Socioeconomic Status and Inflammation in Women with Early-stage Breast Cancer: Mediation by Body Mass Index

Background: Breast cancer is the most common cancer among women in the US, and women of low socioeconomic status (SES) show markedly poorer outcomes than those of high SES. SES may influence health through inflammation, although links between SES and inflammatory biomarkers have not been investigated in women with breast cancer. This study tested the hypothesis that breast cancer patients of lower SES would show higher levels of inflammation than those of higher SES. BMI was examined as a mediator of this association. Methods: Women recently diagnosed with early-stage breast cancer (N = 194) were recruited before neoadjuvant or adjuvant therapy. Participants completed questionnaires and provided blood samples for immune assessment. SES was indexed by participants' self-reported education and annual household income, BMI was determined by height and weight measurements, and blood was assayed for inflammatory biomarkers linked with cancer outcomes: IL-6, CRP, TNF-alpha, and sTNF-RII. General linear models tested associations between SES and inflammation, and mediation models examined indirect effects through BMI. Results: Consistent with hypotheses, education status was associated with CRP, (F(2,185) = 4.72, p = 0.001), and sTNF-RII, (F(2,185) = 4.19, p = 0.02), such that lower education was associated with higher levels of both biomarkers. Further, BMI mediated the associations between education and CRP, (95% CIs [-0.62, -0.11; -0.76, -0.21]), sTNF-RII, (95% CIs [-0.09, -0.01; -0.10, -0.02]), and IL-6, (95% CIs [-0.32, -0.05; -0.38, -0.09]). Annual household income was not significantly associated with inflammation (ps > 0.25), and indirect effects on inflammation through BMI were not significant. Conclusions: Lower education was associated with higher levels of inflammation in this sample, which may presage poor breast cancer-related and clinical outcomes. SES should inform the development of interventions targeting BMI and inflammation in breast cancer.