There is a large body of evidence showing that having diabetes can be damaging to your cognitive and brain health. In recent months, we’ve written news items on the link between type 2 diabetes and dementia, as well as how retina scan results are linked to cognitive function in type 1. It’s not all bad news, though — metformin has been found to reduce the risk of dementia in type 2, and following a Mediterranean diet may help improve cognitive performance in people with diabetes.
As we’ve written about before, research has found a clear connection between blood glucose levels and cognitive function — with glucose levels predictive of future cognitive decline as people get older. This has been true even when blood glucose isn’t high enough to qualify for a diabetes diagnosis.
Now, a new study confirms that elevated blood glucose can be harmful to cognitive health across the entire spectrum, from prediabetes to poorly controlled diabetes — with even somewhat elevated levels linked to a higher risk of cognitive decline and vascular dementia.
To get cutting-edge diabetes news, strategies for blood glucose management, nutrition tips, healthy recipes, and more delivered straight to your inbox, sign up for our free newsletter!
Connection stands regardless of age and weight
The latest study, published in the journal Diabetes, Obesity and Metabolism, looked at data from nearly 450,000 people ages 40 to 69 in Britain who took part in the UK Biobank. Participants were assigned to one of three categories based on their A1C (a measure of long-term blood glucose control) and diagnosis information — normal blood glucose, prediabetes or diabetes.
During a follow-up period that lasted an average of four years, the researchers found a striking connection between glucose status and the risk of cognitive decline. People with diabetes were 197% more likely to have vascular dementia and 39% more likely to have cognitive decline than the normal glucose group. But as noted in a news release on the study from University College London, people with prediabetes were also at risk — they were 54% more likely to have vascular dementia and 42% more likely to have cognitive decline. Notably, the risk of cognitive decline was even higher in people with prediabetes than in those with diabetes.
But having diabetes carried particular risks, with a 91% higher risk for all forms of dementia and an 84% higher risk of Alzheimer’s dementia in people with known diabetes. There were also changes in brain volume linked to prediabetes, undiagnosed diabetes, and known diabetes, with some of the most dramatic changes seen in those with undiagnosed diabetes.
The researchers noted that adjusting for taking blood pressure medications reduced the link between one measure of brain volume and glucose status for those with prediabetes and known diabetes, but not undiagnosed diabetes. While this would normally indicate that taking blood pressure drugs increases the risk for unwanted brain volume changes, in this case, the researchers suggested that “in this context, receipt of antihypertensive medication acts as an indicator of longstanding untreated elevated blood pressure and that, therefore, treatment is being instituted too late.” They based this conclusion on a review of other studies on long-term blood pressure control and cognitive changes.
Risk from prediabetes and diabetes, but blood pressure control helps
While this study’s results may seem depressing if you already have diabetes or prediabetes, there are some important lessons for diabetes management. First, it’s likely that good blood glucose control will reduce your risk for cognitive decline and certain forms of dementia. But it’s also important to make sure your blood pressure is well controlled as early as possible, since waiting too long may increase your risk for cognitive problems.
“It is striking that in comparison with normoglycaemic individuals, prediabetes and known diabetes both increase the risk of vascular dementia, cognitive decline and, to a slightly lesser extent, all‐cause dementia and Alzheimer’s dementia]” the researchers wrote. “Therefore, much like the finding of excess cardiovascular disease risks in people with prediabetes, this result prompts consideration of identification and early intervention in such individuals.”
Talk to your doctor if you have any questions about your risk for cognitive decline or dementia, or concerns about whether your blood glucose or blood pressure are being adequately controlled.
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.”