Smoking Is Independently Associated With an Increased Risk for COVID-19 Mortality: A Systematic Review and Meta-analysis Based on Adjusted Effect Estimates

Abstract

Introduction Smoking can cause muco-ciliary clearing dysfunction and poor pulmonary immunity, leading to more severe infection. We performed this study to explore the association between smoking and mortality of coronavirus disease 2019 (COVID-19) patients utilizing a quantitative meta-analysis on the basis of adjusted effect estimates. Methods We conducted a systematic search of the online databases including PubMed, Web of Science, Scopus and Embase. Only articles reporting adjusted effect estimates on the association between smoking and the risk of mortality among COVID-19 patients in English were included. Newcastle-Ottawa scale (NOS) was fitted to assess the risk of bias. A random-effects model was applied to calculate the pooled effect with the corresponding 95% confidence interval (CI). Results A total of 73 articles with 863,313 COVID-19 patients were included in this meta-analysis. Our results indicated that smoking was significantly associated with an increased risk for death in patients with COVID-19 (pooled relative risk = 1.19, 95% CI = 1.12-1.27). Sensitivity analysis indicated that our results were stable and robust. Conclusion Smoking was independently associated with an increased risk for mortality in COVID-19 patients.

The effect of laboratory-verified smoking on SARS-CoV-2 infection: results from the Troina sero-epidemiological survey

“…Surprisingly current research on the relationship between smoking and SARS-CoV-2/COVID-19 has yielded conflicting findings [ 19 – 21 ]. For instance, a positive association between smoking and risk of COVID-19-related severe outcomes, hospitalization and death was found in some primary and secondary studies [ 22 – 25 ]. In contrast, other studies have identified lower proportions of active smokers among patients diagnosed with SARS-CoV-2 [ 26 – 29 ], and a significant lower prevalence of smoking among hospitalized COVID-19 patients than that expected on the basis of population smoking prevalence [ 30 , 31 ].…”

“…Additional concerns have been raised about the possible sources of residual confounding. Some studies relied on self-reported smoking habits and most failed to correct for relevant confounders which could result in different risk exposure while others combined current smokers and former smokers into one category, preventing from examining the interaction of SARS-CoV-2 with active smoking and its effect on risk of infection and COVID-19 outcomes [ 11 , 22 , 24 , 34 ]. As a whole, all these limitations reflect problems with poor reporting of the smoking status as well as lack of studies specifically designed to examine the association between smoking and COVID-19.…”

The Unfavorable Clinical Outcome of COVID-19 in Smokers is Mediated by H3K4me3, H3K9me3 and H3K27me3 Histone Marks

“…Despite its negligible effects on the expression of ACE2 and TMPRSS2 in endothelial cells [ 1 ], cigarette smoking is still associated with increased risk of severe COVID-19. On the basis of the results of a 2021 meta-analysis on more than 800,000 COVID-19 patients, smoking predicts a 19% increased risk of death in patients with COVID-19 [ 2 ]. Strangely enough, this increased severity does not manifest in the form of gross pulmonary damage that is typically revealed by imaging techniques [ 3 ].…”

The COVID-19 Pandemic and Smoking Cessation—A Real-Time Data Analysis from the Polish National Quitline

“…Since the beginning of 2020, when the COVID-19 pandemic outbreak took place, studies have delivered new evidence on the harmfulness of smoking—this time in the context of SARS-CoV-2 infection and the course of the COVID-19 disease. More and more research proves that smoking is an important risk factor contributing to increased risk of mortality among COVID-19 patients [ 9 ]. Research has shown that any history of smoking in the individual’s life is combined with a substantially higher vulnerability to severe course of the COVID-19 disease, as well as much worse prognosis in the event of hospital treatment [ 10 ].…”