Wednesday, July 29, 2015
A syndrome of general biological fitness appears again
I have been pointing out for many years that there seems to be a syndrome of general biological fitness -- such that high IQ people are healthier, live longer and have better emotional balance. High IQ, in other words, is just one part of general bodily good functioning. The recent study below is another indicator of such an association and goes on to show that the link is genetic. Some people are just born healthier and fitter. If so, all your bits work well -- including your brain, which is just another bodily organ. A wise man from long ago knew that. He said: "For he that hath, to him shall be given: and he that hath not, from him shall be taken even that which he hath." (Mark 4: 25). "All men are equal" exists neither in the Bible nor in life
The association between intelligence and lifespan is mostly genetic
By Rosalind Arden et al.
Background: Several studies in the new field of cognitive epidemiology have shown that higher intelligence predicts longer lifespan. This positive correlation might arise from socioeconomic status influencing both intelligence and health; intelligence leading to better health behaviours; 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.
Methods: We analysed data from three genetically informative samples containing information on intelligence and mortality: Sample 1, 377 pairs of male veterans from the NAS-NRC US World War II Twin Registry; Sample 2, 246 pairs of twins from the Swedish Twin Registry; and Sample 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 lifespan: we calculated the proportion of the more intelligent twins who outlived their co-twin; we regressed within-twin-pair lifespan differences on within-twin-pair intelligence differences; and we used the resulting regression coefficients to model the additive genetic covariance. We conducted a meta-analysis of the regression coefficients across the three samples.
Results: 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%.
Conclusions: The finding of common genetic effects between lifespan and intelligence has important implications for public health, and for those interested in the genetics of intelligence, lifespan or inequalities in health outcomes including lifespan.
Posted by John J. Ray (M.A.; Ph.D.).