Multilevel sociodemographic and socioeconomic disparities in COVID-19 outcomes in the Central Puget Sound region, 2020-2021

Presence of at least one underlying health condition (UHC) is positively associated with severe COVID-19. Although disparities in severe COVID-19 outcomes by race, ethnicity, and socioeconomic position (SEP) are extensively documented, there is little research examining these associations beyond the effect of UHCs. Studies also show regions of lower SEP and higher racial residential segregation (RRS) have greater adverse COVID-19 outcomes, but are limited by their geographic coarseness and ecological nature. Furthermore, relatively few age-stratified studies have been conducted, especially studies focused on young adults, who have had the highest incidence of COVID-19 during much of the pandemic. METHODS: We leveraged 2017-2021 electronic health record data from the University of Washington Medicine (UWM) healthcare system and publicly-available neighborhood-level data to conduct three retrospective cohort studies of UWM patients. First, we used regression modeling to estimate age-stratified (18-39, 40-64, and 65+ years) adjusted risk ratios (aRRs) and risk differences (aRDs) of COVID-19-associated hospitalization by any UHC, among SARS-CoV-2-positive patients. Next, among SARS-CoV-2-positive patients aged 18-39, we used regression modeling to estimate aRRs and aRDs of COVID-19-associated hospitalization by SEP (measured by health insurance status) and race and ethnicity, adjusted for any UHC to examine these associations beyond the effect of UHCs. Finally, in a multilevel analysis, we used generalized estimating equations to estimate aRRs and aRDs of (1) receiving SARS-CoV-2 testing and (2) testing positive by block group-level SEP and RRS (high vs. low disadvantage/segregation), accounting for clustering by residential census block group and adjusted for individual-level SEP (health insurance status) and race and ethnicity. We measured RRS using the divergence index, and group-level SEP using a previously-developed area deprivation index. RESULTS: First, we found that patients with any UHC in all age groups were at significantly increased risk of COVID-19-associated hospitalization, and that the aRR comparing patients with vs. those without UHCs was notably higher for patients aged 40-64 (aRR [95% CI] for 18-39: 4.3 [1.8, 10.0]; 40-64: 12.9 [3.2, 52.5]; 65+: 3.1 [1.2, 8.2]; overall: 5.3 [3.0, 9.6]). Our estimated aRDs increased across age groups (aRD [95% CI] per 1,000 SARS-CoV-2-positive persons for 18-39: 10 [2, 18]; 40-64: 43 [33, 54]; 65+: 84 [51, 116]; overall: 28 [21, 35]). Next, we found that uninsured/publicly insured young adults had a 1.9-fold higher risk of hospitalization (aRR [95% CI]=1.9 [1.0, 3.6]) and 9 additional hospitalizations per 1,000 SARS-CoV-2 positive persons (aRD [95% CI]=9 [-1, 20]) compared to the privately insured. Hispanic or Latine, non-Hispanic (NH) Asian, NH Black, and NH Native Hawaiian or Pacific Islander patients had a 1.5-, 2.7 , 1.4-, and 2.1-fold-higher risk of hospitalization (aRR [95% CI]=1.5 [0.7, 3.1]; 2.7 [1.1, 6.5]; 1.4 [0.6, 3.3]; 2.1 [0.5, 9.1]), respectively, compared to NH White patients. Finally, we found that patients living in highly disadvantaged neighborhoods were less likely to receive testing (aRR [95% CI] = 0.84 [0.81, 0.87]; aRD [95% CI] = -329 [-404, -254]) and, among those tested, more likely to test positive (aRR [95% CI] = 1.26 [1.16, 1.36]; aRD [95% CI] = 149 [95, 203]) compared to patients in low disadvantage neighborhoods. Patients in highly segregated neighborhoods also were less likely to receive testing (aRR [95% CI] = 0.95 [0.93, 0.98]; aRD [95% CI] = -120 [-184, -55]) and, among those tested, more likely to test positive (aRR [95% CI] = 1.06 [0.99, 1.13]; aRD [95% CI] = 30 [-1, 61]) compared to patients in low segregation neighborhoods, although the latter associations were not statistically significant. CONCLUSIONS: We found that individuals with UHCs were at significantly increased risk of COVID-19-associated hospitalization, regardless of age. Furthermore, though they should be interpreted with caution given low precision, our findings suggest the increased risk of COVID-19-associated hospitalization among young adults of color and young adults of lower SEP may be driven by forces other than UHCs, including social determinants of health. These results support the prevention of severe COVID-19 in adults with UHCs in all age groups as an ongoing local public health priority, and underscore the importance of equitable access to vaccines and anti-SARS-CoV-2 therapy for young adults of color and young adults of lower SEP in general, not only for those with UHCs. Finally, our findings support targeted local morbidity and mortality prevention initiatives, including age-group-specific risk communication, and the use of neighborhood measures to inform COVID-19 resource allocation to mitigate disparities.