October 20, 2008 — A high level of education and a mentally challenging job may reduce memory impairment and delay clinical expression of Alzheimer's disease (AD), suggesting the cognitive reserve hypothesis may extend to include amnestic mild cognitive impairment (aMCI).
A study of individuals with aMCI showed that although subjects with a high level of education and more intellectually demanding jobs had the same level of cognitive impairment as those with lower education/occupations, 2-[18F] fluoro-2-deoxy-D-glucose (FDG) positron-emission tomography (PET) imaging revealed their brains sustained significantly more damage.
"The theory is that education and demanding jobs create a buffer against the effects of dementia on the brain, or a cognitive reserve. Their brains are able to compensate for the damage, [allowing individuals] to maintain functioning in spite of damage," study author Valentina Garibotto, MD, from San Raffaele University and Scientific Institute and the National Institute of Neuroscience, in Milan, Italy said in a statement.
There are 2 possible explanations for this, she said. "The brain could be made stronger through education and occupational challenges. Or genetic factors that enabled people to achieve higher education and occupational achievement might determine the amount of brain reserve. However, it isn't possible to determine which accounts for our findings," she said.
The study is published in the October 21 issue of Neurology.
Cognitive Reserve Hypothesis Also Applicable in aMCI?
This concept, known as the cognitive reserve hypothesis, is based on the clinical observation in AD patients that high premorbid intelligence, education, and an active lifestyle significantly attenuate the impact of aging and disease on brain function.
In recent years, the hypothesis has been supported by imaging studies, showing that higher education is linked to more severe brain pathology in patients with AD. This includes several PET imaging studies, which have demonstrated a greater degree of impairment of regional cerebral metabolic activity and blood flow for a given level of dementia in highly educated patients.
However, it is not known whether a similar cognitive reserve mechanism is also at play in patients with aMCI, a condition thought to be a prodromal form of AD.
The aim of the current study was to assess the impact of education and occupation on regional cerebral metabolic rates for glucose (rCMRglc) using FDG-PET imaging in individuals with aMCI and those with probable AD.
The study included 242 subjects with probable AD, 72 with aMCI, and 144 healthy controls. Years of education were defined as the number of completed years of formal education, including university or apprenticeship.
Occupational attainment was determined according to a graduated rating scale of 1 to 6. A score of 1 ranked as "no occupation," while a score of 6 ranked as a "senior civil servant or management; senior academic position; self-employed with a high degree of responsibility."
All subjects underwent an extensive battery of neuropsychological tests to evaluate global cognitive impairment, memory, speed of information processing and executive functioning, visuoconstructive abilities, word fluency, and language comprehension.
In addition, participants underwent baseline FDG-PET scans to measure glucose metabolism. At an average follow-up of 14 months, 21 individuals with aMCI at baseline converted to AD and 51 remained stable.
Important Advancement of Earlier Work
The study showed a significant association between higher education/occupation and lower rCMRglc in the posterior temporoparietal cortex and precuneus in AD patients and those with aMCI who converted to AD. However, the investigators found no correlation in aMCI subjects who did not convert to AD compared with healthy controls.
According to the researchers, the results show individuals with aMCI and AD with higher education/occupation had more severe rCMRglc reduction than individuals with low education/occupation and comparable levels of cognitive impairment.
"The present findings are an extension and an important advancement of previous functional neuroimaging studies, indicating that highly educated subjects can cope better than less educated subjects with the same level of AD changes in the brain, maybe by recruiting alternative, or redundant, neural networks to support cognitive function," the authors write.
The authors report no disclosures.
Medscape Medical News © 2008 Medscape
Cite this: Caroline Cassels. High Education Level May Reduce Memory Impairment, Delay Onset of Alzheimer's Symptoms - Medscape - Oct 20, 2008.