Evidence Growing that Alzheimer's Risk Greatly Diminished by Exercise

Oct. 4, 2005–A new study published today adds to the growing evidence that exercise – particularly if it starts early and is maintained over time - is beneficial in preventing dementia and Alzheimer’s disease. The new study focused on the physical activity levels of older people when they were middle aged and concludes being physically active in midlife can significantly decrease the risk of dementia and Alzheimer’s.

The investigators in this study found that older people (65-79) who had participated in leisure-time physical activity at least twice a week in middle age had a 60 percent lower risk of AD. The report appears in today’s edition of The Lancet Neurology.

The active group also had 50% lower risk of dementia compared to the sedentary group, which participated in physical activity less than twice a week.

The researchers also found that for individuals who are genetically susceptible to AD (carriers of the gene variant APOE4), physical activity has a more pronounced effect against developing dementia or AD in later life. This variant is found in about one-quarter to one-third of Alzheimer's patients.

The authors state that interventions that could postpone the onset of AD even modestly would have a major public health impact, as the proportion of old people is increasing. Dr. Miia Kivipelto, leader of the study, states: “These findings may have wide implications for preventive healthcare; if an individual adopts an active lifestyle in youth and at midlife, this may increase their probability of enjoying both physically and cognitively vital years later in life”.

This is the latest of several studies this year, which if considered in whole, seem to show that people who are at least mildly active through middle age and into their senior citizen years, are at about half the risk of dementia and Alzheimer's as inactive adults.

Intensity of exercise not a factor

Another study released in April, also detected a decreased risk for dementia among active people. The variety of leisure and physical activity one engages in -- and not its intensity in terms of calories expended - may reduce dementia risk in older people, according to researchers at Johns Hopkins.

The study included 3,375 men and women age 65 years or older who participated in the Cardiovascular Health Cognition Study from 1992 to 2000 and who did not have dementia at the onset of the study. The researchers found 480 new cases of dementia over an average of 5.4 years of follow-up. Among these, dementia occurred less frequently in those participating in more activities relative to those who participated in fewer activities (one or no activity had 130 cases, two activities had 152 cases, three activities had 113 cases, four or more activities had 84 cases). The association held true for all types of dementia, including Alzheimer's disease and vascular dementia.

The association in this study did not, however, hold true for those who have the APOE-4 genotype, as it does in the study reported today.

"These findings, taken together with recent findings from our colleagues at the University of Chicago studying physical activity and plaque buildup in the brains of mice with Alzheimer's provide a good picture from basic and clinical science of how activity and exercise work to reduce the risk of dementia," said Constantine G Lyketsos, M.D., professor of psychiatry and behavioral sciences at Johns Hopkins and senior author on the report.

The study of mice to which she referred found a link between an enriched environment and Alzheimer's-like brain changes in mice. That study, published by Orly Lazarov, Ph.D., and colleagues in the March 11, 2005, issue of the journal Cell, found that beta-amyloid levels decreased in the brains of a kind of transgenic mice when they were housed in groups and in environments that were enriched with running wheels, colored tunnels, and toys.

Active mice have less Alzheimer’s plaque in brains

There was also a study at the University of California that was released in April that found physical activity appears to inhibit Alzheimer's-like brain changes in mice, slowing the development of a key feature of the disease. This research demonstrated that long-term physical activity enhanced the learning ability of mice and decreased the level of plaque-forming beta-amyloid protein fragments--a hallmark characteristic of Alzheimer's disease (AD)--in their brains.

Mice that had exercised for 5 months on the running wheels had significantly fewer plaques and fewer beta-amyloid fragments (peptides) in the cerebral cortex and hippocampus, approximately by 50 percent. The sedentary mice, to which they were compared, had no running wheels in their cages. Additional studies, of exercised animals at 10 weeks old, showed that the mechanism underlying this difference began within the first month of exercise.

There have been other studies, too, that focused on evidence that staying mentally active as people grow older seems to lower the risk of dementia and Alzheimer's. And, in the studies indicting physical activity lowers AD risk, the emphasis is not on rigorous exercise - just regular activity.

There definitely seems to be a trend line developing that says staying mentally and physically active is very beneficial in the fight against the loss of cognitive ability, that is so highly feared by most senior citizens.