Information about Staying Physically Active and Dementia Risk

All mental functions, including memory, depend on an adequate supply of blood to the brain. Regular exercise promotes better mental functioning by improving cerebral blood flow.

A study from the Journal of the American Geriatrics Society found evidence that exercise protects cognitive ability. Older people who had better aerobic capacity—meaning they were in better physical condition at the beginning of the study—were the most likely to have maintained their level of cognitive functioning six years later. People who were otherwise healthy but had poor aerobic capacity had worse cognitive scores after six years.

Brisk walking is a popular aerobic exercise that has been found to reduce the risk of cognitive decline. In a study published in the Journal of the American Medical Association, researchers asked 2,257 men (ages 71 to 93 and with no signs of dementia) how far they walked each day.

Cognitive assessments performed four to eight years later showed that the men who walked less than a quarter mile a day were nearly twice as likely to have developed dementia as those who walked two miles or more each day.

In the same issue of the journal, a study of 16,466 women found that regular exercise (including walking) reduced the risk of cognitive impairment by 20%, and the more exercise, the better. Women who exercised at least 1.5 hours per week showed less cognitive decline than those who walked 40 minutes or less each week.

In a study reported in the Journal of Gerontology, researchers asked people ages 60 to 79 to either walk or perform stretching and toning exercises for one hour three times per week for three months. A third group did not exercise. The researchers used magnetic resonance imaging (MRI) to measure the participants' brain volumes before and after the exercise programs.

After three months, brain volume had increased significantly among the people who had walked. The biggest increases were in the frontal lobes, the area of higher-order mental activity like memory and attention. Brain volume did not change in the other two groups.

The U.S. Surgeon General and most health organizations recommend at least 30 minutes of moderate activity on most days of the week to maintain good health. For weight loss and weight maintenance, the Institute of Medicine recommends about 60 minutes of activity a day on most days of the week. Some studies suggest that being overweight increases the risk of developing dementia.

Publication Review By: Peter V. Rabins, M.D., M.P.H.

Published: 08 Mar 2011

Last Modified: 28 Jan 2015