Thanks to long-term studies using brain imaging and biomarker analysis, scientists know that physiological signs of Alzheimer’s disease begin to appear long before individuals notice changes in their memory. New guidelines for diagnosing Alzheimer’s, put forth today by the National Institute on Aging and Alzheimer’s Association, recognize the earliest stages of the neurodegenerative disorder and encourage the use of early monitoring technologies in drug development. In fact, given the difficulty in developing treatments for the disease, it may be that the most effective drugs need to be delivered very early in disease progression.
“The new guidelines reflect today’s understanding of how key changes in the brain lead to Alzheimer’s disease pathology and how they relate to the clinical signs of mild cognitive impairment and Alzheimer’s disease dementia,” said Creighton Phelps, program director of the Alzheimer’s Disease Centers Program at the National Institutes of Health, in a press release from the Alzheimer’s Association. “We are also beginning to be able to detect these changes at a preclinical stage, long before symptoms appear in many people. With further research on biomarkers, as set forth in the new guidelines, we may ultimately be able to predict who is at risk for development of mild cognitive impairment and Alzheimer’s dementia, and who would benefit most as interventions are developed.”
According to the authors, in order to facilitate the possibility of future presymptomatic treatment of Alzheimer’s, it was important to define the disease from the earliest changes in the brain, not only the observable, symptomatic stages of the disease. The authors propose that Alzheimer’s begins with a long asymptomatic period during which detrimental changes are progressing in the brain, and individuals with biomarker evidence of these changes are at increased risk for developing cognitive and behavioral impairment and progression to Alzheimer’s dementia.
For now, the change will mainly be felt in clinical trials rather than in standard clinical practice, as scientists use these technology to monitor the effectiveness of experimental drugs.
According to the New York Times.
For now, the guidelines specify that Alzheimer’s biomarkers — including abnormal levels of the proteins amyloid and tau, and shrinkage of certain brain areas — should not yet be put into widespread use, but used only with patients enrolled in clinical trials.
That is because scientists cannot yet standardize the results of the tests, or know “what measure is truly abnormal and what measure is not,” said Marilyn Albert, director of the Johns Hopkins Alzheimer’s Disease Research Center, and a leader of one working group that developed the new guidelines.
As many as a third of people with amyloid plaques in their brains, for example, have not developed Alzheimer’s symptoms by the time they die. The guidelines also urge caution because there is currently no drug known to halt or significantly delay the onset of symptoms, so people told they are likely to get Alzheimer’s have no effective medication to take.
“We don’t have enough information about what to tell people,” said Dr. Steven DeKosky, dean of the University of Virginia medical school, who participated in one of the working groups. “Until you can tell a clinician, ‘If you do this test you have X amount of reliability and to do that will make a difference in the life of your patient’ — until then, it remains in the lab.”