What’s the News: Alzheimer’s is getting an update: for the first time in 27 years, the national criteria for diagnosing the disease have been revised. The new criteria are intended only for use by researchers studying the disease, but they are important because they acknowledge growing evidence for an early stage of Alzheimer’s that could be detectable with biological tests before cognitive impairment sets in.
What’s the Context:
Alzheimer’s disease, which involves the gradual loss of memory, language, and other mental skills, affects more than five million people in the U.S., mostly elderly. In autopsies—the only sure way of diagnosing the disease—the brains of Alzheimer’s patients are dotted with clumps, or plaques, of a protein called beta amyloid, and may show other signs of neurological damage. Doctors rely on cognitive tests and general assessment to make diagnoses while patients are alive. There is no cure; several drugs are used to slow progression, with limited success.
However, a rash of studies from the last few years indicate that biological signs of the disease may be detectable years before people become impaired: new brain scans and tests of spinal fluid in research studies show promise for detecting the disease in its early stages. In particular, abnormal levels of proteins amyloid and tau seem to be “biomarkers” for the disease.
The new criteria, developed by the National Institute on Aging and the Alzheimer’s Association, describe an early phase of the disease that’s identifiable only with biomarkers, adding to the previously existing descriptions of a middle phase with mild cognitive impairment and a late phase with profound dementia. But because the new tests are still being developed—they haven’t been standardized and rigorously tested—they’re only for use in research. (For more detail, check out the Alzheimer’s Association’s FAQ (pdf).)
The Future Holds: For now, researchers will use the criteria to make sure that they're all using the same definition of early stage Alzheimer's in their studies. Tests won't be hitting your doctor's office any time soon, but revising the guidelines for diagnosis to include biomarkers indicates that the scientific community is moving in that general direction.