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Racial disparities in COVID-19 mortality are driven by unequal infection risks

Our take —

This is a prospective study, available as a preprint and thus not yet peer reviewed, using case level data on 49,701 confirmed and probable cases of SARS-CoV-2 from Michigan, United States. Investigators found that racial minorities (except for Native Americans) had higher incidence and mortality rates compared to whites. The similarity in case fatality rates among racial groups suggests that greater exposure to the virus may be driving excess deaths in racial minority groups compared to whites. This could be indicative of various factors such as higher population density or a lack of ability to socially distance due to a higher number of essential workers in these communities. A major limitation is that the study does not include other variables (e.g. markers of socioeconomic status (SES) or neighborhood level SES) that may help explain underlying contributors to the disparities. However, this provides a basis for future studies to identify the mechanisms driving racial disparities in infection and mortality rates.

Study design

Prospective Cohort

Study population and setting

Data were used from 49,701 individuals with confirmed or probable SARS-CoV-2 infection from the Michigan Disease Surveillance System (MDSS) from March 8 to May 20, 2020. The data included information regarding sex, age, race, date of death (if applicable), and date the case was referred to the Michigan Department of Health and Human Services (MDHHS). Investigators excluded individuals who did not reside in Michigan, had missing data on race/ethnicity, age, or sex at birth, or any duplicates in the data. Investigators reported comparisons of infection and mortality rates by race, age, and sex by using 2010 US Census data to represent Michigan’s population.

Summary of Main Findings

After standardizing by age and sex, Black [IRR: 5.6 (95% CI: 5.5, 5.7)], Latinx [IRR: 3.8 (95% CI: 3.7, 3.9)], Asian/Pacific Islander [IRR: 2.4 (95% CI: 2.2,2.5)], and other [IRR: 5.2 (95% CI: 4.9, 5.5)], race was associated with a higher SARS-CoV-2 incidence rate compared to white race. Overall within the population, Black, Latinx, Asian/Pacific Islander, and other race was also associated with higher mortality rates compared to whites. There were no statistically significant differences in the case fatality rate (I.e. the mortality rate only among cases) between racial groups, thus this suggests that higher overall mortality rates among racial minorities is due to increased risk of infection.

Study Strengths

This study had a large sample size as it included all confirmed and probable cases that were reported to MDHHS. Reconciling these data with the 2010 US Census allowed for investigators to calculate incidence and mortality rates that could be representative of the Michigan population.

Limitations

The investigators did not include other variables (e.g. indicators of socioeconomic status) that may further help explain racial disparities in infection and mortality rates. Also, due to the fact that investigators used the 2010 US Census, the base population of Michigan in 2020 may be different from that of the 2010 U.S. Census, thus these figures may not be accurate if there were significant demographic changes over this 10-year period.

Value added

This study highlights the stark racial disparities in infection and mortality rates in Michigan, and suggests that excessive deaths among racial minorities is due to greater exposure to the virus rather than being more likely to die once one has the virus.

This review was posted on: 2 October 2020