TUESDAY, April 19 (HealthDay News) -- The first new guidelines
in 27 years for the diagnosis of Alzheimer's disease could double
the number of Americans defined as having the brain-robbing
The guidelines, issued Tuesday by the Alzheimer's Association
and the U.S. National Institute of Aging, differ in two important
ways from the last recommendations, which have been in use since
First, Alzheimer's is now being recognized as a continuum of
stages: Alzheimer's itself with clear symptoms; mild cognitive
impairment (MCI) with mild symptoms; and also the "preclinical"
stage, when there are no symptoms but when recognizable brain
changes may already be occurring.
Second, the new guidelines incorporate the use of so-called
"biomarkers" -- such as the levels of certain proteins in blood or
spinal fluid -- to diagnose the disease and assess its progress,
but almost exclusively for research purposes only.
Still, the authors of the guidelines emphasized that these
revisions are unlikely to change what happens in doctors' offices
when diagnosing Alzheimer's or its precursors.
"It will not change practice," said Dr. Guy M. McKhann, one of the guideline authors, at a Monday press conference.
MCI will, however, become a new diagnosis. And that could mean
that the number of people considered to be on the new Alzheimer's
continuum could double, said Marilyn Albert, another author,
director of the division of cognitive neuroscience at Johns
Hopkins. But how MCI is determined won't change.
The new U.S. National Institute on Aging/Alzheimer's Association
Diagnostic Guidelines for Alzheimer's Disease now recognize three
clear stages of Alzheimer's disease.
The first and most severe is Alzheimer's dementia, when patients
are clearly cognitively and functionally impaired. This is to be
characterized now not just by memory loss but also visual, spatial
and judgment problems.
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
"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
"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. "We thought our best chance for disease-modifying therapy was to detect evidence of the disease and intervene much earlier."
As in cancer and diabetes, McKhann pointed out, if you're trying
therapies "only in people who have advanced dementia, the chances
of them working is not very great."
"We're worried that there could be drugs around now that could be beneficial but that we could be using them too late in the disease course," added Albert.
The new guidelines, summarized William Thies, chief medical and
scientific officer of the Alzheimer's Association, "will result in
little change in current clinical practice of medicine as applied
to Alzheimer's disease. . . . [However] the new criteria are really
extending the range of our ability to investigate this disease and
eventually to find treatments that will be so necessary to avoid
the epidemic of Alzheimer's that we see facing us."
The new guidelines appear in four papers in
Alzheimer's & Dementia: The Journal of the Alzheimer's
The Alzheimer's Association has more about
mild cognitive impairment (MCI).
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