Is Medication Adherence Predictive of Cardiovascular Outcomes and Blood Pressure Control? The Systolic Blood Pressure Intervention Trial (SPRINT)

BACKGROUND: Adherence to study medications is crucial to evaluating treatment effects in clinical trials. To assess whether in the SPRINT trial, adherence and cardiovascular outcomes are associated regardless of intervention assignment. METHODS: This study included 9,361 participants aged ≥50 years, recruited from 102 clinics. Participants were randomized to a Standard Treatment Group (targeted systolic blood pressure [SBP] <140 mm Hg) or an Intensive Treatment Group (targeted SBP <120 mm Hg) and followed for incident cardiovascular events until the study was halted early for benefit. The 8-item Morisky Medication Adherence Scale (MMAS-8) was administered at baseline, and at the 12- and 48-month (or close out) visit. RESULTS: Adjusting for covariates, there was no association between the baseline 8-item MMAS-8 and the likelihood of the primary composite endpoint, any of the secondary endpoints, or blood pressure (BP) control. Low adherence was associated with a higher body mass index, SBP, diastolic BP, and Patient Health Questionnaire, and high adherence was associated with a higher Montreal Cognitive Assessment. There was no difference in the MMAS-8 over time by treatment arm assignment. For the primary outcome (a composite of myocardial infarction, other acute coronary syndromes, stroke, heart failure, or death from cardiovascular causes), baseline odds ratios (95% confidence intervals) for the Low vs. Medium and vs. High; and, for Medium vs. High MMAS-8 were 1.02 (0.82–1.28), 1.07 (0.85–1.34), and 1.05 (0.88–1.250). CONCLUSIONS: In SPRINT, medication adherence as measured using the MMAS-8 was not associated with outcomes or BP control.