Association of educational attainment with cancer mortality in a national cohort study of black and white adults: A mediation analysis

Background: Low educational attainment is associated with excess cancer mortality. However, the mechanisms driving this association remain unknown. Methods: Using data from the REasons for Geographic and Racial Differences in Stroke (REGARDS) study, we evaluated the associations of participant and parental/caregiver education with cancer mortality using Cox proportional hazards models, adjusting for socio-demographic characteristics and health conditions. We used principal components analysis to generate indices of measures representing the social determinants of health (SDOH) and health behaviors. We used structural equation modeling to determine if the association between educational attainment and cancer mortality was mediated by these domains. Results: Among 30,177 REGARDS participants included in this analysis, 3798 (12.6%) had less than a high school degree. In fully adjusted models, those without a high school education experienced about 50% greater risk of death than high school graduates and higher (White participants HR: 1.47; 95% CI: 1.23, 1.76 and Black HR: 1.54; 95% CI: 1.33, 1.79). There was evidence of a modest mediation effect for the association between education and cancer mortality by the SDOH domain score (White total effect HR: 1.25; 95% CI: 1.18, 1.33, indirect effect HR: 1.04; 95% CI: 1.03, 1.05, direct effect HR: 1.21; 95% CI: 1.14, 1.28 and Black total effect HR: 1.24; 95% CI: 1.18, 1.29, indirect effect HR: 1.04; 95% CI: 1.03, 1.05, direct effect HR: 1.19; 95% CI: 1.14, 1.24). There was no evidence of mediation by the health behaviors score. No significant associations were found for female caregiver/ mother's or male caregiver/father's education (N = 13,209). Conclusions: In conclusion, participant education was strongly associated with cancer mortality, and this association was partially mediated by the SDOH domain score.