The study is observational—meaning the researchers followed people over time—rather than interventional (say, having some people watch TV and others read a book), which is the gold standard for proving cause and effect. However, the findings do dovetail with what other interventional studies have found, experts say.

Of course there are some uncontrollable factors that affect the brain as you age. For example, the study found that whites were more likely than blacks to maintain their cognitive function with age. And people with hypertension, diabetes, or a gene called apolipoprotein E-e4 were at greater risk of memory loss with aging. (About 25% to 30% of people in the general population carry one or two copies of this gene, which is inherited from one or both parents.)

However, even if you didn’t finish high school or have other factors you can’t change, you can still challenge your brain to preserve mental function, Fiocco says. Interacting with other people through volunteering, work, and other social activities is also an important way to stimulate and challenge the brain, she adds. “Isolation is very dangerous.”

Michelle Carlson, PhD, the associate director of the Center on Aging and Health at Johns Hopkins School of Public Health, in Baltimore, agrees: “It’s about the activity; it’s about being engaged and being out there.”

Carlson is running a study called the Experience Corps Trial, in which older men and women volunteer to teach reading skills to kindergarten through third graders in Baltimore city schools. Using brain-imaging studies, Carlson and her colleagues have shown that after just a few months, people who volunteer show beneficial changes in their brains similar to those that other research teams have seen with exercise.

And just how much exercise is needed? Not much, according to Carlson, who notes that studies have shown benefits for older people who walked a total of 90 minutes a week.

Carlson says that many of her subjects are black and hail from low-income neighborhoods; they are at a greater risk of cognitive decline, she explains. But studies like Fiocco’s suggest that it may be possible to turn “decliners” into “maintainers” by encouraging social and intellectual engagement.

“It really is never too late to start exercising,” says Kirk Erickson, PhD, of the University of Pittsburgh.  “Even people who remain sedentary most of their life can benefit from participating in an exercise regimen.” Walking at a steady pace 3 days a week for 30-45 minutes per day “is enough to actually enhance cognitive function and reverse some of the deficits that may be occurring with old age.”

“The second thing that is  important for keeping a healthy brain as you age is to remain intellectually curious,” he says. “ That is, don’t be afraid to learn new  things.  Pursue things that you find interesting and try to search out new and novel avenues for your mind and brain to work on.”

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