The effect of the total amount of work hours and the benefits of a shortening is frequently debated, but very little data is available. The present study compared a group (N = 41) that obtained a 9 h reduction of the working week (to a 6 h day) with a comparison group (N = 22) that retained normal work hours. Both groups were constituted of mainly female health care and day care nursery personnel. The experimental group retained full pay and extra personnel were employed to compensate for loss of hours. Questionnaire data were obtained before and 1 year after the change. The data were analyzed using a two-factor ANOVA with the interaction term year*group as the main focus. The results showed a significant interaction of year*group for social factors, sleep quality, mental fatigue, and heart/respiratory complaints, and attitude to work hours. In all cases the experimental group improved whereas the control group did not change. It was concluded that shortened work hours have clear social effects and moderate effects on well-being.
Day sleep (after night work) and night sleep (after day work) were studied in two groups of locomotive engineers aged 25-35 and 50-60 a, respectively. All recordings were made in the homes of the subjects. For both groups day sleep was reduced by approximately 3.3 h, mainly affecting rapid eye movement sleep and stage 2 sleep. Diuresis and the excretion of noradrenaline were increased during day sleep. The ratings of sleepiness were higher after night work than after day work. Several indices of disturbed daytime sleep correlated significantly with catecholamine excretion. The age groups differed mainly in that the older subjects had relatively more stage shifts, awakenings, stage 1 sleep, a higher diuresis, and a higher noradrenaline excretion during day sleep. It was concluded that night work is detrimental to sleep and that negative effects are exacerbated by increasing age.
OBJECTIVES: The present study sought to evaluate the effect of a change from a rotating 3-shift (8-hour) to a 2-shift shift (12 hour) schedule on sleep, sleepiness, performance, perceived health, and well-being. METHODS: Thirty-two shift workers at a chemical plant (control room operators) responded to a questionnaire a few months before a change was made in their shift schedule and 10 months after the change. Fourteen workers also filled out a diary, carried activity loggers, and carried out reaction-time tests (beginning and end of shift). Fourteen day workers served as a reference group for the questionnaires and 9 were intensively studied during a week with workdays and a free weekend. RESULTS: The questionnaire data showed that the shift change increased satisfaction with workhours, sleep, and time for social activities. Health, perceived accident risk, and reaction-time performance were not negatively affected. Alertness improved and subjective recovery time after night work decreased. The quick changes in the 8-hour schedule greatly increased sleep problems and fatigue. Sleepiness integrated across the entire shift cycle showed that the shift workers were less alert than the day workers, across workdays and days off (although alertness increased with the 12-hour shift). CONCLUSIONS: The change from 8-hour to 12-hour shifts was positive in most respects, possibly due to the shorter sequences of the workdays, the longer sequences of consecutive days off, the fewer types of shifts (easier planning), and the elimination of quick changes. The results may differ in groups with a higher work load.
A sample of 73 men and women aged 22-63 years and working in six different occupations (air traffic controllers, waiters, physicians, symphony orchestra musicians, baggage handlers, and airplane mechanics) participated in a longitudinal study four times during a year. The spontaneous variations in job strain (determined as the self-reported ratio between psychological demands and decision latitude) were substantial. The average difference between the occasion with the highest level of strain and the occasion with the lowest level was 25% of the total mean. Systolic blood pressure during workhours, as well as self-reported sleep disturbance, increased when demands increased in relation to decision latitude. Among men with a depressive tendency (according to a diary) morning plasma prolactin levels increased markedly with increasing job strain. Among subjects with a positive family history of hypertension the increase in systolic blood pressure at work was particularly pronounced, and among the men in this group a lower than expected level of morning cortisol was found measured during the period with the highest level of strain.
The aim of the present study was to compare 12-hour shifts during weekends with 8-hour shifts during weekdays with respect to sleep, sleepiness, physical effort, and performance.
