Timing of Device-Measured Physical Activity and Sleep in Relation to Meeting Physical Activity Guidelines in U.S. Adults

Introduction: Whether the timing of moderate-to-vigorous physical activity (MVPA) and sleep is independently and jointly associated with meeting physical activity guidelines in adults remains unclear. Methods: We cross-sectionally analyzed 2003–2006 National Health and Nutrition Examination Survey (NHANES) data. Non-pregnant adults aged ≥20 years with valid accelerometer data, ≥5 min/day of MVPA, and no mobility limitation were included (n=3,153). Participants were classified as: morning (06:00–09:59), midday (10:00–13:59), afternoon (14:00–17:59), evening (18:00–21:59), or overnight (22:00–05:59) MVPA groups if ≥50% of average daily MVPA occurred in that window; or as mixed if otherwise. Subsamples with valid sleep timing proxy data (n=2,370) were classified as: irregular sleepers if participants had a standard deviation of the sleep midpoint >1 h; otherwise, regular sleepers were further categorized by mean sleep midpoint as early (22:00–01:59), mid (02:00–03:59), or late (04:00–07:59). Survey-weighted modified Poisson models were used to estimate adjusted prevalence ratios (PRs) and 95% confidence intervals (CIs) for meeting PA guidelines (i.e., ≥150 min/week of moderate-equivalent activity), controlling for sociodemographic, behavioral, and health-related covariates. Results: Morning MVPA (PR = 1.48, 95% CI = 1.31–1.66) and early sleep (1.14, 1.01–1.28) were each associated with a higher prevalence of meeting PA guidelines compared to mixed MVPA and irregular sleep, respectively. Similar patterns were observed for joint groups of morning MVPA with early sleep (1.57, 1.14–2.16), morning MVPA with mid sleep (1.62, 1.34–1.96), and midday MVPA with mid sleep (1.44, 1.21–1.73) compared with mixed MVPA with irregular sleep. Conclusions: Accumulating MVPA predominantly in the morning and/or maintaining earlier sleep timing may inform timing-based strategies to support population-level adherence to PA guidelines.