At first, when an association was found between IQ and lifespan, many plausible reasons came to mind. Brighter people, it was argued, were the first to heed health warnings, adopt healthy life styles, read the medicine instructions carefully, and avoid putting their tender parts in meat grinders. All this is true. Brighter people stop smoking sooner than others, don’t get into so many accidents, and so on.
However, part of the IQ/lifespan links when you control for simple reaction times in middle to late age, suggesting there are underlying systems in common. If you are blessed with a good system, and have “system integrity” (a hypothetical construct dreamed up by Ian Deary when he looked at the first sets of data) then you also get the benefit of a healthy body and a longer life. Mens sana in corpore sano indeed.
Now Arden and team have found a genetic link to the overlap between intelligence and lifespan. Fingers crossed for all my (highly intelligent) readers.
THE ASSOCIATION BETWEEN INTELLIGENCE AND LIFESPAN IS MOSTLY GENETIC
Rosalind Arden1 , Michelle Luciano2 , Ian J Deary2 , Chandra A Reynolds3 , Nancy L Pedersen4 , Brenda L Plassman5 , Matt McGue6,7 , Kaare Christensen8 , Peter M Visscher9
1 CPNSS London School of Economics, email@example.com.
2 University of Edinburgh,
3 University of California, Riverside,
4 Department of Medical Epidemiology and Biostatistics Karolinska Institutet Stockholm, Sweden.
5 Department of Psychiatry and Behavioral Sciences Duke University Medical Center, Durham, NC.
6 Department of Psychology, University of Minnesota.
7 The Danish Aging Research Center, University of Southern Denmark.
8 The Danish Twin Registry and Te Danish Aging Research Center University of Southern Denmark, Odense, Denmark.
9 Queensland Brain Institute The University of Queensland Diamantina Institute, Translational Research Institute (TRI) Woolloongabba, QLD 4102 Australia.
Several studies in the new field of cognitive epidemiology have shown that higher intelligence predicts longer lifespan. This positive correlation might arise from socio-economic status influencing both intelligence and health; intelligence leading to better health behaviors, and/or some shared genetic factors influencing both intelligence and health. Distinguishing among these hypotheses is crucial for medicine and public health, but can only be accomplished by studying a genetically-informative sample.
We analyzed data from three genetically-informative samples containing information on intelligence and mortality: 1) 377 pairs of male veterans from the NAS-NRC US World War II Twin Registry, 2) 246 pairs of twins from the Swedish Twin Registry and 3) 784 pairs of twins from the Danish Twin Registry. The age at which intelligence was measured differed between the samples.
We used three methods of genetic analysis to examine the relationship between intelligence and life-span: we calculated the proportion of the more intelligent twins who out-lived their co-twin; we regressed within-twin-pair life-span differences on within-twin pair intelligence differences; and we used the resulting regression coefficients to model the additive genetic covariance.
The combined (and all three individual samples) showed a small positive phenotypic correlation between intelligence and lifespan. In the combined sample observed r=.12 (95% confidence interval .06 to .18). The additive genetic covariance model supported a genetic relationship between intelligence and lifespan. In the combined sample the genetic contribution to the covariance was 95%; in the US study, 84%; in the Swedish study, 86%, and in the Danish study, 85%. The finding of common genetic effects between lifespan and intelligence has important implications for public health and those interested in the genetics of intelligence, lifespan or inequalities in health outcomes including lifespan.