To determine the patterns of concomitant drug use for chronic diseases and examine the risk factors of polypharmacy in older outpatients.
Data were extracted from an anonymized health insurance claims database of a public insurance program for older adults in Tokyo, Japan. We analyzed individuals aged ≥75 years who had visited an outpatient clinic, and were regularly prescribed orally administered drugs for chronic diseases for ≥14 days between May and August 2014. The prescription patterns for 16 main drug types were studied using exploratory factor analysis, and the risk factors of polypharmacy, defined as the concomitant prescription of five or more drugs, were identified using multivariate logistic regression models.
A total of 1 094 199 outpatients were analyzed (mean age 81.8 years, 38.4% men). We identified five prescription patterns that explained almost 40% of all observed variance: edema/heart failure/atrial fibrillation-related drugs, insomnia/anxiety-related drugs, pain-related drugs, lifestyle disease-related drugs and dementia-related drugs. The significant risk factors of polypharmacy included men, octogenarians and nonagenarians, higher number of medical institutions visited, use of physician home visits, and hospitalization during the study period. The main drug types most strongly associated with polypharmacy were analgesics, diuretics and antidiabetics.
Polypharmacy was found to be prevalent in older outpatients aged ≥75 years in Tokyo. These findings might provide useful evidence that can contribute to the development of practical countermeasures against adverse events associated with polypharmacy in clinical practice. Geriatr Gerontol Int 2020; ••: ••-••.

© 2020 Japan Geriatrics Society.