Obesity and COVID-19: are they linked?

02 June 2020
In March this year, the World Health Organisation (WHO) declared COVID-19 (the disease caused by the SARS-COV-2 virus) a pandemic.

In March this year, the World Health Organisation (WHO) declared COVID-19 (the disease caused by the SARS-COV-2 virus) a pandemic.

Early research has highlighted a range of factors associated with the severity of COVID-19. These include whether an individual is older, is male, is of Asian or black ethnicity and whether they have other pre-existing conditions.

Obesity is one of these factors.

NHS Inform in Scotland1, Public Health England2, and the US Centers for Disease Control and Prevention3 (CDC) all state that those with a body mass index (BMI) of 40kg/m2 or above have a higher risk of severe illness in COVID-19. Those with a BMI in this category have been advised to follow strict physical distancing measures. Despite this and the emerging research implicating obesity as a risk factor, obesity has not been formally recognised by the WHO as an independent risk factor for COVID-19.

 

 

What do we know about COVID-19 and obesity so far?

Researchers from countries including China, US, France, Italy and UK have found links between having a higher BMI and an increased risk of hospitalisation, more serious complications and, in some studies, death in COVID-19 patients.

Early research from China found that 42.7% of all COVID-19 patients in a hospital in Shenzhen were either overweight or had obesity17. They found that BMI was also linked to an increased likelihood of developing severe pneumonia, which increased as BMI increased. This was backed up by another study in Zhejiang, which found that of COVID-19 in one hospital, those with more severe illness had significantly higher BMI than those with less severe illness18.

In the US, research from New York City found that obesity was the second most significant risk factor for hospitalisation, following age over 6519. Another report from 12 hospitals in New York City found obesity to be one of the most common pre-existing conditions in patients hospitalised with COVID-19: obesity was recorded in 41.7% of patients20.

A large study by the CDC found that obesity was the most common pre-existing health condition in younger people hospitalised with COVID-19: 59% of these patients had obesity21. This association has also been observed elsewhere in the US22, and in Italy24, where a third of patients who dead with COVID-19 in a study of 3200 people had type 2 diabetes, and just under a third had cardiovascular disease24.

In the UK, a report was published by the Intensive Care National Audit and Research Centre (ICNARC) on 15th May of 8699 patients in critical care units with confirmed COVID-19 in England, Wales and Northern Ireland25. Where BMI was recorded, 73.8% were classed as overweight and 38.6% of these patients had obesity. Patients with overweight or obesity were far more likely to require respiratory or renal support than those without.

Most recently, in the largest COVID-19 study to date, and after taking into account factors such as age, sex, ethnicity and smoking status (to make sure that these factors were not influencing the results), researchers found that increasing BMI was associated with an increased the likelihood of dying in hospital27.

Why might people with obesity be at higher risk of complications?

There are a number of reasons why people with obesity are at increased risk of severe illness from viruses or respiratory illnesses:

  • Obesity causes an underlying state of inflammation in the body, which can affect its ability to fight a virus4,5,6
  • Obesity is a risk factor for other conditions, like type 2 diabetes. It is common for people with obesity to have several conditions at once. Many of the underlying conditions listed by Public Health England within their social distancing guidance are associated with obesity10
  • Lung function is often impaired in those with obesity11as is lung volume and capacity12
  • Standard treatment may be affected, for example, ‘proning’ (turning people on to their front) has become standard treatment in COVID-19 to improve oxygenation to particular areas of the lungs. In patients with obesity, this is much more difficult, and may not be possible in patients with severe obesity4

Conclusion

It is increasingly likely that obesity may be an independent risk factor in COVID-19 severity; however, there is a need for more research and a standardised approach to collecting information on BMI4. There are known links between socio-economic status (SES) and obesity and evidence is emerging for an association between obesity, SES and COVID-19, with poorer outcomes for those from more deprived areas25. By collecting better data on patients with confirmed COVID-19, risk factors can be determined and groups most at risk from the virus can be identified clearly. This information can be used to tailor prevention measures toward groups who require the most protection.

 

Read the full Obesity and COVID-19 briefing, here.

 

References

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