"Even those elderly people who did modest amounts of gentle exercise, such as walking for 15 minutes three times a week, appeared to benefit," says Eric B. Larson, director of Group Health Cooperative's Center for Health Studies and the lead investigator for the study.
"Based on these findings, we can advise older people to 'use it even after you start to lose it,' because exercise may slow the progression of age-related problems in thinking," said Larson.
The study followed 1,740 Group Health members, aged 65 and older over a six-year period. The researchers contacted the participants every two years to assess factors potentially affecting dementia, including exercise frequency, cognitive function, physical function, symptoms of depression, and lifestyle characteristics. After six years, 158 participants had developed dementia and 107 of those with dementia had been diagnosed with Alzheimer's disease. People 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.
Larson's study was designed to be more definitive than previous research into exercise and dementia--the results of which have been mixed. In this study, Larson's team used tests scores to ensure that all participants had a minimum level of function at the time the study began. Doing so eliminated participants who might already be developing Alzheimer's disease, but not showing overt signs of the disease--a factor that would make it difficult to determine the true effects of exercise over the duration of the study.
Larson believes that exercise may improve brain function by boosting blood flow to areas of the brain used for memory. "Earlier research has shown that poor blood flow can damage these parts of the brain," he explained. "So one theory is that exercise may prevent damage and might even help repair these areas by increasing blood flow."
Larson advises older people that it's never too late to begin exercising. "Even if you're 75 and have never exercised before, you can still benefit by starting to exercise now."
Simply walking or swimming for 15 minutes three times a week may be enough, added Larson. And programs such as the "EnhanceFitness" classes that Group Health offers to its Medicare Advantage members can be especially helpful because they are designed with attention to senior safety issues, such as avoiding falls.
"As our population ages, strategies are needed to reduce the risks and delay the onset of dementing disorders such as Alzheimer's disease," Larson said. "These findings indicate that programs that encourage elderly people to exercise should be part of those strategies."
This release has been updated since it was posted on January 10, 2006.
The National Institute of Aging funded the study. Other researchers contributing to the study were the University of Washington's Li Wang, MS; James D. Bowen, MD; Wayne C. McCormick, MD, MPH; Linda Teri, PhD; Paul Crane, MD, MPH; and Walter Kukull, PhD.
About Group Health Cooperative's Center for Health Studies
Group Health is a consumer-governed, nonprofit health care system that coordinates care and coverage. Based in Seattle, Group Health and its subsidiary health carriers, Group Health Options, Inc. and KPS Health Plans, serve more than 590,000 members in Washington and Idaho. Group Health's Center for Health Studies conducts research related to prevention, diagnosis, and treatment of major health problems. It is funded primarily through government and private research grants.