Occup. Med. 1992; 42: 193-199
Effects of a change in shift work on health C. J. M. Poole Hunters Rise, Clent, Worcestershire, UK G. R. Evans and A. Spurgeon Institute of Occupational Health, University of Birmingham, UK K. W. Bridges Department of Psychiatry, Manchester Royal Infirmary, UK
INTRODUCTION Disturbances of sleep and an increased prevalence of gastrointestinal symptoms have been reported by shift workers, but no long-term ill effects on health have been proved1"3. The night shift is usually the shift that is least well tolerated and so schemes with two or three nights, lates or earlies in a row may be preferable to more slowly rotating ones on the grounds that they do not require adaption of endogenous circadian rhythms4'5. On the other hand, slowly rotating shifts allow more time for biological adaption unless the shifts are discontinuous, eg with breaks at weekends. The optimum duration and sequence of shifts is unknown, but there is some evidence that 8 hour shifts are preferable to 12 hour shifts6 and that delaying (meaning that the start time of the shift is delayed, ie earlieslates-nights) rotations are preferable to advancing (nights-lates-earlies) rotations7'8. A spontaneous experiment arose in a large engineering factory when, because of increased production demands, 4000 paced track workers changed their pattern of working from 'fortnight about' (2 weeks of days alternating with 2 weeks of nights, weekdays only), to three advancing 8 hour shifts (5 days of lates, ie 14.00 to 22.00 h, followed by 5 days of earlies, ie 06.00 to 14.00 h, followed by 4 nights, ie 22.00 to 06.00 h, weekdays only). Workers within the same factory doing similar paced track work, but on a permanent 8 hour day shift, acted as a comparison group. A prospective longitudinal study was undertaken to observe changes in sleep disturbance, gastrointestinal symptoms, social functioning and mental health of a sample from the 4000 track workers, whose pattern of working was Correspondence and reprint requests to: C. J. M. Poole, MD, MRCP, Hunters Rise, Holy Cross Green, Clent, Worcestershire DY90HG, UK.
© 1992 Butterworth-Heinemann for SOM 0962-7480/92/040193-07
changed from 'fortnight about' to three advancing shifts. METHODS Study design Health assessment was by a 6 page questionnaire (Appendix). This was constructed so as to be capable of completion in 10 minutes, as employees could only participate during rest breaks. A brief verbal explanation of the project was given and where necessary help with understanding the questions, eg to those with poor literacy skills. Questionnaires were administered (1) 2 to 8 weeks prior to the change in shifts, whilst working 'fortnight about' and (2) 6 months after the change in shifts (to allow for stable adjustment to the new shift pattern), whilst working three shifts, to the same employees who acted therefore, as their own controls. During the 8 months of the study, track speeds did not change, although production was increased by the recruiting of an additional shift. Only employees who changed from the old two shift pattern to the new three shifts acted as subjects. Employees recruited specifically for the additional shift were not studied. A comparison group who were working on a similar process in the same factory, but on permanent days, completed the same questionnaire at the time that the study group was working three shifts. Both management and unions gave their consent and support to the project. Ethical clearance was obtained from the Central Birmingham Health Authority. Responses before and after the shift change were compared. Responses were further compared with the comparison group working days only. Non-parametric statistical tests (Wilcoxon's ranked pairs, Mann-Whitney U) and chi-square were used as appropriate. Significance was taken asp < 0.05.
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Aspects of health were studied in a sample of factory workers who changed their pattern of working from 'fortnight about' to three advancing shifts. Within the same factory and doing similar work there was a comparison group who were working permanent days only. The change in shifts was associated with more difficulty with sleep, more indigestion, higher alcohol consumption, reduced alertness and a worse social life. There was more minor psychiatric disturbance in those who worked three shifts than in those who worked days only.
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ASSESSMENTS
Table 1. Demography
Questions included: Male: Female Mean age (years) Married/cohabiting (%) UK or European (%)
3 Shifts
Days
5.1 33(18-64) 62 87
5.1 33(18-64) 61 88
6.1 36(20-60)*t 31*f 95
'Result significantly different from 'fortnight about', p < 0.01. tResult significantly different from three shifts, p < 0.01.
Table 2. Social functioning by visual analogue scales 'Fortnight about' mean ± sd Work enjoyment (0-7) Social life (0-7) Tension at home (0-7) Sex life (0-7)
4.0 ± 5.0 + 3.2 ± 4.8 ±
2.0 2.0 2.4 2.2
3 Shifts mean ± sd
Days mean ± sd
4.0 ± 4.5 + 2.9 + 4.3 ±
3.1 ±2.1*f 4.8 ± 2.2 2.5 ± 2.3* 4.7 ± 2.4
2.0 2.1* 2.3 2.3*
'Result significantly different from fortnight about', p < 0.05. tResult significantly different from three shifts, p < 0.05.
Table 3. Sleep disturbance and gastrointestinal symptoms 'Fortnight about'
3 Shifts
Days
Difficulty going to sleep Difficulty getting up Sleepy on the night shift
46 39 73f
55 50* 64
35f 37 N/A
Indigestion Heartburn Bowels open/day
22 21 1.2
35' 20 1.2
29 21 1.3
'Result significantly different from 'fortnight about', p < 0.05. tResult significantly different from three shirts, p < 0.01.
Subjects Subjects were recruited haphazardly (rather than strictly randomly) whilst they were working on the track, or relaxing in a rest station, and invited to take part in the study during their next break period by either CJMP or GRE. Less than 10 per cent of employees approached refused to take part, presumably for personal reasons. The number of subjects completing die questionnaire before the change in shifts was 212, with 189 of the same subjects completing the questionnaire 6 months later. As a result of some subjects leaving the factory for work elsewhere, illness or personal reasons, 23 were lost to follow up. Subjects who were working permanent days were selected in a similar way and 109 completed the same questionnaire. RESULTS 1. Demographic information indicated that there was no significant difference in the sex ratio or ethnic mix of die groups (Table 1). The mean age of the subjects working days only was 3 years higher than the shift workers (36 vs. 33 years) and significantly fewer of the days only workers were married or cohabiting.
