The impact of history of hypertension and type 2 diabetes at baseline on the incidence of stroke and stroke mortality

Background and Purpose - Both hypertension and diabetes are strong predictors of stroke, but very few studies have assessed their joint effect on stroke risk. We evaluated prospectively the joint association of history of hypertension and type 2 diabetes on the incidence of stroke and stroke mortality. Methods - We prospectively followed 49 582 Finnish subjects aged 25 to 74 years without a history of stroke and coronary heart disease at baseline. Hazards ratios (HRs) for stroke risk were estimated by the hypertension and diabetes status. Results - During a mean follow-up of 19.1 years, 2978 incident stroke events were recorded, of which 924 were fatal. Age-, sex-, and study year-adjusted HRs of stroke incidence were 1.35 (95% CI, 1.21 to 1.51), 1.98 ( 95% CI, 1.79 to 2.19), 2.54 (95% CI, 1.61 to 4.01), 3.51 (95% CI, 2.40 to 5.14), and 4.50 (95% CI, 3.60 to 5.61), respectively, among subjects with hypertension I (blood pressure 140 to 159/90 to 94 mm Hg) only, with hypertension II (blood pressure >= 160/ 95 mm Hg, or using antihypertensive drugs) only, with diabetes only, with both hypertension I and diabetes, and with both hypertension II and diabetes compared with the subjects without either of the diseases. The corresponding HRs of stroke mortality were 1.47, 2.62, 3.06, 5.59, and 9.27, respectively. Additional adjustments for body mass index, cholesterol, education, smoking, alcohol consumption, and physical activity did not appreciably change these risk estimates. Blood pressure affected the risk of stroke similarly in diabetic and nondiabetic subjects. Conclusions - Hypertension and type 2 diabetes increase stroke risk independently, and their combination increases the risk drastically. A significant proportion of the risk of stroke assumed to be related to hypertension may be attributable to concomitant diabetes.