Alzheimer's disease was clarified today.
With the announcement of new diagnostic guidelines, developed in tandem by the National Institute of Aging and the National Alzheimer's Association, we can now conceptualize the disease across a continuous spectrum with three contiguous stages of progression. There is a pre-clinical stage, a mild cognitive impairment stage, and a dementia stage.
Pre-clinical Stage
The purpose of defining this very early stage, before the presence of any clinical symptoms, is purely to benefit research. While there are no symptoms of disease in this stage, researchers have noted that certain biological changes, including protein levels in the brain, blood, and spinal fluid, seem to change in fairly predictable ways during the years before Alzheimer's patients manifest symptoms. The changes are not sufficiently telling to diagnose the disease at this early stage, but identifying these individuals and enlisting them as research subjects is an important goal for the field.
Importantly, physicians will not use these criteria to diagnose such early stage Alzheimer's. The definition of this stage is purely to help researchers speak a common language about similarly characterized research subjects.
Mild Cognitive Impairment Stage
In this stage, patients have clear underlying pathology consistent with Alzheimer's disease, and have also developed clinical symptoms of memory loss or other cognitive deficits.
The identification of this stage is the most important aspect of the new guidelines, as it will enable earlier intervention for patients who are, almost certainly, in the progressive throes of Alzheimer's, but still have relatively healthy brains. It is hoped that existing treatments, and new treatments in the pipeline, will be optimally effective in these early stage patents.
Dementia Stage
This stage is quite consistent with our former view of the disease. It requires the hallmark pathology of amyloid plaques in the brain, plus cognition so impaired as to meet the criteria for dementia (two or more realms of impaired cognition that interrupt daily activities of living). In the past, we did not call the problem "Alzheimer's disease" until the patient reached this end stage condition.
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