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Study Links Diabetes and Cognitive Impairment in Elderly

Diane Fennell

November 25, 2011

Although various complications of diabetes, such as retinopathy (eye disease), neuropathy (nerve damage), and nephropathy (kidney disease), are well known and well researched, the effect diabetes has on the brain has until now received relatively little attention. But recently, a team of investigators from Beth Israel Deaconess Medical Center identified a key mechanism that links diabetes to depression, memory loss, and other types of cognitive impairment in older individuals.

The team, led by Vera Novak, MD, PhD, has been studying the relationship between diabetes and cognitive difficulties for five years. In their previous research, they discovered that people with diabetes had significantly more brain shrinkage than people without diabetes. To test the hypothesis that chronic inflammation related to high blood glucose levels could affect blood flow to the brains of people with diabetes, Novak recruited 147 people with an average age of 65. Seventy-one of the people had Type 2 diabetes and had been taking medicine to control their condition for at least five years, while the other 76 people did not have diabetes and served as the control group.

The participants were given a series of cognitive tests, balance tests, and blood pressure and blood glucose tests and also had blood drawn to check for various markers of systemic inflammation. They additionally underwent MRI testing (in which magnetic fields and radio waves are used to provide detailed images of internal body structures) to measure blood flow to the brain.

As they’d expected, the researchers found that people with diabetes had more blood vessel constriction (narrowing) and a greater decline in brain tissue. They also found that high blood glucose levels were strongly correlated with higher levels of inflammation-causing chemicals called cytokines. The scientists determined that chronic high blood glucose and insulin resistance trigger the release of two specific molecules — sVCAM and sICAM — that set off a chain of events, leading to the chronic inflammation that causes a reduction in blood flow and shrinkage in brain tissue.

“If these markers [sVCAM and sICAM] can be identified before the brain is damaged, we can take steps to try and intervene,” noted Novak, adding that the research presents further incentive for people to take steps to manage their diabetes.

Previous research by scientists from the University of Alberta, in Canada, has identified several factors linked with cognitive deficits in older adults with diabetes, including high blood pressure, a slow gait or poor balance, and self-reported bad health.

To learn more about the study, read the article “Researchers Identify Link Between Diabetes and Cognitive Impairment in Older Adults” or see the study’s abstract in the journal Diabetes Care. And for tips on controlling high blood glucose, see the article “Managing Hyperglycemia.”
