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Rush researchers find effects of Alzheimer's disease may be influenced by education
Researchers at Rush-Presbyterian-St. Luke's Medical Center 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).
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."