JMIR Publications

ABSTRACT

Background:

Several studies reported a low prevalence of current smoking among hospitalized COVID-19 cases however, no definitive conclusions can be drawn.

Objective:

We investigated the association of tobacco smoke exposure with the nasopharyngeal swab (NPS) test result for SARS-CoV-2 infection and the disease severity accounting for possible confounders.

Methods:

The cross-sectional EPICOVID19 web-based survey was performed in an Italian population of 198,822 adults who filled in an online questionnaire between April 13 and June 2, 2020. For the present study we analyzed 6857 individuals with known NPS test result. The association of smoking status and the dose-response relationship with the positivity to NPS test and infection severity were analyzed using logistic and multinomial regression models adjusting for socio-demographic, clinical and behavioral characteristics.

Results:

Out of the 6857 individuals, 63.2% had never smoked, 21.3% were former and 15.5% were current smokers. Compared to non-smokers, current smokers were younger, more educated, less affected by chronic diseases, reported less frequently COVID-like symptoms, were less hospitalized and tested for COVID-19. In multivariate analysis current smokers had almost halved odds of a positive NPS test (OR 0.54, 95% CI 0.45-0.65) compared to non-smokers. We also found a dose-dependent relationship with tobacco smoke: mild smokers (OR 0.76, 95% CI 0.55-1.05), moderate (OR 0.56, 95% CI 0.42-0.73) and heavy smokers (OR 0.38, 95% CI 0.27-0.53). This inverse association persisted also when considering the severity of the infection.

Conclusions:

Current smoking was negatively associated with SARS-CoV-2 infection with a dose-dependent relation. Ad-hoc experimental studies are needed to elucidate the mechanisms underlying this association. Clinical Trial: ClinicalTrials.gov NCT04471701