OBJECTIVESTo explore the association of sleep duration with obesity among children in urban areas of China.

METHODSA total of 6 576 children (3 293 boys and 3 283 girls) aged 7-11 years were randomly selected from 36 primary schools in 6 metropolitan cities in China. A 7-day Physical Activity Recall was used to assess the sleep duration and physical activity level. The height, weight, waist circumference (WC) and percentage of body fat (%BF, as determined by bioelectrical impedance analysis technique) were measured by following the standardized operation procedures. The information on demography, lifestyle and eating habits was collected with a self-administered questionnaire from participants and their parents.

RESULTSThe average sleep duration per night in the children was 9.7 h with the decreasing trends along with the increase of age (P < 0.05). The sleep duration was negatively associated with body mass index (BMI) and WC in both boys and girls after adjustment for confounders (beta value -0.23 and -0.82 for boys, -0.24 and -0.91 for girls, respectively, P < 0.01). However, no significant association of sleep duration with %BF was found. Children who slept less than 9.0 h per night had a higher risk for overweight and obesity (OR = 1.29, 95% CI: 1.01, 1.64) and abdominal obesity (OR=1.38, 95% CI: 1.04, 1.83) as compared with those who slept for 10.0-10.9 h.

CONCLUSIONSShort sleep duration is associated with obesity. It is important to ensure adequate sleep duration of children and foster their healthy lifestyle at an early stage of life.