Tracing the association between IQ and mortality risk
posted on: Aug 20, 2009
Previous studies have demonstrated an association between low IQ and elevated mortality risk, but the explanation for this association remains to be identified. In a study published last week in the journal Pediatrics, Markus Jokela at the University of Helsinki, Finland and colleagues, including David Batty at MRC SPHSU, examined potential pathways connecting IQ to mortality risk. The mortality risk associated with low IQ emerges already early in adult life and this is only partly explained by common risk factors of family background, sociodemographic factors or health behaviors, the authors conclude.
In the British birth cohort of 10620 participants, IQ assessed in childhood at age 11 predicted mortality risk from age 11 to age 46, so that the risk of dying by midlife was twice as high in individuals with low IQ compared to those with high IQ (3.4% vs. 1.7%). The IQ-mortality association was largely independent of several measures of childhood developmental characteristics and family background (birth weight, childhood height at 11 years of age, problem behaviors, father's occupational class, parents' interest in child's education, family size, and family difficulties). Adult sociodemographic variables (education, occupational class, marital status) and health behaviors (smoking, BMI, alcohol use, psychosomatic symptoms) also explained relatively little of the IQ-mortality association, none of them accounting for more than 20% of the effect of IQ. The most important explanatory factors were parent's interest in child's education, adult education, and adult psychosomatic symptoms. "We currently have an incomplete understanding of health inequalities originating from individual psychological characteristics, such as IQ," says Jokela. "Identifying these mechanisms could inform us how to plan more effective public health interventions accessible to wider audiences."
Contact: Markus Jokela, Department of Psychology, University of Helsinki, Finland. firstname.lastname@example.org
Reference: Jokela M, Batty GD, Deary IJ, Gale CR, Kivimäki M. Low childhood IQ and early adult mortality: The role of explanatory factors in the 1958 British Birth Cohort. Pediatrics, doi:10.1542/peds.2009-0334