Systematic Reviews
Copyright ©The Author(s) 2016. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Meta-Anal. Apr 26, 2016; 4(2): 10-43
Published online Apr 26, 2016. doi: 10.13105/wjma.v4.i2.10
Environmental tobacco smoke exposure and lung cancer: A systematic review
Peter N Lee, John S Fry, Barbara A Forey, Jan S Hamling, Alison J Thornton
Peter N Lee, John S Fry, Barbara A Forey, Jan S Hamling, P.N. Lee Statistics and Computing Ltd., Sutton, Surrey SM2 5DA, United Kingdom
Alison J Thornton, Independent Consultant in Statistics, Okehampton EX20 1SG, United Kingdom
Author contributions: Lee PN, Fry JS and Forey BA planned the study; Hamling JS and Thornton AJ carried out the literature searches, assisted by Lee PN and Forey BA; Fry JS, Forey BA, Hamling JS and Thornton AJ carried out the data entry which was independently checked by one of these or Lee PN; Lee PN and Forey BA discussed any difficulties in interpreting published data or in the appropriate methods for derivation of RRs; Forey BA and Hamling JS conducted the main statistical analyses, and Fry JS the bias analyses along lines discussed and agreed with Lee PN; Lee PN drafted the paper, with the assistance of Thornton AJ, which was critically reviewed by the other authors.
Conflict-of-interest statement: Lee PN, Director of P.N. Lee Statistics and Computing Ltd., is an independent consultant in statistics and an advisor in the fields of epidemiology and toxicology to a number of tobacco, pharmaceutical and chemical companies including the sponsors of this study. Fry JS, Forey BA and Hamling JS are employees of, and Thornton AJ a consultant to, P.N. Lee Statistics and Computing Ltd.
Data sharing statement: Supplementary Files provide: (1) further information on the methods; (2) fuller description and results of the confounder/misclassification analyses; (3) description of reasons for rejection of some papers; and (4) fuller results of the main meta-analyses. Copies of the database files are available on request from the corresponding author at
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (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:
Correspondence to: Peter N Lee, MA, Director, P.N. Lee Statistics and Computing Ltd., 17 Cedar Road, Sutton, Surrey SM2 5DA, United Kingdom.
Telephone: +44-20-86428265 Fax: +44-20-86422135
Received: November 24, 2015
Peer-review started: November 25, 2015
First decision: December 28, 2015
Revised: January 19, 2016
Accepted: March 9, 2016
Article in press: March 14, 2016
Published online: April 26, 2016
Core Tip

Core tip: We present an up-to-date meta-analysis of the evidence relating non-smoker lung cancer to environmental tobacco smoke (ETS) exposure. We demonstrate a clear risk increase for spousal, at-home, workplace and total exposure, but not childhood exposure. For husband smoking, the relative risk (RR) is estimated as (RR = 1.22, 95%CI: 1.14-1.31). However, adjustment for confounding by education and dietary variables, and correction for misclassified wife’s smoking reduces it to (RR = 1.08, 95%CI: 0.999-1.16). Given the other data limitations and biases we discuss, one cannot reliably conclude that any true ETS effect on lung cancer risk exists. Our results suggest caution in drawing inferences from weak epidemiological associations where known biases exist.