader in

bringing cutting edge sleep medicine to India, is categorical in his opinion that the prevalence

of sleep disorders in India is very similar to what it is in the United States.24

He is also

supportive about the NSF‘s 2005 Sleep in America poll and has advised that these may be the

realistic figures actually seen at the population level.

Studies in India in this arena of sleep disorders are sparse but growing.

The first population based study was undertaken to know prevalence of Obstructive

Sleep Apnea Syndrome (OSAS) at the Vallabhbhai Patel Chest Institute, Delhi, India .A total

of 7975 participants were included. Sleep-related symptoms were seen in 5.1% of subjects.

They estimated prevalence of OSAS is 2.4% in males and 1% in females.25

An article by Dr.Chokroverty provides basic information about some important

laboratory tests and principles of treatment of sleep disorders to the general

physicians.26

Another article in the Indian journal of Medical research , talks about

Circadian rhythm and sleep disorders (CRSD)2 and describes the problem and highlights the

issue as elaborated in the International Classifications of SleepDisorders-2.27

An Editorial in

the Indian journal of Medical research shows how the physicians in India have finally

10

wakened to the reality of sleep disorders. But still research is mainly concentrated on

Obstructive Sleep Apnea syndrome, its research and treatment at large.28

In India, there are no statistics available on the shift working population. Even the

total number of persons in the work force is unknown. According to official figures, from

1981 to 2001 the total number of workers grew more than 50 per cent from approximately

245 million to 402 million persons.29

These figures count only those who are considered to

have ―engaged in economically productive activity for 183 days or more.‖ The actual number

of persons in the work force is likely to be much higher. The Survey results of 2008-09 reveal

that about 94% factories are covered under manufacturing activities giving employment to

about one crore employees, which accounts for nearly 97% of the total number of persons

engaged in the total factory sector.29

2.3. Biomedical theory-Normal Sleep cycle and shift work disorder

Humans and almost all organisms have predictable daily patterns in function and

functionalities. In spite of minor variations in heart rate, blood pressure, and the release of

digestive enzymes, most physiological processes, have a set rhythm. This may be attributed

to the neuroendocrine cycle or the inbuilt human sleep wake cycle.30,31

The word ‗circadian‘ from circa dies (Latin), means ―around a day‖ and refers to the

innate clock within the hypothalamus in the brain. This clock functions on an 24.2 hour cycle

approximately.31

Daylight and social cues tune the circadian rhythm to the 24-hour day.The

current understanding of the circadian system in mammals may be used to describe the

features of the 6 recognized circadian rhythm sleep disorders (CRSDs).

11

2.3.1. The Circadian system-The circadian system consists of 3 parts:

(1) Input pathways (2) Central oscillator and (3) Output pathways.

In Humans, the circadian clock governs sleep in a linear pathway. Retina captures

light and is via melanopsin in ganglion cells of the retinohypothalamic tract transfers it to the

suprachiasmatic nuclei (SCN) in the hypothalamus. The hypothalamus is the vortex of

circadian cycle. The hypothalamus reads it as length of day and transfers signals further to the

pineal gland. The pineal gland is located near the centre of the brain, between the

two hemispheres. It secretes melatonin during night for a duration corresponding to the

usual dark period of the day (scotoperiod) .

FIGURE 1.-Entertainment of sleep wake cycle by light.

Source:Christopher L. Drake,The characterization and pathology of circadian rhythm sleep

disorders.35

The SCN activates other output pathways, like the adrenal gland. This releases the

stress hormone cortisol in the morning prior to waking.The SCN is also found to rhythmically

transcribe clock genes controlled by auto regulatory feedback. It ensures autonomous

working and also responsiveness to external light and dark cycle. Clock genes that have been

12

described in humans are hPer (period homolog)1, hPer2, hPer3, hCLOCK (circadian

locomotor output cycles kaput), hCK(casein kinase)1δ, and hCK1ε. 32

Interestingly, the sleep-

wake cycle is not solely ruled by the circadian system. Sleep pressure or a homeostatic sleep

drive is inevitable after successive waking hours. Usually two systems act together

synergistically, with the homeostatic system encouraging sleep, while the circadian signal

opposes this process by promoting wakefulness

Normally, the circadian wakefulness increases as the day progresses and then dips

with the melatonin secretion at the start of evening. This triggers sleep onset. In normal case,

circadian and homeostatic factors work synergistically to promote sleep and wakefulness

alternately. 33

However, when the body‘s internal circadian phase is disturbed, the homeostatic

and circadian systems are unable to maintain appropriate sleep and wake cycle. In Shift work,

workers may struggle to stay awake at night in the face of increased homeostatic pressure for

sleep, without the benefit of a wake-promoting signal from the SCN

FIGURE 2A The Normal sleep cycle


disorders

13

During shift Work, circadian drive for wakefulness, works against forced sleep at day

time. During night-time work hours, homeostatic drive for sleep acts against the circadian

need and demand for wakefulness

FIGURE 2B-Sleep cycle in a shift worker


disorder.

2.3.2. Types of circadian rhythm sleep disorder

The 6 main CRSDs can be broadly classified into 2 types: Intrinsic and Extrinsic.

Intrinsic CRSDs are characterized by asynchrony between the patient‘s sleep-wake cycle and

the external day-night cycle, due to dis-regulation within the internal circadian system. These

are Delayed sleep-phase disorder, advanced sleep-phase disorder, free-running disorder (non–

24-hour sleep/wake syndrome, and irregular sleep/wake rhythmExtrinsic CRSDs result from

an imposed or forced change in the behavioral timing of sleep and wakefulness compared to

internal circadian timing. Shift-work disorder and jet lag disorder are extrinsic CRSDs

14

2.3.3. Shift-work sleep disorder

Shift work sleep disorder occurs when work or occupation demands that the worker

function at times that are in opposition to his or her body‘s normal circadian-controlled

periods of sleep and wake.

Generally, workers with SWD experience insomnia when trying to sleep and/or have

conversely excessive sleepiness when trying to remain awake. Sleep in patients with SWD is

broken, with marked difficulty in maintaining sleep during day hours. Sleep lost due to shift

work over successive nights eventually snowballs into a sleep debt that intensifies the

homeostatic sleep drive.34

Over time, the circadian drive competes with this overwhelming

sleep debt, further exacerbating excessive sleepiness. This leads to impaired work

performance, and increases the risk of accidents in individuals with SWD.4

The high degree of variation between individuals in terms of the severity of symptoms

associated with shift work seems complicated. Research in melatonin rhythms indicate that

adapting circadian rhythms to their varying patterns of sleep and wake is not always possible.

Some workers may be physiologically unable adjust their circadian rhythms.35

Again;

adaptation may be possible in night-shift workers who are forced to go back to a night-time

sleep schedule on their days off. They thus do not have a regular circadian sleep/wake

adjustment with the light/dark cycle. Night-shift workers mal-adapting to their new shift

schedule report reduced sleep during the daytime, thus increasing the risk of developing

Shift work sleep disorder .36

Summarily, in patients with SWD in spite of trying to adapt and

adjust to the varying work schedule, unfortunately insomnia and/or excessive sleepiness seem

to persist.

15

2.4.Diagnositic and therapeutic features.

2.4.1. Diagnosis: Diagnosis is indicated by the presence of typical history combined

with work or occupational history of being engaged in shift work.

ICDS gives the Diagnostic Criteria for Shift Work Sleep Disorder. (307.45-1) .1

A. The patient has a primary complaint of insomnia or excessive sleepiness.

B. The primary complaint is temporally associated with a work period (usualy night work)

that occurs during the habitual sleep phase.

C. Polysomnography and the MSLT demonstrate loss of a normal sleep-wake pattern (i.e.,

disturbed chronobiologic rhythmicity).

D. No medical or mental disorder accounts for the symptoms.

E. The symptoms do not meet criteria for any other sleep disorder producing

insomnia or excessive sleepiness (e.g., time-zone change [jet lag] syndrome).

Minimal Criteria: A plus B.

Severity Criteria:Mild: Mild insomnia or mild excessive sleepiness, the Sleep deficit is

often one to two hours.Moderate: Moderate insomnia or moderate excessive sleepiness; the

sleep deficit is often two to three hours.Severe: Severe insomnia or severe excessive

sleepinessThe sleep deficit is greater than three hours.

Duration Criteria:Acute: 7 days or less.Subacute: More than 7 days but less than 3

months.Chronic: 3 months or longer

Polysomnographic Features: Polysomnographic recordings may be useful if the sleep

disorder is severe or the etiology of the sleep disturbance is in question. A 24-hour recording

over the first and last of the series of rotating shift is to be performed. Monitoring of an

16

episode of usual daytime wakefulness and night sleep during a daytime shift is ideal for

comparative purposes. If excessive sleepiness is part of the complaint, a multiple sleep

latency test should be carried out in the standard manner at least three times: at the beginning,

middle, and end of the work shift.

Polysomnography demonstrates impaired quality of sleep, with either a prolonged

sleep latency or shortened total sleep time. The sleep period may be fragmented, with

frequent arousals and awakenings. The MSLT may demonstrate excessive sleepiness during

the time of the work shift.

Other Laboratory Test Features: Actigraphy may be helpful to demonstrate a

disrupted sleep-wake pattern consistent with shift work sleep disorder. There may be a loss of

the normal pattern of circadian rhythmicity, as demonstrated by 24-hour temperature or

biochemical patterns.

