0919 Impact of Circadian Misalignment on the Association of Sedentarism with Weight Gain from Childhood to Adolescence

Abstract Introduction Adolescence is a developmental period marked by significant changes in sleep, particularly in circadian timing. This transition is also characterized by declines in physical activity (PA) and increases in sedentary behavior (SB), which, combined with sleep changes, may exacerbate weight gain and obesity. However, few longitudinal studies have examined how sleep timing modifies the impact of PA/SB on weight gain in the transition from childhood to adolescence. Methods We studied 307 subjects from the Penn State Child Cohort aged 5-12 years old at the childhood visit and 12-19 years old at the adolescent visit (53% male, 23% racial/ethnic minority) who underwent in-lab polysomnography and had at least 3 valid actigraphy (ACT) nights. Predictors included ACT-measured SB and moderate-to-vigorous PA (MVPA). Moderators included ACT-measured sleep duration, variability, midpoint, and irregularity. Outcomes were change in body mass index (ΔBMI) and in waist circumference (ΔWC) from childhood to adolescence. Stepwise linear regressions adjusted for age, sex, race/ethnicity, socioeconomic status, being on school breaks, apnea/hypopnea index, insomnia symptoms, internalizing symptoms, and externalizing behaviors as well as height and childhood baseline values, as required. Results Sleep irregularity (p-interaction = 0.014) and, to a lesser extent sleep midpoint (p-interaction = 0.09), modified the association between SB with ΔWC. Similar, but weaker findings, were observed with ΔBMI (e.g., sleep irregularity p-interaction = 0.059). Among adolescents with highest sleep irregularity (≥2 hours), greater SB was associated with a larger increase in ΔWC since childhood (Est=9.28, SE=3.59, p=0.01). No significant effect modification was found for sleep duration or variability or for the association between MVPA and weight gain. Conclusion This study is among the first to evaluate longitudinal synergistic effects of sedentarism on weight gain by sleep irregularity. The impact of sedentarism on weight gain is stronger in adolescents with misalignment in the circadian timing of sleep. Implementing interventions that target circadian sleep timing, combined with strategies to increase physical activity, may help to reduce weigh gain and prevent central obesity in the transition from childhood to adolescence. Support (if any) R01HL136587