The National Institute on Aging and the Alzheimer’s Association are issuing new medical guidelines today that divide Alzheimer’s disease into three stages. The first stage, which may be considered pre-clinical — meaning before any mental dysfunction is apparent — is the most recently characterized phase. This stage, of currently unknown duration, is defined by changes in the brain — manifested by alterations of certain biomarkers (measurable substances in the blood or spinal fluid correlated with the disease) or on imaging studies such as MRI or PET scans — with no overt symptoms. The middle stage is categorized by the emergence of mild cognitive problems with no interruption in daily function, while the last stage indicates the development of dementia.
Currently, cerebral spinal fluid analyses and brain scans test for abnormal levels of the proteins beta-amyloid and tau, or shrinkage of certain brain areas, respectively. These tests, however, are still under investigation and are not yet reliably predictive for definite diagnosis of Alzheimer’s, except in advanced cases.
Dr. Steven DeKosky, dean of the University of Virginia medical school reiterates this point: “We don’t have enough information about what to tell people. 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.”
This clarification is especially important since there are currently no drugs available that can effectively halt or significantly delay the onset of symptoms — although some of the approved drugs can slow disease progression briefly, albeit in a minority of patients.
The ultimate goal is to identify reliable biomarkers that will accurately predict the eventual development of clinically significant Alzheimer’s. “The sooner we can get such indicators, the more likely we’ll be able to interfere with the disease’s progress, especially when we develop effective new pharmaceutical treatments,” says ACSH’s Dr. Gilbert Ross. “Building such a database of research will hopefully break the chain of events that, at this point, irrevocably lead to Alzheimer’s. Hopefully, we’ll be able to break this chain within ten years or less, when the pathogenesis is more clearly delineated and focused drug interventions will be accelerated.”