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).