Not Bad for the Heart, but an Ally? How Coffee Reduced Arrhythmia Risk by 39%

Was "Coffee is bad for the heart" true?

"You should refrain from coffee because of your arrhythmia."
If you've been diagnosed with atrial fibrillation, you might have heard this advice at least once.

Caffeine is often associated with increasing heart rate and causing palpitations, and the "common knowledge" that it should be avoided if you have a heart condition has been somewhat of a standard in medical settings.

However, in November 2025, a new study introduced by the German news site "t-online" reported results that overturn this common belief.t-online

"Those who drank coffee had fewer recurrences of atrial fibrillation."

For patients who have been abstaining from coffee, this might sound unbelievable. What does this study indicate?

What is Atrial Fibrillation? It's more than just "a little flutter."

The focus of this study is the arrhythmia known as "atrial fibrillation."
Atrial fibrillation is a condition where the atria, the upper chambers of the heart, quiver irregularly, disrupting the heart's rhythm. This can lead to poor blood flow and an increased risk of blood clots forming in the heart.t-online

As a result,

• Stroke (when a clot travels to the brain)

• Heart failure (when the heart's pumping ability decreases)

are serious complications known to have increased risk. It is one of the most common arrhythmias worldwide, and the number of patients is on the rise with an aging population.PubMed

One treatment method is "cardioversion." This procedure uses electric shocks to restore the heart's normal rhythm, and many people regain a normal rhythm at least once through this method. However, the issue is **"how likely is it to recur afterward?"**

The DECAF Trial: Dividing 200 People into "Coffee Drinkers" and "Abstainers"

The study in question is the clinical trial "DECAF (Does Eliminating Coffee Avoid Fibrillation?)" published in JAMA.Journal Network

In summary, the study was designed as follows:

• Subjects: 200 adults with atrial fibrillation or atrial flutter, just before cardioversion

• Location: Multiple hospitals in Australia, the USA, and Canada

• Classification:

  • Coffee Continuation Group

    • Drinking at least one cup of caffeinated coffee per day

  • Coffee Abstinence Group

    • Basically avoiding caffeinated beverages, including coffee

• Follow-up period: 6 months

• Outcome assessment: Whether atrial fibrillation or atrial flutter recurred

Patients were monitored using wearable devices and electrocardiograms.EatingWell

Results: Those who drank coffee had fewer recurrences

After 6 months, the research team found surprising results.

• Coffee Continuation Group: 47 out of 100 people experienced recurrence (47%)

• Coffee Abstinence Group: 64 out of 100 people experienced recurrence (64%)

Statistical evaluation of this difference calculated thatthose who drank coffee had about a 39% lower risk of recurrence compared to those who did not.t-onlineJournal Network

Considering that it was previously believed safer for people with atrial fibrillation to avoid coffee, this is indeed a reversal of conclusions.

Dr. Christopher Wong, the lead author of the paper, commented, "Contrary to the general image, patients who drank coffee clearly had an advantage."t-online

Why might coffee protect the heart? Possible mechanisms

Of course, coffee hasn't become a "medicine to cure atrial fibrillation." Nonetheless, the research team has proposed several hypotheses as to why recurrences were fewer.t-onlineScienceAlert

1. Increased activity theory

   • Many people feel more alert and active after drinking coffee.

   • Light exercise is known to reduce cardiovascular risk, and the increase in activity might have had a positive effect.

2. Effects of caffeine and diuretic action on blood pressure

   • Coffee has a mild diuretic effect, helping to expel excess water from the body.

   • As a result, it is suggested that blood pressure and the burden on the heart might be slightly reduced.

3. Anti-inflammatory and antioxidant effects

   • Coffee contains many polyphenols, such as chlorogenic acid, which are reported to suppress inflammation and oxidative stress.

   • Chronic inflammation of the heart is said to be involved in the background of atrial fibrillation, which might have contributed to the suppression of recurrence.

4. Secondary effect of "avoiding sugary drinks"

   • By choosing coffee, people might have naturally avoided sugary soft drinks and energy drinks (although this point was not thoroughly examined in this trial).

All of these are still hypotheses, and none can be definitively stated as the deciding factor. However,the direction that "caffeine is not necessarily bad for the heart" aligns with past observational studies.PubMed

However, it's not a "cure-all"—the limitations of the study

It is important to note thatinterpreting this trial's results as "just drink coffee and prevent atrial fibrillation" is dangerous.

The study has several important limitations.The Guardian

• The sample size is relatively small at 200 people

  • Large-scale drug trials often involve thousands to tens of thousands of participants.

  • With 200 people, the influence of biases, such as more people with good lifestyle habits being in the coffee group, cannot be completely ruled out.

• Open-label trial where participants know which group they are in

  • Some might have felt reassured and more active because they were drinking coffee,

  • while others might have felt increased stress from being deprived of coffee.

• Other factors (diet, exercise, sleep, other caffeine sources) are not fully controlled

  • The influence of other caffeine sources, such as energy drinks or strong tea, cannot be completely excluded.

  • Moreover, factors like weight, blood pressure, and sleep quality are all involved in the recurrence of atrial fibrillation.

• Subjects are patients already receiving treatment and medication

  • "What about people who haven't been diagnosed yet and drink coffee as a preventive measure?" is a separate issue, and this trial does not provide conclusions on that.

For these reasons, experts have commented cautiously, saying, "The results are intriguing, but not enough to immediately rewrite guidelines."The Guardian

What do experts think? "Moderate coffee is 'at least not harmful.'"

Gregory Marcus, a cardiologist at the University of California, introduced by t-online, says
"For patients with atrial fibrillation, enjoying coffee in moderation is not necessarily bad," but ultimately emphasizes that one should **"consult individually with their primary doctor."**t-online

Considering the research so far, the following stance seems realistic:

1. The blanket prohibition of "atrial fibrillation = no coffee" might have been somewhat excessive.

2. At least, there is no clear evidence that 1-2 cups of coffee a day increase the risk of recurrence; in fact, data suggesting a reduction is emerging.

3. However, those who experience palpitations or chest discomfort from coffee, or have other illnesses, should not drastically change their consumption without consulting a doctor.

In other words, it's reasonable to position coffee as "neither an absolute evil nor an absolute good. It should be something you decide how to engage with, in consultation with your body and your doctor."

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