Sex differences in the growth and physical development of Beijing school aged children and adolescents / 中国学校卫生

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.