The Paradoxical Relationship Between Nicotine and SARS-CoV-2 Infection: A Systematic Review

Abstract

Across the board, smoking is considered to be negative toward our health. While this information has been known for a relatively long time, the COVID-19 pandemic has stirred up a controversial idea: that smokers are protected from severe COVID-19 relative to non-smokers. This suggests that smoking is a helpful agent in the evolving fight against SARS-CoV-2, and impressionable individuals are at risk of starting to smoke as a means of protecting themselves from the virus. To address the validity of this claim, a systematic review was done according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. PubMed was searched for relevant articles and the results were screened according to inclusion criteria. Our search yielded a total of 81 results and after removal of duplicates, non-English papers, and a quality appraisal a total of 16 papers were included in this review. We found that while smokers were more likely present with a less severe disease due to downregulation of severe cytokine storm, they were overall more likely to contract COVID-19 due to upregulation of ACE-2 receptors which SARS-CoV-2 uses to enter the cells of the respiratory epithelium. Also, long time smokers who develop COPD are more likely to have fatal outcomes from COVID-19 infection. Further, these results were due to the effects of nicotine and not cigarettes themselves. Since cigarettes contain numerous carcinogens, they are not recommended as a prophylaxis for COVID-19. However, we recommend that nicotine should be a topic for further research as potential therapy.