Medication Adherence is a Mediator of the Relationship Between Ethnicity and Event-Free Survival in Patients With Heart Failure

Background: Rehospitalization rates are higher in African American than Caucasian patients with heart failure (HF). The reasons for the disparity in outcomes between African Americans and Caucasians may relate to differences in medication adherence. To determine whether medication adherence is a mediator of the relationship between ethnicity and event-free survival in patients with HF. Methods and Results: Medication adherence was monitored longitudinally in 135 HF patients using the Medication Event Monitoring System. Events (emergency department visits for HF exacerbation, HF and cardiac rehospitalization, and all-cause mortality) were obtained by interview and hospital data base review. A series of regression models and survival analyses was conducted to determine whether medication adherence mediated the relationship between ethnicity and event-free survival. Event-free survival was significantly worse in African Americans than Caucasians. Ethnicity was a predictor of medication adherence (P = .011). African Americans were 2.57 times more likely to experience an event than Caucasians (P = .026). Ethnicity was not a predictor of event-free survival after entering medication adherence in the model (P = .06). Conclusions: Medication adherence was a mediator of the relationship between ethnicity and event-free survival in this sample. Interventions designed to reduce barriers to medication adherence may decrease the disparity in outcomes.