COVID-19 and smoking: A systematic review of the evidence

Overview of the five studies included in the systematic review Title Setting Population Study design and time horizon Outcomes Smoking rates by outcome Zhou et al.9 (2020)Clinical course and risk factors for mortality of adult inpatients with COVID-19 in Wuhan, China: a retrospective cohort study Jinyintan Hospital and Wuhan Pulmonary Hospital, Wuhan, China All adult inpatients (aged ≥18 years) with laboratory confirmed COVID-19 (191 patients) Retrospective multicenter cohort study until 31 January 2020 Mortality54 patients died during hospitalisation and 137 were discharged Current smokers: n=11 (6%)Non-survivors: n=5 (9%)Survivors: n=6 (4%)(p=0.20)Current smoker vs non-smokerUnivariate logistic regression(OR=2.23; 95% CI: 0.65–7.63; p=0.2) Zhang et al.10(2020)Clinical characteristics of 140 patients infected with SARS-CoV-2 in Wuhan, China No. 7 Hospital of Wuhan, China All hospitalised patients clinically diagnosed as ‘viral pneumonia’ based on their clinical symptoms with typical changes in chest radiology (140 patients) Retrospective 16 January to 3 February 2020 Disease SeverityNon-severepatients: n=82Severe patients:n=58 Disease SeverityFormer smokers: n=7Severe: n=4 (6.9%)Non-severe: n=3 (3.7%) (p= 0.448)Current smokers: n=2Severe: n=2 (3.4%)Non-severe: n=0 (0%) Guan et al.12(2019)Clinical Characteristics of Coronavirus Disease 2019 in China 552 hospitals in 30 provinces, autonomous regions, and municipalities in mainland China Patients with laboratory-confirmed COVID-19 (1099 patients) Retrospective until 29 January 2020 Severity and admission to an ICU, the use of mechanical ventilation, or deathNon-severe patients: n=926 Severe patients: n=173 By severitySevere cases16.9% current smokers5.2% former smokers77.9% never smokersNon-severe cases11.8% current smokers1.3% former smokers86.9% never smokersBy mechanical ventilation, ICU or deathNeeded mechanical ventilation, ICU or died25.8% current smokers7.6% former smokers66.7% non-smokersNo mechanical ventilation, ICU or death11.8% current smokers1.6% former smokers86.7% never smokers Huang et al.11(2020)Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China A hospital in Wuhan, China Laboratory-confirmed 2019-nCoV patients in Wuhan (41 patients) Prospective from 16 December 2019 to 2 January 2020 MortalityAs of 22 January 2020, 28 (68%) of 41 patients were discharged and 6 (15%) patients died Current smokers: n=3ICU care: n=0Non-ICU care: n=3 (11%)Current smokers in ICU care vs non-ICU care patients (p=0.31) Liu et al.13 (2019)Analysis of factors associated with disease outcomes in hospitalised patients with 2019 novel coronavirus disease Three tertiary hospitals in Wuhan, China Patients tested positive for COVID-19 (78 patients) Retrospective multicentre cohort study from 30 December 2019 to 15 January 2020 Disease progression11 patients (14.1%) in the progression group 67 patients (85.9%) in the improvement/stabilization group 2 deaths Negative progression group: 27.3% smokersIn the improvement group: 3% smokersThe negative progression group had a significantly higher proportion of patients with a history of smoking than the improvement/stabilisation group (27.3% vs 3.0%)Multivariate logistic regression analysis indicated that the history of smoking was a risk factor of disease progression (OR=14.28; 95% CI: 1.58–25.00; p= 0.018)