Associations between intelligence in adolescence and indicators of health and health behaviors in midlife in a cohort of Swedish women Karin Modig a, ⁎, Lars R. Bergman b a Institute of Environmental Medicine, Division of Epidemiology, Karolinska Institute, Box 210, 71 77 Stockholm, Sweden b Stockholm University, Department of Psychology, Sweden article info abstract Article history: Received 22 August 2011 Received in revised form 2 February 2012 Accepted 4 February 2012 Available online 22 February 2012 The objective of this study was to investigate associations between intelligence and indicators of health status and health behaviors at age 43 in a cohort of Swedish women (n = 682). Intel- ligence was measured by standard IQ tests given at ages 10, 13, and 15. At the age of 43, 479 of the women were sampled for a medical examination in which 369 participated (77% participa- tion rate). We performed correlations of IQ and the continuous health variables and we esti- mated logistic regression models with dichotomous health variables as the dependent variables. No significant correlations were found between IQ and any of the continuous health variables. In unadjusted logistic regression models where the cut-off points were set based on standard health risk levels, four out of sixteen indicators of unfavorable health status and health behaviors showed significant negative associations with intelligence, meaning higher risk with decreasing IQ-score. After adjusting for educational level, two remained statistically significant: being obese, OR 1.51 (95% CI 1.08, 2.12) and having a high systolic blood pressure OR 1.45 (95% CI 1.03, 2.03). For all other health variables, this study finds no support for a siz- able association between IQ in adolescence and indicators of health and health behavior in midlife among Swedish women. © 2012 Elsevier Inc. All rights reserved. Keywords: Cognitive epidemiology Health behavior Health Women Intelligence 1. Introduction The inverse association between early intelligence and later morbidity and mortality, sometimes referred to as cog- nitive epidemiology (Deary, 2005; Deary & Batty, 2007), is well established (Batty, Deary, & Gottfredson, 2007; Batty et al., 2009), at least among men. This relationship, together with its potential underlying mechanisms, has also been dis- cussed in several papers (Batty, Deary, & Gottfredson, 2007; Batty, Kivimaki, & Deary, 2010; Deary, 2009; Lager, Bremberg, & Vagero, 2009, 2010). In these studies, intelli- gence was usually measured by global tests of mental ability where the scores on different subtests were added to give a combined score. Of course, such measures cannot automati- cally be assumed to be synonymous with intelligence in a more general sense since there exist different theories of the nature and structure of intelligence (Carrol, 1993; Gardner, 1993; Sternberg, 1985). However, within the dominant g- factor paradigm it is claimed that almost any high-quality test of mental ability that has a reasonably broad set of tasks will load heavily in the g-factor (Gottfredson, 2004; Jensen, 1998). Our definition of intelligence is based on this paradigm and, to avoid confusion with the broader intelli- gence concept, we henceforth mostly use the term “IQ” in- stead of intelligence. Despite the established association between early IQ and later health outcomes the underlying mechanisms linking IQ to them are not clear. IQ may act through other variables, or perhaps not at all, if the associations are due to confound- ing from other factors. Further, as the association between IQ and mortality has been shown in some studies to be present for men only and not for women (Kuh, Richards, Hardy, Butterworth, & Wadsworth, 2004; Lager et al., 2009; Pearce, Deary, Young, & Parker, 2006) it raises questions about Intelligence 40 (2012) 82–90 ⁎ Corresponding author. E-mail address: karin.modig@ki.se (K. Modig). 0160-2896/$ – see front matter © 2012 Elsevier Inc. All rights reserved. doi:10.1016/j.intell.2012.02.002 Contents lists available at SciVerse ScienceDirect Intelligence