INTRODUCTION COVID-19 has major effects on the clinical, humanistic and economic outcomes among patients, producing severe symptoms and death. Smoking has been reported as one of the factors that increases severity and mortality rate among COVID-19 patients. However, the effect of smoking on such medical outcomes is still controversial. This study conducted a comprehensive systematic review and meta-analysis (SR/MA) on the association between smoking and negative outcomes among COVID-19 patients. METHODS Electronic databases, including PubMed, EMBASE, Cochrane Library, Science Direct, Google Scholar, were systematically searched from the initiation of the database until 12 December 2020. All relevant studies about smoking and COVID-19 were screened using a set of inclusion and exclusion criteria. The Newcastle-Ottawa Scale was used to assess the methodological quality of eligible articles. Random meta-analyses were conducted to estimate odds ratios (ORs) with 95% confidence interval (CIs). Publication bias was assessed using the funnel plot, Begg's test and Egger's test. RESULTS A total of 1248 studies were retrieved and reviewed. A total of 40 studies were finally included for meta-analysis. Both current smoking and former smoking significantly increase the risk of disease severity (OR=1.58; 95% CI: 1.16-2.15, p=0.004; and OR=2.48; 95% CI: 1.64-3.77, p<0.001; respectively) with moderate appearance of heterogeneity. Similarly, current smoking and former smoking also significantly increase the risk of death (OR=1.35; 95% CI: 1.12-1.62, p=0.002; and OR=2.58; 95% CI: 2.15-3.09, p<0.001; respectively) with moderate appearance of heterogeneity. There was no evidence of publication bias, which was tested by the funnel plot, Begg's test and Egger's test. CONCLUSIONS Smoking, even current smoking or former smoking, significantly increases the risk of COVID-19 severity and death. Further causational studies on this association and ascertianing the underlying mechanisms of this relation is warranted.

中文翻译：

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COVID-19 患者吸烟与负面结果的风险：系统评价和荟萃分析。

简介 COVID-19 对患者的临床、人文和经济结果产生重大影响，导致严重症状和死亡。据报道，吸烟是增加 COVID-19 患者严重程度和死亡率的因素之一。然而，吸烟对此类医疗结果的影响仍然存在争议。本研究对吸烟与 COVID-19 患者负面结果之间的关联进行了全面的系统回顾和荟萃分析 (SR/MA)。方法 从数据库建立到 2020 年 12 月 12 日，系统地检索了包括 PubMed、EMBASE、Cochrane Library、Science Direct、Google Scholar 在内的电子数据库。使用一组纳入和排除筛选所有有关吸烟和 COVID-19 的相关研究标准。纽卡斯尔-渥太华量表用于评估合格文章的方法学质量。进行随机荟萃分析以估计比值比 (OR) 和 95% 置信区间 (CI)。使用漏斗图、Begg 检验和 Egger 检验评估发表偏倚。结果 共检索到并回顾了 1248 篇研究。最终纳入 40 项研究进行荟萃分析。当前吸烟和既往吸烟均显着增加疾病严重程度的风险（分别为 OR=1.58；95% CI：1.16-2.15，p=0.004；OR=2.48；95% CI：1.64-3.77，p<0.001）中等程度的异质性表现。同样，当前吸烟和既往吸烟也会显着增加死亡风险（分别为 OR=1.35；95% CI：1.12-1.62，p=0.002；OR=2.58；95% CI：2.15-3.09，p<0.001）具有中等程度的异质性。通过漏斗图、Begg 检验和 Egger 检验进行了测试，没有发现发表偏倚的证据。结论 吸烟，即使是当前吸烟或以前吸烟，都会显着增加 COVID-19 严重程度和死亡的风险。有必要对这种关联进行进一步的因果研究，并确定这种关系的潜在机制。