0144 Exercise Timing and Sleep in Young Adults

Abstract

Introduction: Sufficient sleep and regular exercise are important for optimal health. Although exercise is associated with enhanced sleep quality; there is evidence that exercise performed in the evening can have an adverse impact on subsequent sleep. Unfortunately, many individuals with busy schedules are only able to make time to exercise in the evening. Therefore, it is important to understand the relationship between exercise timing and sleep. In addition, an individual's chronotype (preference for activity in the morning or evening) may play an important role in this relationship. We examined exercise timing, chronotype and sleep in a diverse population of young adults. Methods: Data were analyzed from N=867 enrolled in a cross-sectional study of undergraduates (19.5±1.4y, 38% female, 38% white). Participants were recruited after completing a workout at on-campus fitness facilities during operational hours (7 AM to 11 PM, approximately 55 participants were recruited per hour) and completed the Reduced Chronotype and Pittsburgh Sleep Quality Index (PSQI) questionnaires. Multiple regression and analysis of variance were used to examine the relationship between exercise timing, chronotype and sleep. Results: In this sample of undergraduates, average self-reported sleep duration=6.9±1.2 h/night, bedtime=12:45 AM ± 77 min, and global PSQI score=6.0 ± 2.8. Approximately 58% were neither morning/evening type, 13% were moderately/definitely morning type and 29% were moderately/definitely evening type. Timing of exercise was not associated with sleep duration or global PSQI score but was associated with bedtime, and the PSQI perceived sleep quality and sleep efficiency subscales (ps<0.05). Participants who exercised in the evening (6-11 PM) went to bed later and reported poorer sleep quality and lower sleep efficiency than those who exercised in the morning (7 AM-noon) or afternoon (noon-6 PM) (ps<0.05). Participants with an evening preference exhibited a poorer global PSQI score than those with a morning preference and this was consistent among morning and evening exercisers (ps<0.05). Conclusion: Findings suggest that exercise timing and chronotype are important predictors of sleep timing and quality in undergraduates and support current sleep hygiene recommendations to not perform intensive exercise within 3 hours of bedtime.