Educational level, mediators, and risk of atrial fibrillation by sex in The Tromsø Study 1994–2016

Abstract Aims To study the association between socioeconomic position (SEP), indicated by educational level, and incident atrial fibrillation (AF), and the role of lifestyle and cardiovascular risk factors as potential mediators in the causal pathway. Methods and results Using education as indicator for SEP, we examined the association with AF and the mediation by body mass index, hypertension, smoking, alcohol, and physical activity. Our sample included 25 796 adult women and men from a population-based cohort study with median follow-up of 22 years (1994–2016). Total effect, natural direct effect (not through mediators), and natural indirect effect (through mediators) hazard ratios (HRs) were estimated using a counterfactual-based natural-effects model. Total effect of education on AF was small, and only significant for women with upper secondary as compared with primary education (19% lower hazard, 95% confidence interval 4%, 32%). All natural direct effect HRs were non-significant but suggesting increased risk by higher educational level. Compared with women with primary education, natural indirect effect hazard was 11% (4%, 17%) lower in women with upper secondary education, 18% (7%, 28%) lower in women with university/college education <4 years and 25% (12%, 34%) lower in women with university/college ≥4 years. In men, however, natural indirect effect did not differ between the levels of education. Conclusion We found protective indirect effect of education on AF through lifestyle and cardiovascular risk factors in women, but not in men. The direct effect in both women and men indicated increased risk by higher education, although non-significant.