Exercise associated with reduced risk of dementia in older people

Older adults who exercised at least three times a week were much less likely to develop dementia than those who were less active, according to a new study. The study did not demonstrate directly that exercise reduces risk of dementia, but it joins a growing body of observational research pointing to an association between exercise and cognitive decline, say scientists at the National Institute on Aging (NIA), a component of the National Institutes of Health (NIH), U.S. Department of Health and Human Services, which funded the study.

The research, reported in the January 17, 2006, issue of the Annals of Internal Medicine, was conducted by Eric B. Larson, M.D., Ph.D., and colleagues at the Group Health Cooperative (GHC), the University of Washington, and the VA Puget Sound Health Care System in Seattle, WA. Larson and co-investigators followed 1,740 GHC members age 65 or older for an average of 6.2 years between 1994 and 2003. When the study began, the participants — all of whom were tested and found to be cognitively normal — reported the number of days per week they engaged in at least 15 minutes of physical activity, such as walking, hiking, bicycling, aerobics, or weight training. Their cognitive function was then assessed, and new cases of dementia were identified, every 2 years. By the end of the study, the rate of developing dementia was significantly lower for those who exercised more — 13.0 per 1,000 “person years” for those who exercised three or more times weekly, compared with 19.7 per 1,000 “person years” for those who exercised fewer than three times per week — a 32 percent reduction in risk.

“Physical activity has been shown to be beneficial for health and aging in a number of areas,” says Dallas Anderson, Ph.D., program director for population studies in the Dementias of Aging Branch of NIA’s Neuroscience and Neuropsychology of Aging Program. “This emerging association between exercise and cognitive health is increasingly important to understand.” The NIA is beginning to support clinical trials which seek to test exercise for its direct effect on cognitive function. Such research, Anderson says, should help sort out whether exercise reduces risk of cognitive decline or whether other factors related to exercise, such as increased social interaction, play a role. Additional study also may provide information on the possible merits of varying types of exercise.