As the world's population ages, experts predict that a large number of people will experience one devastating effect of old age - dementia. But new studies reveal that regular walking, just a few hours a week, can have a significant effect on protecting the brain from dementia.
Several studies have shown that moderate exercise like walking has many health benefits, such as lowering the risk of heart disease and diabetes. Now, two new studies of older men and women show that regular walking is good not just for the body, but also for the brain. "Better memory, learning, and attention may be achieved by walking as little as two to three hours per week," says physician Jennifer Weuve of the Harvard School of Public Health in Boston. She and her colleagues tracked the exercise habits of nearly 19,000 women over a period of eight to 15 years. When the women reached age 70 or older, the researchers tested the women's cognitive abilities - their memory, learning, and attention - over a two-year period.
Dr. Weuve says walking helped the women maintain these mental functions, and the more they walked, the better they performed on cognition tests.
"Women who performed a moderate amount of activity, on the order of walking two to three hours at an easy pace every week, performed significantly better on these tests of cognition than women who walked less than one hour per week," she said. "More cognitive benefits may be associated with more activity, and the strongest associations that we saw were associated with activity on the order of walking six or more hours per week."
The results, which appear in the Journal of the American Medical Association, show that women who walked the most had a 20 percent lower risk of cognitive impairment than women who walked the least, regardless of age, education, health habits and overall health status.
A companion study of 2,200 elderly men came to a similar conclusion. That work focused on distance walked rather than amount of time spent walking. Researchers in Virginia and Hawaii found that men who walked the least - less than half a kilometer a day - experienced nearly twice the risk of dementia than those who walked more than three kilometers daily.
These are not the first studies to show that activity helps stave off mental decline in the elderly, but as Dr. Weuve notes, they point out that the activity does not have to be very strenuous.
"They need not be super athletes," she says. "Walking appears to be sufficient to gain these cognitive benefits."
The Harvard physician says some researchers suspect that walking may help the brain by encouraging the growth and survival of brain cells.