High blood pressure as a risk factor for incident stroke among very old people: a population-based cohort study

Abstract

Introduction: High blood pressure (BP) increases the risk of stroke, but there is limited evidence from studies including very old people. The aim was to investigate risk factors for incident stroke among very old people.

Methods: A prospective population-based cohort study was performed among participants aged at least 85 years in northern Sweden. The 955 participants were tested at their homes. BP was measured manually after 5-min supine rest. Incident stroke data were collected from medical charts guided by hospital registry, death records, and 5-year reassessments. Cox proportional hazards models were used.

Results: The stroke incidence was 33.8/1000 person-years (94 stroke events) during a mean follow-up period of 2.9 years. In a comprehensive multivariate model, atrial fibrillation [hazard ratio 1.85, 95% confidence interval (CI) 1.07-3.19] and higher SBP (hazard ratio 1.19, 95% CI 1.08-1.30 per 10-mmHg increase) were associated with incident stroke overall. However, higher SBP was not associated with incident stroke in participants with SBP less than 140 mmHg (hazard ratio 0.90, 95% CI 0.53-1.53 per 10-mmHg increase). In additional multivariate models, DBP at least 90 mmHg (hazard ratio 2.45, 95% CI 1.47-4.08) and SBP at least 160 mmHg (vs. <140 mmHg; hazard ratio 2.80, 95% CI 1.53-5.14) were associated with incident stroke. The association between BP and incident stroke was not affected by interactions related to sex, dependence in activities of daily living, or cognitive impairment.

Conclusion: High SBP (≥160 mmHg) and DBP (≥90 mmHg) and atrial fibrillation appeared to be risk factors for incident stroke among very old people.

FIGURE 1

Stroke events per 1000 person-years for 10-mmHg SBP intervals, from 80 to 240 mmHg. The intervals are left-closed and right-open. Starting values and numbers of events and participants are presented for each interval.

FIGURE 2

Forest plot comparing univariate and multivariate associations with incident stroke. A logarithmic scale was used. Cox proportional hazards models were used. Multivariate models included atrial fibrillation, previous stroke, congestive heart failure, categorical mini–mental state examination, Mini–Nutritional Assessment score, gait speed, and Geriatric Depression Scale score. The multivariate model of previous stroke and atrial fibrillation also included continuous SBP.