A review of Swedish research on problems with irregular working hours was presented. The Swedish Work Environment Fund concluded that high priorities should be given to studies on compensation, social aspects, medical consequences, personal adjustments, and economic consequences of shiftwork (SW). Research was performed on biological rhythms, health effects, absence from work, accidents, social and leisure time activities, and the reasons as to why people start and quit SW. About 33 percent of the working population was involved in different forms of SW, nightwork, or irregular working hours. Two thirds of the SW population had irregular working hour arrangements. The most common SW pattern in Sweden was about 1 week on each different shifts with a trend toward systems with shorter cycles. A degree of adjustment was observed toward the end of the week on a particular shift. People with inclination to more evening activities were found more often among shift workers. The age of 45 appeared to be a critical age in etiology of dysfunctions. Shift workers reported more sleep and stomach disorders and experienced more fatigue, irritation, and aggression than dayworkers. Two/shift workers had higher sickness rates, while results for three/shift workers varied. Three/shift workers considered themselves more exposed to accidents than dayworkers. Results of research on irregular working hours showed that shift workers had more physical, psychical and social problems and symptoms than dayworkers. Shiftworkers had more sickday absences, suffered more social inconveniences, and had less time for their children, leisure, and social activities. Problems were caused, to a large extent, by mismatch between work hours and circadian rhythms.
The Twenty-Four Hour Workday: Proceedings of a Symposium on Variations in Work-Sleep Schedules, Division of Biomedical and Behavioral Science, NIOSH, U.S. Department of Health and Human Services, Cincinnati, Ohio, DHHS (NIOSH) Publication No. 81-127