Adults aged 65 years and older, a group at high risk for developing dementia, will soon be the fastest growing age segment in the United States, according to background information in the article. Studies suggest that exercise may reduce the risk of cognitive decline. However, the intensity of exercise needed to maintain cognitive function is uncertain, according to the article.
Jennifer Weuve, Sc.D., from the Harvard School of Public Health, Boston, and colleagues surveyed 18,766 women, aged 70 to 81 years, on their physical activity in biennial questionnaires beginning in 1986. Telephone interviews with the women were conducted from 1995 to 2001, testing general cognition, verbal memory, category fluency, and attention. The women were participants in the Nurses' Health Study, a survey begun in 1976, assessing medical history and health-related behaviors.
The researches found that higher levels of physical exercise were linked to better cognitive performance. The women were divided into five groups depending on their average energy expenditures, one being the lowest and five the highest; groups two through five scored higher on the cognitive performance tests than those in group one. Also, those in the highest activity grouping had a 20 percent lower risk of cognitive impairment than those women in the lowest. Women who walked at an easy pace for at least 1.5 hours per week had higher cognitive scores than those who walked less than forty minutes per week. Women in the two groups with the highest rates of physical activity had significantly less cognitive decline than women with the lowest rate of physical activity.
The authors write: "... the apparent cognitive benefits of greater physical activity were similar in extent to being about three years younger in age and were associated with a twenty percent lower risk of cognitive impairment. The association was not restricted to women engaging in vigorous activities ..."
"In summary, in our study, as well as in other epidemiologic investigations, higher levels of physical activity, including walking, are associated with better cognitive function and less cognitive decline."
(JAMA. 2004; 292: 1454-1461. Available post-embargo at www.jama.com.)
Editor's note: This work was supported by grants from the National Institutes of Health. Dr. Weuve was partially supported by a training grant from the National Institute on Aging.