IQ and Life Expectancy

I saw this going viral Why do those with higher IQs live longer? A new study points to answers

Among the thousands of people studied, those in the top 10 percent of childhood intelligence were two-thirds less likely to have died from respiratory disease by age 79 than people in the bottom 10 percent. They were half as likely to have died from heart disease, stroke, smoking-related cancers, digestive diseases, and outside causes such as injury.

“The increased risk of dying earlier from many different causes is not just about low versus high IQ scores,” said Ian Deary, a psychologist at the University of Edinburgh and the senior author of the paper. “The slight benefit to longevity from higher intelligence seems to increase all the way up the intelligence scale, so that very smart people live longer than smart people, who live longer than averagely intelligent people, and so on.”

The big question is how much of this attributable to genetic factors vs. environmental. That is, does having high IQ confer some resistance to early death that cannot be explained by environment. The answer, unfortunately, is likely not. After controlling for lifestyle diseases and risks (such as occupational injury, smoking, alcoholism, etc.), high intelligence does not protect against Alzheimer’s disease or cancers that may not be attributable to lifestyle (such as liver cancer and alcoholism or lung cancer and smoking).

According to a large study of participants in Sweden, having a high IQ doesn’t reduce incidence of cancer after a 20-year follow up, after controlling for environmental factors. They also found a positive link between IQ and skin cancer, which persists even after socioeconomic status is controlled for.

Results: During an average of 19.5 years of follow-up, there were 10 273 new cancer cases. IQ showed few associations with the cancer end points studied. There was a suggestion that IQ was positively associated with lung cancer, and inversely related to stomach, oesophageal and liver malignancies, although effects were modest. The only robust gradient was found for IQ in relation to skin cancer (HRper one standard deviation advantage in IQ; 95% confidence interval 1.18; 1.13, 1.24; P value for trend across categories: <0.01), which was attenuated but retained statistical significance after adjustment for indices of socioeconomic position across the life course.

In the present study of almost one million men who were well characterised for IQ, socioeconomic position and cancer, we examined the relation of IQ to 21 separate cancer outcomes (20 of which were noninclusive). In general, there was limited evidence of a link between IQ and these malignancies. One exception was the IQ–skin cancer relationship where increased rates of this neoplasm were evident in the higher IQ-scoring men. In Sweden, and elsewhere, elevated rates of this skin cancer have also been reported in the socioeconomically advantaged relative to the less affluent [30], and in the highly educated relative to persons with basic credentials [31].

Same for Alzheimer’s…having a high IQ may mask the symptoms, but it does not prevent the development of the disease itself.

I have always been sorta skeptical of the purported link between IQ and life expectancy, especially for exceptional IQ and after controlling for obvious risk factors. Indeed, if you look at the biographies of famous scientists they don’t seem to live exceptionally long. Feynman, Neumann, Segan, Oppenheimer, Szilard, Fermi, etc. all died in their 50s or 60s. Even Einstein died at 76, a very unremarkable age for an otherwise remarkable mind. There are some exceptions, like Edward Teller, who lived to 95, and Hans Bethe, who lived to 99. Science careers tend to be short anyway and dominated by the young, so it’s not like you need to live to a very long age to produce important work, unlike in the arts, in which top authors and painters can keep cranking out important, influential work until death.

If the difference between a top 5% IQ and an average IQ is maybe a year of additional average life expectancy, then obviously we can expect a lot of people who are smart to fall below the average.

Conversely, if you look at the biographies of people who lived the longest, they do not seem exceptionally smart either. It’s like “I ate chocolates everyday and went to the park,” not “I worked with Einstein” or “I helped develop quantum mechanics” or anything like that. It does speak to a sort of unfairness that someone as smart and productive as John von Neumann had his life cut short at 53. Or maybe that was a blessing in disguise given that he had been pressing for a preemptive nuclear attack on Russia.