[Association between age at menarche and height and leg length in adult women: findings from survey in 10 areas in China].

Objective: To describe the regional differences and secular trend in age at menarche, height and leg length in adult women aged 30-79 years in 10 areas included in China Kadoorie Biobank study (CKB), and evaluate the association between age at menarche and height and leg length in adult women in China. Methods: A total of 285 187 women, who had data on age at menarche and who had their menarche at the age between 9-18 years, were included in the analysis. Multiple linear regression models were used to assess the association between age at menarche and height and leg length. Subgroup analyses were performed for different birth cohorts and living areas (urban area or rural area). Results: The overall means (standard deviation) of age at menarche, height and leg length were 15.2 (±1.7) years, 154.2 (±6.0) cm and 71.0 (±3.7) cm, respectively. A significant increasing trend was observed in the mean height and leg length in different birth cohorts(trend: all P<0.001), while a decreasing trend was observed in the mean age at menarche, except for a slight increase in women born in 1940s (trend: P<0.001). Adjusted for age, study area, educational level and hip circumference (only for models for leg length), the average height and leg length in women increased by 0.17 cm and 0.20 cm, respectively, for each later age at menarche (both P<0.001). The positive associations between age at menarche and both height and leg length were stronger in younger birth cohorts (interaction: both P<0.001). Conclusion: Age at menarche was positively associated with height and leg length in women in 10 areas included in CKB study.