Being physically active has been linked to a litany of health benefits, often related to preventing heart problems.

Might exercising regularly have a similar effect on the brain?

THIS STUDY analyzed data on 876 older adults (average age, 78) who were participating in a long-term study on cardiovascular health. Periodic assessments included brain scans; a variety of standardized neurological and cognitive tests; and evaluations of physical activity, including time and energy expended on such activities as swimming, hiking, biking, racket sports, gardening, golfing, dancing, walking, calisthenics and aerobics.

People who regularly generated the greatest energy output, regardless of the type of physical activity, had larger brain size, or gray matter volume — especially in areas that affect memory and cognition — than those who were less active. The researchers estimated that this correlated to as much as a 50 percent reduction in risk for the dementia of Alzheimer’s disease.

WHO MAY BE AFFECTED? Older adults. About 5.3 million Americans — the vast majority of them older than 65 and two-thirds of them women — have Alzheimer’s disease. No cure has been found for the progressive brain disorder, which robs people of their memory and thinking abilities along with their ability to live independently. The brain shrinks dramatically in people with Alzheimer’s, prompting research into whether maintaining brain size may help prevent development or progression of Alzheimer’s and other dementias.

CAVEATS Some of the data came from the participants’ responses on questionnaires. Factors not accounted for also may have affected brain size.

FIND THIS STUDY Online in the Journal of Alzheimer’s Disease (j-alz.com; click on “Contents,” then “All Issues, ” then go to “Looking for an article?” to search for “longitudinal relationships.”)

LEARN MORE ABOUT Alzheimer’s disease at nia.nih.gov/alzheimers. Learn about brain health at alz.org.