Glycated hemoglobin and risk of hypertension in the atherosclerosis risk in communities study

OBJECTIVE - Diabetes and hypertension often co-occur and share risk factors. Hypertension is known to predict diabetes. However, hyperglycemia also may be independently associated with future development of hypertension. We investigated glycated hemoglobin (HbA _1c) as a predictor of incident hypertension. RESEARCH DESIGN AND METHODS - We conducted a prospective analysis of 9,603 middle-aged participants in the Atherosclerosis Risk in Communities Study without hypertension at baseline. Using Cox proportional hazards models, we estimated the association between HbA _1c at baseline and incident hypertension by two definitions 1) self-reported hypertension during a maximum of 18 years of follow-up and 2) measured blood pressure or hypertension medication use at clinic visits for a maximum of 9 years of follow-up. RESULTS - We observed 4,800 self-reported and 1,670 visit-based hypertension cases among those without diagnosed diabetes at baseline. Among those with diagnosed diabetes at baseline, we observed 377 self-reported and 119 visit-based hypertension cases. Higher baseline HbA _1c was associated with an increased risk of hypertension in subjects with and without diabetes. Compared with nondiabetic adults with HbA _1c <5.7%, HbA _1c in the prediabetic range (5.7-6.4%) was independently associated with incident self-reported hypertension (hazard ratio 1.14 [95% CI 1.06-1.23]) and visit-detected hypertension (1.17 [1.03-1.33]). CONCLUSIONS - We observed that individuals with elevated HbA _1c, even without a prior diabetes diagnosis, are at increased risk of hypertension. HbA _1c is a known predictor of incident heart disease and stroke. Our results suggest that the association of HbA _1c with cardiovascular risk may be partially mediated by the development of hypertension.