Secular trends in menarche age among Iranian girls: Probit analysis on cross-sectional data of Persian (Shahedieh) cohort

Background: Given concerns regarding changing puberty ages globally, examining current trends in specific societies is essential. Objective: This study aimed to determine secular changes in the age at menarche among Iranian girls in central Iran using the Probit model. Materials and Methods: This cross-sectional study utilized data from the entry phase of the Shahedieh cohort study, Yazd, Iran. In total, fertility information and menarche data were extracted from ۴,۸۵۴ women (aged ۳۵-۷۰ yr). Based on the menarche age data of these individuals, the proportion of those who had reached menarche in each of the ۳ birth decades (۱۹۴۶-۱۹۵۷, ۱۹۵۸-۱۹۶۹, and ۱۹۷۰-۱۹۸۱) was calculated. To calculate this proportion, a hypothetical time origin was considered for each decade, and the Probit model was employed to calculate the probability of menarche at each age. Results: Findings indicate that approximately ۱۰% of Iranian girls experienced menarche before age ۱۱, while ۹۰% reached menarche by age ۱۴.۸۹, with a median age of ۱۲.۸۹ yr. A significant downward trend in the age at menarche was observed; girls born between ۱۹۴۶-۱۹۵۷ experienced significantly later menarche compared to those born in the ۱۹۵۸-۱۹۶۹ and ۱۹۷۰-۱۹۸۱ cohorts at the ۱۰th, ۲۵th, ۵۰th, and ۷۵th percentiles. Conclusion: The observed downward trend in menarche age in central Iran aligns with results from similar studies in developing countries. This declining trend has historically been attributed to lifestyle-related variables. Today, this decreasing trend (acceleration of puberty) can be attributed to poor nutritional habits, sedentary lifestyles, or a physiological response to increased physical and mental stress.

کلیدواژه ها:

Cross-sectional studies ، Menarche ، Life change events ، Puberty. ، مطالعه توصیفی-مقطعی ، منارک ، رویدادهای حیاتی تغییردهنده زندگی ، بلوغ.