This article focuses on:
- Association of smoking with COVID-19
- Smoking is a major risk factor for many respiratory infections, and could also accelerate disease progression in those infected.
- Previous studies have shown that smokers are more likely to contract influenza and exhibit more severe symptoms than nonsmokers.
- Middle East respiratory syndrome coronavirus (MERSCoV) outbreaks, smoking was reported to be a risk factor for MERS-CoV infection and associated with high mortality.
- The mechanisms by which smoking increases the risk of worsening pneumonia include altered airway architecture, inhibition of airway ciliary clearance and reduced immune function.
- Reasons why smoking adversely affects the immune system:
- Smoking reduces CD4+ T-cells (helper T-cells), which promote antibody production in B-cells and activate killer T-cells to attack pathogens.
- Nicotine promotes the secretion of catecholamines and corticosteroids, could impair immune function and suppress the body’s ability to combat infections.
- Nicotine inhibits the production of interleukin-22, which helps suppress lung inflammation and repair damaged cells.
- In COVID-19, as well as in other infectious diseases, the risk of infection and increased disease severity could be higher in smokers.
- According to the WHO, the mortality rate due to SARS-CoV-2 in China is higher among men than women, which might reflect the large sex difference in smoking habits in China.
- The European Centre for Disease Prevention and Control (ECDC) reported that COVID-19 deaths were more frequent among men; a higher smoking rate in men might be attributable to the higher mortality.
- 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 being admitted into an intensive care unit or fitted with a ventilator, or mortality. In comparison, only 4.7% of those who had never smoked developed critical outcomes.11 Additionally, the proportion of patients with severe symptoms was 21.2% among current smokers and 42.9% among past smokers, which was higher compared with those who had never smoked (14.5%).11 In this report, the analysis was just a simple comparison. Usually, past smokers were older than current smokers. Therefore, a high age in past smokers may contribute to their worsening outcomes.
- A small study from China using multivariate analysis identified the following four factors as being associated with COVID-19 deterioration: smoking history, body temperature of >37.3°C at the time of admission, respiratory failure and age ≥60 years.
- Among these, the OR for smoking history was highest at 14, which was higher than the ORs for other factors associated with disease deterioration.
- Multiple studies have shown that ACE-2 is a host receptor for SARS-CoV-2.16 SARS-CoV-2 enters cells through ACE-2 receptors present in mucosal epithelial cells and alveolar tissues in a clathrin-dependent process.
- Cigarette smoking increases the expression of ACE-2 in pulmonary tissues, which could in part account for the increased risk of infection.
- WHO has noted that smokers perform repeated hand to face reciprocal movements, which contribute to increased opportunity for virus entry.
- ACE inhibitors and angiotensin-receptor blockers also increase the expression of ACE-2 receptors, which increases the risk of COVID-19 infection.
- European Society of Cardiology have issued alerts that patients with cardiovascular diseases discontinue ACE inhibitors and angiotensinreceptor blockers.
- Switching to calcium antagonists has been suggested.
- Cigarette smoking decreases lung function and poses a general risk factor for severe respiratory infections.
- Smokers are likely to be at serious risk for contracting SARS-CoV-2 infection.
- Smoking cessation recovers airway ciliary clearance and immune function as early as 1 month. Thus, smoking cessation awareness is strongly encouraged as part of public health measures to limit the global impact of COVID-19.
Reference Link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7199122/