Abstract 11287: The Relationship of All-Cause Mortality to Average On-Treatment Systolic Blood Pressure is Significantly Related to Baseline Systolic Blood Pressure: Implications for Interpretation of the SPRINT Study

Abstract

Background: The SPRINT study demonstrated that targeting systolic blood pressure (SBP) <120 mm Hg was associated with lower cardiovascular event and mortality rates. However, in the LIFE study, a lower achieved SBP (<130 mm Hg) was associated with increased mortality. Mean baseline SBP in SPRINT was 140 and a third of the population had a baseline SBP ≤132, raising the question of whether the lower baseline SBP in SPRINT could in part account for these differences. Methods: All-cause mortality in relation to tertiles of on-treatment average SBP achieved was examined in patients with baseline SBP ≤ or > 25 th percentile value of 164 mm Hg during 4.8±0.9 years follow-up in 7998 non-diabetic hypertensive patients with ECG left ventricular hypertrophy randomly assigned to losartan- or atenolol-based treatment. Average on-treatment SBP <142 (lowest tertile) and average SBP 142 to <152 (middle tertile) were compared with average SBP ≥152 (highest tertile and reference group). Results: In the overall population, there was a highly significant interaction between baseline SBP ≤164 and average on-treatment SBP <142 in Cox analysis (χ 2 =15.48, p<0.001). Among patients with baseline SBP >164, in multivariate Cox analyses adjusting for other potential predictors of mortality and a propensity score for having baseline SBP ≤164, compared with average on-treatment SBP ≥152 an average on-treatment SBP <142 was associated with 32% increased risk of mortality (HR 1.32, 95% CI 1.01-1.65), whereas average SBP of 142 to <152 was associated with 24% lower mortality risk (HR 0.76, 95% CI 0.59-0.98). In contrast, in parallel Cox analyses among patients with baseline SBP ≤164, both an average on-treatment SBP <142 (HR 0.60, 95% CI 0.36-0.99) and average SBP of 142 to <152 (HR 0.51, 95% CI 0.30-0.89) were associated with statistically significant lower risks of mortality compared with average SBP ≥152. Conclusions: All-cause mortality risk associated with achievement of an average SBP <142 is strongly related to baseline SBP level in LIFE. These findings suggest that the lower mortality associated with a lower targeted SBP in SPRINT may not be applicable to patients with considerably higher baseline SBP than SPRINT patients. Further study is necessary to better understand these findings.