A long-term study of the elderly has found that their average rate of weight loss doubles in the year before the first symptoms of Alzheimer's-type dementia are detected.
The study is the first to confirm a link between weight loss and dementia tentatively identified a decade ago.
Alzheimer's researchers are working hard to find biomarkers, indicators that can be used to detect the presence of Alzheimer's before clinical symptoms appear. Studies have strongly suggested that if Alzheimer's treatments will ever prevent lasting cognitive damage, they may have to be given before memory loss and other disruptions caused by the disorder are evident.
"A person's weight can vary substantially in a given year, so weight loss alone can't serve as a definite indicator for physicians," says David K. Johnson, Ph.D., research instructor in neurology. "But it's interesting from a biochemical perspective-we don't know why these two phenomena are linked. And weight loss may one day be incorporated into a battery of biomarkers that physicians keep their eyes on for early warning of Alzheimer's-type dementia."
The study appears in the September 2006 Archives of Neurology. It used data from the Memory and Aging Project at the Alzheimer's Disease Research Center (ADRC) of Washington University School of Medicine in St. Louis.
The Memory and Aging Project, which began in 1979, is a long-term study of the links between cognitive health and aging. The project is made possible through the cooperation of hundreds of volunteers age 65 and older who undergo a detailed annual evaluation of their cognitive, neurological and physical health.
Studies have suggested that weight generally begins a slow but steady decline of about half a pound per year in the late 50s and early 60s. Gerontologists have speculated that the decline may be attributable to physical shrinkage of the body seen in old age, loss of interest in eating or the effects of cancers and other illnesses.
The study analyzed data on 449 participants, most in their 70s and 80s, but some as young as 65.
"Interestingly, the group of volunteers who did become demented started the study weighing about eight pounds less on average than the patients who did not develop dementia," Johnson notes. "The two groups lost weight at the same rate for four to five years, and then one year before the detection of even the mildest cognitive symptoms, weight loss increased in the group that would eventually be diagnosed with mild dementia."
It is unclear why the group that developed dementia began the study at a lower average weight. Johnson speculates that a process somehow related to Alzheimer's might have become active earlier in the participants' lives and started to drive their weight down. Alternatively, persons with lower average weight may be more vulnerable to Alzheimer's.