Not only do former smokers have lower risk of atrial fibrillation (AFib) than current smokers, but patients who quit smoking may reduce their AFib risk while doing so, according to a longitudinal cohort study utilizing UK Biobank data, published Sept. 11 in JACC: Clinical Electrophysiology.

The study followed 146,772 current and former smokers (mean age 57.3 years; 48% women) with no history of AFib for a mean of 12.7 years for any incident AFib, the primary endpoint as ascertained from both inpatient and outpatient records. Of the patients enrolled, 37,377 (25.5%) were current smokers, 105,429 (72.0%) were former smokers and 3,966 (2.7%) reported quitting during the study, according to self-reported lifestyle questionnaires. Current smokers who did not quit were more likely to be younger and non-White, have less education and fewer cardiovascular comorbidities, consume less alcohol, and have a higher median pack-year history.

Results showed that 11,214 (7.6%) participants developed AFib. Furthermore, compared with current smokers, former smokers had a 13% lower risk of AFib (hazard rate [HR], 0.87; 95% CI, 0.83-0.91) and those who quit during the study had an 18% lower risk (HR, 0.82; 95% CI, 0.70-0.95), according to data adjusted through a multivariable Cox regression model for age, sex, race, body mass index, daily alcohol use, pack-years, highest education level, hypertension, congestive heart failure, coronary artery disease, diabetes and chronic kidney disease.

Study authors Justin T. Teraoka, MD, MAS; Gregory M. Marcus, MD, MAS, FACC; et al., note several explanations for the higher risk for AFib among current smokers. "Nicotine," they write, "promotes an arrhythmogenic environment because of excess catecholamine release and proarrhythmic aberrations of cardiac myocyte ion channels. Furthermore, nicotine has been associated with increased atrial fibrosis and remodeling." They also note that smoking tobacco is known to be a risk factor for cardiovascular diseases and that inhalation of vaporized hydrocarbons "cause oxidative stress, free radical production, and overall chronic inflammation."

"The findings provide a compelling new reason to show current smokers that it's not too late to quit and that having smoked in the past doesn't mean you're 'destined' to develop AFib," said Marcus, the study's senior author. "Even for the current and longtime smoker, AFib can still be avoided."

There were several limitations to the study, including the variable number of self-reported questionnaires and the possibility of recall bias in them. There could also have been unmeasured confounding factors, such as participant lifestyle and access to preventative health services.

Clinical Topics: Arrhythmias and Clinical EP, Cardiovascular Care Team, Heart Failure and Cardiomyopathies, Prevention, Atrial Fibrillation/Supraventricular Arrhythmias, Acute Heart Failure, Smoking

Keywords: Smokers, Nicotine, Atrial Fibrillation, Smoking Cessation, Smoking, Cardiovascular Diseases, Tobacco Smoking, Risk Factors, Heart Failure