According to a joint study between the Group Health Cooperative and the University of Washington, the very first signs of dementia and Alzheimer's disease, may well be physical, rather than mental.
The study led by Eric B. Larson, MD, MPH, director of Group Health Center for Health Studies, followed 2,288 Group Health members age 65 and older for six years.
At the outset none showed any signs of dementia or Alzheimer's disease; they were assessed by the research team every two years, using a variety of tests, for both physical and mental functioning.
After six years it was found that 319 participants had developed dementia, including 221 with Alzheimer's disease.
The researchers say the participants whose physical function was higher at the start of the study were three times less likely to develop dementia than were those whose physical function was lower.
Dr. Larson says they had expected the earliest signs of dementia would be subtle cognitive changes and were surprised to find that physical changes can precede declines in thinking.
The implication he says is that what is considered to be a brain disease may be intimately connected to physical fitness.
The researchers say that they found the first indicators of future dementia appeared to be problems with walking and balance and a weak handgrip may be a later sign of the development of dementia in older people.
Recent research has also found that when people exercised regularly, they were less likely to develop dementia, including Alzheimer's disease but does not clearly explain the association.
This latest study suggests that regular exercise may help stave off dementia by improving and maintaining physical conditioning.
Larson says the results suggest that in aging, there is a close link between the mind and body and that physical and mental performance may go hand in hand, and anything done to improve one is likely to improve the other.
Larson suggests that when people notice that they are starting to decline physically, re-engaging in physical activity may help them to stop or slow this decline and also reduce their risk of early cognitive decline.
A previous study by Dr. Larson has shown that regular exercise reduces the risk of dementia and Alzheimer's disease by up to 40%.
He also notes that it is still possible for people who have physical constraints, even paralysis, to stay mentally alert and cognitively fit and other studies have suggested that staying busy with nonphysical leisure activities and learning new things may also help delay the onset of dementia.
Larson says "healthy body, healthy mind" is probably only part of the story, and other elements might include social support and positive mood.
The study is published in the current edition of the Archives of Internal Medicine.