A Study On The Age At Menarche And Its Influencing Factors Among Adolescent Girls

Objective:To know age at menarche and the characteristics of menarche age of the adolescentgirls in Wuxi city and to investigate its influencing factors. To provide scientific basisfor carrying out adolescent health education and to be benefit for the research ofdynamic changes of menarche age in Wuxi in the future.Methods:10824Chinese students from selected36schools in Wuxi were surveyed by usingrandom stratified cluster sampling method. Self-designed questionnaire was used tocollect the age at menarche and its influencing factors.10693available questionnaireswere retried finally. All the data were input into the database of Epidata3.02, andanalyzed by using the statistical software of SPSS17.0. The statistical methods includeprobability unit method, variance analysis, chi square test, t-test, multiple linearregressions, and stepwise Logistic regression, receiver operating curve.Results:1. Age at menarcheIn the study, there were5564students with menarche; the incidence rate ofmenarche was52.03%. The rate of menarche at the age of9years was5.98%, the rateof menarche increased with age. The rate of menarche at the age of12years was over50%and14years over90%. The average age of menarche of the girls in Wuxi city was12.33years (95%CI:12.23-12.43years) by probability unit method. The top incidencerate of menarche months was July and August (July made up11.9%and August madeup14.1%), The lowest incidence rate of menarche months were November andDecember(November made up3.9%and December made up6.1%). The students withmenarche before10years were176, accounting for1.64%. The average age ofmenarche of local students was12.13, which was less than non-local students (12.45). There was significant difference in different genders (P<0.05).2. Family environment factors effect on the age at menarcheOne-way ANOVA analysis showed that parental relation, family income, parents’education level, parental rearing pattern were influence factors in the age of menarche.It is concretely represented in the following aspects: The average age of menarche of thegirls whose parental relationship was not good, family income was high, parents’education was good and parents praised too much was earlier. There was a significantnegative correlation between family conflict and age of menarche was, the correlationcoefficient was-0.092. In other words, the greater family conflict the earlier age ofmenarche. Moreover, multiple linear regressions showed that parental relation, familyincome, parents’ education level and family conflict were main factors in the age ofmenarche, there was significant statistical difference. Among them, maternaleducational level mainly affected on the age of menarche, the higher maternaleducational level, the age of menarche was earlier.3. Negative life events effect on the age at menarcheThe total of negative life events in menstruation menarche girls was higher thanthat in the non-menstruation menarche girls. The incidence of menarche was related to8negative life events except for family economic difficulty and failed in the election of“Triple-A” outstanding students.4. Constitution factors effect on the age at menarche4.1Overweight and obesity effect on the age at menarcheIt shows the tendency that the obese group is higher in occurrence rate of menarchethan that of overweight group which is higher than normal group in10、11、12groups.There was also no obvious difference in13years group. The occurrence rate ofmenarche in girls who had a normal BMI both during early childhood and adolescentwas36.97%. The occurrence rate of menarche in girls who had a normal BMI duringearly childhood but became overweight or obesity in adolescent was56.12. Theoccurrence rate of menarche in girls who had an overweight or obesity BMI in earlychildhood but normal in adolescent was63.89%. The occurrence rate of menarche ingirls who were persistently overweight or obesity in early childhood and adolescent was69.14%. There was significant difference in different genders (P<0.05).Logisticregression analysis results suggested that girls who were overweight or obesity in early childhood, and persistently overweight or obesity in adolescent, were more likely tohave menarche (OR=4.170，95%CI=2.533-6.864) in comparison with those who had anormal BMI during early childhood but became overweight or obesity inadolescent(OR=2.267，95%CI=1.476-3.481) or who had a overweight or obesity BMIin early childhood but normal in adolescent(OR=3.317，95%CI=1.637-6.723).4.2Optimal cut-off point of BMI on age at menarcheThe average weight of the menstruation menarche girls aged from10-11、11-12、12-13and13-14was higher than that of the non-menstruation menarche girls. Heightand BMI were also so. All of them were significant statistical differences. The areasunder curve (AUC) of weight was0.73and AUC of BMI was0.68. There wassignificant statistical difference(Z=4.20, P＜0.05).Both of the indexes in low age groupwere higher than high age group. The optimal cut-off point of BMI and weight were17.36and39.75. The sensitivity of weight and BMI were0.74and0.53. The specificityof weight and BMI was0.60and0.76. The optimal cut-off point of weight on differentage groups were different, but the optimal cut-off point of BMI on different age groupstended to be uniform.5. OthersThe average age of menarche of girls who did not do some exercises was11.81,The average age of menarche of girls who did occasionally exercises was12.11and thatof the ones who did a lot of exercises was12.36. There was significant difference(P＜0.05).There was no obvious difference of the average age of menarche of the studentswho watching TV or going online less than1hour,1-3hours and more than3hours.There was also no obvious difference of the average age of menarche of the studentswhose sleeping time less than7hours,7-9hours and more than9hours.Conclusions:1. The average age of menarche of the girls in Wuxi city was12.33years old. Thetop incidence rate of menarche months was July and August, November and Decemberwas lowest.2. Parental relation, family income, parents’ education level and family conflictwere main factors in the age of menarche; maternal educational level mainly affected onthe age of menarche, the higher maternal educational level, the age of menarche was earlier.3. The total of negative life events in menstruation menarche girls was higher thanthat in the non-menstruation menarche girls.4. The average weight of the menstruation menarche girls was higher than that ofthe non-menstruation menarche girls. Height and BMI were also so. It shows thetendency that the obese group is higher in occurrence rate of menarche than that ofoverweight group which is higher than normal group. Overweight or obesity in earlychildhood effected on age at menarche. The optimal cut-off point of BMI is applicablein predicting the age of menarche.5. The menarche of the girls who seldom did exercises would be ahead of advancewhile the menarche of the girls who often did exercises would be late.