Timing of Daily Device-Assessed Physical Activity and Nightly Sleep Quality Across Pregnancy

Background: Moderate-to-vigorous-intensity physical activity (MVPA) timing may influence sleep in pregnancy. We aimed to examine the associations of daily total duration and timing of MVPA with sleep quality during pregnancy. Methods: Nine participants ( N days = 928) at Kaiser Permanente Northern California enrolled in early pregnancy and wore an accelerometer 24/7, up to 35 wk gestation. Algorithms classified device minutes as wear/nonwear, bedrest (proxy for sleep)/active, and by movement intensity. Windows (morning = 5:00 am –11:00 am , midday = 11:00 am –5:00 pm , evening = 5:00 pm –00:00 am ) with ≥50% of the day’s MVPA were classified as “dominant.” Days with <50% of MVPA in one window were considered “mixed.” Mixed-effects models estimated associations of daily MVPA duration and timing (evening-dominant reference) with measures of device-based bedrest (multidimensional bedrest score, duration, efficiency, number of bedrest interruptions, average length of bedrest interruptions, and bedrest midpoint) and self-reported sleep (sleep efficiency, sleep latency, and perceived sleep quality), stratified by trimester. Results: MVPA duration was associated with small, trimester-specific changes in sleep timing and efficiency. In the first trimester, sleep latency was 8.13 min shorter on midday-dominant versus reference (95% confidence interval (CI): −15.79 to −0.46). In the second trimester, multidimensional bedrest score was 0.12 points greater (95% CI: 0.01–0.23), bedrest duration 0.44 h longer (95% CI: 0.16–0.73), length of bedrest interruptions 5.58 min shorter (95% CI: −9.91 to −1.25), and diary-based sleep efficiency 4.54% greater (95% CI: 0.70–8.37) on midday-dominant versus reference. In the third trimester, bedrest midpoint was 0.85 min shorter on midday-dominant versus reference (95% CI: −1.1 to −0.55). MVPA timing was not associated with perceived sleep quality or bedrest efficiency. Conclusions: Midday-dominant MVPA was associated with better sleep quality compared with evening-dominant MVPA in pregnancy. Associations with specific bedrest and sleep outcomes varied by trimester. Future directions include investigating joint associations of intensity, duration, type, and timing of physical activity on sleep measures in large, diverse cohorts.