https://orcid.org/0000-0003-0499-4527
Abstract
Purpose
Medication non-adherence in dialysis patients is associated with increased mortality and higher healthcare costs. We assessed whether medication adherence is influenced by specific psychometric constructs measuring beliefs about the necessity for medication and concerns about them. We also tested whether medication knowledge, health literacy, and illness perceptions influenced this relationship.
Patients and Methods
This study is based on data from a cross-sectional in-person questionnaire, administered to a random sample of all adult dialysis patients at a teaching hospital. The main outcome was self-assessed medication adherence (8-Item Morisky Medication Adherence Scale). The predictors were: concerns about medications and necessity for medication (Beliefs About Medication Questionnaire); health literacy; medication knowledge (Medication Knowledge Evaluation Tool); cognitive, emotional, and comprehensibility Illness perceptions (Brief Illness Perception Questionnaire). Path analysis was performed using structural equations in both covariance and variance-based models.
Results
Necessity for medication increased (standardized path coefficient [β] 0.30 [95% CI 0.05, 0.54]) and concerns about medication decreased (standardized β −0.33 [−0.57, −0.09]) medication adherence, explaining most of the variance in outcome (r2=0.95). Medication knowledge and cognitive illness perceptions had no effects on medication adherence, either directly or indirectly. Higher health literacy, greater illness comprehension, and a more positive emotional view of their illness had medium-to-large sized effects in increasing medication adherence. These were indirect rather and direct effects mediated by decreases in concerns about medications (standardized β respectively −0.40 [−0.63,-0.16], −0.60 [−0.85, −0.34], −0.33 [−0.52, −0.13]).
Conclusion
Interventions that reduce patients’ concerns about their medications are likely to improve adherence, rather than interventions that increase patients’ perceived necessity for medication. Improving patients’ general health literacy and facilitating a better understanding and more positive perception of the illness can probably achieve this. Our study is potentially limited by a lack of generalizability outside of the population and setting in which it was conducted.
Acknowledgments
We would like to acknowledge the input of the Māori Cultural Resource Unit at Counties Manukau Health, Associate Professor Papaarangi Reid from the University of Auckland, and Susan Reid from Health Literacy NZ for their advice regarding this study.
We thank Dr Morisky for permission to use the MMAS-8. Use of the MMAS-8 is protected by United States copyright laws. A license agreement to use the scale is available from: Donald E. Morisky, ScD, ScM, MSPH, Professor, Department of Community Health Sciences, UCLA School of Public Health, 650 Charles E. Young Drive South, Los Angeles, CA 90095-1772, [email protected].
We thank Dr Horne for permission to use the BMQ. Use of the BMQ is protected by United Kingdom copyright laws. A license agreement to use the scale is available from: Rob Horne, Professor of Behavioural Medicine, Practice & Policy, University College London, BMA House, UCL School of Pharmacy Tavistock Square, London, WC1H 9JP, United Kingdom, [email protected].
We thank Dr Broadbent for permission to use the BIPQ. Use of the BIPQ is protected by New Zealand copyright laws. A license agreement to use the scale is available from: Elizabeth Broadbent, Professor, Psychological Medicine, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand, [email protected].
Disclosure
The authors report no conflicts of interest in this work.