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EDITORIAL COMMENT

Alcohol Consumption andRisk of Atrial FibrillationHow Much Is Too Much?*

David Conen, MD, MPH,yz Christine M. Albert, MD, MPHzxk

SEE PAGE 281

A trial fibrillation (AF) is the most commonarrhythmia and a strong predictor of majorcardiovascular complications and death (1,2).

Unfortunately, few interventions have been shownto improve hard clinical outcomes in the growing pop-ulation of patients with confirmed AF (3). Therefore,AF prevention is of major clinical importance.

Prior studies have shown that elevated bloodpressure and high body mass index are the 2 mostimportant potentially reversible risk factors for AFdevelopment (4–8), each explaining about 20% ofthe population attributable risk for AF (5,6). If theseand several other modifiable risk factors were avoi-ded, approximately 50% to 60% of all AF cases inthe population might be eliminated, leaving sub-stantial room for improvement (5,8). In comparison,modifiable risk factors explain 80% to 90% of theattributable risk for sudden cardiac death (9) andmyocardial infarction (10), respectively.

Based on multiple epidemiologic studies identi-fying a relationship between alcohol intake and AF(11), lowering intake may be an effective AF preven-tion strategy (12,13). A previous meta-analysis ofobservational studies found evidence for a linearrelationship between increasing amounts of alcoholintake and AF, with an estimated 8% increased AF

* Editorials published in the Journal of the American College of Cardiology

reflect the views of the authors and do not necessarily represent the

views of JACC or the American College of Cardiology.

From the yDepartment of Medicine, University Hospital, Basel,

Switzerland; zCenter for Arrhythmia Prevention, Department of Medi-

cine, Brigham and Women’s Hospital, Harvard Medical School, Boston,

Massachusetts; xDivision of Preventive Medicine, Department of Medi-

cine, Brigham and Women’s Hospital, Harvard Medical School, Boston,

Massachusetts; and kCardiovascular Medicine, Department of Medicine,

Brigham and Women’s Hospital, Harvard Medical School, Boston, Mas-

sachusetts. Both authors have reported that they have no relationships

relevant to the contents of this paper to disclose.

risk associated with each 10 g of alcohol intake.However, several studies included in the meta-analysis assessed alcohol intake retrospectively, af-ter the AF event; and recall bias may have inflated theassociation between alcohol and AF to some degree.

In this issue of the Journal, Larsson et al. (14) add tothis prior literature by analyzing the association be-tween total amount, type, and pattern of alcoholintake and incident AF in the largest prospectivestudy to date, and then combining these results in ameta-analysis limited to other prospective studies.

Larsson et al. (14) assessed alcohol intake by a foodfrequency questionnaire in 2 large Swedish cohorts,comprising 79,000 men and women, in whom 7,245hospitalizations for AF were identified through na-tional inpatient registries. Compared with individualsconsuming <1 drink of alcohol per week, those whoconsumed 15 to 21 and >21 drinks per week had 14%and 39% elevations in their relative risk of devel-oping AF, respectively. Consuming <15 drinks perweek (2 drinks per day) was not robustly associatedwith AF development. These risk estimates aresimilar to those obtained in previous prospectivestudies (12,13), and when combined in meta-analysis,a linear dose-response relationship between alcoholintake and AF was found. Given the large numbers ofevents, the investigators were able to show that evensmall amounts of alcohol intake were associated witha small, but significant, increased relative risk of newonset AF. Each drink of alcohol consumed per daywas associated with an estimated 8% increase inthe relative risk of AF in both men and women.Although remarkably similar to the results of theprior meta-analysis involving retrospective data (11),by focusing on prospective studies only, the dose-response data in the current meta-analysis increases

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our confidence in the potential causality of the linkbetween alcohol intake and AF.

The current study also adds several other impor-tant findings to the literature. First, binge drinking(>5 drinks on a single occasion) reported by 18% ofthe population, was associated with an increased riskof new onset AF, independent of the number ofdrinks consumed per week. These results combinedwith prior results in patients with established car-diovascular disease (15) argue strongly that thepattern of alcohol consumption is an importantdeterminant of AF risk. However, binge drinking didnot entirely explain all excess AF risk associated withalcohol intake in the population. Second, the type ofalcoholic beverage may impact AF risk, with thehighest relative risks observed for liquor followed bywine, and no apparent association for beer con-sumption. Although at least part of this differencecould be due to residual confounding by total alcoholconsumption and/or a drinking pattern, these resultsraise the possibility that drinking beer may be a saferalternative to other types of alcoholic beverages,particularly hard liquor, with respect to AF risk.