2. Results of visual analogue scales to assess enjoyment of work, social life, tension at home and sex life are shown in Table 2. The quality of reported social and sex life was significantly worse on diree shifts than 'fortnight about'. Work enjoyment and tension at home were less in subjects who worked days only. There was no difference in the rating of social or sex life by the days only workers compared with the shift workers. 3. Reported mean weekly alcohol consumption increased from 12.0 units (range 0-115 units) on 'fortnight about' to 13.4 units (range 0-115 units) on three shifts (p < 0.05), but was highest in day only subjects, 17.8 units (range 0-76 units). Significantly more subjects on the days only shift had a high alcohol intake, ie > 50 units/week for men and > 35 units/week for women when compared with three shifts (chisquare = 4.6, p < 0.05). Mean weekly alcohol consumption in permanent day workers was significantly higher than those working 'fortnight about' but notsignificantly different from those working three shifts. 4. Percentages of subjects reporting difficulties with sleep and gastrointestinal symptoms are shown in Table 3. Difficulties with sleep and indigestion were
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1. Age, sex, ethnic origin and marital status. 2. Visual analogue scales (0 to 7) to assess enjoyment of work (0 = bad, 7 = good), social life (0 = bad, 7 = good), tension at home (0 = none, 7 = a lot) and sex life (0 = bad, 7 = good). 3. Alcohol consumption in the previous week in pints of beer, measures of spirit and glasses of wine. 4. Whether the subject had had difficulty going to sleep, getting up for work or felt sleepy on the night shift during the previous month. The presence of gastrointestinal symptoms such as abdominal pain, indigestion, or heartburn in the previous week and the number of bowel actions in the preceding 2 days. The number of times they had consulted a doctor in the last month. 5. The prevalence of psychiatric morbidity was estimated using the General Health Questionnaire (GHQ-28) 9 , anxiety and depression scales10, and a modified version of the Stress and Arousal Check List (SACL) n . These screening tests were chosen on the basis that they are widely used by doctors or psychologists, and reasonably well validated, albeit in non-industrial populations for the first two tests. 6. Comparisons were made of mean weekly total absence of the study population for the 10 weeks immediately before and after the change in shift pattern, as well as between the days only and three shift study populations for a corresponding 10 week period.
'Fortnight about'
C. J. M. Poole et al.: Changing shift work on health
195
DISCUSSION
Table 4. Psychological health 'Fortnight about' mean ± sd
3 Shifts mean ± sd
Days mean ± sd
QHQ-28
Not done
4.5 + 5.1
3.5 + 5.1
SACL-Stress SACL-Arousal
6.5 + 4.0 6.9 + 2.9
6.2 ± 4.1 6.3 + 3.2*
5.9 ± 4.2 6.9 ± 2.8
Anxiety > 4 Depression >4
26% 27%
24% 24%
20% 25%
Felt stressed
44%
44%
36%
'Result significantly different from 'fortnight about', p < 0.05. GHQ-28 = General Health Questionnaire-28 questions. SACL = Stress and Arousal Check List.
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commonest on three shifts. The mean number of consultations with a doctor in the previous month was similar in each group, 0.4 for 'fortnight about', 0.5 for three shifts and 0.5 for days only. 5. Results relating to psychological disturbances are shown in Table 4. The GHQ was not administered to subjects working 'fortnight about' because they were the first group to be sampled, and it was thought that the 28 questions would lengthen the questionnaire to such a degree that they would either not complete it or refuse to take part. As it turned out subjects were easily recruited and so the GHQ was included during three shifts and with days only workers. The mean total score (using GHQ scoring12) was not significantly higher on three shifts than days only. However, the number of subjects with high scores ( > 5 ) was higher on three shifts than days only (chi-square = 4.37,p < 0.05). The estimated prevalence of psychiatric morbidity12 was 28.2 per cent for three shifts and 9.9 per cent for days only. These estimates were based on variance-weighted means reported for the sensitivity and specificity of the GHQ-289'13, as it was not possible to measure validity coefficients in the subjects of this study. There was no correlation between a high GHQ score and leaving the company within 10 months. Women were represented more frequently in the top 20 per cent of GHQ scores (chi-square = 4.37, p < 0.05). The anxiety and depression scales correlated with the GHQ-28 total scores (anxiety r = 0.57 and depression r = 0.63) but there were no significant differences in the proportions reporting high scores ( > 5 for anxiety, >4 for depression) between the groups {Table 4). There were no significant differences in mean stress scores between the groups. This may be because the anxiety and depression scales and Stress and Arousal Check Lists were insufficiently sensitive to detect such differences. The mean arousal scores however, deteriorated significantly from 'fortnight about' to three shifts. 6. Mean weekly total absence for the 10 weeks before and after the change in shifts was 8.3 and 7.6 per cent respectively (not significantly different). The corresponding figure for days only workers was 9.0 per cent which was not significantly different from three shift workers.
The change from 'fortnight about' to three shifts was associated with a deterioration in some aspects of health. In particular social and sex life were worse, possibly due to the disruption to normal family dynamics and recreation that this pattern of working creates. For example, evening socializing is reduced as the worker has either to go to bed early in preparation for the early shift or, by the end of the late shift most social activities have finished. Alcohol consumption increased on three shifts but was still comparable to the 9.4 units per week reported for the general population14. Days only workers had the highest mean alcohol consumption and the highest proportion of heavy drinkers, possibly because of the increased opportunities to drink. Drinking is very much related to age and sex, with men between 18 and 24 years, who form a large proportion of this workforce, drinking most alcohol14. The mean weekly consumption of alcohol for male and female medical students for example, in one study was respectively 20.5 and 14.6 units per week15. Sleep disturbance occurred more frequently after the change to three shifts and was more common than in those on days only. However sleepiness on the night shift was reported more commonly on 'fortnight about' probably due to the longer duration of the night shift. Indigestion was also more common on three shifts possibly related to meal breaks being only 15 minutes in duration every 2 hours. Levels of anxiety and depression did not change significantly from 'fortnight about' to three shifts but were higher for example, than those reported in a group of offshore oil workers.16 One of the problems with using anxiety and depression scales to assess the prevalence of psychiatric morbidity is that they were not developed for use as a self-assessment questionnaire, but as a research tool for psychiatrists to be used in conjunction with informed clinical judgement to assess the subject's response to each question. It is also uncertain which threshold scores should be used in a non-clinical group of subjects, however the relatively high cut-off score used here is likely to include the least number of false positives. Levels of stress did not change significantly with the change in shifts, but were in all groups a little higher than have been previously reported for industrial populations17. This may be because the work of the majority of subjects in this study was monotonous and paced with little or no job rotation. The change from 'fortnight about' to three shifts was associated with a fall in arousal. The cause of this cannot be determined from this study, but may be related to the increased difficulties with sleep that were reported following the change in shifts. Using the GHQ scores the estimated prevalence of psychiatric morbidity in this study was 28 per cent on three shifts and 10 per cent on days only. The authors know of no similar study in an industrial population using GHQ-28. Other forms of the GHQ (ie 12, 30
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three shifts from 'fortnight about' appears to have had a detrimental effect on several aspects of health. Days only work was associated with less sleep disturbance and better mental health than three shifts work. REFERENCES 1. Harrington JM. Shift Work and Health. London: HMSO, 1978. 2. Akerstedt T. Psychological and psychophysiological effects of shift work. ScandJ Work Environ Health 1990; 16(suppl 1), 67-73. 3. Knauth P, Rutenfranz F. Shiftwork. In: Harrington JM 4. 5.
