Another reason your dad was right that you should stay in school

This study is interesting. Published last December in the Archives of Physical Medicine and Rehabilitation, it looked at cognitive performance of people who had suffered a traumatic brain injury (TBI). A TBI is basically any injury to the brain that results from externally applied physical forces, as would happen, for example, in a car accident. The study, authored by James Sumowski, Nancy Chiaravalotti, Denise Krch, Jessica Paxton and John DeLuca, examined a variable that might partially account for why impacts of TBIs on cognitive ability can be so variable from one case to another. It’s well known in TBI circles that it’s difficult to predict, simply on the basis of the type or extent of a brain injury, just how much the injury will affect subsequent cognitive functioning.

The variable the authors examined was the number of years of schooling the individual had undergone prior to the injury. The number of years of schooling is what is known as a “proxy variable”, that is, a variable that’s assumed to reflect another variable indirectly. In the case of educational attainment, what researchers think they’re measuring is the amount of intellectual stimulation a person has received in his or her lifetime—and that’s a reasonable assumption, provided she didn’t study fine arts. Okay, okay, don’t be so touchy; I was just kidding! Anyway, what the authors were interested in was a phenomenon that’s already known in research on other conditions, namely, the fact that people with more years of education seem to have brains that are more resistant to the performance-degrading impacts of various diseases or illnesses. The most striking of these is Alzheimer’s Disease, for which it’s been well documented that people with more education tend to be spared partially or totally from dementia, despite their brains on autopsy being riddled with the same Alzheimer’s pathology that is assumed to cause the cognitive decline in other people. The term for this seemingly greater resilience characterizing better-educated brains is cognitive reserve. The researcher whose excellent work is most associated with the construct of cognitive reserve is Yaakov Stern, of Columbia University in New York.

So, most of the work on cognitive reserve has shown that people with more years of education are more resistant to the onset of dementia in old age. The researchers in the current study looked at whether the same would be the case for people who had suffered a TBI. To examine this question, they compared the cognitive performances of a group of 44 TBI sufferers, on average about a year after their injury, to a group of normal, healthy control subjects. All of the participants completed a group of cognitive tests measuring processing speed, working memory (the ability to hold information in a highly active state while using it), and episodic memory (the ability to remember events that have happened to you). These were chosen because they’re among the most consistently impaired functions following a TBI. The three tests were summarized into a single performance score, and then the joint impact of TBI status and educational attainment (expressed as number of years of schooling) on this score was tested.

The results clearly showed that, although the TBI patients performed significantly worse on the cognitive tests than the controls (not a surprising finding), those who had more years of schooling were not impaired as badly as those who had fewer years of schooling. The following figure taken from the study illustrates this difference. The red dots represent members of the TBI group, and the blue dots, members of the control group:

In fact, it’s clear from the graph that if a person had had, say, 25 years of schooling, he would perform better after a TBI than before! Okay, not really. That was a joke. But it is a pretty interesting indication of how the extensive and varied intellectual experiences that accompany higher education can actually be not only personally enriching, but also neurologically protective.

I find the concept of cognitive reserve to be fascinating, because it’s one case in which there’s a clear crossing-over between what we normally think of as mind/psychology on the one hand, and brain/neurology on the other. What the study suggests is that educational experiences not only change your psychology, but also change the physical stuff of your brain, in a way that is strikingly evident as (relatively) spared functioning following a physical injury. Cool, huh? See, I knew it was worth it to stay in school for that long!

Leave a Reply