AHA Late breaking Trial - DECAF

 A cup of coffee a day may cut AF recurrence — the DECAF trial (AHA late-breaking science)

A surprising randomized trial presented as late-breaking science at the American Heart Association’s Scientific Sessions 2025 — and published in JAMA — found that patients with atrial fibrillation (AF) who were instructed to drink at least one cup of caffeinated coffee daily had fewer recurrences of AF or atrial flutter than those asked to abstain from all caffeine. The finding challenges long-standing advice that people with AF should avoid caffeinated beverages. 

What the DECAF trial did

DECAF (Does Eliminating Coffee Avoid Fibrillation?) was a randomized clinical trial that enrolled about 200 adults who had AF (or atrial flutter) and had recently undergone cardioversion. Participants were randomized 1:1 to (a) consume at least one cup of caffeinated coffee per day for six months or (b) completely abstain from coffee and other sources of caffeine for six months. The trial ran across multiple centers in Australia, the United States and Canada and was designed to test whether avoiding caffeine reduced recurrent arrhythmias. 

Main result

At six months, the primary outcome — recurrence of AF or atrial flutter — occurred in 47% of the coffee group versus 64% of the abstinence group. That translates to a roughly 39% lower hazard of recurrence for the coffee arm (hazard ratio ~0.61; 95% CI approximately 0.42–0.89). The per-protocol analysis (which included participants who adhered to their assigned regimen) suggested an even larger benefit. There were no major differences in serious adverse events between groups. 

Why this is unexpected

For decades many clinicians have advised AF patients to avoid caffeine because caffeine is a stimulant and can acutely increase heart rate and sympathetic activity — mechanisms thought potentially pro-arrhythmic. Observational studies have been mixed, and some prior research suggested no harm from habitual coffee consumption. DECAF is notable because it’s a prospective randomized trial directly testing caffeine exposure in patients with known AF, rather than relying on observational data. 

Possible explanations (hypotheses)

Investigators and commentators have suggested several possible reasons coffee might reduce AF recurrence:

Tolerance: Regular coffee consumers may develop tolerance to caffeine’s stimulatory effects, so low-to-moderate habitual intake may not trigger arrhythmias and could even stabilize autonomic tone over time. 

Non-caffeine compounds: Coffee contains polyphenols and other biologically active compounds (for example, chlorogenic acids) with anti-inflammatory and antioxidant effects that might reduce arrhythmia susceptibility. 

Reverse causation avoided: Randomization reduces the biases inherent in observational studies where patients who feel symptomatic avoid caffeine — DECAF’s design helps isolate the effect of the exposure. 

These remain hypotheses; the trial was not designed to prove mechanism.

Limitations and cautions

A balanced interpretation is important:

Sample size and population: DECAF enrolled ~200 patients — a respectable size for a randomized behavioral trial but still modest. Participants were people undergoing cardioversion; results may not generalize to all AF patients (for example, those never cardioverted or with different comorbidities). 

Adherence: Not every participant strictly followed the assigned regimen — about 69% adherence in the abstinence group was reported in some summaries — which can bias intention-to-treat estimates. The per-protocol analysis suggested a stronger effect but is more susceptible to selection bias. 

Dose and form: The intervention was “at least one cup of caffeinated coffee daily.” It did not test high doses of caffeine, energy drinks, or differing coffee preparations — so extrapolation beyond a modest daily cup is speculative. 

Short follow-up: The follow-up was six months. Longer-term effects (benefit or harm) remain unknown. 

Clinical implications — what clinicians and patients might take away

DECAF suggests that routine avoidance of modest caffeinated coffee intake after cardioversion may not be necessary and that a daily cup of coffee could be safe — and possibly beneficial — for many patients with AF. Clinicians should:

Avoid blanket restrictions: Rather than universally advising complete caffeine abstinence, clinicians can individualize recommendations — allowing patients who tolerate coffee well to continue it. 

Watch individual response: Some patients do report caffeine-triggered palpitations; patient-level responses still matter. If coffee triggers symptoms in a given patient, avoidance remains reasonable. 

Consider context: The DECAF findings apply to modest daily coffee intake after cardioversion; they do not prove coffee prevents new-onset AF or permit high-dose caffeine consumption. 

Bottom line

The DECAF trial — a randomized study presented at AHA Scientific Sessions 2025 and reported in JAMA — found that consuming at least one cup of caffeinated coffee daily was associated with a significantly lower rate of AF or atrial flutter recurrence over six months compared with complete caffeine abstinence. The finding challenges entrenched advice to avoid coffee after AF and supports individualized, evidence-based counseling. However, confirmatory trials, longer follow-up, and mechanistic studies are needed before changing guideline recommendations broadly. 

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Key references

1. Caffeinated Coffee Consumption or Abstinence to Reduce Atrial Fibrillation: the DECAF randomized clinical trial. JAMA (DECAF trial publication). 

2. American Heart Association — Scientific Sessions 2025: Late-Breaking Science (DECAF presentation). 

3. AHA Newsroom coverage: “Cup of coffee a day may not be harmful for some adults with AFib — and could lower episodes.” 

4. PubMed / abstract summary of DECAF results. 

5. Nature Medicine coverage summarizing implications and context.