[Relationship between body mass index and sexual development in Chinese children].

Objective: To investigate the relationship between body mass index (BMI) and sexual development in Chinese children. Methods: A nationwide multicenter and population-based large cross-sectional study was conducted in 13 provinces, autonomous regions and municipalities of China from January 2017 to December 2018. Data on sex, age, height, weight were collected, BMI was calculated and sexual characteristics were analyzed. The subjects were divided into four groups based on age, including ages 3-<6 years, 6-<10 years, 10-<15 years and 15-<18 years. Multiple Logistic regression models were used for evaluating the associations of BMI with sexual development in children. Dichotomous Logistic regression was used to compare the differences in the distribution of early and non-early puberty among normal weight, overweight and obese groups. Curves were drawn to analyze the relationship between the percentage of early puberty and BMI distribution in girls and boys at different Tanner stages. Results: A total of 208 179 healthy children (96 471 girls and 111 708 boys) were enrolled in this study. The OR values of B2, B3 and B4+ in overweight girls were 1.72 (95%CI: 1.56-1.89), 3.19 (95%CI: 2.86-3.57), 7.14 (95%CI: 6.33-8.05) and in obese girls were 2.05 (95%CI: 1.88-2.24), 4.98 (95%CI: 4.49-5.53), 11.21 (95%CI: 9.98-12.59), respectively; while the OR values of G2, G3, G4+ in overweight boys were 1.27 (95%CI: 1.17-1.38), 1.52 (95%CI: 1.36-1.70), 1.88 (95%CI: 1.66-2.14) and in obese boys were 1.27 (95%CI: 1.17-1.37), 1.59 (95%CI: 1.43-1.78), and 1.93 (95%CI: 1.70-2.18) (compared with normal weight Tanner 1 group,all P<0.01). Analysis in different age groups found that OR values of obese girls at B2 stage and boys at G2 stage were 2.02 (95%CI: 1.06-3.86) and 2.32 (95%CI:1.05-5.12) in preschool children aged 3-<6 years, respectively (both P<0.05). And in the age group of 6-10 years, overweight girls had a 5.45-fold risk and obese girls had a 12.54-fold risk of B3 stage compared to girls with normal BMI. Compared with normal weight children, the risk of early puberty was 2.67 times higher in overweight girls, 3.63 times higher in obese girls, and 1.22 times higher in overweight boys, 1.35 times higher in obese boys (all P<0.01). Among the children at each Tanner stages, the percentage of early puberty increased with the increase of BMI, from 5.7% (80/1 397), 16.1% (48/299), 13.8% (27/195) to 25.7% (198/769), 65.1% (209/321), 65.4% (157/240) in girls aged 8-<9, 10-<11 and 11-<12 years, and 6.6% (34/513), 18.7% (51/273), 21.6% (57/264) to 13.3% (96/722), 46.4% (140/302), 47.5% (105/221) in boys aged 9-<10, 12-<13 and 13-<14 years, respectively. Conclusions: BMI is positively correlated with sexual development in both Chinese boys and girls, and the correlation is stronger in girls. Obesity is a risk factor for precocious puberty in preschool children aged 3-<6 years, and 6-<10 years of age is a high risk period for early development in obese girls.目的： 评估中国儿童体质指数（BMI）与性发育水平之间的关系。 方法： 2017年1月至2018年12月在中国13个省、自治区、直辖市对3~<18岁的208 179名健康儿童进行横断面调查。调查指标包括性别、年龄、身高、体重，计算BMI值，并评估第二性征发育情况。根据年龄将3~18岁儿童分为3~<6岁、6~<10岁、10~<15岁、15~<18岁4组，采用多因素Logistic回归分析，分析每组BMI与性发育水平的相关性。根据BMI标准分为正常体重、超重、肥胖组，采用二分类Logistic回归分析组间早发育与非早发育分布差异。绘制曲线图分析青春期不同发育分期女童和男童的早发育百分比与BMI分布之间的关系。 结果： 208 179名健康儿童中女96 471名、男111 708名。多因素Logistic回归分析（以正常体重Tanner 1期为对照）发现超重及肥胖女童B2、B3、B4+期OR值分别为1.72（95%CI：1.56~1.89）、3.19（95%CI：2.86~3.57）、7.14（95%CI：6.33~8.05）及2.05（95%CI：1.88~2.24）、4.98（95%CI：4.49~5.53）、11.21（95%CI：9.98~12.59）；超重及肥胖男童G2、G3、G4+期OR值分别为1.27（95%CI：1.17~1.38）、1.52（95%CI：1.36~1.70）、1.88（95%CI：1.66~2.14）及1.27（95%CI：1.17~1.37）、1.59（95%CI：1.43~1.78）、1.93（95%CI：1.70~2.18），均P<0.01。3~<6岁肥胖女童B2期、男童G2期的OR值分别为2.02（95%CI：1.06~3.86）和2.32（95%CI：1.05-5.12），均P<0.05。6~<10岁超重女童性发育水平B3期的风险高达5.45倍，肥胖则高达12.54倍。超重女童发生早发育的风险是正常体重女童的2.67倍，肥胖女童则高达3.63倍，在男童分别为1.22和1.35倍（均P<0.01）。青春期不同发育阶段儿童早发育百分比随着BMI增加而增加，其中8~<9、10~<11、11~<12岁女童各BMI水平的早发育百分比分别从5.7%（80/1 397）、16.1%（48/299）、13.8%（27/195）至25.7%（198/769）、65.1%（209/321）、65.4%（157/240），9~<10、12~<13、13~<14岁男童分别从6.6%（34/513）、18.7%（51/273）、21.6%（57/264）至13.3%（96/722）、46.4%（140/302）、47.5%（105/221）。 结论： 中国儿童BMI与性发育水平呈正相关，女童的相关性更高。肥胖是3~<6岁学龄前儿童发生性早熟危险因素。6~<10岁是肥胖女童早发育的危险时期。.