Contribution of Health Behaviors to the Association between Area-Level Socioeconomic Status and Cancer Mortality

Background: Area-level socioeconomic status (SES) is increasingly recognized as an important predictor of health outcomes; however, its association with cancer mortality is not established. Moreover, mediators of the association between area-level factors and health outcomes are not well understood. The purpose of this study is to quantify the association between area-level SES and cancer mortality and to identify whether and to what extent behaviors mediate the association. Methods: We identified the census block groups of participants in the VITamins And Lifestyle (VITAL) Study cohort and constructed an SES index using data from the 2000 U.S. Census. Participants included 54,736 men and women ages 50–76 years with no history of cancer at baseline (2000–2002). Cancer deaths (n = 1,488) were tracked through the Washington State death file over 7.7 years of follow-up. We tested whether eight modifiable risk factors (e.g. body mass index (BMI), physical activity, diet, alcohol, smoking, screening) mediated the association between area-level SES and cancer mortality. Results: Living in the lowest-SES areas was associated with 77% higher cancer mortality than living in the highest-SES areas (hazard ratio (HR): 1.77, 95% confidence interval (CI): 1.50, 2.11). Adding modifiable risk factors into the models explained 45% (95% CI: −68%, −11%) of the association. In models controlling for individual education and income, area-level SES remained associated with cancer mortality (HR highest- vs. lowest-SES areas: 1.37, 95% CI: 1.14, 1.65) and adding modifiable risk factors reduced the association by 37% (95% CI: −99%, 22%). Smoking, physical activity and screening mediated the largest proportion of the association, while diet, alcohol use and BMI had little explanatory effect for the health disparities. Conclusions: Low area-level SES is associated with increased cancer mortality. This association persists after accounting for individual education and income and is partially mediated by smoking, physical activity, and screening.