6. 7.
8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.
(ed.), Recent Advances in Occupational Health Vol. 3. London: Churchill Livingstone, 1987; 263-81. Walker J. Frequent alteration of shifts on continuous work. Occup Psychol 1966; 40: 215-25. Halberg F. Some aspects of chronobiology relating to the optimization of shift work. In: Shift Work and Health. Washington DC: US Govt. Printing Office, 1976; 76-203. Smith M, Vernon MD. A study of the 2-shift system in certain factories. Industrial Fatigue Research Board Report No 47. London: HMSO, 1928. Anonymous. Final Report on the Philadelphia Police Department Shift Rescheduling Program. Center for Design of Industrial Schedules. Boston, Massachusetts, 1988. Knauth P, Kiesswetter E. A change from weekly to quicker shift rotations: a field study of discontinuous three shift workers. Ergonomics 1987; 30: 1311-21. Goldberg DP, Williams P. A users guide to the General Health Questionnaire. Windsor: Nfer-Nelson, 1988. Goldberg DP, Bridges KW, Duncan-Jones P, Grayson D. Detecting anxiety and depression in general medical settings. Br Med J 1988; 297: 897-9. Mackay C, Cox T, Burrows G, Lazzerini T. An inventory for the measurement of self-reported stress and arousal. BrJSoc Clin Psychol 1978; 17: 283-4. GoldbergDP. Manualofthe General Health Questionnaire. Windsor: Nfer-Nelson, 1978. Bridges KW, Goldberg DP. The validation of the GHQ-28 and the use of the M.M.S.E. in neurological in-patients. Br J Psychiatry 1986; 148: 548-53. Goddard E, Ikin C. Drinking in England and Wales in 1987. Office Population Censuses and Surveys. London: HMSO, 1988. Collier DJ, Beales ILP. Drinking among medical students: a questionnaire survey. Br Med J 1989; 299: 19-22. Gann M, Corpe U, Wilson I. The application of a short anxiety and depression questionnaire to oil industry staff. J Soc Occup Med 1990; 40: 138-42. Cox T. The recognition and measurement of stress. In: Wilson JR, Corlett EN (eds), Evaluation of Human Work. Taylor and Francis, 1989; 628-47. Bridges KW, Goldberg DP. Psychiatric illness in patients with neurological disorder. Br Med J 1984; 289: 656-8. Bridges KW, Goldberg DP. Somatic presentation of DSM III psychiatric disorders in primary care. J Psychosom Res 29: 563-9. Goldberg DP, Kay C, Thompson L. Psychiatric morbidity in general practice and the community. Psychol Med 1976; 6: 565-9. Finlay-Jones RA, Burvill PW. The prevalence of minor psychiatric morbidity in the community. Psychol Med 1977; 7: 475-89. Duncan Jones P, Henderson S. The use of a two-phase design in a prevalence survey. Soc Psychiatry 1978; 13: 231-7. Office of Population Censuses and Surveys, General Household Survey. London: HMSO, 1988.
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and 60) have been used in occupational groups such as nurses, doctors, social workers and pharmacists9, but not factory workers. In those studies that have used the GHQ-28 the above prevalence rates compare with 39 per cent in a group of neurology inpatients18, 33 per cent in a study of patients with new illness in primary care19 and between 8 and 18 per cent in three community studies20"22. That is, psychiatric morbidity on three shifts appears to be in keeping with patients consulting doctors, whereas psychiatric morbidity in days only workers appears to be more in keeping with community studies. These findings should be treated with caution as the calculation for psychiatric morbidity is based on sensitivity and specificity values determined by other studies on different subjects. We would have liked to have validated the use of the GHQ-28 in this factory, but time restraints to interview subjects and the lack of privacy, prevented us from doing a standardized research interview such as the Present State Examination, on a sub-group of the sample. One of the conditions for management granting consent for this study to take place was that the questionnaires could only be administered in the employees' own time, which during three shifts meant in practice during one of three 15 minute breaks. Ideally subjects should have been recruited randomly from personnel records rather than haphazardly on the track, but this was not done for practical reasons. The results do suggest however that advancing three shift work is associated with more psycho-social disturbance than with day only work, and with the 'fortnight about' type of shift pattern. This observation is worthy of more vigorous study to identify aetiological factors and vulnerable groups who might benefit from additional support such as counselling. Despite the differences noted above there was no significant difference in the mean weekly total absence on three shifts compared with 'fortnight about', possibly reflecting the effects of factors unrelated to health on absence attributed to sickness. Consultation rates with general practitioners vary with age and socio-economic group 23 . The subjects in this study consulted a doctor on average once every two months, which compares with once every four months in the 1988 General Household Survey23. The reasons for the relatively high consultation rates with doctors in both shift and day workers cannot be determined by this study, but may be related to some of the disturbances in health identified in this study. The reason for the lower enjoyment of work of the day only subjects is unknown, but may be related to the older process, albeit paced and track tied, on which they were working. It is tempting to suggest that their reported lower level of tension at home was associated with them not working shifts, but the effects of other confounding variables, such as higher age and fewer married or cohabiting subjects in this group may also be relevant. Less difficulty with sleeping is well reported for day only workers, yet it is interesting to note that one third reported difficulty sleeping. In conclusion, the change to discontinuous advancing
C. J. M. Poole et ai: Changing shift work on health
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APPENDIX: QUESTIONNAIRE [ ]M
1. Sex 2. Edinic Origin
[ ] UK & Irish
[ ] African
[ ] Caribbean
[
[ ] t 1 Asian European (Indian-subcontinent)
[ ] Other
3. Age 4. Current marital status
[ ]
Single
[ ]
Married or Cohabiting
[ ]
Separated or Divorced
[ ]
