The Prevalence and Characteristics of Older Japanese Adults with Polypharmacy, Based on Regionally Representative Health Insurance Claims Data.

We aimed to clarify the prevalence of polypharmacy among elderly individuals in Japan. We used the data obtained from a large-scale population-based representative database of health insurance claims in a single prefecture in Japan. We examined all of the outpatient and pharmaceutical health insurance claims for National Health Insurance and those for Late-stage Elderly Health Insurance in Nagasaki Prefecture, Japan between April and June 2016. When two or more claim forms were issued for a patient in a single month, we combined the data and identified the number of prescribed drugs for each person. The definition of polypharmacy is a the prescription of six or more drugs per month. We investigated the prevalence of polypharmacy among the beneficiaries of the two insurance systems. Of the 605,406 beneficiaries of the 2 insurance systems, 121,033 (20.0%) patients with polypharmacy were identified. The prevalence of polypharmacy increased with age, especially among the beneficiaries aged > 85 years, with about half of the beneficiaries having polypharmacy status. About half of the people aged > 85 years in the database had polypharmacy status. When a drug is prescribed to an elderly individual, it is necessary to consider the possibility of polypharmacy-related problems.