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Type 2 Diabetes Has Adverse Effects on Memory and Learning Abilities in Older Adults

Jul 17, 2015

Scores of the diabetes patients decreased by an additional 12 percent during the two-year period…

Type 2 diabetes is known to put individuals at risk for numerous health complications. Now a study led by researchers at Beth Israel Deaconess Medical Center (BIDMC) sheds new light on the often overlooked toll that diabetes can take on brain health.

The researchers 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.

“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, MD, PhD, of the Department of Neurology at BIDMC and Associate Professor of Neurology at Harvard Medical School. “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 their conditions.

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 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, 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. Her work showed that the brain’s frontal and temporal regions – which are responsible for vital functions such as decision-making, language, verbal memory and complex tasks – are at greatest risk. This new study suggests that early changes in perfusion, or blood flow, may lead to these 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.”

Beth Israel Deaconess Medical Center news release. Chen-Chih Chung, MD. Inflammation-associated declines in cerebral vasoreactivity and cognition in type 2 diabetes. Neurology. Published online before print July 8, 2015, doi: 10.1212/WNL.0000000000001820.