Objective: To compare the strength of the relation of two measurements of IQ and eleven established risk factors with total and cardiovascular disease (CVD) mortality.
Methods: Cohort study of 4166 US male former army personnel with data on IQ test scores (in early adulthood and middle-age), a range of established risk factors, and 15 year mortality surveillance.
Results: When CVD mortality (N=61) was the outcome of interest, the relative index of inequality (hazard ratio; 95% CI) for the most disadvantaged relative to the advantaged (in descending order of magnitude of the first six based on age-adjusted analyses) was: 6.58 (2.54, 17.1) for family income; 5.55 (2.16, 14.2) for total cholesterol; 5.12 (2.01, 13.0) for body mass index; 4.70 (1.89, 11.7) for IQ in middle-age; 4.29 (1.70, 10.8) for blood glucose; and 4.08 (1.63, 10.2) for HDL cholesterol (the RII for IQ in early adulthood was ranked tenth: 2.88; 1.19, 6.97). In analyses featuring all deaths (N=233), the RII for risk factors most strongly related to this outcome was: 7.46 (4.54, 12.3) for family income; 4.41 (2.77, 7.03) for IQ in middle-age; 4.02 (2.37, 6.83) for smoking; 3.81 (2.35, 6.17) for educational attainment; 3.40 (2.14, 5.41) for pulse rate; and 3.26 (2.06, 5.15) for IQ in early adulthood. Multivariable adjustment, which may serve to identify pathways by which IQ is related to mortality risk, led to marked attenuation of these relations, particularly those for IQ.
Conclusions: Lower scores on measures of IQ at two points in time were associated with CVD and, particularly, total mortality at a level of magnitude greater than several other established risk factors.
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