Association between polypharmacy and the risk of requiring long-term care among community-dwelling older residents: A retrospective cohort study.

Background: Polypharmacy has been increasing attention as it is associated with a number of health problems, especially adverse outcomes in older adults. However, there is insufficient evidence regarding the risk of polypharmacy and long-term care. Methods: We analyzed a community-based retrospective cohort of residents of Goto City by combining data from health checkups, prescription information, and long-term care needs certification database. The study sample included residents aged 65-79 years in 2015 who were followed up for 4 years. The number of medications used was categorized as 0, 1-5, 6-9, and ≥10. The outcome was initiation of long-term care. Cox regression models were used to calculate hazard ratios (HRs) with 95% confidence intervals (CIs) adjusted for potential confounders. Results: Among 1083 participants, 58 used long-term care for 4 years. Compared with participants taking no medication, the incidence of long-term care initiation was approximately double in those taking 1-5 medications, four times higher in people taking 6-9 medications, and 13 times higher in people taking ≥10 medications. After adjusting for potential baseline confounders, the number of medications was significantly associated with the initiation of long-term care services (1-5 drugs: adjusted HR 2.38, 95% CI 1.06-5.34; 6-9 drugs: adjusted HR 2.97, 95% CI 1.23-7.15; and ≥10 drugs: adjusted HR 5.54, 95% CI 1.89-16.23). Conclusions: Among community-dwelling residents aged 65-79 years, the risk of requiring long-term care had a dose-response relationship with the number of prescribed medications.