Meta-Analysis
Copyright ©The Author(s) 2019. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Meta-Anal. Feb 22, 2019; 7(2): 31-50
Published online Feb 22, 2019. doi: 10.13105/wjma.v7.i2.31
Misclassification of smoking habits: An updated review of the literature
Janette S Hamling, Katharine J Coombs, Peter N Lee
Janette S Hamling, RoeLee Statistics Ltd., 17 Cedar Road, United Kingdom
Katharine J Coombs, Peter N Lee, P.N. Lee Statistics and Computing Ltd., Sutton SM2 5DA, United Kingdom
Author contributions: Hamling JS and Lee PN planned the study; Coombs KJ carried out the literature searches, assisted by the other authors; Hamling JS carried out the data entry, assisted by Lee PN; Hamling JS carried out the statistical analyses along lines discussed and agreed with Lee PN; Lee PN drafted the paper which was critically reviewed by the other authors.
Conflict-of-interest statement: All the authors are long-term consultants to various tobacco companies and organizations.
PRISMA 2009 Checklist statement: The authors have read the PRISMA 2009 Checklist, and the manuscript was prepared and revised according to the PRISMA 2009 Checklist.
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: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Peter N Lee, MA, Director, Senior Statistician, P.N. Lee Statistics and Computing Ltd., 17 Cedar Road, Sutton SM2 5DA, United Kingdom. peterlee@pnlee.co.uk
Telephone: +44-20-6428265 Fax: +44-20-8642135
Received: November 29, 2018
Peer-review started: November 29, 2018
First decision: December 15, 2018
Revised: January 21, 2019
Accepted: January 21, 2019
Article in press: January 21, 2019
Published online: February 22, 2019
ARTICLE HIGHLIGHTS
Research background

Misclassification of smoking habits leads to underestimation of true relationships between diseases and active smoking, but overestimation of true relationships with passive smoking.

Research motivation

We estimated overall misclassification rates weighted on sample size and investigated heterogeneity by various study characteristics.

Research objectives
Research methods

We analysed data from studies using cotinine as a marker which involved at least 200 participants and provided information on high cotinine levels in self-reported non-, never-, or ex-smokers. Information on low levels in self-reported smokers was also analysed.

Research results

There was considerable heterogeneity between misclassification rates. Rates of claiming never smoking were very high in Asian women smokers, the individual studies reporting rates of 12.5%, 22.4%, 33.3%, 54.2% and 66.3%. False claims of quitting were relatively high in pregnant women, in diseased individuals who may recently have been advised to quit, and in studies considering cigarette smoking rather than any smoking. False claims of smoking were higher in younger populations.There was no clear evidence that rates varied by the body fluid used for the cotinine analysis, the assay method used, or whether the respondent was aware their statements would be validated by cotinine - though here many studies did not provide relevant information. Misclassification rates were higher in more recently published studies.

Research conclusions

Our demonstration that rates of misclassification of smoking habits are particularly high in some situations underlines the difficulty that epidemiologists have in accurately estimating the increases in risk of various diseases associated with active and passive smoking.

Research perspectives

Misclassification rates are heterogeneous, with false claims of never smoking much higher in Asian women, and false claims of having quit higher in pregnant women. A number of the rates are higher in diseased groups likely to have been advised to quit. Misclassification rates are higher in more recent studies, which exacerbates problems in determining true relationships of passive smoking with disease.