by Sue McCurry, PhD
Exercise has long been recognized as an important tool for preventing many chronic diseases such as hypertension, heart disease, and stroke. For example, in 2002, University of Washington ADRC researchers Li Wang and Drs. Gerald van Belle, Walter Kukull, and Eric Larson examined the physical functioning of 2,578 older adults and members of Group Health Cooperative who were participants in the Adult Changes in Thought (ACT) study. To measure physical status, researchers recorded how quickly participants could walk 10 feet and how quickly they could rise up from a chair and sit back down without using their arms for support. Researchers also measured participants’ grip strength and balance, and recorded the number of days per week that participants exercised for 15 minutes or longer. Over four years of follow-up, subjects who exercised regularly were less likely to show declines in their activities of daily living, performed better on physical tasks, and were less likely to die during the follow-up period. This protective effect was even greater in persons already diagnosed with coronary heart disease.
However, there is now growing evidence that exercise also has many beneficial effects for persons with Alzheimer’s disease (AD). A recent issue of DIMENSIONS (Winter 2005), highlighted research conducted by ADRC investigator Dr. Linda Teri and her colleagues showing that persons with AD who participated in a home-based exercise program had better physical functioning and fewer symptoms of depression up to two years after study completion. They were also less likely to be placed in a nursing home due to behavioral disturbance. Since that work was completed, researchers have shown that physical exercise may also be protective against cognitive decline. In a recent study conducted at the University of Pittsburgh, 1,146 adults aged 65 years and older and living in rural community settings were enrolled in a study (the MoVIES Project), and followed for two years. Persons who were in the “high exercise” group (who did aerobic exercise lasting 30 minutes or longer, three or more days per week) were less likely to decline on screening tests of memory and thinking. Why would this be? One possibility, says ADRC researcher Dr. Eric Larson, is that exercise reduces risk for developing vascular diseases, such as high blood pressure and stroke, which themselves are common causes of age-related cognitive decline. However, another possibility is that exercise may have more direct positive effects on brain health and function. A study recently published by investigators at the University of Illinois has shown that persons who were very physically fit had substantially less age-related brain tissue loss as measured by magnetic resonance imaging (MRI). These results suggest that there may be some direct beneficial effects of regular exercise on the vascular fitness of parts of the brain that are vulnerable to age related decline.
If exercise can slow age-related cognitive decline, is it possible that it might also be an effective strategy to delay onset of dementia and Alzheimer’s disease? A number of studies in recent years have suggested that this may be the case. Dr. Larson and his team of ADRC and Group Health Cooperative investigators have been conducting their own research at University of Washington with ACT participants to help further answer this question, and to evaluate whether the relationship between exercise and dementia onset is altered by other factors such as depression, lifestyle practices (such as alcohol consumption, smoking, and vitamin use), or the presence of specific medical diseases. Their study has followed 1,740 subjects, 65 and older, for six years. Although final results of the study are not yet published, the findings do confirm other studies which have shown that persons who exercise regularly may be at reduced risk to develop dementia. This appears to be particularly valuable if they are physically frail. Says Dr. Larson, “Persons who exercised three or more times per week had about a 35 percent reduction in the rate at which they developed Alzheimer’s disease over the time period of our study. I believe these findings are particularly useful, since AD is one of the illnesses feared most as a consequence of aging. Many people say they don’t ‘want to get old’ because they do not want to lose their independence or quality of life. The problem with exercise is that it’s hard for people to change their behavior and exercise regularly. The knowledge that they might be preventing or delaying the onset of Alzheimer’s could be just the motivation many people need to start a regular exercise habit.”