Physical activity, even of a moderate degree, may help older people keep their minds sharp, according to a UCSF study.

Scientists tracked 5,925 women 65 and older, who at the start of the research had no cognitive impairments or physical limitations. The women were asked about their physical activity, including recreation and exercise habits, how many city blocks they walked and flights of stairs climbed each day.

The women who were most physically active at the beginning of the study were the least likely to experience a decline in cognitive or mental functions during the next six to eight years, researchers found.

"Exercise seems to be good for the brain/mind as well as for the body,'' lead author Kristine Yaffe, chief of geriatric psychiatry at San Francisco Veterans Affairs Medical Center and UCSF assistant professor of psychiatry, neurology and epidemiology, told Reuters. ``This does not have to be strenuous activity. Even moderate activity is beneficial.''

For every 10 blocks -- approximately one mile -- walked per day, "women had a 13 percent lower odds of cognitive decline," reported Yaffe.

Twenty-four percent of the women who walked the fewest blocks per week developed cognitive decline compared with 17% of the women who walked the most (about 17 miles a week.)

The study is published in the July 23 issue of Archives of Internal Medicine. "

At least 10 percent of persons older than 65 years and 50 percent of those older than 85 years have some form of cognitive impairment, ranging from mild deficits to dementia," according to the study.

The new finding, however, supports the hypothesis that physical activity prevents cognitive decline in older women.

"The exact mechanism of this association is not certain, although it may be related to a healthy lifestyle, a reduction in cardiovascular risk factors, or a direct effect on neurons," wrote Yaffe. "Further research is needed to determine if physical activity programs could prevent clinically significant cognitive impairment and if our findings can be replicated in other populations."