Association of smoking history with severe and critical outcomes in COVID-19 patients: A systemic review and meta-analysis

Introduction: The highly infectious coronavirus disease 2019 (COVID-19) has now rapidly spread around the world. This meta-analysis was strictly focused on the influence of smoking history on the severe and critical outcomes on people with COVID-19 pneumonia.Methods: A systematic literature search was conducted in eight online databases up to 1 February 2021. All studies meeting our selection criteria were included and evaluated. Stata 14.0 software was used to analyze the data.Results: A total of 109 articles involving 517,020 patients were included in this meta-analysis. A statistically significant association was discovered between smoking history and COVID-19 severity, the pooled OR was 1.55 (95%CI: 1.41-1.71). Smoking was significantly associated with the risk of admission to intensive care unit (ICU) (OR = 1.73, 95%CI: 1.36-2.19), increased mortality (OR = 1.58, 95%CI: 1.38-1.81), and critical diseases composite endpoints (OR = 1.61, 95%CI: 1.35-1.93), whereas there was no relationship with mechanical ventilation. The pooled prevalence of smoking using the random effects model (REM) was 15% (95%CI: 14%-16%). Meta regression analysis showed that age ( P = 0.004), hypertension ( P = 0.007), diabetes ( P = 0.029), chronic obstructive pulmonary disease (COPD) ( P = 0.001) were covariates that affect the association.Conclusions: Smoking was associated with severe or critical outcomes and increased the risk of admission to ICU and mortality in COVID-19 patients, but not associated with mechanical ventilation. This association was more significant for former smokers than in current smokers. Current smokers also had a higher risk of developing severe COVID-19 compared with non-smokers. More detailed data, which are representative of more countries, are needed to confirm these preliminary findings.Introduction: The highly infectious coronavirus disease 2019 (COVID-19) has now rapidly spread around the world. This meta-analysis was strictly focused on the influence of smoking history on the severe and critical outcomes on people with COVID-19 pneumonia.Methods: A systematic literature search was conducted in eight online databases up to 1 February 2021. All studies meeting our selection criteria were included and evaluated. Stata 14.0 software was used to analyze the data. Results: A total of 109 articles involving 517,020 patients were included in this meta-analysis. A statistically significant association was discovered between smoking history and COVID-19 severity, the pooled OR was 1.55 (95%CI: 1.41-1.71). Smoking was significantly associated with the risk of admission to intensive care unit (ICU) (OR = 1.73, 95%CI: 1.36-2.19), increased mortality (OR = 1.58, 95%CI: 1.38-1.81), and critical diseases composite endpoints (OR = 1.61, 95%CI: 1.35-1.93), whereas there was no relationship with mechanical ventilation. The pooled prevalence of smoking using the random effects model (REM) was 15% (95%CI: 14%-16%). Meta regression analysis showed that age ( P = 0.004), hypertension ( P = 0.007), diabetes ( P = 0.029), chronic obstructive pulmonary disease (COPD) ( P = 0.001) were covariates that affect the association.Conclusions: Smoking was associated with severe or critical outcomes and increased the risk of admission to ICU and mortality in COVID-19 patients, but not associated with mechanical ventilation. This association was more significant for former smokers than in current smokers. Current smokers also had a higher risk of developing severe COVID-19 compared with non-smokers. More detailed data, which are representative of more countries, are needed to confirm these preliminary findings.