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Researchers Claim 95 Percent Success in Predicting
Alzheimer’s
They use relatively inexpensive, painless, and
easy-to-use tool called an EEG
 Oct.
6, 2005 – One of the most pursued challenges in medicine is finding a
means of detecting Alzheimer’s disease, the most common form of dementia
for senior citizens, in its early stages. The medicines now available
work best if prescribed in the early stages of the disease, when victims
have only mild cognitive impairment. Now a new study says the earliest
manifestations of Alzheimer's can be found with a relatively
inexpensive, painless, and easy-to-use tool called an EEG
(electroencephalograph). The researchers claim a 95 percent success
rate.
In the study, by a group at NYU School of Medicine,
the researchers found that a computer analysis of the EEG, which
measures the brain's electrical activity, accurately predicted healthy
people in their 60s and 70s who would develop dementia over the next 7
to 10 years. It also identified individuals who would remain virtually
unchanged over the same time span. The EEGs were almost 95 percent
accurate in identifying those who would decline cognitively and those
who would not, according to the study.
"Our results suggest that quantitative analysis of
the EEG is sensitive to the earliest signs of the dementing process,"
says Leslie S. Prichep, Ph.D., Associate Director of the Brain Research
Laboratories of the Department of Psychiatry, who led the study. Some
day she says it may be used as one of the tools to evaluate a person's
propensity for developing Alzheimer's, the most common form of dementia
affecting people over 65. But for now the results need to be replicated
in and validated by much larger prospective studies before they can be
applied to screen large populations.
It takes about 30 minutes to perform an EEG, which
involves placing recording electrodes on the scalp. The test is perfomed
with the patient seated comfortably. There are no injections and the
scalp is not shaved.
The NYU researchers, led by Dr. Prichep and Roy
John, Ph.D., Professor in the Department of Psychiatry, evaluated a
group of 44 individuals between the ages of 64 and 79 who felt that
their memories were faltering. These people enrolled voluntarily in a
long-term study at NYU's Silberstein Aging and Dementia Research Center
where they underwent a battery of neuropsychiatric and other tests,
which revealed that their brain function was normal for their age.
At the beginning of the testing process each
volunteer was also given a baseline EEG test at the Brain Research
Laboratories at NYU School of Medicine. They were tested there several
more times over the next 7 to 10 years. Over this period, 27 of the 44
subjects developed mild cognitive impairment or full-blown dementia, and
17 remained stable. Applying a mathematical algorhythm to the brain
scans, Drs. Prichep and John showed that certain characteristics of the
pattern of brain waves on the baseline EEG were associated with future
cognitive deterioration.
To the untrained eye EEGs look like a confusing
thicket of squiggly lines. But the lines are actually waves that have
been described mathematically by their amplitude and frequency
composition as a function of age, based on data collected over the last
30 years by Drs. Prichep and John. They and their NYU colleagues
obtained this data from some 12,000 healthy people and psychiatric
patients who had been given EEGs. About 3,500 of the EEGs were from
aging and dementia patients.
"We probably have the largest electrophysiological
database of this kind in the world," says Dr. Prichep. "Since we can
compare each individual's quantitative EEG to age-expected normal
values, we were able to describe which features reflected expected
changes occurring with normal aging and which might be associated with
future decline," she says.
A prominent feature associated with cognitive
deterioration on the baseline EEG was a brain wave called theta, which
was excessive in people who would eventually decline, according to the
study. This band was particularly abnormal in the frontal regions, along
the lateral regions and in the right posterior region of the brain in
those people who went on to decline.
Another feature was a slowing in the mean frequency
of the EEG, which is described in cycles per second. Yet another
distinctive feature of those who decline was a change in the
synchronization between the two sides of the brain. The source of the
theta has been shown to be the hippocampus, a brain region demonstrated
in imaging studies with MRI and PET to be impaired in dementia, notes
Dr. Prichep.
The report will be published in the upcoming
on-line issue of the journal Neurobiology of Aging,
Abut the study:
The NYU researchers who contributed to this study
are Drs. Prichep and John, Steven Ferris, Ph.D., Lawrence Rausch, PhD,
Zeke Fang, PhD, Robert Cancro, M.D., Carol Torossian, Ph.D. and Barry
Reisberg, M.D.
The study was supported by grants from National
Institutes of Health, among other organizations.
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