The association of smoking status with SARS-CoV-2 infection, hospitalisation and mortality from COVID-19: A living rapid evidence review (version 6)

<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 Ovid MEDLINE and medRxiv.

Setting: Community or hospital with no restrictions on location.

Participants: Adults who had received a test for SARS-CoV-2 infection or a diagnosis of COVID-19.

Measurements: Outcomes were SARS-CoV-2 infection, hospitalisation, disease severity and mortality stratified by smoking status. Study quality was assessed.

Findings: Version 6 with searches up to 17 July 2020 included 174 studies with 26 included in meta-analyses. Thirty-nine studies reported current, former and never smoking status. Notwithstanding recording uncertainties, compared with adult national prevalence estimates, recorded current smoking rates were generally lower than expected. Current compared with never smokers were at reduced risk of SARS-CoV-2 infection (RR = 0.74, 95% Credible Interval (CrI) = 0.56-0.97, τ = 0.46). Former compared with never smokers were at somewhat increased risk of infection but data were inconclusive (RR = 1.06, 95% CrI = 0.94-1.20, τ = 0.19). Current (RR = 1.05, CrI = 0.82-1.34, τ = 0.29) and former (RR = 1.20, CrI = 1.03-1.44, τ = 0.19) compared with never smokers were both at somewhat increased risk of hospitalisation with COVID-19, but data for current smokers were inconclusive. Current (RR = 1.15, CrI = 0.80-1.66, τ = 0.29) and former (RR = 1.51, CrI = 1.06-2.15, τ = 0.36) compared with never smokers were at increased risk of greater disease severity, but data for current smokers were inconclusive. Current (RR = 1.89, 95% CrI = 0.77-3.41, τ = 0.51) and former (RR = 1.93, 95% CrI = 1.33-2.66, τ = 0.19) compared with never smokers had increased risk of in-hospital death, but data for current smokers were inconclusive.

Conclusions: There is uncertainty about the associations of smoking with COVID-19 outcomes. Recorded smoking prevalence among people with COVID-19 was generally lower than national prevalence. Current smokers were at reduced risk of infection. Former smokers were at increased risk of hospitalisation, disease severity and mortality, while data for current smokers favoured no important associations but were inconclusive.</jats:p>