Walking away from dementia: moderate exercise protects aging minds

Science News, Sept 25, 2004 by B. Harder

Two fresh studies strengthen the case that physical activity protects the aging brain from decline. Walking a couple of miles a day at a moderate pace appears to make a difference.

Past studies have linked both physical and mental inactivity in adulthood with elevated risk of Alzheimer's disease (SN: 3/10/01, p. 148). A regimen of stepped-up physical activity can cause greater blood flow in the brain and stronger performance on mental tests (SN: 2/21/04, p. 115), but whether regular exercise can fend off subsequent cognitive decline has remained a question.

Furthermore, if physical activity indeed guards the brain, the question becomes, How much is required to achieve benefits?

To explore these issues, biostatistician Robert D. Abbott of the University of Virginia in Charlottesville and his colleagues enrolled in their study 2,257 retired Japanese-American men who were living in Hawaii. All were at least 71 years old and demonstrated generally good physical and mental health. The investigators asked the men what distance they walked each day. The team tested the men 3 and 6 years later for signs of dementia.

Compared with men who had initially averaged at least 2 miles of walking per day, those who had walked less than a quarter mile were 77 percent more likely to develop some form of dementia during the study. Volunteers who had walked between a quarter mile and 1 mile per dab, faced a 71 percent elevated dementia risk, Abbott's team reports in the Sept. 22/29 Journal of the American Medical Association.

In the same issue, Jennifer Weuve of the Harvard School of Public Health in Boston and her colleagues describe long-term effects of physical activity on mental functioning in women.

Rather than diagnosing dementia, Weuve's team gave a series of cognitive-performance tests to each of 18,766 female nurses, 70 to 81 years old. To determine how rapidly cognition declined with age, the investigators repeated the tests about 2 years later.

The team also assessed prior physical activity from data each volunteer had provided more than a decade ago. The investigators factored in both typical intensity of the exercise and time devoted to exercise each week.

Compared with the women who had been least active, those who had been most active scored better on the mental assessments and experienced less cognitive decline in the 2 years between sets of tests. Compared with being highly active, being inactive cost women as much in mental performance as aging 2 to 3 years did, Weuve says. Even women whose activity had been modest--comparable to walking at an easy pace for about 1.5 hours per week--were as cognitively capable as women 1.5 years younger who had been less active, she says.

Both new studies support the view that "physical exercise is protective against cognitive impairment," says neurologist Robert P. Friedland of Case Western Reserve University School of Medicine in Cleveland. He says that an important implication of the research is that "moderate forms of physical exercise, such as walking, are valuable in maintaining health in old age.

"Many older people are reluctant to engage in physical exercise because they think it means they have to run or lift weights," adds Friedland. "As a clinician, I'm happy to tell my patients that walking is an excellent physical activity."

Adds Abbott, "The findings become most meaningful when you consider that walking has been associated with increased longevity and reduced risk of diseases other than dementia, including heart disease and cancer."