Widowed
5. Number of children at home (Please circle) 0
1 2
3
6. How many times have you consulted a doctor in the last month?
4
5
or more
[ ]
[ ]
pints of beer
[ ]
glasses of shorts/spirits
[ ]
glasses of wine
8. Have you had any tummy pain or indigestion in the last week?
[ ] YES
[ ] NO
9. Have you had any burning behind the breastbone (heartburn) in the last week?
[ ] YES
[ ] NO
10. How many times have you opened your bowels in the last 2 days?
[ ]
In the last month have you-
YES
NO
1. felt keyed up or on edge?
[ ]
[ ]
2. been worrying a lot?
[ ]
[ ]
3. been irritable?
[ ]
[ ]
4. had difficulty relaxing?
[ ]
[ ]
5. been sleeping poorly?
[ ]
[ ]
6. had headaches or neck aches?
[ ]
[ ]
sweating, frequency or diarrhoea?
[ ]
[ ]
8. been worried about your health?
[ ]
[ ]
9. had difficulty falling asleep?
[ ]
[ ]
YES
NO
1. been low in energy?
[ ]
[ ]
2. had loss of interests?
[ ]
[ ]
3. lost confidence in yourself?
[ ]
[ ]
4. felt hopeless?
[ ]
[ ]
5. had difficulty concentrating?
[ ]
[ ]
6. lost weight (due to poor appetite)?
[ ]
[ ]
7. been waking early?
[ ]
[ ]
8. felt slowed up?
[ ]
[ ]
9. tended to feel worse in the mornings?
[ ]
[ ]
(if yes to two of the above, go on to answer)
7. had any trembling, tingling, dizzy spells,
In the last month have you-
(if yes to any questions, go on to answer)
Please answer ALL the questions on the following two pages simply by underlining the answer which you think most nearly
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7. How much alcohol have you drunk in the last week, including the weekend?
198 Occup. Med. 1992, Vol. 42, No 4
applies to you. Remember that I want to know about present and recent complaints, not those that you had in the past. It is important that you try to answer ALL the questions. Over the last few weeks have you: Al. Been feeling perfectly well and in good health? A2. Been feeling in need of a good tonic?
Better than usual Not
at all A3. Been feeling run down and out of sorts?
Not
at all A4. Felt that you are ill?
Not
at all A5. Been getting any pains in your head?
Not
at all Not
Bl. Lost much sleep over worry?
Not
B2. Had difficulty in staying asleep once you are off? B3. Felt constantly under strain?
Not
Not
at all at all at all at all Not
at all B4. Been getting edgy and bad-tempered?
Not
at all B5. Been getting scared or panicky for no good reason? B6. Found everything getting on top of you?
Not
at all Not
at all B7. Been feeling nervous and strung-up all the time? Cl. Been managing to keep yourself busy and occupied? C2. Been taking longer over the things you do? C3. Felt on the whole you were doing things well ? C4. Been satisfied with the way you've carried out your task? C5. Felt that you are playing a useful part in things ? C6. Felt capable of making decisions about things? C7. Been able to enjoy your normal day-to-day activities ? D l . Been thinking of yourself as a worthless person ? D2. Felt that life is entirely hopeless?
Not
at all More so than usual Quicker than usual Better than usual More satisfied More so than usual More so than usual More so than usual Not
at all Not
at all D3. Felt that life isn't worth living? D4. Thought of the possibility that you might make away with yourself? D5. Found at times you couldn't do anything because your nerves were too bad? D6. Found yourself wishing you were dead and away from it all? D7. Found that the idea of taking your own life kept coming into your mind?
Not
at all Definitely not Not
at all Not
at all Definitely not
Worse than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather less than usual Longer than usual Less well than usual Less satisfied than usual Less useful than usual Less so than usual Less so than usual Rather more than usual Rather more than usual Rather more than usual Has crossed my mind Rather more than usual Rather more than usual Has crossed my mind
Much worse than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much less than usual Much longer than usual Much less well Much less satisfied Much less useful Much less capable Much less than usual Much more than usual Much more than usual Much more than usual Definitely have Much more than usual Much more than usual Definitely has
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A6. Been getting a feeling of tightness or pressure in your head? A7. Been having hot or cold spells?
Same as usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual Same as usual Same as usual About the same About same as usual Same as usual Same as usual Same as usual No more than usual No more than usual No more than usual I don't think so No more than usual No more than usual I don't think so
C. J. M. Poole et at:. Changing shift work on health
199
For each of the following words please circle the response which most applies to how you are feeling at the moment: Eg. If very tense then circle + + , if not at all tense then circle —
Answer the following questions by circling one of the numbers on a scale from 0 to 7: How would you rate your enjoyment of work? (bad)
0
1 2
3
4
(good)
4
(good)
How would you rate your social life? (bad)
0
1 2
3
How would you rate tension at home? (good)
0
1 2
3
4
(bad)
How would you rate your sex life? (bad)
0
1 2
3
4
(good)
In the last month have you: -had any difficulty going to sleep?
Yes[ ]
No[ ]
-had difficulty getting up for work?
Yes[ ]
No[ ]
-felt stressed?
Yes[ ]
No[ ]
-felt sleepy on the night shift?
