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Walking 1 1/2 Hours a Week Can Delay Mental Decline

September 22, 2004|Thomas H. Maugh II | Times Staff Writer

Walking as little as 90 minutes a week can significantly reduce the rate of mental decline in the elderly, delaying the onset of dementia and Alzheimer's disease, according to two large studies reported today, one involving men and the other women.

Researchers had already known that more intense physical activity was beneficial to the brain, but it was not clear that less rigorous exercise such as walking was helpful. The studies in the Journal of the American Medical Assn. show that it is.

Women who walked 1 1/2 hours per week had a 20% lower risk of mental impairment than those who walked less than 40 minutes per week, according to a study of 18,766 elderly women conducted by researchers from the Harvard School of Public Health.

The mental benefits of the exercise were equivalent to being about three years younger, said Harvard epidemiologist Jennifer Weuve, who led the study. Women who walked more had an even lower risk, she said.

In the second study, men who walked less than a quarter of a mile per day had an 80% higher risk of developing dementia than those who walked at least two miles a day, according to a team from the University of Virginia School of Medicine, which surveyed 2,257 Asian American men in Hawaii. Men who walked a quarter of a mile to one mile a day had a 70% higher risk, University of Virginia biostatistician Robert D. Abbott said.

Dementia is a persistent disorder of mental processes due to brain disease.

The new studies join a growing list of those showing benefit from exercise among people over age 70. Previous studies have shown that regular physical activity reduces the risk of heart disease, cancer and diabetes.

So far, it is not clear how walking reduces the risk of mental impairment. "This finding is probably related to a lifetime of [healthy] behavior," which helps keep blood vessels flexible and open, Abbott said.

Experiments in mice have hinted that physical activity reduces the levels of amyloid in the brain. Amyloid is a sticky protein that builds up with Alzheimer's and other mental disorders, eventually killing brain cells.

In a third study in the journal, a team from the Netherlands reported that a combination of exercise and the so-called Mediterranean diet -- rich in fish, olive oil, fruits and vegetables and low in meat and dairy products -- extended life even if it was not adopted until after age 70.

Epidemiologist Kim T.B. Knoops of Wageningen University and her colleagues studied 1,507 men and 832 women, all of them healthy, and found that those who adopted the Mediterranean diet and had at least 30 minutes of physical activity per day were 50% less likely to die during the 12-year study.

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