2.4.2.Differential Diagnosis:

Disorders of initiating sleep disorders of sleep maintenance, depending on morning or night

shift. The excessive sleepiness should be differentiated from that due to narcolepsy or sleep

apnea syndrome. Sometimes, patients with sleep disorders such as narcolepsy tend to adopt

shift work as an attempt to rationalize symptoms of excessive sleepiness.

2.4.3 Treatment

Most essential thing is to identify and address any co morbid conditions that might

contribute to poor sleep hygiene and/or cause ES or fatigue during required periods of

wakefulness. Important co morbidities are other sleep disorders, such as obstructive sleep

apnea (OSA), and mood disorders, such as depression.

17

An algorithm for the management of SWD in the primary care setting, including steps

to evaluate co morbid disorders is given by Dr. Michael J. Thorpy.37

Non pharmacologic

interventions, available for the treatment of SWD are improvement of sleep hygiene,

exercise, and timed exposure to light.38,39,40

Pharmacologic interventions

The wakefulness-promoting agents modafinil and armodafinil are the only

interventions with FDA approval for use in patients with SWD and have been evaluated

specifically among individuals with ES associated with SWD.41,42,43

A number of studies among individuals undergoing simulated night-shift work

suggest that caffeine or stimulants such as methamphetamine may be useful to promote

wakefulness during the work period, although there may be some residual effects on daytime

sleep depending on the caffeine drink selected.44,45,46,47

Administration of the sleep-mediating

hormone melatonin is also reportedly effective in promoting daytime sleep.48

2.5 Impact of shift work sleep disorder

2.5.1 How shift work affect health

Mainly three pathways have been used to elucidate the relationship between shift

work and other concomitant problems.49,50,51

1) Disruption of circadian rhythms (this leads to sleep/wake disturbances producing

desyncronisation of biological clock finally leading to an increased susceptibility to disease)

2) Disturbed social and temporal systems from odd work hours leading to family problems

and stress

18

3) Behavioral changes in such as irregular or poor diet and, smoking. Also cholesterol, blood

pressure and cardiac activity show changes, and may act as mediators of morbidities.49

Shift workers have usually been noticed to have erratic lifestyles owing to their

behavioral and biological risk factor or both .52,53

Shift work has been reported to have

adverse effects on health even in the absence of SWD, there is growing evidence that shift

work may affects lifespan.14,15

Figure No.3.Disease mechanisms in shift work

Source:Knutsson A. Shift work and coronary heart disease

2.5.2. Gastrointestinal disorders

Gastrointestinal complaints are a regular among shift workers. These are about 2 to 5

times more common among night shift workers as compared with those not working nights

.54

Circadian disturbance is reported to affect the digestion, and absorption of food. After

19

adjusting for demographic variables, job, and lifestyle variables, shift workers have reported

higher prevalence of indigestion, heartburn, constipation, loss of appetite, and nausea than

day workers.55,56

. Evidence also links shift work to peptic or duodenal ulcer.57

In an Japanese study which used endoscopic examination, the prevalence of gastric

ulcer was 2.38% among shift workers, and 1.03% in day workers.58

Duodenal ulcers also

showed higher prevalence among shift workers in the same study. In an Italian study shift

work was also found to be associated with significant metabolic disturbance. The study

correlated shift work with with 3 of the 5 diagnostic symptoms of metabolic syndrome.59

In

an Japanese study, diabetes prevalence has been seen to increase with duration of exposure

to shift work. Here markers of insulin resistance was more common seen among in shift

workers .60

2.5.3. Cardiovascular disease

Shift work seems to be a significant risk factor associated with cardiovascular disease.

A meta-analysis of 17 studies of cardiovascular disease and shift work elaborates on this

assocations.61

Overall , shift workers were found to have a 40% excess risk for cardiovascular

disease when compared to day workers. Reportedly, night work limits the normal night time

reductions in blood pressure and also reduces heart rate variability.62

Such workers without

normal fluctuations are likely to develop hypertension, snowballs into adverse cardiovascular

outcomes.63

Also there is has been published evidence that ES may be a risk factor for

increased blood pressure.64

Tenkanen et al analyzing the Helsinki study in 1997 on a 6-year

prospective study of cardiovascular (CHD) risk, followed up 1806 industrial workers. He

found that overall, the relative risk of CHD among shift workers as compared to day workers

was 1.5 (CI 1.1- 2.1) .65

Shiftwork was also found to interact with smoking and obesity to

20

increase CHD risk. A review by Knutsson in 2003 reported evidence of an association

between shift work and coronary heart disease.50

2.5.4 Mental Health

Depression has been reported and linked to shift workers, especially among women.

Drake and colleagues‘s study had also reported that symptoms of SWD were associated with

elevated rates of depression (OR, 2.57 (CI 2.01-3.27)).14

He cautions us that although SWD

seems associated with depression, shift work does not increase the risk of developing mood

disorders .A study of radar controllers in the US Air Force using the Zung Anxiety and

Depression Scales reveal that shift workers with SWD were more likely to experience anxiety

and also more prone to depression.66

2.5.5. Accidents

Shift workers are more likely to have work-related accidents than are day workers.67

Chances of a medical resident or a nurse to have a injury ,or report an error was found to be

two times during a night shift or rotating than during a day shift.68

Police officers working shifts were seen to be more likely to experience a sleep

related accident at work or at home than were their regular work counterparts.(OR 2.24,p

<.0005).14

Accidents reported by workers going home after the night shift are more than those

reported by day workers.69,70

Excessive sleepiness in morning hours is also hypothesized to

be responsible for the increased rate of military flight accidents.71

2.5.6. Social and Domestic life

Working in shift seems to affect the quality of life. In the same study of American radar

controllers, it was seen that shift workers in general experienced more anxiety and irritability,

21

and that sleep disorder seems to lower the quality of life.51

Drake and colleagues‘s study also

had similar findings. They found more individuals with sleep disorder seem to miss social

and family interactions due to sleep problems than those without SWD.14

2.5.7. Cognition and Executive functions.

Independently, sleep deprivation and excessive sleepiness seems to impair memory, learning,

alertness, and work performance, even in the absence of overt circadian problmes.72,73

Also a study that assessed mathematical learning, reports that circadian disturbances

could be detrimental to learning, even among normal people who temporarily failed to adapt

their circadian cycles.74

Shift workers who suffer from a snowball effect of sleep deprivation

and excessive sleepiness have also been reported to have reduced attention, alertness and

consequently performance .Again alertness and cognitive processes may be impaired during

the transition from of shifts.75,76,77

2.6. Prognosis

Earlier it was thought that shift working would be better tolerated as time elapsed.

Shift workers might have fewer domestic pressures from children, and perhaps more coping

ability. The fact that older people seem to require less sleep than younger people, was also

supposed to help. Today the research findings seem to teach us otherwise.

Recent evidence seems to tell us that aging worker may not tolerate shift work as

deftly as young workmen .With age, sleep becomes shorter and fragmented. This can again

complicate the situation.78

But if recognized, diagnosed and treated, workers may be able to

adapt and resynchronize themselves in their bio rhythms, life and person. At its extreme, shift

work disorder may lead to Cancer. The International Agency for Research on Cancer (IARC)

22

has concluded that "shift work that involves circadian disruption" is considered a Group 2A

carcinogen and "probably carcinogenic to humans.‖79

2.7. Current Recommendations.

Today there are recommendations available at various levels to prevent and diagnose

this growing problem. National Institute of Occupational Safety and Health (NIOSH), USA,

has recommended measures to be taken at Organization level and also for the Individual

worker. 80,81

At the individual level some of them are -a healthy diet and exercise

program..82

Avoiding caffeine and alcohol close to bedtime.Developing a relaxing sleep ritual

and following good sleep hygiene.Keeping a regular sleep schedule—going to sleep and

waking up at the same time every day, including weekends.

The National Institute for Occupational Safety and Health (NIOSH) recommends that

organizations design health work schedules, allotting free time for needy workers, efficient

work load distribution and health work environments along with counseling programs.

2.8. Rationale of the study

There been little work to examine prevalence and consequences of shift work sleep

disorder in comparison to the difficulties with insomnia and excessive sleepiness experienced

by day workers. I have chosen to base my study among industrial worker as they are the most

affected due to shift work (They lack the cushioning of comfort provided by similar shift

working professionals)

23

2.9. Research Question

What are the detrimental effects of working in a varying pattern of work on the

quality of sleep and consequently work alertness, general health and social roles?

2.10. Objectives

1. To ascertain the prevalence of shift work sleep disorders and their associations with

performance and safety in terms of self reported injuries/accidents

2. To assess the impact of shift work on physical health with emphasis to

gastrointestinal system and cardiovascular system.

3. To find out the Impact of shift work on personal and family life as perceived by the

worker

24

CHAPTER 3. METHODOLOGY

3.1 Study Design: Cross sectional design

3.2 Cross sectional survey:

3.2.1 Study setting: The study was conducted among workers of Kerala Minerals and

Metals Ltd , Chavara, Kollam and Travancore Titanium Ltd ,two Public sector enterprises in

Kerala. Both have continuously running chemical plants, producing Titanium dioxide and

employ both shift and regular workers. Both have same shift timings and almost similar

salary packages. The work processes and factory setting are mostly similar, if not same.

