As people age, many try to stay active to keep their bodies healthy. Now, research shows that what's good for the body might also be good for the mind. In two separate studies, researchers from Harvard and the University of Virginia studied the effects of moderate exercise on the minds of elderly men and women.

What they wanted to know: Can low-intensity exercise such as walking help keep older adults lucid?

What they did: The first study involved a group of 2,257 men from Honolulu who were between 71 and 93 years old when they entered this study between 1991 and 1993. The men were screened for dementia using cognitive tests and interviews with both the participants and their family members. Then, they were asked how much they walked every day and given physical tests measuring how well they could walk. Two subsequent evaluations, which took place between 1994 and 1996, and between 1997 and 1999, measured the men's mental functioning. In the second study, which looked only at women, the researchers contacted participants in the nationwide Nurses' Health Study, which has been following a group of female nurses since 1976. The researchers phoned more than 16,000 women over 70 between 1995 and 2001 and again two years later and gave them six cognitive tests over the phone. For the women they contacted, the researchers got data from the Nurses' Health Study about amount of physical activity each woman did regularly.

What they found: Men who regularly walked a mile or less every day were at higher risk for dementia than men who walked more than two miles a day. The risk was the highest for men who walked less than a quarter of a mile per day; 8.2 percent developed dementia during the six year follow-up versus 4.2 percent from the group that walked more than 2 miles a day. For women, the results were similar. The more physical activity an older woman regularly incorporated into her life, the clearer her thinking as she got older. The researchers estimated that women who had activity equivalent to walking at least one and a half hours had minds that functioned on the same level as women three years younger.

What it means to you: As people advance in age, they can use low intensity physical activity to take care of their brains as well as their hearts. The researchers are not sure why walking and other physical activities ward off declines in mental function, though they guess that it could have something to do with preventing other physical problems that are more closely associated with cognitive decline. For example, the authors of the women's study point out that walking lowers blood pressure and keeps blood flowing to the brain.

Caveats: All of the men used in one study were from Hawaii and were of Japanese descent. That means their results may not apply to the rest of the population both because they are a genetically distinct population and because, living in Hawaii, they can walk most days of the year. People living in places where they can't walk every day may not see the same benefit. The women's study has different problems, primarily that the researchers couldn't tell whether women had less mental decline because they were active or whether it was the other way around—women who were less lucid were less likely to do physical things. In addition, the follow-up period was short, only two years, and many cognitive changes would not be visible by then.

Find out more: The AARP has tips for seniors who want to stay active as well as some articles on the latest trends, such as ChiRunning, which combines Tai Chi moves with running.

Read the articles: Abbott, R.D. et al. "Walking and Dementia in Physically Capable Elderly Men." Journal of the American Medical Association. Sept. 22, 2004, Vol. 292, No. 12, pp. 1447-1453.

Weuve, J. et al. "Physical Activity, Including Walking, and Cognitive Function in Older Women." Journal of the American Medical Association. Sept. 22, 2004, Vol. 292, No. 12, pp. 1454-1461.

Abstract online: Abbott et al: http://jama.ama-assn.org/cgi/content/short/292/12/1447

Weuve et al: http://jama.ama-assn.org/cgi/content/short/292/12/1454