JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY
VOL. 64, NO. 3, 2014
ª 2014 BY THE AMERICAN COLLEGE OF CARDIOLOGY FOUNDATION
ISSN 0735-1097/$36.00
PUBLISHED BY ELSEVIER INC.
http://dx.doi.org/10.1016/j.jacc.2014.04.038
EDITORIAL COMMENT
Alcohol Consumption and Risk of Atrial Fibrillation How Much Is Too Much?* David Conen, MD, MPH,yz Christine M. Albert, MD, MPHzxk
A
trial fibrillation (AF) is the most common
risk associated with each 10 g of alcohol intake.
arrhythmia and a strong predictor of major
However, several studies included in the meta-
cardiovascular complications and death (1,2).
analysis assessed alcohol intake retrospectively, af-
Unfortunately, few interventions have been shown
ter the AF event; and recall bias may have inflated the
to improve hard clinical outcomes in the growing pop-
association between alcohol and AF to some degree.
ulation of patients with confirmed AF (3). Therefore, AF prevention is of major clinical importance.
SEE PAGE 281
Prior studies have shown that elevated blood
In this issue of the Journal, Larsson et al. (14) add to
pressure and high body mass index are the 2 most
this prior literature by analyzing the association be-
important potentially reversible risk factors for AF
tween total amount, type, and pattern of alcohol
development (4–8), each explaining about 20% of
intake and incident AF in the largest prospective
the population attributable risk for AF (5,6). If these
study to date, and then combining these results in a
and several other modifiable risk factors were avoi-
meta-analysis limited to other prospective studies.
ded, approximately 50% to 60% of all AF cases in
Larsson et al. (14) assessed alcohol intake by a food
the population might be eliminated, leaving sub-
frequency questionnaire in 2 large Swedish cohorts,
stantial room for improvement (5,8). In comparison,
comprising 79,000 men and women, in whom 7,245
modifiable risk factors explain 80% to 90% of the
hospitalizations for AF were identified through na-
attributable risk for sudden cardiac death (9) and
tional inpatient registries. Compared with individuals
myocardial infarction (10), respectively.
consuming <1 drink of alcohol per week, those who
Based on multiple epidemiologic studies identi-
consumed 15 to 21 and >21 drinks per week had 14%
fying a relationship between alcohol intake and AF
and 39% elevations in their relative risk of devel-
(11), lowering intake may be an effective AF preven-
oping AF, respectively. Consuming <15 drinks per
tion strategy (12,13). A previous meta-analysis of
week (2 drinks per day) was not robustly associated
observational studies found evidence for a linear
with AF development. These risk estimates are
relationship between increasing amounts of alcohol
similar to those obtained in previous prospective
intake and AF, with an estimated 8% increased AF
studies (12,13), and when combined in meta-analysis, a linear dose-response relationship between alcohol intake and AF was found. Given the large numbers of
* Editorials published in the Journal of the American College of Cardiology
events, the investigators were able to show that even
reflect the views of the authors and do not necessarily represent the
small amounts of alcohol intake were associated with
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-
a small, but significant, increased relative risk of new onset AF. Each drink of alcohol consumed per day
cine, Brigham and Women’s Hospital, Harvard Medical School, Boston,
was associated with an estimated 8% increase in
Massachusetts; xDivision of Preventive Medicine, Department of Medi-
the relative risk of AF in both men and women.
cine, Brigham and Women’s Hospital, Harvard Medical School, Boston,
Although remarkably similar to the results of the
Massachusetts; and kCardiovascular Medicine, Department of Medicine, Brigham and Women’s Hospital, Harvard Medical School, Boston, Mas-
prior meta-analysis involving retrospective data (11),
sachusetts. Both authors have reported that they have no relationships
by focusing on prospective studies only, the dose-
relevant to the contents of this paper to disclose.
response data in the current meta-analysis increases
Conen and Albert
JACC VOL. 64, NO. 3, 2014 JULY 22, 2014:290–2
Alcohol Consumption and AF Risk
our confidence in the potential causality of the link
vagal tone (19) in susceptible individuals (20). Clearly,
between alcohol intake and AF.
more studies are needed to understand the effects of
The current study also adds several other impor-
lower doses of alcohol on cardiac electrophysiology.
tant findings to the literature. First, binge drinking
Second, it remains unclear from the present data
(>5 drinks on a single occasion) reported by 18% of
whether small intakes of alcohol are associated with
the population, was associated with an increased risk
AF risk. Although the test for nonlinearity was not
of new onset AF, independent of the number of
statistically significant in the current meta-analysis,
drinks consumed per week. These results combined
clearly more refined patient level data meta-analyses
with prior results in patients with established car-
that control for other dietary and lifestyle risk factors
diovascular disease (15) argue strongly that the
associated with AF are needed to really define the
pattern of alcohol consumption is an important
shape of the relationship at the lower spectrum of
determinant of AF risk. However, binge drinking did
alcohol intake, given the small relative risks involved.
not entirely explain all excess AF risk associated with
In summary, the present study supports the widely
alcohol intake in the population. Second, the type of
held contention that significantly elevated alcohol
alcoholic beverage may impact AF risk, with the
consumption, particularly binge drinking, is related
highest relative risks observed for liquor followed by
to AF and should be avoided. The study also agrees
wine, and no apparent association for beer con-
with other prospective data suggesting that chronic
sumption. Although at least part of this difference
levels of alcohol intake above 2 drinks per day
could be due to residual confounding by total alcohol
may modestly elevate AF risk in men and women.
consumption and/or a drinking pattern, these results
Although the meta-analysis suggests that lower
raise the possibility that drinking beer may be a safer
amounts of alcohol also may be associated with ele-
alternative to other types of alcoholic beverages,
vations in AF risk, the question of how much is too
particularly hard liquor, with respect to AF risk.
much is not definitely answered by this study. When
At least 2 major questions regarding the relation-
assessing the potential net clinical benefit of alcohol
ship between alcohol and incident AF remain unan-
reduction, elevations in AF risk associated with
swered. First, although binge drinking and chronic
small-to-moderate amounts of alcohol intake need to
levels of moderate-to-high alcohol intake have
be balanced against risk reductions observed in other
proarrhythmic effects and direct toxic effects on the
cardiovascular outcomes at similar levels of intake
myocardium, the mechanisms by which small-to-
(9,16,21). Because the AF risk related to consuming
moderate amounts of alcohol consumption may in-
low-to-moderate amounts of alcohol (i.e., <2 drinks
crease AF risk are unclear. The adverse association
per day) is small, these data in isolation should not
between alcohol consumption and AF clearly differs
discourage individuals from safely consuming and
from the favorable inverse association with myocar-
enjoying such modest amounts of alcohol.
dial infarction (16) and U-shaped association with sudden cardiac death (9) and heart failure (17). These
REPRINT REQUESTS AND CORRESPONDENCE: Dr.
varying associations raise the possibility that alcohol
Christine M. Albert, Center for Arrhythmia Preven-
may have a specific negative impact on atrial electro-
tion, Brigham and Women’s Hospital, 900 Common-
physiology, for example, by shortening the atrial
wealth Avenue East, Boston, Massachusetts 02215.
effective refractory period (18) or through alteration of
E-mail:
[email protected].
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KEY WORDS alcohol, atrial fibrillation, epidemiology, prevention, risk factors