By Maki Komiyama, Koji Hasegawa
National Hospital Organization Kyoto Medical Center, Kyoto, Japan
COVID-19, which is caused by severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2, commonly called the novel coronavirus), to be a public health emergency of international concern.1 Smoking adversely affects the immune system. with the previous Middle East respiratory syndrome-coronavirus (MERS-CoV) outbreaks, smoking was reported to be a risk factor for MERS-CoV infection, and a higher mortality rate was reported in smokers.2 However, the effects of cigarette smoking on the transmission of the virus and worsening of COVID-19 have been less addressed.
Explanation and Comment
Emerging data indicate increased risk for infection, morbidity, and high mortality of SARS-CoV-2 in individuals with a history of smoking. Cigarette smoking increases the expression of ACE2, a SARS-CoV-2 receptor, in pulmonary tissues,3 which may, in part, account for the increased risk for infection. Additionally, the WHO has noted that smokers perform repeated hand–face reciprocal movements which contribute to increased opportunity for virus entry.4 In a report on 1,099 infected individuals from China, 12.4% of current smokers and 23.8% of past smokers developed critical outcomes including those either admitted into an intensive care unit, fitted with a ventilator, or died. On the other hand, only 4.7% of never smokers resulted in such critical situations.5 A small study from China using multivariate analysis demonstrated that the odds ratio for smoking history associated with disease deterioration was the highest, at 14, (confidence interval [CI]: 1.6–45; p = 0.018).6 Smoking cessation recovers airway ciliary clearance and immune function as early as one month.7
Smoking cessation awareness is strongly encouraged as part of the public health measures aiming to limit the global impact of COVID-19.
- World Health Organization. Coronavirus disease (COVID-19) outbreak https://www.who.int/emergencies/diseases/novel-coronavirus-2019
- Park JE, Jung S, Kim A. MERS transmission and risk factors: a systematic review. BMC Public Health. 2018;18(1):574. doi: 10.1186/s12889-018-5484-8.
- Wenhua Liang, et al. Cancer patients in SARS-CoV-2 infection: a nationwide analysis in China. Lancet Oncology 2020;21:335-337
- World Health Organization. Q & A on smoking and COVID-19. https://www.who.int/news-room/q-a-detail/q-a-on-smoking-and-covid-19
- Guan W, Ni Z, Hu Y, et al. Clinical Characteristics of Coronavirus Disease 2019 in China. N Engl J Med 2020; NEJMoa2002032.
- Liu W, Tao ZW, Lei W, Ming-Li Y, Kui L, Ling Z, et al. Analysis of factors associated with disease outcomes in hospitalized patients with 2019 novel coronavirus disease. Chin Med J (Engl). Feb 28, 2020. doi: 10.1097/CM9.0000000000000775.
- Komiyama M, Hasegawa K. Smoking Cessation As A Public Health Measure To Limit The Coronavirus Disease 2019 Pandemic. European Cardiology Review 2020;15:e16. DOI https://doi.org/10.15420/ecr.2020.11