| Alzheimer’s Disease Begins Before Symptoms Appear
St. Louis, Feb. 12, 2001— Researchers at Washington University School of Medicine in St. Louis have new evidence that 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.
The research, presented in the Feb. 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 of age and had been assessed by psychometric tests within two 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 five 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, M.D., 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 call the incubation period a "preclinical" phase and 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 Morris, the Harvey A. and Dorismae Hacker Friedman Professor of Neurology and co-director of the ADRC. .Morris is on the medical staff of Barnes-Jewish Hospital.
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.
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Goldman WP, Price JL, Storandt M, Grant EA, McKeel DW, Rubin EH, Morris JC. Absence of cognitive impairment or decline in preclinical Alzheimer’s disease. Neurology, 56:3, 361-367, Feb. 13, 2001.
Funding from the National Institute of Aging supported this research.
The full-time and volunteer faculty of Washington University School of Medicine are the physicians and surgeons of Barnes-Jewish and St. Louis Children's hospitals. The School of Medicine is one of the leading medical research, teaching and patient-care institutions in the nation. Through its affiliations with Barnes-Jewish and St. Louis Children's hospitals, the School of Medicine is linked to BJC Health System.
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