Factors related to polypharmacy and hyper-polypharmacy for the elderly: A nationwide cohort study using National Health Insurance data in South Korea.

Polypharmacy may cause adverse health outcomes in the elderly. This study examined the prevalence of continuous polypharmacy and hyper-polypharmacy, factors associated with polypharmacy, and the most frequently prescribed medications among older adults in South Korea. This was a retrospective observational study using National Health Insurance claims data. In total, 7,358,953 Korean elderly patients aged 65 years and older were included. Continuous polypharmacy and hyper-polypharmacy were defined as the use of ≥5 and ≥10 medications, respectively, for both ≥90 days and ≥180 days within 1 year. A multivariate logistic regression analysis was conducted with adjustment for general characteristics (sex, age, insurance type), comorbidities (12 diseases, number of comorbidities, and Elixhauser Comorbidity Index [ECI] classification), and healthcare service utilization. Among 7.36 million elderly patients, 47.8% and 36.9% had polypharmacy for ≥90 and ≥180 days, and 11.9% and 7.1% of patients exhibited hyper-polypharmacy for ≥90 and ≥180 days, respectively. Male sex, older age, insurance, comorbidities (cardio-cerebrovascular disease, diabetes mellitus, depressive disorder, dementia, an ECI score of ≥3), and healthcare service utilization were associated with an increased probability of polypharmacy. The therapeutic class with the most prescriptions was drugs for acid-related disorders (ATC A02). The number of outpatient visit days more strongly influenced polypharmacy than hospitalizations and ED visits. This study provides health policymakers with important evidence about the critical need to reduce polypharmacy among older adults.