The new guidelines also make a clearer distinction between Alzheimer's dementia and vascular dementia (such as that caused by stroke), McKhann said. The diagnosis will still be made by a doctor, with help from someone who knows the patient and perhaps the patient him- or herself, but biomarkers may be called in "to augment our certainty about the diagnosis," said McKhann, a professor of neurology and neuroscience at Johns Hopkins University School of Medicine in Baltimore.
Another stage, MCI, can represent an earlier phase of dementia and consists of modest impairments, primarily in memory, which can be a harbinger of full-blown Alzheimer's years down the road. In the research arena, investigators will be working towards standardizing biomarkers which indicate, for example, the presence of amyloid protein or nerve damage in the brain.
But for now, how diagnoses are made "will be extremely similar to what's been used in the last 10 years," said Albert, who added that "a very large number" of individuals with MCI do go on to develop Alzheimer's.
"Older adults with MCI progress to dementia at a higher rate than those with no impairment, but progression is not inevitable," according to the Alzheimer's Association's online overview of mild cognitive impairment.
"Not everyone diagnosed with MCI goes on to develop Alzheimer's," the association noted.
The preclinical category was formulated for research purposes only, namely to study biomarkers that may be present in the blood or cerebrospinal fluid or evident on different imaging tests that would indicate the build-up of amyloid plaque or damage to nerve cells.
"The main conceptual point was to define Alzheimer's on the basis of the underlying brain changes rather than just requiring clinical symptoms," said Dr. Reisa A. Sperling, a neurologist at Brigham and Women's Hospital and associate professor of neurology at Harvard Medical School in Boston
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