August 22nd, 2006

ozarque figure

Well, Virginia, is there really such a thing as "cognitive reserve"?

Recently Frances Green sent me an article by Lisa Melton titled "Use it don't lose it" [so help me, that's how it's punctuated], from pp. 32-35 of the December 17, 2005 issue of New Scientist. I've stopped assuming that New Scientist articles are always trustworthy -- for example, a recent article on the Piraha controversy said flat out that most linguists now accept the Sapir-Whorf hypothesis as valid, which is wildly inaccurate -- but I do tend to put more faith in New Scientist's information about science than I do in that provided by most popular science publications. If the conclusions in this article are accurate, it's worrisome; it imposes a whole new interpretation on a number of very serious issues.

The article opens with an account of a man whose only sign of mental impairment was that he couldn't think as many moves ahead when he played chess as he had been able to in earlier life. But when he suddenly died, his autopsy revealed evidence of Alzheimer's disease at so advanced a level that it "would have reduced most people to a state of total confusion." (page 32) This man, Melton says, is an example of a puzzling phenomenon -- the strong evidence that people who are better educated, who are in high-status occupations, who lead more intellectually stimulating lives, are somehow shielded from the typical manifestations of Alzheimer's and other dementias in old age. It's not that they don't get these dementias, they do; and once they start showing symptoms of dementia they decline -- and die -- rapidly. But the symptoms don't appear until they are in the very last stages of the disease. Of the man mentioned previously, epidemiologist Michael Marmot says, on page 34: "By the time he couldn't dress himself he would have been at death's door."

The name given to whatever-this-is is "cognitive reserve," defined in the article as the ability -- when ordinary brain pathways are unavailable because of factors such as plaques and tangles and debris in the brain -- to "recruit," and switch to, alternate pathways. And we're told on page 35 that "building cognitive reserve is a lifetime enterprise, and the earlier we start the better."

Finally, on page 35 the article describes research demonstrating that physical exercise also has a "remarkable effect" on mental performance.

When I put this all together, the implications in these United States -- if it's all true -- are distressing. Worse than distressing. We have an education system so badly broken that the slogan "No Child Left Behind" is no more than a bad joke, with an ever-increasing dropout rate, especially in minority populations other than Asian-Americans. We have an ever-growing lack of respect for intellectuals and intellectual pursuits. We have a set of overlapping constraints that stand between the poor (and lower middle class) population and physical exercise. We have widespread inadequate nutrition for pregnant women and for children younger than two years of age that seriously endangers those children's brains and depresses intelligence.

I went googling, looking for the kind of media attention that it seemed to me this research deserved -- a call for immediate emergency measures to start building cognitive reserve in our children. I didn't find it. I found quite a few scholarly papers and highly intellectual news articles that discuss the research and make soothing noises along the lines of "oh, we need far more evidence before we accept this cognitive reserve hypothesis and this mental exercise/physical exercise hypothesis." Which strikes me as very convenient indeed, since accepting the hypotheses and taking them seriously would mean actually doing something about the problems of early education and early nutrition. I'm not alleging any kind of conspiracy, mind -- just a standard denial-response to what looks like an inconveniently intractable problem. It would be far more convenient, especially for those already equipped with a robust cognitive reserve, for that research to be flawed and ignorable.

The Melton article isn't available online unless you're a subscriber to the print edition of New Scientist, but here are a few items you could look at if you want to read typical material available on the subject:

1. "Educating the Brain to Avoid Dementia: Can Mental Exercise Prevent Alzheimer Disease?," by Margaret Gatz, at http://medicine.plosjournals.org/perlserv?request=get-document&doi=10.1371/journal.pmed.0020007 .

2. RE: "Relation of Education and Occupation-based Socioeconomic Status to Incident Alzheimer's Disease," by
G. David Batty et al., at http://aje.oxfordjournals.org/cgi/content/full/160/4/404?ijkey=6f5eab269f0fe75c664964368e399f238039f40c&keytype2=tf_ipsecsha .

3. "Physical Activity and Risk of Cognitive Impairment in Elderly Persons," by Danielle Laurin et al., at http://archneur.ama-assn.org/cgi/content/abstract/58/3/498 .