Does nighttime exercise really disturb sleep? Results from the 2013 National Sleep Foundation Sleep in America Poll

Objective: To assess the relationship between sleep, time of exercise, and intensity of exercise in a large American sample. Methods: The 2013 National Sleep Foundation Sleep in America Poll was a cross-sectional study of 1000 adults stratified by age (23-60. years) and US geographical region. Sleep outcomes included self-reported sleep quality, total sleep time, sleep latency, and waking unrefreshed. Exercise timing was characterized as morning (>8. h before bed), afternoon (4-8. h before bed), or evening (<4. h before bed). Exercise intensity was assessed with a modified version of the International Physical Activity Questionnaire. Results: After adjustment for confounders, evening moderate or vigorous exercisers did not differ in any of the reported sleep metrics compared to non-exercisers. Morning vigorous exercisers had the most favorable sleep outcomes, including greater likelihood of reporting good sleep quality (OR. = 1.88, p<. .001) and lower likelihood of waking unrefreshed (OR. = 0.56, p= .03). Most individuals who performed vigorous evening exercise believed that their sleep was of equal or better quality (97%) and duration (98%) on days they exercised. Conclusion: Evening exercise was not associated with worse sleep. These findings add to the growing body of evidence that sleep hygiene recommendations should not discourage evening exercise.