Can smoking increase the likelihood and severity of COVID-19?

Earlier this week, The European Centre for Disease Prevention and Control (ECDC) included smokers on the list of those most vulnerable to COVID-19. Though there is currently not sufficient evidence linking smoking to COVID-19, it is established that smoking damages the lining of the lungs and increases the likelihood of contracting influenza-like diseases. Smoking also increases the likelihood of getting conditions like COPD, heart disease and asthma. All of these underlying conditions are linked with more dire COVID-19 prognoses. 

Representational image. Image source: Getty Images.

The stance of the WHO

According to the WHO, smoking can increase the likelihood of getting COVID-19 because of behavioural factors as well. Smokers constantly put their fingers to their lips when holding a cigarette, thereby transporting germs from their hands to their mouths. Transmitting the virus from the hands to the mouth is the most common way of getting the disease. Further, smokers may also share cigarettes which again increases the chances of spreading germs. 

Smokers are also likely to have diminished lung capacity, and long term smokers are highly likely to have lung damage. All of these factors place them in higher-risk groups.

How does smoking damage the lungs?

The airway is lined with hairlike structures known as cilia that are constantly moving and drawing toxins and mucus away from the lungs. In heavy smokers, the functionality of the cilia is impaired, meaning that mucus and toxins cannot be cleared out as efficiently. When the immune system responds to infections, it releases lymphocytes. Because the lymphocytes cannot be cleared as efficiently from the area, it causes inflammation. This leads to lung damage and lower capacity. 

Further, studies have suggested that smoking is associated with higher levels of ACE2 receptors in the body. This is the enzyme present on cell membranes onto which SARS-CoV-2 (which causes COVID-19) implants itself. An increase in ACE2 receptors implies that the virus may be able to invade the body more easily.

What does data on the ground suggest?

Smoking was initially suggested as a complicating factor after Chinese studies showed that men were more likely to get more severely sick from COVID-19 than women. According to earlier studies, men had a mortality rate of 2.8% whereas the figure was 1.7% for women. What could explain the discrepancy? Commentators pointed to smoking figures - 50% of Chinese men smoke whereas only 2% of women do. However, similar data have begun to emerge from Italy where men have reportedly accounted for 71% of deaths, and Spain where twice the number of men have died. The smoking rates are not so different in these countries so they can’t adequately explain these differences. It appears that behavioural and genetic factors are probably at play, with smoking having a smaller influence. 

There have been some small studies disaggregating patients by smoking behaviour. A Chinese study published in February - which consisted of 1,099 patients - showed that out of those admitted to the ICU, 25.5% were smokers. This was more than twice the number of smokers compared to the group that did not have severe symptoms.

However, conclusive data are lacking; we will learn more as the disease progresses. From what we know about what smoking does to the body, it is recommended to smokers to give up their habit if they can. Even small periods of abstinence have a positive impact on the body. 

For more tips, read our article on How to Quit Smoking.

Health articles in Firstpost are written by myUpchar.com, India’s first and biggest resource for verified medical information. At myUpchar, researchers and journalists work with doctors to bring you information on all things health.