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.