The Paradox of the Low Prevalence of Current Smokers Among COVID-19 Patients Hospitalized in Nonintensive Care Wards: Results From an Italian Multicenter Case–Control Study

Abstract

Introduction 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. Methods 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. Results 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). Conclusions 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. Implications 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.

Risk factors for hospitalization among persons with COVID-19—Colorado

“…While smoking was associated with hospitalization in crude analysis, it was not significant in multivariable analysis. Findings of previous studies of smoking and COVID-19 outcomes have been mixed, including increased, decreased, or no impact on risk as was found in this analysis [ 16 , 39 , 57 – 59 ]. Smoking has also been found to causes variable risk for SARS-CoV-2 infection suggesting a potential complex affect [ 60 ].…”

Nicotinic cholinergic system and COVID-19: In silico identification of interactions between α7 nicotinic acetylcholine receptor and the cryptic epitopes of SARS-Co-V and SARS-CoV-2 Spike glycoproteins

“…Published meta-analyses reporting an unusually low pooled prevalence of smoking among hospitalized COVID-19 patients compared with population smoking rates ( Farsalinos et al, 2020 ; Farsalinos et al, 2020a ; Farsalinos et al, 2020b ) bolstered the debate about the connection between smoking and COVID-19. Other studies report that smokers are less likely to be diagnosed with or be hospitalized for COVID-19 ( Farsalinos et al, 2020a ; Farsalinos et al, 2020b ; Hippisley-Cox et al, 2020 ; Kowall et al, 2020 ; Giannouchos et al, 1101 ; Rossato et al, 2020 ; Meini et al, 2020 ; Simons et al, 2020 ), but, once hospitalized, they have higher odds for an adverse outcome ( Farsalinos et al, 2020b ; Alqahtani et al, 2020 ; Vardavas and Nikitara, 2020 ). Cox et al recently published a cohort study of 8.28 million participants, including 19,486 confirmed COVID-19 cases, and found that smoking was associated with lower odds for COVID-19 diagnosis and ICU admission ( Hippisley-Cox et al, 2020 ).…”

Cumulative Incidence of SARS-CoV-2 Infection and Associated Risk Factors Among Frontline Health Care Workers in Paris, France: The SEROCOV Prospective Cohort Study

“…An increasing number of studies have reported this reduced risk of SARS-CoV-2 infection in active smokers in different contexts (cross-sectional studies in the general population; crosssectional, case-control or control studies in different populations). [17][18][19][20][21][22] Our results from a large multicenter prospective study in a young population of HCWs with 26.9% active smokers support the role of use of tobacco substances as protective against SARS-CoV-2 infection, which may act through the nicotine pathway. [23][24][25][26] This result should not encourage smoking to limit the risk of COVID-19; indeed, 78,000 deaths per year are due to smoking in France.…”