[COVID-19 and Smoking: A Systematic Review and Meta-Analysis of the Evidence]

The aim of this study was to determine if tobacco use in patients with Covid-19 is associated with a negative disease course and adverse outcome, and if smoking, current and past, is associated with a greater possibility of developing COVID-19.

A systematic review (SR) and meta-analysis (MA) of previously published works were performed. The search strategy included all known descriptors for Covid-19 and tobacco and was conducted in different databases. Appropriate statistical models were used to address the effect size in meta-analysis, namely random effects and fixed effects model.

Thirty-four articles were identified in the SR of which 19 were included in the MA. Being a smoker or former smoker was shown to be a risk factor for worse progression of Covid-19 infection (OR 1.96, 95% CI, 1.36 - 2.83) and a greater probability of presenting a more critical condition (OR 1.79 95% CI, 1.19 - 2.70). As limitations of the MA, we found that most of the studies analyzed were observational with limited publication bias. Two studies that disagreed with the rest were included, although after withdrawing them from the MA, smoking was maintained as a risk factor for worse progress.

Current and past smoking produces a more serious clinical form of Covid-19 and more frequently leads to intensive care admission, intubation, and death.