Does Smoking Prevent Covid-19 or is it a myth?

The great enemy of truth is very often not the lie–deliberate, contrived and dishonest–but the myth–persistent, persuasive and unrealistic…… We enjoy the comfort of opinion without the discomfort of thought.

JF Kennedy 1962

There are many myths emerging as we struggle with the SARS-CoV2 virus pandemic. President Trump again covers himself in glory with his latest; suggesting intravenous disinfectant as a treatment option. Vitamin C, Zinc and Vitamin D are all appearing as disease preventors but there is little evidence and politicians generally are getting a bad name when it comes to the advice on, and management of, our current pandemic. Grant Shapps, for example, in an interview last week, declined to call Trump’s disinfectant advise rubbish and where it can be understood he was not wishing to criticise the head of the Free World, there must be a limit. The French Health Minister, Oliver Veran to whom I referred before (ref) because of his claim that taking Ibuprofen could worsen Covid-19 infections, has been at it again. His ibuprofen statement caused Health Services globally to reassess their position on the use of the drug for symptomatic relief of Covid-19 symptoms. Last week the four UK Health departments issued a statement confirming the safety of ibuprofen. They are clear that there is no evidence to support Monsieur Veran’s statement.

Oliver has now decreed that nicotine replacement therapy products (NRT) sales in French pharmacies be restricted to 4 weeks supply per patient. He is doing this he explains to ensure that France does not run out of NRT for those wishing to stop smoking. He is concerned his fellow country men and women will start enmasse applying NRT patches to protect against Covid-19 and in doing so deplete supplies needed for those wishing to stop smoking. He is right to be concerned about the prevalence of smoking in France. Annually 75,000 people die of smoking related disease and about 25% of the population smoke compared to about 18% in the UK. But should he be so dismissive of NRT as a Covid-19 preventor?

His concern has been sparked because France is shortly to begin a study to establish if NRT might protect against Covid-19. A French study published last week identified an interesting relationship between smoking and contracting Covid-19. If you are a smoker you are much less likely to end up in A&E or be admitted to ICU due to Covid-19.

This finding, from this good quality study, is of particular interest since smoking was, from the early stages of the infection, identified as a major risk factor for poorer outcomes in Covid-19.

However, Chinese researches noticed early on that smokers were less likely to end up in A&E or be admitted to ICU and did publish some studies suggesting this counter intuitive fact. Only 12% of Chinese infections in ICU were smokers in a population where 52% of males are smokers. These studies were weak as many of the Covid-19 patients did not have a proper smoking status assigned. An American study confirmed the findings but again there was significant problems with the data. So the French group, working in Paris and studying a cohort of Parisenns, in March and early April trying to ensure robust data on smoking status, covid-19 status and the degree of illness. From nearly 500 Covid-19 patients who went to A&E or were hospitalised and ended up in ICU, they found that only around 5% were daily smokers compared to the French public with a smoking prevalence of some 25%.

Something is going on here but what exactly is unclear. The French team identify a possible or speculative mode of action for nicotine affecting receptors that further impact on ACE2 receptors potentially blocking them or reducing their ability to allow transfer of virus into cells lining the lungs. This ACE2 receptors is the very same one blamed for ibuprofen potentially worsening the prognosis of those suffering from a SARS-cov-2 viral infection. In the French study conclusion the authors offer this comment;

There are however, sufficient scientific data to suggest that smoking protection is likely to be mediated by nicotine. SARS-CoV2 is known to use the angiotensin converting enzyme 2 (ACE2) receptor for cell entry[14-16], and there is evidence that nicotine modulates ACE2 expression[17]which could in turn modulate the nicotinic acetyl choline receptor (manuscript submitted). We hypothesize that SARS-CoV2 might alter the control of the nicotine receptor by acetylcholine. This hypothesis may also explain why previous studies have found an association between smoking and Covid-19 severity[1, 9, 10]. As hospitals generally impose smoking cessation and nicotine withdrawal at the time of hospitalization, tobacco (nicotine) cessation could lead to the release of nicotine receptors, that are increased in smokers, and to a “rebound effect” responsible for the worsening of disease observed in hospitalized smokers.

That is very interesting and suggest that when rushed into ICU due to Covid-19 and denied the nicotine that the smoker has been getting for many years the patient has a much worse prognosis.

As with all studies this one has limitations and most importantly is the speculative link between nicotine and a viral protective mechanism. It is a very good study and it is good science. It is allowing the data to form the conclusions. There is certainly no suggestion that people should start smoking to avoid Covid-19 and in this way Oliver Veran is right but he should wait to see what if any role NRT might have. However, I really fear, if he has shares in big tobacco, Mr Trump might just jump on this bandwagon too before we get the proper answers.

Photo by realworkhard is licensed under CC BY-NC-SA

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