New research shows that physical fitness can actually affect the structure of the human brain, and exercise may be our best friend when it comes to keeping the old noggin tuned up while we age.
We've been told for years that staying fit helps fight off the decline in cognition due to aging, and that's common sense because the brain, after all, is part of the body. But for the first time scientists have literally looked inside the human brain and found that people who exercise regularly maintain a physiological advantage over couch potatoes.
To put it simply, their brains don't shrink as much.
Keeping Your Grays and Whites
The researchers used high-resolution magnetic resonance imaging to study the brains of 55 volunteers between the ages of 56 and 79. They found that those who were physically fit had lost far less of their brain's gray and white matter than those who got very little exercise.
"People who are most fit showed the largest benefit," says psychologist Arthur F. Kramer of the University of Illinois at Urbana-Champaign. "They showed the least amount of reduction in brain volume."
Gray matter is home to the neurons that are so important to learning and memory. White matter is sort of the brain's Internet, with fibers that send signals throughout the brain. Scientists have known for years that these tissues begin to shrink at about the age of 30 in a pattern that closely matches declines in cognitive performances, says Kramer, leader of the research team.
But the new research shows that the decline can be minimized by physical exercise, because the fitter participants had more gray and white matter than those who exercised less.
Furthermore, the areas that showed the most benefit are the same areas associated with mental decline due to aging, such as short-term memory loss.
The researchers found far more gray and white matter in the frontal, temporal and parietal cortexes among the physically fit participants.
That's particularly significant because of the role each of those areas plays in the cognitive processes.
"The frontal areas of the brain have a lot to do with what people call higher-level cognition," Kramer says. That's where we synthesize information, and store data we've just acquired. If that's not up to par, you're likely to forget a phone number that you just looked up.
The temporal lobes consolidate short-term memories and build them into long-term memories. The parietal lobes allow us to navigate.
"People call it spatial cognition, to get around in the world," Kramer says.
All of those areas are associated with mental decline due to aging, and "those seem to be the areas that are most responsive to fitness training," he adds.
The participants were all well educated men and women, ranging from sedentary to very fit athletes. Three-dimensional brain scans were done on each participant, allowing the researchers to measure the density of white and gray matter.
Kramer cautions against drawing too many conclusions from the University of Illinois study, because more research needs to be done.
"This is the first study ever to look at the link between brain structure and fitness," he says.
But it fits neatly with other major studies at the university, also led by Kramer. Another study shows that even people who begin exercising late in life "show pretty dramatic benefits."
Doctor: ‘Get Off the Couch’
But those who start younger reap the greatest rewards, adds Kramer, a physical fitness nut who has even climbed Alaska's Denali (also known as Mount McKinley), the highest peak in North America.
If you want to keep your senses, he says, the evidence is clear: "Get off the couch, no matter how old you are."
"There's no reason not to start if you're older, and there's no reason not to start earlier if you're younger," he says. "We've been doing this kind of work for years, and 20-year-olds always say to me, 'Well, what does it matter? I can always wait until I'm 60.'
"My reply is the effects tend to be larger if you start younger. So if you plan to be around when you're 70, it might be a good idea to start now."
Another study led by Kramer, which will be published in the March issue of Psychological Science, revealed some similar results. It found:
Exercise programs involving both aerobic exercise and strength training produced better results on cognitive abilities than either one alone. That suggests that the old rule of walking 30 minutes a day, three days a week, may not offer as much protection against mental decline as a more vigorous routine.
Older adults benefit more than younger people because age-related declines are more pronounced.
The magnetic imaging study will be published in the February issue of the Journal of Gerontology: Medical Sciences. The studies were funded by the National Institute on Aging and the New York-based Institute for the Study of Aging.
Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.