Yes[ ]
No[ ]
Do you prefer to work: 3 shifts [ ]
or fortnight about [ ]
Thank you very much for your co-operation
or straight days[
or straight nights
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TIRED IDLE UPTIGHT CHEERFUL LIVELY INFURIATED CONTENTED JITTERY SLUGGISH PLEASANT SLEEPY COMFORTABLE CALM STIMULATED ACTIVATED FRIGHTENED IRRITATED ALERT HURRIED BUSY
TENSE ANGRY RESTFUL ACTIVE APPREHENSIVE WORRIED ENERGETIC DROWSY BOTHERED UNEASY DEJECTED NERVOUS BAD TEMPERED VIGOROUS PEACEFUL STEADY RELAXED DISTRESSED PUSHED PRESSED
Effects of a change in shift work on health C. J. M. Poole Hunters Rise, Clent, Worcestershire, UK G. R. Evans and A. Spurgeon Institute of Occupational Health, University of Birmingham, UK K. W. Bridges Department of Psychiatry, Manchester Royal Infirmary, UK
INTRODUCTION Disturbances of sleep and an increased prevalence of gastrointestinal symptoms have been reported by shift workers, but no long-term ill effects on health have been proved1"3. The night shift is usually the shift that is least well tolerated and so schemes with two or three nights, lates or earlies in a row may be preferable to more slowly rotating ones on the grounds that they do not require adaption of endogenous circadian rhythms4'5. On the other hand, slowly rotating shifts allow more time for biological adaption unless the shifts are discontinuous, eg with breaks at weekends. The optimum duration and sequence of shifts is unknown, but there is some evidence that 8 hour shifts are preferable to 12 hour shifts6 and that delaying (meaning that the start time of the shift is delayed, ie earlieslates-nights) rotations are preferable to advancing (nights-lates-earlies) rotations7'8. A spontaneous experiment arose in a large engineering factory when, because of increased production demands, 4000 paced track workers changed their pattern of working from 'fortnight about' (2 weeks of days alternating with 2 weeks of nights, weekdays only), to three advancing 8 hour shifts (5 days of lates, ie 14.00 to 22.00 h, followed by 5 days of earlies, ie 06.00 to 14.00 h, followed by 4 nights, ie 22.00 to 06.00 h, weekdays only). Workers within the same factory doing similar paced track work, but on a permanent 8 hour day shift, acted as a comparison group. A prospective longitudinal study was undertaken to observe changes in sleep disturbance, gastrointestinal symptoms, social functioning and mental health of a sample from the 4000 track workers, whose pattern of working was Correspondence and reprint requests to: C. J. M. Poole, MD, MRCP, Hunters Rise, Holy Cross Green, Clent, Worcestershire DY90HG, UK.
© 1992 Butterworth-Heinemann for SOM 0962-7480/92/040193-07
changed from 'fortnight about' to three advancing shifts. METHODS Study design Health assessment was by a 6 page questionnaire (Appendix). This was constructed so as to be capable of completion in 10 minutes, as employees could only participate during rest breaks. A brief verbal explanation of the project was given and where necessary help with understanding the questions, eg to those with poor literacy skills. Questionnaires were administered (1) 2 to 8 weeks prior to the change in shifts, whilst working 'fortnight about' and (2) 6 months after the change in shifts (to allow for stable adjustment to the new shift pattern), whilst working three shifts, to the same employees who acted therefore, as their own controls. During the 8 months of the study, track speeds did not change, although production was increased by the recruiting of an additional shift. Only employees who changed from the old two shift pattern to the new three shifts acted as subjects. Employees recruited specifically for the additional shift were not studied. A comparison group who were working on a similar process in the same factory, but on permanent days, completed the same questionnaire at the time that the study group was working three shifts. Both management and unions gave their consent and support to the project. Ethical clearance was obtained from the Central Birmingham Health Authority. Responses before and after the shift change were compared. Responses were further compared with the comparison group working days only. Non-parametric statistical tests (Wilcoxon's ranked pairs, Mann-Whitney U) and chi-square were used as appropriate. Significance was taken asp < 0.05.
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Aspects of health were studied in a sample of factory workers who changed their pattern of working from 'fortnight about' to three advancing shifts. Within the same factory and doing similar work there was a comparison group who were working permanent days only. The change in shifts was associated with more difficulty with sleep, more indigestion, higher alcohol consumption, reduced alertness and a worse social life. There was more minor psychiatric disturbance in those who worked three shifts than in those who worked days only.
194
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ASSESSMENTS
Table 1. Demography
Questions included: Male: Female Mean age (years) Married/cohabiting (%) UK or European (%)
3 Shifts
Days
5.1 33(18-64) 62 87
5.1 33(18-64) 61 88
6.1 36(20-60)*t 31*f 95
'Result significantly different from 'fortnight about', p < 0.01. tResult significantly different from three shifts, p < 0.01.
Table 2. Social functioning by visual analogue scales 'Fortnight about' mean ± sd Work enjoyment (0-7) Social life (0-7) Tension at home (0-7) Sex life (0-7)
4.0 ± 5.0 + 3.2 ± 4.8 ±
2.0 2.0 2.4 2.2
3 Shifts mean ± sd
Days mean ± sd
4.0 ± 4.5 + 2.9 + 4.3 ±
3.1 ±2.1*f 4.8 ± 2.2 2.5 ± 2.3* 4.7 ± 2.4
2.0 2.1* 2.3 2.3*
'Result significantly different from fortnight about', p < 0.05. tResult significantly different from three shifts, p < 0.05.
Table 3. Sleep disturbance and gastrointestinal symptoms 'Fortnight about'
3 Shifts
Days
Difficulty going to sleep Difficulty getting up Sleepy on the night shift
46 39 73f
55 50* 64
35f 37 N/A
Indigestion Heartburn Bowels open/day
22 21 1.2
35' 20 1.2
29 21 1.3
'Result significantly different from 'fortnight about', p < 0.05. tResult significantly different from three shirts, p < 0.01.
Subjects Subjects were recruited haphazardly (rather than strictly randomly) whilst they were working on the track, or relaxing in a rest station, and invited to take part in the study during their next break period by either CJMP or GRE. Less than 10 per cent of employees approached refused to take part, presumably for personal reasons. The number of subjects completing die questionnaire before the change in shifts was 212, with 189 of the same subjects completing the questionnaire 6 months later. As a result of some subjects leaving the factory for work elsewhere, illness or personal reasons, 23 were lost to follow up. Subjects who were working permanent days were selected in a similar way and 109 completed the same questionnaire. RESULTS 1. Demographic information indicated that there was no significant difference in the sex ratio or ethnic mix of die groups (Table 1). The mean age of the subjects working days only was 3 years higher than the shift workers (36 vs. 33 years) and significantly fewer of the days only workers were married or cohabiting.
