Neighborhood-level income inequality and breast cancer stage at diagnosis

Purpose Area-level socioeconomic differences may affect health outcomes due to, among other factors, differences in health care access. These differences may exist even among individuals with equivalent health insurance coverage. The purpose of this study was to examine the effect of neighborhood-level differences in per capita income on breast cancer stage at diagnosis. Methods Using SEER–Medicare linked data, the authors examined stage at diagnosis for 76,448 women diagnosed with breast cancer between 1992 and 1998. Subjects were older than 65 and enrolled in Medicare. Stage and neighborhood-level variables were reported by the SEER (Surveillance, Epidemiology and End Results) program. Income inequality was measured as census tract mean per capita income. Confounders included both individual-level and area-level factors. Polytomous logistic regression was used to calculate odds ratios. Results Living in an area with per capita income less than $15,000 was associated with a 19% increase (95% CI = 1.08–1.31) of each stage of breast cancer, compared with those in the highest income areas. Covariates included individual age, race, marital status, presence of comorbidities, and area-level percent black, percent Hispanic, percent English-speaking, and urban versus rural residence. Conclusion Even among those with similar health insurance coverage, living in an area with lower per capita income contributed to later stage at diagnosis.