3.2.2 Sampling Unit-Sampling unit was the ―Shift worker‖ as compared to

―Regular/Day worker‖

3.2.3 Sample size:

The difference in excessive daytime sleepiness (a key component of shift work sleep

disorder) obtained as per literature review to be 30 percent among shift workers and 18

percent among regular workers. This difference was used to fix the sample size. Sample size

was fixed to be 215 for each group of workers. This sample size was calculated using epi-info

version 3.5.2 statcalc to get a study result with 80% power and a maximum alpha error of

5%.Accounting for a non response rate or drop out of 30% the sample size was then rounded

to 280.Therefore final sample size was 560(280 regular workers and 280 shift workers)

During the course of the study, 560 workers were recruited, but due to drop outs, final

sample size obtained was 482. The study had 255 shift workers (intended 280) and 227

regular workers (intended 280).Coverage was therefore 86.07 percent.

3.2.4 Sample selection:

25

Random sampling method was followed by using employee roll, and spss random

selection procedure. It was duly seen that that the workers ―adjusted‖ and often interchanged

their shifts and work stations amongst themselves. Therefore in about 60 workers, the worker

who was working at the work station was taken in place of the worker chosen by the random

selection procedure.

For the clinical tests, again random sampling was done to obtain 30 random shift

workers and 30 random regular workers. They were obtained from among the workers

previously selected and from those who had given consent to undergo clinical testing. If any

of the workers were unavailable or expressed inability to undergo testing, the next worker in

the serial order was taken.

3.2.5 Inclusion and exclusion criteria-Workers who are on company rolls and have

been working in their respective shifts-regular or rotating, for 6 months were included in the

study. Exclusion criteria-workers who have been diagnosed with any kind of sleeping

disorder or are on therapeutic treatment for any sleeping disorder were excluded.

3.2.6 Data collection: Written Informed Consent was taken after assuring

confidentiality and non effect on Employee review, records, benefits and medical records.

Data was collected in 3 stages

(1) Recruitment of workers after explaining the study and obtaining informed

consent. The sleep log was assigned to be completed.

(2)A pretested questionnaire was used comprising of 2 instruments-A Work

log-to record shift work or normal working schedules, and a comprehensive

Questionnaire comprising of shift work sleep index, Insomnia questionnaire and

26

Epworth sleep questionnaire was then given to the worker to be returned after 2 weeks

along with the sleep log.

(3)Rey Auditory verbal learning tests (immediate and quick recall),Trail A,

Trail B and Digit span tests-forward and backward were done to check for fronto-

temporal functions, at a later date upon a selected subset of the sample.

All clinical tests were taught to the investigator, by a practising neuropsychologist,

under guidance of the consultant neurologist and sleep specialist. They were practiced upon

normal people and then upon screened patients attending a neurology clinic, after due

consent.

The Rey Auditory verbal learning tests (RAVLT) are useful in evaluating verbal

learning and memory. There are comprehensible ‗lay‘15 words, which read out read aloud at

the rate of one per second. The subjects were asked to repeat all the words he can remember,

in any order. This procedure is carried out a total of five times. Then second list of 15 words,

was presented a allowing the subject only one attempt at recall. Immediately following this,

the subject was asked to remember as many words as possible from the first list.83,84

The Trail Making Test is a measure of attention, speed and mental flexibility. Both

parts of the Trail Making Test consist of 25 circles distributed over a sheet of paper. In Part

A, the circles are numbered 1 – 25, and the subject was asked draw lines to connect the

numbers in ascending order. In Part B, the circles include both numbers (1 – 13) and letters

(A – L).The subjects were asked to draw lines to connect the circles in an ascending pattern,

but with the added task of alternating between the numbers and letters (e.g. 1-A-2-B-3-C).

The subjects were timed as they connected the "trail."85

27

Digit span is a common measure of short-term memory, the number of digits a person

can absorb and recall in correct serial order after hearing them .The has to remember a small

amount of information for a relatively short time, and the order of recall is important. To test

the auditory digit span of respondents, numbers were said slowly in one second intervals and

subjects were asked to repeat it back.86

3.2.7 Data storage: All data obtained were kept safely with the principal investigator,

who bears the sole responsibility for safe keeping and any breach of confidentiality. Data

shall be maintained by principal investigator for any future reference.

3.2.8 Data Entry, Analysis and Statistical Measures: All these data were entered in

Epidata version 3.1 and analyzed in SPSS version 17.Descriptive analysis was done to look at

the sample characteristics. Bivariate analysis was done to find the relation between the

predictor and outcome variables. Further multivariate analysis was done using binary logistic

regression and came up with the final models.

3.2.9 .Variables used in the study

3. 2.9.1.Dependent variables

Insomnia -Based on insomnia questions -described in Appendix B 2 and contained in

questions 3.16,3.21,3.23 and 3.15 of the questionnaire. Insomnia was taken to be present if

respondent had difficulty in going to sleep, sustaining sleep or had early awakening, any of

the above three accompanied with un refreshed sleep.

Excessive Sleepiness-Excessive Sleepiness was taken to be present if the Epworth Sleepiness

Scale described in Appendix B 3 and contained in question 3.28 of the questionnaire, gave a

total score of more than or equal to 10.

28

Insomnia or Excessive Sleepiness- This is based on the above two dependent variables,

Insomnia as well as Excessive sleepiness. For the prevalence of shift work sleep disorder, this

is also the working definition among workers who are in the shift work schedule.

Satisfaction with job-This is taken as general job satisfaction more or general job satisfaction

less, based on the median score calculated based on total score. Respondents scoring more

than 29 were taken as more satisfied, while respondents scoring 29 or lesser were taken as

less satisfied with job.

Gastro intestinal problems-This is based on the Physical health questionnaire-described in

Appendix B 4 and contained in section 4 question 4.1 (a) to 4.1 (h) in the questionnaire.

Median score was calculated. Respondents with score of 15 or more were taken to have

Symptoms suggestive of gastro intestinal diseases.

Cardiovascular problems-This is based on the Physical health questionnaire-described in and

Appendix B 4 contained in section 4 question 4.1 (i) to 4.1 (p) in the questionnaire. Median

score was calculated and respondents with score of 12 or more were taken to have Symptoms

suggestive of cardiovascular diseases.

Mental Health score-This is based on the GENERAL HEALTH QUESTIONNAIRE-

described in Appendix B 5and contained in question 4.7 of the questionnaire. Median score

was calculated and respondents with score of 10 or more were taken to have Poor Mental

health

Overall Socio and domestic Score-This is based on the SOCIAL AND DOMESTIC

SURVEY- described in Appendix B 6and contained in question 5.1 to 5.5 of the

questionnaire. Median score was calculated and respondents with score of 55 more were

29

taken to be more satisfied with time available after or around work in relation to their social

and domestic life.

3.2.9.2. Independent variables

Socio demographic variables-Age, Height, Weight, and Years in service, marital status and

Number of children were asked.

Work related variables-Work schedule was captured by work log. Among Shift workers,

reasons for working shifts, its perceived advantages and disadvantages were asked. They

were asked whether, they feel advantages outweigh disadvantages. They were also asked if

all things remaining equal, whether they would change over to regular shift.

Sleep related variables-Sleep quantity and quality were assessed by different questions.

Quantity of sleep was verified in a subsample using the sleep log.

Accidents and injuries variables-Accidents and injuries were asked for by asking for even

been witness to accident or injuries, or having had an accident or injury or having one on the

way back home after work. The shift /or timing of each of these was also asked.

Variables to capture Habits-Cigarettes smoked, units of alcohol, and cups of tea or coffee

taken in were asked. Also before and after shift information, regarding the same was asked.

3.3. Ethical considerations

3.3.1. Risks to the participants

There were no risks involved in participating in the study in the wake of all

precautions taken, to protect the identity of workers and anonymity maintained.

30

3.3.2. Privacy and confidentiality

Identity of the participants is known only to the principal investigator. A

dummy code was used and all personal details were erased after data collection. This

coding contained in the dummy code register, is maintained by the principle

investigator. Only the faculty guide, other than principle investigator has had access

to raw data that has already been coded anonymously. Whatever has been and will be

shared, for academic purposes is the summarized data of the whole sample. Access to

the personal identification data through the dummy code not only anonymised the

worker and also enabled to direct the worker to a sleep specialist in the case the

worker had a sleep disorder.

3.3.3. Benefits

This study offered the participant the chance to be diagnosed, if he suffers from

insomnia, excessive sleepiness or both. All workers diagnosed thus shall be referred to the

Comprehensive sleep clinic at Sri Chitra Institute for Medical Sciences and Technology .If

recognized, diagnosed and treated, workers may be able to adapt and resynchronize

themselves in their bio rhythms, life and person. They may be able to tide over the effects of

sleep defects and cure themselves of the sleep disorder. Also the study results may bring forth

policy changes which may prove beneficial to the community at large.

3.3.4. Informed consent process

Informed consent was taken by the principal investigator right before administering

the interview schedule at stage of recruitment. Clearance was obtained from the institutional

ethics committee before commencement of the study.

31

3.3.5. Funding source

Funding was applied for and part of funds required was obtained from Kerala

state Council for Science, Technology and Environment. All research work done and

presented herewith are independent of any influence whatsoever, and there are no

conflict of interests.

32

CHAPTER 4. RESULTS

This chapter describes the outcomes of data analysis in concurrence with the stated

objectives. After scrutiny, data entered was analyzed using SPSS for windows version

17.Baseline characteristics of the sample population were first understood. Using the

conceptual framework and based on literature review, data was analyzed for associations

between various independent variables and outcome variables.

