Abstract A071: County-level racial and ethnic diversity index and cancer mortality in the U.S.
Authors: Hirko Kelly A. , Greteman Breanna , Ford Sabrina , Nash Sarah H. 
Published: September 2024

Abstract
Background: The United States is experiencing a demographic trend of increasing racial and ethnic diversity. While persistent racial and ethnic disparities in cancer mortality are well documented, little is known about the impact of racial and ethnic diversity on cancer outcomes in the United States. Purpose: We examined associations between the U.S. county-level racial & ethnic diversity index and age-adjusted cancer mortality rates. We also assessed whether associations differed by geographic region, persistent poverty, and rurality. Methods: We used the U.S. Census Bureau’s 2020 Racial and Ethnic Diversity Index, which estimates the chance that two people chosen at random will be from different racial and ethnic groups. The diversity index was calculated at the county-level and categorized as follows: less than 35% (lowest), 35.0 to 44.9%, 45.0 to 54.9%, 55.0 to 64.9% and 65.0% or more (highest). We described county- level sociodemographic characteristics according to the diversity index categories. We calculated mean and standard errors of the county-level age-adjusted cancer mortality rates per 100,000 from 2016-2020 (overall and by site for the top four sites for cancer mortality) across the diversity index categories. We used multivariable linear regression models to examine associations between racial and ethnic diversity and cancer mortality, overall and by cancer site. We also assessed models stratified by geographic region (U.S. Census regions), persistent poverty and rurality. Results: Counties with more racial and ethnic diversity had a younger median age, a higher proportion of college graduates, and were less likely to be rural. Cancer mortality rates per 100,000 were lower in the most vs. least diverse counties, overall (144.7 vs. 164.6), and for lung (32.5 vs. 44.8), and colorectal cancer (13.0 vs. 15.6). In adjusted models, the highest vs. lowest racial and ethnic diversity was associated with a 7.25 decrease in overall cancer mortality rates (95% CI: -10.5 to -4.0), a 6.55 decrease in lung cancer mortality (95% CI: -8.0 to -5.1) and a 1.49 increase in breast cancer mortality (95% CI: 0.7 to 2.3). The diversity index was not associated with colorectal cancer mortality or pancreatic cancer mortality in adjusted models. Inverse associations of diversity index and overall cancer mortality were strongest in the South Census region (b=-13.0, 95% CI: -17.5 to -8.4), in non-persistent poverty counties (b=-9.0, 95% CI: -12.4 to -5.5), and in rural counties (b=-8.6, 95% CI: -13.2 to -4.1). Conclusions: Greater racial and ethnic diversity was associated with lower overall cancer mortality and lung cancer mortality rates, although it was associated with significantly higher breast cancer mortality rates. Findings help elucidate whether and how social factors may differentially impact subgroups of the population to influence cancer mortality. This study addresses an urgent need to explore contextual factors that may shape racial and ethnic disparities at the population level.
Citation Format: Kelly A. Hirko, Breanna Greteman, Sabrina Ford, Sarah H. Nash. County-level racial and ethnic diversity index and cancer mortality in the U.S. [abstract]. In: Proceedings of the 17th AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2024 Sep 21-24; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2024;33(9 Suppl):Abstract nr A071.