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. (C) 2014 Elsevier B.V. All rights reserved.