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Letter to the Editor
DOI: 10.1016/j.pulmoe.2020.12.013
Open Access
Available online 23 January 2021
Cigarette smoking and COVID-19
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Marco Rossato
Corresponding author
marco.rossato@unipd.it

Corresponding author at: Clinica Medica 3, Department of Medicine – DIMED, University Hospital of Padova, 35128 Padova, Italy.
, Angelo Di Vincenzo
Clinica Medica 3, Department of Medicine – DIMED, University - Hospital of Padova, Italy
Received 20 December 2020
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In a recent editorial published on tobacco and COVID-19, the Sociedade Portuguesa de Pneumologia raises doubts and caution about the data coming from the medical and scientific community regarding the hypothesis that cigarette smoking or nicotine could be “protective” against COVID-19, recommending that this information should not be taken as an invitation to start smoking or to delay giving it up to avoid SARS-CoV-2 infection or its complications.1

The role of cigarette smoking/nicotine (or whatever else is contained within cigarette smoke) in the scientific discussion on COVID-19 ignores the fact that smoke cessation has to be discouraged to avoid COVID-19 pulmonary complications (this seems obvious for scientists and physicians) but references the scientific importance of the strong epidemiological data coming from all the countries that hospitalized patients with SARS-CoV-2 related pneumonia show quite low percentages of active smokers.2,3

Based on this we have to strongly support the importance of understanding of the possible mechanisms characterizing these aspects, i.e. how cigarette smoking dampens the inflammatory response during infection by SARS-CoV-2 strongly reducing the severe complications of SARS-CoV-2 infection, mainly nterstitial pneumonia and ARDS. The reported evidence that among COVID-19 patients, those who are (and/or were) smokers show worse clinical progression with respect to never smokers is not in contradiction with the huge number of studies showing that there are few active smokers among hospitalized patients with SARS-CoV-2 related pneumonia.4–6 However it is quite strange that a scientific society does not seem to understand the important scientific implications of such observations, bearing in mind that of course cigarette smoking has to be discouraged due to its well known dangerous effects.

Thus we have to consider, without any preconceived position, on the one hand the notorious unhealthy effects of cigarette smoking, and on the other the possible important scientific information coming from different countries in the world showing that active smokers are somehow ‘protected’ from the severe complications of SARS-CoV-2 infection, namely interstitial pneumonia and ARDS.

In this context a very recent paper reported decreased levels of the SARS-CoV-2 receptor ACE2 in both bronchial and alveolar epithelial cells from cigarette smoking-exposed versus air-exposed mice.7 Furthermore and more importantly, cigarette smoking treatment did not affect ACE2 levels but potently inhibited SARS-CoV-2 replication in Calu3 cells in vitro.7 On the other hand previous studies have reported the opposite effects of cigarette smoking on ACE2 expression in the lung,8 thus underlying the urge for further investigations to finally clarify the role of cigarette smoking on SARS-CoV-2 infection and its severe respiratory complications.

Science proceeds by criticism and by analyzing objective data coming from scientists. In 1939 Winston Churchill said “Criticism may not be agreeable, but it is necessary. It fulfils the same function as pain in the human body; it calls attention to the development of an unhealthy state of things. If it is heeded in time, danger may be averted; if it is suppressed, a fatal distemper may develop”.9

In the case of active smoking and COVID-19, to hide ones head in the sand will not help rapid scientific progress in the discovery of the pathophysiology of this disease and of its possible therapeutic strategies.

Financial support

None.

Conflict of interest

The authors have no conflict of interest to declare.

References
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C.P. Matos, J.P. Boléo-Tomé, P. Rosa, A. Morais.
Tobacco and COVID-19: a position from Sociedade Portuguesa de Pneumologia.
[2]
W.J. Guan, Z.Y. Ni, Y. Hu, W.H. Liang, C.Q. Ou, J.X. He, et al.
Clinical characteristics of coronavirus disease 2019 in China.
N Engl J Med, 382 (2020), pp. 1708-1720
[3]
M. Rossato, L. Russo, S. Mazzocut, A. Di Vincenzo, P. Fioretto, R. Vettor.
Current smoking is not associated with COVID-19.
[4]
X. Wang, X. Fang, Z. Cai, X. Wu, X. Gao, J. Min, et al.
Comorbid chronic diseases and acute organ injuries are strongly correlated with disease severity and mortality among COVID-19 patients: a systemic review and meta-analysis.
Research (Wash DC), (2020),
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W. Liu, Z.W. Tao, L. Wang, M.L. Yuan, K. Liu, L. Zhou, et al.
Analysis of factors associated with disease outcomes in hospitalized patients with 2019 novel coronavirus disease.
Chin Med J, 133 (2020), pp. 1032-1038
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Smoking is associated withCOVID-19 progression: a meta-analysis.
Nicotine Tob Res, 22 (2020), pp. 1653-1656
[7]
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Paradoxical effects of cigarette smoke and COPD on SARS-CoV2 infection and disease.
[8]
S.J. Brake, K. Barnsley, W. Lu, K.D. McAlinden, M.S. Eapen, S.S. Sohal.
Smoking upregulates angiotensin-converting enzyme-2 receptor: a potential adhesion site for novel Coronavirus SARS-CoV-2 (Covid-19).
J Clin Med, 9 (2020), pp. 841
Copyright © 2021. Sociedade Portuguesa de Pneumologia
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