Psychosocial factors associated with medication adherence among older adults with chronic diseases: an ITHBC-informed cross-sectional study

To identify psychosocial factors associated with medication adherence among elderly patients with chronic diseases, guided by the Integrated Theory of Health Behavior Change (ITHBC). A cross-sectional survey was conducted among 1,138 community-dwelling adults aged sixty years or older who were receiving long-term treatment for chronic diseases. A structured questionnaire was administered that incorporated validated instruments including the Adherence to Refills and Medications Scale (ARMS), the Medication Literacy Knowledge-Attitudes-Practices (KAP) Scale, the Beliefs about Medicines Questionnaire (BMQ), the Self-efficacy for Appropriate Medication Use Scale (SEAMS), and the Social Support Rating Scale (SSRS). Descriptive statistics, group comparisons, and binary logistic regression were used to examine the psychosocial factors associated with medication adherence. A total of 1,102 valid responses were obtained, yielding a response rate of 96.84%. Among the participants, 46.64% demonstrated good medication adherence. Guided by the ITHBC framework, psychosocial variables were categorized into intention-, capability-, and context-related domains. Logistic regression analysis showed that higher self-efficacy (OR = 0.874, p < 0.001) and higher medication literacy (OR = 0.980, p = 0.020) were associated with lower odds of poor medication adherence, whereas stronger medication concern beliefs (OR = 1.128, p = 0.008) and a history of adverse drug reactions (OR = 0.596, p = 0.035) were associated with poorer adherence. Compared with older adults living with a spouse, those living alone (OR = 3.848, p = 0.003) and those living with children (OR = 3.404, p = 0.004) showed significantly higher odds of poor medication adherence. Medication adherence among older adults with chronic diseases was associated with medication literacy, self-efficacy, social support, and medication beliefs. The ITHBC provided a useful framework for understanding these psychosocial determinants. The findings highlight the importance of multidimensional adherence-support interventions integrating medication education, psychosocial support, and self-management enhancement for older adults with chronic diseases.