Bidirectional Daily Associations Between Accelerometer-Measured Sleep and Physical Activity in Brazilian High School Students

Purpose: This study analyzed day-to-day estimates of bidirectional associations between sleep parameters and intensity-specific physical activity and assessed whether the timing of physical activity influences these relationships. Methods: The sample was comprised of 651 high school students (51.2% female, 16.33 [1.0] y old) from southern Brazil. Physical activity and sleep were measured using accelerometers. Multilevel models were applied to test associations of nocturnal total sleep time, onset, and efficiency with moderate to vigorous and light (LPA) physical activity. Results: Higher engagement in moderate to vigorous physical activity and LPA was associated with increased total sleep time, and this effect was greater when physical activity was performed in the morning. Morning and evening LPA were associated with increased sleep efficiency and reduced total sleep time, respectively. Practice of LPA in the morning leads to early sleep onset, whereas evening LPA was associated with later onset. Higher total sleep time and later sleep onset were associated with lower moderate to vigorous physical activity and LPA on the following day. However, higher sleep efficiency was associated with increased LPA. Conclusion: The relationship between sleep parameters and physical activity is bidirectional and dependent on physical activity intensity and timing.