Self-reported medication adherence and cardiovascular events in patients with stable coronary heart disease: the heart and soul study

Abstract

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.

Figure 1

Proportion with subsequent cardiovascular (CV) event (myocardial infarction, stroke, or coronary heart disease death) by the percentage of time in the past month when participants reported taking medications as prescribed (P =.20 for proportion with events across all 4 adherence categories; P=.03 for proportion with events in patients with adherence ≤75% vs >75% of the time).

Figure 2

Proportion surviving without a cardiovascular event (myocardial infarction, stroke or coronary heart disease death) by self-reported medication adherence at baseline, adjusted for age, sex, race, educational level, smoking, diabetes mellitus, hypertension, depressive symptoms, number of cardiovascular medications, use of β-blocker, use of statin, left ventricular ejection fraction, weekly angina, high-density lipoprotein cholesterol level and low-density lipoprotein cholesterol level (P=.006).