Smoking as a Risk or Protective Factor in Developing and Severity of COVID-19?

Background: Many studies have discussed the relationship between COVID-19 and smoking, but they include many contradictory findings. This study evaluates the relationship between smoking and the incidence and severity of COVID-19 patients in Shahroud City, Iran. Methods: We conducted a cross-sectional analytical study using COVID-19 data. All suspected cases were referred to the registered centers at Shahroud University of Medical Sciences from 21 January 2020 to 20 March 2021. Multivariable logistic regression was conducted to evaluate the relationship between smoking and SARS-COV 2 confirmed cases, and its severity. Results: Overall, it was confirmed that 22.6% of smokers had positive COVID-19 PCR tests compared to 42.1% of non-smokers. COVID-19 is a public health problem, and the results showed that there was a relationship between smoking and COVID-19 confirmed cases and severity. The results showed that smoking, adjusting for other related factors, reduces the odds of COVID-19 by 58%, but increases the odds of severe disease by 89%. Conclusions: In this study, smoking was significantly associated with a low chance of developing COVID-19 disease but higher odds of severity. These significant results were reported even in the presence of under-reporting of smoking by patients, which underestimates the association. These results should not be ignored, and further studies are needed.