An international randomised trial reports a 39% reduction in recurrent atrial fibrillation among patients who drank one caffeinated coffee a day.
A cup of caffeinated coffee each day may lower the risk of an irregular heart rhythm coming back after treatment.
That is the headline finding from the DECAF trial, published in JAMA, which tracked 200 adults with atrial fibrillation or atrial flutter following electrical cardioversion.
Those asked to drink at least one caffeinated coffee daily had fewer recurrences over six months than those told to avoid coffee and all caffeine.
What the study found
Researchers in the United States, Australia and Canada randomly assigned 100 patients to drink coffee and 100 to avoid it for six months.
Recurrent atrial fibrillation or flutter occurred in 47 percent of the coffee group and 64 percent of the abstinence group. That equates to a 39 percent lower hazard of recurrence for those drinking coffee.
There was no significant difference in adverse events between groups.
Why this matters
People with diabetes face a higher risk of atrial fibrillation and of complications when the two conditions occur together.
For years, patients with rhythm problems have been told to steer clear of caffeine.
The new results challenge that habit and add to a growing body of evidence that coffee is not necessarily a trigger for abnormal rhythms.
Atrial fibrillation is common and becoming more so, with a lifetime risk in the region of one in three people. Any safe, everyday habit that reduces recurrence is likely to interest patients and clinicians alike.
How the trial worked
DECAF was an open label, international study of current or recent coffee drinkers undergoing planned cardioversion.
Participants in the coffee group were encouraged to consume at least one cup of caffeinated coffee or a shot of espresso daily.
Those in the abstinence group were asked to avoid both caffeinated and decaffeinated coffee and other caffeine sources. Follow up lasted six months with checks that included electrocardiograms and wearable devices.
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Possible reasons for the benefit
The authors and affiliated universities suggest several mechanisms.
Coffee contains bioactive compounds with anti inflammatory properties. Caffeine can increase physical activity and has mild diuretic effects that may influence blood pressure.
Together these may support a steadier heart rhythm.
These hypotheses need testing but provide plausible explanations for the observed effect.
Important caveats
This was a relatively small study of people with established rhythm problems just after cardioversion.
The design was open label and coffee intake was self reported. The findings do not mean unlimited caffeine is advisable for everyone.
The benefit was seen with roughly one cup daily and within a monitored clinical context. Larger trials will be needed to confirm the effect and to define who benefits most.
What it could mean for people with diabetes
The DECAF results suggest routine coffee intake is unlikely to be harmful for rhythm control and could be helpful for some.
Anyone who is sensitive to caffeine or who has poorly controlled blood pressure should speak to their clinician before changing habits.
If you do drink coffee, be mindful of sugars and syrups that can raise glucose levels.
