Oral contraceptive use and association with glucose, insulin, and diabetes in young adult women: the CARDIA Study. Coronary Artery Risk Development in Young Adults

OBJECTIVE: We studied the associations between 1) current use of oral contraceptives (OCs) and 2) glucose levels, insulin levels, and diabetes in young women. RESEARCH DESIGN AND METHODS: Subjects were women (n = 1,940) in the Coronary Artery Risk Development in Young Adults (CARDIA) study, a prospective observational study of African-Americans and whites aged 18-30 years at enrollment in 1985-1986. We analyzed the cross-sectional associations between 1) current use of OCs and 2) fasting glucose, fasting insulin, and presence of diabetes using generalized estimating equations to adjust for repeated measures. We also examined the effect of current use of OCs on incident diabetes at year 10 of the study. RESULTS: In unadjusted analyses, current use was associated with lower fasting glucose levels [-3.1 mg/dl, 95% CI (-3.7, -2.5)] and reduction in the odds of diabetes [odds ratio 0.56 (0.32, 0.97)], but not lower fasting insulin levels [-0.01 microU/ml (-0.03, 0.02)], compared with nonuse in both African-American and white women. After adjustment for covariates, current use of OCs was still associated with lower fasting glucose levels [-1.8 mg/dl (-2.4, -1.3)] and lower odds of diabetes [odds ratio 0.56 (0.33, 0.95)], although the associations were attenuated. After adjustment, current use of OCs was associated with higher insulin levels [0.12 microU/ml (0.006, 0.23)]. No association existed between pattern of use of OCs and incident diabetes at year 10, although the total number of new persons with diabetes at year 10 was small (n = 17). CONCLUSIONS: Current use of OCs is associated with lower glucose levels in young African-American and white women and may be associated with lower odds of diabetes