Effects of physical activity on sleep in an ecologically valid design

BACKGROUND: Both sleep and physical activity (PA) are essential for health. Previous studies found inconsistent effects of PA, including evening PA (EPA), on sleep. PURPOSE: To examine the effects of PA and its timing on objectively and subjectively measured sleep in predominantly healthy, young adults. METHODS: In the Budapest Sleep, Experiences and Traits Study, a highly ecologically valid multiday observational study, 267 participants tracked their natural sleep and reported PA for at least 1 week, including mobile electroencephalography recordings. We estimated the effects of PA and its timing, quantifying it as the time elapsed between activity initiation and sleep onset. RESULTS: Our findings showed no substantial main effect of PA on sleep (all P ≥ .19). However, PA temporally close to sleep had a rapid eye movement (REM) sleep-suppressing effect: each additional hour between PA and sleep onset decreased REM latency by 1.8 minutes (B = -1.82, SE = 0.58, P = .002) and increased REM percentage by 0.30 percentage points (B = 0.30, SE = 0.11, P = .008), but no other timing effect was found. Results were robust across multiple analytical specifications. CONCLUSIONS: Our results support neither a general sleep-promoting effect of PA nor a sleep-suppressing effect of EPA and suggest that for healthy young individuals, habitual, relatively low-intensity EPA is safe to perform and is a good alternative for those whose daily schedule permits no alternative timing, although the lack of detailed exercise intensity monitoring is a limitation of our study.