THE INFLUENCE OF BASELINE DIASTOLIC BLOOD PRESSURE ON THE EFFECTS OF INTENSIVE BLOOD PRESSURE LOWERING: RESULTS FROM THE STEP RANDOMIZED TRIAL

Abstract

Objective: The Strategy of Blood Pressure Intervention in the Elderly Hypertensive Patients (STEP) trial reported cardiovascular benefits of intensive systolic blood pressure (SBP) lowering. However, the influence of baseline diastolic blood pressure (DBP) on the effects of intensive SBP lowering on cardiovascular outcomes has not been fully elucidated. Design and method: In this post hoc analysis of the STEP trial, participants were randomly assigned to receive intensive (110 to <130 mmHg) or standard SBP treatment (130 to <150 mmHg) and categorized by baseline DBP into subgroups: <70, 70 - 79, and > = 80 mmHg. The primary outcome was a composite of stroke, acute coronary syndrome, acute decompensated heart failure, coronary revascularization, atrial fibrillation, or death from cardiovascular causes. A competing risk proportional hazards regression model was used in the analysis. We compared results across subgroups stratified by baseline DBP levels by including a multiplicative interaction term between SBP treatment arms and subgroups (treatment arm* subgroup). Results: Of the 8,511 participants, 960, 2,474, and 5,077 had baseline DBP divided in intervals of <70, 70 - 79, and > = 80 mmHg, respectively. A reduction in the primary outcome was observed among those randomized to intensive SBP lowering in each DBP subgroup but was significant only in the subset of participants with baseline DBP > = 80 mmHg (<70 mmHg: adjusted hazard ratio, 0.81 [95% confidence interval, 0.43 - 1.51]; 70 - 79 mmHg: 0.80 [0.55 - 1.15]; > = 80 mmHg: 0.73 [0.54 - 0.97]). There were no significant interactions between SBP treatment and baseline DBP subgroups for the primary and secondary outcomes (all P for interaction >0.05). The sensitivity analyses showed consistent results with the main analysis. Conclusions: Baseline DBP levels did not modify the beneficial effects of intensive SBP lowering on cardiovascular outcomes.