2. Results of visual analogue scales to assess enjoyment of work, social life, tension at home and sex life are shown in Table 2. The quality of reported social and sex life was significantly worse on diree shifts than 'fortnight about'. Work enjoyment and tension at home were less in subjects who worked days only. There was no difference in the rating of social or sex life by the days only workers compared with the shift workers. 3. Reported mean weekly alcohol consumption increased from 12.0 units (range 0-115 units) on 'fortnight about' to 13.4 units (range 0-115 units) on three shifts (p < 0.05), but was highest in day only subjects, 17.8 units (range 0-76 units). Significantly more subjects on the days only shift had a high alcohol intake, ie > 50 units/week for men and > 35 units/week for women when compared with three shifts (chisquare = 4.6, p < 0.05). Mean weekly alcohol consumption in permanent day workers was significantly higher than those working 'fortnight about' but notsignificantly different from those working three shifts. 4. Percentages of subjects reporting difficulties with sleep and gastrointestinal symptoms are shown in Table 3. Difficulties with sleep and indigestion were
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1. Age, sex, ethnic origin and marital status. 2. Visual analogue scales (0 to 7) to assess enjoyment of work (0 = bad, 7 = good), social life (0 = bad, 7 = good), tension at home (0 = none, 7 = a lot) and sex life (0 = bad, 7 = good). 3. Alcohol consumption in the previous week in pints of beer, measures of spirit and glasses of wine. 4. Whether the subject had had difficulty going to sleep, getting up for work or felt sleepy on the night shift during the previous month. The presence of gastrointestinal symptoms such as abdominal pain, indigestion, or heartburn in the previous week and the number of bowel actions in the preceding 2 days. The number of times they had consulted a doctor in the last month. 5. The prevalence of psychiatric morbidity was estimated using the General Health Questionnaire (GHQ-28) 9 , anxiety and depression scales10, and a modified version of the Stress and Arousal Check List (SACL) n . These screening tests were chosen on the basis that they are widely used by doctors or psychologists, and reasonably well validated, albeit in non-industrial populations for the first two tests. 6. Comparisons were made of mean weekly total absence of the study population for the 10 weeks immediately before and after the change in shift pattern, as well as between the days only and three shift study populations for a corresponding 10 week period.
'Fortnight about'
C. J. M. Poole et al.: Changing shift work on health
195
DISCUSSION
Table 4. Psychological health 'Fortnight about' mean ± sd
3 Shifts mean ± sd
Days mean ± sd
QHQ-28
Not done
4.5 + 5.1
3.5 + 5.1
SACL-Stress SACL-Arousal
6.5 + 4.0 6.9 + 2.9
6.2 ± 4.1 6.3 + 3.2*
5.9 ± 4.2 6.9 ± 2.8
Anxiety > 4 Depression >4
26% 27%
24% 24%
20% 25%
Felt stressed
44%
44%
36%
'Result significantly different from 'fortnight about', p < 0.05. GHQ-28 = General Health Questionnaire-28 questions. SACL = Stress and Arousal Check List.
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commonest on three shifts. The mean number of consultations with a doctor in the previous month was similar in each group, 0.4 for 'fortnight about', 0.5 for three shifts and 0.5 for days only. 5. Results relating to psychological disturbances are shown in Table 4. The GHQ was not administered to subjects working 'fortnight about' because they were the first group to be sampled, and it was thought that the 28 questions would lengthen the questionnaire to such a degree that they would either not complete it or refuse to take part. As it turned out subjects were easily recruited and so the GHQ was included during three shifts and with days only workers. The mean total score (using GHQ scoring12) was not significantly higher on three shifts than days only. However, the number of subjects with high scores ( > 5 ) was higher on three shifts than days only (chi-square = 4.37,p < 0.05). The estimated prevalence of psychiatric morbidity12 was 28.2 per cent for three shifts and 9.9 per cent for days only. These estimates were based on variance-weighted means reported for the sensitivity and specificity of the GHQ-289'13, as it was not possible to measure validity coefficients in the subjects of this study. There was no correlation between a high GHQ score and leaving the company within 10 months. Women were represented more frequently in the top 20 per cent of GHQ scores (chi-square = 4.37, p < 0.05). The anxiety and depression scales correlated with the GHQ-28 total scores (anxiety r = 0.57 and depression r = 0.63) but there were no significant differences in the proportions reporting high scores ( > 5 for anxiety, >4 for depression) between the groups {Table 4). There were no significant differences in mean stress scores between the groups. This may be because the anxiety and depression scales and Stress and Arousal Check Lists were insufficiently sensitive to detect such differences. The mean arousal scores however, deteriorated significantly from 'fortnight about' to three shifts. 6. Mean weekly total absence for the 10 weeks before and after the change in shifts was 8.3 and 7.6 per cent respectively (not significantly different). The corresponding figure for days only workers was 9.0 per cent which was not significantly different from three shift workers.
The change from 'fortnight about' to three shifts was associated with a deterioration in some aspects of health. In particular social and sex life were worse, possibly due to the disruption to normal family dynamics and recreation that this pattern of working creates. For example, evening socializing is reduced as the worker has either to go to bed early in preparation for the early shift or, by the end of the late shift most social activities have finished. Alcohol consumption increased on three shifts but was still comparable to the 9.4 units per week reported for the general population14. Days only workers had the highest mean alcohol consumption and the highest proportion of heavy drinkers, possibly because of the increased opportunities to drink. Drinking is very much related to age and sex, with men between 18 and 24 years, who form a large proportion of this workforce, drinking most alcohol14. The mean weekly consumption of alcohol for male and female medical students for example, in one study was respectively 20.5 and 14.6 units per week15. Sleep disturbance occurred more frequently after the change to three shifts and was more common than in those on days only. However sleepiness on the night shift was reported more commonly on 'fortnight about' probably due to the longer duration of the night shift. Indigestion was also more common on three shifts possibly related to meal breaks being only 15 minutes in duration every 2 hours. Levels of anxiety and depression did not change significantly from 'fortnight about' to three shifts but were higher for example, than those reported in a group of offshore oil workers.16 One of the problems with using anxiety and depression scales to assess the prevalence of psychiatric morbidity is that they were not developed for use as a self-assessment questionnaire, but as a research tool for psychiatrists to be used in conjunction with informed clinical judgement to assess the subject's response to each question. It is also uncertain which threshold scores should be used in a non-clinical group of subjects, however the relatively high cut-off score used here is likely to include the least number of false positives. Levels of stress did not change significantly with the change in shifts, but were in all groups a little higher than have been previously reported for industrial populations17. This may be because the work of the majority of subjects in this study was monotonous and paced with little or no job rotation. The change from 'fortnight about' to three shifts was associated with a fall in arousal. The cause of this cannot be determined from this study, but may be related to the increased difficulties with sleep that were reported following the change in shifts. Using the GHQ scores the estimated prevalence of psychiatric morbidity in this study was 28 per cent on three shifts and 10 per cent on days only. The authors know of no similar study in an industrial population using GHQ-28. Other forms of the GHQ (ie 12, 30
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three shifts from 'fortnight about' appears to have had a detrimental effect on several aspects of health. Days only work was associated with less sleep disturbance and better mental health than three shifts work. REFERENCES 1. Harrington JM. Shift Work and Health. London: HMSO, 1978. 2. Akerstedt T. Psychological and psychophysiological effects of shift work. ScandJ Work Environ Health 1990; 16(suppl 1), 67-73. 3. Knauth P, Rutenfranz F. Shiftwork. In: Harrington JM 4. 5.
