Age at Menarche and its Related Factors among School Girls, in Zanjan, Iran

There are differences in the age at menarche in different countries and it seems that in recent decades gradually the age of puberty is declining. The aim of the present study was to determine the age at menarche and its related factors in school girls in Zanjan city, Iran.
This cross-sectional study was conducted on 1,500 healthy school girls between 6-17 years old who were selected on the basis of a multistage probability sampling. Age at menarche, birth weight, family size, Body Mass Index (BMI), fast food consumption, and physical activity, were recorded. Data were analyzed using SPSS version 16.0.
Out of 1,500 students, 273 girls (18.2%) had experienced menarche with a mean age of 12.6±1.6 (95% confidence interval [C]: 12.4-12.8), and a median age of 13 years. The prevalence of early menarche, was 10.3%, (95% CI: 6.6%-14.1%). A significant association between menarche and BMI, frequency of fast food consumption and birth rank was observed; however, we didn’t find a significant association between physical activity (P>0.05) and birth weight (P>0.05) with menarche.
The mean age of menarche in our study was 12.6±1.6 years old, similar to other studies in Iran, and it was significantly associated with higher BMI.