Taking into account the age and sex of the patients, the researchers discovered the number of smokers was much lower than that in the general population estimated by the French health authority Santé Publique
France at about 40% for those aged 44-53 and between 8.8% and 11.3% for those aged 65-75.
The renowned French neurobiologist Jean-Pierre Changeux, who reviewed the study, suggested the nicotine might stop the virus from reaching cells in the body preventing its spread. Nicotine may also lessen the overreaction of the body’s immune system that has been found in the most severe cases of Covid-19 infection.
The findings are to be verified in a clinical study in which frontline health workers, hospital patients with the Covid-19 virus and those in intensive care will be given nicotine patches.
The results confirm a Chinese study published at the end of March in the New England Journal of Medicine that suggested only 12.6% of 1,000 people infected with the virus were smokers while the number of smokers in China is around 28%.
In France, figures from Paris hospitals showed that of 11,000 patients admitted to hospital with Covid-19, 8.5% were smokers. The total number of smokers in France is estimated at around 25.4%.
“Our cross-sectional study strongly suggests that those who smoke every day are much less likely to develop a symptomatic or severe infection with Sars-CoV-2 compared with the general population,” the Pitié-Salpêtrière report authors wrote.
“The effect is significant. It divides the risk by five for ambulatory patients and by four for those admitted to hospital. We rarely see this in medicine,” it added.