For this study, researchers recruited 200 adults with persistent AFib who were also coffee drinkers. Study participants were randomly selected to either drink at least 1 cup of caffeinated coffee a day or completely abstain from caffeine, for a period of 6 months.

“Caffeinated coffee is the most commonly consumed beverage in the U.S., and the great majority of studies examining its health effects have been observational and not true experimental or interventional randomized trials,” Gregory M. Marcus, MD, MAS, professor of medicine in the Division of Cardiology at the University of California, San Francisco, and lead author of this study, told Medical News Today.

“Such studies are inherently limited by confounding factors that travel with the various reasons why one person may decide to consume coffee versus not. Despite the absence of good evidence to recommend avoiding it, atrial fibrillation patients are often instructed by their treating physicians to stop consuming caffeine,” said Marcus.

At the study’s conclusion, researchers observed that study participants who drank 1 cup of caffeinated coffee each day lowered their risk of AFib recurrence by 39%.

“It is important to emphasize that these were participants randomly assigned to consume at least 1 cup of caffeinated coffee a day,” Marcus said. “This is the first long-term randomized trial of caffeinated coffee in general. A randomized study design is the best method we have to infer actual causal effects.”

“The fact that those who were randomized to the coffee arm experienced a lower risk of atrial fibrillation should certainly reassure our atrial fibrillation patients that consume and enjoy caffeinated coffee and should provide data for health care providers that they should not generally prohibit their atrial fibrillation patients from consuming caffeinated coffee,” he continued.

“This study also opens the door to future studies to determine if caffeinated coffee might actually be a tool to protect against atrial fibrillation,” Marcus pointed out.

Marcus said there are several potential mechanisms that might explain why caffeine, and caffeinated coffee in particular, might reduce the risk for atrial fibrillation:

“First, atrial fibrillation often arises in states of heightened vagal tone, such as during sleep or after a heavy meal, and perhaps caffeine, by ramping up the sympathetic nervous system a bit, protects against that. Although caffeine is often considered something that might increase blood pressure, chronic caffeinated coffee consumption has been shown to be associated with a lower blood pressure, probably via a diuretic effect. A lower blood pressure probably protects against atrial fibrillation.”

“Animal studies have suggested that caffeine prolongs the electrical recovery time, or electrical refractoriness, of the left atrium, an electrophysiologic change that would be expected to suppress atrial fibrillation,” Marcus continued.

“In our CRAVE trial of randomization of a day at a time of caffeinated coffee versus a day at a time avoiding caffeine, we found that caffeinated coffee consumption was associated with, on average, 1,000 more steps per day as measured objectively using Fitbits. More physical activity has been shown to reduce atrial fibrillation recurrences among patients with the disease, and so perhaps those randomized to caffeinated coffee were more physically active,” he told us.

“Finally, coffee has many anti-inflammatory constituents, and inflammation is known to promote atrial fibrillation,” he suggested.

MNT had the opportunity to speak with Nikhil Warrier, MD, a board-certified cardiac electrophysiologist and medical director of electrophysiology at MemorialCare Heart & Vascular Institute at Orange Coast Medical Center in Fountain Valley, CA, about this study.

Warrier, who was not involved in the research, commented that he found the findings reassuring.

“Emerging evidence over the past few years has shown that moderate caffeine intake does not increase the risk of AFib,” Warrier explained. “Our current guidance to patients is that caffeine consumption within normal limits is associated with no added risk of AFib. This new randomized trial supports that approach and continues to help move us away from the blanket advice many patients previously received to avoid coffee intake altogether.”

“AFib is probably the most common heart rhythm disorder that we treat today,” he told us. “It is also heavily impacted by lifestyle. We routinely counsel patients on the importance of weight management, sleep quality, alcohol intake, and regular exercise which all play a significant role in AFib development and recurrence.“

“Understanding how everyday habits affect AFib empowers patients and allows us to pair medical or procedural therapies with meaningful lifestyle modifications to improve long term outcomes,” said Warrier.

MNT also spoke with Renato Apolito, MD, medical director of the Cardiac Catheterization Laboratory and assistant program director of cardiology fellowship at Hackensack Meridian Jersey Shore University Medical Center in New Jersey, about his research.

“Many people enjoy coffee and the effects of the caffeine in it every day,” Apolito, who was not involved in the study, commented.

“Typically, cardiologists have advised patients with AFib to limit or avoid their caffeine intake. As a stimulant, some intuitively deduce that caffeine can increase heart rate and blood pressure so it is thought it could trigger or worsen heart rhythm problems, like AFib. This is all theoretical and I have never subscribed to that as it is a very weak effect in small, daily doses,” he told us.

“The results of this DECAF trial may suggest that cardiologists could change their recommendation in the future, and adults with AFib could continue to enjoy a minimal amount of coffee (a cup) each day,” he added.

While this research is a welcomed first step, Apolito said, there are several factors that need to be scientifically studied.

“For example, the study only enrolled people who already drink coffee and it was the only caffeinated substance reviewed,” he detailed. “The coffee intake was limited to ‘one cup’ a day. It would be interesting to see the results of studies looking at people with AFib who consumed more amounts of coffee, or different, naturally caffeinated beverages and in people who did not drink coffee prior to their AFib diagnosis.”