At least 2 major questions regarding the relation-ship between alcohol and incident AF remain unan-swered. First, although binge drinking and chroniclevels of moderate-to-high alcohol intake haveproarrhythmic effects and direct toxic effects on themyocardium, the mechanisms by which small-to-moderate amounts of alcohol consumption may in-crease AF risk are unclear. The adverse associationbetween alcohol consumption and AF clearly differsfrom the favorable inverse association with myocar-dial infarction (16) and U-shaped association withsudden cardiac death (9) and heart failure (17). Thesevarying associations raise the possibility that alcoholmay have a specific negative impact on atrial electro-physiology, for example, by shortening the atrialeffective refractory period (18) or through alteration of

vagal tone (19) in susceptible individuals (20). Clearly,more studies are needed to understand the effects oflower doses of alcohol on cardiac electrophysiology.Second, it remains unclear from the present datawhether small intakes of alcohol are associated withAF risk. Although the test for nonlinearity was notstatistically significant in the current meta-analysis,clearly more refined patient level data meta-analysesthat control for other dietary and lifestyle risk factorsassociated with AF are needed to really define theshape of the relationship at the lower spectrum ofalcohol intake, given the small relative risks involved.

In summary, the present study supports the widelyheld contention that significantly elevated alcoholconsumption, particularly binge drinking, is relatedto AF and should be avoided. The study also agreeswith other prospective data suggesting that chroniclevels of alcohol intake above 2 drinks per daymay modestly elevate AF risk in men and women.Although the meta-analysis suggests that loweramounts of alcohol also may be associated with ele-vations in AF risk, the question of how much is toomuch is not definitely answered by this study. Whenassessing the potential net clinical benefit of alcoholreduction, elevations in AF risk associated withsmall-to-moderate amounts of alcohol intake need tobe balanced against risk reductions observed in othercardiovascular outcomes at similar levels of intake(9,16,21). Because the AF risk related to consuminglow-to-moderate amounts of alcohol (i.e., <2 drinksper day) is small, these data in isolation should notdiscourage individuals from safely consuming andenjoying such modest amounts of alcohol.

REPRINT REQUESTS AND CORRESPONDENCE: Dr.Christine M. Albert, Center for Arrhythmia Preven-tion, Brigham and Women’s Hospital, 900 Common-wealth Avenue East, Boston, Massachusetts 02215.E-mail: calbert@partners.org.

RE F E RENCE S

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2. Go AS, Hylek EM, Phillips KA, et al. Prevalenceof diagnosed atrial fibrillation in adults: nationalimplications for rhythm management and strokeprevention: the AnTicoagulation and Risk Factorsin Atrial Fibrillation (ATRIA) study. JAMA 2001;285:2370–5.

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4. Conen D, Tedrow UB, Koplan BA, et al. Influ-ence of systolic and diastolic blood pressure onthe risk of incident atrial fibrillation in women.Circulation 2009;119:2146–52.

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13. Mukamal KJ, Tolstrup JS, Friberg J, et al.Alcohol consumption and risk of atrial fibrillationin men and women: the Copenhagen City HeartStudy. Circulation 2005;112:1736–42.

14. Larsson SC, Drca N, Wolk A. Alcohol con-sumption and risk of atrial fibrillation: a prospective

study and dose-response meta-analysis. J Am CollCardiol 2014;64:281–9.

15. Liang Y, Mente A, Yusuf S, et al. Alcohol con-sumption and the risk of incident atrial fibrillationamong people with cardiovascular disease. CMAJ2012;184:E857–66.

16. Mukamal KJ, Conigrave KM, Mittleman MA,et al. Roles of drinking pattern and type of alcoholconsumed in coronary heart disease in men. N EnglJ Med 2003;348:109–18.

17. Walsh CR, Larson MG, Evans JC, et al. Alcoholconsumption and risk for congestive heart failurein the Framingham Heart Study. Ann Intern Med2002;136:181–91.

18. Marcus GM, Smith LM, Whiteman D, et al.Alcohol intake is significantly associated with atrial

flutter in patients under 60 years of age and ashorter right atrial effective refractory period.Pacing Clin Electrophysiol 2008;31:266–72.

19. Spaak J, Tomlinson G, McGowan CL, et al.Dose-related effects of red wine and alcohol onheart rate variability. Am J Physiol Heart CircPhysiol 2010;298:H2226–31.

20. Mandyam MC, Vedantham V, Scheinman MM,et al. Alcohol and vagal tone as triggers for parox-ysmal atrial fibrillation. Am J Cardiol 2012;110:364–8.

21. Reynolds K, Lewis B, Nolen JD, et al. Alcoholconsumption and risk of stroke: a meta-analysis.JAMA 2003;289:579–88.

KEY WORDS alcohol, atrial fibrillation,epidemiology, prevention, risk factors