Walking may keep brain from shrinking in old age

A man leaves the polling booth during the second-round of parliamentary election in Budapest April 25, 2010.

CHICAGO (Reuters) - Walking at least six miles a week may be one thing people can do to keep their brains from shrinking and fight off dementia, U.S. researchers said on Wednesday.

A study of nearly 300 people in Pittsburgh who kept track of how much they walked each week showed that those who walked at least six miles had less age-related brain shrinkage than people who walked less.

"Brain size shrinks in late adulthood, which can cause memory problems. Our results should encourage well-designed trials of physical exercise in older adults as a promising approach for preventing dementia and Alzheimer's disease," said Kirk Erickson of the University of Pittsburgh, whose study appears in the journal Neurology.

Alzheimer's disease, the most common form of dementia, slowly kills off brain cells, and activities like walking have been shown to build brain volume.

Erickson and colleagues tested to see if people who walk a lot might be better positioned to fight off the disease.

They studied 299 volunteers who were free of dementia and who kept track of how much they walked.

Nine years later, scientists took brain scans to measure their brain volume. After four more years, they tested to see if anyone in the study had cognitive impairment or dementia.

They found that people who walked roughly six to nine miles a week halved their risk of developing memory problems.

"Our results are in line with data that aerobic activity induces a host of cellular cascades that could conceivably increase gray matter volume," the team wrote.

They said more studies need to be done on the effects of exercise on dementia, but in the absence of any effective treatments for Alzheimer's, walking may be one thing people can do that may help down the road.

"If regular exercise in midlife could improve brain health and improve thinking and memory in later life, it would be one more reason to make regular exercise in people of all ages a public health imperative," Erickson said.

No current drugs can alter the progression of Alzheimer's, which affects more than 26 million people globally.

(Editing by Stacey Joyce)