Metformin and Alzheimer’s Disease Risk

To the Editor: In the September issue of the Journal, Jarskog et al. (1) report and Correll et al. (2) discuss a 4-month trial of metformin that concluded “metformin was modestly effective in reducing … risk factors for cardiovascular disease” and “represents a safe … option for patients who are motivated to lose weight.” That study spanned 4 months, but the treatment of cardiovascular risk factors may continue indefinitely. Imfeld et al. (3) reported that long-term metformin use (over 60 prescriptions or more than 7 years) but not use of other antidiabetic medications such as sulfonylureas, thiazolidinediones, or insulin was associated with a small increased risk of developing Alzheimer’s disease (adjusted odds ratio, 1.71).

I would be grateful if Jarskog et al. and Correll et al. would compare the benefit they anticipate from reducing cardiovascular risk factors with metformin in psychiatric, nondiabetic patients to the risk of increased Alzheimer’s disease from metformin.