Blood pressure control and risk of stroke: a population-based prospective cohort study.

BACKGROUND AND PURPOSE Adequate control of blood pressure (BP) is a cornerstone in stroke prevention. This study explored the risk of stroke in relation to the quality of BP control in a population-based cohort and whether control of hypertension was related to background characteristics of patients. METHODS A total of 27,936 subjects (10,953 men and 16,983 women), 45 to 73 years old, living in Malmö, Sweden participated in the study. Incidence of stroke was followed-up for a mean period of 6 years. Controlled BP was defined as BP <140/90 mm Hg in subjects with pharmacological treatment for hypertension. RESULTS In the whole cohort, 16 648 subjects (60%) had hypertension (BP > or =140/90 mm Hg) and 23% of them received treatment. Among treated hypertensives, 88.2% had BP levels > or =140/90 mm Hg and 49.5% had BP levels >or =160/100 mm Hg. During the follow-up, 137 strokes occurred among treated hypertensive subjects. The crude incidence of stroke was 289/100 000 person-year in controlled hypertensive subjects and 705/100,000 person-year in treated hypertensive subjects with BP >or =140/90 mm Hg. It was estimated that approximately 45% of all strokes among subjects with treatment for hypertension might be attributed to uncontrolled BP. In treated hypertensives, the risk of stroke increased significantly with advancing age, current smoking, high level of diastolic BP, and diabetes. In hypertensive subjects without treatment (n=12 819), incidence of stroke was 363/100,000 person-year. CONCLUSIONS Uncontrolled BP is highly prevalent in patients with pharmacological treatment for hypertension. More than 90% of stroke in this group occurred in those with uncontrolled BP. Adequate hypertension control may prevent a substantial proportion of first-ever stroke among treated hypertensives.