Does coffee actually trigger heart palpitations? A randomised trial tested it
In a two-week trial, 100 adults drank coffee or avoided caffeine on random days. Coffee did not raise the upper-chamber skipped beats it was blamed for — but it nudged up lower-chamber ones and cut sleep.
| Group | Value (value) |
|---|---|
| Coffee days | 58 |
| No-caffeine days | 53 |
Caffeinated coffee does not appear to trigger the fluttering, skipped-beat sensation many people blame it for — at least not the kind that arises in the heart's upper chambers. In a randomised trial that had 100 adults drink coffee or avoid caffeine on assigned days, coffee produced no statistically significant increase in premature atrial contractions, the extra beats most tied to the feeling of palpitations and to atrial fibrillation [s1].
Palpitations are among the commonest reasons people cut out coffee, and clinicians have long told patients with atrial fibrillation to give up caffeine on the assumption that it provokes the arrhythmia. The CRAVE trial put that assumption to a direct test with a design that avoids the usual confounding: a case-crossover in which each person serves as their own control [s1].
How the trial worked
One hundred adults were fitted with a continuously recording electrocardiogram patch, a wrist accelerometer and a continuous glucose monitor, then sent daily text messages over 14 days randomly instructing them to drink caffeinated coffee or avoid caffeine [s1]. Adherence was checked with date-stamped receipts and geofencing of coffee-shop visits [s1]. Because the comparison is within the same person from one day to the next, differences in age, fitness or baseline heart rhythm cannot skew it. The participants were young and healthy on average — mean age 39, and half were women [s1].
What it found
The primary outcome, premature atrial contractions, came out to 58 on coffee days versus 53 on caffeine-free days — a difference that was not statistically significant (rate ratio 1.09; 95% confidence interval 0.98 to 1.20; P = 0.10) [s1]. So the specific ectopic beats linked to palpitations and atrial fibrillation were not meaningfully provoked by coffee.
The lower chambers behaved differently. Premature ventricular contractions rose from 102 a day without caffeine to 154 on coffee days (rate ratio 1.51; 95% confidence interval 1.18 to 1.94) — a real increase [s1]. In people with structurally normal hearts these beats are usually benign, but at very high burdens they can matter, so this is the more substantive cardiac signal in the study. Coffee also came with a familiar pair of trade-offs: on coffee days participants took more steps — 10,646 versus 9,665, a mean difference of 1,058 steps (95% confidence interval 441 to 1,675) — but slept less, 397 versus 432 minutes a night, a loss of about 36 minutes (95% confidence interval 25 to 47) [s1]. Serum glucose barely moved: 95 versus 96 mg per decilitre (mean difference −0.41; 95% confidence interval −5.42 to 4.60) [s1].
The bigger picture on rhythm
The trial measured acute, next-day effects, not the long-run question of whether coffee drinkers develop atrial fibrillation. On that, the population evidence points the other way. A dose-response meta-analysis pooling six prospective cohorts and 228,465 participants found caffeine weakly associated with a lower risk of atrial fibrillation (relative risk 0.90; 95% confidence interval 0.81 to 1.01), with the risk falling by 6% for every 300 mg per day of habitual caffeine (relative risk 0.94; 95% confidence interval 0.90 to 0.99) [s2]. Its authors concluded it is unlikely that caffeine causes or contributes to the arrhythmia [s2]. That is consistent with a large pooled analysis of coffee and cardiovascular outcomes, which found lower, not higher, rates of irregular heartbeat among heavier drinkers.
What it means for a reader
The evidence does not support blaming coffee for the palpitation people fear, and blanket caffeine bans for atrial fibrillation look poorly founded — though the CRAVE trial is a two-week study in mostly young, healthy adults, and individuals vary [s1]. Someone whose own palpitations reliably follow espresso is not wrong to notice a personal pattern; the finding is that no such effect holds across people on average. This is a different matter from diagnosed arrhythmia, where symptoms warrant medical assessment rather than dietary guesswork, and from the separate question of how much caffeine is too much for sleep and anxiety. For the racing-heart readings that consumer wearables increasingly flag, the Apple Heart Study shows how noisy those signals can be.
Sources
- Acute Effects of Coffee Consumption on Health among Ambulatory Adults — New England Journal of Medicine , March 22, 2023
- Caffeine Intake and Atrial Fibrillation Incidence: Dose Response Meta-analysis of Prospective Cohort Studies — Canadian Journal of Cardiology , January 3, 2014
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