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.