Thirty-one subjects at a power plant participated. Sleep, sleepiness, and physical effort were measured with a diary. About half of the subjects carried out a reaction-time test during both 8- and 12-hour morning and night shifts. The remaining subjects carried out a vigilance task.
Sleepiness was higher and physical effort lower on the 12-hour night shift than on the 8-hour night shift. However, the subjects who had the same level of physical effort on 8- and 12-hour night shifts did not differ with respect to sleepiness. During the 12-hour morning shift, sleepiness was lower and the sleep length was longer than on the 8-h morning shift. The subjects who had the same amount of sleep for 8- and 12-hour morning shifts showed no difference in sleepiness. Sleep did not differ between 8- and 12-hour night shifts. There was no difference between 8- and 12-hour shifts with respect to performance.
It was suggested that the difference in sleepiness between 8- and 12-hour shifts is related to differences in sleep length for the morning shift, and to differences in physical effort for the night shift, rather than to shift duration. Thus the most likely conclusion is that 12-hour shifts do not cause increased sleepiness or impaired performance or disturbed sleep.
The aim of the present study was to investigate how "double-shifts" (15.5 hours) affects sleep, fatigue and self-rated health. The study was carried out on male construction workers of which 80% were long-distance commuters. The schedule involved two work periods and each work period involved two double shifts in a row. The subjects filled in a sleep/wake diary at 8 times across a year and a questionnaire at 3 times. They also wore an actigraph during one shift cycle. The results showed that sleepiness, and to a certain extent, mental fatigue increased during double shifts and accumulated across days. The short rest time (8.5 hours) between days caused insufficient sleep and approximately 5.5 hours of sleep was obtained between double shifts. Questionnaire data showed that complaints of insufficient sleep, exhaustion on awakening and pain symptoms increased across the year. It was concluded that a shift system involving double shifts has a negative effect on fatigue, recovery and health-related well-being.
We compared the effects of different types of free-time activity on subjective and objective indices of sleep, recovery and well-being in an experimental field study. Twelve participants spent four consecutive evenings after work in each of three conditions: pursuing quiet leisure activities at home; undertaking active leisure pursuits; doing additional work. Ratings of rest and recuperation, and of satisfaction, were lowest in the additional work condition. There were few other differences between conditions. However, being satisfied with one's evening activities (regardless of which experimental condition was being undertaken) was associated with improved subsequent sleep (self-reported). Evening activities involving lower mental effort were also associated with better-rated sleep, as well as improved recuperation and fatigue the next day. It is concluded that the nature of activity per se may be less important than (1) whether the activity accords with individual preference and (2) the cumulative demands of daytime and evening activities.
504 papermill workers were followed up for 15 years and the incidence of ischaemic heart disease (IHD) in shift workers was compared with that in day workers. The relative risk (RR) of IHD rose with increasing duration of reported exposure to shift work. A significant risk of IHD was associated with an exposure of 11 - 15 years (RR = 2.2, p less than 0.04) and of 16 to 20 years (RR = 2.8, p less than 0.03. The association was independent of age and smoking history. The RR of IHD fell sharply after 20 years of shift work. This was ascribed to the pronounced positive selection that had taken place in this group.
Recently there has been a sizeable increase in research on fatigue and accidents in transportation. Therefore a meeting was convened last year to discuss prevalence, mechanisms and countermeasures, with the intention to produce an international consensus document. It was concluded that official statistics strongly underestimate prevalence, and that a reasonable estimate, based on research, lies between 10 and 20% for accidents on the road, in the air and at sea. The main causes are disturbed sleep and work at the circadian low, caused by night work, morning work, sleep/wake disorders (including sleep apnea) or social obstacles to sleep. Suggested countermeasures include information/education of the public and of transportation companies, as well as enforcement of existing work hour regulation. Additional countermeasures include strategic use of napping and caffeine, as well as implementation of rumble strips and--possibly--electronic devices for drowsiness detection.