Medication adherence, social support, and event-free survival in patients with heart failure

Objectives: Medication adherence and perceived social support (PSS) are independent predictors of mortality in patients with heart failure (HF). However, the predictive power of the combination of medication adherence and PSS for hospitalization and death has not been investigated in patients with HF. The purpose of the study was to explore the combined influence of medication adherence and PSS for prediction of cardiac event-free survival in patients with HF. Method: A total of 218 HF patients monitored medication adherence for 1-3 months and completed the Multidimensional Perceived Social Support Scale (MPSSS) at baseline. Medication adherence was measured using a valid and objective measure, the Medication Event Monitoring System (MEMS). Patients were followed for up to 3.5 years to collect data about cardiac event-free survival (i.e., cardiac emergency department visits, hospitalizations, and death). To test the association of the combination of medication adherence and PSS with outcomes, the interaction term of medication adherence and PSS was first entered in a Cox regression to predict outcomes. Second, patients were grouped using an evidence-based cutpoint of 88% for medication adherence from the MEMS data and a median score 71 of the MPSSS. Kaplan-Meier and Cox proportional hazards models were used to compare cardiac event-free survival among groups. Result: Medication adherence and PSS were independent predictors of cardiac event-free survival (p = .006 and .021, respectively). Patients with medication nonadherence and lower PSS had a 3.5 times higher risk of cardiac events than those who were adherent and had higher PSS. Conclusion: Medication adherence mediated the relationship between PSS and cardiac event-free survival in this sample. Moreover, medication adherence and social support independently, and in combination, predicted cardiac event-free survival in patients with HF. Interventions to improve clinical outcomes should address medication adherence and social support.