Loss of body mass over time appears to be strongly linked to older adults’ risk of developing Alzheimer’s disease (AD), and the greater the loss the greater the chance of a person developing the disease, new research has found. The findings are the first to associate decline in body mass index (BMI) with the eventual onset of AD. The researchers suggest that the loss of body mass reflects disease processes and that change in BMI might be a clinical predictor of the development of AD.
The research, reported in the September 27, 2005, issue of Neurology, was conducted by Aron S. Buchman, M.D., David A. Bennett, M.D., and colleagues at Rush University Medical Center in Chicago, IL, as part of the Religious Orders Study. The Religious Orders Study is a comprehensive, long-term look at aging and AD among Catholic nuns, priests, and brothers nationwide that has been funded by the National Institute on Aging (NIA), a component of the National Institutes of Health, U.S. Department of Health and Human Services, since 1993. Rush University Medical Center is one of more than 30 Alzheimer’s Disease Centers supported by the NIA.
“People with Alzheimer’s disease are known to lose weight and body mass after they have the disease,” says Dallas W. Anderson, Ph.D., program director for population studies in the Dementias of Aging Branch of NIA’s Neuroscience and Neuropsychology of Aging Program. “This study is significant in that it looks at body mass changes in the years preceding dementia and cognitive decline. Other studies have looked at BMI at only one point in time or studied body mass loss in people who already have AD.”
Each of the 820 study participants took part in yearly clinical evaluations that included a medical history, neurologic examination, and extensive cognitive function testing. The participants’ weights and heights were also measured to determine their BMI, a widely used measure of body composition that is calculated by dividing weight in kilograms by height in meters squared. They completed an average of 6.6 annual evaluations, with a 95 percent follow-up rate. All of the participants were older than 65 years, and the vast majority of them were white and of European ancestry.
When the study began, none of the participants had dementia, and their average BMI was 27.4. During the follow-up period, 151 of the participants (18.4 percent) developed AD. Both baseline BMI and the annual rate of change in BMI were linked to the risk of developing AD.
People who lost approximately one unit of BMI per year had a 35 percent greater risk of developing AD than that of people with no change in BMI over the course of the study. Those with no change in BMI had a 20 percent greater risk of developing the disease than that of people who gained six-tenths of a unit of BMI per year.
The findings held true even after adjusting for factors such as chronic health problems, age, sex, and education. They also held true when those who developed AD in the first 4 years of follow-up — and might have had mild, undiagnosed AD early in the study — were excluded from the analysis.
For more information on participation in an AD clinical trial, visit http://www.clinicaltrials.gov/ (search for "Alzheimer’s disease trials"), or the Alzheimer’s Disease Education and Referral (ADEAR) Center website at http://www.alzheimers.org.
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