Lower rates of dementia with metformin?

The 2 minute update looks at a study evaluating metformin in Type 2 diabetes. Does metformin decrease the risk of developing dementia?

This is a huge meta-analysis. It includes 24 cohort studies, with over 3.4 million participants.

All those included had type 2 diabetes. Three studies specifically looked at new onset DM2. Follow up varied widely, but was most commonly about 5 years. Most studies evaluated all-cause dementia. Compared to those who did not take metformin, metformin users were about 24% less likely to develop dementia. Compared to those who took sulfonylureas, those who took metformin were about 12% less likely to develop dementia. Rates were lower in both men and women. There was no difference seen in those with newly diagnosed diabetes.

Other research has demonstrated that dementia rates increase when someone has diabetes for more than 5 years, and they increase more after 10 years, so it’s not surprising that there was no improvement seen for the patients with newly diagnosed diabetes.

Metformin is very cheap, and usually well tolerated. Of course, there may be gastrointestinal side effects, but starting at a low dose and titrating up slowly will usually avoid most adverse effects, or at least make them tolerable. We don’t know if metformin would help prevent dementia in people without diabetes – research asking that question could potentially be game-changing.

Reference: Tang et al. Association of Metformin use with risk of dementia in patients with type 2 diabetes: A systematic review and meta-analysis. Diabetes Obes Metab. 2025 Jan 8; Online ahead of print.