Associations of sleep duration with childhood obesity: findings from a national cohort study in China

Objective: Examine effect of sleep duration on children's risk of overweight and obesity; and study associations between activities in the last hour before bedtime and sleep outcomes (sleep duration, sleep quality, and sleep onset latency). Methods: Children's data were recruited using a questionnaire survey from a nationally representative sample of children (n = 10 279) in China in 2013‒2016. Mixed-effects models were used to test associations among variables stratified by sex. Results: Sleep duration was positively associated with BMI in boys (β = 0.04, P = 0.021). Girls with short sleep durations (< 8 h/d) tended to have higher BMI values than those with normal sleep durations (8‒9 h/d) (β = 0.12, P = 0.063). The top three activities were playing electronic devices (Factor 1), doing homework, and reading (combined as Factor 2). Factors 1 and 2 were both significantly associated with sleep duration (β = 0.17, P < 0.001; β = −0.26, P < 0.001, respectively). Conclusion: Sleep duration seems to affect BMI in Chinese children. Using electronic devices and reading before bedtime influenced sleep duration. Good bedtime habits and sleep duration can help weight management in children.