A Systematic Review and Meta-Analysis of Hospitalised Current Smokers and COVID-19

Abstract

SARS-CoV-2 is a new coronavirus that has caused a worldwide pandemic. It produces severe acute respiratory disease (COVID-19), which is fatal in many cases, characterised by the cytokine release syndrome (CRS). According to the World Health Organization, those who smoke are likely to be more vulnerable to infection. Here, in order to clarify the epidemiologic relationship between smoking and COVID-19, we present a systematic literature review until 28th April 2020 and a meta-analysis. We included 18 recent COVID-19 clinical and epidemiological studies based on smoking patient status from 720 initial studies in China, the USA, and Italy. The percentage of hospitalised current smokers was 7.7% (95% CI: 6.9–8.4) in China, 2.3% (95% CI: 1.7–2.9) in the USA and 7.6% (95% CI: 4.2–11.0) in Italy. These percentages were compared to the smoking prevalence of each country and statistically significant differences were found in them all (p < 0.0001). By means of the meta-analysis, we offer epidemiological evidence showing that smokers were statistically less likely to be hospitalised (OR = 0.18, 95% CI: 0.14–0.23, p < 0.01). In conclusion, the analysis of data from 18 studies shows a much lower percentage of hospitalised current smokers than expected. As more studies become available, this trend should be checked to obtain conclusive results and to explore, where appropriate, the underlying mechanism of the severe progression and adverse outcomes of COVID-19.

Characteristics of Critically Ill Patients with COVID-19 Compared to Patients with Influenza—A Single Center Experience

“…The low prevalence of smokers among our COVID-19 patients is remarkable. This is in line with a few publications claiming lower rates of SARS-CoV-2 infections in countries with a high prevalence of smoking, a lower number of hospitalized current smokers than expected [ 33 ] and even leading to a controversial and probably premature suggestion for considering nicotine as a therapeutic option [ 34 ]. Nicotine acts in a similar fashion as the naturally occurring neurotransmitter acetylcholine on nicotinic acetylcholine receptors and may act as an anti-inflammatory agent [ 35 ].…”

Chronic comorbidities and clinical outcomes in patients with and without COVID-19: a large population-based study using national administrative healthcare open data of Mexico

“…Immunity system is weaker in male than in female sex, therefore men are at higher risk of viral infection than women [ 22 ]. Because the low prevalence of smoking in patients hospitalized with COVID-19 [ 23 , 24 ], the protective effect of tobacco is largely discussed [ 25 ]; however, several meta-analyses of observational studies have confirmed that smoking habit is related to severe COVID-19 and adverse outcomes [ 19 , 21 , 26 – 28 ]. Tobacco smoking is associated with upregulation of the angiotensin-converting-enzyme-2 (ACE2), immune system disturbance, endothelial injury and hypercoagulable state [ 28 , 29 ]; these factors and pre-existing comorbidities could explain adverse outcomes observed in smokers with COVID-19.…”

Littérature médicale et COVID-19 : comment trois articles ont influencé les médias et la décision publique en France

“…Depuis la publication de cet avis, la version 4 du manuscrit a été consultée 205 196 fois (au 10 janvier 2021), et de nombreux articles publiés dans des revues classiques, sur des serveurs communautaires, ou auprès de revues dites disruptives, ont confirmé la moindre prévalence de fumeurs parmi les patients hospitalisés pour COVID-19 et se sont interrogés sur les éventuels liens entre tabac ou nicotine et COVID-19 [25] , [26] , [27] et/ou sur la communication de résultats pouvant générer des comportements individuels à risque [28] .…”