Tobacco smoking and the risk of atrial fibrillation: A systematic review and meta-analysis of prospective studies.

Background Epidemiological studies on smoking and atrial fibrillation have been inconsistent, with some studies showing a positive association while others have found no association. It is also unclear whether there is a dose-response relationship between the number of cigarettes smoked or pack-years and the risk of atrial fibrillation. We conducted a systematic review and meta-analysis to clarify the association. Design Systematic review and meta-analysis. Methods We searched the PubMed and Embase databases for studies of smoking and atrial fibrillation up to 20 July 2017. Prospective studies and nested case-control studies within cohort studies reporting adjusted relative risk estimates and 95% confidence intervals (CIs) of atrial fibrillation associated with smoking were included. Summary relative risks (95% CIs) were estimated using a random effects model. Results Twenty nine prospective studies (22 publications) were included. The summary relative risk was 1.32 (95% CI 1.12-1.56, I