4.1 General description of Survey outcome

Out of the 580 workers recruited for the study, only 482 returned their questionnaire,

despite best efforts. Not all workers responded to all questions in various sections of the

questionnaire. Therefore the number of respondents is also given wherever all the 482

respondents did not answer a question or section. Total workers in each category total are 227

in the Regular shift group and 255 in the Shift working group. Therefore final coverage is

86.07% of targeted size.For the Clinical tests, the tests were done by the principal

investigator who, at the time did not know about their responses or results of their

questionnaire replies.30 random regular workers and 30 shift workers who had been part of

the earlier survey were taken as a sub sample and tested.

4.2 Univariate analysis

4.2.1. Demographic description of the study subjects.

The mean age of regular workers was 45.14 (SD 9.029),while that of the shift

workers was 42.45(SD 9.330).Most regular workers were in the above 50 age group ,when

age was segregated into five year age groups. Five year age group was taken so as to

facilitate calculation of prevalence as compared to the WHO standard population. The shift

33

working group mainly composed of younger workers as indicated by 46 percent of them

falling in the 30-34 and 35-39 age group.The Mean Body Mass Index of regular workers was

25.24 (SD 2.96),while that of shift worker was 26.49 (SD 2.69).When categorized into

Undernourished, Normal BMI, Overweight and Obese, majority of the workers in both

category were overweight. More shift workers (67.2%)were overweight than regular

workers(50.4%).The mean number of years, served in the industry was comparable among

both categories of workers. On an average regular worker group had 17.33 yrs in service

while the shift workers had put in 15.87 yrs of service. Majority of the workers in both

groups had put in more than 14 yrs of service

Demographic

and Physical

characteristics

Regular worker, n=227

Mean(Confidence

interval)

Shift worker. n=255

Mean(Confidence

interval)

p value

Age 45.14(43.96-46.31) 42.45(41.30-43.59) 0.001

Body Mass

Index

25.24(24.85-25.62) 26.49(25.96-27.01) <0.001

Body Mass

Index

(n=479)

Underweight

Normal BMI

Overweight

Obese

(Grouped) n=226 (%)

2(.9)

102(45.2)

114(50.4)

8(3.5)

n=254(%)

1(.4)

62(24.5)

170(67.2)

20(7.9)

Total-479(%)

3(.6)

164(34.3)

284(59.3)

28(5.8)

<.001

Years in service Mean(Confidence

interval)

17.33(16.23-18.42)

Mean(Confidence

interval)

15.87(14.82-16.91)

0.59

Years in service

upto14yrs

>14 yrs

(Grouped) n (%)

95(41.9)

132(58.1)

n (%)

125(49)

130(51)

Total(%)

219(45.5)

262(54.5)

0.126

Table 1.Mean Age, Body Mass index and Years in service between regular and shift workers

34

Age groups Work schedule Total(%)

Regular workers (%) Shift workers (%)

20-24 yrs 1(0.4) 2(0.8) 3(0.6)

25-29yrs 16(7.0) 8(3.1) 24(5.0)

30-34yrs 17(7.5) 59(23.1) 76(15.8)

35-39yrs 35(15.4) 59(23.1) 94(19.5)

40-44yrs 29(12.9) 24(9.5) 53(11.0)

45-49yrs 41(18.1) 16(6.3) 57(11.8)

50-54yrs 53(23.3) 51(20.0) 104(21.6)

55-59yrs 35(15.4) 36(14.1) 71(14.7)

Total 227(100.0) 255(100.0) 482(100.0)

Almost 90 % of the men were married in both regular and shift working group.7.1 %

of the regular workers were unmarried as compared to 4.1 % of shift workers.

Regarding the habits of workers, 134 workers had responded to the question about

smoking. Smoking was uniformly seen in both work groups.30 percent of regular workers as

well as shift workers were smokers.155 workers had responded to the question regarding

alcohol consumption. 33 % of regular workers were alcohol users while 38.9% of shift

workers used alcohol. Due to the stigma regarding use of alcohol and smoking, probably

fewer people responded to these questions. 466 workers responded to question about tea or

coffee drinking. Both groups had high consumption of coffee and tea, typical of the culture

and work environment.

Table 2. Age of Regular and Shift workers segregated into five year age groups

35

Variable

Regular worker

225 (%)

Shift worker

255 (%)

Overall n(%) p value

Marital status

(n=480)

Married

Divorced

Widower

Unmarried

203(90.2)

5(2.2)

1(0.5)

16(7.1)

238(93.3)

3(1.2)

1(1.2)

11(4.3)

441(91.9)

8(1.7)

4(0.8)

27(5.6)

.342

Habits

Smokers(n=450)

Alcohol users

(n=441)

Tea/coffee users

(n=466)

64(30)

69(33)

202(93.1)

72(30.4)

90(38.9)

244(98.0)

136(30.2)

159(36.1)

446(95.7)

.939

.207

.009

4.3 Bi variate analysis-Three sets of analysis were attempted.

The first set of analysis intended to arrive at the problems of shift work. For this,

proportion of regular and shift workers were cross-tabulated against various co morbidities.

The second set of analysis aimed to arrive at the associations of sleep disorder, namely

Insomnia, Excessive Sleepiness and Insomnia or excessive sleepiness. For shift workers, this

corresponds to shift work sleep disorder‘s working definition. The third set of analysis aimed

to correlate the clinical findings between types of workers.

4.3.1 Type of shift cross tabulated against various morbidities and co morbidities.

4.3.1.1. Sleep disorders

Sleep variables collected from sleep section were used for bivariate analysis.

Insomnia, excessive sleepiness was calculated using questions and the Epworth sleepiness

Table 3-Marital status and Habits of Regular and Shift workers

36

scores as described before. The presence of either insomnia or excessive sleepiness was also

looked for, in order to calculate the prevalence of shift work sleep disorder, among shift

workers, according to the working definition of shift work sleep disorder.20(8.8%) regular

workers reported insomnia and 27(12%) had excessive sleepiness. In shift workers, 54

workers (21.2%) reported insomnia, while 71(28.1%) reported excessive sleepiness. Among

regular workers 41 (18.1) workers had either Insomnia or Excessive sleepiness. Among shift

workers, 103 workers (40.4) had either Insomnia or Excessive sleepiness. These results were

significantly different between both the groups of workers.

Thus as per definition, the prevalence of Shift work sleep disorder -insomnia or

excessive sleepiness among this population is 40.4%.

The risk difference may be calculated as follows. The prevalence of sleep disorders

being 18.1% in regular workers, the risk difference is 22.3% with a 95% CI of 14.47 to

30.13%. This estimate is suggestive of the actual location of the prevalence of shift work

sleep disorder after ruling out sleep disorders due to other causes. If the regular and shift

workers be considered as retrospective cohorts with the exposure being shift work and the

outcome to be sleep disorder, we may be able to assess relative risks ,since they are mutually

exclusive groups. The Relative Risk (RR) among shift workers as compared to regular

workers is 2.24 (95% CI 1.63-3.06)

When adjusted to age , according to the new World Health Organisation-2000-2005

standard population, the prevalence of shift work sleep disorder(insomnia or excessive

sleepiness among this sample is 30.74%. Similarly the prevalence of insomnia or excessive

sleepiness among regular workers is 26.14%.

37

Sleep Disorder Regular

worker n(%)

Shift

worker n(%)

Overall

n(%)

Odds ratio

(95% CI)

p value

Insomnia 20(8.8) 54(21.2) 74(15.4) 2.78(1.61-4.81) <0.001

Excessive

Sleepiness

27(12) 71(28.1) 98(20.5) 2.86(1.75-4.65) <0.001

Insomnia or

Excessive

Sleepiness

41(18.1) 103(40.4) 144(29.9) 3.07(2.02-4.68) <0.001

4.3.1.2. Symptoms suggestive of gastrointestinal, cardiovascular disease, and

mental health status of workers.

Based on the Physical health questionnaire, 16 symptoms along with their

severity or frequency were put forward to the worker, to capture any undetected morbidities

regarding the gastrointestinal system or cardiovascular disease. 84 regular workers (42.6%)

had symptoms suggestive of gastrointestinal disorder. More shift workers, 115 in number

(53.1%) had similar symptoms. Regarding Symptoms suggestive of cardiovascular diseases,

71 regular workers (36.2%) reported to having them, as compared to the higher number128

among shift workers (56.6%). This result is significantly different among both the groups and

is in alliance with the accepted current review of literature.

