ClinicalAtrial fibrillationSmoking and incidence of atrial fibrillation: Results from the Atherosclerosis Risk in Communities (ARIC) Study
Introduction
Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice; it currently affects more than 2.2 million Americans.1 Risk factors for AF include increasing age, male gender, white race, obesity, hypertension, and diabetes.2 More recently, the metabolic syndrome has also been implicated in the development AF.3 However, other important cardiovascular risk factors, such as elevated cholesterol and cigarette smoking, are less clearly related to AF. Specifically, cigarette smoking has been shown to predict one's individual risk for AF in a risk score developed using the Atherosclerosis Risk in Communities (ARIC) study;4 however, results from other prospective studies investigating the association between smoking and AF have provided inconsistent results.
In the Framingham Heart Study, cigarette smoking conferred a 40% increased odds of developing AF among women, but there was no association among men.5 Furthermore, current smoking was not a significant predictor for AF in the Framingham risk score for AF.6 Compared with never smokers, the Rotterdam study reported a 51% and 49% increased risk of incident AF among current and former smokers, respectively, which did not differ by gender.7 A 37% increased risk of AF among ever smokers was reported in the Manitoba Follow-Up Study.8 Yet, no association was found between smoking and AF in the Danish Diet, Cancer, and Health Study9 or the Multifactor Primary Prevention Study.10
Although cigarette smoking increases oxidative stress,11 inflammation,11 and atrial fibrosis,12 all mechanisms potentially involved in the etiology of AF,13 these limited and inconsistent data suggest further investigation of the association between smoking and AF is warranted. Thus, we assessed in detail the risk of incident AF in relation to smoking status and amount in the ARIC study.
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Study population
The ARIC study is a prospective investigation aiming to identify risk factors for atherosclerosis and cardiovascular disease. ARIC recruited adults aged 45 to 64 years from four U.S. communities: Forsyth County, North Carolina; Jackson, Mississippi; Minneapolis suburbs, Minnesota; and Washington County, Maryland.14 Blacks and whites were recruited from Forsyth County, only blacks from Jackson, and predominantly whites from the other two communities. Between 1987 and 1989, 15,792 participants
Results
After exclusions, 15,329 ARIC participants were available for the smoking status analysis, and 15,078 were available for the cigarette-years and the combined smoking status and amount analyses. Current and former smokers were less well educated, were more likely to be current drinkers, were less physically active, and had more prevalent CHD and HF than did never smokers (Table 1).
Over a mean follow-up of 13.1 years, 876 incident AF events were identified. Of these, 749 were ascertained by
Discussion
In this population-based prospective study with up to 16 years of follow-up, former and current smokers exhibited a 32% and 105% increased risk of developing AF compared to never smokers. The risk of incident AF increased with increasing cigarette-years of smoking and appeared to be somewhat greater among current smokers than former smokers with similar cigarette-years of smoking.
Our results corroborate the findings reported in the Framingham Heart Study,5 the Rotterdam Study,7 and the Manitoba
Conclusion
Current smokers had twice the risk of developing AF over up to 16 years of follow-up compared to never smokers. In addition, the risk of developing AF increased with increasing cigarette-years of smoking, and current smokers appeared to have a greater risk of AF than former smokers with similar cigarette-years of smoking. We found that the associations between smoking and AF do not differ between blacks and whites, even though the incidence rates of AF are lower among blacks compared to whites.
Acknowledgments
We thank the staff and participants of the ARIC study for their important contributions.
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Cited by (0)
The Atherosclerosis Risk in Communities Study is carried out as a collaborative study supported by National Heart, Lung, and Blood Institute (NHLBI) Contracts N01-HC-55015, N01-HC-55016, N01-HC-55018, N01-HC-55019, N01-HC-55020, N01-HC-55021, and N01-HC-55022. Dr. Chamberlain was supported by NHLBI Grant T32-HL-007779. This study was further supported by American Heart Association Grant 09SDG2280087 and NHLBI Grant RC1HL099452.