Menstrual patterns and risk of adult-onset diabetes mellitus.

We examined the association between menstrual patterns and risk of developing adult-onset diabetes in a prospective study of 668 white, college-educated women who completed menstrual diaries throughout their reproductive years. We calculated summary measures of cycle length and variability and bleeding duration for ages < or = 22, 23-27, 28-32, and 33-37 years. The analysis included 35,418 person-years of follow-up and 49 self-reported cases of diabetes (median age at diagnosis, 63 years). There was no association between diabetes risk and age at menarche, mean cycle length, cycle variability, or frequency of long cycles (> 42 days). Longer bleeding periods in the mid- and late reproductive years were somewhat associated with an increased risk of diabetes (adjusted rate ratio 1.4, 95% confidence interval 1.0-1.8 per day increase in bleeding duration for menses during ages 28-32). These results do not support the association of long or irregular menstrual cycles with post-menopausal diabetes incidence, but do suggest a possible association of longer bleeding duration with subsequent onset of diabetes.