Intelligence Predicts Health and Longevity, but Why?
Large epidemiological studies of almost an entire population in Scotland have found that intelligence (as measured by an IQ-type test) in childhood predicts substantial differences in adult morbidity and mortality, including deaths from cancers and cardiovascular diseases. These relations remain significant after controlling for socioeconomic variables. One possible, partial explanation of these results is that intelligence enhances individuals’ care of their own health because it represents learning, reasoning, and problem-solving skills useful in preventing chronic disease and accidental injury and in adhering to complex treatment regimens.
A Gottfredson pdf just full of useful bits of information about the influence of IQ on mortality. A few of the most interesting bits…
a drop of 1 standard deviation in IQ was associated with a 27% increase in cancer deaths among men and a 40% increase in cancer deaths among women (Deary, Whalley, & Starr, 2003). The effect was especially pronounced for stomach and lung cancers, which are specifically associated with low socioeconomic status (SES) in childhood.
For each standard deviation increase in IQ, there was a 33% increased rate of quitting smoking. Adjusting for social class reduced this rate only mildly, to 25%. Thus, childhood IQ was not associated with starting smoking (mostly in the 1930s, when the public were not aware of health risks), but was associated with giving up smoking as health risks became evident.
When all other variables were statistically controlled, each additional IQ point predicted a 1% decrease in risk of death. Also, IQ was the best predictor of the major cause of death, motor vehicle accidents. Vehicular death rates doubled and then tripled at successively lower IQ ranges (100–115, 85–100, 80–85; O’Toole, 1990).
Perhaps better nutrition and a stronger health foundation increase intelligence to reflect, rather than drive longevity.