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Which measure of disparity is correct?

Happy Thanksgiving!  Q&As will resume on Monday, November 30th.

Question: Yesterday you mentioned that Black American COVID patients are 1.24x more likely to die than White American COVID patients.  I thought the rate was much higher than that. This APM Research Lab analysis shows that compared with Whites (and adjusting for age), Blacks have 3x higher mortality.  Which is correct?

Answer: To my knowledge, both numbers–terrible as they are– are correct. The APM number is based on the COVID cumulative mortality rate (deaths/100,000 population) whereas the number I cited is based on the August case fatality rate (deaths/cases).  Racial disparities in mortality rates are primarily driven by: 1) disparities in who is getting infected; and 2) disparities in who succumbs to the disease.  It’s this second piece– disparities in who succumbs to the disease– that the case fatality analysis I described yesterday helps disentangle.    

For example, APM’s analysis shows that Asians have the same overall mortality as Whites. Our case fatality analysis, however, shows that Asians have higher case fatality than Whites (1.19x higher in August*).  This disparity was masked in the overall mortality rate.  Why?  Because Asians have been less likely than other racial/ethnic groups to become infected with COVID, but more likely (particularly in older age bands) to succumb to COVID if they become infected. This is a great example of why it’s important to look at case fatality rates alongside mortality rates.**

Finally, since we’re talking about race and health outcomes, I’ll remind us all that race has no genetic basis and is a social construct (see Q&A of 6/7).  Stark differences in mortality by race are stark markers of inequalities by race.         

*Note: I haven’t re-run the analysis, but to my recollection, the cumulative case fatality rate among Asians is nearly 1.7x higher than the rate among Whites.

**Note: If you ever want to learn more about different mortality frequency measures, CDC’s Principles of Epidemiology in Public Health is a great resource.