Research on the effects of smoking on COVID-19 patients has been inconsistent. To this end, the study titled "Smoking and COVID-19 Results: Observational and Mendelian Randomization using the UK Biobank Cohort" combined observational and Mendelian randomization analysis to better understand this relationship.
The research team analyzed primary care records, COVID-19 test results, hospitalization data and death certificates among 421,469 participants in the UK Biobank from January 2020 to August 2020 to look for associations between smoking and severity of COVID-19 infection.
"There were 421,469 eligible participants, 1,649 confirmed infections, 968 COVID-19-related hospitalizations and 444 COVID-19-related deaths. Current smokers have a higher risk of hospitalization and death compared to never-smokers. In a MR analysis of 281,105 white British participants, a genetically predicted propensity to smoke was associated with a higher risk of infection and hospitalization. Genetically predicted, the higher the number of cigarettes smoked per day, the higher the risk for all outcomes, the researchers report.
After analyzing the data, the team concluded that smoking has a causal effect on the risk of severe COVID-19. On the other hand, countless studies report the opposite. According to the Centers for Disease Control and Prevention (CDC), smokers made up just 1.3% of the COVID-19 cases analyzed, while the adult smoking rate in the United States is 13.7%. Similarly, a review of Chinese data published in the European Journal of Internal Medicine reports that "active smoking does not appear to be significantly associated with an increased risk of COVID-19 progression to severe disease."
Association between smoking and susceptibility to sarS-COV-2 infection
Another study conducted between March 2020 and April 2020 at a large University hospital in France aimed to determine a possible correlation between daily smoking and susceptibility to sarS-COV-2 infection.
After controlling for gender and age data, the researchers estimated the daily percentage of current smokers among COVID-19 infected patients and compared it to the daily percentage of current smokers in the general population of France.
Pooled data indicate that the daily smoking rate among COVID-19 patients is 5.3%, compared with 25.4% among the general population in France. These findings led the researchers to conclude that people who smoked daily were significantly less likely to develop symptoms or severe SARS-COV-2 infection than the general population.