Epidemiology of exercise effects on sleep.

This survey was designed to study the characteristics of sleep and perceived factors promoting and disturbing sleep. Several living habits, such as exercise, and characteristics of sleep were investigated independently of each other by a pretested questionnaire and a sleep diary which were mailed to a stratified random sample of 200 men and women in each of the age groups 36, 41, 46 and 50 years (N = 1600). The response rate was 75%. Every third respondent felt that exercise (e.g. jogging and evening walks) had a positive impact on sleep quality. The most frequently perceived positive effects of exercise were ease of falling asleep, deepness of sleep, a sense of wellbeing and more alertness in the morning. Negative perceived effects of exercise were uncommon. The balance of positive and negative perceived effects of exercise was more favourable when the activity was performed early in the evening compared to late at night. When both the intensity and the timing of exercise were considered, light and moderate exercise, especially early in the evening, had mainly positive effects on sleep. The frequency of negative impacts increased when the exercise was performed vigorously late at night. However, a considerable portion of vigorous late exercisers reported mainly positive effects. The available information suggests that especially light and moderate exercise early in the evening should be emphasised in health education as a means to enhance sleep and to improve its quality. However, the epidemiological information about exercise and sleep should be investigated and verified in detail using objective methods and controlled interventions.