Interaction between education and income on the risk of all-cause mortality: prospective results from the MOLI-SANI study

To investigate the separate and inter-related associations of education and household income in relation to all-cause mortality. Prospective study on 16,247 men and women (aeyen35 years), a sub-sample of the MOLI-SANI cohort that had been randomly recruited within an Italian general population. Both education and income were used as categorical variables. Hazard ratios (HR) were calculated by Cox-proportional hazard models. Over a median follow-up of 7.7 years (125,016 person-years), 694 deaths were ascertained. Either education (HR = 0.68; 95 % CI 0.51-0.91) or income (HR = 0.57; 0.42-0.77) was inversely associated with mortality. After simultaneous adjustment, the association of education appeared to be largely explained by income. A significant interaction between both variables was found (p = 0.0078). The inverse association with mortality was stronger when a higher income was combined with a higher educational level (HR = 0.59; 0.38-0.92 for the highest combination of the two indicators). Either education or income was the predictor of mortality in a large sample of the Italian population. The two variables significantly interacted and the inverse association of income with mortality tended to be stronger within higher education groups.