Intelligence and Parkinson's (1)

I did a cursory search for any correlation between Parkinson’s and intelligence when I asked the question Is There a Parkinson’s Personality? I wasn’t really expecting to find anything, and, indeed, I didn’t. However, a phrase in the article on increased artistic activity associated with dopaminergic therapy made me wonder about a related factor: the level of education.

“… With the only exception of a higher level of education, patients with PD did not differ from [Healthy Controls] in terms of any demographic variables.”

While it would be facile to suggest that a high level of education invariably indicates a similarly high level of intelligence, there is a tendency for the “cleverer” individuals to progress further along the academic path. And it is much simpler to measure someone’s level of education (leaving aside any suggestion that exams are getting easier) than it is their innate intelligence.

I was actually quite surprised to find several pertinent articles when I plugged “level of education parkinson’s” into Google. The most relevant one was a study at the Mayo Clinic in 2005, reported on by The Daily of the University of Washington, whose article opens with the bald statement:

The higher your level of education, the greater your risk of developing Parkinson’s disease

So… maybe we are more erudite than the population at large.

But it’s not a very pleasing result, all the same. We like to think of education as a Good Thing (well, I do). If it somehow increases your risk of getting Parkinson’s, then it becomes less good.

[The Mayo Clinic] study examined the occupations and educational levels of people who developed Parkinson’s in Minnesota between 1976 and 1995. A similar study conducted at Harvard found that people who work in jobs that are less physically demanding are more likely to develop Parkinson’s than people whose jobs demand a lot of sweat and muscle.

[...] Other studies have drawn similar conclusions, said [Dr. Walter Rocca, chief investigator of the research], pointing to analyses that found greater Parkinson’s risks among teachers and physicists.

This particular study (the abstract for which can be found here) actually found that physicians (i.e. doctors) were at most risk, along with those who had attained higher education. How much of this has to do with the amount of physical activity expended in these people’s occupations? Us overeducated types tend to sit around on our bottoms all day and type or talk to people, occasionally wandering down a corridor to fetch some small item or to see someone else. It seems well established that exercise is good for Parkies (there is even a suggestion that it may slow the progress of the condition), so it isn’t a great leap to start wondering if exercise can help you not get Parkinson’s in the first place. It might not be the level of education per se, but the type of job we do after we’ve left education. The Daily article continues:

But Dr. Michael Hutchinson, an associate professor of neurology at NYU School of Medicine in Manhattan, said there is another way of looking at lifestyle issues and Parkinson’s.

“When people find something that correlates, they tend to say: `Aha!’ But that correlation may be sheer chance,” Hutchinson said [...]“The problem with studies like these is that there might be other factors that are linked secondarily.”

For years, Hutchinson said, it has been known that smoking protects against Parkinson’s, and that smoking is more common among people with fewer years of education. “So there may be a genuine correlation between educational level and the incidence of Parkinson’s disease, but it may be hiding the real primary variable, which in this case may be smoking.”

Ah. Smoking, again. I don’t smoke. I’m a bit overeducated and I always worked at a desk (ignore the fact that I used to arrive there on a bicycle). Obviously, I’m high risk for Parkinson’s…

But remember this?

[...] patients with PD are less likely than controls to be smokers. It has been suggested that nicotine and its byproducts are not actually protective against PD, and it could be postulated that higher-than-average intrinsic dopamine may facilitate addiction. Smoking for the patient who is later to develop PD may be particularly unrewarding.

“Is there a premorbid personality typical for Parkinson’s disease?”
George W. Paulson, MD and Nahid Dadmehr, MD
Neurology May 1, 1991 vol. 41 no. 5 Suppl 2 73-76

(quoted in Is There a Parkinson’s Personality?)

Which is cause and which effect?

I think it takes more than a modicum of intelligence and a bit of education to answer that one*.

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* Although, personally, I would like the answer not to include smoking being, in any way, good for you.

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