6. 7.
8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23.
(ed.), Recent Advances in Occupational Health Vol. 3. London: Churchill Livingstone, 1987; 263-81. Walker J. Frequent alteration of shifts on continuous work. Occup Psychol 1966; 40: 215-25. Halberg F. Some aspects of chronobiology relating to the optimization of shift work. In: Shift Work and Health. Washington DC: US Govt. Printing Office, 1976; 76-203. Smith M, Vernon MD. A study of the 2-shift system in certain factories. Industrial Fatigue Research Board Report No 47. London: HMSO, 1928. Anonymous. Final Report on the Philadelphia Police Department Shift Rescheduling Program. Center for Design of Industrial Schedules. Boston, Massachusetts, 1988. Knauth P, Kiesswetter E. A change from weekly to quicker shift rotations: a field study of discontinuous three shift workers. Ergonomics 1987; 30: 1311-21. Goldberg DP, Williams P. A users guide to the General Health Questionnaire. Windsor: Nfer-Nelson, 1988. Goldberg DP, Bridges KW, Duncan-Jones P, Grayson D. Detecting anxiety and depression in general medical settings. Br Med J 1988; 297: 897-9. Mackay C, Cox T, Burrows G, Lazzerini T. An inventory for the measurement of self-reported stress and arousal. BrJSoc Clin Psychol 1978; 17: 283-4. GoldbergDP. Manualofthe General Health Questionnaire. Windsor: Nfer-Nelson, 1978. Bridges KW, Goldberg DP. The validation of the GHQ-28 and the use of the M.M.S.E. in neurological in-patients. Br J Psychiatry 1986; 148: 548-53. Goddard E, Ikin C. Drinking in England and Wales in 1987. Office Population Censuses and Surveys. London: HMSO, 1988. Collier DJ, Beales ILP. Drinking among medical students: a questionnaire survey. Br Med J 1989; 299: 19-22. Gann M, Corpe U, Wilson I. The application of a short anxiety and depression questionnaire to oil industry staff. J Soc Occup Med 1990; 40: 138-42. Cox T. The recognition and measurement of stress. In: Wilson JR, Corlett EN (eds), Evaluation of Human Work. Taylor and Francis, 1989; 628-47. Bridges KW, Goldberg DP. Psychiatric illness in patients with neurological disorder. Br Med J 1984; 289: 656-8. Bridges KW, Goldberg DP. Somatic presentation of DSM III psychiatric disorders in primary care. J Psychosom Res 29: 563-9. Goldberg DP, Kay C, Thompson L. Psychiatric morbidity in general practice and the community. Psychol Med 1976; 6: 565-9. Finlay-Jones RA, Burvill PW. The prevalence of minor psychiatric morbidity in the community. Psychol Med 1977; 7: 475-89. Duncan Jones P, Henderson S. The use of a two-phase design in a prevalence survey. Soc Psychiatry 1978; 13: 231-7. Office of Population Censuses and Surveys, General Household Survey. London: HMSO, 1988.
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and 60) have been used in occupational groups such as nurses, doctors, social workers and pharmacists9, but not factory workers. In those studies that have used the GHQ-28 the above prevalence rates compare with 39 per cent in a group of neurology inpatients18, 33 per cent in a study of patients with new illness in primary care19 and between 8 and 18 per cent in three community studies20"22. That is, psychiatric morbidity on three shifts appears to be in keeping with patients consulting doctors, whereas psychiatric morbidity in days only workers appears to be more in keeping with community studies. These findings should be treated with caution as the calculation for psychiatric morbidity is based on sensitivity and specificity values determined by other studies on different subjects. We would have liked to have validated the use of the GHQ-28 in this factory, but time restraints to interview subjects and the lack of privacy, prevented us from doing a standardized research interview such as the Present State Examination, on a sub-group of the sample. One of the conditions for management granting consent for this study to take place was that the questionnaires could only be administered in the employees' own time, which during three shifts meant in practice during one of three 15 minute breaks. Ideally subjects should have been recruited randomly from personnel records rather than haphazardly on the track, but this was not done for practical reasons. The results do suggest however that advancing three shift work is associated with more psycho-social disturbance than with day only work, and with the 'fortnight about' type of shift pattern. This observation is worthy of more vigorous study to identify aetiological factors and vulnerable groups who might benefit from additional support such as counselling. Despite the differences noted above there was no significant difference in the mean weekly total absence on three shifts compared with 'fortnight about', possibly reflecting the effects of factors unrelated to health on absence attributed to sickness. Consultation rates with general practitioners vary with age and socio-economic group 23 . The subjects in this study consulted a doctor on average once every two months, which compares with once every four months in the 1988 General Household Survey23. The reasons for the relatively high consultation rates with doctors in both shift and day workers cannot be determined by this study, but may be related to some of the disturbances in health identified in this study. The reason for the lower enjoyment of work of the day only subjects is unknown, but may be related to the older process, albeit paced and track tied, on which they were working. It is tempting to suggest that their reported lower level of tension at home was associated with them not working shifts, but the effects of other confounding variables, such as higher age and fewer married or cohabiting subjects in this group may also be relevant. Less difficulty with sleeping is well reported for day only workers, yet it is interesting to note that one third reported difficulty sleeping. In conclusion, the change to discontinuous advancing
C. J. M. Poole et ai: Changing shift work on health
197
APPENDIX: QUESTIONNAIRE [ ]M
1. Sex 2. Edinic Origin
[ ] UK & Irish
[ ] African
[ ] Caribbean
[
[ ] t 1 Asian European (Indian-subcontinent)
[ ] Other
3. Age 4. Current marital status
[ ]
Single
[ ]
Married or Cohabiting
[ ]
Separated or Divorced
[ ]
Widowed
5. Number of children at home (Please circle) 0
1 2
3
6. How many times have you consulted a doctor in the last month?
4
5
or more
[ ]
[ ]
pints of beer
[ ]
glasses of shorts/spirits
[ ]
glasses of wine
8. Have you had any tummy pain or indigestion in the last week?
[ ] YES
[ ] NO
9. Have you had any burning behind the breastbone (heartburn) in the last week?
[ ] YES
[ ] NO
10. How many times have you opened your bowels in the last 2 days?
[ ]
In the last month have you-
YES
NO
1. felt keyed up or on edge?
