The first signs of Alzheimer’s disease and other forms of dementia among older people may be physical rather than mental, new research suggests.

The findings are a strong indicator that physical and mental performance among the elderly are interconnected, researcher Eric B. Larson, MD, tells WebMD.

“If we expect the earliest sign of dementia to be subtle changes in cognition, we are probably going to be wrong,” he says.

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The study by Larson and colleagues at the University of Washington and the VA Puget Sound Health Care System included 2,288 older people followed for six years.

All the participants were members of a Seattle-based managed care cooperative, and all were aged 65 or older at study entry. None was diagnosed with dementia or Alzheimer’s disease at enrollment in the trial, based on standardized cognitive testing, which was repeated every two years.

Physical function testing was also conducted -- evaluating for walking, standing balance, hand grip, and the time needed to stand from being seated in a chair repeated five times.

At the beginning of the study, people with lower baseline physical-performance scores also had lower baseline cognitive test scores. During the six years of follow-up, 319 study participants developed dementia, with 221 of these having a diagnosis of Alzheimer’s disease.

Each 1-point decline in physical-performance score was associated with an increased risk for developing dementia -- with 16 points representing the best physical function and 0 representing the worst. People who scored higher than 10 were far less likely to develop dementia than those with scores of 10 or lower.

Gait slowing and poor balance were more common in people later diagnosed with Alzheimer’s or some other dementia. Poor handgrip seemed to be associated with later dementia in people who already showed early signs of mild cognitive decline.

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Can Exercise Delay Alzheimer’s?

The new study, supported by a grant from the National Institute on Aging, is published in the May 22 issue of the Archives of Internal Medicine. In another study published earlier this year, Larson and colleagues concluded that regular exercise may reduce the risk of Alzheimer’s among older adults.

Older people in the earlier study who reported exercising three times a week or more developed Alzheimer’s a third less often during the six-year-old study than people who exercised less.

Larson says an older person who does not exercise and is declining physically should be encouraged to become more physically active.

“Many people just sit down and accept the inevitable, and if you accept the inevitable you will get it,” he says.

Dallas Anderson, PhD, of the National Institute on Aging, agrees that regular exercise is important for the elderly for a host of reasons. But he adds that it is not yet clear if delaying the onset of Alzheimer’s is one of them.

Anderson is program director for studies into the epidemiology of dementia with the Dementias of Aging branch of the NIA.

It has been suggested that regular exercise protects against mental decline by improving blood flow to the brain.

That may be true, Anderson tells WebMD. But it may also be true that older people tend to become less physically active with advancing mental decline. So instead of regular exercise being protective against dementia, it may just be a sign that mental function has not been impaired.

“In a sense the dementia process could be causing people to exercise less,” Anderson says.

He also points out that older people who exercise regularly may have other habits that could help reduce their Alzheimer’s risk.

“They are probably more disciplined,” he says. “They may eat a better diet or be more socially engaged. They may be doing any number of things that seem to be positive.”

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By Salynn Boyles, reviewed by Louise Chang, MD

SOURCES: Wang, L. Archives of Internal Medicine, May 22, 2006; vol. 166: pp 1115-1120. Eric B. Larson, MD, MPH, director, Center for Health Studies, University of Washington, Seattle. Dallas Anderson, PhD, program director for studies in the epidemiology of dementia, Dementias of Aging Branch, National Institute on Aging, National Institutes of Health, Bethesda, Md. WebMD Medical News: "Regular Exercise May Delay Alzheimer's."