Impact of Smoking on COVID-19 Outcomes

Smoking has emerged as a significant determinant of COVID-19 progression and mortality, with evidence indicating that both current and former tobacco use exacerbate disease severity. Tobacco smoke impairs mucociliary clearance, disrupts innate and adaptive immune responses, and upregulates receptors facilitating viral entry in the respiratory epithelium. Clinically, smokers are more likely to require hospitalisation, intensive care admission and mechanical ventilation, while former smokers frequently exhibit higher mortality than never smokers. These findings underscore the global importance of tobacco control and cessation efforts as part of comprehensive strategies to reduce COVID-19 morbidity and mortality.

Research from Nature Portfolio

Analysis of a hospitalised cohort in Northern Italy identified current smoking as an independent predictor of in-hospital mortality, alongside age, cancer and obesity. This foundational study demonstrated that smokers admitted with COVID-19 exhibited poorer gas exchange—reflected in lower PaO2/FiO2 ratios—and a heightened fatality rate nearing 30%. These insights have informed clinical risk stratification tools and reinforced the need to consider smoking status in patient triage and management.

Impact of Smoking on COVID-19 Outcomes publication trend

The graph below shows the total number of articles in impact of smoking on covid-19 outcomes across all publications each year (not limited to Nature Index journals).

Technical terms

ACE2: A membrane-bound enzyme that serves as the primary cellular entry receptor for SARS-CoV-2.

TMPRSS2: A transmembrane serine protease that cleaves and activates the viral spike protein, enabling host cell fusion.

PaO2/FiO2 ratio: The arterial oxygen partial pressure to inspired oxygen fraction ratio, used to assess pulmonary gas exchange efficiency.

Mendelian randomisation: A genetic epidemiology method that uses inherited genetic variants as proxies for modifiable exposures to infer causal relationships.

Benzo[a]pyrene: A carcinogenic polycyclic aromatic hydrocarbon present in tobacco smoke that can modulate gene expression and inflammatory pathways.

References

1. Smoke and Spike: Benzo[a]pyrene Enhances SARS‐CoV‐2 Infection by Boosting NR4A2‐Induced ACE2 and TMPRSS2 Expression. Advanced Science (2023).
2. Risk of death due to COVID-19 among current and former smokers in the Netherlands: a population-based quasi-cohort study. International Journal of Epidemiology (2024).
3. Smoking and COVID-19 outcomes: an observational and Mendelian randomisation study using the UK Biobank cohort. Thorax (2021).
4. Fatality rate and predictors of mortality in an Italian cohort of hospitalized COVID-19 patients. Scientific Reports (2020).