Decline in the Age of Menarche in Ýstanbul Schoolgirls Over the Last 12 Years

INTRODUCTION: Menarche is the endpoint of a sequence of maturational events of female puberty. The timing of menarche is a strongly heritable trait. However, secular trends suggest that lifestyle and environmental factors are important.
OBJECTIVE: To assess the trend in age at menarche (AAM), and its associated factors in Istanbul over the last 12 years.
METHODS: A cross-sectional study was carried out between March and April 2022 on schoolgirls aged 9-18 years. A predesigned and self-administered questionnaire was filled out anonymously by the students. The data of AAM was included in the statistical analysis if the time of AAM is remembered for months and years. A probit model was used to calculate the median AAM. The findings were compared with those from the study performed 12 years ago in the same region of Istanbul.
RESULTS: Among 9000 girls to whom the questionnaire was distributed, 1749 (19.5%) responded. The median AAM of 1374 girls whose AAM information was considered valid was 12.04 years (95% CI 12.01−12.13), 0.7 years lower than was reported 12 years ago (p<0.0001). AAM was correlated positively with maternal AAM, and negatively with body mass index (BMI) SDS and maternal educational status (p<0.0001, <0.0001, 0.002), respectively. There was no correlation between the AAM and birth weight. Girls with BMI percentile ≥85% (n=251) had earlier menarche than the ones with BMI percentile <85% (n=1072) (11.5 vs. 12.1 years, p<0.0001). Among the mother-daughter pairs (n=1162), AAM of girls was 0.91 years (median 0.94 years) earlier than their mothers.
DISCUSSION AND CONCLUSION: The present study demonstrates a significant downward trend in the menarcheal age in Istanbul over the last decade. Our findings support a strong contribution of genetic factors and BMI on AAM.