Image: woolzian/iStock
Image: woolzian/iStock
Type 2 diabetes is known to put individuals at risk for numerous health complications. Now, a study led by researchers at Harvard Medical School and Beth Israel Deaconess Medical Center sheds new light on the often-overlooked toll that diabetes can take on brain health.
This study found that over a period of just two years, older adults with Type 2 diabetes developed complications in blood flow regulation in the brain that led to impaired memory and other cognitive problems.
The findings appeared online July 8 in Neurology.
Type 2 diabetes affects more than 44 million people worldwide, including 27 percent of adults over age 65. The condition, known as hyperglycemia, develops when glucose builds up in the blood instead of entering the body’s cells to be used as energy.
“In this study, we wanted to determine the associations between inflammation, blood flow in the brain and cognitive performance over a two-year period in older adults with and without Type 2 diabetes,” said senior author Vera Novak, HMS associate professor of neurology at Beth Israel Deaconess. “We hypothesized that inflammation and hyperglycemia are associated with impaired vasoregulation in the brain and that impaired vasoregulation is associated with cognitive decline in cases of Type 2 diabetes.” Vasoregulation refers to the brain’s ability to increase blood flow when needed for mental processing or other cognitive tasks.
The research showed that on tests of learning and memory the scores of the diabetes patients—which started out nine points lower than scores of patients who did not have diabetes—decreased by an additional 12 percent during the two-year period. Scores of the patients who did not have diabetes remained the same throughout the study.
The researchers studied 40 individuals with an average age of 66. Nineteen individuals had Type 2 diabetes, and 21 did not have diabetes. The patients with diabetes had been treated for the disease for an average of 13 years and were taking medication to control the condition.
Study participants underwent a series of MRI scans to examine brain volume and blood flow. They also underwent blood tests to measure inflammation and blood sugar control, and they took cognitive tests to measure thinking and memory skills.
Among participants with diabetes, the ability to regulate blood flow in the brain decreased by 65 percent over two years. However, there was no significant change in blood flow regulation among people who did not have diabetes. (Blood flow measurements were determined through a specialized imaging technique known as arterial spin labeling, which was used in conjunction with standard MRI.)
The study also showed that higher levels of inflammation were associated with greater decreases in blood flow regulation, even among the participants with diabetes who had good control of their blood sugar.
“In patients with diabetes, excess glucose appears to increase vascular inflammation and impair the endothelial cells that line blood vessels,” said Novak. “This, in turn, impedes blood flow regulation and disrupts cognitive function.”
Novak has been studying the effects of diabetes on cognitive health for nearly 10 years. Her earlier research revealed that diabetes can eventually cause the brain to atrophy. This new study suggests that early changes in perfusion, or blood flow, may lead to related later complications.
“There is no cure for diabetes-related cognitive impairment, and our findings showed that even careful glycemic control did not protect brain function in patients with Type 2 diabetes,” said Novak. “This study helps explain the mechanisms underlying long-term effects of diabetes on the brain and has important implications for the growing population of older people with Type 2 diabetes. Novel treatment strategies are urgently needed to prevent the impact of diabetes on the brain and its function.”
The study was supported by grants from the National Institutes of Health (1R01-AG0287601A2; 5R21 DK084463) as well as support from the American Diabetes Association, the Harvard Catalyst | The Harvard Clinical and Translational Science Center and M01-RR-01032 from the National Center for Research Resources.
Adapted from a Beth Israel Deaconess news release.
