Epidemiology of exercise and sleep.

Although exercise is widely believed to improve sleep, experimental evidence has found acute and chronic exercise to exert only modest effects on subsequent sleep. However, these studies are limited in that they have primarily used good sleepers (floor/ceiling effects). In contrast to experimental studies, epidemiologic studies have consistently reported significant positive associations between self-reported exercise habits and better self-reported sleep. This association has been confirmed across a wide range of demographics. Nonetheless, epidemiologic studies on this topic have also had limitations. They have often assessed exercise and sleep using instruments of dubious validity. Moreover, the studies have generally not included clinical diagnoses of sleep disorders. Thus, the clinical relevance of these findings is unclear. In addition, possible alternative explanations for the association of exercise and improved sleep have often not been controlled (e.g. bright light, other healthy behaviors). This review will focus on these epidemiologic studies. We will review and critique representative survey and epidemiologic studies of exercise and sleep and discuss directions for future research in this area.