Objectively measured, but not self-reported, medication adherence independently predicts event-free survival in patients with heart failure.
OBJECTIVE
Medication nonadherence is presumed to be related to poor clinical outcomes, yet this relationship rarely has been tested using objective adherence measures in patients with heart failure. Which objective indicators of medication adherence predict clinical outcomes are unknown. The study objective was to determine which indicators of medication adherence are predictors of event-free survival.


METHODS
Patients (N = 134) with heart failure (69% were male, aged 61 +/- 11 years, 61% with New York Heart Association class III/IV heart disease) were enrolled in this 6-month longitudinal study. Adherence was measured using two measures: 1) an objective measure, the Medication Event Monitoring System (MEMS); and 2) self-reported adherence (Medical Outcomes Studies Specific Adherence Scale). Three indicators of adherence were assessed by MEMS: 1) dose-count, percentage of prescribed doses taken; 2) dose-days, percentage of days correct number of doses taken; and 3) dose-time, percentage of doses taken on schedule. Events (emergency department visits, rehospitalization, and mortality) were obtained by patient/family interview and hospital databases.


RESULTS
In Cox regression, two of the three MEMS indicators, dose-count and dose-day, predicted event-free survival before and after controlling for age, gender, ejection fraction, New York Heart Association class, angiotensin-converting enzyme inhibitor use, and beta-blocker use (P = .004, P = .008, and P = .224, respectively). Self-report adherence did not predict outcomes (P = .402).


CONCLUSIONS
Dose-count and dose-day predicted event-free survival. Neither dose-time nor self-reported adherence predicted outcomes. Health care providers should assess specific behaviors related to medication taking rather than a global patient self-assessment of patient adherence.
Wu
Jia-Rong
JR
University of Kentucky, College of Nursing, Lexington, Kentucky 40536-0232, USA.jiarongwu@uky.edu
Moser
Debra K
DK
Chung
Misook L
ML
Lennie
Terry A
TA
D017677:Age Distribution; D000368:Aged; D002317:Cardiovascular Agents / Q000008:administration & dosage*; D018572:Disease-Free Survival; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000188:drug therapy* / Q000401:mortality*; D006801:Humans; D053208:Kaplan-Meier Estimate; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010349:Patient Compliance / Q000706:statistics & numerical data*; D011237:Predictive Value of Tests; D011336:Probability; D011446:Prospective Studies; D018570:Risk Assessment; D012646:Self Administration / Q000706:statistics & numerical data; D012720:Severity of Illness Index; D017678:Sex Distribution; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires; D016019:Survival Analysis
D002317:Cardiovascular Agents