Background The association between childhood cognitive ability measured with IQ tests and mortality is well documented. However, studies on the association in women are few and conflicting, and the mechanisms underlying the association are unclear.
Methods Data on IQ were collected at school at age 13 among 19 919 men and women born in 1948 and 1953. Information on childhood socioeconomic position, the participants’ socioeconomic and social circumstances in middle age and mortality up to 2013 was collected through national registers.
Results Lower IQ was associated with an increased risk of all-cause mortality among men (1070 cases, HR 1.31, 95% CI 1.23 to 1.39 for one SD decrease in IQ) and among women (703 cases, HR 1.16, 95% CI 1.08 to 1.25). IQ was associated with mortality from several causes of death in men, and cancer and cardiovascular disorder mortality in women. Adjustment for socioeconomic factors in childhood and, in particular, in adulthood attenuated the associations considerably in men and near completely in women.
Conclusion Lower IQ was associated with an increased risk of mortality in men and women. The explanatory effects of socioeconomic factors in adulthood suggest that they constitute an important pathway in the association between IQ and mortality, especially in women.
- social and life-course epidemiology
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Contributors PA, TH and J-EG conceived the study. J-EG supplied the data. TH wrote the first draft. ASW performed the analyses and wrote subsequent drafts. All authors edited and approved the final version of the manuscript.
Funding This work was supported by the Swedish Council for Health, Working Life and Welfare (Project No. 2011-0255 and).
Competing interests None declared.
Patient consent Not required.
Ethics approval The ethics committee at the Karolinska Institutet, Stockholm, approved the study.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement The data are accessible to postgraduate students and researchers at Swedish and foreign universities and colleges. However, there are some restrictions on deliveries to countries outside the European Union.
Correction notice This article has been corrected since it first published online. The spelling of the second author’s surname has been corrected to Allebeck.