| Objective: To explore the trend and characteristics of pubertal development trajectories on breast,pubic hair,axillary hair and menarche of girls and first ejaculation of boys based on a puberty cohort.To investigate the status of emotional and behavioral problems of boys and girls in grade 6 to 9 after 5 years of follow-up,and explore the association between the pubertal development trajectories and emotional and behavioral problems.Methods: By using purposive sampling,four representative urban primary schools in a district of Chongqing were selected,in which,all students in grades one to four were eligible to participate with informed consent.A total of 1,429 students(695 boys and 734 girls)were recruited for the baseline survey,pubertal development examinations were conducted half-yearly.In total,ten follow-ups had been conducted and were included in the present analyses.The Group-Based Trajectory Model(GBTM)was used to explore the pubertal development trajectories in boys and girls.The data about children’s emotional and behavioral problems were collected through the Achenbach Youth Self-report(YSR)and the Screen for Children Anxiety Related Emotional Disorders(SCARED)at the 10 th follow-up survey.The rank-sum test and chi-square test were used to compare the scores and detection rate of children’ emotional and behavioral problems with different demographic characteristics and pubertal development trajectories.The multiple linear regression was used to explore the association between pubertal development trajectories and children’s emotional and behavioral problem.Results:(1)The pubertal development trajectories in boys and girls: Three sub-groups of "earlier development group","general development group" and "faster development group" were explored for girls’ breast development,accounting for 16.5%,52.5% and 31.0% of the total subjects,respectively.The age of breast development onset in three groups was 9,10 and 11.5 years old,respectively.It took girls in the "early development group" and "general development group" 5 years from breast development onset to maturity,and 4.5 years in the "faster development group".Two sub-groups of "earlier development group" and "later development group" were identified for girls’ pubic hair development,accounting for 38.3% and 62.7% of the total subjects,and the ages of pubic hair development onset in each group was 11 and 12 years,respectively.Girls in two sub-groups took 4 years from pubic hair development onset to maturity.Two sub-groups of "earlier development group" and "later development group" were explored for girls’ axillary hair development,accounting for 30.7% and 69.3% of the total subjects,and the age of axillary hair development onset in each group was 12 and 14 years,respectively.3 years were needed for girls in the "earlier development group" from the axillary hair development onset to maturity.Two sub-groups of ―earlier menarche group‖ and ―later menarche group‖ were identified for girls’ menarche,accounting for 57.4% and 42.6% of the total subjects,and the age of menarche in each group was 12 years and 15 years,respectively.Two sub-groups of ―earlier ejaculation group‖ and ―later ejaculation group‖ were explored for boys’ first ejaculation,accounting for 36.3% and 63.7% of the total subjects,and the age of first ejaculation in each group was 12.5 years and 16 years,respectively.(2)The association between children’s pubertal trajectories and emotional and behavioral problems: Totally,1,002 subjects(488 boys/514 girls)participated in the investigation of emotional and behavioral problems.The comparation of emotional and behavioral problems of children with different demographic characteristics showed that girls’ internalizing problem(Z=6.720,P<0.001),externalizing problem(Z=3.227,P<0.001),total emotional and behavioral problem(Z=4.659,P<0.001)and anxiety(Z=6.077,P<0.001)were significantly higher than that of boys.The levels of externalizing problem(Z=2.519,P=0.012),total emotional and behavioral problem(Z=2.482,P=0.013)and anxiety(Z=2.620,P=0.009)of children with sibling(s)were significantly higher than those of the only child.The level of externalizing problem(Z=2.202,P=0.028)and total emotional and behavioral problem(Z= 2.037,P=0.042)of children with divorced parents were significantly higher than those without divorced parents.Multiple linear regression results showed that girls in ―earlier menarche group‖ were more likely to have internalizing problem(β=0.100,P=0.029),total emotional and behavioral problems(β=0.092,P=0.048)and anxiety(β=0.095,P=0.039)than those in ―later menarche group‖.Boys in ―earlier ejaculation group‖ were more likely to have internalizing problem(β=0.109,P=0.019)total emotional and behavioral problem(β=0.109,P=0.018)and anxiety(β=0.108,P=0.017)than those in ―later ejaculation group‖.No significant associations between girls’ breast,pubic hair and axillary hair development trajectories and emotional and behavioral problems were found(p> 0.05)in our study.Conclusion:There are different trends in the development of breast,pubic hair,axillary hair and menarche of girls and first ejaculation of boys.The characteristics of development trajectories of those pubertal events can be observed by GBTM explicitly.Girls have more emotional and behavioral problems than boys.Girls with earlier onset of menarche and boys with earlier attainment of first ejaculation were associated with higher level of internalizing problem,total emotional and behavioral problems,and anxiety.There were no significant associations between breast,pubic hair and axillary hair development trajectories and emotional and behavioral problems in girls(P>0.05). |
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