Sex differences in the growth and physical development of Beijing school-aged children and adolescents

Abstract

Objective The study aimed to explore sex differences in the growth and physical development of Beijing school-aged children and adolescents.

Methods Data obtained from regular health examinations of 94 122 school-aged children and adolescents aged 6-18 years old were collected from primary and high schools in Shunyi District from 2009 to 2018, and a longitudinal dataset was compiled with complete anthropometric parameters including height, weight, and BMI levels after linkage of individual-level information. The age-specific growth rate was calculated and a linear mixed-effects model was used to identify sex differences according to chronological or relative age to peak height velocity (PHA).

Results Height, weight, and BMI levels increased with age in both boys and girls. Girls were taller than boys in the 10–11-year-old age group, catch-up growth in height was observed in boys at age 12, whose height surpassed that of girls thereafter. Boys had a higher weight and BMI than girls in all age groups ( P<0.01). Sex differences were found in the growth rates of height, weight, and BMI levels ( t = −67.56, −47.46, 3.22, P<0.01), which was demonstrated by the interaction effect of sex and age in the linear mixed-effects model. The PHA in boys was 12 years old, which was two years later than the PHA in girls. Boys reached peak weight velocity at 12 years old, lagging one year behind girls who reached their peak at 11 years old. The curves of the BMI growth rate with age showed double peaks in boys and the first peak appeared at 10 years, which was one year earlier than girls. The change in weight was highly synchronized in time with the increase in height, after adjusting for the growth rate of weight by PHA. Weight velocity increased with age before the onset of puberty until PHA, and then it declined; boys presented with obvious fat accumulation before the onset of puberty.

Conclusion Sex differences in the growth and physical development of school-aged children and adolescents were persistent and apparent, and the change in weight was highly synchronized in time with the increase in height.

Abstract

【摘要】 目的 探索学龄儿童青少年体格发育指标增长速度的性别差异, 为明确中国儿童青少年的生长发育规律提供科 学依据。 方法 基于北京市顺义区 2009—2018 年 6~18 岁学龄儿童及青少年健康体检资料, 经匹配个人信息后共纳人 94 122 名学生, 计算年龄别身髙、体重、体质量指数 (BMI) 增长速度, 以及以身髙增速髙峰年龄 (PHA) 为基点的体重和 BMI 增长速度, 采用混合效应线性模型分析增长速度的性别差异。 结果 男、女生平均身髙、体重和 BMI 随年龄增长而增长, 除 10~11 岁男生平均身髙低于女生外, 其他年龄段男生平均身髙均髙于女生, 各年龄段男生的平均体重和 BMI 均髙于女 生 ( P 值均<0.01); 混合效应线性模型结果显示身髙、体重和 BMI 的增长速度存在性别年龄交互作用 ( t 值分别为 −67.56, −47.46, 3.22, P 值均<0.01), 即每个年龄段身髙、体重和 BMI 的增长速度具有性别差异;男生 PHA 为 12 岁, 女生 PHA 为 10 岁, 男生出现身髙增速髙峰较女生晚 2 年, 但峰髙髙于女生。男生体重增长速度髙峰年龄为 12 岁, 女生为 11 岁。男生 BMI 增长速度曲线呈“双峰”状且最大增长速度年龄为 10 岁, 女生为 11 岁, 男生较女生早 1 年;调整 PHA 后的体重增长速 度曲线均显示, 男生和女生青春期体重增长与身髙增长相一致, 即体重增长速度在 PHA 前随年龄增加而升髙, 在 PHA 达 到髙峰, 之后又下降; 7~9 岁男生可能出现青春期启动前脂肪堆积。 结论 青春期各年龄段男、女生身髙、体重和 BMI 的 增长速度存在性别差异, 且体重的变化与身髙增长密切相关。