Metformin use in elderly population with diabetes reduced the risk of dementia in a dose-dependent manner, based on the Korean NHIS-HEALS cohort

Aims: The aim of this study is to investigate the association between metformin usage and dementia in an elderly Korean population. Methods: Participants were divided into five groups: metformin non-users with diabetes mellitus (DM), metformin users with DM (low-, mid-, and high-users), and non-diabetic Individuals. Dementia was defined with primary diagnostic dementia codes according to the 10th edition of the International Classification of Diseases. To compare the incidence rate of dementia among the five groups, Kaplan-Meier estimates and log-rank test were employed. Also, to control the confounding factors, Cox proportional hazards regression models were fitted in a sequential adjustment. Results: The median follow-up was 12.4 years. The overall incidence rate of dementia was 11.3% (8.4% in men and 13.9% in women). Compared with metformin non-users, hazard ratios (95% confidence intervals) of low-, mid-, and high-users and non-diabetic individuals for dementia were 0.97 (0.73–1.28), 0.77 (0.58–1.01), 0.48 (0.35–0.67), and 0.98 (0.84–1.15), respectively, in men, respectively, and 0.90 (0.65–0.98), 0.61 (0.50–0.76), 0.46 (0.36–0.58), and 0.92 (0.81–1.04), respectively, in women, after full adjustment of confounding variables. Conclusions: Metformin use in an elderly population with DM reduced dementia risk in a dose-response manner.