Does smoking protect against coronavirus?

Does smoking protect against coronavirus? The statistics are sometimes disturbing. Without becoming an incentive to smoke - France has been reporting over 200 deaths a day due to tobacco consumption since at least 2013 (and declining since 2000) - the first data on Covid-19 show that the vast majority of severe forms do not involve smokers.

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First spotted on a tweet from Pr. Bertrand Dautzenberg, pulmonologist and tobacco specialist, then on France Inter yesterday morning from Jean-François Delfraissy, Chairman of the Scientific Advisory Board which advises the French government on managing the health situation linked to the coronavirus pandemic, nicotine could thus constitute «a form of protection».

«As if tobacco protects against this virus via nicotine! We could never have imagined this kind of questioning a few weeks ago», explained Jean-François Delfraissy. «Don't give up smoking just yet!», this questioning surrounding nicotine just highlights «some surprising facts at the epidemiological level».

Does smoking make Covid-19 worse?

Several serious studies have been published on the subject, some of them suggesting a down-regulation of ACE2 receptor expression in smokers, which tends to protect them from the coronavirus. Clearly, nicotine closes the doors of entry to the virus in the bronchial tubes and throughout the body.

The first study presents an analysis of the current prevalence of smoking among hospitalized patients with Covid-19 in China, compared with the prevalence of smoking in the Chinese population. This preliminary analysis does not support the argument that smoking is a risk factor for hospitalization with Covid-19. It suggests a protective role linked to the down-regulation of ACE2 receptor expression known to be induced by smoking. The study does not include data on hospitalized patients and e-cigarette use.

The second study entitled «Active smoking is not associated with severity of coronavirus disease 2019 (COVID-19)» concludes that active smoking does not appear to be significantly associated with an increased risk of progression to severe disease in COVID-19. It is based on 44672 cases of coronavirus in China and draws up a meta-analysis of 5 other studies totaling 1399 cases of Covid-19, 288 of them with severe forms.

The latest was published in The New England Journal of Medicine, based on nearly 1,100 Covid-19 patients in China, shows a link between smoking status and the risk of developing a severe form of the coronavirus. Thus, 14% of non-smokers with Covid-19 developed a «severe form» of the disease, compared with 21% of smokers. In the case of very severe forms, which require patients to be admitted to intensive care, only 5% of non-smokers develop this extreme form, compared with 12% of smokers, a difference that can be explained by chronic bronchitis and respiratory diseases caused by smoking.

What about cannabis?

Literature is lacking here. Like the IACM reminded us, Cannabis does not cure coronavirus. However, the University Hospitals of Geneva (HUG) have published a pharmacological evaluation on cannabinoids and Covid-19. During the SARS-CoV-2 epidemic, the HUG recommends avoiding «as a precautionary principle, non-medical consumption of cannabinoid agonists».

The assessment cites several studies on humans and animals and on respiratory viruses other than SARS-CoV-2. Here, stimulation of the CB2 would reduce the signs
infection by modulating the immune system. The administration of a CB1 agonist (such as phytocannabinoids) reduce complications in respiratory syncytial virus (RSV) infection, while administration of a CB1 antagonist leads to an accumulation of immune cells in the peribronchial and perivascular spaces compared with the control group, and exacerbates lung damage.