15 April 2020

Tobacco users face an elevated risk for a long list of chronic diseases and malignancies, and there is growing evidence that smoking, and possibly vaping, also increase the risk for life-threatening complications and death from COVID-19.

A study of patients in Wuhan, China, suggested that active smokers with COVID-19 were 2.4 times more likely to experience severe outcomes -- intensive care unit admission, need for mechanical ventilation, or death -- than non-smokers with the disease.

The ACE2 receptor, which is found on the surface of lung cells, is a point of entry for infection with the COVID-19 coronavirus. Furthermore, a recent publication (European Respiratory Journal 2020; DOI: 10.1183/13993003.00688-20200) indicates that current smokers and patients with chronic obstructive pulmonary disease (COPD) show increased lung expression of the transmembrane angiotensin converting enzyme II (ACE2) receptor. Current smokers had significantly higher levels of ACE2 expression in their airways compared to never smokers (2.77±0.91 log2 counts per million reads vs 2.00±1.23 and 1.78±0.39, respectively; P=0.024.  Similarly, patients with COPD had higher ACE2 expression compared with non-COPD patients (2.52±0.66 vs 1.70±0.51; P=0.00076).

"Active cigarette smoking and COPD upregulate ACE2 expression in lower airways, which in part may explain the increased risk of severe COVID-19 in these populations," the researchers wrote, adding that the findings "highlight the importance of smoking cessation for these individuals and increased surveillance of these risk subgroups for prevention and rapid diagnosis of this potentially deadly disease."

The US Centers for Disease Control have recently identified smoking as a potential risk factor for coronavirus-related severe disease or death, based on findings from more than 122,000 U.S. cases and case studies from China and Italy. In addition, the WHO have reported that "tobacco users are probably less likely to become infected if they quit because the absence of smoking helps reduce the touching of fingers to the mouth.”

Smoking leads to chronic airway inflammation which is associated with decreases in lung immune defenses, such as fighting off viral and bacterial infections. In addition, smoking has long been recognized to suppress mucociliary clearance in most smokers making the removal of pathogens from infected lungs more problematic. Within minutes to hours of smoking cessation, nicotine and carbon monoxide levels decline and coughing, sputum production and wheezing can all improve over the course of days to weeks and these are associated with improvements in tobacco-related lung inflammation. In the current COVID-19 pandemic now is the perfect time for smokers to quit.

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