Factors associated with appropriate knowledge of the indications for prescribed drugs among community-dwelling older patients with polypharmacy

Background: polypharmacy contributes to patients' non-adherence with physicians' prescriptions. Patients' knowledge about the indications for their medicines is one of the factors influencing adherence. Objective: to identify factors associated with appropriate knowledge about the indications for drugs prescribed to older patients with polypharmacy. Methods: in a primary care setting, using home interviews and postal questionnaires, patients aged 60 and over who were taking five or more prescribed drugs simultaneously were asked about their medication. Multiple logistic regression analysis was used to evaluate the association (odds ratio, OR) between medication knowledge and explanatory variables like medication use, sex, age, living situation and educational level. Results: seven hundred and fifty-four participants (mean age 73.2 years) reported an average daily intake of nine (SD 3.0) prescribed drugs. Only 15% of the patients were able to recall the indication for each of their prescribed drugs. Variables that were negatively associated with correct reporting of all indications were taking many prescribed drugs (e.g. a parts per thousand yen10 versus a parts per thousand currency sign5: OR 0.05), age 80 years or over (versus 60-69 years: OR 0.47) and male sex (OR 0.53). Patients living with a partner were more knowledgeable than patients living alone (OR 2.11). We did not find an association with educational level. Conclusion: among older patients using five or more prescribed drugs, there was little understanding of the indications for their drugs, especially among patients taking the highest number of drugs, patients aged 80 or over, and men. Patients living independently with a partner were more knowledgeable than others.