A long suffering toiler in the groves of academe writes in to say that, rather than just bemoaning the lack of intelligence and personality measures in epidemiology, I should pay some attention to a study which has done precisely that, and help boost the visibility of such work in the health literature. In fact, I have a vague recollection of the paper, but now is the time to make amends for my forgetfulness.
Bryan Pesta apologizes for the “ghastly” link below, but it is free, folks, so just copy and paste into the search bar.
By way of background, to the external world the USA is a monolith with some minor regional variations. To its citizens is a union of sovereign states, and all the better for it when that union is not too close. Pesta, Bertsch,McDaniel, Mahoney and Poznanski (Intelligence 40 (2012) 107–114) have gathered data on all 50 American states, have found a link between IQ and neuroticism measures and health variables, and have tried to tease out possible causal links.
They found that at the State level, drinking alcohol correlates positively with exercising and eating fruits and vegetables; and it correlates negatively with rates of smoking and many chronic diseases. These data are consistent with a growing but mixed literature showing that alcohol consumption correlates inversely with chronic disease rates. This may be nothing to do with ethanol as such, but we should follow the tradition of results first, explanations later.
The authors work through the key data using multiple regression.
At Step 1, the linear combination of IQ and N alone explained 57% and 61% of the variance in Chronic Disease and Metabolic Syndrome, respectively. Both IQ and N remained significant (but attenuated) predictors of disease, after entering Health Behaviors at Step 2. Not surprisingly, Health Behaviors itself explained large amounts of variance (over IQ and N) in both Chronic Disease and Metabolic Syndrome. Note that the variance explained at Step 2 is unusually large for social science research. Fully 80% of the variance in Chronic Disease (77% in Metabolic Syndrome) was explained by the combination of IQ, N and Health Behaviors.
The size of the effects here, though, could exemplify the "high resolution" that aggregate-level data offer, relative to studies that use individuals. At Step 3 they found that IQ (Beta=−.18), N (Beta=.35) and Health Behaviors (Beta=
−.53) all remained significant as predictors of chronic disease, even after controlling for state income (Beta=−.12, ns).
Here are the correlations between IQ and :
Health Behaviours .45
Chronic disease −.51
Metabolic syndrome −.53 C
So, here we have a nice clean study, admittedly at State level (aggregated data) which shows the importance of IQ and Neuroticism in influencing health outcomes. Why has this engaging study only been cited once? It may be that the intelligence literature is not read by epidemiologists. Another problem may be the title: “Differential epidemiology: IQ, neuroticism, and chronic disease by the 50 U.S. states”. It is accurate but dull, and hardly worth tweeting about in its current form. I think that the Pesta gang need to get with the spirit of the age, and re-issue it with a snappier, media friendly title:
Dull worriers die sooner: Avoid West Virginia.
Disclaimer: I am sure that the denizens of West Virginia are bright and stable people. It was just a suggestion.