The study is published in the Sept. 22 issue of the Journal of the American Medical Association.

" This is additional evidence that exercise includes health benefits other than just lowering the risk for coronary disease, cancer and other diseases. We now have evidence that regular walking is also associated with benefits that are related to cognitive function later in life," said Robert D. Abbott, Ph.D., professor of biostatistics at the University of Virginia Health System and a co-author of the study.

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

Symptoms may include personality changes, as well as losses in reasoning, orientation, and memory, that interfere with a person's usual activities.

So far, it is not clear why walking seems to protect the aging brain from dementia and Alzheimer's disease.

"If you've been active throughout your life it could have direct relationships with the same kind of healthy risk factors that are often associated with less obesity, diabetes and heart disease," Abbott said. "People who are active tend to adhere to a healthier life-style and a better diet than those who are inactive. All of these factors could be working together in determining overall vitality and how healthy our brain is. There is also the possibility that people who walk are less likely to get diseases later on in life that could lead to dementia versus people who are inactive."

The study was comprised of 2,257 physically-capable, nonsmoking Japanese-American men between the ages of 71 and 93 who were already participating in the Honolulu-Asia Aging Study, launched in the early 1990's as part of the Honolulu Heart Study.

Distance walked per day was assessed from 1991 to 1993. The men were then neurologically assessed for dementia in two follow-up examinations between 1994 and 1999. During follow-up, 158 cases of dementia were identified. After adjusting for age, men who walked less than a quarter mile per day experienced a 1.8 fold excess of dementia compared with men who walked over two miles per day.

"This finding is probably related to a lifetime of behavior," Abbott said. "Nevertheless, we continue to hear reports about the health benefits of walking, especially in terms of lowering the risk of heart disease and cancer. If I were sedentary, regardless of age, the finding that regular walking could have effects on late-life cognition is an additional reason to become more physically active. But I would do it carefully and with the advice of a physician. Also, keep in mind that walking is not a strenuous activity for most people." Abbott notes that the recommendations and findings from this study of men in Hawaii are likely to apply to women as well.

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