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.
Significant Differences in Global Cognition, Executive Function
In the observational, prospective study, published online in Diabetes Care, Samaras and colleagues identified 1037 community-dwelling people without dementia between the ages of 70 and 90 who were enrolled in the Sydney Memory and Ageing Study in Australia.
Among the participants, 123 (12%) had type 2 diabetes, including 67 who were treated with metformin; 34 as a single medication and 33 in combination with other medications, most commonly sulfonylureas (70%).
Of the 56 patients with diabetes who did not receive metformin, 34 were treated with diet alone, while the remainder were treated with other glucose-lowering medications.
There were no significant baseline differences between the groups in cognitive performance at baseline, after a multivariate adjustment. Their mean age was about 79.
All participants received neuropsychological testing for cognitive function every 2 years, including memory, executive function, attention, speed, and language tests.
In terms of cognitive decline over the 6 years, those treated with metformin had a significantly lower decline in global cognition compared to those with diabetes not taking metformin (P = .032), and the rate of decline of metformin-treated participants was not different compared to those without diabetes.
There was also a slower decline in executive function in those treated versus not treated with metformin (P =