The association of smoking status with SARS-CoV-2 infection, hospitalisation and mortality from COVID-19: A living rapid evidence review with Bayesian meta-analyses (version 12)

Aims: To estimate the association of smoking status with rates of i) infection, ii) hospitalisation, iii) disease severity in hospitalised patients, and iv) mortality from SARS-CoV-2/COVID-19 disease. Design: Living rapid review of observational and experimental studies with random-effects hierarchical Bayesian meta-analyses. Published articles and pre-prints were identified via MEDLINE and medRxiv. Setting: Community or hospital. No restrictions on location. Participants: Adults who received a SARS-CoV-2 test or a COVID-19 diagnosis. Measurements: Outcomes were SARS-CoV-2 infection, hospitalisation, disease severity and mortality stratified by smoking status. Study quality was assessed (i.e. ‘good,’ ‘fair’ and ‘poor’). Findings: v12 (searches up to 2021-07-18) included 547 studies with 87 ‘good’ and ‘fair’ quality studies included in unadjusted meta-analyses. 171 studies (31.3%) reported current, former and never smoking status with the remainder using broader categories. Recorded smoking prevalence among people with COVID-19 was generally lower than national prevalence. Current compared with never smokers were at reduced risk of SARS-CoV-2 infection (RR = 0.67, 95% Credible Interval (CrI) = 0.60-0.75, τ = 0.27). Data for former smokers were inconclusive (RR = 0.99, 95% CrI = 0.94-1.05, τ = 0.12) but favoured there being no important association (