As we mark World No Tobacco Day on May 31, let’s consider the impact of tobacco use on coronavirus (COVID-19) outcomes. The virus has infected more than 5.5 million people in 188 countries and territories, killing more than 350,000.
Tobacco use is causally linked to diseases of nearly all organs of the body. Studies in various countries have found that middle-aged smokers have two to three times the mortality rate of non-smokers of similar age, reducing lifespan by an average of 10 years. Smoking and e-cigarette use increase the risk and severity of pulmonary infections because of damage to upper airways, lung inflammation, and reduced lung and immune function.
It shouldn’t surprise us, then, that initial evidence suggests smoking is also a risk factor for COVID-19, with smokers having 1.91 times the odds of progression in COVID-19 severity compared to non-smokers. This finding is reinforced by another review showing that infection was associated with substantially higher severity and mortality rates in patients with chronic obstructive pulmonary disease (COPD) and among current smokers.
Men are at higher risk of COVID-19 progression
Data from China, the first country to be affected, provides insights into the biology, epidemiology, and clinical characteristics of COVID-19. The sex distribution of affected patients shows a male predominance of cases. Chinese researchers reported in the New England Journal of Medicine that 58.1% of patients across 30 provinces were male. Also, among the initial 425 cases that occurred in Wuhan, 56% were male. Moreover, an article published at the Journal of the American Medical Association noted that death rates among infected men, particularly in their late 40s and older, have exceeded those among women.
In previous outbreaks of coronaviruses, such as SARS and MERS, men were also disproportionally affected. In Hong Kong in 2003, researchers found that men with SARS had a 50 percent higher risk of death than women.
What explains this discrepancy?
A higher prevalence of smoking among men, often resulting in compromised lung function, may help explain their higher COVID-19 fatality rate.
Tobacco use also contributes to the onset of co-occurring conditions such as cardiovascular diseases, lung cancer, COPD, and diabetes. These are more prevalent among males and also increase the risk of disease severity and death among COVID-19 patients.
Data presented in the New England Journal of Medicine article further illustrates the impact that smoking has on COVID-19 progression and mortality in China:
- Among those severely affected by the disease, 16.9% were current smokers and 5.2% former smokers.
- Among patients who were admitted to an intensive care unit, put on ventilation, or died, 25.8% were current smokers and 7.6% were former smokers.
Data from Italy similarly shows that a high proportion of COVID-19 patients had a history of smoking and high rates of COPD and heart disease. Researchers in Indonesia have also found that the high prevalence of smoking among men (one of the world’s highest) is contributing to the high COVID-19 fatality rate in the country.
The epidemic of tobacco use in China
China has the largest smoking population in the world, with around 316 million adult smokers representing nearly one-third of smokers and 40% of tobacco consumption globally. While the prevalence of smoking in women is relatively low at 1.9%, an estimated 48.4% of men are smokers.
In 2010, an estimated 1.2 million premature deaths were attributable to smoking in China, and the three leading causes of death (stroke, heart disease, and COPD) were linked to tobacco use. A recent study also finds China in the midst of a lung cancer epidemic on an unprecedented scale, driven largely by tobacco use and accounting for 21.7% of the country’s total cancer mortality in 2015.
How does smoking affect lung health and COVID-19 risk?
As explained in the 2004 U.S. Surgeon General Report:
“Toxins in tobacco smoke harm the body from the moment they enter through the mouth and nose. They damage tissue and cells all the way to the lungs. When cigarette smoke is inhaled, chemicals from the smoke are absorbed in the lungs. As a result, smoking causes lung diseases… makes chronic lung diseases more severe; and increases the risk for respiratory infections…. Although the lung has ways to protect itself from injury by inhaled agents, these defenses are overwhelmed when cigarette smoke is inhaled repeatedly over time. After years of exposure to cigarette smoke, lung tissue becomes scarred, loses its elasticity, and can no longer exchange air efficiently.”
There is sufficient evidence to infer a causal relationship between smoking and acute respiratory illnesses, including pneumonia. Not only is smoking the predominant underlying cause, but it might increase the frequency or severity of infections. For example, a recent study showed that smoking was consistently associated with a higher risk of hospital admission for influenza. Researchers have also suggested that it could cause an increase in the ACE2 protein in the lungs, the molecule that the coronavirus uses to infect human cells, facilitating viral dissemination and possibly resulting in a higher rate of morbidity in COVID-19 patients.
What to do?
Besides monitoring smoking and e-cigarette use, governments have an obligation to address smoking in their strategies to contain and mitigate the impact of COVID-19. The most cost-effective policy measure for tobacco control is taxation, so governments must act boldly and swiftly to raise taxes on cigarettes and e-cigarettes. This has been shown to reduce and prevent tobacco use, particularly among youth, and hence to improve health and reduce the risk of premature mortality. Taxation would also help to expand the tax base and mobilize additional public revenue for economic recovery initiatives after the pandemic subsides.