[Prospective associations of rest-activity rhythms and obesity and adiposity-related measures in children]

Objective: To explore the prospective associations between rest-activity rhythms (RARs) with obesity and adiposity-related indicators in children. Methods: In April 2023, children in grades 3 to 4 were enrolled from two schools in Chuzhou city, Anhui Province, using cluster random sampling. At baseline, triaxial accelerometers were used to monitor physical activity and sleep continuously for 7 consecutive days. Using R studio software, non-parametric indices(relative amplitude, inter-daily stability, intra-daily variability, average activity during the most active 10 h and least active 5 h, and their midpoints) were calculated. Parametric indices (amplitude, 24 h periodic mean activity, and acrophase) were also derived. At baseline and during the 1.5-year follow-up (October 2024), body fat-related indices, including percent body fat (PBF), fat mass (FM), and visceral fat area (VFA), were measured using a bioelectrical impedance analyzer. Linear mixed-effects models were employed to analyze the associations between RARs and obesity and body fat-related indices. Results: The final analysis included 534 children with a median (Q₁, Q₃) age of 9.72 (9.17, 10.20) years at baseline; 265 (48.18%) were girls. Relative amplitude and amplitude were associated with reductions in PBF (β=-0.87, 95%CI: -0.53 - -0.20; β=-1.23, 95%CI: -1.89 - -0.56), FM (β=-0.49, 95%CI: -0.89 - -0.08; β=-0.70, 95%CI: -1.10 - -0.30), and VFA (β=-2.70, 95%CI: -4.83 - -0.58; β=-3.66, 95%CI: -5.78 - -1.55) at follow-up (all P values <0.05). Amplitude was associated with reductions in BMI (β=-0.28, 95%CI: -0.51 - -0.05) and waist circumference (β=-0.87, 95%CI: -1.33 - -0.40)(both P<0.05). Conclusions: Robust circadian rhythms, characterized by higher daytime activity and stable nighttime sleep, are protective factors for obesity and adiposity-related indicators in children, suggesting that fostering regular rest-activity patterns helps prevent childhood obesity.