Drinking caffeinated coffee is safe for people with atrial fibrillation and may help protect against recurrence of the disease, a new study has found.
More than 10 million Americans live with atrial fibrillation or A-fib, a common heart condition that causes rapid heartbeat and can lead to heart failure, blood clots, and stroke. Doctors have long tried to understand whether caffeine, which can increase heart rate and blood pressure, causes attacks that resemble fluttering or pounding in the chest, as well as dizziness or shortness of breath.
“There is no standard advice about atrial fibrillation and caffeine,” said Dr. Gregory Marcus, a cardiologist and professor of medicine at the University of California, San Francisco, who led the study. DECAF Study (Does Quitting Coffee Prevent Atrial fibrillation?). “I often encounter patients who have stopped drinking caffeinated coffee because their doctor told them to because of atrial fibrillation.”
Results from the DECAF study, a four-year clinical trial examining the effects of coffee drinking on people with a history of heart rhythm problems that either resolved or were treated, were presented Sunday at the American Heart Association's annual meeting in New Orleans and published in JAMA. Marcus is an associate editor at JAMA.
The researchers recruited 200 older adults in Australia, Canada and the United States who had been regular coffee drinkers at some point in the past five years. The average age was 70 years, and a third were women.
For six months, participants were randomized into two groups: those who gave up caffeine and those who drank at least one cup of coffee every day. Each self-reported consumption of coffee and caffeinated beverages during telemedicine or video recordings that were conducted one, three, and six months after the start of the study.
Using data from electrocardiograms, or EKGs, taken in a doctor's office, wearable heart monitors, and implantable heart devices, Marcus and his team determined whether people in each group had their first recurrent episode of heart fibrillation and when it happened. They included episodes of atrial flutter, a related condition that also causes abnormal contractions in the upper chambers of the heart.
Both groups had approximately the same drinking habits. Not everyone was a coffee drinker when the study began, but the number of daily coffee drinkers in each group was similar.
Before the study began, 60% of people in the coffee drinking group and 65% in the non-coffee drinking group said that coffee had never caused an episode of atrial fibrillation.
During the six-month study, 111 people, or 56%, experienced a recurrence of atrial flutter. People in the coffee-drinking group were less likely to relapse—47%, compared to 64% for people in the non-coffee-drinking group—and took longer before they had their first episode.
(About a third of people in the non-coffee group admitted to drinking at least a cup of coffee during the study, while the rest drank none.)
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Previous observational studies found that people who drank coffee had a lower risk of developing atrial fibrillation, but the new study shows a cause-and-effect relationship, Marcus said.
“I was somewhat surprised by how effective caffeinated coffee was in protecting against atrial fibrillation,” Marcus said.
Dr. Joanna Contreras, a cardiologist at Mount Sinai Fuster Heart Hospital in New York, said the most important finding from the study was that drinking a cup of coffee a day appears to be completely safe for people with A-fib, not that coffee is protective.
“There's no hard and fast rule. Not everyone has the same reaction to caffeine,” said Contreras, who was not involved in the study.
There are notable limitations to the study, including the influence of caffeinated drinks other than coffee. The study did not track differences in exercise habits or diet. Marcus suggested that people who drink coffee might also exercise more.
The study found that drinking just one cup of coffee a day had a protective effect, and although some study participants drank more, it is unclear whether more than a cup of coffee a day may have any effect on the recurrence of fibrillation A.
Moderation is key, Contreras said.
“If people drink six or seven cups of coffee and then Red Bull and Celsius, that's different,” she said.
It is not clear why drinking coffee was associated with a lower risk of recurrence of irregular heartbeats. It's possible that an anti-inflammatory compound in coffee, rather than caffeine, could reduce the likelihood of relapses in the coffee-drinking group, Marcus said.
If caffeine is involved, it is possible that stimulating the body's adrenaline response with caffeine may help prevent cardiac fibrillation. According to Marcus, people often report episodes when they are relaxed, such as during sleep or after a large meal, when adrenaline levels are low, when the part of the nervous system responsible for resting and digesting food is activated.
In addition, the study only included people who were not currently experiencing episodes of atrial fibrillation. The results may not be applicable to people with unmanageable disorder.
“If someone had cardiac fibrillation, caffeine could definitely increase the heart rate during that episode and therefore lead to a worsening of symptoms,” he said.
For people who already drink coffee regularly, “this shows that you can have a cup of coffee in the morning and be fine if you have atrial fibrillation,” Contreras said.
