Current tobacco use and COVID-19 diagnoses in a cohort of adult clients of public dental clinics in Sweden

The Association Between Tobacco Use and Risk of COVID-19 Infection and Clinical Outcomes in Sweden: A Population-Based Study

Background: The association between tobacco use and COVID-19 is controversial. During the early course of the pandemic, limited testing prevented studying a wide spectrum of clinical manifestations. Objective: To examine the potential causal association between tobacco use and COVID-19 during the second wave (1 October 2020-30 June 2021) of the pandemic in Stockholm, Sweden. Methods: A population-based cohort study was conducted in the Stockholm region of Sweden, with information on tobacco use collected prior to the pandemic. Adjusted relative risks (RR) of COVID-19 and 95% confidence intervals (CI) were calculated, contrasting current smokers and snus users to non-users of tobacco. Results: Compared with non-users of tobacco, current smokers had a lower risk of COVID-19 (RR 0.78, 95% CI = 0.75-0.81) and of hospitalisation for the disease. Current snus users had a higher risk of COVID-19. Heavy smokers and snus users had longer hospital stays than non-users of tobacco. Conclusion: Tobacco use may have a different impact on the risk of being infected with SARS-CoV-2 and the risk of developing severe clinical manifestations. Further research is needed to determine the underlying mechanisms.

Current tobacco use and SARS-CoV-2 infection in two Norwegian population-based cohorts

BACKGROUND

Clear evidence of an increased risk for SARS-CoV-2 infection among smokers has not been established. We aimed to investigate associations between cigarette smoking or use of snus (snuff) and other nicotine-containing products and a positive SARS-CoV-2 test, taking test behavior into account.

METHODS

Current tobacco use and testing behavior during the pandemic were recorded by adult participants from the Norwegian Mother, Father and Child Cohort Study and The Norwegian Influenza Pregnancy Cohort. SARS-CoV-2 infection status was obtained from The Norwegian Surveillance System for Communicable Diseases (MSIS) in May 2021 (n = 78,860) and antibody measurements (n = 5581). We used logistic regression models stratified by gender and adjusted for age, education, region, number of household members, and work situation.

RESULTS

Snus use was more common among men (26%) than women (9%) and more prevalent than cigarette smoking. We found no clear associations between cigarette smoking or snus and a COVID-19 diagnosis among men. Associations among women were conflicting, indicating that cigarette smoke was negatively associated with a diagnosis (OR 0.51, 95% CI 0.35, 0.75), while no association was found for snus use (OR 1.07, 95% CI 0.86, 1.34). Compared with non-users of tobacco, both cigarette smokers and snus users had increased odds of being tested for SARS-CoV-2.

CONCLUSIONS

Cigarette smoking, but not snus use, was negatively associated with SARS-CoV-2 infection in women. The lack of an association between snus use and SARS-CoV-2 infection in this population with prevalent snus use does not support the hypothesis of a protective effect of nicotine.