Exercise builds small blood vessels in brain, study says

Exercise builds small blood vessels in brain, study says

By John Fauber, Medicine & Health / Research

Exercise is known to help prevent cognitive decline and maintain the brain as people age, and now researchers think they know one reason why.

People who engaged in long-term, regular exercise had substantially more small blood vessels in their brains and more blood flow than people who performed little exercise over the years, according to a study presented Monday.

"Exercise increases the number of blood vessels in other parts of the body," said lead researcher Feraz Rahman of Jefferson Medical College in Philadelphia. "What we didn't know is that it also affects the brain."

The researchers used magnetic resonance imaging and a new three-dimensional computer reconstruction to make models of small blood vessels and blood flow in the brains of 12 healthy adults ages 59 to 75. None was considered to be cognitively impaired.

The study was presented at the Radiological Society of North America's annual meeting and is expected to be published in the next few months. It was conducted at the University of North Carolina-Chapel Hill.

Half of the volunteers had engaged in aerobic exercise at least three hours a week over the previous 10 years. The other group exercised less than one hour a week.

The models showed that the exercisers had 43 percent more blood vessels with a diameter of 0.4 millimeters to 0.6 millimeters. While an average of about 100 blood vessels of that size was found in the non-exercisers, an average of 143 was found in the exercisers. More importantly, there are thousands of blood vessels in the brain that are smaller than 0.4 millimeters, Rahman said, so it's likely that exercise also increases the number of smaller blood vessels.

Rahman compared the exercise effect with that of the branching system of a tree. While there were similar numbers of larger blood vessels and arteries, the number of smaller vessels branching off from them was reduced.

"Other studies have shown that exercise prevents cognitive decline in the elderly," he said. "The blood vessel and flow differences may be one of the reasons. Aerobic exercise is a vital part of healthy aging."

The growth of new blood vessels, a process known as angiogenesis, is known to occur around the body, including in the brain, as a response to regular exercise, said David Harder, associate dean for research at the Medical College of Wisconsin.

The researchers "have confirmed what we've known using newer technology," he said. "They can actually see and count the blood vessels."

Exercise initiates a complex process that leads to the formation of new blood vessels in the brain, Harder said. When the muscles of the body are used, electrical impulses are sent from the spine through long nerve fibers to the brain.

These electrical signals stimulate cells in the brain known as astrocytes. The astrocytes, in turn, send out a type of fatty acid that causes blood vessels to dilate. The substance, known as EET, also promotes the growth of new blood vessels, he said.

Exercise doesn't make people smarter, he said, but older people who regularly exercise tend to be more alert. And the increased blood flow in the brain that is established as a result of exercise might help maintain cognitive function as people age, said Harder, who also serves as director of the college's Cardiovascular Research Center.

"It probably is beneficial in terms of being able to maintain a normal functioning brain," he said.

For instance, Harder said his lab has been looking at slices of brains from people who died after being diagnosed with Alzheimer's disease. Those brain slices show a lack of density of small blood vessels known as capillaries.

The study also might explain why people who exercise are less likely to have a stroke, said Arvind Ahuja, chairman of neurosurgery at Aurora St. Luke's Medical Center in Milwaukee, Wis.

"Something is happening at the basic micro level," he said. "Exercise induces a lot of changes in the body that you are not aware of."

For instance, exercise prompts the release of substances that help improve blood flow, he said.

But a key question still needs to be resolved: Does exercise not only increase the number of blood vessels and capillaries, but also help maintain cognitive function? asked Vivek Prabhakaran, assistant professor of neuroradiology at the University of Wisconsin-Madison's School of Medicine and Public Health.

Some observational studies suggest that exercise helps people retain their mental ability as they age.

But what is needed is a larger study that measures blood vessels and cognitive performance together.

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