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The more formal
education a person has, the better his or her memory and learning
ability even in the presence
of brain abnormalities characteristic of Alzheimer's
disease (AD), according to new findings from the Religious
Orders Study, a major national study of aging. The research,
by investigators at Rush Presbyterian-St. Luke's
Medical Center in Chicago, Ill., offers important new
evidence that formal education may provide a cognitive "reserve" or
a "neuroplasticity" that can reduce the effect
of AD brain abnormalities on cognitive function in later
life.
"These findings give us additional insight into the long-known but not
well understood link between education and everyday memory and learning ability," notes
Neil Buckholtz, Ph.D., chief of the National Institute on Aging's (NIA)
Dementias of Aging Branch. "It may be that education permits the brain
already affected by the pathology of Alzheimer's disease to work around
that damage and allow an individual to function at a higher level."
The
findings are reported in the June
24, 2003, issue of Neurology by David A.
Bennett, M.D., and colleagues at Rush and at the University of Pennsylvania.
This analysis was supported by the NIA, part of the National Institutes
of Health at the U.S. Department
of Health and Human Services.
The
investigators examined physical characteristics of autopsied brains
of deceased participants in the Religious Orders Study,
a long-running prospective
study of aging and cognitive function. They also looked at the participants' years
of education and performance on tests of overall cognitive function before
death. Each of the 130 participants underwent cognitive testing about 8 months
before death. In those tests, 19 measures of cognitive function were used
to create a global cognitive function measure involving different forms of
memory,
perceptual speed, and "visuospatial" ability.
At
death, brains of the participants were examined to see how much
AD pathology, or damage,
was evident. Scientists noted the extent of different kinds of
amyloid plaques (which occur when snipped fragments of a larger protein
clump together)
and neurofibrillary tangles (which are formed when threads of the protein
tau become entangled, damaging critical neurons, or nerve cells, in the
brain).
In
this study, the relationship between the number of plaques and
cognitive performance changed with the level of education:
as people moved up the
educational ladder, the same number of plaques had less effect on cognitive
test scores.
To illustrate, the researchers offer an example of the cognitive scores
(on a scale where the average participant scores 100) of two people of
the same
age with the same level of plaques but with different levels of education.
An 84-year-old woman in the most highly educated group (equivalent to
postgraduate work after college) would score 98.1 in the absence
of any plaques; the same age woman in the study group with the
least education (equivalent to some college attendance) would score
96.8. In the presence
of about 18 plaques (more than the number required for a diagnosis of
AD), the
more highly educated woman's score would drop about two points,
to 96.2, while the score of the woman with less formal education would
drop more than
14 points, to 82. Therefore, the presence of a certain number of AD plaques
had less effect on cognition as educational level increased.
The
study did not find an association among neurofibrillary tangles – a
different pathological feature of AD – and increased education
and cognitive function.
Bennett
noted that the significant differences with education were found
in a population in which approximately 90
percent of the participants
had some
college education, ranging from a few years of undergraduate study
to
high levels of postgraduate work. Even more may be learned by investigating
the associations among education, cognition, and AD pathology in
a group of people
with a wider range of educational background and experience, he said.
Education "may
make the brain more adaptable and flexible, similar to what we have
seen demonstrated in experimental animals," Bennett theorizes.
In these previous studies, environments enriched with toys and mazes
were associated with building new connections among brain cells and
in some cases generating
new cells in the brains of mice.
More than 900 older Catholic clergy from about 40 groups across the
U.S. are part of the Religious Orders Study. The nuns, priests, and
brothers
participating in the research agree to annual clinical evaluations
during the study and
to
brain donation and autopsy upon their deaths. "We are grateful for the
remarkable dedication and altruism of this unique group of people," says
Bennett. "I expect we will learn a great deal more from them as we look
for insights into how the brain functions with age."
The
study is supported by the NIA, which leads the Federal effort to
support
and conduct basic, clinical, and social and behavioral
studies
on aging
and on AD. It supports the Alzheimer's Disease Education
and Referral (ADEAR) Center, which provides information on AD research.
ADEAR's website can
be viewed at www.alzheimers.org,
where several publications may be found on the causes and course
of AD, including the new publication Alzheimer's
Disease: Unraveling
the Mystery and the detailed Progress
Report 2000, which describes the broader NIH research program
on AD. The public and health professionals may also call ADEAR
toll-free at
1-800-438-4380.
Press
releases, fact sheets, and other materials about aging and aging
research can be viewed at the NIA's general
information website, www.nia.nih.gov.
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