Alzheimer's Decline Delayed but more Rapid for the Educated
> 10/29/2007 2:08:22 PM

Earlier this month, a Finnish study in Neurology firmly established the link between Alzheimer's Disease (AD) and education level. Compared to the lower education group, the medium education group had a 40% lower risk of developing AD, and the high education group had an 80% lower risk. This link held even when factors like nutrition, income, and exercise were taken into account. These large differences prompted researchers to declare that education protects against AD, but a newer article in this week’s issue of the same journal hints that the relationship between education and AD is more complex than simple protection.

The problematizing research comes from an aging study at the Albert Einstein College of Medicine. The Einstein study followed 117 subjects and found a protective effect somewhat similar to that found in the Finnish study; each extra year of education delayed the onset of rapid cognitive decline by .21 years. However, the more highly educated subjects actually suffered a more precipitous drop in function once their cognitive decline became noticeable. Their rate of decline on the Buschke Selective Reminding Test increased by .1 points for every extra year of education.

The dark flip-side of education protection suggests the possibility that education does not actually reduce the risk of AD, but rather postpones the onset of noticeable symptoms. Because the risk of AD rises sharply for every year after age 65, many highly educated people may be dying before their AD becomes apparent. This could mean that while the cognitive decline curves of uneducated and educated people are shaped differently, they would end up at roughly the same amount of neural damage over a long period of time. In addition to the question about decline curve shape, there is the debate over whether education slows neural damage or just the cognitive impairment that can  come from neural damage. It is possible that education shores up the brain’s defenses temporarily, but that this protection exhausts some system that eventually breaks down entirely and allows accelerated decline. Alternatively, educated people may lose neurons all along but not exhibit impaired cognition as quickly.

The theory that educated people are able to better compensate for neural damage relies upon the idea of a “Cognitive Reserve”. The cognitive reserve is assumed to be either a large amount of extra capacity or a flexibility formed by learning a variety of ways to think. A reserve of extra capacity would allow AD sufferers to keep performing normally on all but the most taxing tasks. A more flexible array of alternative pathways would allow the AD sufferer to find one way to perform a task even as other pathways degenerate.

The cognitive reserve theory is plausible and has the support of many researchers in the AD field, including the authors of the Einstein study, but further research is required. In the meantime, the practical implications of the different shapes of cognitive decline curves need to be addressed. Well-educated elderly citizens should be more vigilant for signs of even small decline. It is not sufficient for them to watch for large gaps in memory, because by the time extreme symptoms manifest there will be a very short window before incapacitating dementia and then death. This rapid mental descent can be devastating for the sufferers and their families if they are not adequately prepared.

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