Obesity dramatically increases the risk of death from COVID-19 and this effect is even worse for ethnic minority groups in the UK. However, the extent of this risk across different body weights and ethnic groups was not clear. Researchers using health and Census records have been able to quantify the higher risk of death for people of different ethnic backgrounds based on their BMI.

The challenge

The COVID-19 pandemic highlighted the unequal health impact experienced by different people. Epidemiologists have identified a number of risk factors for severe cases of COVID-19, including ethnicity and obesity. Obesity is well-known to increase the risk of many conditions; from early on in the pandemic, it was apparent that it also increases the risk of hospitalisation and death in people with COVID-19. Other studies found that the chance of COVID-19 death is potentially up to four times greater for people of Black or South Asian ethnicities.

Previous work on type 2 diabetes suggested that the combination of both ethnicity and obesity may increase the risk even further. However, this had not been sufficiently studied in COVID-19 to understand how large this effect is across different values of BMI and ethnicities.

The solution

The researchers who had previously quantified the connection between ethnicity and obesity in diabetes have taken a similar approach for COVID-19. With support from HDR UK, they analysed national Census, electronic health records and mortality data of all adults in England in 2020. Of these, over 12.5 million people had their BMI recorded.

In this group, there were almost 34,000 deaths and 100,000 hospital admissions related to COVID-19. The team analysed how the likelihood of this happening depended on the BMI and ethnicity of the individuals, accounting for differences in age, deprivation, other medical conditions and many other established risk factors.

Impact and outcomes

The results showed that BMI was more strongly associated with COVID-19 deaths for ethnic minority groups than people with a white ethnic background. A BMI of 40 kg/m2 in white ethnicities was equivalent to the risk of BMIs of 30, 27 and 32 in Black, South Asian and other ethnic minority groups, respectively. At low BMI, there was little difference between ethnicities.

These results seemed to be even stronger among people under the age of 70. When broken down into narrower groups, the highest risk populations were those with Bangladeshi and Pakistani ancestry.

Professor Tom Yates, the senior author of the paper, published in the journal Nature Communications, said:

“Previous research had shown that obesity and ethnicity are both independent risk factors for COVID-19 severity and mortality risk, but nobody had adequately studied the interaction between them. In fact, the interaction between these factors and the disproportionate impact of higher BMI in ethnic minority groups was stronger for COVID-19 death than we’d seen for diabetes and other chronic diseases previously.”

Although the biological cause for this link is not clear, it could help identify people at highest risk to prioritise for weight management efforts. In future, this work could be extended to investigate how these risks change following vaccination against COVID-19.

Impact committee

The Impact committee highlighted this paper because of its potential to inform policy to help improve the health of ethnic minorities, an area that has been neglected. The scale of the data will also allow the medical community to better understand the impact on a range of subgroups in great detail.