The General Health Questionnaire was used to arrive at the mental health status of the

workers. The mental health of both group of workers were comparable. Better mental health

was taken as the variable, compared to poor mental health based on median scores, and duly

cross tabbed with work schedule 98 regular workers (49.7%) were found to have better

mental health . Among shift workers, 120 workers (51.5%) were seen to have better mental

health based on their mental health score

Table 4- Insomnia, Excessive Sleepiness and Insomnia or Excessive Sleepiness

of Regular and shift worker

38

Table 5-Symptoms of Health problems among Regular and shift worker

Symptoms of

Health Conditions

Regular

worker n(%)

Shift worker

n(%)

Overall

n(%)

Odds ratio

(95% CI)

p

value

Symptoms

suggestive of

Gastrointestinal

diseases

84(42.6) 115(53.1) 119(48.1) 1.52(1.03-2.24) .035

Symptoms

suggestive of

Cardiovascular

diseases

71(36.2) 128(56.6) 199(47.2) 2.30(1.55-3.40) <0.001

Better Mental

Status

98(49.7) 120(51.5) 218(50.7) 1.07(.73-1.56) .717

4.3.1.3. Occupational issues among workers

History of other diseases commonly seen as occupational, was asked for among the

workers. These were either diagnosed diseases or self reported as having had them. Chronic

Back pain, Stomach or duodenal ulcers, Sinusitis/Tonsillitis, Bronchial Asthma, Angina,

Heart Attack, Hypertension, Arrythmia, Hypercholesterolemia ,Diabetes, Urinary infection,

Skin diseases, Chronic anxiety Depression, Arthritis, Hemorrhoids and Varicose veins were

the diseases asked among the workers.

Among these, Stomach or duodenal ulcers, Sinusitis/tonsillitis Angina, Hypertension,

Hypercholesterolemia, and diabetes prevalence was found to be significantly different among

the two groups of workers.31 regular workers(13.8%) had Stomach or duodenal ulcers,

compared to 57 shift workers(22.4%).Sinusitis/Pharyngitis prevalence was lower among the

regular workers. Only 28 of regular workers (12.6%) reported it, while 57 shift workers

(22.6%) had the same. Angina was also found to have a lower prevalence among regular

workers, with 15 percent cases (6.7%) as compared to th33 shift workers who reported to

39

have angina (13%).63 regular workers were reportedly hypertensive (28.3%),while 103 shift

workers were hypertensive(40.4%). 49 regular workers had high cholesterol(21.9%),while 81

of the shift workers had high cholesterol(31.8%). 55 regular workers (24.6%)were reportedly

diabetic while 87 of the shift workers were diabetic(34.3%).

Table 6-Self reported health problems among Regular and shift worker

Disease

(self reported)

Regular worker

n (%)

Shift worker

n (%)

Overall

n (%)

Odds ratio

(95% CI)

p value

Chronic Backache 30(13.7) 47(18.4) 77(16.1) 1.45(.88-2.39) .140

Stomach ulcers 31(13.8) 57(22.4) 88(18.4) 1.79(1.55-3.40) .016

Sinusitis/Pharyngitis 28(12.6) 57(22.6) 85(17.9) 2.04(1.24-3.34) .004

Asthma 35(15.7) 39(15.3) 74(15.5) .97(.54-1.59) .904

Angina 15(6.7) 33(13) 48(10) 2.08(1.09-3.94) .022

Heart attacks 6(2.7) 12(4.7) 18(3.8) 1.79(.662-4.86) .245

Hypertension 63(28.3) 103(40.4) 166(34.7) 1.72(1.17-2.52) .005

Arrythmias 23(11.3) 40(15.7) 65(13.7) 1.47(.86-2.517) .155

Hypercholesterolemia 49(21.9) 81(31.8) 130(27.1) 1.66(1.10-2.51) .015

Diabetes 55(24.6) 87(34.3) 142(29.7) 1.60(1.07-2.38) .021

Urinary Tract

Infections

17(7.6) 16(6.3) 33(6.9) .815(.40-1.65) .571

Skin diseases 22(9.8) 40(15.7) 62(12.9) 1.70(.98-2.97) .056

Chronic anxiety 21(9.4) 25(9.8) 46(9.6) 1.05(.57-1.94) .863

Depression 30(13.5) 50(19.7) 80(16.8) 1.57(.96-2.58) .069

Arthritis 23(10.3) 24(9.4) 47(9.8) .91(.49-1.65) .753

Hemorrhoids 18(8.1) 29(11.4) 47(9.8) 1.46(.79-2.71) .227

Varicose veins 18(6.8) 25(9.9) 40(8.4) 1.51(.77-2.94) .221

40

Accidents and Injuries among workers were taken and cross tabulated according to

their work schedule.19.6% of regular workers had witnessed accident to someone around

them in the last 2 months, compared to 18.8% of shift workers. Regarding injuries to

themselves in the last two months, 27 regular workers (11.9%) seem to have self reported

accidents, while among shift workers, self reported accidents were only among 10 workers

(3.9%).This result is significantly different among both work groups. Again, this is not in

agreement with expected findings, with regard to current literature. This may be explained

by the different nature of work, as observed on the field and is elaborated in the discussion

part.

Job satisfaction was calculated as described previously, and workers were divided

into more satisfied with job and less satisfied with job. 114 regular workers seem to be more

satisfied with their job (55.1%).Comparably118 shift workers (47.4 %) also reported that they

were satisfied with their jobs. Irrespective of the nature of work (regular or shift) job

satisfaction was asked for, and reported by the workers.

Table 7-Accidents, injuries and job satisfaction among Regular and shift worker

Accidents Regular

worker

n(%)

Shift

worker

n(%)

Overall

n(%)

Odds ratio

(95% CI)

p value

Witness to accidents/injuries

occurred to anyone

44(19.6) 48(18.8) 92(19.1) .959

(.609-1.512)

.857

Accidents/injuries to self 27(11.9) 10(3.9) 37(7.7) .30

(.14-.63)

.001

Accidents on road way back

home after work/or at home

immediately after work

9(4) 18(7.1) 27(5.6) 1.80

(.794.12)

.153

More satisfied with Job 114(55.1) 118(47.4) 232(50.9) .76

(.51-1.06)

.102

41

The social and domestic life of the workers was assessed using the social and

domestic survey. The overall satisfaction score is not found to be significantly different

between the two groups of workers. As expected more shift workers reported more

satisfaction in finding time for domestic tasks, such as helping at home or looking after

children. They also found more time for their Non domestic activities such as going to bank,

hairdresser etc. Both these were significantly different between the two groups. Being

negatively coded, these had to be interpreted conversely-103 regular workers (56.9 %)

reported lesser time for domestic things, while 111 shift workers (45.7%) reported the same

problem. Again 86 regular workers reported that their work schedule interfered with non

domestic tasks (60.1%), while only 86 of their shift work counterparts (39%) reported the

same problem.

Table 8-Social and domestic situation among regular and shift worker.

Social and Domestic

situations (number of

respondents)

Regular

worker

n(%)

Shift

worker

n(%)

Overall

n(%)

Odds ratio

(95% CI)

p value

More satisfied with time

for Social and domestic

activities (301)

84(57.1) 80(51.9) 164(54.5) .88(.56-1.28) .366

Lesser time for

activities one like to do

( sports, hobbies..) (450)

94(47.7) 137(54.2) 231(51.3) 1.29(.89-1.88) .175

Lesser time for

domestic things(tasks,

children)(424)

103(56.9) 111(45.7) 214(50.5) .637(.432-.938) .022

Interfere with non

domestic activities (371)

86(60.1) 89(39) 175(47.2) .424(.277-1.56) <0.001

4.3.2. Associations of Insomnia or Excessive sleepiness, against various factors :Insomnia or

Excessive sleepiness was cross tabulated against various factors to look for its associations.

Age, years in service, body mass index, marital status, work schedule, Smoking, use of

42

alcohol and coffee or tea intake was the socio demographic variable and habits first examined

for associations. Work schedule, smoking and use of alcohol were found to be associated

with Insomnia or Excessive sleepiness

Table 9-Table showing results of bivariate analysis, done to look for associations of insomnia

or excessive sleepiness

Variables Insomnia or

Excessive

sleepiness -n

(%)

OR(95%CI)

for Sleep

disorder

Chi-Square

p-value.

Age(groups)

45-60 years 71(30.6 ) 1.07(0.72-1.58) .737

^20-44 years 73(29.2 )

Year in Service

More than 14 years 84(32.1) 1.25(0.85-1.86) .253

^Upto 14 years 60(27.3)

Body Mass

index

Overweight or obese 126(30.9) 1.39(.785-

2.461)

.257

^Normal BMI 18(24.3)

Marital status(n-

480)

Married

133(30.2) 1.10(0.532-

2.23)

.799

^ Unmarried 11(28.2)

Work schedule

Shift 103 (40.4) 3.07 (2.02-4.68) <0.001

^Regular 41(18.1)

Smoking

(Respondents-

450)

Smoking more than18

cigarettes per week

21(34.4)

<0.001

Smoking upto18

cigarettes per week

27(37.5)

^Non smokers 96(27.5)

Acohol use

(Respondents-

441)

Alcohol use more than

8 units per week

16(28.6)

<0.001 Alcohol use upto 8

units per week

47(47.5)

^Non users 81(24.8)

Tea or Coffee

intake

(Respondents-

466)

More than 4 cups per

day

38(30.6) 0.406

Upto 4 cups per day 97(30.8)

^Non users 9(20.9)

^-Reference category Variable names are emboldened if associations are significant

43

Next, the morbidities detected as part of the survey and the self reported morbidities

were examined for possible association with insomnia or excessive sleepiness.

Gastrointestinal problems, cardiovascular problems, mental health, hypertension, diabetes,

anxiety and depression were found to be significantly associated with Insomnia or excessive

sleepiness.

Table 10-Table showing results if bivariate analysis, done to look for associations of

insomnia or excessive sleepiness

Variables Insomnia

or

Excessive

sleepiness

-n (%)

OR(95%CI)

for Sleep

disorder

Chi-Square

p-value.

