Smokers Are at an Increased Risk of Developing Symptomatic COVID-19

Smokers are at an increased risk of developing symptomatic coronavirus 2019 (COVID-19).

Smokers are at an increased risk of developing symptomatic coronavirus 2019 (COVID-19), according to study results published in Thorax.

Smoking is a significant risk factor for both viral and bacterial infections of the respiratory system, and therefore may be an important factor in an individual’s risk of developing symptomatic COVID-19. Researchers investigated the association between current tobacco smoking, the risk of developing symptomatic COVID-19, and the severity of illness by analyzing data from United Kingdom users of a COVID-19 symptom-reporting app developed by Zoe Global.

Users provided baseline data including demographics, anthropometrics, smoking status, and medical conditions, and were asked to log their condition daily. Participants who reported that they did not feel physically normal were then asked by the app to complete a series of questions, including 14 potential COVID-19 symptoms and about hospital attendance. The main study outcome was the development of “classic” symptoms of COVID-19 defined as fever, new persistent cough, and breathlessness, and their association with current smoking. The number of concurrent COVID-19 symptoms was used as a proxy for severity and the pattern of association between symptoms was also compared between smokers and nonsmokers.

Between March 24 and April 23, 2020, data were available for 2,401,982 participants, with a mean age of 43.6 years, 63.3% were women, and an overall smoking prevalence of 11.0%. A total of 35% (834,437) of participants reported being unwell and entered 1 or more symptoms. Current smokers were more likely to report the “classic” 3 symptoms suggesting a diagnosis of COVID-19 (odds ratio [OR], 1.14; 95% CI, 1.10-1.18), more than 5 symptoms (OR, 1.29; 95% CI, 1.26-1.31), and more than 10 symptoms (OR, 1.50; 95% CI, 1.42-1.58). The pattern of association between reported symptoms did not vary between smokers and nonsmokers, which indicates that the increased symptom burden cannot be explained by preexisting smoking-related symptoms.

The researchers pointed out that behavioral factors or individual expectations may have effected reporting; thus, smokers may have felt to be at a higher risk of developing COVID-19 making them more likely to report symptoms which could have potentially overestimated the effect of smoking. However, nonsmokers being generally healthier, may have been more sensitive to any physical changes, which could have led to underestimating the effect of smoking. In addition, all participants were self-selected, choosing to register to use the app, which was only available on smartphones. This raises the issue of digital access/literary; therefore, caution should be used when extrapolating to other populations (eg, older or poorer groups).

“Our results provide compelling evidence for an association between current smoking and individual risk from COVID-19, including self-reported symptom burden and risk of attending hospital,” concluded the study authors. “Smoking cessation should be incorporated into public health campaigns and other efforts to address the COVID-19 pandemic.”

Disclosure: This clinical trial was supported by Zoe Global Limited. Please see the original reference for a full list of authors’ disclosures.  


Hopkinson NS, Rossi N, El-Sayed_Moustafa J, et al. Current smoking and COVID-19 risk: results from a population symptom app in over 2.4 million people. Thorax. Published online January 5, 2021. doi:10.1136/thoraxjnl-2020-216422