COVID-19, a respiratory illness due to SARS-CoV-2 coronavirus, was first described in December 2019 in Wuhan, rapidly evolving into a pandemic. Smoking increases the risk of respiratory infections; thus, cessation represents a huge opportunity for public health. However, there is scarce evidence about if and how smoking affects the risk of SARS-CoV-2 infection.
We performed an observational case-control study, assessing the single-day point prevalence of smoking among 218 COVID-19 adult patients hospitalized in 7 Italian non-intensive care wards and in a control group of 243 patients admitted for other conditions to 7 general wards COVID-19-free. We compared proportions for categorical variables by using the χ2 test and performed univariate and multivariate logistic regression analyses to identify the variables associated with risk of hospitalization for COVID-19.
The percentages of current smokers (4.1% vs 16%, p=0.00003) and never smokers (71.6% vs 56.8%, p=0.0014) were significantly different between COVID-19 and non-COVID 19 patients. COVID-19 patients had lower mean age (69.5 vs 74.2 years, p=0.00085) and were more frequently males (59.2% vs 44%, p=0.0011). In the logistic regression analysis, current smokers were significantly less likely to be hospitalized for COVID-19 compared with non-smokers (Odds ratio 0.23; 95% CI, 0.11-0.48, p<0.001), even after adjusting for age and gender (OR 0.14; 95% CI, 0.06-0.31, p<0.001).
We reported an unexpectedly low prevalence of current smokers among COVID-19 patients hospitalized in non-intensive care wards. The meaning of these preliminary findings, which are in line with those currently emerging in literature, is unclear; they need to be confirmed by larger studies.
An unexpectedly low prevalence of current smokers among patients hospitalized for COVID-19 in some Italian non-intensive care wards is reported. This finding could be a stimulus for the generation of novel hypotheses on individual predisposition and possible strategies for reducing the risk of infection from SARS-CoV-2, and needs to be confirmed by further larger studies designed with adequate methodology.