[The associations between nighttime sleep duration, bedtime and preschool children's obesity].

To examine the relationship of nighttime sleep duration and bedtime with preschool children's obesity, and to explore possible early life risk factors for childhood obesity. A total of 14 946 valid children from 16 439 pre-school children aged 3-6 years in 91 kindergartens in Ma'anshan city participated in the study. The body mass index cut-offs for overweight and obesity in Chinese children and adolescents aged 2-18 years was used as the criterion for judging overweight and obesity, and pathological and secondary causes of obesity were excluded. The associations of nighttime sleep duration and bedtime with preschool children's obesity was analyzed by using non-conditional multivariate binary logistic regression model. Among the preschool children, 22.4% (3 345) had shorter sleep duration. 9.5% (1 415) had bedtimes after 22:00 on weekdays and 21.8% (3 260) had bedtimes after 22:00 on weekends. The prevalence of overweight and obesity were 16.5% (2 466) and 10.5% (1 562), respectively. After the adjustent of age, gender, whether or not only child, residence in the last six months, parents' body mass index parents' educational level, diet preference, outdoor activities, TV viewing duration, sleep duration, bedtime on weekdays and weekends, only the shorter sleep duration (1.25, 95: 1.03-1.51) was still positively associated with the prevalence of obesity in preschool children. Shorter sleep duration was positively associated with the prevalence of obesity among preschool children.