Factors influencing medication adherence among persons with post-acute myocardial infarction

Abstract

The purpose of this cross-sectional, descriptive correlation study was to test a model that explains the influence of financial status, education, social support, symptom severity, barriers, knowledge, depression, and self-efficacy on medication adherence in post-myocardial infarction patients (MI). The conceptual framework was World Health Organization’s multidimensional adherence model (MAM). A cluster sampling using multi-stage process of 348 post-MI patients was recruited from nine regional hospitals of Thailand. All participants responded to a set of nine questionnaires in a structured interview format. Research instruments were the Demographic Characteristics Questionnaire, Modified ENRICHD Social Support Instrument, Cardiovascular Society Classification, Center for Epidemiologic Studies Depression Scale, Barriers to Medication Adherence, Coronary Heart Disease Awareness and Knowledge Questionnaire, Self-efficacy for Appropriate Medication Use Scale, and Morisky’s Self-reported Measure of Medication Adherence. The reliability of instruments were .92, .72, .87, .87, .91 and .65, respectively. A linear structural relationship (LISREL) 8.72 was used to test the hypothesized path model. The study findings revealed that the hypothesized model fit the empirical data and explained 20% of the variance of medication adherence (chi square = 5.87, df = 5, p < .43, Chi-square/df = 0.97, GIF = 0.99, RMSEA = 0.065, SRMR = 0.041, AGFI = 0.97). Depression was the most influential factor affecting medication adherence which it had negative direct effect (-.40, p < .05) and had negative indirect effect on medication adherence through self-efficacy (-.77, p < .05). Self-efficacy and knowledge had positive direct effect on medication adherence (.17 and .05, p < .05, respectively). Barriers had positive direct effect on medication (.10, p < .05) and negative indirect effect on medication adherence through self-efficacy (-.07, p < .05). Symptom severity, financial status, and social support had negative direct effect on medication adherence (-.06, -.05, and -.05, p < .05, respectively). Social support and knowledge had positive indirect effect through self-efficacy (.21 and .08, p < .05, respectively) and had negative indirect effect through depression and self-efficacy (-.27 and -.11, p < .05, respectively). Moreover, education had positive direct effect on medication adherence (.03, p < .05), positive indirect effect through knowledge and self-efficacy (.10, p < .05), and negative indirect effect on medication adherence through depression and self-efficacy (-0.01, p < .05). These findings demonstrated that the highest impact factors influencing medication adherence was depression followed by self-efficacy and barriers, respectively. Therefore, nurse should identify or aware of barriers and depression on medication adherence. Further nursing interventions should promote self-efficacy to enhance medication adherence and improve quality of life among persons with post-acute MI.