Influence of Baseline Diastolic Blood Pressure on the Effects of Intensive Systolic Blood Pressure Lowering on the Risk of Stroke

Abstract

Background: Guidelines recommend lowering systolic blood pressure below 130 mm Hg, irrespective of previous strokes. However, there is a concern that lowering systolic blood pressure in people with low baseline diastolic blood pressure might increase the risk of stroke. Methods: We conducted a secondary analysis of the Secondary Prevention of Small Subcortical Strokes trial that randomly assigned participants with a history of subcortical strokes to an intensive (<130 mm Hg; N=1519) or standard (130–149 mm Hg; N=1501) systolic targets. We examined the effects of blood pressure intervention on stroke and cardiovascular composite across the range of baseline diastolic blood pressure in spline regression models and tested for interaction of baseline diastolic blood pressure with the intervention on outcomes. Results: Mean baseline systolic and diastolic blood pressures were 143±19 and 78±11 mm Hg, respectively. Within each baseline diastolic blood pressure tertile, the achieved diastolic was lower in the intensive versus standard arm. There were 275 stroke events over 10 889 years of follow-up. Lower baseline diastolic blood pressure was associated with increased risk of stroke in an observational spline regression model. Hazard ratios relating blood pressure intervention with the risk of stroke in the lowest (hazard ratio, 0.78 [95% CI, 0.52–1.16]) and the highest (hazard ratio, 0.80 [95% CI, 0.53–1.21]) baseline diastolic tertiles were similar ( P =0.95). Results were similar for the cardiovascular composite. Conclusions: Intensive systolic control does not appear to increase the risk of stroke in those with low baseline diastolic blood pressure and prior stroke. Registration: URL: https://www.clinicaltrials.gov ; Unique identifier: NCT00059306.