IQ and alcohol-related morbidity and mortality among Swedish men and women: the importance of socioeconomic position

Aims: To investigate the association between intelligence in childhood and later risk of alcohol-related disease and death by examining (1) the mediating effect of social position as an adult and (2) gender as a possible moderator. Design: Cohort study. Setting and participants: 21 809 Swedish men and women, born in 1948 and 1953, from the Swedish "Evaluation Through Follow-up" database were followed until 2006/2007. Measurements: IQ was measured in school at the age of 13 and alcohol-related disease and death (International Classification of Disease codes) were followed from 1971 and onwards. Findings: We found an increased crude HR of 1.23 (95% CI 1.18 to 1.29) for every decrease in group of IQ test results for alcohol-related admissions and 1.14 (95% CI 1.04 to 1.24) for alcohol-related death. Social position as an adult was found to mediate both outcomes. Gender was not found to moderate the association. However, adjusting for socioeconomic position lowered the risk more among men than among women. Conclusions: There was an inverse, graded association between IQ and alcohol-related disease and death, which at least partially was mediated by social position as an adult. For alcohol-related death, complete mediation by socioeconomic position as an adult was found. Gender does not moderate this association. The role of socioeconomic position may differ between the genders.