Effect of adherence to evidence-based therapy after acute myocardial infarction on all-cause mortality

Abstract

Purpose: Our aim is to estimate the effect of nonadherence to evidence-based cardioprotective medications on all-cause mortality in survivors of acute myocardial infarction (AMI).

Methods: A patient-based retrospective cohort study of 1-year survivors of AMI, members of a health organization in Israel, between 2005 and 2010 was used. Adherence was measured using the proportion-of-days-covered metric and defined as a proportion of days covered ≥80%. In order to determine the independent impact of medication nonadherence on all-cause mortality, Cox proportional hazards models were constructed, adjusting for patient demographic and clinical characteristics.

Results: Of 4655 patients prescribed at least one medication, 864 died during an 8-year follow-up (median 4.5 years). Except for beta-blockers, medication nonadherence was significantly associated with increased adjusted all-cause mortality risk for aspirin [hazard ratio (HR), 1.28; 95% confidence interval (CI), 1.11-1.47], statins (HR, 1.36; 95%CI, 1.18-1.57), and angiotensin-converting enzyme inhibitors/angiotensin receptor blockers only among ischemic heart disease patients with documented heart failure (HR, 1.57; 95%CI, 1.16-2.14). Multidrug-combined therapy exerted incremental survival benefit in a dose-response gradient, exceeding that of single-component treatment. The highest risk of mortality was observed in patients adherent to none of the medications compared with adherents to all medications, with a 38% increase in risk of mortality (HR, 1.38; 95%CI, 1.06-1.80).

Conclusions: Outpatient nonadherence to evidence-based cardioprotective medications in patients with AMI is common, and in the case of aspirin, statin or combined therapy is associated with a marked risk increase in all-cause mortality. Further research is needed to elucidate the role of angiotensin-converting enzyme inhibitor/angiotensin receptor blocker in patient subgroups.

Keywords: medication adherence; mortality; myocardial infarction; pharmacoepidemiology; secondary prevention.