The Impact of Type 2 Diabetes on Brain Health

Type 2 diabetes affects more than 44 million people worldwide, including 27 percent of adults over age 65. The condition develops when glucose builds up in the blood instead of entering the body’s cells to be used as energy, and is known to cause numerous health complications, including vision, kidney and foot problems. But new research from Beth Israel Deaconess Medical Center describes how diabetes can also affect brain health, leading to memory problems and problems carrying out daily activities.

In a study recently published in the journal Neurology, BIDMC neurologist Vera Novak, PhD, discovered that changes in blood vessel activity in patients with diabetes led to cognitive problems.

“Our research found that over a period of just two years, older adults with type 2 diabetes developed complications in blood flow in the brain,” explains Novak.

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.

The researchers found that among the diabetes patients, 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 is used in conjunction with standard MRI.)

The research also 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.

“When doing any task, from memorizing material to moving your fingers, you need to increase blood flow to specific areas of the brain,” Novak explains. When blood sugar levels fluctuate, as they do in people with diabetes, it can damage cells and nerves and trigger inflammation, leading to diminished flexibility in the brain’s blood vessels. “When blood flow is reduced, diabetes patients have fewer resources available to complete these tasks,” she adds.

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 grow smaller. Her work showed that the brain’s frontal and temporal regions — regions 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 blood flow may be what is leading to these later complications.

Novak and her colleagues are continuing to study ways that brain health can be improved for patients with diabetes. One area they are investigating involves using insulin inhaled through the nose or blood pressure medications to help restore normal blood vessel activity.

“Our new study helps explain how diabetes affects the brain and has important implications for the growing population of older individuals with type 2 diabetes,” she says. “Novel treatment strategies are urgently needed to prevent long-term memory problems.”

September 2015