Investigation Of Menarche And Its Relative Factors Of Junior Middle School Students In Ninghe District Of Tianjin

Objective:This study measured the menarcheal age and its characteristics of female junior middle school students in Tianjin and explored factors that could impact on the onset of menarche.To provide suggestions for further development of adolescence education on physiological and mental health,and to be useful for the study of dynamic change of menarcheal age in Tianjin area.Methods:5337 junior middle school girls in Tianjin area were selected by stratified random sampling method,and investigated by the method of physical examination and questionnaire survey.Using Lime Survey recover and collect all the data,then established the database.After logic checked by Epidata 3.0,using SPSS23.0 to analyse all the statistics,including one-way ANOVA,chi-square test,t test,Kruskal Wallis H test,ROC curve and multiple response analysis.Results: 1.Age at menarche Among 4127 female students,1383 students experienced menarche,with the menstruation rate of 33.51%.Mean AAM was 12.68±1.19 years old.The rate of menarche at the age of 9-10 years old was 1.17%,the lowest.While the rate of menarche over 15 years old was 99.05%,the highest.Girls in 7-8 years old group with breast development was 3.01%,pubic hair development was later than breast development about 1 year.The levels of height,weight,BMI,waist circumference,hip circumference,and the skin fold thickness in precocious puberty girls were higher than those in normal group.The difference was statistically significant(P<0.05).2.Family factors effect on the age at menarche One-way ANOVA showed that girls with higher family income,better education of their parents had earlier menarcheal age.3.Inheritance and postnatal factors effect on the age at menarche Kruskal Wallis H test showed that the AAM of girls is consistent with that of their mothers.Girls whose mother’s AAM was earlier had earlier menarcheal age.According to One-way ANOVA,girls with low birth weight had earlier AAM than those with normal birth weight and giant infants.There was no significant difference in the average AAM among the girls with different lactation time.4.Constitution factors effect on the age at menarche 4.1 Comparison of the rate of menarche in the marasmus group,the normal group,the over-weight group and the obesity group According to age,girls were divided into groups of 10-11 、11-12、12-13 and13-14 years old.After that,girls of each group were divided into four group:marasmus group,the normal group,the over-weight group and the obesity group according to BMI.The rate of menarche in the marasmus group,the normal group,the over-weight group and the obesity group in 10-11 years old group was 0.00%、3.17%、10.39%、19.55%;For 11-12 years old group,that is 0.00%、32.63%、39.58%、45.74%;For 12-13 years old group,that is 27.27%、69.08%、70.31%、76.71%;For 13-14 years old group,that is 50.00%、90.09%、100.00%、92.00%.The difference was statistically significant(P<0.05).4.2 Comparison of body fat indicators between the menstruation menarche girls and the non-menstruation menarche girls Girls in each age group were divided into the menstruation menarche group and the non-menstruation menarche group,and the mean values of height,weight,BMI,waist circumference,hip circumference,waist-to-hip ratio,waist-to-height ratio and the skin fold thickness of girls in each group were calculated.The results showed that the levels of height,weight,BMI,waist circumference,hip circumference,and the skin fold thickness in menstruation group were higher than those in non-menstruation group except the waist-to-hip ratio and the waist-to-height ratio.The difference was statistically significant(P<0.05).4.3 ROC curve analysis of weight and BMI The area under curve(AUC)of weight was 0.702,AUC of BMI was 0.653.The optimal cut-off value of weight and BMI were 46.15 and 17.23.The sensitivity and specificity of weight were 0.654 and 0.683,the sensitivity and specificity of BMI were 0.875 and 0.383.5.Diet factors effect on the age at menarche In terms of the consumption of sugary drinks and ice cream,the number of people in the menstruation menarche group was more than that in the non-menstruation menarche group.The difference was statistically significant(P<0.05).6.Others 6.1 Physical exercise frequency effect on the age at menarche The average AAM of the girls who hardly ever exercise was 12.44.The average AAM of the girls who exercise 1-3 times a week was 12.69,the average AAM of the girls who exercise 4-6 times a week was 12.72 and that of the ones who exercise everyday was 12.80.The difference was statistically significant(P<0.05).6.2 Time spending on watch TV,computer and mobile phone effect on the age at menarche There was no significant difference in the average age at menarche between girls who watched TV,computer and mobile phone for less than 30 minutes,1-2 hours and more than 3 hours everyday(P>0.05).6.3 Sleep duration effect on the age at menarche In different age groups,there was no significant difference in the average AAM between girls who sleep less than 8 hours,8-10 hours and more than 10 hours(P>0.05).Conclusions: 1.Mean age at menarche of junior middle school students in Ninghe district of Tianjin was 12.68±1.19 years old.2.Girls with higher family income and better education of their parents had earlier menarcheal age.Both AAM of mothers and birth weight had influence on the age at menarche of girls.Girls with earlier mother’s age at menarche and lighter birth weight had earlier menarcheal age.3.Obesity may advance menarche.The optimal cut-off value of weight and BMI were worth in predicting menstruation.4.Regular consumption of sugary drinks and ice cream may advance menarche.5.Regular exercise may delay menarche.