Researchers find effects of Alzheimer's disease may be influenced by
education
June 24, 2003
The more education, the better memory and learning ability
Researchers at Rush-Presbyterian-St. Luke's Medical Center in Chicago
have found that 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).
New findings from the Religious Orders Study (ROS), a long-running
prospective study of aging and cognitive function in Catholic clergy, 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.
The research, published in the June 24, 2003, issue of Neurology by Dr.
David A. Bennett, Rush colleagues and researchers at the University of
Pennsylvania, examined physical characteristics of autopsied brains of
deceased participants in the Religious Orders Study. Bennett and colleagues
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).
Bennett found that 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," said Bennett.
To illustrate, take two women, same age, same level of plaques, but with
different levels of education. An 84-year-old woman in the most highly
educated group (postgraduate work after college) would score 98.1 (on a
scale where the average participant scores 100) in the absence of any
plaques. The same age woman with the least education (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 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."
"These findings give us additional insight into the long-known but not
well understood link between education and everyday memory and learning
ability," notes Dr. Neil Buckholtz, 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."
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 study 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."
Rush Presbyterian St. Luke's Medical Center
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