Having type 2 diabetes is associated with a range of worse health outcomes, including a higher risk for heart disease, kidney disease, and vision impairment. But one outcome that’s particularly concerning to many people is dementia, or cognitive impairment.
Two new studies shed light on how type 2 diabetes increases the risk of dementia, and how one of the most common drugs for type 2, metformin, may help reduce this risk.
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Type 2 diabetes tied to vascular dementia
In the first study, presented online at the annual meeting of the European Association for the Study of Diabetes, researchers at the University of Glasgow in Scotland looked at health data from over 370,000 people with type 2 diabetes over an average of 7 years. As noted in an article at McKnight’s Long-Term Care News, compared with a control group that don’t have type 2 diabetes, those with diabetes were 36% more likely to be diagnosed with vascular dementia during the study period. Vascular dementia is cognitive impairment associated with reduced blood flow to your brain.
What’s more, people with type 2 were 9% more likely to have other forms of dementia than those without diabetes. But they weren’t any more likely to have Alzheimer’s disease, in particular. Alzheimer’s disease is a degenerative brain disease that causes dementia. This finding is in tension with certain other studies that have found a link between type 2 and a high risk of Alzheimer’s disease.
The researchers also looked at what effect blood glucose control had on the risk of dementia. They found that compared with participants with type 2 who had good glucose control (HbA1c below 7.0%), those with poor glucose control (HbA1c of 9.1% or higher) were almost twice as likely to develop vascular dementia.
These results suggest that lifestyle interventions to reduce cardiovascular risk factors, as well as good blood glucose control, are essential to help prevent vascular dementia in people with type 2 diabetes. But they don’t definitively show a cause-and-effect relationship between better glucose control and a lower dementia risk.
Metformin tied to slower cognitive decline
Another study, though, offers a bright spot in the link between type 2 diabetes and dementia. Published in the journal Diabetes Care, it looked at over 1,000 people ages 70 to 90 without dementia at the beginning of the study who didn’t live in any type of care facility.
Researchers put participants through neuropsychological testing every two years to assess cognitive function. Over an average follow-up period of about six years, participants with type 2 diabetes who took metformin experienced a slower rate of cognitive decline than those who didn’t take metformin — despite the two groups being otherwise similar. And when it came to cognitive decline that was severe enough to qualify as dementia, the difference was stark. Those who didn’t take metformin were 5.29 times as likely to develop dementia.
The researchers noted that although the number of people in each group in the study was fairly small (67 who took metformin and 56 who didn’t), the results suggest a clear benefit from metformin in slowing cognitive decline and warding off dementia. But a larger, randomized controlled study — in which some people are randomly assigned to take metformin, while others take another drug for glucose control — is needed to definitively conclude that metformin has a protective effect against cognitive decline.
The researchers note that they are planning just such a study, which will examine how effectively metformin reduces the rate of cognitive decline in people with type 2 over a period ofthree3 years. They intend to focus on participants who are deemed to be at high risk for developing dementia, based on factors like their age and health history.
Want to learn more about maintaining cognitive health with diabetes? Read “Nine Tips to Keep Your Memory With Diabetes,” “Keeping Your Brain Strong With Diabetes” and “Memory Fitness: How to Get It, How to Keep It.”