Walking, gardening and generally being physically active after age 65 appears to ward off dementia, including Alzheimer’s disease, new research indicates.

“In later life, active effort with a lot of variety during your leisure time may have a big influence in reducing your chances of getting dementia,” study author Dr. Constantine G. Lyketsos told Reuters Health.

However, physical activity appeared to help only the aging minds of people who weren’t genetically predisposed to develop dementia - suggesting that, in this instance, physical activity may not be strong enough to compensate for that “genetic force,” added Lyketsos, based at the Johns Hopkins Hospital in Baltimore, Maryland.

As he put it, “If your nature is strong in favor of dementia your nurture may not be able to overcome it, but if your nature is less strong, then your nurture may be more influential.”

Despite this, Lyketsos noted that staying active helps more than just the mind, and it’s a good idea for every one 65 and older, regardless of their genetic makeup.

“It is best to keep a variety of activities going, such as a sport, walking, gardening, swimming - with four or more being optimal,” he said.

A growing amount of research suggests that physical activity can keep seniors’ minds in good working order, but some studies have yielded contradictory results.

To investigate further, Lyketsos and his colleagues followed 3,375 men and women aged 65 and older for an average of 5-1/2 years, noting how much activity they engaged in, and whether they developed dementia.

Activities included walking, household chores, yard work, gardening, biking, dancing, aerobics, bowling, swimming and golfing.

Over the course of the study, 480 people developed dementia, the authors report in the American Journal of Epidemiology.

In general, people who were more active appeared to have a lower risk of dementia. However, when the researchers separated people according to whether they carried the e4 version of a gene called APOE, which predisposes carriers to Alzheimer’s disease, they found that physical activity only appeared to fight off dementia in APOE e4 non-carriers.

The more types of activities people engaged in, the less likely they were to develop dementia, suggesting that a variety of activities is particularly protective.

Lyketsos explained that physical activity may help the aging brain by preventing a hardening of the brain arteries, reducing the buildup of plaque in brain tissue, and keeping different parts of the brain active - in line with the “use it or lose it” theory, he said.

SOURCE: American Journal of Epidemiology, April 1, 2005.