Background: Medication nonadherence is presumed to be related to poor clinical outcomes including emergency department (ED) visits, rehospitalization and mortality, yet this relationship has not been tested using objective adherence measures in patients with heart failure (HF). Therefore, it is unknown which objective indicators of medication adherence predict clinical outcomes and how self-reported adherence measures compare to objective measures in predicting clinical outcomes. Objective: The purpose of this study was to determine which indicators of medication adherence are predictors of event-free survival in patients with HF.
Methods: A total of 134 patients with HF (70% male, 61 ±12, 61% NYHA III/IV) were enrolled in this 6-month longitudinal predictive study. Medication adherence was measured using an objective measure, the Medication Event Monitoring System (MEMS) and self-reported adherence from the Medical Outcomes Studies Specific Adherence Scale. Four indicators of adherence were assessed by the MEMS:
dose-count, percentage of prescribed doses taken;
dose-days, percentage of days the correct number of doses taken;
dose-time, percentage of doses taken on schedule; and
therapeutic coverage, percentage of time therapeutic drug action maintained.
Events (ED visits, rehospitalization, and mortality) were obtained by patient/family interview and hospital databases.
Results: In Cox regression, three of the four MEMS indicators, dose-count, dose-day, and therapeutic coverage, predicted time to first event before and after controlling age, gender, ejection fraction, NYHA, angiotensin-converting enzyme inhibitor use, and beta-blocker use (
p
= .004, .008, and < .001, respectively). Self-report medication adherence did not predict outcomes (
p
= .402).
Conclusions: The percentage of prescribed doses taken, percentage of days the correct number of doses taken, and overall therapeutic coverage predicted event-free survival. Neither the percentage of doses taken on schedule nor self-reported adherence predicted outcomes. Healthcare providers should assess specific behaviors related to medication taking rather than a global patient self-assessment of patient adherence.
Medication adherence, social support, and event-free survival in patients with heart failure.
