Our ecological study used US county-level data to investigate US health disparities by studying the joint effects of demographic, socioeconomic, and health variables on COVID-19 cumulative case and death rates as of 11/8/20 using representative national data. We found racial and ethnic health disparities among Black/African American, Hispanic/Latino, American Indian/Native Alaskan, and Native Hawaiian/Pacific Islander communities persisted after adjusting for county-level socioeconomic and prevalence of comorbid conditions. We also observed that increased racial residential segregation increased COVID-19 case and death rates, with different impacts across racial and ethnic communities. Lastly, our estimated COVID-19 case and death rates account for potential instability in observed rates from counties with small populations or few confirmed cases/deaths and can assist in identifying counties with the greatest total COVID-19 burden.
Univariate associations between race/ethnic composition and COVID-19 outcomes were considerably stronger prior to adjustment for socioeconomic factors and comorbidities, indicating socioeconomic factors and comorbidities may partially explain observed racial and ethnic disparities. Several unstudied factors may additionally contribute residual racial and ethnic disparities, including differences in neighborhood testing rates, percentage of healthcare workers, percentage of essential workers, exposure to infected individuals within households and in communities, Personal Protection Equipment (PPE) access, use of public transportation, access, quality, and utilization rates of available healthcare facilities/resources, access to living resources (such as a lack of access to clean water in many households of American Indian/Alaskan Native communities), and health literacy. Since many of these measures were either not available or quantifiable at the county-level, we were unable to control for them in analyses.
Counties with increased racial residential segregation experienced increased COVID-19 case and death rates. While Black and American Indian communities have historically been segregated into counties, Hispanics communities are more prone to micro-segregation within counties25–27. Counties and states may appear to be less segregated on a larger level, but Hispanic/non-Hispanic communities may still remain racially segregated at the neighborhood level28,29. In addition, after adjusting for socioeconomic variables and comorbidities, counties with more racial segregation had stronger associations between Native American percentage and COVID-19 case and death rates. This suggests stronger COVID-19 disparities were experienced on Native American territories and reservations, which have more racial segregation, compared to Native American living in other communities.
Our county-level results on racial and ethnic disparities also reinforce and expand findings reported from existing individual-level studies. Single institution studies in the US have also found that Black COVID-19 patients were more likely to be hospitalized, enter the intensive care unit, and die9,30. United Kingdom Biobank and electronic health record studies looking at individual-level data have also found that Black and Asian individuals have an increased risk of COVID-19 hospitalization and deaths after adjusting for covariates31–33.
Our county-level results in the other domains are consistent with those from several smaller scale individual-level studies. We found counties with a greater proportion of individuals with ages 60+ years tended to have increased death rates. Individual-level studies also reported that older patients were more likely to develop severe COVID-19 symptoms and have greater mortality rates34. We found county average household size was associated with increased case and death rates. Household size is known to affect COVID-19 contact and transmission rates35. We found county level rates of heart failure, hypertension, and stroke were associated with case and/or death rates. These pre-existing health conditions are important biological and clinical risk factors for COVID-19 disease severity and mortality34,36. We found county COPD percentage was negatively associated with COVID-19 case and death rates. Some studies have observed a lower than expected prevalence of COPD in COVID-19 patients, but this association is still being investigated as other studies have reported COPD is a significant risk factor for COVID-19 infection at the individual level37–39. Lastly, we found counties with more individuals ages 20-29 tended to have residents spend less time at home. As early as early February 2020, there have been discussions about young adults being more likely to go out and socialize despite social distancing guidelines40; this issue received more media attention in June and July.
Our SafeGraph mobility metric analyses suggested residents of counties with a higher percentage of people with no high school diplomas or health insurance tended to spend less time at home. These communities may have a higher percentage of essential workers who are unable to work from home, may be more likely to take public transportation, and may be more susceptible to contracting COVID-1941. Such areas may require additional attention and interventions.
We observed different county-level socioeconomic associations across various races/ethnicities. This emphasizes that demographic, socioeconomic and immigration complexities faced by various populations are likely to differ substantially between vulnerable communities, especially those with high proportions of under-represented minorities42. To address this challenge, public health interventions, medical care services, and outreach efforts need to be tailored to the unique challenges and needs of each community.
Because we control for fixed state effects, adjusted race/ethnicity composition associations adjust for unmeasured state-specific factors (e.g. differences in testing capacity or response procedures). Within states, counties with larger non-white populations may tend to be more socioeconomically underserved, and the numbers of reported cases are likely to underestimate the total number of infected cases23,24. If under-reporting is driven by race/ethnicity, our reported adjusted associations likely understate the true extent of racial/ethnic disparities. To address racial health disparity on COVID-19 in US, county-level race/ethnicity specific case and death count data are needed for research purposes.
Our findings are based on ecological associations at the county level, and analysis at this level is subject to several limitations (Methods). Associations observed at an aggregated level may be in the same direction, different direction, or not exist at the individual level43. As with all observational studies, associational findings do not imply causality. It is of interest to in the future conduct studies on COVID-19 disparities using individual-level data with additional information on household and community exposures to COVID-19 cases, occupation and work conditions, housing conditions, public transportation usage, basic living resources, and COVID-19 treatments. Despite these limitations, our US county-level ecological study identified elevated risks of COVID-19 cases and deaths in areas with substantial non-White populations after adjusting for socioeconomic and disease prevalences.
Multi-faceted efforts are needed to combat the pandemic by addressing these COVID-19 health disparity issues. Increased resources, such as testing priority and accessible points of care, should be allocated to counties with more racial/ethnic minority populations or residential racial segregation, as well as those counties with more crowded housing, more elderly residents, less education infrastructure, greater prevalences of hypertension, and less living resources, such as a lack of clean water. Intervention measures can include policies requiring face coverings, guaranteeing workers can take paid sick leave, providing personal protective equipment to essential workers, and ensuring prioritized and robust testing, tracing, and isolation infrastructure. Outreach efforts can include transportation assistance, social and community support, and increased accessibility and affordability of health care.