Age at menarche, abnormal glucose tolerance and type 2 diabetes mellitus: The Rancho Bernardo Study

We examined the association of age at menarche with risk of abnormal glucose tolerance (AGT) and type 2 diabetes in postmenopausal women.

Participants were 997 women aged 50-92 years who had a clinic visit in 1984-87, when reproductive and diabetes history were recorded, and an oral glucose tolerance test administered. Information on age at menarche was collected in 1989. Diabetes status was based on WHO 1999 criteria, and AGT on having impaired fasting glucose (IFG) or impaired glucose tolerance (IGT).

The average age was 69.5 years; 12.5% had diabetes and 29.8% had AGT. Menarche was < 12 years in 14.5%, 12-15 years in 78.9% and > or = 16 years in 6.6%. Age and body mass index (BMI) predicted AGT (p < 0.001, p = 0.003, respectively), while age, BMI and family history of diabetes predicted type 2 diabetes (p < 0.001, p < 0.001, p = 0.02, respectively). Polynomial logistic regression showed no association of menarche with AGT or type 2 diabetes risk. In linear regressions, however, older age at menarche was associated with lower fasting (p = 0.01) and post-challenge plasma glucose (p = 0.03). Covariates, especially BMI, weakened these associations, although women with menarche > or = 16 years still had lower post-challenge (0.86 mmol/l, p = 0.05) and fasting glucose (0.26 mmol/l, p = 0.11) than those with menarche < 12 years.

Age at menarche was not associated with AGT or type 2 diabetes risk. Late age at menarche was inversely associated with fasting and post-challenge glycemia. Obesity may mediate the observed associations.