Assessing the Impact of Medication Adherence on Long-Term Cardiovascular Outcomes

BackgroundAlthough guideline-recommended therapies reduce major adverse cardiovascular events (MACE) in patients after myocardial infarction (MI) or those with atherosclerotic disease (ATH), adherence is poor.ObjectivesThe goal of this study was to determine the association between medication adherence levels and long-term MACE in these patients.MethodsWe queried the claims database of a large health insurer for patients hospitalized for MI or with ATH. The primary outcome measure was a composite of all-cause death, MI, stroke, or coronary revascularization. Using proportion of days covered for statins and angiotensin-converting enzyme inhibitors, patients were stratified as fully adherent (≥80%), partially adherent (≥40% to ≤79%), or nonadherent (<40%). Per-patient annual direct medical (ADM) costs were estimated by using unit costs from 2 national files.ResultsData were analyzed for 4,015 post-MI patients and 12,976 patients with ATH. In the post-MI cohort, the fully adherent group had a significantly lower rate of MACE than the nonadherent (18.9% vs. 26.3%; hazard ratio [HR]: 0.73; p = 0.0004) and partially adherent (18.9% vs. 24.7%; HR: 0.81; p = 0.02) groups at 2 years. The fully adherent group had reduced per-patient ADM costs for MI hospitalizations of $369 and $440 compared with the partially adherent and nonadherent groups, respectively. In the ATH cohort, the fully adherent group had a significantly lower rate of MACE than the nonadherent (8.42% vs. 17.17%; HR: 0.56; p < 0.0001) and the partially adherent (8.42% vs. 12.18%; HR: 0.76; p < 0.0001) groups at 2 years. The fully adherent group had reduced per-patient ADM costs for MI hospitalizations of $371 and $907 compared with the partially adherent and nonadherent groups.ConclusionsFull adherence to guideline-recommended therapies was associated with a lower rate of MACE and cost savings, with a threshold effect at >80% adherence in the post-MI population; at least a 40% level of long-term adherence needs to be maintained to continue to accrue benefit. Novel approaches to improve adherence may significantly reduce cardiovascular events.