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Regular Exercise in Middle Age May Ward Off Alzheimer's Disease

Posted on: Wednesday, 5 October 2005, 12:00 CDT

By Elisabeth Rosenthal

People who exercise in middle age are far less likely to develop Alzheimer's disease and other dementia when they are older, a study published Tuesday indicated.

Doctors have long realized that regular exercise could prevent and control high blood pressure, diabetes and heart disease. But a few recent studies have suggested that exercise can protect against the development of senility, even many years later. In a study published online Tuesday by the journal Lancet Neurology, researchers from Karolinska Institute in Sweden checked for dementia or Alzheimer's disease in a group of nearly 1,500 patients 69 and older, whose exercise habits had been monitored for nearly 35 years.

To their surprise, they discovered 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, when compared with their 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 the Karolinska Institute, who is the study's main author. The finding confirms what has been hinted at by previous smaller, shorter-term studies in animals and humans. "This is important and squares well with what we have come to realize in the past five years," said Dr. Ian Robertson, director of the Trinity College Institute of Neuroscience in Dublin. "It shouldn't be surprising that the brain benefits from exercise like the rest of the body, maybe even more." He said it was the first study he knew of that had shown a specific association between exercise and the prevention of Alzheimer's. But, more generally, he said that other studies had recently suggested that diet and mental activities, as well as physical exercise, could prevent the mental decline associated with aging.

In one, people over 60 who were required to exercise regularly for six months showed improved mental function, changes on brain scans and growth in the white-matter portion of their brain, which deals with higher thought processes. "I know I've changed my life in response to the data, doing aerobic exercise and eating differently," said Robertson, who is 54 and the author of a new book on the topic, "Stay Sharp With the Mind Doctor." The study published Tuesday deals primarily with the beneficial effects of long-term exercise on the brain, and 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, so it was logical that exercise even decades before diagnosis would have an effect.

Robertson suggested that the improved blood circulation induced by exercise might foster an increase in nerve connections, making the brain more resilient and patients less likely to show early signs of brain ailments. But 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 these 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 importantly, when the mice died and they were subjected to autopsy, the brains of the active mice showed far fewer deposits of beta amyloid. Deposits of clumps of this protein are characteristic of Alzheimer's disease, in mice and humans.

The paper Tuesday suggests that the exercise strategy protects humans as well as rodents. In the Swedish study, 1,449 people who had been surveyed about their life habits every five years since 1972 were examined in 1998. At that point, 117 had developed dementia and 76 Alzheimer's.

Source: International Herald Tribune

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