In a meta-analysis of all studies, we observed a linear dose-response relationship between alcohol consumption and AF risk, with an overall 8% (6% to 10%) increase in AF risk per 1 drink/day increment in alcohol consumption.
July 16, 2014
Life overflows with choices
And consequences. You can choose to smoke and then not be surprised to die a difficult death from cancer. You can choose to eat more calories than you burn and then buy bigger belts. You can choose to “need” more stuff and then, surely, remain unfulfilled.
The more we learn about atrial fibrillation the more it looks like a consequence of our choices. The notion that AF is (mostly) not a mysterious fluke of nature but a result of simple lifestyle choices represents a big shift in thinking, which, like most things in medicine, will take some time to become mainstream. It’s very early in the process of understanding that AF may be unnecessary.
One of the choices we make in our daily life is whether to drink alcohol. And if we decide to drink, we also decide the dosage. These choices, too, come with consequences. And one of them may be to disrupt the heart’s rhythm.
It has long been known that excessive alcohol intake can lead to the “holiday heart,” a disorder in which AF occurs and then passes. Fast (intuitive) thinking holds that it was just too much alcohol at one time, and, no worries, just don’t do that dose again and all will be well.
New studies, however, tell a different story. In recent years, researchers who study populations have found linear (not u-shaped) relationships of alcohol intake and AF incidence. What this means is that one drink daily increases the risk of AF a little. Two drinks daily increases AF risk a little more. And so on. This is different than the old idea that mild-to-moderate alcohol intake is protective (u-shaped curve).
A new study published this week in the Journal of the American College of Cardiology strengthens the idea that alcohol intake increases the risk of having AF in a dose-dependent way. Although the study was observational, the Swedish researchers provided compelling evidence that alcohol intake is indeed an important lifestyle choice, one that comes with potential consequences for the heart’s electrical system. (Recall that the heart beats 100,000 times daily. And that once AF starts, it sometimes doesn’t just stop so easily.)
In my column over at Trials and Fibrillations on theHeart.org, I summarized this study, and then expanded on four thoughts that came to mind when thinking about alcohol and AF risk. The areas I wrote about included the biology, statistics, ethics and philosophy of alcohol use.
Background Although high alcohol consumption has been associated with increased risk of atrial fibrillation (AF), the role of light to moderate drinking remains unclear.
Objectives The study sought to investigate the association between alcohol consumption and AF risk in a prospective study of Swedish men and women and to conduct a meta-analysis of prospective studies to summarize available evidence.
Methods We followed 79,019 men and women who, at baseline, were free from AF and had completed a questionnaire about alcohol consumption and other risk factors for chronic diseases. Incident AF cases were ascertained by linkage to the Swedish Inpatient Register. For the meta-analysis, studies were identified by searching PubMed through January 10, 2014, and by reviewing references of pertinent publications. Study-specific relative risks (RRs) were combined using a random effects model.
Results Over 859,420 person-years of follow-up (1998 to 2009), 7,245 incident AF cases were identified in our own cohort study. The association between alcohol consumption and AF did not differ by sex (p for interaction = 0.74). Compared with current drinkers of <1 drink/week (12 g alcohol/drink), the multivariable RRs of AF were 1.01 (95% confidence interval [CI]: 0.94 to 1.09) for 1 to 6 drinks/week, 1.07 (95% CI: 0.98 to 1.17) for 7 to 14 drinks/week, 1.14 (95% CI: 1.01 to 1.28) for 15 to 21 drinks/week, and 1.39 (95% CI: 1.22 to 1.58) for >21 drinks/week. Results were similar after excluding binge drinkers. In a meta-analysis of 7 prospective studies, including 12,554 AF cases, the RRs were 1.08 (95% CI: 1.06 to 1.10) for 1 drink/day, 1.17 (95% CI: 1.13 to 1.21) for 2 drinks/day, 1.26 (95% CI: 1.19 to 1.33) for 3 drinks/day, 1.36 (95% CI: 1.27 to 1.46) for 4 drinks/day, and 1.47 (95% CI: 1.34 to 1.61) for 5 drinks/day, compared with nondrinkers.
Conclusions These findings indicate that alcohol consumption, even at moderate intakes, is a risk factor for atrial fibrillation.
Characteristics of Prospective Studies of Alcohol Consumption and Risk of Atrial Fibrillation
Consumption of liquor and wine but not beer was significantly positively associated with AF risk.
In this large prospective study, both moderate (1 to 3 drinks/day) and high (>3 drinks/day) alcohol consumption was associated with increased AF risk, and the associations persisted after excluding binge drinkers. With regard to specific alcoholic beverages, consumption of liquor and wine but not beer was significantly positively associated with AF risk. Our finding for total alcohol consumption was confirmed in a dose-response meta-analysis, including our own study and 6 other prospective studies, showing an overall 8% increased AF risk for each 1 drink/day increase of alcohol consumption. Results from individual studies were consistent, thus providing strong support for a causal association between alcohol consumption and risk of AF.
In our study cohort, we observed an association between binge drinking and increased AF risk. Although the link between binge drinking, as may occur during weekends or holidays, and cardiac arrhythmias has been known for a long time, few large prospective studies have examined the association between binge drinking and AF risk. Results from a study of 30,433 adults (≥55 years of age) with a history of cardiovascular disease or diabetes showed that among moderate drinkers, binge drinkers (>5 drinks/day at 1 time) had a statistically significant increased risk (29%) of AF compared with non-binge drinkers As in our study, the positive association of moderate and high alcohol consumption with AF risk remained after excluding binge drinkers. These findings suggest that not only binge drinkers but also regular drinkers of moderate amounts of alcohol have an increased risk of developing AF.
Result from our meta-analysis is consistent with findings from 2 previous meta-analyses showing an 8% increase in AF risk for each 10 g/day increase of alcohol consumption or per drink (equivalent of 12 g pure alcohol) and day. Those 2 meta-analyses included both prospective and case-control studies. We only included prospective studies, which are less susceptible to systematic bias compared with case-control studies. The current meta-analysis also included twice as many AF cases as the previous dose-response meta-analyses.
There are several speculations by which mechanisms alcohol consumption may increase AF risk. Studies in animals and humans have shown that acute and chronic alcohol ingestion leads to depression of heart function and also may result in cardiac conduction abnormalities and morphologic changes. A study in healthy men showed that acute moderate alcohol consumption was associated with an increased interatrial electromechanical delay. Long-term heavy alcohol consumption could lead to dilated cardiomyopathy with both supraventricular arrhythmias such as AF but also ventricular arrhythmias with an increased risk of sudden cardiac death. The association between alcohol consumption and AF also may be related to a shortening of the right atrial effective refractory periods. Other potential mechanisms include alterations in oxidative stress and vagal activity, electrolyte imbalances, and hypertensiom.
I have been particularly fond of dark beer, and the more bitter the better.
I am not particularly fond of atrial fibrillation.
Although this study does not implicate beer as a risk factor for atrial fibrillation, it is enough of a concern that making a choice between drinking alcohol and risking another episode of atrial fibrillation is clear. Months of heart instability and three shocking experiences — i.e, cardioversion– is enough experience to pass on the beer.