Isolated and borderline isolated systolic hypertension relative to long-term risk and type of stroke: a 20-year follow-up of the national health and nutrition survey

Abstract

Background and purpose: Although the short-term risks of stroke and types of stroke associated with isolated systolic hypertension (ISH) and borderline isolated systolic hypertension (BISH) have been described, the long-term effects of these hypertensive conditions, particularly in younger individuals, are unclear. We performed this study to evaluate the long-term risks of stroke, type of stroke, and predictors of stroke associated with ISH and BISH and how this risk compares with that for persons with diastolic hypertension and normotension.

Methods: We used the 20-year follow-up data for 12 344 adults aged 25 to 74 years who participated in the First National Health and Nutrition Examination Survey Follow-Up Study to determine the aforementioned risks. Blood pressure (BP) measurements of the participants were obtained during baseline evaluation. ISH was defined as systolic BP >/=160 mm Hg and diastolic BP <90 mm Hg. BISH was defined as systolic BP between 140 and 159 mm Hg and diastolic BP <90 mm Hg. Diastolic hypertension was defined as a diastolic BP >/=90 mm Hg. Normotension was defined as systolic BP <140 mm Hg and diastolic BP <90 mm Hg. Incidence of stroke overall and incidence of ischemic stroke and intracerebral hemorrhage were determined from a review of hospital records and death certificates. Relative risk (RR) of stroke and stroke type in association with each hypertensive category was determined by Cox proportional hazards analysis after adjustment for potential confounding variables.

Results: Among the 12 344 participants, hypertension was categorized as ISH (n=493), BISH (n=1241), and diastolic hypertension (n=3954). Normotension was observed in 6656 persons. After adjustment for differences in age, sex, education, serum cholesterol level, body mass index, diabetes mellitus, and cigarette smoking, a significantly higher RR for all strokes was observed in participants with ISH (RR, 2.7; 95% CI, 2.0 to 3.4) and BISH (RR, 1.4; 95% CI, 1.1 to 1.8) than those with normotension. The risk was significantly higher for ischemic stroke or intracerebral hemorrhage in persons with ISH and BISH. Among the 1734 persons with either ISH or BISH, the risk of stroke was independently associated with older age, diabetes mellitus, and systolic BP >/=180 mm Hg.

Conclusions: Increased risks for stroke, ischemic stroke, and intracerebral hemorrhage were observed in patients with BISH, similar to those associated with ISH and diastolic hypertension. Future clinical trials are required to evaluate the effect of antihypertensive treatment in younger patients with BISH and ISH.