Associations between adherence to 24-hour movement guidelines and parameters of the rest-activity rhythm among preschool-aged children: An exploratory analysis.

This exploratory cross-sectional secondary analysis examined associations between 24-hour movement behaviors and rest-activity rhythm (RAR) among preschoolers using baseline data from 84 children aged 3.0-5.9 years in a randomized controlled trial. Accelerometer data were processed using R package GGIR to derive time-use composition and cut-point-free metrics (average acceleration and intensity gradient). RAR was characterized by relative amplitude (RA), inter-daily stability (IS), intra‑daily variability (IV), and the circadian function index (CFI). In generalized linear models adjusted for age, sex, body mass index z-score, parental education level, and the number of valid accelerometer wear days, with false discovery rate (FDR) correction, more sedentary behavior relative to other behaviors was associated with lower IS (β =  -0.185; 95% confidence interval [CI]: -0.281, -0.089), higher IV (β = 0.249; 95% CI: 0.117, 0.380), and lower CFI (β =  -0.252; 95% CI: -0.338, -0.166). In contrast, more light-intensity physical activity was associated with lower IV (β =  -0.324; 95% CI: -0.547, -0.100), and higher CFI (β = 0.239; 95% CI: 0.111, 0.368). Higher average acceleration was associated with higher CFI (β = 0.005; 95% CI: 0.002, 0.008). These preliminary findings suggest that higher relative light‑intensity physical activity and lower relative sedentary behavior were associated with healthier RAR in preschoolers. These potential associations warrant further investigation in future confirmatory studies.