Copyright ©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Meta-Anal. Aug 28, 2021; 9(4): 353-376
Published online Aug 28, 2021. doi: 10.13105/wjma.v9.i4.353
Systematic review with meta-analysis of the epidemiological evidence in Europe, Israel, America and Australasia on smoking and COVID-19
Peter Nicholas Lee, Janette S Hamling, Katharine Jane Coombs
Peter Nicholas Lee, Katharine Jane Coombs, Department of Statistics, P.N. Lee Statistics and Computing Ltd., Sutton SM2 5DA, United Kingdom
Janette S Hamling, Department of Statistics, RoeLee Statistics Ltd., Sutton SM2 5DA, Surrey, United Kingdom
Author contributions: Lee PN conceived the study, checked the data entry and analysis, and wrote the paper; Coombs KJ carried out the literature searches and assisted in finalizing the paper; Hamling JS checked the literature searches, carried out the data entry and analysis, and assisted in finalizing the paper.
Supported by British-American Tobacco (Investments) Ltd., No. 5700014230; Japan Tobacco International S.A., No. 4700562109; and Philip Morris Products S.A., No 5700131814.
Conflict-of-interest statement: The authors have carried out consultancy work for many tobacco organizations.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2020 statement, and the manuscript was prepared and revised according to the PRISMA 2020 statement.
Open-Access: This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Corresponding author: Peter Nicholas Lee, MA, Director, Senior Statistician, Department of Statistics, P.N. Lee Statistics and Computing Ltd., 17 Cedar Road, Sutton SM2 5DA, United Kingdom.
Received: April 3, 2021
Peer-review started: April 3, 2021
First decision: June 18, 2021
Revised: June 28, 2021
Accepted: August 23, 2021
Article in press: August 23, 2021
Published online: August 28, 2021
Core Tip

Core Tip: Detailed analyses of 74 studies related smoking to being tested for coronavirus disease 2019 (COVID-19), having COVID-19, or suffering death or severe disease due to COVID-19. Various smoking indices were studied, as were the effects of adjusting for other factors. Although many studies provided limited unreliable results, consistent evidence showed that of those tested, smokers were less likely to have COVID-19. Among those positive for or hospitalized with COVID-19, there was a clear association between smoking and COVID-19 death and severity in unadjusted analyses, which disappeared following adjustment for comorbidities and demographics. Any adverse effects in smokers appear to derive from their poorer prior health status.