Systematic Reviews
Copyright ©The Author(s) 2020. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Meta-Anal. Apr 28, 2020; 8(2): 119-152
Published online Apr 28, 2020. doi: 10.13105/wjma.v8.i2.119
Systematic review with meta-analysis of the epidemiological evidence relating smoking to type 2 diabetes
Peter N Lee, Katharine J Coombs
Peter N Lee, Katharine J Coombs, Department of Statistics, P.N. Lee Statistics and Computing Ltd., Sutton SM2 5DA, Surrey, United Kingdom
Author contributions: Lee PN conceived the study, designed and assisted in the literature searches and statistical analyses, and wrote the various drafts of the paper; Coombs KJ carried out the literature searches and statistical analyses, checked the drafts of the paper, and agreed the final version.
Supported by Japan Tobacco International, No. PO 4700389462.
Conflict-of-interest statement: The authors have carried out consultancy work for many tobacco organizations.
PRISMA 2009 Checklist statement: The guidelines of the PRISMA 2009 statement have been adopted.
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: http://creativecommons.org/licenses/by-nc/4.0/
Corresponding author: Peter N Lee, MA, Director, Senior Statistician, Director and Consultant Medical Statistician, Department of Statistics, P.N. Lee Statistics and Computing Ltd., 17 Cedar Road, Sutton SM2 5DA, Surrey, United Kingdom. peterLee@pnlee.co.uk
Received: February 5, 2020
Peer-review started: February 5, 2020
First decision: March 21, 2020
Revised: April 8, 2020
Accepted: April 21, 2020
Article in press: April 21, 2020
Published online: April 28, 2020
Processing time: 82 Days and 22.8 Hours
Core Tip

Core tip: Based on data from 145 follow-up studies of individuals free of type 2 diabetes at baseline, we confirm evidence of a modest association of smoking with subsequent onset of the disease. Meta-analysis showed relative risks of 1.33 [95% confidence interval (CI): 1.28-1.38] for current vs never smoking, 1.28 (95%CI: 1.24-1.32) for current vs non-smoking, and 1.13 (95%CI: 1.11-1.16) for former smoking. Risks increased with amount smoked and decreased with time quit. Elevated risks were consistently seen when the data were subdivided by various factors, suggesting that the associations are not a result of uncontrolled confounding.