Background/Purpose: Environmental factors such as smoking, pollutants, diet, and geography as well as sex, race/ethnicity, and genetics have been linked with rheumatoid arthritis (RA) pathogenesis and outcomes. However, most studies assess individual exposures. The U.S. Environmental Protection Agency’s Environmental Quality Index (EQI) provides a multi-domain composite county-level measure of environmental quality by combining 219 variables across five domains: air, water, land, built, and socio-demographic. This offers a unique opportunity to evaluate these cumulative environmental risks on RA mortality. Using this tool, we aimed to investigate the association between EQI domains and the odds of RA-related death versus all-cause mortality, adjusting for urbanization, race/ethnicity, sex, and age. Methods: We analyzed the individual U.S. death certificate data from 2011 to 2015 using the CDC Multiple Cause of Death dataset. RA deaths were identified using ICD-10 codes for seropositive and seronegative RA. EQI scores for 2006-2010 were linked to decedents’ counties using FIPS (Federal Information Processing Standard) codes. Two multivariable logistic regression models were constructed: one assessing total EQI, and another examining individual EQI domains. Both models adjusted for Rural-Urban Continuum Codes (RUCC), race/ethnicity, sex, and age. Interaction terms evaluated effect modification, and stratified analyses were conducted by race/ethnicity and RUCC. Results: Among 12,970,917 total deaths, 43,757 were attributed to RA. Total EQI was not significantly associated with RA mortality. However, individual domains showed significant associations with RA death odds: increased odds: poorer water (OR 1.13; 95% CI, 1.12–1.14), land (1.05; 95% CI, 1.04–1.06), and socio-demographic (1.05; 95% CI, 1.04–1.06) quality; decreased odds: poorer air (0.95; 95% CI, 0.94–0.96) and built environment (0.91; 95% CI, 0.90–0.92) quality (all p < 0.001). Additionally, RA mortality was higher in nonmetro-urbanized areas (OR 1.09; 95% CI, 1.05–1.13) compared to metro areas. Significant interactions were found between the five EQI domains and race/ethnicity and RUCC. Stratified analyses revealed differential associations across racial/ethnic groups and urbanization levels. For example, poor water quality was significantly associated with RA death in Hispanic individuals in metro and less-urbanized areas but not in others. Conclusion: Environmental quality domains independently associate with RA mortality, with variable effects across urbanization and racial/ethnic groups. These findings highlight the importance of addressing environmental and healthcare access disparities to reduce RA-related mortality in vulnerable populations.
