COMBINED EFFECTS OF SHIFT WORK AND LIFE-STYLE ON THE PREVALENCE OF INSOMNIA, SLEEP-DEPRIVATION AND DAYTIME SLEEPINESS

Objectives The combined effects of age, leisure-time physical activity , smoking, alcohol consumption, and different forms of shift work on t he prevalence of sleep complaints and daytime sleepiness were studied among workers in industry, transport, and traffic. Methods Altogether 3020 subjects were studied using a psychosocial questionnaire. The par ticipants were currently employed men, aged 45-60 years, from a postal and telecommunication agency, the railway company, and 5 industrial c ompanies. On the basis of a factor analysis of an 11-item sleep questi onnaire, the sleep complaints were grouped into the categories of inso mnia, sleep deprivation, daytime sleepiness, and snoring. The importan ce of the shift schedule, age, and life-style factors as simultaneous predictors of the complaints was studied in a logistic regression anal ysis and an analysis of covariance. Results The prevalence of insomnia , sleep deprivation, and daytime sleepiness depended significantly on the shift system. All sleep complaints were more common in 2- and 3-sh ift work and in irregular shift work than in day work. The prevalence of daytime sleepiness was 20-37%, depending on the shift system. Leisu re-time physical activity and alcohol consumption were the most import ant life-style factors predicting all sleep complaints, except snoring . The effects of physical activity and alcohol consumption differed fo r different shift schedules. Conclusions Different shift systems, also 2-shift work and permanent night work, seem to increase the frequency of sleep complaints. Especially 3-shift work seems to interact with l ife-style factors by increasing the adverse effects and decreasing the beneficial effects on sleep and sleepiness.