While cigarette smoking is a known risk factor for respiratory diseases and cardiovascular diseases, its role in the development of atrial fibrillation is less certain. However, a new study indicates that it may double the risk of this arrhythmia.
A large study, published in the August edition of HeartRhythm, is the first to show that cigarette smoking doubles the risk of atrial fibrillation.
In the Atherosclerosis Risk in Communities Study (ARIC), participants were asked whether they had ever smoked and if they had, they were asked about the age they started smoking, the number of years they smoked, the amount of cigarettes they smoked, and if they were currently smokers (and if they were not, when they gave up).
Compared with “never smokers”, current smokers had a two-fold increased risk of developing atrial fibrillation while former smokers had a 1.32 increased risk. After excluding participants who had prevalent chronic heart disease or heart failure at baseline from the results and censoring for incident chronic heart disease or heart failure during follow-up, the investigators Chamberlain et al reported that the risk attenuated but still remained. They added that this finding indicated that “chronic heart disease and heart failure may account for some of the association of smoking with atrial fibrillation.”
Additionally, the risk of atrial fibrillation was higher in patients who were or had been heavy smokers. Ever smokers (ie, former or current smokers) with the lowest number of cigarette years (≤300) had a similar risk of developing atrial fibrillation as those who had never smoked. The heaviest smokers (>675 cigarette years) had a hazard ratio of 2.10 compared with never smokers (1.94 after adjusting for prevalent chronic heart disease and heart failure at baseline).
Overall, the risk of atrial fibrillation was slightly decreased in former smokers (but not significantly) compared with current smokers. However, former smokers had lower incidence rates and hazard ratios for atrial fibrillation compared with current smokers with similar cigarette years. For example, compared with never smokers, former heavy smokers (≥800 cigarette years) had a 89% increased risk of developing atrial fibrillation while current heavy smokers had a 131% increased risk.
Prior to this study, the link between smoking and atrial fibrillation was not clear. While some studies did find an association between smoking and atrial fibrillation – such as the Rotterdam study, which reported a 51% and 49% increased risk for current and former smokers respectively – others (eg, the Danish Diet, Cancer, and Healthy study) did not find any association. Lead author of the ARIC study Alanna Chamberlain, from the Department of Health Sciences Research Mayo Clinic, said about the new study: “It is my hope that our study findings will shed more light on the impact that smoking has on cardiovascular diseases, and help individuals realise that they can play a role in preventing the development of atrial fibrillation.”