7338 Temporal Trend of Age at Menarche in Korean Adolescents: A Population-based Study

Abstract Disclosure: H.Y. Kim: None. J. Kim: None. Background: The age at menarche has been decreasing worldwide. Previous studies in Korean adolescents also reported a downward trend of age at menarche. We investigated the current trends of age at menarche in Korean adolescents using nationally representative data. Methods: Data from the Korea National Health and Nutrition Examination Survey 2007-2021 were used in this study. A total of 50,730 females born between 1927 and 2004 with information on age at menarche were included in this study. The trend of age at menarche was analyzed according to 12 birth-year groups (with 5-year interval) using quantile regression analysis. Results: The mean age at menarche decreased over time, from 16.58±0.02 years for females born before 1950 to 12.45±0.04 years for females born between 2000 and 2004 (P <0.001). According to the percentiles group of age at menarche, the menarche age decreased by 0.073 years per year (95% confidence intervals [CIs], 0.072-0.074) in the 50th percentile group, 0.088 years per year (95% CI, 0.085-0.091) in the 97th percentile group, and 0.050 years per year (95% CI, 0.048-0.052) in the 3rd percentile group (P <0.001 for all). A decreasing trend of age at menarche was more prominent in the obese group (0.080 years per year, 95% CI, 0.078-0.082) compared to the non-obese group (0.069 years per year, 95% CI, 0.068-0.071) (P <0.001 for both). Conclusion: Ongoing downward trend in age at menarche was observed in Korean adolescents born until 2004, decreasing by 0.73 years per decade. A downward trend was faster in individuals in the higher percentile of age at menarche and in those with obesity. Presentation: 6/1/2024