Neighborhood racial and ethnic composition typology and breast cancer risk: the Multiethnic Cohort Study

Living in racially and ethnically segregated neighborhoods may increase the risk of breast cancer. We examined associations between neighborhood racial and ethnic composition typology and risk of primary invasive breast cancer in a population-based sample of 102 615 African American/Black, Japanese American, Native Hawaiian, Latino, and White females residing in California and Hawaii from the Multiethnic Cohort (MEC) Study from 1993 through 2019. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated using multivariable Cox proportional hazards regression. In California, African American/Black females residing in predominantly White neighborhoods had decreased breast cancer risk compared to African American/Black females residing in predominantly Black neighborhoods (HR, 0.71; 95% CI, 0.50-0.99). Latino females residing in mixed White and Asian American/Pacific Islander neighborhoods had increased breast cancer risk (HR, 1.59; 95% CI, 1.20-2.11) in comparison to Latino females residing in predominantly Hispanic neighborhoods. In Hawaii, Japanese American females residing in multiethnic neighborhoods had increased breast cancer risk (HR, 1.49; 95% CI, 1.24-1.78) compared to Japanese American females residing in predominantly Asian American neighborhoods. Native Hawaiian patients residing in predominantly Asian American neighborhoods had increased breast cancer risk (HR, 1.23; 95% CI, 1.04-1.45) compared to Native Hawaiian patients residing in mixed Native Hawaiian neighborhoods. Our findings can inform future studies to identify specific pathways through which segregation influences cancer risk in multiethnic populations.