Clinical Investigation
Objectively Measured, but Not Self-Reported, Medication Adherence Independently Predicts Event-Free Survival in Patients With Heart Failure

https://doi.org/10.1016/j.cardfail.2007.11.005Get rights and content

Abstract

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).

Conclusion

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.

Section snippets

Study Design

In this prospective study, patients were interviewed at baseline and started medication adherence monitoring with the MEMS. They were followed monthly for 6 months by phone to determine emergency department (ED) visits, hospitalizations, and mortality.

Sample and Setting

Patients enrolled in this study met the following inclusion criteria: (1) diagnosis of chronic HF from either preserved (left ventricular ejection fraction [LVEF] ≥ 40%) or nonpreserved systolic function (LVEF < 40%);25 (2) underwent evaluation of

Patient Characteristics

Of the 301 eligible patients with HF who were approached for the study, 152 patients refused to participate because of the long travel distance, time concerns (e.g., have to take care of other family members), no interest in participating in research, or lack of energy. We recruited 149 patients, but two patients died after recruitment and before completing baseline assessment. In this study, we only included the data for the 134 patients for whom we have full data from the MEMS. MEMS data were

Discussion

In this study, we provide evidence of the important impact of medication adherence on clinical outcomes and identify specific aspects of medication-taking behavior that are important to outcomes. The percentage of prescribed doses taken and percentage of days the correct number of doses were taken, but not percentage of doses taken on schedule, are predictors of health outcomes. This finding is important because it helps clinicians target education to specific aspects of medication-taking

Limitations

There are a number of potential limitations to the use of the MEMS to assess patient adherence. There is no guarantee that patients will take their medication even though they open the bottle or that they will take the correct dose, and in these situations, adherence level would be falsely elevated. Our data, however, demonstrating a strong relationship between adherence and outcomes, suggest that adherence was accurately reflected by the MEMS in this study. Moreover, data from validation

Conclusions

This study had three important findings: 1) Medication adherence is directly and independently related to important patient outcomes in HF; 2) the most important components of medication adherence are taking medications daily and taking the correct doses; and 3) self-reported adherence, at least when assessed using a simple one-item method, is not a reliable predictor of outcomes. The finding provides clinicians and researchers with valuable information on how to educate patients to improve

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  • Cited by (0)

    This study was supported by funding from the Philips Medical-American Association of Critical Care Nurses Outcomes Grant, the National Institute of Health Grant (R01 NR008567), the University of Kentucky General Clinical Research Center (M01RR02602), and the Gill Endowment, University of Kentucky, College of Nursing.

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