Research Sugests Exercise May Keep Senility at Bay

By ELISABETH ROSENTHAL International Herald Tribune

People who exercise in middle age are far less likely to develop Alzheimer's disease and other types of dementia when they are older, a new study has found.

Doctors have long realized that regular exercise could prevent and control high blood pressure, diabetes and heart disease. But a few recent studies, including the newest one, have pointed to the more startling finding, that exercise can protect against the development of senility, even many years later.

In a study published last week online by the journal Lancet Neurology, researchers from the Karolinska Institute checked for dementia or Alzheimer's in a group of nearly 1,500 patients 65 and older whose exercise habits have been monitored for nearly 35 years.

To the researchers' surprise, they found that people who engaged in leisure time physical activity at least twice a week as they passed through middle age, had a 50 percent lower chance of developing dementia and a 60 percent lower chance of developing Alzheimer's disease compared with more sedentary colleagues.

"If an individual adopts an active lifestyle in youth and at midlife, this may increase their probability of enjoying both physically and cognitively vital years later in life," said Dr. Miia Kivipelto, of the Aging Research Center of Karolinska Institute in Stockholm and the main author of the study.

Such retrospective studies do not prove cause and effect, and it is possible that people who are predisposed to Alzheimer's exercised less for some reason connected to the disease. But the finding confirms what has recently been hinted at by previous smaller studies in animals and humans.

"This is important and squares well with what we come to realize in the past five years," said Ian H. Robertson, director of the Trinity College Institute of Neurosciences in Dublin. "It shouldn't be surprising that the brain benefits from exercise like the rest of the body, perhaps even more."

Dr. Robertson added that this was the first study he knew of to show a specific link between exercise and preventing Alzheimer's. Indeed, the researchers found that those people who carried a genetic sequence associated with the development of dementia derived the most benefit.

To ensure that the exercise habit was in and of itself protective, rather than just a general marker for a healthier person or healthy habits, the researchers adjusted their study to eliminate other influences like age, sex, education, movement disorders, vascular illness, smoking, and alcohol consumption.

More limited studies have recently suggested that diet and intellectual activity, as well as physical exercise, may prevent the mental decline associated with aging.

In one, people older than 60 who were forced to exercise regularly for six months showed improved mental function, changes on brain scans and growth in the white matter parts of their brains, the area that deals with higher thought processes.

For the Lancet study, 1,449 people who had been surveyed about their habits every five years since 1972 were examined in 1998. At that point, 117 had developed dementia and 76 Alzheimer's.

The announcement last week deals primarily with the benefits of long-term exercise on the brain.

The researchers were not able to specify an exact mechanism. They noted that dementia starts with silent neurological changes, detectable under a microscope years before outward signs appear.

Recent research on mice genetically engineered to develop Alzheimer's hints at a more specific biochemical explanation.

In a study published in April in The Journal of Neuroscience, a group of those mice were given treadmills in their cages, and so the opportunity to run in their "leisure time."

In a series of subsequent intellectual challenges, the running mice proved better able to learn the ins and outs of test mazes, learning escape routes twice as fast as their more sluggish counterparts.

More important, when the mice were autopsied, the brains of the active ones showed far fewer deposits of beta amyloid.

Deposits of clumps of this protein are characteristic of Alzheimer's, in mice and man.