Abstract
<title>Abstract</title> <p> <bold>Background/Objectives</bold> Circadian light exposure may influence central adiposity in children. We examined whether objectively measured 24-hour light exposure patterns, particularly blue light exposure (BLE), were associated with waist-to-height ratio (WtHR) in school-aged children. <bold>Subjects/Methods</bold> This cross-sectional school-based study included 91 children aged 7 to 15 years, 48 girls, observed simultaneously during the same school week in May 2025 in Tyumen, thereby standardizing ambient light conditions across participants. Six participants were excluded because of poor actigraphy quality due to large non-wear episodes, leaving 85 children for analysis. Participants wore wrist actigraphy devices with integrated RGB light sensors for 7 days to assess sleep, physical activity, wrist temperature, and light/BLE exposure. The sample size was determined by the precision required for this exploratory analysis. <bold>Results</bold> Higher WtHR was associated with shorter sleep duration and was most strongly related to BLE patterns. In multivariable models, nocturnal BLE independently predicted WtHR (β = 0.311, P = 0.011), as did reduced 24-hour BLE robustness (β = 0.425, P = 0.001) and greater day-to-day variability in BLE (β = 0.449, P < 0.001). Children with WtHR > 0.5 showed reduced morning and elevated afternoon and nocturnal light exposure and had nearly five-fold higher odds of detectable nocturnal BLE exposure (OR, 4.98; 95% CI, 1.06–23.28; P = 0.018). Physical activity and wrist temperature rhythms showed little association with WtHR. <bold>Conclusions</bold> In school-aged children, circadian light exposure, particularly nighttime BLE, was more strongly associated with central adiposity than physical activity, sleep duration, or wrist temperature rhythms. These findings identify light timing and regularity as potentially modifiable correlates of pediatric adiposity. </p>