A New Study Just Found an ‘Astounding’ Link Between Coffee and Heart Rhythms
Coffee has spent years in a strange health limbo. One week, it’s a morning staple with a halo, the next it’s the troublemaker blamed for racing pulses and shaky nerves. People living with irregular heartbeat are usually warned about caffeine without much hesitation. Now, it appears that researchers have uncovered something unexpected about its relationship with heart rhythms.
The First Trial Of Its Kind
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For decades, conversations about atrial fibrillation, or AFib, usually included a nudge to cut back on caffeine. AFib involves an irregular heartbeat that can interrupt blood flow, raise stroke risk, and leave millions managing symptoms long-term.
More than 10 million adults in the United States live with it, and many have heard some version of the same advice: skip the coffee.
A team based at the University of Adelaide and the University of California, San Francisco, decided to challenge that assumption in a more controlled way. Their study, named the DECAF trial, enrolled 200 adults across Australia, the United States, and Canada who already had persistent AFib.
Half drank at least one cup of caffeinated coffee or an espresso shot each day for six months. The other half avoided coffee and all caffeine entirely.
Participants wore monitors, and every potential episode was confirmed by clinicians using electrocardiograms. The tracking created a rare, direct look at cause and effect.
The Result That Shocked The Researchers
By the end of the study, the coffee group saw something that surprised the clinical team. Their risk of a recurrent AFib episode dropped by 39 percent compared to the group that stayed caffeine-free. The figure pushed against years of assumptions.
It also aligned with hints researchers had noticed in earlier observational studies, although those older studies couldn’t establish cause and correlation. This trial could, and it told a different story.
The researchers pointed to several possible reasons. Caffeinated coffee often increases physical activity in small, measurable ways. In a previous experiment that tracked days with coffee versus caffeine-free days, the coffee days resulted in approximately 1,000 extra steps. More movement has been tied to lower AFib recurrence.
Caffeine also acts as a mild diuretic. Over time, that can reduce blood pressure, which helps ease strain on the atria. Animal studies have suggested that caffeine may affect electrical recovery in the heart’s upper chambers, potentially helping to stabilize the rhythm.
Additionally, coffee contains anti-inflammatory compounds, and inflammation is known to play a role in AFib development. None of these explanations stands alone, but together they form a network of small advantages that may help explain the unexpected drop in episodes.
A Shift In Guidance
The trial’s outcome is already sparking careful updates on how clinicians discuss caffeine. Cardiologists who were not involved in the study called the results reassuring, especially for AFib patients who enjoy coffee and have been unsure about that daily cup.
Several experts have pointed out that moderate caffeine intake has not been shown to cause clear harm in recent years, and this trial adds strength to that trend. They also highlighted lifestyle factors that consistently influence AFib, including weight, sleep patterns, blood pressure, and physical activity.
Coffee does not replace those efforts, but it is no longer on the automatic “avoid” list that many patients were given in the past.
Still, some questions remain. The study included only people who already drank coffee. It tested one cup per day, not three or four. It did not test energy drinks or highly caffeinated teas. Future studies will need to map those differences.
A Familiar Drink With A New Role
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The gist isn’t that coffee cures AFib. It’s that a long-standing assumption didn’t hold up under stronger testing. For many people living with the condition, that alone is a relief. Routine habits often carry emotional weight, and coffee is one of the most common daily rituals in the United States and Australia, with approximately two-thirds of American adults and three-quarters of Australians drinking it daily.
The DECAF trial suggests that coffee doesn’t have to be a guilty pleasure for people managing irregular heart rhythms. In fact, it may work in their favor.