title: The association between intelligence and lifespan is mostly genetic.
abstract: 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.
authors.affiliation: Centre for Philosophy of Natural & Social Science, London School of Economics, London, UK, Genetic Epidemiology, Queensland Institute of Medical Research, Brisbane, QLD, Australia, arden.rosalind@gmail.com.
authors.forename: Rosalind
authors.initials: R
authors.lastname: Arden
authors.affiliation: Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK, arden.rosalind@gmail.com.
authors.forename: Michelle
authors.initials: M
authors.lastname: Luciano
authors.affiliation: Centre for Cognitive Ageing and Cognitive Epidemiology, University of Edinburgh, Edinburgh, UK.
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Deary
authors.affiliation: Department of Psychology, University of California, Riverside, CA, USA.
authors.forename: Chandra A
authors.initials: CA
authors.lastname: Reynolds
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Nancy L
authors.initials: NL
authors.lastname: Pedersen
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Duke University Medical Center, Durham, NC, USA.
authors.forename: Brenda L
authors.initials: BL
authors.lastname: Plassman
authors.affiliation: Department of Psychology, University of Minnesota, Minneapolis, MN, USA, Danish Ageing Research Center, University of Southern Denmark, Odense, Denmark.
authors.forename: Matt
authors.initials: M
authors.lastname: McGue
authors.affiliation: Danish Ageing Research Center, University of Southern Denmark, Odense, Denmark, Danish Twin Registry, University of Southern Denmark, Odense, Denmark and.
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
authors.affiliation: Queensland Brain Institute, University of Queensland Diamantina Institute, Translational Research Institute, Woolloongabba, QLD, Australia.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Visscher
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D007360:Intelligence / Q000235:genetics*; D008017:Life Expectancy; D008297:Male; D015201:Meta-Analysis as Topic; D008875:Middle Aged; D012042:Registries; D012044:Regression Analysis; D012727:Sex Characteristics; D012959:Socioeconomic Factors; D013548:Sweden / Q000453:epidemiology; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics; D014481:United States / Q000453:epidemiology; D014728:Veterans