Doctors have generally advised some people (for example, people who have abnormally fast heart rhythms or palpitations) to avoid coffee and other caffeine-containing beverages; they do so because caffeine is a stimulant and therefore is theoretically able to cause abnormally fast heart rhythms. A recently published study on the association between self-reported coffee consumption and cases of rapid heart rhythms (cardiac tachyarrhythmias) found that contrary to the expectations of conventional medical wisdom, people who regularly drank coffee had slightly fewer instances of rapid heart rate than those who did not (1).
The study was thorough. Study participants were monitored over an average period of 4.5 years, and researchers controlled for many of the factors that increase risk for rapid heart rate. The study found that people who regularly drink coffee were not more likely to have abnormal heart rhythms, including atrial fibrillation and/or atrial flutter and supraventricular tachycardia. Of course, this type of study cannot prove that coffee consumption protects people from abnormal heart rhythms. Researchers were not able to control for variables such as people incorrectly reporting their coffee intake, people changing the amount of coffee they drink over time, the effects of other substances in coffee, or even whether it was the tachyarrhythmias themselves that lead people drink less coffee. On the other hand, a randomized clinical trial of habitual coffee consumption is unlikely to ever be done, so studies like this one are the best that doctors have to guide recommendations.
Other studies have also failed to show that coffee predisposes people to tachyarrhythmias. In addition, this study adds to an additional type of evidence only recently studied. The researchers also tried to determine whether genetic factors that influence how the body processes caffeine influenced whether coffee intake increased the rate of heart rhythm abnormalities. The researchers found no relation between these genetic factors and rhythm abnormalities.
Although this study did find that people who regularly drink coffee are slightly less likely to have rhythm abnormalities, the study does not demonstrate that coffee consumption protects people from these rhythm problems. People who do not drink coffee or other caffeinated beverages should not start drinking them in an effort to prevent heart rhythm problems. People should not increase coffee consumption to try to prevent rhythm problems either.
The probability that habitual coffee intake increases probability of abnormal heart rhythms in the overall population is small. Accordingly, it seems unnecessary for people to avoid drinking coffee because of this concern. Findings were similar among people who already have heart rhythm problems; however, the conclusions are less certain in these people, but only because there is not as much accumulated evidence in this smaller group. Nevertheless, doctors may be able to move away from the current recommendation that all people who have heart rhythm problems avoid coffee or caffeine intake and instead advise caffeine avoidance for people in whom a relation between intake and symptoms is established. People who have concerns about their caffeine intake, especially those who have heart rhythm problems, should talk with their doctors before increasing their caffeine intake.