Obese people were more at risk of severe Covid for the opposite reason to what doctors originally thought, a new study suggests.
Experts initially believed that severely overweight people were becoming more ill when they caught coronavirus because their bodies were already highly inflamed, triggering a dangerous immune overload.
But now Cambridge University has found that obese people actually mount a poorer inflammatory response than healthy weight individuals, meaning they struggle to fight off the virus.
Patients suffering from severe Covid are often given anti-inflammatory drugs to help dial down the immune system, but the new study suggests the opposite might be needed for obese people.
Professor Menna Clatworthy, a clinician scientist at the University of Cambridge, said: “During the pandemic, the majority of younger patients I saw on the Covid wards were obese.
“Given what we know about obesity, if you’d asked me why this was the case, I would have said that it was most likely due to excessive inflammation. What we found was the absolute opposite.”
For the new research, scientists analysed blood and lung samples taken from 13 obese patients with severe Covid-19 requiring mechanical ventilation and intensive care treatment at Addenbrooke’s Hospital.
The samples were then compared to those non-obese Covid-19 patients and people on ventilators for other conditions.
They found that cells in the lining of the lungs, nasal cells, and immune cells in the blood show a blunted inflammatory response in obese patients, producing low levels of molecules needed to fight the infection.
“This was really surprising and unexpected,” added Professor Clatworthy added: “Across every cell type we looked at, we found that the genes responsible for the classical antiviral response were less active. They were completely muted.”
The researchers say the findings could have important implications both for the treatment of Covid and in the design of clinical trials to test new treatments.
Doctors have frequently turned to anti-inflammatory drugs to fight Covid, but the team said that the medication may not be appropriate for obese patients.
Co-author Dr Andrew Conway Morris from the Department of Medicine at the University of Cambridge and Honorary Consultant on the intensive care unit at Addenbrooke’s Hospital said: “What we’ve shown is that not all patients are the same, so we might need to tailor treatments.
“Obese subjects might need less anti-inflammatory treatments and potentially more help for their immune system.”
Their results were published in the American Journal of Respiratory and Critical Care Medicine.
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