National evaluation of adherence to β-blocker therapy for 1 year after acute myocardial infarction in patients with commercial health insurance

Background: Quality measures of evidence-based medications post-myocardial infarction have focused on prescription at hospital discharge. Yet survival benefits of these medications are best realized with sustained therapy. We sought to examine long-term β-blocker adherence over the first year after myocardial infarction in patients with commercial health insurance and prescription drug benefits. Methods: This multicenter analysis examined health plan records from members of 11 health plans who had myocardial infarction in 2001, survived at least 1 year, and maintained insurance coverage (N = 17 035). The primary outcome measure was adherence to β-blockers (defined as prescription claims covering ≥75% of days) for 360 days post-discharge. We also examined associations with adherence-time from discharge, health plan product (commercial or Medicare + Choice [M + C]), age (35-64 or ≥65), sex, and region. Results: For 360 days after discharge, only 45% of patients were adherent to β-blockers, with the biggest drop in adherence between 30 and 90 days. In a multivariable model, statistically significant predictors of lower adherence were participation in M + C product, residence in the Southeast, and age (driven by young participants in M + C and young females in commercial products). Conclusions: In a population of patients with health insurance and prescription drug coverage, adherence to β-blocker therapy in the first year after myocardial infarction is poor, indicating that factors other than medication cost are important determinants of long-term adherence. Quality improvement initiatives focused on long-term adherence are needed to realize maximal benefit from medical therapy in post-myocardial infarction patients.