Diabetes can lead to a variety of complications, including kidney disease, foot amputations, and eye problems. Even the brain can be affected by diabetes.
Diabetes is associated with memory loss, depression, and other forms of cognitive impairment (problems with memory, language, and other mental functions) in older individuals.
Vera Novak, M.D., Ph.D., of Beth Israel Deaconess Medical Center, and colleagues have worked for the past five years looking at how diabetes affects the cognitive health of older people.
According to Dr. Novak, her past research showed that diabetes patients lose many more neurons than those without the disease. "In fact," she says, "at the age of 65, the average person's brain shrinks about one percent a year, but in a diabetic patient, brain volume can be lowered by as much as 15 percent."
In people with diabetes, the blood vessels can become inflamed. Dr. Novak and colleagues wanted to see if this inflammation was changing the blood flow so as to affect the brain of diabetes patients.
They found that two molecules are responsible for inflammation in the brain, which then affects the blood vessels, ultimately leading to the loss of brain tissue. More specifically, the brain tissue that is most affect is in the frontal and temporal lobes - where the abilities of decision-making, language, verbal memory, and complex tasks are stored.
The researchers came to these findings by comparing older diabetes patients to those without the disease. Of a total 147 participants, 71 were type 2 diabetes patients who had been taking medications for at least five years. The rest of the participants did not have diabetes. The average age of participants was 65 years.
Participants went through a series of tests that measured cognitive ability, balance, blood pressure, and blood sugar. The researchers also collected serum samples to measure certain molecules and other signs of inflammation. Blood flow was measured using magnetic resonance imaging (MRI).
Just as the researchers thought, diabetes patients had more constrained blood vessels, compared to those without diabetes. Diabetes patients also had more loss of brain tissue.
The serum samples showed a strong link between high blood sugar levels and inflammation.
Dr. Novak says the study's results show that chronic high blood sugar and insulin resistance (the telltale signs of diabetes) lead to the release of certain molecules (sVCAM and sICAM) that trigger a series of events which ultimately leads to chronic inflammation. "Once chronic inflammation sets in," explains Dr. Novak, "blood vessels constrict, blood flow is reduced, and brain tissue is damaged."
The two molecules identified in this study could serve as signs of brain damage to come. If these markers can be spotted before brain damage occurs, doctors can take steps to save patients from a variety of cognitive problems, says Dr. Novak.
The study's results also highlight the importance of focusing on the impact diabetes has on the brain. In many cases, the effects of diabetes on the brain have been neglected, says Dr. Novak. These findings show that brain damage among diabetes patients needs to be addressed.
The study appears in the journal Diabetes Care. The research was supported in part by grants from the National Institute of Aging, the National Institute of Diabetes, Digestive and Kidney Diseases, the American Diabetes Association, and the National Center for Research Resources.