Childhood socioeconomic status modifies the association between intellectual abilities at age 20 and mortality in later life
OPEN ACCESS- E Kajantie1,2,
- K Räikkönen3,
- M Henriksson4,5,
- T Forsén6,7,
- K Heinonen3,
- A K Pesonen2,3,
- J T Leskinen8,
- I Laaksonen4,
- M Paile-Hyvärinen1,
- C Osmond9,
- D J P Barker9,10,
- J G Eriksson1,6,7,11
- 1National Institute for Health and Welfare, Helsinki, Finland
- 2Hospital for Children and Adolescents, Helsinki University Central Hospital, Helsinki, Finland
- 3Department of Psychology, University of Helsinki, Helsinki, Finland
- 4Centre for Military Medicine, Finnish Defence Forces, Lahti, Finland
- 5National Supervisory Authority for Welfare and Health, Helsinki, Finland
- 6Department of General Practice and Primary Health Care, University of Helsinki, Helsinki, Finland
- 7Vasa Central Hospital, Vasa, Finland
- 8National Defence College, Finnish Defence Forces, Helsinki, Finland
- 9MRC Epidemiology Resource Centre, University of Southampton, General Hospital, Southampton, UK
- 10Heart Research Center Oregon Health and Science University, Portland, Oregon, USA
- 11Helsinki University Central Hospital, Unit of General Practice, Helsinki, Finland
- Correspondence to E Kajantie, National Institute for Health and Welfare, PL 30, Helsinki 00271, Finland; eero.kajantie{at}helsinki.fi
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Contributors EK generated the study questions, analysed the data, wrote the first draft of the manuscript, coordinated other authors' contributions to the redrafts and acts as a guarantor of the paper. KR contributed to the discussion and data analysis with her expertise in intellectual ability testing and to redrafts of the manuscript. MH has previously published a study using data from the same intellectual ability tests as predictors of psychiatric outcomes and contributed with this experience to the data analysis and writing of the Materials and Methods section and discussion. TF was responsible for the collection of data from the archives of Finnish Defence Forces and contributed to redrafts of the manuscript. KH and AKP contributed to the discussion with their expertise on psychological aspects of intellectual ability testing. JTL and IL are responsible for the development of the Finnish Defence Forces intellectual ability test; they oversaw the data collection and contributed to the interpretation of the results and the description of the test in the Materials and Methods section. MP-H took part in cleaning of the intellectual ability test data and contributed to the data analysis, description of the intellectual ability test results and discussion. CO took part in the design and implementation of the Helsinki Birth Cohort Study; as a statistical expert, he oversaw the data analysis and contributed to its description in the Materials and Methods section. DJPB took part in the design and implementation of the Helsinki Birth Cohort Study and contributed to the interpretation of the results, writing the cohort description in the Materials and Methods section and rewriting of the manuscript drafts as a whole. JGE was responsible for the design and implementation of the Helsinki Birth Cohort Study and linked the data with intellectual ability tests scores of the Finnish Defence Forces; he also contributed to data analysis and presentation and rewriting of the manuscript drafts.
- Accepted 24 August 2009
- Published Online First 11 October 2009
Abstract
Background People who score poorly in intellectual ability tests have shorter life expectancy. A study was undertaken to determine whether this association is different in people from different socioeconomic backgrounds.
Methods The mortality of 2786 men born in Helsinki, Finland during 1934–1944 who, as military conscripts, underwent a standardised intellectual ability test comprising verbal, visuospatial and arithmetic reasoning subtests was studied. Mortality data came from the Finnish Death Register.
Results Comparing men in the lowest and highest test score quartiles, HRs for all-cause mortality were 1.9 (95% CI 1.4 to 2.5) for verbal reasoning, 2.2 (95% CI 1.6 to 3.0) for visuospatial reasoning and 1.9 (95% CI 1.4 to 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 quartile of the visuospatial reasoning score, middle-class men in the lowest quartile lost 6.5 years of life while men from families of manual workers in the highest quartile lost 2.8 years and men in the lowest quartile lost 5.6 years.
Conclusions High intellectual ability in men aged 20 protects them from mortality in later life. This effect is stronger in men who grew up in middle-class families than in those who grew up in manual worker families. This finding suggests that early life conditions that are unfavourable to the development of cognitive abilities negate the life expectancy benefits of being born into a more affluent family.
- Intelligence
- cognitive function
- mortality
- death
- socio-economic status
- cognitive problems
- longitudinal studies
- mortality SI
- social inequalities
Footnotes
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Funding This work was supported by the British Heart Foundation; the Academy of Finland; the Päivikki and Sakari Sohlberg Foundation; the Finnish Diabetes Research Foundation; the Finnish Foundation for Cardiovascular Research; the Finnish Foundation for Paediatric Research; the Finnish Medical Society Duodecim; the Jalmari and Rauha Ahokas Foundation; the Novo Nordisk Foundation; the Signe and Ane Gyllenberg Foundation; the Sigrid Jusélius Foundation; the Yrjö Jahnsson Foundation; the Juho Vainio Foundation; and Finska Läkaresällskapet.
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Competing interests None.
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Ethics approval This study was conducted with the approval of the ethics committee of the National Public Health Institute.
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Provenance and peer review Not commissioned; externally peer reviewed.
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