An international team of scientists has identified genetic evidence that suggests both smoking and obesity can increase the risk of severe Covid-19.

The researchers also found the same was true for the risk of developing sepsis, a dangerous inflammatory response faced by many patients with other infections.

The findings, published in Circulation, highlight that stopping smoking and losing weight are likely to be effective interventions for reducing the risk of developing severe Covid-19 and sepsis.

The study looked at data from three thousand one hundred and ninety nine patients with severe Covid-19 and ten thousand one hundred and fifty four patients with sepsis and examined genetically predicted exposure to risk factors such as BMI and smoking. The researchers were able to assess whether the presence of these genetic signposts were related to an increased likelihood of severe Covid-19 or sepsis.

Cardiff University reports Dr Mark Ponsford, a clinical clinical academic trainee at the university, and first author on the study, said “Observational studies can be vulnerable to bias – for instance because of confounding factors such as how patients are recruited or data are collected. We used an approach known as ‘Mendelian Randomisation’, a technique that harnesses our knowledge of how our genetic make-up predisposes to a greater BMI or smoking. This approach is generally less affected by these confounding factors.

“Studying large publicly-available genetic datasets from well-characterised UK and Norwegian populations, we found that smoking and obesity increased the risk of developing sepsis. Applying this approach to genetic association studies of severe Covid-19, we found the same outcome. This adds to the growing body of evidence that reducing smoking and obesity are important for public health, and highlights the importance of research exploring the links between the immune response and these traits.”

Dr Dipender Gill, a clinician scientist and senior author on the paper from St George’s, University of London and Imperial College London, said “While it’s already known that smoking and obesity increase the risk of many serious health conditions, including heart disease, stroke and certain types of cancer, our findings highlight that the implications of smoking and obesity are exacerbated in the current Covid-19 pandemic.

“Our work supports that something can be done to reduce risk of severe Covid-19, and in particular that losing excess weight and stopping smoking can make a difference.

“Now, more than ever, it’s essential that campaigns highlighting the benefits of losing excess weight and stopping smoking remain central to public health strategies.”