News & Research

Insulin Resistance, Brain Atrophy, and Cognitive Performance in Late Middle-Aged Adults. Diabetes Care, February 2013, pages 443–449

What is the problem and what is known about it so far?

People with diabetes and insulin resistance are at an increased risk of developing dementia and Alzheimer’s disease. Some evidence suggests that problems with insulin signaling in the body, like that seen in diabetes, affects glucose absorption by the brain and leads the brain tissues to waste away.

Why did the researchers do this particular study?

The researchers wanted to study whether insulin resistance reduces the volume of gray matter in regions of the brain that other studies have shown are related to Alzheimer’s disease and if the diminishing amounts of gray matter is a link between Alzheimer’s disease and type 2 diabetes.

Who was studied?

The participants were 372 people in late middle-age (the average age was 57 years) without symptoms of cognitive dysfunction, most of whom did not have diabetes.

How was the study done?

At the start of the study, researchers tested the participants’ insulin resistance and measured the amount of gray matter in their brains using magnetic resonance imaging. Four years later, the researchers tested their insulin resistance and gray matter volume again.

What did the researchers find?

People in the study who had more insulin resistance also had more brain atrophy in areas affected by Alzheimer’s disease. The association was stronger when looking at changes in insulin resistance and gray matter volume over the four-year study—as resistance increased, gray matter volume decreased—solidifying the connection.

What were the limitations of the study?

Only 121 participants were tested at the end of the study, far less than the 372 at the study’s start. Another issue was that very few people in the study had or developed type 2 diabetes, so the researchers can’t compare these results to those of other studies that focused primarily on people with diabetes.

What are the implications of the study?

The findings suggest that insulin resistance, and thus type 2 diabetes, may increase the likelihood that a person develops Alzheimer’s disease by causing damage to the gray matter in certain regions of the brain.

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