Age at menarche and incidence of diabetes: a prospective study of 300,000 women in China.
Yang L., Li L., Peters SAE., Clarke R., Guo Y., Chen Y., Bian Z., Sherliker P., Yin J., Tang Z., Wang C., Wang X., Zhang L., Woodward M., Chen Z.
Previous studies of mostly Western populations have reported inconsistent associations between age at menarche and risk of diabetes. We examined such associations among Chinese women who tend to have later menarche age than women in West. China Kadoorie Biobank recruited 302,632 women aged 30-79 years from 10 areas across China in 2004-8, recording 5,391 incident cases of diabetes during 7-years follow-up among 270,345 women without diabetes, cardiovascular disease or cancer at baseline. Cox regression models yielded adjusted hazard ratios (HRs) for incident diabetes associated with age at menarche. Overall, the mean age at menarche was 15.4 years, which was decreasing across successive generations. Age at menarche was linearly and inversely associated with incident diabetes, with adjusted HR of 0.96 (95%CI: 0.94-0.97) per year delay. The HRs were greater in younger than older generations (0.93 [0.90-0.97], 0.95 [0.93-0.98] and 0.97 [0.95-0.99] for women born in the 1960s-1970s, 1950s and 1920s-1940s, respectively). Further adjustment for adulthood body mass index significantly attenuated the association (0.99, 0.97-1.00), especially among those born before 1950 (1.00, 0.97-1.02). In Chinese women age at menarche was inversely associated with incident diabetes. Much of this association was mediated through increased adiposity associated with early menarche, especially in older generations.