0273 Morning Versus Evening Exercise: Which is Better for Sleep Quality in Premenopausal Women?

Abstract

Introduction: Exercise can improve sleep. Traditional sleep hygiene recommendations discourage evening exercise, as this may disrupt sleep in some individuals. However, evening exercise training has minimal, if not beneficial, impact on sleep in healthy young adults and few studies have investigated its impact on sleep quality in women. In this study, we examined whether morning or evening exercise confers greater benefits to sleep quality in premenopausal women. Methods: Participants (women ages 18-44) were randomized to either a morning (n=25; 6:30-9:30am) or evening (n=29; 6:30-9:30pm) exercise training regimen for 8 weeks (4 days a week, 45 minutes a day, 3 days supervised). Exercise training involved moderate-intensity treadmill walking (40-59% Heart Rate Reserve). Sleep quality was assessed with Visual Analog Scale (VAS) sleep quality ratings for seven nights prior to beginning exercise training (pre-intervention) and during week eight of training (post-intervention). Twelve participants were excluded from the analyses for insufficient sleep diary data. Paired samples t-tests were performed in the total sample to explore the impact of exercise on mean level and night-to-night variability in sleep quality. Pre-post intervention difference scores in sleep variables were also computed and compared across groups (morning vs. evening training) using independent samples t-tests. Results: In the total sample, exercise improved average sleep quality and decreased night-to-night variability in sleep quality compared to baseline, t(42)=2.9, p=0.005 and t(42) =-3.2, p=0.003, respectively. The morning and evening exercise groups did not differ significantly in pre-post intervention changes in sleep quality variables. Conclusion: Regardless of time of day, exercise resulted in consistently improved sleep quality for premenopausal women. Given the sleep health benefits of exercise, sleep hygiene recommendations should encourage exercise irrespective of time of day.