Relationship of neighborhood social determinants of health on racial/ethnic mortality disparities in US veterans—Mediation and moderating effects

Abstract

Objective: To examine mediation and moderation of racial/ethnic all-cause mortality disparities among Veteran Health Administration (VHA)-users by neighborhood deprivation and residential segregation. Data sources: Electronic medical records for 10/2008-9/2009 VHA-users linked to National Death Index, 2000 Area Deprivation Index, and 2006-2009 US Census. Study design: Racial/ethnic groups included American Indian/Alaskan Native (AI/AN), Asian, non-Hispanic black, Hispanic, Native Hawaiian/Other Pacific Islander, and non-Hispanic white (reference). We measured neighborhood deprivation by Area Deprivation Index, calculated segregation for non-Hispanic black, Hispanic, and AI/AN using the Isolation Index, evaluated mediation using inverse odds-weighted Cox regression models and moderation using Cox regression models testing for neighborhood*race/ethnicity interactions. Principal findings: Mortality disparities existed for AI/ANs (HR = 1.07, 95%CI:1.01-1.10) but no other groups after covariate adjustment. Neighborhood deprivation and Hispanic segregation neither mediated nor moderated AI/AN disparities. Non-Hispanic black segregation both mediated and moderated AI/AN disparities. The AI/AN vs. non-Hispanic white disparity was attenuated for AI/ANs living in neighborhoods with greater non-Hispanic black segregation (P =.047). Black segregation's mediating effect was limited to VHA-users living in counties with low black segregation. AI/AN segregation also mediated AI/AN mortality disparities in counties that included or were near AI/AN reservations. Conclusions: Neighborhood characteristics, particularly black and AI/AN residential segregation, may contribute to AI/AN mortality disparities among VHA-users, particularly in communities that were rural, had greater black segregation, or were located on or near AI/AN reservations. This suggests the importance of neighborhood social determinants of health on racial/ethnic mortality disparities. Living near reservations may allow AI/AN VHA-users to maintain cultural and tribal ties, while also providing them with access to economic and other resources. Future research should explore the experiences of AI/ANs living in black communities and underlying mechanisms to identify targets for intervention.