Tobacco use in all forms, whether smoking or chewing, is significantly associated with severe COVID-19 outcomes. Pre-existing comorbidities in tobacco users such as cardiovascular diseases, diabetes, respiratory diseases and hypertension were found to further aggravate the disease manifestations making the treatment of such COVID-19 patients more challenging due to their rapid clinical deterioration. Tobacco smoke is known to induce and alter immune responses in the lungs, triggering inflammation, allergy, asthma, and other lung diseases.
Role of ACE2 receptors in COVID-19 severity in tobacco users
COVID-19 infections begin at the ACE2 receptor, a neurotransmitter protein present on the surface of the cells and tissues in the lungs, heart, blood vessels, kidneys, liver, intestines, and epithelial cells in the upper and lower respiratory tracts. ACE2 is a critical mediator of the renin-angiotensin system (RAS) signaling throughout the body and its dysfunction leads to critical congestive heart failure, acute lung disease, and cardiorenal metabolic syndrome which closely resemble the symptoms associated with SARS-CoV-2 infection.
Nicotine is known to disrupt the homeostasis of the RAS in multiple organs, which can lead to the development of cardiovascular and pulmonary diseases. And it acts on nicotinic acetylcholine receptors (nACE), it can possibly, promote SARS-CoV-2 entry and proliferation in epithelial cells through co-expression of ACE2.
Because a SARS-CoV-2 virus contains spike-like coat proteins, it can plug into human ACE2 receptors, inject its genetic material, replicate itself, rupture the host cell, then spread further.
Lungs exposed to cigarette smoke are shown to accumulate abnormally large numbers of ACE2 receptors in the human respiratory tract, making it more vulnerable to damage for active tobacco use can provide a cellular mechanism for viral susceptibility and disease severity during the course of the infection in the lungs. The viral entry in the human body has been shown to cause a ‘cytokine storm’ involving elevated levels of inflammatory cytokines which get augmented in smokers. Possibly, an exogenous supplement of recombinant human (Rh) ACE2 in soluble form might be utilized in the prevention and treatment of COVID-19 as ACE2 may act as the bait to neutralize the spike protein on the surface of the SARS-CoV-2.
Tobacco use in the vulnerable population, including adolescents
Patient with smoking habit increases the chances of death from COVID-19 by a staggering 80% and 2.4 times more likely to be admitted to an ICU, requiring mechanical ventilation.
Adolescents are highly vulnerable to tobacco addiction because of COVID-19 pandemic as a sort of mental health ‘therapy’ to relieve depression and anxiety associated with the social isolation resulting from extended quarantine. Smoking is viewed as a means of reversing negative mood, anxiety, and irritability associated with nicotine withdrawal.
COVID-19 infection causes critically low levels of blood oxygen (i.e. hypoxemia) due to damage and inflammation of the alveoli in the lungs and they are unable to transfer oxygen to the small blood capillaries. This severe decrease in oxygen saturation occurs without any visible symptoms of hypoxia and causes rapid deterioration of the patient’s clinical condition. The elevated level of hemoglobin is found to be a strong predictor of acute respiratory distress syndrome (ARDS).
Epidemiological data show that SARS-CoV-2 can spread through human-to-human transmission by direct means i.e. small droplets from the nose or mouth, which are spread when an infected person coughs or exhale or by indirect contact with contaminated objects and airborne contagion where the virus can survive for a few hours to several days.
Smokers have a higher risk of getting coronavirus because they are constantly putting their hands to their lips while tobacco chewers often touch their mouths with their fingers during product use. Smoking products such as water pipes often involve the sharing of mouthpieces and hoses, which could facilitate the transmission of COVID-19, especially in communal and social gatherings. Cigarette and bidis butts are often discarded in open after use can also be a means of virus transmission. Chewing tobacco products can increase the production of saliva followed by a very strong urge to spit and the virus can be spread when the user spits out the excess saliva produced during the chewing process.
There is a very close association between tobacco use and severe COVID-19 manifestations. Tobacco use could be a potential risk factor for, not only contracting the viral infection but also making the treatment of such COVID-19 patients more challenging. Hopefully, the COVID-19 pandemic could just prove to be the game-changer and a teachable moment that we have been waiting for, to ultimately achieve a tobacco-free world.
Source from : Tobacco use as a well-recognized cause of severe COVID-19 manifestations, Respiratory Medicine 176 (2021),
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https://exposetobacco.org/resource/review-two-french-studies/