Ethnic disparities in COVID-19 mortality: are comorbidities to blame?

On June 2, 2020, Public Health England (PHE) reported on the disparities in the risk and outcomes of COVID-19. After adjusting for sex, age, deprivation, and region, people from a Black, Asian, and Minority Ethnic (BAME) background had a higher risk of death from COVID-19 than White British people. This analysis did not adjust for comorbidities, and the PHE report highlighted this to be an important limitation as comorbidities were postulated to be “more commonly seen in some BAME groups”.

PHE refers to a study from the COVID-19 Clinical Information Network (CO-CIN), led by Harrison and colleagues, of the difference in survival from COVID-19 associated with membership of an ethnic group. In this study, once comorbidities were accounted for, there was no difference in COVID-19 mortality between ethnic groups. This initially appears to support PHE's conclusion that differences in the distribution of comorbidities may account for the increased COVID-19 mortality of BAME patients.

However, in CO-CIN's analysis of more than 14 000 patients with COVID-19 admitted to UK hospitals, BAME patients were more likely to have diabetes, but less likely to have other comorbidities such as chronic cardiac, pulmonary, kidney, and neurological disease, malignancy, and dementia. In the multivariate analysis of risk factors for COVID-19 mortality, the adjusted hazard ratio for diabetes (1·11) was less than that for chronic cardiac (1·20), pulmonary (1·24), and kidney disease (1·28), and dementia (1·40), and equal to the adjusted hazard ratio for malignancy (1·11).

Furthermore, age was by far the largest contributor to risk of death, with an adjusted hazard ratio of 9·09 for patients aged 70–79 years and 11·72 for those aged 80 years and older, compared with people younger than 50 years. 60·7% of White patients admitted to hospital with COVID-19 were aged 70 years and older, compared with 30·7% of Black, 29·2% of Asian, and 35·2% of Minority Ethnic patients.

As patients from a White ethnic background were more likely to be older and have comorbidities associated with a higher risk of dying from COVID-19, it is very concerning that the case fatality at 30 days after hospital admission for COVID-19 appears to be the same in Black and White patients. The lack of association between ethnicity and COVID-19 mortality after adjustment for comorbidities is not reassuring. This suggests that research into ethnic disparities in COVID-19 mortality must consider social as well as biological factors.