By NICHOLAS BAKALAR
Published: May 23, 2006

Being in poor physical shape may increase the risk for dementia and Alzheimer's disease, a new study has found, and being fit may help delay the onset of the illnesses.

Researchers studied a group of more than 2,200 people over 65 and without dementia from 1994 to 1996, then followed them through October 2003, examining their mental abilities with standard tests and their physical performance with strength and agility tasks.

During the follow-up, 319 people developed dementia. Of them, 221 had Alzheimer's. But the poorer their physical performance at the start of the study, even among people with no signs of dementia, the more likely they were to develop dementia.

The associations held even after adjusting for age, family history of dementia, heart disease and other factors.

A co-author of the study, Dr. Eric Larson of the Group Health Center for Health Studies in Seattle, said the relationship between physical performance and dementia was likely to go both ways.

"The two processes are intimately connected," Dr. Larson said. "People more likely to develop dementia show early signs of physical function decline, and people, especially in old age, will develop decline in physical function as a result of dementia that may be too mild to be detected."

Does this mean that keeping in good physical condition can help prevent or delay the onset of dementia? Yes, Dr. Larson said.

"Maintaining physical fitness is likely to stave off cognitive decline, and maintaining cognitive fitness and activities can also help forestall physical decline," he said. "They are all intimately linked in the aging process, and are influenced by activities in both spheres — because they are not really separate spheres."

The paper appeared yesterday in The Archives of Internal Medicine.