Only alcohol -- not caffeine, diet or lack of sleep -- might trigger heart rhythm condition

New research from UC San Francisco that tested possible triggers of a common heart condition, including caffeine, sleep deprivation and sleeping on the left side, found that only alcohol use was consistently associated with more episodes of the heart arrhythmia.

The authors conclude that people might be able to reduce their risk of atrial fibrillation (AF) by avoiding certain triggers.

The study is published in JAMA Cardiology and was presented November 14, 2021, at the annual Scientific Sessions of the American Heart Association.

Researchers were surprised to find that although most of the things that participants thought would be related to their AF were not, those in the intervention group still experienced less arrhythmia than the people in a comparison group that was not self-monitoring.

"This suggests that those personalized assessments revealed actionable results," said lead author Gregory Marcus, MD, professor of medicine in the Division of Cardiology at UCSF. "Although caffeine was the most commonly selected trigger for testing, we found no evidence of a near-term relationship between caffeine consumption and atrial fibrillation. In contrast, alcohol consumption most consistently exhibited heightened risks of atrial fibrillation."

Atrial fibrillation contributes to more than 150,000 deaths in the United States each year, reports the federal Centers for Disease Control and Prevention, with the death rate on the rise for more than 20 years.

To learn more about what patients felt was especially important to study about the disease, researchers held a brainstorming session in 2014. Patients said researching individual triggers for AF was their top priority, giving rise to the I-STOP-AFib study, which enabled individuals to test any presumed AF trigger. About 450 people participated, more than half of whom (58 percent) were men, and the overwhelming majority of whom were white (92 percent).

Participants in the randomized clinical trial utilized a mobile electrocardiogram recording device along with a phone app to log potential triggers like drinking alcohol and caffeine, sleeping on the left side or not getting enough sleep, eating a large meal, a cold drink, or sticking to a particular diet, engaging in exercise, or anything else they thought was relevant to their AF. Although participants were most likely to select caffeine as a trigger, there was no association with AF. Recent research from UCSF has similarly failed to demonstrate a relationship between caffeine and arrhythmias -- on the contrary, investigators found it may have a protective effect.

The new study demonstrated that consumption of alcohol was the only trigger that consistently resulted in significantly more self-reported AF episodes.

The individualized testing method, known as n-of-1, did not validate participant-selected triggers for AF. But trial participants did report fewer AF episodes than those in the control group, and the data suggest that behaviors like avoiding alcohol could lessen the chances of having an AF episode.

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No link between moderate coffee consumption and increased risk of cardiac arrhythmia, researchers find

In the largest study of its kind, an investigation by UC San Francisco has found no evidence that moderate coffee consumption leads to a greater risk of cardiac arrhythmia.

In fact, each additional daily cup of coffee consumed among several hundred thousand individuals was associated with a 3 percent lower risk of any arrhythmia occurring, including atrial fibrillation, premature ventricular contractions, or other common heart conditions, the researchers report. The study included a four-year follow up.

The paper is published July 19, 2021, in JAMA Internal Medicine.

"Coffee is the primary source of caffeine for most people, and it has a reputation for causing or exacerbating arrhythmias," said senior and corresponding author Gregory Marcus, MD, professor of medicine in the Division of Cardiology at UCSF.

"But we found no evidence that caffeine consumption leads to a greater risk of arrhythmias," said Marcus, who specializes in the treatment of arrhythmias. "Our population-based study provides reassurance that common prohibitions against caffeine to reduce arrhythmia risk are likely unwarranted."

While some professional societies suggest avoiding caffeinated products to lower the risk for arrhythmia, this connection has not been consistently demonstrated -- indeed, coffee consumption may have anti-inflammatory benefits and is associated with reduced risks of some illnesses including cancer, diabetes, and Parkinson disease.

In the new study, UCSF scientists explored whether habitual coffee intake was associated with a risk of arrhythmia, and whether genetic variants that affect caffeine metabolism could modify that association. Their investigation was conducted via the community-based UK Biobank, a prospective study of participants in England's National Health Services.

Some 386,258 coffee drinkers took part in the coffee research, with an average mean age of 56 years; slightly more than half were female. It was an unprecedented sample size for this type of inquiry.

In addition to a conventional analysis examining self-reported coffee consumption as a predictor of future arrhythmias, the investigators employed a technique called "Mendelian Randomization," leveraging genetic data to infer causal relationships. As those with the genetic variants associated with faster caffeine metabolism drank more coffee, this analysis provided a method to test the caffeine-arrhythmia relationship in a way that did not rely on participant self-report and should have been immune to much of the confounding inherent to most observational studies.

With a mean four-year follow up, data were adjusted for demographic characteristics, health and lifestyle habits.

Ultimately, approximately 4 percent of the sample developed an arrhythmia. No evidence of a heightened risk of arrhythmias was observed among those genetically predisposed to metabolize caffeine differently. The researchers said that higher amounts of coffee were actually associated with a 3 percent reduced risk of developing an arrhythmia.

The authors noted limitations including the self-reporting nature of the study, and that detailed information on the type of coffee -- such as espresso or not -- was unavailable.

"Only a randomized clinical trial can definitively demonstrate clear effects of coffee or caffeine consumption," said Marcus. "But our study found no evidence that consuming caffeinated beverages increased the risk of arrhythmia. Coffee's antioxidant and anti-inflammatory properties may play a role, and some properties of caffeine could be protective against some arrhythmias."

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