July 22, 2008
People with mild Alzheimer's disease may benefit from regular physical activity, a new study finds. Men and women suffering from early Alzheimer's who had higher levels of physical fitness had larger brains compared to those with lower physical fitness levels. In those with Alzheimer's, the brain typically shrinks in size. Larger brains in Alzheimer's patients are associated with better memory.
In one of the first studies to explore the relationship between cardiorespiratory fitness and Alzheimer's disease, medical researchers at the University of Kansas studied 121 people ages 60 and older. Of the group, 57 were in the early stages of Alzheimer's disease, while the rest were free of dementia.
Study participants underwent fitness tests using a treadmill as well as brain scans to measure white matter and gray matter, the essential parts of the brain. Scientists also measured the total volume of their brains. Cardiorespiratory fitness was used as an overall gauge of physical fitness, since people who get regular exercise tend to have higher cardiac and respiratory function.
"People with early Alzheimer's disease who were less physically fit had four times more brain shrinkage when compared to normal older adults than those who were more physically fit, suggesting less brain shrinkage related to the Alzheimer's disease process in those with higher fitness levels," said study author Jeffrey M. Burns, M.D.
The results remained the same regardless of age, gender, severity of dementia, physical activity and frailty. There was no relationship between higher fitness levels and brain changes in the group of people without dementia.
"People with early Alzheimer's disease may be able to preserve their brain function for a longer period of time by exercising regularly and potentially reducing the amount of brain volume lost," Dr. Burns said. "Evidence shows decreasing brain volume is tied to poorer cognitive performance, so preserving more brain volume may translate into better cognitive performance."
Physical fitness is known to benefit the brain in healthy people, helping to mitigate age-related deterioration. And some research suggests that regular physical activity like walking can help to stave off Alzheimer's and other forms of dementia. [See the article, "Want to Keep the Memory Sharp? Try Walking"]
Less is known about the effects of exercise on those who already have Alzheimer's. Studies in animals suggest it may provide benefits, although results in people have been mixed. Scientists propose several reasons why exercise may benefit the brain. Physical fitness has been shown to benefit blood vessels, including those in the brain, and good blood flow to the brain may be critical for maintaining memory and thinking. Physical activity has also been shown to boost the growth of nerve cells in the brain and release various growth factors important for nerve cell maintenance.
The results of this study suggest that exercise does have benefits for the brain in those with early disease. Dr. Burns cautions, however, that the results only observed the standard measure of fitness at one point in time, so further study is needed to explore the links between physical fitness and mental sharpness. The findings were published in Neurology, the medical journal of the American Academy of Neurology.
J. M. Burns, M.D.; B. B. Cronk, B.S., H. S. Anderson, M.D., et al: "Cardiorespiratory Fitness and Brain Atrophy in Early Alzheimer's Disease." Neurology, Volume 71, July 15, 2008, pages 210-216.