Sorting out fact from fiction: tobacco and COVID-19

• We know that exposure to tobacco smoke is a major risk factor for lung diseases (1) and smoking is a significant risk factor for bacterial and viral infections. (2)
• However, a study from the Pitié-Salpêtrière hospital calls into question the impact of tobacco in patients with Covid-19 since the rate of smokers was 4.4 to 5.3% compared to just over 20 % in the general population. (3) The results of this observational study cannot confirm that tobacco would have a protective effect against SARS-CoV-2 infection since it presents several biases such as the small sample, the absence of a control group, in addition to the fact that more than 65% of the patients in the series are former smokers.
• Recent studies report that smoking is associated with increased expression of angiotensin-converting enzyme 2 (ACE2) receptors which play a primary role for SARS-COV-2 virus infestation of host cells ( 4-7) and that exposure to nicotine can increase the risk of COVID-19 not only in the lungs but also in the brain. (8) The Chinese study with the largest number of COVID-19 patients compared severe cases (N=173) to non-severe cases (N=926). The percentage of active and quit smokers was higher among severe cases (17% and 5%, respectively) than among non-serious cases (12% and 1%, respectively). (9) Smokers were also twice as likely to be admitted to intensive care or to be intubated (26 vs 12%). (9)
• Based on these data, learned societies and the World Health Organization (WHO) have issued warnings against smoking as a risk factor for COVID-19 infection and severity and recommended cessation. smoking especially in vulnerable patients (elderly people, people with cardiovascular or pulmonary disorders, diabetes, etc.). (10, 11)

References :

• 1 - Strzelak A, Ratajczak A, Adamiec A, Feleszko W. Tobacco smoke induces and alters immune responses in the lung triggering inflammation, allergy, asthma and other lung diseases: A mechanistic review. Int J Environ Res Public Health. 2018;15(5):1033. Published 2018 May 21. doi:10.3390/ijerph15051033
• 2 - Arcavi L, Benowitz NL. Cigarette smoking and infection. Arch Intern Med. 2004;164(20):2206–2216. doi:10.1001/archinte.164.20.2206
• 3 - Miyara et al. (2020). Low incidence of daily active tobacco smoking in patients with symptomatic COVID-19. Qeios. doi:10.32388/WPP19W.3
• 4 - Cai G. Bulk and single-cell transcriptomics identify tobacco-use disparity in lung gene expression of ACE2, the receptor of 2019-nCov. medRxiv preprint doi: https://doi.org/10.1101/2020.02.05.20020107.
• 5 - Brake et al. Smoking Upregulates Angiotensin-Converting Enzyme-2 Receptor: A Potential Adhesion Site for Novel Coronavirus SARS-CoV-2 (Covid-19). J. Clin. Med. 2020, 9(3), 841; https://doi.org/10.3390/jcm9030841
• 6 - Leung et al. ACE-2 Expression in the Small Airway Epithelia of Smokers and COPD Patients: Implications for COVID-19. Eur Respir J 2020; in press https://doi.org/10.1183/13993003.00688-2020.
• 7 - Olds & Kabbani: Is nicotine exposure linked to cardiopulmonary vulnerability to COVID-19 in the general population? The FEBS Journal. doi:10.1111/febs.15303
• 8 - Kabbani & Olds. Does COVID19 infect the brain? If so, smokers might be at a higher risk. Molecular Pharmacology Fast Forward. Published on April 1, 2020 as DOI: 10.1124/molpharm.120.000014
• 9 - Guan WJ, Ni ZY, Hu Y, et al. Clinical Characteristics of coronavirus disease 2019 in China [published online ahead of print, 2020 Feb 28]. N Engl J Med. 2020 doi:10.1056/NEJMoa2002032
• 10 - Coronavirus/COVID-19 and smoking: the importance of quitting smoking. Francophone Society of Tabacology (SFT); press release March 25, 2020. [Accessed May 05, 2020 at http://www.societe-francophone-de-tabacologie.org/dl/SFT-CP-Tabac-et-Covid19-2020_03_25.pdf].
• Q&A on smoking and COVID-19. WHO 2020. [Accessed 05 May 2020 at https://www.who.int/news-room/q-a-detail/q-a-on-smoking-and-covid-19].