Brain drain. MRI images show areas of gray matter that shrink with age (left) and areas protected by exercise (right).

Fighting Brain Shrinkage

Aging brains, just like aging bodies, are more robust if treated to regular cardiovascular workouts. Human brains start gradually losing tissue after age 30, and this shrinkage is matched by declines in cognitive performance. But it's been known for years that fit older adults do better on mental tests. Now a brain-imaging study has supplied anatomical evidence that exercise can literally prevent the brain from shrinking.

In the study, researchers used a magnetic resonance imaging (MRI) device to determine the three-dimensional structure and density of the brains of 55 adults, aged 56 to 79. All showed the typical drop in tissue density seen in older people, but the decline was significantly less in those who swam, walked, jogged, or cycled at least 20 minutes a day, several days a week, report neuroscientists Arthur Kramer, Stanley Colcombe, and colleagues at the University of Illinois, Urbana-Champaign, in the February Journal of Gerontology: Medical Sciences. Kramer says fitness had a bigger benefit the older subjects were. Although the researchers looked only at the results of aerobic exercise, they say they have evidence that strength training or other exercise may produce similar effects.

The new results are consistent with animal studies, says Carl Cotman, director of the Institute for Brain Aging and Dementia at the University of California, Irvine. Modest, repeated activity can improve learning and memory in rodents. Kramer believes that it is not just increased blood circulation to the brain that provides the benefits. Animal research, he says, shows that exercise produces more neurotrophins, small proteins that are thought to dispose of harmful free radicals and to encourage neurons to grow and connect.

Related sites
Abstract of the paper
Arthur Kramer's home page
Carl Cotman's home page at the Institute for Brain Aging and Dementia