Average county-level IQ predicts county-level disadvantage and several county-level mortality risk rates

Research utilizing individual-level data has reported a link between intelligence (IQ) scores and health problems, including early mortality risk. A growing body of evidence has found similar associations at higher levels of aggregation such as the state- and national-level. At the same time, individual-level research has suggested the IQ–mortality risk association may be mediated by socioeconomic status, but no aggregate research has considered this possibility. This paper extended the current knowledge base in two important ways: 1) by analyzing the association between county-level IQ and county-level mortality risk; and 2) by testing a theoretical model where county IQ influences county disadvantage which, in turn, influences county mortality risk. The findings indicated a consistent relationship between county IQ and several measures of county mortality risk. The IQ–mortality risk association was mediated by county disadvantage for some county mortality risk measures but not others, suggesting the relationship between county IQ and county mortality risk is more nuanced than was hypothesized.