Effectiveness of polypharmacy reduction policy in Japan: nationwide retrospective observational study.

Background Polypharmacy is an important global health issue. In Japan, an amended policy has been implemented since April 2016 to offer incentives that allow claiming a payment of approximately 22.5 US$ per patient to hospitals and clinics that succeed to reduce two or more medications. However, there is no evidence on the nationwide effectiveness of polypharmacy reduction policy. Aim To evaluate the effectiveness of the polypharmacy reduction policy in Japan using nationwide outpatient prescription fee reimbursement claims data in Open Data of the National Database of Health Insurance Claims and Specific Health Checkups of Japan. Method This nationwide retrospective observational study was conducted over 3 years (April 2015 to March 2018). The primary outcome was the polypharmacy reduction ratio calculated by the polypharmacy proportion. Factors associated with policy effectiveness were identified by performing a multiple linear regression analysis using independent variables. Results After implementing the new policy, a 7.3 % polypharmacy reduction ratio was observed, particularly in the elderly (8.2 %). Multiple linear regression analysis revealed that the proportion of elderly residents (aged ≥65 years), number of hospitals per 100,000 residents, and number of clinics per 100,000 residents were statistically significantly associated with this reduction. Conclusion The polypharmacy reduction policy indicated an association with polypharmacy reduction in Japan. The proportion of elderly residents and availability of hospitals and clinics are important factors to enhance the effectiveness of the polypharmacy reduction policy.