May 9, 2001 (Philadelphia) -- Older women who walk even a few miles a week are less likely to experience a decline in mental functions and loss of memories than their peers who never get exercise, report researchers at the annual meeting of the American Academy of Neurology here.
"A little walking is good, and more is even better," says Kristine Yaffe, MD, assistant professor of psychology, neurology, and epidemiology at the University of California, San Francisco and chief of geriatric psychiatry at the San Francisco VA Medical Center
Yaffe and colleagues looked at nearly 6,000 women aged 65 and older who had no signs of impaired mental or physical abilities. The women were tested for mental function at the beginning of the study and again 6-8 years later.
The researchers found that women who walked the most were the least likely to suffer a decline in thought processes and that there was a direct relationship between activity and mental function: As the amount of walking or calories burned per week rose, the risk for loss of mental abilities declined.
"We found that for every extra mile walked per week there was a 13% less chance of [mental] decline," Yaffe says. The most active women in the study walked an average of about 18 miles per week; the least active made it barely half a mile.
To account for possible differences among the study participants that could skew the results, the researchers massaged the data to compensate for the fact that the more active women in the study tended to be younger, had more years of higher education, and had fewer medical problems than inactive women.
The protective effect of exercise held up even when these differences were taken into consideration, Yaffe says.
The study adds to the growing body of evidence that even modest amounts of physical activity can have a visible health benefit. A Harvard University study published in TheJournal of the American Medical Association earlier this year found that women who walk as little as about one hour per week have about half the risk of heart disease as women who don't get off their sofas.
"As the U.S. population is growing older, there is interest now in how we can live so that we improve our functional capacity well into older age, and not just our physical capacity but our mental capacity, and what they're seeing with regard to [mental] function adds to that body of evidence that physical activity may play an important role," says I-Min Lee, MBBS, ScD, associate epidemiologist at Brigham and Women's Hospital and associate professor of medicine at Harvard Medical School in Boston. Lee, who headed the study, commented on the new findings for WebMD.
In a separate study presented at a meeting of the American College of Cardiology, researchers from Cedars Sinai Medical Center in Los Angeles reported that among overweight women undergoing evaluation for possible heart disease, those who rarely or never performed strenuous activities were more likely to have signs of one risk factor for type 2 diabetes and the heart problems related to it. In addition, inactive women also had much higher blood levels of triglycerides, a harmful form of fat, than the active women.
There are several possible explanations for how stretching the legs can also stretch the mind. Studies of mice show that those that run in exercise wheels for a good part of the day develop more nerve connections and healthier nerve cells in the portion of the brain where learning and memory reside than their sedentary littermates.
"We know that physical activity does a number of favorable things in terms of cardiovascular profile and [artery narrowing], less [blood fat], better fitness -- the same things we know are also associated with [mental] function," Yaffe says.
"Some people say it's not exercising by itself," Oscar Lopez, MD, associate professor of neurology and psychiatry at the University of Pittsburgh, tells WebMD. "It's the social activity that goes with exercise. The guy who wakes up in the morning and starts using [an exercise machine] is different from the group where they run and then they have a cup of tea and spend the whole morning together. That type of social support and contact relieves anxiety and could be as important as exercise by itself."
Asked whether exercise might also offer a protective benefit in men, Yaffe says, "I don't see why we wouldn't expect to see the same things in men. However, there is a study that recently came out [in the journal Archives of Neurology] that did not, and I don't know why. They looked at this and found that the association was much more prominent among women."
She speculates that because men tend to have higher risk for heart and blood vessel disease, they may need to exercise more to see the same benefit. Other studies, however, have shown a similar benefit of exercise for both sexes, Yaffe says.