The Effect of Smoking on COVID-19 Symptom Severity: Systematic Review and Meta-Analysis

Abstract

Background. Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SAR2-COV-2) and was first identified in Wuhan, China, in December of 2019, but quickly spread to the rest of the world, causing a pandemic. While some studies have found no link between smoking status and severe COVID-19, others demonstrated a significant one. The present study aimed to determine the relationship between smoking and clinical COVID-19 severity via a systematic meta-analysis approach. Methods. We searched the Google Scholar, PubMed, Scopus, Web of Science, and Embase databases to identify clinical studies suitable for inclusion in this meta-analysis. Studies reporting smoking status and comparing nonsevere and severe patients were included. Nonsevere cases were described as mild, common type, nonintensive care unit (ICU) treatment, survivors, and severe cases as critical, need for ICU, refractory, and nonsurvivors. Results. A total of 16 articles detailing 11322 COVID-19 patients were included. Our meta-analysis revealed a relationship between a history of smoking and severe COVID-19 cases (OR=2.17; 95% CI: 1.37–3.46; P<.001). Additionally, we found an association between the current smoking status and severe COVID-19 (OR=1.51; 95% CI: 1.12–2.05; P<.008). In 10.7% (978/9067) of nonsmokers, COVID-19 was severe, while in active smokers, severe COVID-19 occurred in 21.2% (65/305) of cases. Conclusion. Active smoking and a history of smoking are clearly associated with severe COVID-19. The SARS-COV-2 epidemic should serve as an impetus for patients and those at risk to maintain good health practices and discontinue smoking. The trial is registered with the International Prospective Register of Systematic Reviews (PROSPERO) CRD42020180173.

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][27][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.…”

Smoking and risk of negative outcomes among COVID-19 patients: A systematic review and meta-analysis

“…Most studies reported smoking history instead of current smoking, which might include former smokers and therefore underestimate current smoking status among COVID-19 patients 70 . Second, former smokers have longer exposure period or accompanying diseases such as asthma, COPD due to smoking 18 . As a result, former smoking showed higher risk of negative outcomes compared with current smoking.…”

“…The differences between risk of severity and death between former and never smoker COVID-19 patients have not been shown [11][12][13] . Because of small sample sizes included in these previous studies and differing definitions of disease severity, existing systematic reviews and meta-analyses found limited evidence suggesting that the risk of COVID-19 infection maybe lower among smokers compared to non-smokers, albeit from highly heterogeneous studies [14][15][16][17][18] .…”

Combination of Angiotensin (1-7) Agonists and Convalescent Plasma as a New Strategy to Overcome Angiotensin Converting Enzyme 2 (ACE2) Inhibition for the Treatment of COVID-19

“…This elevated expression occurs through activation of the α7 subtype of the nicotine acetylcholine receptor (α7-nAChR) ( 80 ). This is further highlighted in a recent meta-analysis revealing that patients with a history of smoking, as well as active smokers, recorded a significant severity of COVID-19 ( 81 ). In fact, cigarette smoking promotes alterations in the respiratory tract that might increase the risk of viral infections through multiple mechanisms such as impairment of mucociliary clearance, mucus hypersecretion, fibrosis, and dysfunction of the epithelial barrier.…”