Association between intelligence and coronary heart disease mortality: a population-based cohort study of 682 361 Swedish men

BACKGROUND: Socio-economic position and intelligence predict coronary heart disease but their mutual associations are not yet well understood. We investigated associations between intelligence and coronary heart disease mortality and explored if they are confounded or modified by socio-economic position. DESIGN: This was a cohort-based follow-up study. METHODS: Data on intelligence, systolic and diastolic blood pressures and body mass index were measured at conscription examination at age 18 years in 682 361 Swedish men born 1951-1965. Data on parental and own education and social position were derived from censuses in 1960, 1970, 1980 and 1990. Follow-up data up to end of 2001 were derived from the Swedish Cause of Death Register and 737 coronary heart disease deaths were observed. Data were analyzed by Cox regression and conditional logistic regression models. RESULTS: An inverse association was found between intelligence and coronary heart disease mortality after adjustment for parental and own education and social position, body mass index and blood pressure (hazard ratio 0.92; 95% confidence interval 0.88-0.96). These associations were of similar strengths within all socio-economic categories and also found within 215 brother pairs discordant for coronary heart disease mortality and intelligence (odds ratio 0.76; 95% confidence interval 0.58-1.00). CONCLUSIONS: Intelligence is associated with coronary heart disease mortality independently of socio-economic position. Health education messages should be tailored according to intellectual performance of the recipients, but also other factors are important for socio-economic coronary heart disease inequalities.