Coffee good – or bad – for the heart

Daily coffee intake is tied to increased physical activity and incidence of premature ventricular contractions (PVCs) but fewer episodes of supraventricular tachycardia (SVT) and less nighttime sleep in the CRAVE* trial.

Atrial arrhythmias were not elevated overall whereas SVTs were reduced by 12 percent per coffee drink vs no coffee at all (p=0.028).

Conventional wisdom holds that caffeine causes arrhythmias and should be avoided once arrhythmia is diagnosed. “However, our data showed that those with – or at risk for – SVTs or atrial fibrillation, should not necessarily avoid drinking coffee,” said lead author Dr Gregory Marcus from the University of California, San Francisco, California, US, at AHA 2021.

Coffee challenge

CRAVE enrolled 100 healthy young volunteers without a history of arrhythmias or cardiovascular disease, who either consume or avoid coffee daily for 2 weeks. “One of the biggest challenges we had to enrolling participants was finding individuals who were willing to forgo coffee daily,” said Marcus. More than half of the participants were female; the average age was 38 years. About 30 percent reported drinking at least one cup of coffee daily at baseline; 21 percent had two to three cups daily.

Activity levels, cardiac ectopy, glucose levels, and sleep were tracked, so was compliance to randomization. DNA analysis was done at the end of the study to assess genetic caffeine metabolism.

There were fewer episodes of SVT (RR 0.84), but more PVCs (HR 1.54; p=0.001). Daily coffee intake did not significantly increase atrial arrhythmias. It had also no effect on glucose levels.

More steps, less sleep

Interestingly, the participants walked 1,000 steps more on days they were on coffee vs days they were not (p=0.0010).

In terms of sleep, participants got 36 fewer minutes of sleep each night on days they had coffee vs days they had not (p< 0.001). The more cups of coffee consumed, the greater the sleep loss.

On DNA analysis, slow caffeine metabolizers were more likely to be affected by sleep deprivation than fast metabolizers (p<0.001). Those with the fastest caffeine metabolism had the highest relative risk of PVCs, with significant trends for both CYP12 and polygenic risk scores.

A complex relationship

“More physical activity – prompted by coffee consumption – has numerous health benefits, including reduced risks of diabetes and several cancers; it is also associated with greater longevity,” Marcus said. “However, reduced sleep is associated with adverse psychiatric, neurologic, and cardiovascular outcomes. More frequent abnormal heartbeats from the upper heart chambers influence the risk of AF whereas more frequent abnormal beats from the lower chambers increase the risk of heart failure. These suggest a complex relationship between coffee and health.”

Press briefing moderator Dr Elaine Hylek from Boston University School of Medicine, Massachusetts, US said she might be biased with her comments, being a coffee drinker herself, but was somewhat reassured of the results on atrial arrhythmias. “It seemed like they were increasing their physical activity … hopefully this could translate to better heart health, weight, and blood pressure.”

Discussant Dr Sana Al-Khatib from the Duke University Medical Center, Durham, North Carolina, US said the study was well-conducted and informative, but the young and healthy patient population in CRAVE does not represent the patients they typically see in practice.

“Hence, future researchers should try to validate these results and look at harder endpoints to follow over time,” she suggested.