October 14, 2008
Adults with memory problems who participated in a home-based physical activity program experienced a modest improvement in thinking and memory skills compared to those who did not participate in the program. The findings appeared in the Journal of the American Medical Association.
The findings are important and urgent, as rates of Alzheimer's disease and other serious memory problems are expected to soar in the coming decades. As the world population ages, the number of older adults living with Alzheimer's disease is estimated to increase from over 26 million today to 106 million by 2050.
"If illness onset could be delayed by 12 months, 9.2 million fewer cases of Alzheimer's disease would occur worldwide," the study authors note. Current Alzheimer's drugs like Aricept, Exelon and Namenda may ease symptoms for a few months or about a year but the effects are small.
The current study looked at the effects of regular physical activity on preventing the onset of Alzheimer's in men and women at high risk for the disease. The researchers, from the University of Melbourne in Australia, looked at 138 adults ages 50 and older who had mild cognitive impairment, a form of memory loss that is not as severe as Alzheimer's but which may lead to the disease. Every year, somewhere from 5 to 15 percent of people with mild cognitive impairment go on to receive a diagnosis of Alzheimer's disease.
Some of the study subjects were randomly assigned to a program involving education and standard care. The others embarked on a 24-week home exercise program. The aim of the program was to encourage participants to perform at least two-and-a-half hours of moderate-intensity physical activity -- in three 50 minute sessions -- per week.
Most of the men and women who were in the exercise group got their exercise by walking at least several times a week. Overall, the group that was encouraged to be physically active averaged 20 minutes more per day of exercise that those in the comparison group.
All were given memory tests over the 18-month study period. By the end of the study, participants in the exercise group had higher memory scores than those who weren't getting as much exercise.
"To our knowledge, this trial is the first to demonstrate that exercise improves cognitive function in older adults with subjective and objective mild cognitive impairment," the authors noted. "The benefits of physical activity were apparent after 6 months and persisted for at least another 12 months after the intervention had been discontinued." Though the effects of exercise were modest and not readily noted by patients and family members, they were statistically significant on the memory tests that the researchers used.
The authors noted other benefits to exercise as well. "Unlike medication, which was found to have no significant effect on mild cognitive impairment at 36 months, physical activity has the advantage of health benefits that are not confined to cognitive function alone, as suggested by findings on depression, quality of life, falls, cardiovascular function, and disability," they wrote.
Other studies have shown that regular walking and other forms of exercise may be an effective way to help ward off Alzheimer's in healthy people. The long-term Nurses' Health Study of 18,766 women, for example, found that higher levels of physical exertion over two years led to higher memory test scores. Similarly, another study found that men who walked at least two miles a day were 1.8 times less likely than sedentary men to develop dementia over a six-year period. And a study of nearly 750 seniors living in Italy who regularly took walks had a lower risk of developing dementia related to poor blood flow in the brain. [See the story, "Want to Keep the Memory Sharp? Try Walking"]
In an accompanying editorial, Dr. Eric B. Larson of the Group Health Center for Health Studies in Seattle, commented on the importance of measures to prevent the onset of Alzheimer's disease. "Health advances of the past century have led to more individuals surviving to extreme old age, when their risk of Alzheimer disease and related dementias increases substantially," he said. "Exercise and possibly other lifestyle factors appear to affect vascular risk and late-life brain health."
In the United States, people over 85 make up the fastest-growing segment of the population, and by the year 2050, an estimated 800,000 Americans will have celebrated their 100th birthday. With advancing age the single greatest risk factor for Alzheimer's, up to 16 million Americans are expected to develop the disease in the coming decades.
Taking steps to prevent the onset of Alzheimer's and to find a cure is critical. In addition to traditional medical approaches to prevent this dreaded disease, Dr. Larson noted, social factors may also play a role. These include providing universal education, general medical care, a suitable environment, adequate nutrition, habitual exercise and opportunities for continued social interactions throughout life, all of which may contribute significantly to improve well-being in late life.
Physical activity may improve brain function in various ways. Exercise may help to maintain the health of blood vessels in the brain, helping to ensure a steady supply of oxygen and nutrients to areas of the brain that are critical for thinking and memory. Physical activity may also help stimulate the release of factors critical for brain cell growth, helping to build up a more robust brain that can resist the damage wrought by Alzheimer's.
Exercise also lowers stress and levels of stress hormones that can damage brain cells. Finally, an active lifestyle may mean more social interaction and stimulation, which has also been shown to lower the risk for Alzheimer's disease.
And while exercise seems to benefit people both young and old, it may be best to maintain a regular exercise program starting at a young age. Alzheimer's may take decades to develop, and taking steps to delay its onset may be most effective the earlier preventive measures are started.
Nicola T. Lautenschlager; Kay L. Cox; Leon Flicker; Jonathan K. Foster; Frank M. van Bockxmeer; Jianguo Xiao; Kathryn R. Greenop; Osvaldo P. Almeida: "Effect of Physical Activity on Cognitive Function in Older Adults at Risk for Alzheimer Disease: A Randomized Trial." Journal of the American Medical Association, Volume 300, Number 9: September 3, 2008, pages 1027-1037.
Eric B. Larson: "Physical Activity for Older Adults at Risk for Alzheimer Disease (editorial)." Journal of the American Medical Association, Volume 300, Number 9: September 3, 2008, pages 1077-1079.