These changes are linked with an impaired ability to regulate blood flow in the brain, due in part to inflammation, which is a common component of type 2 diabetes.
Normally, the brain distributes blood as needed to areas of increased neural activity. In diabetic individuals, however, this process becomes impaired.
"We have shown that people with diabetes have abnormal blood flow regulation in the brain, namely impaired ability to increase blood flow and deliver sugar and oxygen to the brain during episodes of increased mental activity," the study's lead author, Dr. Vera Novak of the Harvard Medical School, told The Huffington Post in an email. "Inflammation further alters blood flow regulation in diabetic people and contributes to mental and functional decline."
For the study, the researchers recruited 65 men and women with an average age of 66, half of whom had Type 2 diabetes and half of whom did not. The participants were given a series of memory and cognition tests at the outset of the study and again two years later. They also received brain scans to measure brain volume and blood flow and blood tests to measure inflammation and blood sugar control.
Here are some of the key findings:
After two years, the people with diabetes showed greater declines in gray matter as well as impairments in their ability to regulate blood flow in the brain than the people without.
Blood flow regulation decreased by an average of 65 percent in the participants with diabetes.
Among participants with diabetes, scores on thinking and memory tests decreased by an average of 12 percent, from 46 to 41 points, while test scores of the participants without diabetes stayed the same at 55 percent.
Higher levels of inflammation were correlated with greater difficulties with blood flow regulation.
Those with the highest levels of blood flow regulation impairment at the outset of the study had more difficulties performing daily activities (such as cooking and bathing) after two years.