Abstract Various comorbidities represent risk factors for severe coronavirus disease 2019 (COVID‐19). The impact of smoking on COVID‐19 severity has been previously reported in several meta‐analyses limited by small sample sizes and poor methodology. We aimed to rigorously and definitively quantify the effects of smoking on COVID‐19 severity. MEDLINE, Embase, CENTRAL, and Web of Science were searched between 1 December 2019 and 2 June 2020. Studies reporting smoking status of hospitalized patients with different severities of disease and/or at least one clinical endpoint of interest (disease progression, intensive care unit admission, need for mechanical ventilation, and mortality) were included. Data were pooled using a random‐effects model. This study was registered on PROSPERO: CRD42020180920. We analyzed 47 eligible studies reporting on 32 849 hospitalized COVID‐19 patients, with 8417 (25.6%) reporting a smoking history, comprising 1501 current smokers, 5676 former smokers, and 1240 unspecified smokers. Current smokers had an increased risk of severe COVID‐19 (risk ratios [RR]: 1.80; 95% confidence interval [CI]: 1.14‐2.85; P = .012), and severe or critical COVID‐19 (RR: 1.98; CI: 1.16‐3.38; P = .012). Patients with a smoking history had a significantly increased risk of severe COVID‐19 (RR: 1.31; CI: 1.12‐1.54; P = .001), severe or critical COVID‐19 (RR: 1.35; CI: 1.19‐1.53; P < .0001), in‐hospital mortality (RR: 1.26; CI: 1.20‐1.32; P < .0001), disease progression (RR: 2.18; CI: 1.06‐4.49; P = .035), and need for mechanical ventilation (RR: 1.20; CI: 1.01‐1.42; P = .043). Patients with any smoking history are vulnerable to severe COVID‐19 and worse in‐hospital outcomes. In the absence of current targeted therapies, preventative, and supportive strategies to reduce morbidity and mortality in current and former smokers are crucial. Highlights The first high‐quality systematic review and meta‐analysis assessing the impact of smoking on COVID‐19 severity. To date, the largest meta‐analysis among peer‐reviewed literature assessing the impact of smoking on COVID‐19 severity, including 32,849 hospitalised patients with COVID‐19. Patients who were current smokers had an increased risk of severe COVID‐19 and severe or critical COVID‐19. Patients with a smoking history had an increased risk of severe COVID‐19, severe or critical COVID‐19, in‐hospital mortality, disease progression and need for mechanical ventilation.
【저자키워드】 zoonoses, coronavirus, Pathogenesis, Epidemiology, Pandemics, respiratory tract, virus classification, 【초록키워드】 Mortality, intensive care, mechanical ventilation, severity, systematic review, Comorbidity, risk, smoking, risk factor, COVID‐19, outcomes, Disease progression, morbidity and mortality, methodology, smoking status, disease, Admission, Critical, Therapies, Smokers, smoker, Web of Science, Endpoint, 95% confidence interval, increased risk, severe coronavirus disease, Registered, small sample size, hospitalized COVID‐19 patients, Effect, current, significantly increased, analyzed, reported, searched, absence, hospitalized patient, hospitalised patient, reduce, eligible, 【제목키워드】 systematic review, smoking, COVID‐19,