Alzheimer's Disease Can Be Asymptomatic at the Start

February 13, 2001

New York (MedscapeWire) Feb 13 — Alzheimer's disease (AD) begins to affect the brain even before a person experiences the memory loss and other cognitive impairments that accompany the disorder, say researchers at Washington University School of Medicine in St. Louis, Missouri.

The research, published in the February 13 issue of Neurology, suggests that efforts to develop vaccines and targeted therapies need to be redirected toward preclinical signs of brain deterioration. AD affects an estimated 4 million Americans.

Researchers at the school's Alzheimer's Disease Research Center (ADRC) identified 24 people who died when they were at least 75 years or older and had been assessed by psychometric tests within 2 years of death. At their final assessment, 10 of these individuals were diagnosed with very mild dementia of the Alzheimer type, whereas the other 14 showed no signs of cognitive decline.

Postmortem examinations revealed that 5 of those who had no cognitive impairment had plaques and brain deterioration typical of AD. Their psychometric assessment results were the same as those who had no AD neuropathology, and their cognitive performance had not declined over the years. In contrast, patients diagnosed with very mild dementia before death had performed progressively worse on the annual psychometric evaluations.

"These findings suggest that a person beginning to develop AD might not have any cognitive signs of the disease," says John C. Morris, MD, who led the study. William P. Goldman, Ph.D., a former neurology fellow now at the University of California, San Francisco, was first author of the paper.

The authors recommend that the current view of AD development and progression be revamped. "To develop a treatment that will prevent dementia, we apparently need to find ways to identify the appearance of AD lesions before clinical symptoms arise," says Dr. Morris, professor of neurology and co-director of the ADRC.

He believes that the study, taken in the context of previous findings, fails to support the notion that everyone who lives long enough becomes senile. "Our work suggests that aging itself is an entity distinct from AD," he says. "The data imply that cognitive abilities in normal aging by and large remain intact as long as AD and other dementing illnesses are absent.

Neurology. 2001;56(3):361-367

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