By Merritt McKinney

NEW YORK (Reuters Health) - Being physically fit may be good for the aging brain, researchers report.

In a new study of older adults, higher levels of physical fitness were associated with improved mental abilities.

The results highlight the importance of staying in shape, according to one of the study authors.

"Fitness training can enhance brain and mental function," Dr. Arthur F. Kramer, of the Beckman Institute at the University of Illinois at Urbana-Champaign, told Reuters Health.

Even moderate physical activity may keep the brain in tip-top shape, according to Kramer.

"By increased fitness we are not talking about going from a sedentary lifestyle to running a marathon but instead to walking a couple of miles a few times a week," he said.

"Older adults can maintain and indeed enhance cognitive and brain function with modest amounts of aerobic exercise," Kramer said.

Several animal studies have shown that aerobic training has a positive effect on the brain. It improves blood flow in the brain, encourages the formation of new neurons and increases the number of connections called synapses that form between neurons.

Whether physical fitness has the same effect in people, however, has been uncertain.

Now, Kramer and his colleagues have found that being in shape does seem to benefit the brain in people. A report on the findings is being published in the early online edition of the journal Proceedings of the National Academy of Sciences.

Kramer and his colleagues performed two sets of experiments involving older adults. In the first study, 41 people who had no signs of dementia underwent an exercise test to evaluate their physical fitness. They also measured brain activity while participants performed a task that required them to pay close attention.

Older adults who had a high level of physical fitness performed better on the activity. What's more, people who were in better shape demonstrated much more activity in parts of the brain that are believed to be involved in attention.

In the second study, participants were randomly assigned to one of two exercise groups. One group participated in stretching and toning activities several days a week, while the other group focused on aerobic activity, such as walking.

At the end of the 6-month program, older adults in the aerobic group improved their cardiovascular health. This improvement in heart health corresponded with a significant improvement on the attention activity. In addition, they experienced an increase in brain activity in areas related to attention.

In contrast, there were no significant changes in people in the stretching and toning group.

SOURCE: Proceedings of the National Academy of Sciences Early Edition, February 16, 2004.

Last Updated: 2004-02-16 17:00:15 -0400 (Reuters Health)