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)

<jats:p>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

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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 (&lt;1% probability of RR ≥1.1). Former compared with never smokers were at increased risk of hospitalisation (RR = 1.27, CrI = 1.15-1.40, τ = 0.20), greater disease severity (RR = 1.69, CrI = 1.30-2.22, τ = 0.43) and mortality (RR = 1.59, CrI = 1.34-1.89, τ = 0.37). Current compared with never smokers were at increased risk of greater disease severity (RR 1.3, 95% CrI = 1.01-1.71, τ = 0.32). Data for current smokers on hospitalisation and mortality were inconclusive (RR = 1.10, 95% CrI = 0.97-1.24, τ = 0.23; RR = 1.13, 95% CrI = 0.90-1.40, τ = 0.41, respectively) but favoured there being no important associations (50% and 60% probability of RR ≥1.1, respectively).

CONCLUSIONS: Compared with never smokers, current smokers appear to be at reduced risk of SARS-CoV-2 infection and increased risk of greater in-hospital disease severity, while former smokers appear to be at increased risk of hospitalisation, greater in-hospital disease severity and mortality from COVID-19. However, it is uncertain whether these associations are causal. This version (v12) will be the last regular update; however, yearly updates may continue as new evidence becomes available.

v7 of this living review article has been published in _Addiction_ [https://doi.org/10.1111/add.15276] </jats:p>