Gastro

intestinal

problems

Symptoms suggestive 78 (39.2) 2.07 (1.36-3.17) 0.001

^No symptoms suggestive 51(23.7)

Cardiovascular

problems

Symptoms suggestive 77 (38.7) 2.43 (1.57-3.74) <0.001

^No symptoms suggestive 46 (20.6)

Mental

health

Better mental health 49(22.5) .451(.296-.686)

<0.001 ^Poorer mental health 83(39.2)

Blood Pressure(self

reported)

Hypertensive 64(38.6) 1.85 (1.24-2.77) 0.003

^Non Hypertensive 79 (25.3)

Diabetes(self

reported)

Diabetic 55(38.7) 1.78 (1.18-2.70) 0.006

^Non-diabetic 88(26.2)

Anxiety(self

reported)

Anxiety 20 (43.5) 1.93 (1.04-3.59) 0.035

^No Anxiety disorder 123(28.5)

Depression (self reported)

Depressed

38 (47.5)

2.52 (1.54-4.12) 0.001

^No Clinical Depression

105(26.4)


44

Again, other morbidities like Gastric or duodenal ulcers, sinusitis or pharyngitis,

chronic backache, angina, arrhythmia, heart attacks, hypercholesterolemia and asthma were

examined for association with insomnia or excessive sleepiness. Gastric or duodenal ulcers,

sinusitis or pharyngitis, chronic backache, angina and Hypercholesterolemia were found to be

significantly associated with insomnia or excessive sleepiness.




Excessive

sleepiness -n

(%)

OR(95%CI) for

Sleep disorder

Chi-Square

p-value.

Gastric/Duodenal

Ulcers (self reported)

Ulcers 39(44.3) 2.19 (1.36-3.54) 0.001

^No ulcers 104 (26.6)

Sinusitis or

pharyngitis (self

reported)

Sinusitis/pha

ryngitis

35 (41.2) 1.9 (1.16-3.09) 0.001

^No

sinusitis or

pharyngitis

105 (26.9)

Chronic backache (self reported)

Backache 37 (48.1) 2.57 (1.56-4.24) <0.001

^No

Backache

106(26.4)

Angina(self reported) Angina 27 (56.3) 3.48 (1.89-6.39) <0.001

^No Angina 116(27.2)

Arrhythmia

(self reported)

Arrhythmia 25(38.5) 1.57(.912-2.705) .102

^No

Arrhythmia

117(28.5)

Heart attacks

(self reported)

Heart attack 8(44.4) 1.940(.749-

5.023)

.165

^No heart

attack

134(29.2)

Hypercholesterolemia (self reported)

Hypercholest

erolemia

50(38.5) 1.72 (1.12-2.63) 0.012

^Normal

cholesterol

levels

93(26.6)

Asthma

(self reported)

Asthmatic 26 (35.1) 1.35 (.797-2.27) .266

^Non-

asthmatic

116(28.7)


45

Finally, social and domestic life variable was also looked for associations. Overall

time available or socio domestic life, and the interference of work schedule on hobbies,

domestic activities and also for non domestic activities were looked for associations with

insomnia or excessive sleepiness. None were found to have significant correlations with

Insomnia or excessive sleepiness.




Excessive

sleepiness -n

(%)

OR(95%CI) for

Sleep disorder

Chi-Square

p-value.

Time available

for socio

domestic life

(Overall)

Better socio

domestic life

49(29.9) 1.24(.746-2.06) .404

^Poorer socio

domestic life

35(25.5)

Work schedule

Interference with

Hobbies

Interfered 73(31.6) 1.00(.675-1.49) .983

^No

interference

69(31.5)

Work schedule

Interference with

domestic activities

Interfered 66(30.8) .873(.581-1.31) .513

^No

interference

71(33.8)

Work schedule

Interference with

other non domestic

activities

Interfered 59(33.7) 1.03(.665-1.58) .911

^No

interference

65(33.2)


46

4.4Multivariate analysis

Following the results of bivariate analysis, variables found to be significantly associated with

insomnia or excessive sleepiness and also some variable like age, years in service were

analyzed by multivariate logistic regression.

Table 13-Results of multivariate logistic regression: Factors associated with Insomnia or

Excessive sleepiness, with no sleep disorder as the reference group –Model 1

Variables Adjusted OR for sleep

disorder(95% CI)

p-value.

Work schedule Shift workers 2.71 (1.58-4.66) <0.001

Regular workers

Angina(self

reported)

Angina 2.57(1.08-6.13) 0.033

No Angina

Model Nagelkerke R2: 0.235, Chi-square for the model: 67.175, p-value: <0.001

Other variables considered in this model and not found to be significant includes Symptoms

suggestive of GIT & CVS problems, BMI, Age, Years in service, and self reported Blood

Pressure, Diabetes ,Chronic Anxiety, Depression, Ulcers, Sinusitis/pharyngitis, Asthma,

Chronic backache, Angina ,Hypercholesterolemia ,Smoking and Use of alcohol.

Work schedule (OR 2.71,CI 1.58-4.66) and Angina (OR 2.57,CI 1.08-6.13) were

found to be independently associated with Insomnia or Excessive sleepiness.

47

Further, different models were explored for shift workers and regular workers.

For Regular workers, Symptoms suggestive of cardio vascular diseases was found to

have an independent association with insomnia or excessive sleepiness.

Table 14-Results of multivariate logistic regression among regular workers only: Factors

associated with Insomnia or Excessive sleepiness, with no sleep disorder as the reference

group –Model 2

Variable Adjusted OR for sleep

disorder(CI)

p value.

Symptoms suggestive

of cardiovascular

diseases

Has symptoms 3.43(2.90-5.16) 0.032

No symptoms

Model Nagelkerke R2: 0.273, Chi-square for the model: 31.769, p-value: 0.046


suggestive of GIT & CVS problems, BMI, Age, Yrs in service, and self reported Blood

Pressure, Diabetes ,Chronic Anxiety, Depression, Ulcers, Sinusitis, Asthma, Chronic

backache, Angina ,Hypercholesterolemia ,Smoking and Use of alcohol.

For Shift workers, symptoms suggestive of depression were found to have an

independent association with insomnia or excessive sleepiness.

Table 15-Results of multivariate logistic regression among shift workers only : Factors

associated with Insomnia or Excessive sleepiness, with no sleep disorder as the reference

group –Model 3

Variable Adjusted OR for sleep

disorder(CI)

p value.

Depression(self

reported

Depressed 3.62(1.45-8.995) 0.006

Not depressed

Model Nagelkerke R2: 0.215, Chi-square for the model: 34.06, p-value: 0.026


suggestive of GIT & CVS problems, BMI, Age, Yrs in service, and self reported Blood

Pressure, Diabetes ,Chronic Anxiety, Depression, Ulcers, Sinusitis/pharyngitis, Asthma,

Chronic backache, Angina ,Hypercholesterolemia ,Smoking and Use of alcohol.

48

4.5 Clinical tests-a bivariate analysis

This is the third set of analysis aimed to correlate the clinical findings between types

of workers.

A battery of clinical tests was done on a subsample of the workers, who had returned

the questionnaires, and also had consented to undergo clinical testing. Rey‘s Auditory Verbal

Learning, Trail A, Trail B, Digit span (forward and backward) were done on a subset of the

sample (30 regular workers and 30 shift worker) First the age and educational levels of both

groups of workers were analyzed and the difference was not found to be significantly

different (p value for age-0.508, p value across 4 categories- 0.478; Categories-masters,

degree or industrial training, passed 10th

standard, did not pass 10th

standard of educational

attainment)

Rey Auditory Verbal Learning tests (RAVLT) results were found to be significantly

different upon comparing the mean words learnt during each round of learning among the

two groups of workers.

Regarding memory,again the two groups were found to score significantly different

from each other. In Immediate recall tests, regular workers scored a mean score of 8.13+-

1.75,while the shift worker scored a mean of 5.97+-1.54.Also in delayed recall testing,

regular workers scored a mean score of 8.47+-2.417,while the shift workers scored a mean

score of 5.40+-1.45.

49

Table 16-Clinical test scores among Regular and shift worker

Regular worker(n=30) Shift worker(n=30) p values

Tests (mean+-SD) Median(IQR) (mean+-SD) Median(IQR) p value

for Mean

p value for

median

RAVLT1 6.20+-1.54 6(2) 5.43+-1.43 6(1.25) .05 .103

RAVLT2 8.83+-1.70 9(2.25) 7.40+-1.63 7(1.25) .002 .002

RAVLT3 10.40+-1.71 10(3) 8.80+-1.84 9(2) .001 .002

RAVLT4 11.71+-1.88 11.50(3.25) 10.17+-2.18 10(4) .004 .008

RAVLT5 12.87+-1.75 13(3.25) 11.13+-2.18 11(4.25) .003 .005

Immediate

recall

8.13+-1.75 8(2) 5.97+-1.54 6(2) <0.001 <0.001

Delayed

Recall

8.47+-2.417 8(3) 5.40+-1.45 5(2) <0.001 <0.001

Repeated measures anova test was done to see if learning across each round of

RAVLT (5 rounds) were significantly different among the work groups. It is seen that the

two groups are significantly different and the RAVLT scores in each round are also

significantly different. But the learning curve may not be significantly different.

Also it was checked if RAVLT was different across work schedule with insomnia or

excessive sleepiness adjusted using multiple factor repeated measures anova. It appears that

RAVLT scores across each round is significantly different across work groups even when

irrespective of insomnia or excessive sleepiness.

