And among the more physically active participants who had retained more gray matter a decade out, the chances of developing cognitive impairment were cut in half, the study found.
However, the researchers stressed that the relationship between walking and gray matter volume appears to apply only to people who regularly walk relatively long distances that equal about six to nine miles a week.
Walking more than the six- to nine-mile range, however, did not have cognitive benefit, the study found.
"That's because the size of our brain regions can only be so large," Erickson said, adding that the opposite isn't true. "So with no exercise, there can be significant deterioration and decay with age."
However, he added, "what we often tend to think of as an inevitable component or characteristic of aging -- memory decline and brain decay -- is clearly not inevitable. There's plenty of evidence now, and this study is part of that, that shows that we can retain our brain tissue and retain our memories well into late adulthood by maintaining an active and engaged lifestyle."
Dr. Steven V. Pacia, chief of neurology at Lenox Hill Hospital in New York City, described the study's finding as both "intriguing" and an "undoubtedly positive message to send to the public."
"My first reaction to studies like this is that only in America do we have to prove to people that it's good to walk," he said with a chuckle.
"But it stands to reason that being active as we age is going to have a beneficial effect on the brain, just as being inactive is going to have a negative impact," Pacia noted. "Because the brain lives in the environment of the body."
But there may be a catch. "This is just an observational study," Pacia noted. "And while we may assume that the relationship between the brain and activity is a prevention-of-atrophy issue -- just like it is with muscle and bone -- this study do
All rights reserved