Influence of Baseline Diastolic Blood Pressure on Effects of Intensive Compared to Standard Blood Pressure Control
Background—In individuals with a low diastolic blood pressure (DBP), potential benefits or risks of intensive systolic blood pressure (SBP) lowering are unclear.
Methods—The Systolic Blood Pressure Intervention Trial was a randomized, controlled trial that compared the effects of intensive (target <120 mm Hg) versus standard (target <140 mm Hg) SBP control in 9361 older adults with high blood pressure at increased risk of cardiovascular disease (CVD). The primary outcome was a composite of CVD events. All-cause death and incident CKD were secondary outcomes. This post-hoc analysis examined whether the effects of the SBP intervention differed by baseline DBP.
Results—Mean baseline SBP and DBP were 139.7 ± 15.6 and 78.1 ± 11.9 mm Hg, respectively. Irrespective of the randomized treatment, baseline DBP had a U-shaped association with the hazard of the primary CVD outcome. However, the effects of the intensive SBP intervention on the primary outcome was not influenced by baseline DBP level (p for interaction 0.83). The primary outcome hazard ratio for intensive versus standard treatment was 0.78 (95% CI 0.57 to 1.07) in the lowest DBP quintile (mean baseline DBP 61 ± 5 mm Hg) and 0.74 (95% CI 0.61 to 0.90) in the upper four DBP quintiles (mean baseline DBP 82 ± 9 mm Hg), with an interaction p-value = 0.78. Results were similar for all-cause death and kidney events.
Conclusions—Low baseline DBP was associated with increased risk of CVD events, but there was no evidence that the benefit of the intensive SBP lowering differed by baseline DBP.
Clinical Trial Registration—URL: https://clinicaltrials.gov Unique Identifier: NCT01206062
- Received July 31, 2017.
- Revision received September 5, 2017.
- Accepted September 21, 2017.