The Association between Polypharmacy and Dementia: A Nested Case-Control Study Based on a 12-Year Longitudinal Cohort Database in South Korea

Dementia is a major concern among growing chronic diseases in the aging society and its association with polypharmacy has not been adequately assessed. The objective of this study was to determine the association between polypharmacy and dementia through multiple statistical approaches. We conducted a nested case-control study for newly diagnosed dementia cases using the South Korean National Health Insurance Service sample cohort database (2002-2013, n = 1,025,340). Interactions between polypharmacy (an average use of ≥5 prescription drugs daily) and comorbidities or potentially inappropriate medications (PIMs) were tested. The odds ratios (ORs) for dementia were analyzed according to the presence of comorbidities, PIM uses, the average number of prescribed daily drugs, and significant interactions with polypharmacy using univariate and multiple logistic regression analyses. A higher prevalence of comorbidities, history of PIM use, higher PIM exposure, and higher proportion of polypharmacy were noted among cases than in controls. In the univariate analysis, the OR for dementia increased significantly with the increase in the number of prescribed drugs [1-