Older people taking metformin, the first-line treatment for type 2 diabetes, show significantly lower rates of dementia and cognitive decline compared to those with diabetes not receiving the drug, with the former having dementia rates that are, in fact, similar to people without diabetes, new research shows.

“After controlling for dementia risk factors that might promote cognitive aging, metformin appeared to mitigate the effect of diabetes on cognitive decline in older people,” first author Katherine Samaras, MBBS, PhD, told Medscape Medical News.

The findings are notable considering the increased risk of cognitive decline that is associated with diabetes, said Samaras, leader of the Healthy Ageing Research Theme at the Garvan Institute and an endocrinologist at St Vincent’s Hospital, Sydney, Australia.

“As they age, people living with type 2 diabetes have a staggering 60% risk of developing dementia, a devastating condition that impacts thinking, behavior, the ability to perform everyday tasks, and the ability to maintain independence,” she said in a press release issued by her institute.

And the results are particularly remarkable in that “few prior studies have controlled for multiple dementia risk factors, including the dementia susceptibility gene APOE4,” Samaras emphasized. 

As the front-line drug treatment for type 2 diabetes, metformin has been extensively studied and, with some other research also showing cognitive benefits, “these results are not surprising,” Mark E. Molitch, MD, told Medscape Medical News.

Nevertheless, “this reinforces the idea that metformin should be the first drug used to treat diabetes, and it should be continued if other drugs are added for blood glucose control,” said Molitch, of the Division of Endocrinology, Metabolism & Molecular Medicine, at the Northwestern University Feinberg School of Medicine in Chicago, Illinois

Diabetes Care. Published online September 23, 2020. Abstract