"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 at http://www.