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Regular exercise reduces risk for dementia and Alzheimer's disease by 30 to 40 percent, new study finds

Author advises older patients to 'use it, even after you begin to lose it'

A new study finds that older adults who exercised three or more times a week had a 30 percent to 40 percent lower risk for developing dementia compared with those who exercised fewer than three times per week.

The study, "Exercise Is Associated with Reduced Risk for Incident Dementia among Persons 65 Years of Age and Older," is published in the Jan. 17, 2006, issue of Annals of Internal Medicine. The entire article is available to the public on Jan. 17, 2006, at http://www.annals.org/cgi/content/full/144/2/73.

Researchers at Group Health Cooperative in Seattle followed 1,750 adults 65 or older with normal mental function for six years. Of the 1,740 subjects, 158 developed dementia and, of these; 107 were diagnosed with Alzheimer’s disease. The rate of dementia was 13.0 per 1,000 person-years for people who exercised three or more times per week, compared with 19.7 per 1,000 person-years for those who exercised fewer than three times per week.

This is the most definitive study yet of the relationship between exercise and risk for dementia. Previous research on this relationship has yielded mixed results.

Participants reported their exercise patterns at two-year intervals. Exercise included: walking, hiking, aerobics, calisthenics, swimming, water aerobics, weight training and stretching.

"We learned that a modest amount of exercise would reduce a person’s risk of dementia by about 40 percent. That’s a significant reduction," said Eric B. Larson, MD, lead study author and director of the Center for Health Studies at Group Health Cooperative.

"Further, the group that benefited the most were the people who were frailest at the start of the study. So this means that older people really should 'use it even after you start to lose it,' because exercise may slow the progression of age-related problems in thinking," Larson said.

In an accompanying editorial, "Mens Sana in Corpore Sano," Laura Podewils, MS, PhD, from the Centers for Disease Control and Prevention, and Eliseo Guallar, MD, DrPH, from the Johns Hopkins Bloomberg School of Public Health, say the study is the "first to report an interaction between level of physical function and physical activity and dementia risk." They say that future research should try to determine whether exercise causes a lower rate of dementia or whether physical activity is a proxy for "life engagement," or other lifestyle or sociodemographic characteristics that are truly associated with development of dementia. Research is also needed to determine the "type, frequency, intensity or duration of physical activity that is most beneficial in preventing cognitive deterioration," the editorialists say.

This text has been updated since its original posting.