Lead: A randomized clinical trial published in JAMA in 2025 followed 200 people in the US, Canada and Australia who were scheduled for electrical cardioversion for atrial fibrillation (AF). Participants were current or former coffee drinkers and were assigned either to avoid coffee for six months or to consume at least one cup daily. Over the follow-up period, AF episodes lasting more than 30 seconds occurred in 47% of the coffee-drinking group versus 64% of the abstainers, a finding that runs counter to conventional clinical advice. The result suggests guidance on caffeine for AF patients may warrant reconsideration.
Key Takeaways
- Study design: 200 patients across the US, Canada and Australia awaiting electrical cardioversion were enrolled in a randomized clinical trial and followed for six months.
- Primary outcome: AF recurrence >30 seconds was recorded in 47% of those who drank coffee daily, compared with 64% of those who avoided it.
- Relative effect: The observed difference corresponds to a 39% lower recurrence risk among coffee drinkers over six months.
- Population: All participants were current or former coffee drinkers at enrollment; the trial did not enroll lifelong non–coffee drinkers.
- Publication: The trial and its results were reported in JAMA (Wong et al., 2025).
- Mechanistic hypotheses: Investigators cite possible benefits from improved exercise tolerance, diuretic effects, anti-inflammatory compounds and beverage substitution as potential explanations, none proven within the trial.
- Limitations: The study did not collect detailed diet or exercise data and cannot alone establish causality for all populations with AF.
Background
Atrial fibrillation is the most common sustained cardiac arrhythmia, affecting tens of millions globally and increasing in prevalence with age. AF raises risks for stroke and heart failure and is associated with comorbidities such as obesity, diabetes and heavy alcohol use. Clinicians have long cautioned some AF patients to limit caffeine because caffeine raises heart rate and alertness, and because past observational studies have produced mixed findings. Until now, randomized data on routine caffeinated coffee consumption after cardioversion have been lacking, leaving uncertainty for clinicians advising patients.
Electrical cardioversion is a common procedure to restore normal rhythm in patients with symptomatic AF; however, recurrence is frequent and a target for preventive strategies. Lifestyle guidance—covering alcohol, weight, sleep and stimulants—forms part of comprehensive AF care, yet recommendations about coffee have generally been conservative due to theoretical concerns. The new trial sought to test whether continuing versus avoiding coffee after cardioversion influenced short-term recurrence risk.
Main Event
The trial enrolled 200 adults across three countries who were scheduled for electrical cardioversion and who reported prior coffee use. Participants were randomized to one of two behavioral protocols: abstain from coffee for six months, or consume at least one cup of caffeinated coffee per day for six months. Investigators monitored participants for AF episodes longer than 30 seconds over the follow-up window, using routine clinical monitoring and participant reports as per the study protocol.
At six months, 47% of those randomized to daily coffee reported or were documented to have an AF recurrence, compared with 64% in the abstinence arm. Statistically, the authors reported a 39% lower recurrence risk among people who drank coffee. The study team emphasized that the trial measured recurrence rates after cardioversion rather than new-onset AF in lifelong non–coffee drinkers.
Authors and external commentators highlighted that this is the first randomized clinical trial addressing habitual coffee intake after cardioversion. The protocol did not capture granular dietary intake, exercise levels, or all potential confounders, so the investigators recommended cautious interpretation and further research to test mechanisms and to evaluate other caffeinated products.
Analysis & Implications
If replicated, the finding challenges routine blanket recommendations that all AF patients avoid coffee. For clinicians, the trial suggests a personalized approach may be reasonable: patients who tolerate caffeinated coffee without provoked symptoms could continue moderate intake, while those who notice clear symptom triggers should still be advised to limit caffeine. The trial does not establish that coffee prevents AF; it shows an association in a randomized behaviour-assignment context among prior coffee users undergoing cardioversion.
Mechanistically, several plausible pathways could explain lower recurrence in coffee consumers. Caffeine can enhance exercise capacity, and better fitness is protective against AF; coffee contains anti-inflammatory polyphenols that might lower cardiovascular risk; and mild diuretic effects could reduce blood pressure and volume stress. None of these mechanisms were tested directly in the trial, so they remain hypotheses to guide future mechanistic studies.
Public-health implications hinge on generalizability. The enrolled cohort consisted of people who already drank coffee previously; effects among lifelong non–coffee drinkers are unknown. Clinicians should weigh this evidence alongside each patient’s symptom pattern, comorbidities, and preferences. Regulatory or guideline changes will require replication and additional trials that measure objective activity, diet and physiologic mediators.
Comparison & Data
| Group | AF recurrence (>30 s) | Rate |
|---|---|---|
| Daily coffee (n≈100) | 47 cases | 47% |
| Coffee abstainers (n≈100) | 64 cases | 64% |
| Relative reduction | — | 39% lower risk |
The absolute difference between arms was 17 percentage points (64% minus 47%), corresponding to a 39% relative reduction in recurrence risk for the coffee group over six months. The table presents the trial’s primary outcome as reported; the study’s statistical adjustments and confidence intervals are available in the JAMA article for readers seeking detailed effect estimates.
Reactions & Quotes
Cardiology investigators and commentators responded to the trial by noting both its potential to change counseling and its need for replication. Their comments emphasize cautious optimism rather than definitive practice shifts.
Investigators summarized that, contrary to prior assumptions, participants assigned to daily coffee experienced fewer recurrences after cardioversion.
Christopher Wong, University of Adelaide (study author)
This paraphrased comment contextualizes the primary finding without overstating causation: the trial randomized behavior among prior coffee users and observed fewer recurrences in the coffee arm.
External experts suggested clinicians may permit patients who tolerate caffeinated beverages to continue them while monitoring symptoms.
Gregory Marcus, University of California, San Francisco (cardiologist/electrophysiologist)
Marcus and others urged personalization: some patients still report caffeine-triggered palpitations, and individual responses can vary.
Unconfirmed
- Whether improved exercise performance mediated the lower recurrence in coffee drinkers is unconfirmed; the trial did not collect detailed exercise data.
- It is unconfirmed if the same effect would appear in lifelong non–coffee drinkers or in different doses/forms of caffeine such as energy drinks or caffeine pouches.
- Direct causality between coffee’s anti-inflammatory or diuretic properties and reduced AF recurrence remains hypothetical and unproven by this trial.
Bottom Line
This randomized trial of 200 people post-cardioversion found fewer AF recurrences among those assigned to drink at least one cup of coffee per day compared with those who abstained for six months. The absolute difference was 17 percentage points, equating to a 39% relative reduction in recurrence risk for the coffee group in this cohort of prior coffee users.
Clinicians should interpret the findings as important but preliminary: the study supports a more individualized conversation about caffeine for AF patients, encourages further research on mechanisms and generalizability, and does not imply that caffeine is safe or protective for every person with AF. Patients who notice caffeine triggers should continue to avoid it, while others may reasonably discuss a monitored trial of moderate coffee intake with their clinician.
Sources
- ScienceAlert — media report summarizing the trial and reactions (news/press).
- JAMA (Wong et al., 2025) — peer-reviewed journal report of the randomized clinical trial (academic journal).