Link between intelligence and longevity is mostly genetic.
The tendency of more intelligent people to live longer has been shown, for the first time, to be mainly down to their genes by new research published in the International Journal of Epidemiology.
By analysing data from twins, researchers found that 95 per cent of the link between intelligence and lifespan is genetic.
They found that, within twin pairs, the brighter twin tends to live longer than the less bright twin and this was much more pronounced in fraternal (non identical) twins than in identical twins.
Studies that compare genetically identical twins with fraternal twins – who only share half of their twin’s DNA – help distinguish the effects of genes from the effects of shared environmental factors such as housing, schooling and childhood nutrition.
Rosalind Arden, a research associate at the London School of Economics and Political Science (LSE), said: “We know that children who score higher in IQ-type tests are prone to living longer. Also, people at the top of an employment hierarchy, such as senior civil servants, tend to be long-lived. But, in both cases, we have not understood why.
“Our research shows that the link between intelligence and longer life is mostly genetic. So, to the extent that being smarter plays a role in doing a top job, the association between top jobs and longer lifespans is more a result of genes than having a big desk.
“However, it’s important to emphasise that the association between intelligence and lifespan is small. So you can’t, for example, deduce your child’s likely lifespan from how he or she does in their exams this summer.”
The researchers looked at three different twin studies from Sweden, the United States and Denmark where both intelligence and age of death was recorded, and where at least one twin in each pair had died. Only twins of the same sex were included in the analysis.
On the reasons for the findings, Rosalind Arden said: “It could be that people whose genes make them brighter also have genes for a healthy body. Or intelligence and lifespan may both be sensitive to overall mutations, with people with fewer genetic mutations being more intelligent and living longer. We need to continue to test these ideas to understand what processes are in play.”
This is the first study to test for a genetic association between intelligence and lifespan.
Source: Sue Windebank – London School of Economics
Image Credit: The image is in the public domain
Original Research: Full open access research for “The association between intelligence and lifespan is mostly genetic” by Rosalind Arden, Michelle Luciano, Ian J Deary, Chandra A Reynolds, Nancy L Pedersen, Brenda L Plassman, Matt McGue, Kaare Christensen and Peter M Visscher in International Journal of Epidemiology. Published online July 26 2015 doi:10.1093/ije/dyv112
Abstract
The association between intelligence and lifespan is mostly genetic
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.
“The association between intelligence and lifespan is mostly genetic” by Rosalind Arden, Michelle Luciano, Ian J Deary, Chandra A Reynolds, Nancy L Pedersen, Brenda L Plassman, Matt McGue, Kaare Christensen and Peter M Visscher in International Journal of Epidemiology. Published online July 26 2015 doi:10.1093/ije/dyv112
