Dec 13, 2008
Given the growing media coverage mentioning the terms Cognitive Reserve and Brain Reserve, you may be asking yourself, “What exactly is my Cognitive (or Brain) Reserve?”
The cognitive reserve hypothesis, tested in multiple studies, states that individuals with more cognitive reserve can experience more Alzheimer’s disease pathology in the brain (more plaques and tangles) without developing Alzheimer’s disease symptoms.
How does that work? Scientists are not sure but two possibilities are considered.
1. One is that more cognitive reserve means more brain reserve, that is more neurons and connections (synapses) between neurons. Individuals with more synapses would then have more synapses to lose before the critical threshold for Alzheimer’s Disease is reached.
2. Another possibility is that more cognitive reserve means more compensatory processes. The brain of individuals with more cognitive reserve would use more alternative networks to compensate for the damages caused by the pathology in previously used networks.
In a newly published study, Roe and colleagues from Washington University in St. Louis, used the number of years of education as a measure of cognitive reserve. Why years of education? Because previous studies have shown that people who have more education also exhibit a greater resistance to Alzheimer’s symptoms, even while pathological changes are occurring in the brain (see Bennett el al., 2003 or Roe, Xiong, et al., 2008).
Roe and her colleagues studied 198 individuals whose mean age was 67. Out of these 198 individuals, 161 were nondemented and 37 were diagnosed with Alzheimer’s Disease.
All the participants in the study took a 1.5h battery of tests to evaluate their cognitive functioning. They also underwent a PiB PET scan. This brain-imaging technique uses a marker called carbon 11-labeled Pittsburgh Compound B (PiB). The marker binds to beta-amyloid plaques in the brain and can be seen on a positron emission tomography (PET) scan.
Statistical tests were used to assess how the number of plaques in the brain, clinical and behavioral measures, and cognitive reserve interacted.For participants who had a large amount of plaques in the brain, performance on several cognitive tests increased with increasing education. This relationship was not observed for individuals with a lower amount of plaques in the brain.
These cognitive tests included the Mini Mental State examination, the Short Blessed test and the Clinical Dementia scale, which are all used to diagnose dementia. What does that mean? This means that individuals with greater education maintain better cognitive functioning in the presence of Alzheimer’s Disease pathology. This new study confirms the idea that cognitive reserve (here measured in terms of years of education) influences the relationship between cognitive functioning and amount of Alzheimer’s pathology.
It also raises several questions:
– How many years of education does one need to be “protected”?
In the studies published so far individuals with high levels of education were individuals who had 15 years or more of education. Little is known about the effect of lower levels of education.
-Are years of education the only measure of cognitive reserve?
No. Other indicators include a challenging occupation, engaging hobbies and active social networks. As you can guess, years of education are easier to objectively measure, which may explain why they are used more often in studies of cognitive reserve.
– Does it mean that if one doesn’t have a high education level, it is too late, there is nothing that one can do?
No! As described above, cognitive reserve can be measured in other ways. This means that people who are not highly educated but live a stimulating life and are active socially can still get some neuroprotection.
– Bennett, D. D., Wilson, R. S., Schneider, J. A. et al. (2003). Education modifies the relation of AD pathology to level of cognitive function in older persons. Neurology, 60, 1909-1915.
– Roe, C. M., Mintun, M. A., D’Angelo, G., Xiong, C., Grant, E. A., & Morris, J. C. (2008). Alzheimer Disease and cognitive reserve. Archives of Neurology, 65, 1467-1471.
– Roe, C. M., Xiong, C., Miller, J. P., Caims, N. J., & Morris, J. C. (2008). Interaction of neuritic plaques and education predicts dementia. Alzheimer Dis. Assoc. Disord., 22, 188-193.
— This article was written by Pascale Michelon, Ph. D., for SharpBrains. Dr. Michelon has a Ph.D. in Cognitive Psychology and has worked as a Research Scientist at Washington University in Saint Louis, in the Psychology Department. She conducted several research projects to understand how the brain makes use of visual information and memorizes facts. She is now an Adjunct Faculty at Washington University, and teaches Memory Workshops in numerous retirement communities in the St Louis area.