50

Table 17-Repeated Measures anova test of 5 rounds of RAVLT

Tested variables p value

Between Work Groups (regular and Shift work) .001

Between each round of RAVLT tests <0.001

Between work groups and Between RAVLT test

.171

Between workers with Insomnia or Excessive sleepiness and no

apparent sleep disorder

.042

Figure no.4.Box plot showing median works learnt by regular and shift workers across each

rounds in RAVLT-learning curve may not be significantly

differen

Regular workers Shift workers

51

Also, other tests such as trail A, Trail B, Digits pan forward and backward were done

on the two sets of workers. The results of these tests were not found to be significantly

different.

Table 18-Clinical test scores among Regular and shift worker

Tests Regular worker(n=30) Shift worker(n=30)

(mean+-SD) Median

(IQR)

(mean+-SD) Median

(IQR)

p value

For mean

p value

For median

Trail A 89.23+-

31.278

84(45) 91.90+-28.11 81(35.5) .730 .615

Trail B

185.07+-

54.32

179(73.3) 190.27+-

73.08

174(61)

.756 .935

Digit span

Forward

5.70+-1.31 6(1) 5.43+-1.61 5(2) .486 .425

Digit span

Backward

4.47+-1.35 4.5(1.5) 4.27+-1.43 4(1) .358 .517

Digit span

Total

10.23+-23 10(3) 9.69+-2.40 9(1.25) .310 .291

52

CHAPTER 5-DISCUSSION AND CONCLUSIONS

5.1. Discussion

The problems of working in shifts and it correlations with sleep are discussed first.

Secondly work schedule and its correlation with health, accidents and socio domestic life of

workers are discussed. Next, insomnia or excessive sleepiness and its correlates are

discussed. Finally the results of clinical tests are discussed.

5.1.1 Relation with sleep-Prevalence of insomnia or Excessive sleepiness

The prevalence of Insomnia, Excessive sleepiness and a combination of both is

significantly higher in the shift working group. This duly conforms to the available evidence

linking shift work and sleep disorders.14,17

When adjusted to age , according to the new World Health Organisation-2000-2005

standard population, the prevalence of shift work sleep disorder(insomnia or excessive

sleepiness) among this population is 30.74%. Similarly The prevalence of insomnia or

excessive sleepiness among regular workers is 26.14%.This rate is higher than what was

found by a similar study done by Drake and colleagues in Detroit, USA, and by Garbarino S

and colleagues among Italian policemen.14,19

This prevalence is however lower than what was found in several other studies in by

Hrma M and colleagues in Helsinki, Santos EH and and collegues in Brazil,and in a study by

Gold DR among hospital nurses.17,18,20

This is also lower than the estimate of sleep disorders

as estimated by the National sleep foundation Sleep in America poll.22

This difference of prevalence may be due to the various factors. The work

environment is tiring in Indian settings. Informally the workers may be taking rest or maybe

53

even naps in free hours. Also due to the reason that this is a survey conducted at workplaces,

it may have been under reported.

5.1.2. Shift work and other co morbidities

Working in shift was significantly associated with having symptoms of

gastrointestinal and also cardiovascular diseases.

It was seen than shift workers were about 1.52(1.03-2.24) times more likely to be

associated with symptoms of gastrointestinal diseases. They were also 2.3(1.55-3.4) times

more likely to be associated with symptoms of cardiovascular diseases. This is in

concordance with available literature in Japan, Italy and Helsinki which looked at

associations of shift work.54, 55,56,61,65

Stomach ulcers were seen to more than those reported abroad, but had a significantly

higher prevalence among the shift workers, as evidenced in Japan.57,58

.Similarly

Hypercholesterolemia and diabetes were seen to been more prevalent among shift workers,

which is in accordance with earlier research.59,60

Angina and hypertension are also found to

be significantly higher in the shift work group and is in agreement with available knowledge

regarding shift work.64,65

Sinusitis or pharyngitis is also found to be significantly associated

with shift work

Accidents and injuries looked for among the two groups suggest a rather uncommon

finding. In contrast to available literature ,in this population regular workers(11.9%) had

more accidents than their shift workmates(3.9%).4,14,67,68,69,70

This is explainable, considering

the work environment which drastically differs in the chemical plant where this study was

undertaken. Shift workers are mostly plant workers and run the automated chemical plant,

54

while regular workers are mostly maintenance workers, who repair and fix machinery.

Therefore regular workers probably have more occupational risks of accidents.

Next the socio domestic situations of the workers were looked into. 56.9 % of regular

workers reported lesser time for domestic things, while only 45.7% of shift workers reported

the same problem. Again 60.1% regular workers reported that their work schedule interfered

with non domestic tasks, while only 39 %of their shift work counterparts reported the same

problem. This is different from other published studies, which state poorer quality of life

among shift worlers.14

I t seems to suggest that shift workers in this population are at an

advantage here, being able to find time for domestic and other non domestic activities while

managing their works shift together

Regarding cognition and executive function, learning or attention here was not found

to be affected as found previously in other settings.74,75

.But memory, as tested by verbally

learnt words were found to be impaired both in the short term and long term.

5.1.3 Insomnia or Excessive sleepiness, and its correlates.

3 models were attempted to find out independent associations for insomnia or

excessive sleepiness-

1) A general model for all workers. 2) Model for regular workers. 3) Model for shift

workers. These models were built using by multivariate logistic regression by entry method,

using all variable which were found significant during bivariate analysis. Extra correlates

which were included were, age and years in service. Work schedule was duly excluded for

models two and three.

55

In general, Work schedule (OR 2.71,CI 1.58-4.66) and Angina (OR 2.57,CI 1.08-

6.13) were found to be independently associated with Insomnia or Excessive sleepiness

(model 1)

Among regular workers, symptoms suggestive of cardio vascular diseases were found

to have an independent association with insomnia or excessive sleepiness. Regular workers

with symptoms of cardiovascular disease were 3.43(OR 2.90-5.16) times more likely to be

associated with insomnia or excessive sleepiness.

Among shift workers, symptoms suggestive of cardio vascular diseases were found to

have an independent association with insomnia or excessive sleepiness. Shift workers with

depression were 3.62(OR 1.45-8.995) times more likely to be associated with insomnia or

excessive sleepiness.

5.1.4. Clinical tests done

30 regular workers and 30 shift workers were administered Rey Auditory Verbal

Learning, Trail A, Trail B, Digit span (forward and backward) .First the age and educational

levels of both groups of workers were analyzed and the difference was not found to be

significantly different.

Rey‘s Auditory Verbal Learning tests results were found to be significantly different

upon comparing the mean words learnt during each round of learning among the two groups

of workers.

While testing for Immediate and delayed recall, the two groups were found to score

significantly different from each other. In Immediate recall tests, regular workers scored a

mean score of 8.13+-1.75,while the shift worker scored a mean of 5.97+-1.54(p

56

value<0.001).Also in delayed recall testing, regular workers scored a mean score of 8.47+-

2.417,while the shift workers scored a mean score of 5.40+-1.45(p value-<0.001).

RAVLT measures were taken as progressive learning outcomes and analyzed.

Repeated measures anova test was done to see if learning across each round of RAVLT (5

rounds) were significantly different among the work groups. It is seen that the two groups are

significantly different and the RAVLT scores in each round are also significantly different.

But the learning curve was not found to be significantly different. This seems to suggest that

memory may be affected, while learning abilities may be spared. This has implications in the

personal and professional life of workers. More evidence needs to be collected as only verbal

learning was tested here.

Repeated measures anova test was against 2 factors done to check if RAVLT was

different across work schedule irrespective of insomnia or excessive sleepiness, as captured

by the study. It appears that RAVLT scores across each round is significantly different across

work groups even when adjusted for with insomnia or excessive sleepiness. This indicates

that irrespective of insomnia or excessive sleepiness, shift work seems to have an impact on

RAVLT scores. This requires further exploration and research.

Trail A, Trail B tests were done on the two sets of workers. These were done to look

for visual attention and task switching. The results of these tests were not found to be

significantly different.

Digit span forward and backward tests were used to check for short term memory.

These results were also were not found to be significantly different between the two work

groups.

57

5.2. Strengths and Limitations of the study.

• Strengths

– Among the early studies to look at effects of shift work especially among

industrial workers.

– Among the emerging studies in India looking at the nascent field of sleep

epidemiology.

– Collaborative effort between industrial health workers , public Health & Sleep

specialist(neurologist) to look at a occupational health problem, which has

public health implications.

– The study was designed and carried out in response to a Clinical observation

by a vigilant Occupational health specialist.

• Limitations

– Cross sectional study with all its inherent weaknesses. No causality can be

ascribed to associations.

– Morbidity variables were self reported, some of them could have been

measured in field with more resources.

58

5.3. Conclusions

Summarily, shift work seems to have a significant impact on health of workers.

It is seen to be associated with sleep disorders like Insomnia or Excessive Sleepiness,

or both. Regarding Insomnia or excessive sleepiness (shift work sleep disorder in the shift

working group as per definition), it seems to be significantly associated with work schedule

and also having angina, after having been adjusted for potential correlates and co morbidities.

Conclusively, working in shifts seems to be associated with sleep disorders.

