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, I2 = 84%, n = 11 studies) for current smokers, 1.09 (95% CI 1.00–1.18, I2 = 33%, n = 9) for former smokers and 1.21 (95% CI 1.12–1.31, I2 = 80%, n = 14) for ever smokers compared to never smokers. Comparing current versus non-current smokers the summary relative risk was 1.33 (95% CI 1.14–1.56, I2 = 78%, n = 10). The summary relative risk was 1.14 (95% CI 1.10–1.20, I2 = 0%, n = 3) per 10 cigarettes per day and 1.16 (95% CI 1.09–1.25, I2 = 49%, n = 2) per 10 pack-years and there was no evidence of a non-linear association for cigarettes per day, Pnon-linearity = 0.17. Conclusions The current meta-analysis suggests that smoking is associated with an increased risk of atrial fibrillation in a dose-dependent matter, but the association is weaker among former smokers compared to current smokers.