[Associations between overweight-obesity and puberty timing in children with different genders in China].

Objective To understand the associations between overweight-obesity and puberty timing in children with different genders. Methods The girls in grade 2, 3, 7, 8 and boys in grade 3, 4, 7, 8 were recruited from primary and middle schools in North new area of Shenyang, Yanqing district of Beijing, Erqi district of Zhengzhou and Jiulongpo district of Chongqing by purposive sampling method between October and December 2014, respectively. The information of demographic characteristics of the respondents were collected and the pubertal development status was evaluated by Pubertal Development Scale (PDS). A total of 6 701 students were recruited; 6 137 out of which were valid with complete questionnaires. The associations between overweight-obesity and puberty timing were estimated by multivariate logistic regression analysis. Results The prevalence of overweight-obesity in primary schools were 34.8% (522/1 499) among boys and 24.2% (341/1 409) among girls, respectively. The prevalence of overweight-obesity in middle schools were 31.3% (591/1 658) among boys and 21.8% (342/1 571) among girls, respectively. The prevalence of premature puberty in primary schools were 15.0% (225/1 499) among boys and 14.2% (200/1 409) among girls, respectively. The prevalence of delayed puberty in middle schools were 14.3% (237/1 658) among boys and 14.9% (234/1 571) among girls, respectively. After adjusting the effects of region, age, one-child, family income and the parents' educational levels, multivariate logistic regression analysis showed that overweight-obesity had significantly positive association with premature puberty (OR=2.16, 95%CI: 1.56-2.99) among girls in primary schools, and significantly negative association with delayed puberty (OR=0.54, 95%CI: 0.36-0.80) among girls in middle schools when compared with students with normal weights, both P values were 0.05. Conclusion There was significantly positive association between overweight-obesity and premature puberty among girls, and significantly negative association with delayed puberty among girls in middle schools; but the association was not found among boys. Key words: Overweight; Obesity; Adolescent development; Gender differences