Prevalence of adiposity and its association with sleep duration, quality and timing among 9-to-12 years old children in China, Guangzhou

Abstract Background Short sleep duration has been reported to be associated with obesity in children, but findings are not consistent. Since few studies have examined the relationship between more complex sleep characteristics and obesity, we examined the association between adiposity and self-reported sleep duration, bedtime and sleep quality in 9-to-12 years old Chinese children using multilevel mixed models. Methods 5518 children aged 9-12 years were recruited from 29 randomly selected primary schools in Guangzhou, China in 2014. Standardised questionnaires were used to obtain data to estimate sleep duration on typical weekday and weekends. Sleep quality data were collected using the Children’s Sleep Habits Questionnaire (CSHQ). Trained researchers undertook measurements of weight, height and waist circumference (WC) for all participating children. Body mass index (BMI) z-scores were derived using the World Health Organization (WHO) child growth reference, and children were classified as overweight or obese using +1 and+2SD as cut-offs respectively. Percentage body fat (BF%) was calculated using bioelectrical impedance. ResultsLonger sleep duration was inversely associated with BMI z-score (β = -0.16, p<0.05), WC (β = -1.11, p<0.05) and later bedtime was associated with higher BMI-z score (β = 0.03, p<0.05), WC (β = 1.72, p<0.001), and BF% (β = 0.15, p<0.05) in multivariable multilevel mixed models after adjustment for age, gender, physical activity, parental education level and average monthly income. No association was seen between sleep quality and adiposity. ConclusionShorter sleep duration and later bedtime are associated with higher adiposity indices in early adolescents from south China.Key words: sleep duration, sleep quality, bedtime, adiposity, children;