Dynamics of Sleep, Sedentary Behavior and MVPA on School versus Non-School Days.

STUDY OBJECTIVES Studies examining time-use activity behaviors (sleep, sedentary behavior and physical activity) on school days compared to non-school days have examined these behaviors independently, ignoring their interrelated nature, limiting our ability to optimize the health benefits of these behaviors. This study examines the associations of school-day (versus non-school day) with time-use activity behaviors. METHODS Time series data (6,642 days) from Fitbits (Charge-2) were collected (n=196, 53% female, 5-10yrs). We used a variable-centered dynamic structural equation modeling (DSEM) approach to estimate day-to-day associations of time-use activity behaviors on school days for each child. We then used person-centered cluster analyses to group individuals based on these estimates. RESULTS Within-participant analysis showed that on school days (vs. non-school days), children (1) slept less (β=-0.17, 95%CI=-0.21, -0.13), (2) were less sedentary (β=-0.05, 95%CI=-0.09, -0.02), and (3) had comparable MVPA (β=-0.05, 95%CI=-0.11, 0.00). Between-participant analysis showed that, on school days, children with higher sleep carryover experienced greater decreases in sleep (β=0.44 95%CI=0.08, 0.71), children with higher zBMI decreased sedentary behavior more (β=-0.41, 95%CI=-0.64, -0.13), and children with lower MVPA increased MVPA more (β=-0.41, 95%CI -0.64, -0.13). Cluster analysis demonstrated four distinct patterns of connections between time-use activity behaviors and school (High Activity, Sleep Resilient, High Sedentary and Dysregulated Sleep). CONCLUSIONS Using a combination of person-centered and more traditional variable-centered approaches, we identified patterns of interrelated behaviors that differed on school, and non-school days. Findings can inform targeted intervention strategies tailored to children's specific behavior patterns.