Discrepancy between Subjective and Objective Measurements for the Evaluation of Medication Adherence—A Cross-Sectional Study in Patients with Cardiovascular Diseases

Medication adherence is important for the appropriate drug-based treatment in patients with chronic diseases, especially those with cardiovascular diseases (CVDs). The purpose of the present study was to evaluate medication adherence among patients with CVDs using subjective and objective measurements. We enrolled outpatients who visited Fukuoka University Chikushi Hospital from June to December 2022. As a subjective measurement, we used a self-reported questionnaire developed by Ueno et al., which consists of 12 questionnaire items grouped into the following four domains: medication compliance (subjective compliance), collaboration with health care providers (collaboration), willingness to access and use information about medication (willingness), and acceptance to take medication and how taking medication fits a patient's lifestyle (acceptance). The pill counting method was used as an objective measurement to calculate the medication adherence rate; Poor Adherence was defined as a medication adherence rate of <100%. Ninety-four patients were analyzed. No statistically significant differences were observed between the patients in the Good and Poor Adherence groups classified by pill counting, an objective indicator; in the subjective evaluation index Ueno scale scores of subjective compliance, collaboration, willingness, and acceptance domains; and in the total score. A multivariate analysis revealed that obesity (odds ratio, 3.527; 95% confidence interval, 1.387-9.423; <i>p</i> = 0.008) was an independent factor associated with Poor Adherence. In conclusion, we found a discrepancy between subjective and objective measurements for the evaluation of medication adherence. Furthermore, obesity was an independent factor associated with poor medication adherence assessed by the pill counting method; thus, patients with CVD and obesity require a careful follow-up.