Link between intelligence and longevity is mostly genetic.
New research published in the International Journal of Epidemiology demonstrates that the observed tendency for people with higher intelligence to live longer is largely explained by genetic factors. By analysing data from multiple twin registries, researchers conclude that roughly 95% of the association between intelligence and lifespan can be attributed to shared genetics, rather than to socio-environmental conditions alone.
The study compared patterns within twin pairs and found that, more often than not, the twin with the higher intelligence score outlived their co-twin. This pattern was most clear when comparing fraternal (dizygotic) twins—who share about half of their segregating genes—with identical (monozygotic) twins, who are genetically identical. Such comparisons are fundamental in separating genetic effects from shared environmental influences like housing, schooling and childhood nutrition.
Rosalind Arden, a research associate at the London School of Economics and Political Science (LSE) and a lead author on the study, explained that previous work in cognitive epidemiology had already shown a link between higher childhood cognitive test scores and longer adult lifespan, and that higher-status occupations are also associated with longer life. What this new analysis adds is evidence that the common thread connecting intelligence and longevity is primarily genetic, not simply the result of occupying higher-status jobs or having better early-life environments.
Arden cautioned that the magnitude of the association is small. She emphasised that intelligence is only one modest predictor of lifespan and that individual outcomes cannot be reliably predicted from a single test score. Factors such as healthcare, lifestyle choices, and chance also play important roles in determining a person’s lifespan.
The researchers combined data from three genetically informative samples: male veteran twin pairs from the NAS-NRC US World War II Twin Registry, same-sex twin pairs from the Swedish Twin Registry, and same-sex twin pairs from the Danish Twin Registry. Each dataset included measurements of intelligence and documented ages at death for at least one twin in each pair. Using three complementary genetic-analytic approaches, the team assessed whether the more intelligent twin tended to outlive the less intelligent twin, examined how within-pair differences in intelligence related to within-pair differences in lifespan, and modelled the additive genetic covariance between intelligence and lifespan. Results were then meta-analysed across the three samples.
Across the combined sample the observed phenotypic correlation between intelligence and lifespan was small but consistent (r = 0.12, 95% confidence interval 0.06 to 0.18). Crucially, genetic modelling indicated that the covariance between intelligence and longevity was overwhelmingly genetic in origin: the combined-sample estimate attributed about 95% of that covariance to additive genetic factors. The individual samples produced similar estimates, with genetic contributions in the range of approximately 84% to 86%.
Several plausible explanations could account for these findings. One possibility is pleiotropy: the same genetic variants that influence cognitive ability may also influence physiological processes that protect health and reduce mortality risk. Another possibility is that a lower burden of deleterious mutations promotes both higher intelligence and longer lifespan. The authors stress that further research is needed to clarify the biological pathways and mechanisms linking cognitive function with longevity.
The study is the first to directly test a genetic association between intelligence and lifespan using multiple twin cohorts and genetic covariance modelling. Its conclusions carry implications for public health and for research into the genetics of intelligence, ageing, and health inequalities. While genetics appear to account for most of the observed link, environmental, social and behavioural factors remain important determinants of individual health outcomes and life expectancy.
Source: Sue Windebank – London School of Economics
Image Credit: Public domain (illustrative image)
Original Research: “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 the International Journal of Epidemiology. Published online July 26, 2015. DOI: 10.1093/ije/dyv112
Abstract (summary)
Background: Prior studies in cognitive epidemiology have established that higher intelligence predicts longer lifespan. Potential explanations include socioeconomic effects, health behaviours linked to intelligence, and shared genetic influences. This study used genetically informative twin samples to distinguish these mechanisms.
Methods: Data from three twin registries were analysed using three genetic-analysis approaches: counting the proportion of more-intelligent twins who outlived their co-twins, regressing within-pair lifespan differences on within-pair intelligence differences, and modelling additive genetic covariance. A meta-analysis combined results across samples.
Results: A small positive phenotypic correlation between intelligence and lifespan was observed. Genetic modelling indicated a predominant genetic contribution to the covariance between intelligence and lifespan, with combined-sample estimates attributing approximately 95% of the covariance to genetic factors.
Conclusions: The association between intelligence and longevity appears largely driven by shared genetic influences. These findings are relevant for public health, for researchers studying the genetics of cognition and ageing, and for understanding health inequalities related to lifespan.