The prevalence and associated factors of nonadherence to antihypertensive medication in secondary healthcare

Purpose Non-adherence (NA) to medication is a major contributor to treatment failure in hypertensive patients. Factors of the ecological model, at family/healthcare professional, service, and system levels, are rarely evaluated as correlates of NA in hypertensive patients. Methods This crossectional study assessed the prevalence of and associated factors of NA to antihypertensive medication among 485 hypertensive patients upon receiving secondary healthcare. The Morisky Green Levine Scale (MGLS) measured the implementation phase of adherence, and the Short Assessment of Health Literacy for Portuguese-speaking Adults (SAHLPA) instrument, health literacy. Multivariate analysis to NA included variables according to the levels of the ecological model. Results Most patients were female (56.3%), white (53.2%), mean age of 62.0 ± 12.6 years, illiterate (61.6%), with low health literacy (70.9%), and low income (65.4%). Uncontrolled BP was frequent (75.2%); 57.1% of patients were nonadherent. In multivariate analysis based on the ecological model, adjusted for micro, meso- and macro-level correlates, NA was associated only with variables of patient-level: low health literacy (OR 1.62, CI 1.07–2.44, p = 0.020), income ≥ two reference wages (OR 0.46, CI 0.22–0.93, p = 0.031), lack of homeownership (OR 1.99, CI 1.13–3.51, p = 0.017), sedentarism (OR 1.78, CI 1.12–2.83, p = 0.014), and complexity of treatment (number of medications taken ≥ two times/day) (OR 1.56, CI 1.01–2.41, p = 0.042). Conclusion In this group of severely hypertensive patients with high cardiovascular risk, only patient-related characteristics were associated with NA. Our findings highlight the need for effective actions to optimize clinical outcomes in similar healthcare programs.