Shift work is also associated with general health of the workers. Shift workers have

significantly more problems like ulcers, sinusitis, angina, hypertension, hypercholesterolemia

seen among them. Symptoms suggestive of gastro intestinal and cardiovascular problems are

also more among the shift workers. It seems to affect the memory (both immediate and

delayed) among workers, as suggested by clinical tests.

Interestingly in their Personal lives, more shift workers seem to find time for domestic

activities and non domestic personal matters, than their regular work mates.

More resources and research need to be directed in order to capture finer nuances of

the health problems of shift work. Screening for various disorders which have significant

associations with shift work needs to be considered as a policy outcome among industrial

workers.

59

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69

APPENDICES

Appendix A

Written informed consent form; English version

Consent form

I am Dr.Anoop Velayudhan, doing my Masters in Public Health,at the Achutha

Menon Centre for Health Science Studies (AMCHSS), Sree Chitra Tirunal Institute for

Medical Sciences and Technology, Trivandrum. As part of my research, I am conducting a

study titled ―Safety, health & social effects of shift work-a case of rapid rotating schedule

among male industrial workers‖, under the guidance of Assistant Professor Dr.Ravi Prasad

Varma.

I am studying the effect of shift work on health,safety social and personal life.I

assume that working at different periods of time and sleeping at different times each day

interrupts the body‘s internal rhythm. I intend to find out how many people have a form of

problem ,what we doctors call shift work sleep disorder,which is characterized by increased

sleepiness and lack of sleep as a result of shift work.

This study is expected to generate information regarding this problem and other

associated problems in the health and life of workers. The results of this study may act as

policy guidelines for industry and other workers.

I have prepared a sleep log,a work log and a questionnaire for you to respond to, with

assistance from me. A total of 560 persons shall be answering the same questionnaires, here

in this centre and another industry nearby.First I shall give you the sleep log to check for

changing sleep timings and collect it from you 2 weeks later.After 2 weeks,I would like you

to fill up this questionnaire and the work log for my study. This asks questions about your

personal details, your work details, your sleep details, your general health,and your social and

domestic situation.The work log is to chart out your work schedule.I shall also be testing

some of you randomly,for checking your alertness,concentration,presence of mind etc.It will

be a series of clinical,noninvasive which are some basic neurological screening tests.This will

take about 45 minutes to one hour.This will not cause any discomfort to you physically or

mentally. Please give me separate permission for this.

The whole procedure will take about 40-45 mins.You are free to withdraw from the

interview at any point of time. Also you can refuse to answer any question without giving any

explanations.

All information shall be made anonymous and recognizable by a DUMMY CODE ONLY (a

new number code that will be used to refer to you but is available with only me, stored in a

separate register maintained and accessible to me only).Your Name,employee code or any

personal information will be therefore be anonymised and know only to me. The information

obtained from you will be kept confidential, stored securely and will be used only for

research purpose. None of this information will be conveyed to the Management. Personal

details will never be revealed to the Industrial or Labour council. Only the final report of the

study will be published and made available to the industry and to also to you. This

70

information shall in no way will affect your career prospects, incentive, promotions or be

marked in your employee records or medical records.

I shall be happy to refer you to a doctor specializing in sleep medicine, a neurologist

if you happen to recognize and identify with some of the symptoms that you find here. Also

if this questionnaire suggests that you having a sleep problem, due to shift work I shall refer

you to a the sleep specialist at Sri Chitra Thirunal Centre for Science and Technology for

further management, in a discreet and confidential manner. For this I may have to access your

other medical records in total. if you are ok with this, please give me permission separately to

collect your Medical information available here in this industry in the following page.

If you have any queries or doubt, please feel free to clarify with me now.Later on, I shall be

available on phone at 9497758488. In case you need any clarifications about my credentials

or the study you can contact Dr. Ravi Prasad Varma, Assisstant Professor, AMCHSS,

SCTIMST, Thiruvananthapuram-695011 Tel: 0471-2436864 or Dr. Anoop Kumar

Thekkuveettil, Member-Secretary of the Institutional Ethical Committee at SCTIMST,

Thiruvananthapuram. Tel:0471-2348394

Signature of the Principle Investigator: ------------------

Time:

Date:

Place:

71

INFORMED CONSENT FORM

I ………………………………………………………………………………have understood

about the study,its wants and requirements.I have had an opportunity to ask questions and

clear my doubts.I am willing to participate in the study

Signature of the responder: ------------------

If you are not willing to take part thank you for your time, but could you please write down

your age and indicate your shift work patter for academic purposes?

Age………………… Shift work :

Regular day shift only

Rotating shift work.

I am willing to share your Medical records available in this institute with me(results of

monthly/yearly Medical tests, blood tests, available diagnoses etc)


I am willing to undergo this clinical tests to check for my memory, learning, alertness, coordination

etc.I understand that it will not affect me in any way.


Time:

Date:

Place:

72

APPENDIX B

Special Tools used in the study

1. General Job satisfaction questionnaire-question 2.7

SOURCE: Standard Shift Work Index, adapted from Hackman JR, Oldham

GR. Development of the Job Diagnostic Survey. Journal of Applied Psychology1975;

60: 159-170.This has five items and gives an overall measure of the degree to which

the employee is satisfied and happy with the job. This scale forms part of the larger

Job Diagnostic Survey (Hackman and Oldham 1975)

SCORING: A seven point response option was provided (range from disagree

strongly through disagree, disagree slightly, neutral, agree slightly, agree to agree

strongly)scored 1 to 7 with a median score being computed. Items B and E were

reversely scored.

2. Insomnia questionnaire- questions 3.13 to 3.27

Adapted from Comprehensive sleep questionnaire, Ray Mayo clinic, which

was altered in consultation with Sleep specialist and Neurologists.

3. Epworth Sleepiness Scale- question 3.28

SOURCE: The Epworth Sleepiness Scale (ESS) is a scale intended to measure

daytime sleepiness that is measured by use of a short questionnaire.

SCORING: The scores for the eight questions are added together to obtain a

single number. A number in the 0–9 range is considered to be normal while a number

in the 10–24 range indicated Excessive sleepiness

73

4. The Physical health questionnaire-Section 4 question 4.1 to 4.6

SOURCE: Standard Shift Work Index, adapted from Gianni Costa, Istituto di

Medicina del lavoro, Verona.

The physical health questionnaire contains two subscales, measuring cardiovascular and

gastrointestinal disorders, both known to have a high incidence in shift workers (8 questions

on each). A four point response option is used in order to avoid a tendency towards a central

answer. Subjects are asked to rate how frequently they experience symptoms, such as heart

palpitations and digestive difficulties. The response options are: almost never; quite seldom;

quite often; almost always.

A general screening questions was also included concerning diseases suffered

in most industrial settings. This was modified and included in consultations with

occupational health specialists. Subjects are asked to indicate on a yes/no response

option whether or not they have experienced any of the listed diseases.

SCORING: The two subscales, digestive and cardiovascular problems are

scored separately

A Likert type scale is used with response options ranging from 1 to 4, from

"almost never" to "almost always" or "definitely not" to "definitely".

5. General health questionnaire- question 4.7

SOURCE: Standard Shift Work Index, adapted from Goldberg DP. The

detection of psychiatric illness by questionnaire. 1972 Oxford: Oxford University

Press. The General Health Questionnaire is a self administered screening test for

detecting minor psychiatric disorders in the general population, and gives a single

74

measure of mental health. It covers recent levels of self-confidence, depression,

sleep loss and problem solving. Its 12 item version was chosen for the present study.

Four response options are provided for each item, e.g. better than usual, same as

usual, less than usual, much less than usual, with a higher score indicating poor

mental health.

SCORING: Multiple response scale was used instead of the bimodal scale.

The multiple-response scale or "Likert scale", was used where weights are assigned to

each position, e.g. the response options are scored 0, 1, 2 and 3, from "less so than

usual" to "much more than usual". A total score is then produced by adding together

each of the scores. A higher score indicated poorer psychological health.

6. Social and domestic survey -Section 5 question 5.1 to 5.5

SOURCE: Standard Shift Work Index, based on the Quality of Life Survey,

Section 4, used by Meredith Wallace and The Impairment in Social Activities scale of

the 1974-Survey, used by Friedhelm Nachreiner. The questionnaire consists of 19

items, covering social (e.g. sports, hobbies) and domestic (e.g. childcare, shopping)

activities. A 5 point response option was provided for Questions 5.1 - 5.4, ranging

from "not at all" to "very much".

SCORING:

Q 5.1A total score of general satisfaction by adding the item scores. The

higher the score the more satisfied.

Q 5.2 - 5.4-Separate scores were calculated for both these questions.

75

APPENDIX C

SLEEP LOG

The sleep log attempts to capture your sleeping time in hours.Please shade the hours you slept for the

last 2 weeks.

Eg

PM MIDNIGHT AM NOON

DAY 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5

Thursday

Friday

WEEK 1 PM MIDNIGHT AM NOON PM

DAY 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5

Thursday

Friday

Saturday

Sunday

Monday

Tuesday

Wednesday

WEEK 2 PM MIDNIGHT AM NOON PM

DAY 6 7 8 9 10 11 12 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5

Thursday

Friday

Saturday

Sunday

Monday

Tuesday

Wednesday

Documents

Shift Work: Health, safety and social effects a case of ...dspace.sctimst.ac.in/jspui/bitstream/123456789/2165/1/MPH_5990.pdf · Mrs.Jayanthi Bai, administrator, KMML. I am indebted