The role of BMI across the life course in the relationship between age at menarche and diabetes, in a British Birth Cohort

AIMS Previous research showing an inverse association between age of menarche and adult diabetes relied on recalled age at menarche and did not adjust for BMI across the life course. We investigated the relationship between age at menarche and diabetes, and whether childhood, adolescent or adult BMI attenuates this relationship. METHODS We used data from the Medical Research Council National Survey of Health and Development, a British birth cohort study of men and women born in 1946, with contemporaneous recording of the age of menarche, BMI at 2, 7, 15 and 20-53 years and diabetes status to 53 years. RESULTS A significant inverse relationship between age at menarche and diabetes [hazard ratio = 0.73 per year older age at menarche (95% CI 0.56-0.96), P = 0.02] was attenuated by adjustment for adult BMI [hazard ratio 0.85 (95% CI 0.65-1.10), P = 0.2]. The effect of age at menarche on Type 2 diabetes was very similar to that for all types of diabetes. Attenuation of the association between age at menarche and diabetes was also observed with BMI at 15 years, but less so with BMI measured earlier in childhood. CONCLUSIONS Earlier age at menarche is associated with a higher risk of diabetes, and specifically Type 2 diabetes, in later life, which is most strongly attenuated by adolescent and adult adiposity. Early menarche may be clinically useful in identifying women who are at risk of later adiposity and so of developing Type 2 diabetes.