To test the hypothesis that an association exists between childhood IQ (at age 11) and mortality up to middle age.
The Newcastle Thousand Families study, a prospectively followed cohort, originally consisted of all 1142 births in the city of Newcastle in May and June 1947. Using data on 717 members of this cohort, we investigated the associations between the results of tests of IQ and English and arithmetic ability at age 11 years and mortality up to the end of 2003 using Cox's proportional hazards models.
Childhood IQ was significantly related to mortality in men (hazard ratio 0.57 for a standard deviation change in IQ at age 11; 95% CI 0.37, 0.86; P=0.007), but not in women (hazard ratio 0.79; 95% CI 0.49, 1.27; P=0.33). Adjustment for social class at birth had little effect on the associations. Similar results were seen when using the English and arithmetic scores.
These results confirm a recently reported association between individual differences in childhood cognition and mortality up to middle age, independent of childhood socio-economic circumstances. It is possible that the link between IQ and mortality is in part mediated through later life choices. Further research is required to identify the mechanisms by which such an association may occur, and to provide input to health promotion and disease management strategies that may improve health throughout life.
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