Why Coffee Causes Some Healthy People’s Hearts to Skip Beats

Why Coffee Causes Some Healthy People’s Hearts to Skip Beats


This is a review of a study out of the University of California, San Francisco that looked into the negative effects of coffee consumption on Heart Health and Sleep.

Heart Skips Beats

This study reports that your daily cup or cups of coffee may be a quick pick-me-up, but this pick-me-up comes with a mixed bag of good and not-so-good effects on your health.  The researchers say that drinking coffee helps people stay more active, but it also significantly robs some people of sleep.

Whilst coffee consumption doesn't seem to cause irregular rhythms in the upper chamber of the heart, it can cause the lower chambers to skip beats, according to findings presented at the online annual meeting of the American Heart Association.


Lead author Dr. Gregory Marcus, associate Chief of Cardiology for research at the University of California, San Francisco said, "People should understand that this extremely commonly consumed beverage really does have substantive effects on our health, and they're variable.

It's not that coffee is necessarily all good or all bad. It's very likely that whether it's net good or net bad depends on a combination of factors."


Dr. Sana Al-Khatib, a heart rhythm expert with the Duke Electrophysiology Clinic in North Carolina, who wasn't involved with the study added, "A very common question we get almost every week from patients is: Can I drink coffee? Especially in patients with atrial fibrillation," 

She said on the subject that from previous studies, “Results were all over the place" and "It hasn't been easy for us as clinicians to advise patients."

The Trial

For this clinical trial, Dr. Marcus and his team recruited 100 coffee drinkers and fitted them with several devices to continuously record their health; they were a Fitbit, a heart monitor, and a blood glucose tracker.

Over the two weeks, participants were randomly assigned, on a daily basis, to either drink as much coffee as they liked or to abstain.

The researchers then tracked the changes for each person, and between people, that occurred when they were either exposed to coffee or went without.

The Findings

The study found no evidence that coffee consumption created any irregular rhythms within the atria, the upper chambers of the heart. That's good news, since one of the major medical concerns about coffee has been whether it might promote atrial fibrillation, a potentially dangerous condition.

But they did find that coffee consumption could cause the ventricles, those are the lower chambers of the heart, to skip beats.


Dr. Marcus said, "On days randomly assigned to coffee, people exhibited about 50% more Premature Ventricular Contractions [PVCs] - more early beats arising from the lower chambers of the heart. Those who consumed more than a drink of coffee exhibited essentially a doubling of their PVC counts."

Dr. Marcus added, “These PVCs are common and are usually regarded as harmless. We all have them once in a while, and generally they're considered benign.

But we and others have shown that more PVCs are an independent risk factor for heart failure over time. 

Not everyone with more PVCs has heart failure, but it is a factor."

Other Factors 

Coffee also had dramatic effects on two other major health factors, those being physical activity and sleep. Dr. Marcus said, “On days they were randomly assigned to drink coffee, participants on average took about 1,000 more steps than they normally would.

For every additional cup of coffee drink consumed, there was an additional 500 steps."


On the other hand, coffee tended to rob people of sleep. Dr. Marcus stated, "On days randomly assigned to coffee, people slept on average about a half-hour less that evening.  

For every additional cup of coffee, there was about 18 minutes less sleep."


But people who were genetically inclined to metabolize coffee more quickly did not exhibit any significant relationship between their coffee consumption and sleep deprivation.


Dr. Sana Al-Khatib noted that, the study was well done, but she sees a need for follow-up research involving more patients over a longer time to see if coffee's immediate effects eventually lead to increased risk for heart disease, stroke and other health problems.

The cohort

Participants in this study were relatively young and healthy, with an average age of 38 and an average BMI on the high end of healthy. Dr. Sana commented that this is, "Not typical of the patient population we see in clinical practice, who are older and have one or more health problems.”


Dr. Marcus stated, “So if you're concerned about the effects of coffee on your health, you should probably talk with your doctor. Depending on your personal health issues, it might make sense for you to either drink coffee or abstain from it.”

He also said, "For those that are concerned about atrial fibrillation, these data suggest there's no reason to worry about coffee consumption. On the other hand, if there are concerns about PVCs, it may make sense to avoid or minimize coffee consumption.

If there's a goal to increase or maintain physical activity, then coffee may be helpful. But for those who have difficulty sleeping then the sleep disruption caused by coffee may make it less worth it."

The Way Ahead

Despite her reservations, Dr. Al-Khatib plans to use this study when counseling patients, she said, "I wouldn't think of these results as, oh, OK, great, so what, let's wait for the next study.

I will incorporate those findings in my discussions with patients, of course, after I've read the full paper and assuming there are no surprises."

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