COVID-19 March 31, 2020 Update
Keeping the immune system healthy is on most people’s minds during the current COVID-19 pandemic. According to epidemiological data, smoking increases susceptibility and severity of flu caused by the influenza virus.1 And experimental data have shown that cigarette smoke directly inhibits epithelial antiviral pathways and increases replication of influenza virus.2 There are also data showing higher mortality among smokers in the 2012 outbreak caused by a coronavirus known as MERS-CoV.3 However, as SARS-CoV-2 is a novel coronavirus, the link between COVID-19 outcomes and smoking status remained unknown.
Until recently. Two researchers conducted a literature search and identified five recently published studies that contained data on COVID-19 outcomes and smoking status, all published during the first two months of the COVID-19 outbreak.4 Sample size ranged from 41 to 1,099 patients.
The researchers found unfavorable outcomes associated with smoking status. For example, they estimated based on the study with the most patient cases (n=1099) that:4
- Smokers were 1.4 times more likely to have severe symptoms of COVID-19 compared with nonsmokers
- Smokers were 2.4 times more likely to be admitted to an ICU, need mechanical ventilation, or die compared with nonsmokers
Similar observations were seen in the other four studies with smaller sample sizes.
As the COVID-19 outbreak is progressing and new cases are unfortunately growing rapidly, these early data (from the first two months of the outbreak) are no longer current. Also, these data are too limited in sample size to allow for more objective and comprehensive statistical analysis. Nevertheless, a pattern is emerging, and the researchers indicated that smoking is most likely linked to negative progression and adverse outcomes of the COVID-19 pandemic.
These findings were published on March 20, 2020, in the journal Tobacco Induced Diseases.
What are the key takeaways?
- Smoking is linked to severity of COVID-19 infection and higher risks of ICU admission, need for mechanical ventilation, and mortality rate
- Smoking is also linked to higher risks of other viral infections such as flu; smoking cessation is a life-saving lifestyle change
- Arcavi L et al. Cigarette smoking and infection. Arch Intern Med. 2004;164:2206-2216.
- Noah TL et al. Alteration of the nasal responses to influenza virus by tobacco smoke. Curr Opin Allergy Clin Immunol. 2012;12:24-31.
- Park JE et al. MERS transmission and risk factors: a systematic review. BMC Public Health. 2018;18:574.
- Vardavas CI et al. COVID-19 and smoking: a systematic review of the evidence. Tob Induc Dis. 2020;18:20.