Pubertal Timing And Analysis Of Related Factors Among Primary And Middle School Students In Zhengzhou City

ObjectiveTo understand the characteristics and current status of pubertal timing among primary and middle school students in Zhengzhou City, and to analyze possible related factors of early puberty. To explore the association of various factors with pubertal timing and possible gender differences, so as to lay the foundation of subsequent cohort study of this group and provide basis for uncovering the mechanism of puberty.MethodsTwo primary schools and one middle school were selected from urban area in Zhengzhou City and cluster sampling method was used. Girls from Grade 2-3 in the two primary schools and Grade 1-2 in the middle school were recruited, and the effective sample size of each grade was no less than 150. Boys from Grade 3-4 in the two primary schools and Grade 1-2 in the middle school were selected, and the effective sample size of each grade was also no less than 150. Data were gathered through physical examination (such as height, weight, waistline and the skinfold thickness), secondary sexual characteristics examination (including testicular volume and pubic hair development in boys and breast development in girls) and questionnaires survey (such as basic demographic information, daily contact with household chemicals, physical activity, psychological behavior development and legumes and soy food intake).Results1. Boys’and girls’pubertal timing status The number of boys aged 8-9 or 12 with no less than 4 ml testicular volume respectively was 8 (6.2%),13 (7.9%),102 (89.5%). Boys aged 8-9 did not begin pubic hair development, and more than half (55.3%) of boys aged 12 did not begin either. Among girls aged 7-8,81.8% and 53.1% did not begin breast development, respectively. Girls aged 12 all began breast development. Menarche mostly occurred in summer, and girls whose menarche occurred in June, July, or August were 30 (12.1%),44 (17.7%),32 (12.9%), respectively. With the development of puberty, indicators of morphological development such as boys’ and girls’ height, weight, waistline and girls’ skinfold thickness were on the rise. Among 610 boys, the earlier puberty group included 111 (18.2%), normal group 449 (73.6%), and delay group 50 (8.2%). Among 644 girls, the earlier puberty group included 79 (12.3%), normal group 500 (77.6%), and delay group 65 (10.1%). The early pubertal timing rate of boys (18.2%) was higher than that of girls (12.3%), and the difference was statistically significant (P<0.05).2. Single factor analysis of early pubertal timing Boys with at least one smoking parent were more likely to develop early puberty than boys whose parents did not smoke, with statistical significance (P<0.05). The distribution difference of whether someone usually smoked in girls’ living or learning environment between the earlier puberty group and on-time/late groups was statistically significant (P<0.05). The mean values of boys’ and girls’ BMI, waistline, and girls’ skinfold thickness and body fat percentage among the earlier puberty group were higher than those among on-time/late groups, with statistical significance (P<0.05). The overweight rate (with obesity) and the obesity rate of girls in the earlier puberty group were higher than those in on-time/late groups (P<0.05). The average marks of boys’ conduct problem and girls’ emotional symptom in the earlier puberty group were also higher than those in on-time/late groups (P<0.05).3. Multiple-factor analysis of early pubertal timing Parental smoking and waistline were related factors (OR respectively was 1.738,1.024, P<0.05) for boys to increase advanced puberty development, while someone smoking in the living or learning environment and abdominal skinfold thickness were related factors (OR respectively was 1.661,1.052, P<0.05) for girls.4. Waistline and boys’ sexual development Among each age group, the scores of testis and pubic hair development in larger waistline group were higher than those in normal group, and they were both higher than those in smaller waistline group.5. Abdominal skinfold thickness and girls’ sexual development Among each age group, the scores of breast development in larger abdominal skinfold thickness group were higher than those in normal group, and the scores in smaller abdominal skinfold thickness group were the lowest. In the 12-13 age groups, the mean values of abdominal skinfold thickness of girls having already experienced menarche were higher than those of girls not having experienced menarche (P<0.05).Conclusions1. The early pubertal timing rate of boys is higher than that of girls.2. Regardless of gender, primary and middle school students’passive smoking is associated with early pubertal timing.3. Waistline is related to boys’early puberty. Compared with their peers, boys with larger waistline are more likely to have earlier sexual development.4. Abdominal skinfold thickness is correlated with girls’early puberty. Compared with their peers, girls with larger abdominal skinfold thickness are more likely to have earlier sexual development.