Contribution of health behaviors to the association between area-level socioeconomic status and cancer mortality

Cancer mortality is higher among residents of low-socioeconomic status (SES) areas than those of high-SES areas; however, the contribution of modifiable risk factors to this disparity is not known. We used data from 54,737 participants in the VITamins And Lifestyle (VITAL) Study, aged 50-76 with no history of cancer at baseline (2000-2002). Of these, 1488 died of cancer over an average of 7.7 years of follow-up. Data on modifiable risk factors including body mass index (BMI), physical activity, diet, alcohol, smoking and screening were taken from baseline questionnaires. We constructed a block group-level SES index using data from the 2000 United States Census and fit Cox proportional hazards models estimating the association between area-level SES and total cancer mortality with and without control for modifiable risk factors. All statistical tests are 2-sided. Cancer mortality was 77% (95% CI: 50%, 111%) higher in the lowest-SES areas compared with the highest. Modifiable risk factors accounted for 45% (95% CI: 34%, 62%) of this association. Smoking explained the greatest proportion (29%; 95% CI: 22%, 40%) of the observed association, followed by diet (11%; 95% CI: 7%, 17%), physical activity (10%; 95% CI: 7%, 16%), screening (9%; 6%, 13%), and BMI (5%; 95% CI: 1%, 10%). Results were similar in models controlling for individual education and income. The association between area-level SES and cancer mortality is partially explained by modifiable risk factors, which could suggest the appropriate targets to reduce socioeconomic disparities.