Most Alzheimer's disease (AD) researchers agree that the disease starts ravaging the brain years, if not decades, before the first symptoms of forgetfulness appear. New criteria, proposed yesterday at the International Conference on Alzheimer's Disease in Honolulu, would shift the diagnosis earlier in the course of the disease. A major motivation for catching AD in its earliest stages is the belief that treatments will be most effective then.
The recommendations, put together by work groups of researchers organized by the National Institute on Aging and the Alzheimer's Association, build on recent research with neuroimaging and other biomarkers that appear to pick up early signs of the disease. The recommendations define full-blown Alzheimer's dementia more precisely and create two new diagnostic categories to describe earlier stages of the disease.
The first is a "preclinical AD" designation that would require three criteria: evidence of accumulation of amyloid-β (the peptide suspected to be the culprit in neurodegeneration) from PET brain scans or spinal fluid samples, evidence from neuroimaging or spinal fluid samples of synaptic dysfunction or early stages of neurodegeneration, and signs of subtle cognitive decline. This preclinical designation is not intended for clinical use, only for research, including clinical trials for drugs to prevent full-blown AD.
The second designation would be used clinically: "mild cognitive impairment (MCI) due to AD." Patients who meet the criteria for this diagnosis would exhibit a noticeable decline in memory or other cognitive functions but would still be reasonably able to function independently. The proposal contains recommendations for clinicians on how to use neuroimaging and spinal fluid biomarkers to determine whether the impairment is due to incipient AD or to some other cause, although it acknowledges that research in this area is still ongoing.
"We're finally now developing the tools to detect AD pathology in the brain and predict cognitive declines," says Michael Weiner an Alzheimer's researcher at the University of California, San Francisco, who was not involved in drafting the recommendations. Weiner says the new recommendations are "a very, very important step" that will aid the development of drugs to prevent AD and will help families by giving them more time to plan for the care of a loved one with the disease.