The connection between using your brain or losing it to dementia and Alzheimer's is well-known. Now, there's evidence that using your body may protect your brain as well.

What: Elderly people who said they exercised moderately one to five times a week when younger were less likely to have mild cognitive impairment (MCI), according to a study presented this week at the American Academy of Neurology conference in Chicago. Often known as pre-Alzheimer's, MCI is marked by serious short-term memory loss, but without the other symptoms of Alzheimer's disease such as confusion and inability to carry out daily activities. Each year about 15 percent of people with MCI develop Alzheimer's, compared with 1 to 2 percent of all people age 65 and older.

Who: The research was led by Dr. Yonas Endale Geda at the Mayo Clinic in Rochester as part of an ongoing Study of Aging, which follows elderly people in Olmsted County to learn more about mild cognitive impairment and Alzheimer's.

How: Elderly people were randomly chosen and asked to participate in the study. In this research, 868 people ages 70 to 89 were asked to recall their exercise habits when they were between 50 and 65. All were screened, and 128 were found to have MCI; 740 were normal.

The details: Those who said they did moderate exercise such as brisk walking one to five times per week were less likely to have severe memory problems. For example, 20 percent of normal people said they exercised one to two times per week, compared with 13.4 percent of those with MCI. That was after adjusting for risk factors of education, depression, age and gender. There was no apparent link between exercise done in the previous year and a healthy brain, the study found.

Why: Geda said there are only theories on why exercise would make a difference. One possibility, shown in animal studies, is that exercise may increase production of a brain chemical that prevents deterioration of neurons. "Maybe physical exercise increases chemicals that are good to brain cells," he said. A second possibility is that exercise is a marker for a healthful lifestyle that protects the brain as well as the body. "Maybe someone who exercises is watching her diet. Maybe she has very good relationships," Geda said.

Possible flaws: Geda said studies relying on the recall of participants can be imprecise. This one relies on elderly people, some with a condition affecting memory. But he said MCI mostly causes short-term memory loss, not long-term.

Why it matters: This is the latest in a growing body of research linking physical activity and healthy brains. It also indicates a simple lifestyle change may help protect against widely feared diseases of aging.

What's next? More research, such as a long-term study on those who exercise and those who don't, might resolve questions and show whether the same pattern would emerge, Geda said.

Josephine Marcotty • 612-673-7394