In April 2011, the National Institute on
Aging and the Alzheimer’s Association issued new diagnostic guidelines
that divide Alzheimer’s disease into three distinct stages, reflecting recent
evidence that the disease begins to affect the brain years before symptoms
become evident.
For the first time in 27 years, clinical diagnostic criteria for Alzheimer's disease have
been revised, and research guidelines for earlier stages of the disease have
been characterized to reflect a deeper understanding of the disorder. The
National Institute on Aging/Alzheimer's Association Diagnostic Guidelines
for Alzheimer's Disease outline some new approaches for clinicians and provides
scientists with more advanced guidelines for moving forward with research on
diagnosis and treatments. They mark a major change in how experts think about
and study Alzheimer's disease. Development of the new guidelines was led by the
National Institutes of Health and the Alzheimer's Association.
The original
criteria were the first to address the disease and described only later stages,
when symptoms of dementia are already evident. The updated guidelines announced
today cover the full spectrum of the disease as it gradually changes over many
years. They describe the earliest preclinical stages of the disease, mild
cognitive impairment, and dementia due to Alzheimer's pathology.
Importantly, the
guidelines now address the use of imaging and biomarkers in blood and
spinal fluid that may help determine whether changes in the brain and
those in body fluids are due to Alzheimer's disease. Biomarkers are
increasingly employed in the research setting to detect onset of the disease
and to track progression, but cannot yet be used routinely in clinical
diagnosis without further testing and validation.
"Alzheimer's
research has greatly evolved over the past quarter of a century. Bringing the
diagnostic guidelines up to speed with those advances is both a necessary and
rewarding effort that will benefit patients and accelerate the pace of
research," said National Institute on Aging Director Richard J. Hodes,
M.D.
"We believe
that the publication of these articles is a major milestone for the
field," said William Thies, Ph.D., chief medical and scientific officer at
the Alzheimer's Association. "Our vision is that this process will result
in improved diagnosis and treatment of Alzheimer's, and will drive research
that ultimately will enable us to detect and treat the disease earlier and more
effectively. This would allow more people to live full, rich lives without-or
with a minimum of-Alzheimer's symptoms."
New Guidelines
The original 1984
clinical criteria for Alzheimer's disease, reflecting the limited
knowledge of the day, defined Alzheimer's as having a single stage, dementia,
and based diagnosis solely on clinical symptoms. It assumed that people free of
dementia symptoms were disease-free. Diagnosis was confirmed only at autopsy,
when the hallmarks of the disease, abnormal amounts of amyloid proteins forming
plaques and tau proteins forming tangles, were found in the brain.
Since then, research
has determined that Alzheimer's may cause changes in the brain a decade or more
before symptoms appear and that symptoms do not always directly relate to
abnormal changes in the brain caused by Alzheimer's. For example, some older
people are found to have abnormal levels of amyloid plaques in the brain at
autopsy yet never showed signs of dementia during life. It also appears that
amyloid deposits begin early in the disease process but that tangle formation
and loss of neurons occur later and may accelerate just before clinical
symptoms appear.
To reflect what has
been learned, the National Institute on Aging/Alzheimer's Association
Diagnostic Guidelines for Alzheimer's Disease cover three distinct stages of Alzheimer's disease:
- Preclinical
The preclinical stage, for which the guidelines only apply in a research
setting, describes a phase in which brain changes, including amyloid
buildup and other early nerve cell changes, may already be in process. At this
point, significant clinical symptoms are not yet evident. In some people,
amyloid buildup can be detected with positron emission tomography (PET) scans and
cerebrospinal fluid (CSF) analysis, but it is unknown what the risk for
progression to Alzheimer's dementia is for these individuals. However, use of
these imaging and biomarker tests at this stage are recommended only for
research. These biomarkers are still being developed and standardized and are
not ready for use by clinicians in general practice.
- Mild
Cognitive Impairment (MCI)
The guidelines for the MCI stage are also largely for research, although
they clarify existing guidelines for MCI for use in a clinical setting. The MCI
stage is marked by symptoms of memory problems, enough to be noticed and
measured, but not compromising a person's independence. People with MCI may or
may not progress to Alzheimer's dementia. Researchers will particularly focus
on standardizing biomarkers for amyloid and for other possible signs of injury
to the brain. Currently, biomarkers include elevated levels of tau or decreased
levels of beta-amyloid in the CSF, reduced glucose uptake in the brain as
determined by PET, and atrophy of certain areas of the brain as seen with
structural magnetic resonance imaging (MRI). These tests will be used
primarily by researchers, but may be applied in specialized clinical settings
to supplement standard clinical tests to help determine possible causes of MCI
symptoms.
- Alzheimer's Dementia
These criteria apply to the final stage of the disease, and are most
relevant for doctors and patients. They outline ways clinicians should approach
evaluating causes and progression of cognitive decline. The guidelines also
expand the concept of Alzheimer's dementia beyond memory loss as its most
central characteristic. A decline in other aspects of cognition, such as
word-finding, vision/spatial issues, and impaired reasoning or judgment may be
the first symptom to be noticed. At this stage, biomarker test results may be
used in some cases to increase or decrease the level of certainty about a
diagnosis of Alzheimer's dementia and to distinguish Alzheimer's dementia
from other dementias, even as the validity of such tests is still under study
for application and value in everyday clinical practice.
Federal Alzheimer’s Activity
The revisions to the
diagnostic guidelines – the first in nearly three decades – indicate how far
scientists have come in understanding the disease and are reflected in new
legislation introduced in both the Senate (S.738) and the
House (H.R.1386)
that would expand Medicare coverage of Alzheimer’s to cover “comprehensive
Alzheimer’s disease diagnosis and services,” including for individuals who fall
under stage (1) or (2) of the new guidelines.
More significantly,
the new guidelines and proposed legislation follow closely on the heels of the passage,
earlier this year, of the National Alzheimer’s Project Act (NAPA). NAPA charges
the Secretary of Health and Human Services with developing “an integrated
national plan to overcome Alzheimer’s,” including by accelerating the
development of treatments, improving patient diagnosis and care and
coordinating efforts across all Federal agencies. Although NAPA did not include
any Federal appropriations, its supporters believe it represents a significant
commitment to fighting the disease and will lead to an increase in funding, as
well as in awareness.
You can review NAPA
report below:
Sources and Additional
Information:
