Blood pressure and the risk of developing diabetes in African Americans and Whites: ARIC, CARDIA, and the Framingham Heart Study

OBJECTIVE - We examined the association between high blood pressure and incident type 2 diabetes in African Americans and whites aged 35-54 years at baseline. RESEARCH DESIGN AND METHODS - We combined data from the Atherosclerosis Risk in Communities (ARIC) study, the Coronary Artery Risk Development in Young Adults (CARDIA) study, and the Framingham Heart Study offspring cohort. Overall, 10,893 participants (57% women; 23% African American) were categorized by baseline blood pressure (normal, prehypertension, hypertension) and examined for incident diabetes (median follow-up 8.9 years). RESULTS - Overall, 14.6% of African Americans and 7.9%of whites developed diabetes. Age-adjusted incidence was increasingly higher across increasing blood pressure groups (P values for trend:,0.05 for African American men; <0.001 for other race-sex groups). After adjustment for age, sex, BMI, fasting glucose, HDL cholesterol, and triglycerides, prehypertension or hypertension (compared with normal blood pressure) was associated with greater risks of diabetes in whites (hazard ratio [HR] for prehypertension: 1.32 [95% CI 1.09-1.61]; for hypertension: 1.25 [1.03-1.53]), but not African Americans (HR for prehypertension: 0.86 [0.63-1.17]; for hypertension: 0.92 [0.70-1.21]). HRs for developing diabetes among normotensive, prehypertensive, and hypertensive African Americans versus normotensive whites were: 2.75, 2.28, and 2.36, respectively (P values <0.001). CONCLUSIONS - In African Americans, higher diabetes incidence among hypertensive individuals may be explained by BMI, fasting glucose, triglyceride, and HDL cholesterol. In whites, prehypertension and hypertension are associated with greater risk of diabetes, beyond that explained by other risk factors. African Americans, regardless of blood pressure, have greater risks of developing diabetes than whites.