Low Primary Medication Non-adherence Patterns in Japan: A 10-Year Retrospective Analysis

This study analyzed primary medication non-adherence (PMN) patterns in Japan over a decade and explored the influence of various predictive factors within the context of universal healthcare coverage. We conducted a retrospective cohort study using the DeSC Healthcare database, which integrates pharmacy dispensing records with Japanese medical claims data from multiple health insurance systems, providing a representative sample of the Japanese population across all age groups. We analyzed 2,620,639 medical claims with prescription fees from April 2014 to September 2023. PMN was defined as the absence of a pharmacy dispensing record following a documented prescription issuance. The overall PMN proportion was 4.9%, with a modest decline from 5.6% in 2014 to 4.3% in 2023. Subgroup analyses by age group, insurance type, day-of-week, and income patterns showed no substantial variations. This retrospective analysis revealed that Japan maintains low PMN proportions. Health insurers should consider developing notification mechanisms to alert healthcare providers about unfilled prescriptions. Future research should evaluate the impact of electronic prescribing systems.