Objective: To investigate the sleeping status of the first grade primary students aged 6-8 in Beijing, to investigate the association between maternal parenting stress and children s sleep, and to inform intervention of addressing sleep problems among children in Beijing. Methods: Online survey was conducted based on the child cohort study designed to study puberty, obesity, and cardiovascular risk (PROC). The Children s Sleep Habits Questionnaire (CSHQ) and Parenting Stress Index Short Form (PSI-SF) were completed by parents, and 1 136 school aged children and their mothers were included as study participants. Logistic regression models were used to determine the association between maternal parenting stress and children s sleep. Results: The prevalence of sleep problems among first grade primary students was 78.52%. Among the children who received PSI-SF, the score of children with sleeping problems(86.66±17.31) was higher than that of the children with no sleeping problems(78.59±17.75)( t =6.42, P <0.01). After adjusting sociodemographic characteristics, multivariable logistic regression results showed children of mothers with parenting stress were more likely to have sleep problems ( OR =2.52, 95% CI =1.55-4.11, P <0.01). Taking 3 dimensions in PSI-SF as independent variables, the analysis indicated that compared with the children having mothers free from parental stress and difficult children, the children with mothers with parental stress were more likely to suffer from the sleeping problems( OR = 1.66 ,1.76, P <0.05). Conclusion Sleep problems are prevalent among first grade primary students, and it underscores providing psychological support to alleviate maternal parenting stress to address children s sleep problems.

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.

Objective: To explore sex differences between weight and systolic blood pressure (SBP) changes among school-age children and adolescents in Beijing, and to provide a basis for priority intervention to control the rapid growth of body weight and blood pressure. Methods: Anthropometric measurement data of 70 288 children and adolescents from primary and high schools in Shunyi District were collected from 2009 to 2018, and a longitudinal dataset with complete data related to weight and BP after individual data linkage was compiled. The age-specific weight and SBP growth rates were calculated, and a linear mixed-effects model was used to identify sex differences in chronological growth rates. Results: Weight and SBP increased with age in both boys and girls, and the mean weight and SBP were higher in boys than in girls across all age groups. The result of the linear mixed-effects model indicated apparent sex differences in weight and SBP growth rates, with an age and sex interaction term(β=-0.35, -0.40, P<0.01). The age at peak weight velocity (PWA) was 12 years old and the age at peak SBP velocity was 13 years old in boys, which occurred one and three years later than for girls, respectively. In addition, the peak weight and SBP velocity were higher in boys than in girls. The curves of the SBP growth rate adjusted for the PWA, showed that the peak SBP velocity occurred two years before PWA and the second peak SBP velocity occurred at the PWA, which indicated "double peaks" in both boys and girls. The SBP growth rate was always higher in boys than in girls, and the rates declined after PWA. Conclusion Sex differences in weight and SBP growth rates were persistent and obvious in school-age children and adolescents in Beijing and the change in SBP was highly time synchronized with the increase in weight.