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Childhood socio-economic status modifies the association between intellectual abilities at age 20 and mortality in later life
  1. Eero Kajantie1,*,
  2. Katri Raikkonen2,
  3. Markus Henriksson3,
  4. Tom Forsén2,
  5. Kati Heinonen2,
  6. Anu-Katriina Pesonen2,
  7. Jukka T Leskinen4,
  8. Ilmo Laaksonen5,
  9. Maria Paile-Hyvarinen1,
  10. Clive Osmond6,
  11. David JP Barker6,
  12. Johan G Eriksson2
  1. 1 National Institute for Health and Welfare, Finland;
  2. 2 University of Helsinki, Finland;
  3. 3 National Supervisory Authority for Welfare and Health, Helsinki, Finland;
  4. 4 National Defence College, Finnish Defence Forces, Helsinki, Finland;
  5. 5 Centre for Military Medicine, Finnish Defence Forces, Lahti, Finland;
  6. 6 University of Southampton, Finland
  1. Correspondence to: Eero Kajantie, National Institute for Health and Welfare, Mannerheimintie 166, Helsinki, 00300, Finland; eero.kajantie{at}helsinki.fi

Abstract

Background: People who score poorly in intellectual ability tests have shorter life expectancy. We studied whether this association is different in people from different socio-economic backgrounds.

Methods: We studied the mortality of 2786 men born in Helsinki, Finland, during 1934-44, who as military conscripts underwent a standardised intellectual ability test comprising verbal, visuospatial and arithmetic reasoning subtests. Mortality data came from the Finnish Death Register.

Results: Comparing men in the lowest and highest test score fourths, hazard ratios for all-cause mortality were 1.9 (95% confidence interval 1.4-2.5) for verbal, 2.2 (1.6-3.0) for visuospatial and 1.9 (1.4-2.5) for arithmetic reasoning, corresponding to 2.6, 3.4 and 2.6 excess years of life lost, respectively. Associations were similar for cardiovascular and non-cardiovascular mortality. Intellectual ability scores were stronger predictors in men who grew up in middle class families. Compared with middle class men in the highest fourth of visuospatial reasoning score, middle class men in the lowest fourth lost 6.5 years of life, while men from manual workers- families in the highest fourth lost 2.8 years and men in the lowest fourth lost 5.6 years.

Conclusions: High intellectual ability in men aged 20 protects from mortality in later life. This effect is stronger in men who grew up in middle class as compared with manual workers- families. We suggest that early life conditions that are unfavourable to development of cognitive abilities negate the life expectancy benefits of being born into a more affluent family.

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