Smoking and Covid-19: recent claims, and new findings

On Monday, the World Health Organization (WHO) issued a statement underlining the perils of smoking, and referring to "unproven claims that tobacco or nicotine could reduce the risk of Covid-19". This came days after researchers had published a hypothesis that nicotine may obstruct the novel coronavirus SARS-CoV-2.

Also on Monday, researchers from British and Saudi Arabian institutions published a study associating smoking with Covid-19 deaths.

What has WHO said?

Its statement said it is constantly evaluating new research, including research that examines the link between tobacco use, nicotine use, and Covid-19. "There is currently insufficient information to confirm any link between tobacco or nicotine in the prevention or treatment of COVID-19," it said. It did not specify who had made unproven claims about nicotine reducing Covid-19 risk.

There has been a hypothesis, by researchers from a number of leading French institutions (The Indian Express, May 5). In hospital data, they found that the proportion of smokers among Covid-19 deaths (4.4-5.3%) was much lower than the proportion in the general population (25.4%). They hypothesised that the reason might be in protein structures, called nAChR, that are found in the nervous system, muscle and certain tissues. Nicotine is known to bind with nAChR; the hypothesis is that if nicotine is already present on human cells, it may block SARS-CoV-2. To test the hypothesis, the researchers are conducting human trials.

oes this not go against the conventional view?

The widespread view in the scientific community is that smoking is harmful for Covid-19 patients. A few recent studies have suggested various reasons why. The newest paper, published in PLOS ONE on Monday, reviewed databases to look at the prevalence of smoking — as well as COPD (chronic obstructive pulmonary disease) in Covid-19 patients. It found current smokers were 1.45 times more likely to have severe complications compared to former and never smokers. Also, critically ill Covid-19 patients with COPD had a 63% risk of severe disease and a 60% risk of mortality, while critically ill patients without COPD had only a 33.4% risk of severe disease and 55% risk of mortality.

The researchers added, however, that the study was not able to examine whether there was an association between the frequency of COPD exacerbations, or severity of COPD, with Covid-19 outcomes.

(Inputs and image from theindianexpress.com)