[ ]
[ ]
2. been worrying a lot?
[ ]
[ ]
3. been irritable?
[ ]
[ ]
4. had difficulty relaxing?
[ ]
[ ]
5. been sleeping poorly?
[ ]
[ ]
6. had headaches or neck aches?
[ ]
[ ]
sweating, frequency or diarrhoea?
[ ]
[ ]
8. been worried about your health?
[ ]
[ ]
9. had difficulty falling asleep?
[ ]
[ ]
YES
NO
1. been low in energy?
[ ]
[ ]
2. had loss of interests?
[ ]
[ ]
3. lost confidence in yourself?
[ ]
[ ]
4. felt hopeless?
[ ]
[ ]
5. had difficulty concentrating?
[ ]
[ ]
6. lost weight (due to poor appetite)?
[ ]
[ ]
7. been waking early?
[ ]
[ ]
8. felt slowed up?
[ ]
[ ]
9. tended to feel worse in the mornings?
[ ]
[ ]
(if yes to two of the above, go on to answer)
7. had any trembling, tingling, dizzy spells,
In the last month have you-
(if yes to any questions, go on to answer)
Please answer ALL the questions on the following two pages simply by underlining the answer which you think most nearly
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7. How much alcohol have you drunk in the last week, including the weekend?
198 Occup. Med. 1992, Vol. 42, No 4
applies to you. Remember that I want to know about present and recent complaints, not those that you had in the past. It is important that you try to answer ALL the questions. Over the last few weeks have you: Al. Been feeling perfectly well and in good health? A2. Been feeling in need of a good tonic?
Better than usual Not
at all A3. Been feeling run down and out of sorts?
Not
at all A4. Felt that you are ill?
Not
at all A5. Been getting any pains in your head?
Not
at all Not
Bl. Lost much sleep over worry?
Not
B2. Had difficulty in staying asleep once you are off? B3. Felt constantly under strain?
Not
Not
at all at all at all at all Not
at all B4. Been getting edgy and bad-tempered?
Not
at all B5. Been getting scared or panicky for no good reason? B6. Found everything getting on top of you?
Not
at all Not
at all B7. Been feeling nervous and strung-up all the time? Cl. Been managing to keep yourself busy and occupied? C2. Been taking longer over the things you do? C3. Felt on the whole you were doing things well ? C4. Been satisfied with the way you've carried out your task? C5. Felt that you are playing a useful part in things ? C6. Felt capable of making decisions about things? C7. Been able to enjoy your normal day-to-day activities ? D l . Been thinking of yourself as a worthless person ? D2. Felt that life is entirely hopeless?
Not
at all More so than usual Quicker than usual Better than usual More satisfied More so than usual More so than usual More so than usual Not
at all Not
at all D3. Felt that life isn't worth living? D4. Thought of the possibility that you might make away with yourself? D5. Found at times you couldn't do anything because your nerves were too bad? D6. Found yourself wishing you were dead and away from it all? D7. Found that the idea of taking your own life kept coming into your mind?
Not
at all Definitely not Not
at all Not
at all Definitely not
Worse than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather more than usual Rather less than usual Longer than usual Less well than usual Less satisfied than usual Less useful than usual Less so than usual Less so than usual Rather more than usual Rather more than usual Rather more than usual Has crossed my mind Rather more than usual Rather more than usual Has crossed my mind
Much worse than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much more than usual Much less than usual Much longer than usual Much less well Much less satisfied Much less useful Much less capable Much less than usual Much more than usual Much more than usual Much more than usual Definitely have Much more than usual Much more than usual Definitely has
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A6. Been getting a feeling of tightness or pressure in your head? A7. Been having hot or cold spells?
Same as usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual No more than usual Same as usual Same as usual About the same About same as usual Same as usual Same as usual Same as usual No more than usual No more than usual No more than usual I don't think so No more than usual No more than usual I don't think so
C. J. M. Poole et at:. Changing shift work on health
199
For each of the following words please circle the response which most applies to how you are feeling at the moment: Eg. If very tense then circle + + , if not at all tense then circle —
Answer the following questions by circling one of the numbers on a scale from 0 to 7: How would you rate your enjoyment of work? (bad)
0
1 2
3
4
(good)
4
(good)
How would you rate your social life? (bad)
0
1 2
3
How would you rate tension at home? (good)
0
1 2
3
4
(bad)
How would you rate your sex life? (bad)
0
1 2
3
4
(good)
In the last month have you: -had any difficulty going to sleep?
Yes[ ]
No[ ]
-had difficulty getting up for work?
Yes[ ]
No[ ]
-felt stressed?
Yes[ ]
No[ ]
-felt sleepy on the night shift?
Yes[ ]
No[ ]
Do you prefer to work: 3 shifts [ ]
or fortnight about [ ]
Thank you very much for your co-operation
or straight days[
or straight nights
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TIRED IDLE UPTIGHT CHEERFUL LIVELY INFURIATED CONTENTED JITTERY SLUGGISH PLEASANT SLEEPY COMFORTABLE CALM STIMULATED ACTIVATED FRIGHTENED IRRITATED ALERT HURRIED BUSY
TENSE ANGRY RESTFUL ACTIVE APPREHENSIVE WORRIED ENERGETIC DROWSY BOTHERED UNEASY DEJECTED NERVOUS BAD TEMPERED VIGOROUS PEACEFUL STEADY RELAXED DISTRESSED PUSHED PRESSED
