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 9)

<jats:p>AIMS: To estimate the association of smoking status with rates of i) infection, ii) hospitalisation, iii) disease severity, 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: Version 9 (searches up to 27 October 2020) included 279 studies with 42 ‘good’ and ‘fair’ quality studies included in unadjusted meta-analyses. Seventy-nine studies (28%) 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 = 0.69, 95% Credible Interval (CrI) = 0.57-0.83, τ = 0.38). Data for former smokers were inconclusive (RR = 1.02, 95% CrI = 0.93-1.12, τ = 0.18) but favoured there being no important association (5% probability of RR ≥1.1). Former compared with never smokers were at somewhat increased risk of hospitalisation (RR = 1.17, CrI = 1.04-1.36, τ = 0.17), greater disease severity (RR = 1.52, CrI = 1.12-2.06, τ = 0.29) and mortality (RR = 1.39, 95% CrI = 1.16-1.69, τ = 0.23). Data for current smokers on hospitalisation, disease severity and mortality were inconclusive (RR = 1.06, CrI = 0.89-1.27, τ = 0.23; RR = 1.26, CrI = 0.86-1.94, τ = 0.34; RR = 1.05, 95% CrI = 0.71-1.49, τ = 0.45, respectively) but favoured there being no important associations with hospitalisation and mortality (32% and 39% probability of RR ≥1.1, respectively) and a small but important association with disease severity (80% probability of RR ≥1.1).

CONCLUSIONS: Compared with never smokers, current smokers appear to be at reduced risk of SARS-CoV-2 infection while former smokers appear to be at increased risk of hospitalisation, greater disease severity and mortality from COVID-19. However, it is uncertain whether these associations are causal.

v7 of this living review article has been published in _Addiction _and is available here https://doi-org.libproxy.ucl.ac.uk/10.1111/add.15276  </jats:p>