Medication adherence among patients with chronic diseases: a survey-based study in pharmacies

Poor adherence to medication leads to worsening of the disease, increased mortality and substantial rise in health care costs. It was our aim to evaluate drug adherence and influencing factors in a cohort of non-selected adult pharmacy customers with various chronic diseases and following long-term treatment. We conducted an 8 week anonymized survey in 152 German pharmacies using the Morisky Medication Adherence Scale to measure medication adherence and a questionnaire comprising questions on multiple factors with potential impact on adherence. Depression was assessed applying the Patient Health Questionnaire-9. In total, 1192 patients were included showing an overall adherence rate of 59.1%. A positive association to drug adherence was found in univariate analysis for non-smoking status, retirement, less disease related complaints, positive belief in drug effects, comprehensive knowledge about the disease and high quality of care by the physician and pharmacist. Multivariate regression analysis revealed that no or minimal depression (odds ratio (OR) 2.3, 95% confidence interval (CI) 1.7-3.0), higher patient age (>63 years) (OR 2.2, CI 1.7-2.8), high perceived importance of the medication (OR 2.0, CI 1.5-2.6), good tolerability of the medication (OR 2.0, CI 1.2-3.5) and drug effect as expected or better (OR 1.6, CI 1.1-2.3) were positively correlated with adherence. Suboptimal adherence to medication is common in pharmacy customers with chronic diseases. The determined factors influencing adherence may help to identify patients at risk for nonadherence and support the need of improvement in physicians' communication with patients to achieve adequate adherence rates.