UNCORRECTED PROOF 1 The burden of disease and the IQ of nations 2 Vittorio Q1 Daniele ⁎, Nicola Ostuni 3 University “Magna Graecia” of Catanzaro, Department of Legal, Historical, Economic and Social Sciences, Campus S. Venuta, 88100 Catanzaro, Italy 4 5 abstract article info 6 Article history: 7 Received 15 November 2012 8 Received in revised form 23 September 2013 9 Accepted 29 September 2013 10 Available online xxxx 11 12 13 14 Keywords: 15 National intelligence quotient 16 IQ 17 Health 18 Disease 19 Economic development 20 The relationship between the conditions of health of the population and the average intelligence quotients (IQs) 21 was examined in a sample of 138 countries. Health conditions were proxied by DALY rates for infectious and 22 parasitic diseases, perinatal and maternal conditions, and nutritional deficiencies. Results show how the 23 burden of considered diseases – and, particularly, of perinatal and maternal – is strongly and negatively related 24 to national IQs even when income, education, and temperature or latitude are controlled for. The effect of educa- 25 tion on national IQs is significant, but lesser than that of health. The burden of disease is a strong predictor of in- 26 ternational differences in average cognitive abilities. Investment in health in poor countries, and particularly in 27 maternal and neonatal health, would have long-term economic returns by reducing international inequalities. 28 © 2013 Published by Elsevier Inc. 29 30 31 32 33 1. Introduction 34 1.1. Health, education and cognitive abilities: individual levels 35 Epidemiological research shows how health strongly influences the 36 cognitive and non-cognitive skills of individuals. Nutritional deficiencies 37 and infections detrimentally affect cognitive, motor and social–emotional 38 development, especially in early childhood (Freeman, Klein, Townsend, & 39 Lechtig, 1980; Grantham-McGregor et al., 2007). Foetal nutrition and 40 maternal health also have notable consequences on cognitive capabili- 41 ties, school participation and children's attainments, influencing health 42 and well-being into old age (Case & Paxson, 2009; Jukes, Drake, & 43 Bundy, 2008). Intrauterine growth restriction, which in developing 44 countries is mainly due to poor maternal nutrition and infections, tends 45 to be associated with lower cognitive development in childhood and 46 also during adolescence (Walker et al., 2007). Undernutrition and severe 47 stunting at 2–3 years are significantly correlated with later cognitive 48 and educational deficits, school achievement and drop-out (Berkman, 49 Lescano, Gilman, Lopez, & Black, 2002; Mendez & Adair, 1999). 50 The negative association between low-birth weight and cognitive 51 development has been documented for children at age 12 months in 52 Brazil, at age 2 and 3 years in Guatemala, and at 7, 15 and 24 months 53 in Jamaica (Gorman & Pollitt, 1992; Grantham-McGregor, Fernald, & 54 Sethuraman, 1999). In a comprehensive review of the effects of under- 55 nutrition on adult health and human capital in low- and middle-income 56 countries, Victora et al. (2008) found maternal and child undernutrition 57 strongly associated with several adult outcomes, such as shorter adult 58 height, less schooling, lower economic productivity, and that height- 59 for-age at 2 years is a strong predictor of human capital. They concluded 60 that damage suffered in early life leads to permanent impairment, and 61 might affect future generations. Severe deficiencies of some nutrients, 62 such as iodine or iron, negatively influence cognitive abilities. For 63 example, a meta-analysis of 37 studies conducted in China, which 64 included a sample of 12,291 children (b 16 years), indicated that 65 the cognitive damage of children exposed to severe iodine deficiency 66 was profound, estimated at 12.45 IQ points loss with respect to children 67 living in naturally iodine sufficient areas (Qian et al., 2005). 68 Infectious and parasitic diseases are also associated with lower 69 cognitive functions and abilities. Exposure to malaria or infections 70 caused by intestinal worms in early life negatively affects mental 71 performances (Watkins & Pollitt, 1997), such as children's memory 72 (Nokes, Grantham-McGregor, Sawyer, Cooper, & Bundy, 1992), and is re- 73 lated to lower scores on tests on cognitive functions (Sakti et al., 1999; 74 Venkataramani, 2012). In poor countries, infections and parasitic diseases 75 have great, significant, adverse effects on school enrolment, attendance 76 and literacy (Bleakley, 2009; Carr-Hill, Katabaro, Katahoire, & Oulai, 77 2002; Miguel & Kremer, 2004). Malaria, one of the most diffuse parasitic 78 infections – which in 2010 caused an estimated 660,000 deaths, most of 79 which were of children under 5 years age in Africa (WHO, 2012) – has 80 been found to be associated with deficits in language and mathematical 81 scores (Fernando, de Silva, Carter, Mendis, & Wickremasinghe, 2006), 82 together with neurological and cognitive impairments in numerous 83 studies (Walker et al., 2007). 84 All in all, poor health, infections and malnutrition, especially in 85 the early years of life, produce long-lasting effects on the social and 86 economic outcomes of individuals and, consequently, of nations 87 (Cunha & Heckman, 2007; Currie, 2011; WHO, 2001). Learning and Individual Differences xxx (2013) xxx–xxx ⁎ Corresponding author. Tel.: +39 0961 3694942 Q3 . E-mail address: v.daniele@unicz.it (V. Daniele). LEAIND-00839; No of Pages 10 1041-6080/$ – see front matter © 2013 Published by Elsevier Inc. http://dx.doi.org/10.1016/j.lindif.2013.09.015 Contents lists available at ScienceDirect Learning and Individual Differences journal homepage: www.elsevier.com/locate/lindif Please cite this article as: Daniele, V., & Ostuni, N., The burden of disease and the IQ of nations, Learning and Individual Differences (2013), http:// dx.doi.org/10.1016/j.lindif.2013.09.015