Sleep, 24-hour activity rhythms, and cardiometabolic risk factors in school-age children.

STUDY OBJECTIVES: Disturbed sleep and 24-hour activity rhythms are linked to adverse cardiometabolic profiles in adults and adolescents, and these associations may originate in early life. We aimed to study associations of sleep and 24-hour rhythms with cardiometabolic risk factors in school-age children.

METHODS: This cross-sectional population-based study comprised 894 children aged 8-11 years from the Generation R Study. Sleep (duration, efficiency, number of awakenings, time awake after sleep onset) and 24-hour activity rhythms (social jetlag, interdaily stability, intradaily variability) were assessed using tri-axial wrist actigraphy for nine consecutive nights. Cardiometabolic risk factors included adiposity (body mass index Z-score, fat mass index using dual-energy-X-ray-absorptiometry, visceral fat mass and liver fat fraction using magnetic resonance imaging), blood pressure and blood markers (glucose, insulin, lipids). We adjusted for season, age, sociodemographics and lifestyle factors.

RESULTS: Each increase in interquartile range (IQR) of nightly awakenings (2 times) was associated with -0.12 SD (95% CI -0.21;-0.04) lower body mass index and 0.15 mmol/L (0.10;0.21) higher glucose. Among boys, an increase in IQR of intradaily variability (0.12) was associated with higher fat mass index (+0.07 kg/m2 , 95% CI 0.03;0.11) and visceral FM (+0.08 gr, 0.02;0.15). We observed no associations with blood pressure or clustering of cardiometabolic risk factors.

CONCLUSIONS: Already at school-age, greater fragmentation of the 24-hour activity rhythm is associated with general and organ adiposity. In contrast, more nightly awakenings were associated with lower BMI. Future research should bring clarity to these disparate observations in order to create potential targets for obesity prevention programs.