Background: Nonadherence to physician treatment recommendations is an increasingly recognized cause of adverse outcomes and increased health care costs, particularly among patients with cardiovascular disease. Whether patient self-report can provide an accurate assessment of medication adherence in outpatients with stable coronary heart disease is unknown.
Methods: We prospectively evaluated the risk of cardiovascular events associated with self-reported medication nonadherence in 1015 outpatients with established coronary heart disease from the Heart and Soul Study. We asked participants a single question: "In the past month, how often did you take your medications as the doctor prescribed?" Nonadherence was defined as taking medications as prescribed 75% of the time or less. Cardiovascular events (coronary heart disease death, myocardial infarction, or stroke) were identified by review of medical records during 3.9 years of follow-up. We used Cox proportional hazards analysis to determine the risk of adverse cardiovascular events associated with self-reported medication nonadherence.
Results: Of the 1015 participants, 83 (8.2%) reported nonadherence to their medications, and 146 (14.4%) developed cardiovascular events. Nonadherent participants were more likely than adherent participants to develop cardiovascular events during 3.9 years of follow-up (22.9% vs 13.8%, P = .03). Self-reported nonadherence remained independently predictive of adverse cardiovascular events after adjusting for baseline cardiac disease severity, traditional risk factors, and depressive symptoms (hazards ratio, 2.3; 95% confidence interval, 1.3-4.3; P = .006).
Conclusions: In outpatients with stable coronary heart disease, self-reported medication nonadherence is associated with a greater than 2-fold increased rate of subsequent cardiovascular events. A single question about medication adherence may be a simple and effective method to identify patients at higher risk for adverse cardiovascular events.