February 01, 2020

Does the diabetes drug metformin increase my risk of dementia?

Q: I take metformin for my type 2 diabetes. A friend told me that it could increase my risk of dementia. Is that true?

A: This issue is particularly important because metformin (Glumetza, Riomet) is very commonly used by those with type 2 diabetes to lower blood sugar levels — and because people with diabetes may already be at greater risk of dementia.

In terms of dementia risk, the strongest studies suggest that metformin use may actually help protect people with diabetes from dementia. For example, one recent large study involving over 85,000 adults age 50 and older found that taking metformin was associated with an 8% decrease in the risk of dementia, as compared with taking sulfonylureas, another class of diabetic medications that includes the drugs glimepiride (Amaryl), glipizide (Glucotrol) and glyburide.

While it's true that some other studies have claimed that metformin use might be associated with a higher risk of dementia, those studies are scientifically much weaker.

Mayo Clinic experts point out that many of the studies that have explored the relationship between metformin and cognition are observational rather than more-rigorous controlled trials. Mayo Clinic researchers are currently in the beginning stages of a controlled trial to further explore this relationship.

Until more is known, Mayo experts say that metformin is a safe drug that works well for treating diabetes — and for preventing diabetes in some people who are in a prediabetic stage.