Decline in the Age of Menarche in İstanbul Schoolgirls Over the Last 12 Years.

Abstract

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. To assess the trend in age at menarche (AAM), and its associated factors in Istanbul over the last 12 years. 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. 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. 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.