Diabetes Takes a Toll on the Brain

October 9, 2015

Type 2 diabetes, one of the most common chronic ailments in older Americans, impairs blood flow to the brain and can contribute to memory and thinking problems, even over a two-year period, a new study found. The results add to a growing body of evidence linking diabetes to dementia.

People typically live with diabetes for years when it is treated. Diabetes is a disease in which the body can no longer regulate the amount of sugar in the blood, resulting in high levels of blood sugar. The disease, which often occurs in people who are overweight, is a well-known risk factor for heart disease and circulatory problems. Other studies have shown that diabetes also increases the risk for Alzheimer’s disease and other forms of dementia.

In this new study, researchers found that after just two years, men and women with diabetes had an impaired ability to regulate blood flow in the brain. The defects were linked to lower scores on tests of memory and thinking skills, and people with impaired blood flow were less able to carry out day-to-day activities like bathing and cooking.

“Normal blood flow regulation allows the brain to redistribute blood to areas of the brain that have increased activity while performing certain tasks,” said Dr. Vera Novak of Harvard Medical School, a study author. “People with type 2 diabetes have impaired blood flow regulation. Our results suggest that diabetes and high blood sugar impose a chronic negative effect on cognitive and decision-making skills.”

For the study, published in the journal Neurology, from the American Academy of Neurology, investigators looked at 40 older women and men, average age 66. Nineteen of them had type 2 diabetes, which had been treated for an average of 13 years. The others were free of diabetes. None of the participants had been diagnosed with Alzheimer’s disease or other forms of dementia.

The participants were given brain scans that measured blood flow, along with tests of memory and thinking skills, at the start of the study. The tests were repeated two years later.

The researchers found that those with diabetes had poorer control of blood flow in the brain than those without the disease. Those with diabetes also scored worse after two years on learning and memory tests, while those without the disease scored about the same two years later. Those with diabetes also performed worse on tests that measured daily activities like bathing or preparing meals.

Chemicals in the blood that indicate high levels of inflammation, a recognized risk factor for heart disease and stroke, were also tied to lower scores on memory and thinking tests. Increasingly researchers believe that inflammation may be tied to dementia as well.

The findings underscore the importance of taking steps, like keeping weight down and following a regular exercise regimen, for warding off diabetes – and, potentially, dementia. Dr. Novak said that additional study in larger numbers of people was needed to better understand the relationship between diabetes and brain problems. Further research could lead to tests that detect blood flow problems early, and ways to prevent the onset of dementia.

By ALZnfo.org, The Alzheimer’s Information Site. Reviewed by William J. Netzer, Ph.D., Fisher Center for Alzheimer’s Research Foundation at The Rockefeller University.

Source: Chen-Chih Chung, MD, Daniela Pimentel, MD, Azizah J. Jor’dan, PhD, et al: “Inflammation-associated Decline in Cerebral Vasoreactivity and Cognition in Type 2 Diabetes.” Neurology: Vol 85, pages 1-9, July 8, 2015


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