The association between tobacco smoking, second-hand smoke and novel products, and COVID-19 severity and mortality in Italy. Results from the COSMO-IT study

Background. Despite the robust evidence of an excess risk of COVID-19 severity and mortality in ever smokers, the debate on the role of current and ex-smokers on COVID-19 progression remains open. Limited or no data are available on the link between electronic-cigarette (e-cigarette), heated tobacco product (HTP) and second-hand-smoke (SHS) exposure and COVID-19 progression. To fill this knowledge gap, we undertook the COvid19 and SMOking in ITaly (COSMO-IT) study.Methods. A multi-centre longitudinal study was conducted in 2020-2021 in 24 Italian hospitals on a total of 1820 laboratory-confirmed COVID-19 patients. We estimated multivariable odds ratios (OR) and 95% confidence intervals (CI), to quantify the association between smoking-related behaviours (i.e., smoking status, e-cigarette and HTP use, and SHS exposure) and COVID-19 severity (composite outcome: intubation, intensive care unit admission and death), and mortality.Results. Compared to never smokers, current smokers had an increased risk of COVID-19 mortality (OR=2.17; 95% CI=1.06-4.41). E-cigarette use was non-significantly associated to an increased risk of COVID-19 severity (OR=1.60; 95% CI=0.96-2.67). An increased risk of mortality was observed for exposure to SHS among non-smokers (OR=1.67; 95% CI=1.04-2.68), the risk being particularly evident for exposures of >= 6 hours/day (OR=1.99; 95% CI=1.15-3.44).Conclusions. This multicentric study from Italy shows a dismal COVID-19 progression in current smokers and, for the first time, in SHS exposed non-smokers. These data represent an additional reason to strengthen and enforce effective tobacco control measures and to support smokers in quitting.