CHICAGO (AP) -- Certain protein deposits in the brains of Alzheimer's victims may be a cause of the mind-robbing disease -- not just a symptom, researchers suggested Wednesday.
Autopsies on 79 nursing home patients confirmed that beta-amyloid protein plays a role in the earliest stages of Alzheimer's, even before symptoms of dementia appear, the researchers reported in Wednesday's Journal of the American Medical Association.Sticky plaques of beta-amyloid in the brain and tangles of a protein known as "tau" inside brain nerve fibers are two of the distinguishing features of Alzheimer's, which affects more than 4 million Americans.
Scientists disagree over which feature may play a more central role in the destruction of brain cells. And some believe that the plaques and tangles are actually markers left by nerve cells killed by some other unknown cause.
The study's authors favor the beta-amyloid theory because they found that the presence of beta-amyloid preceded development of tau protein in the brain's frontal cortex.
In an accompanying editorial, Dr. Dennis J. Selkoe, a neurologist at Harvard's Brigham and Women's Hospital, called the conclusion exciting and said it could lead to new ways to diagnose and treat Alzheimer's.
"This work, coupled with early work, clearly points to amyloid build-up as the cause," said Selkoe, who holds a stake in Elan Corp., which is testing a vaccine aimed at preventing beta-amyloid accumulation.
But an executive at the Alzheimer's Association said the study does not prove what causes the disease.
"What it doesn't tell us is which comes first, the chicken or the egg -- the disease or beta-amyloid," said William Theis, vice president for medical and scientific affairs at the Alzheimer's Association.
The authors studied autopsy results on 63 patients with mild to severe dementia believed to be caused by Alzheimer's and 16 mentally healthy patients.
On the Net: National Library of Medicine site on Alzheimer's disease: www.nlm.nih.gov/medlineplus/alzheimersdisease.html
Alzheimer's Association site: www.alz.org