Biological embodiment of educational attainment and future risk of breast cancer: findings from a French prospective cohort.

Abstract

Women with higher educational attainment have a higher risk of developing breast cancer (BC). Despite the acknowledged impact of reproductive and lifestyle factors, some excess risks remain unexplained. Many studies support the hypothesis that education has a distinctive effect on physiological processes associated with health, independently of known risk factors. In this study, we aimed to determine whether the biological embodiment of education could be part of the observed social inequalities in BC risk. We focused on biomarkers from several physiological systems examined individually, and jointly through a biological health score (BHS). Prospective cohort study. This study, based on a subsample of the French E3N cohort, included women with biological data from four nested case-control studies. The study included 3048 postmenopausal women (17% BC). We first evaluated the association between educational attainment and each biomarker, separately (N=11) and by combining them into a BHS, indicative of an augmented biological health hazard when elevated. Finally, we explored the relationships between the socially patterned biomarkers and BHS, and risk of incident BC. Women with higher educational attainment exhibited a lower BHS in comparison to those with lower educational attainment (β_{high education}=-0.21 (95% CI -0.42; 0.01), model 2). Specific biomarkers associated with the cardiovascular (systolic blood pressure (SBP), diastolic blood pressure (DBP), triglycerides (TG), high-density lipoprotein (HDL)), inflammatory (C reactive protein (CRP)) and hormonal systems (sex hormone-binding globulin (SHBG) and oestradiol) were found socially distributed (OR _CRP-high=0.70 (95% CI 0.54; 0.91), OR _TG-high=0.79 (95% CI 0.61; 1.04), OR _DBP-high=0.69 (95% CI 0.53; 0.90), OR _SBP-high=0.57 (95% CI 0.44; 0.74), OR _HDL-high=0.79 (95% CI 0.60; 1.03), (OR _SHBG-high=0.67 (95% CI 0.52; 0.88), OR _{oestradiol-high}=1.34 (95% CI 1.00; 1.79); model 1). Associations persisted after adjustment for cofounders and a large set of potential mediators for two of the investigated cardiovascular markers (OR _DBP-high=0.75 (95% CI 0.57; 1.00), OR _SBP-high=0.61 (95% CI 0.46; 0.81); model 2). No associations were found between the socially stratified biomarkers and BHS with risk of BC. Educational attainment has a direct impact on biological processes suggesting that the biological embodiment of the social environment could be a potential pathway that mediates the association between educational attainment and health. Further studies are needed to specifically investigate the relationships between socially stratified biomarkers and BC risk.