There is no evidence that moderate coffee consumption can cause cardiac arrhythmia, according to the authors of a prospective, population-based community cohort study, findings of which were published this week in JAMA Internal Medicine.
According to authors Eun-jeong Kim (University of California, San Francisco, USA) et al each additional daily cup of coffee consumed among several hundred thousand individuals was associated with a 3% risk of any arrhythmia occurring, including atrial fibrillation, premature ventricular contractions. The study included a four-year follow up.
“Coffee is the primary source of caffeine for most people, and it has a reputation for causing or exacerbating arrhythmias,” said senior and corresponding author Gregory Marcus, professor of medicine in the Division of Cardiology at University of California, San Francisco.
“But, we found no evidence that caffeine consumption leads to a greater risk of arrhythmias,” said Marcus. “Our population-based study provides reassurance that common prohibitions against caffeine to reduce arrhythmia risk are likely unwarranted.”
In the new study, researchers explored whether habitual coffee intake was associated with a risk of arrhythmia, and whether genetic variants that affect caffeine metabolism could modify that association. Their investigation was conducted via the community-based UK Biobank, a prospective study of participants in England’s National Health Service (NHS)
Some 386,258 coffee drinkers took part in the coffee research, with an average mean age of 56 years; slightly more than half were female.
In addition to a conventional analysis examining self-reported coffee consumption as a predictor of future arrhythmias, the investigators employed a technique called Mendelian Randomisation, leveraging genetic data to infer causal relationships. As those with the genetic variants associated with faster caffeine metabolism drank more coffee, this analysis provided a method to test the caffeine-arrhythmia relationship in a way that did not rely on participant self-report and should have been immune to much of the confounding inherent to most observational studies.
With a mean four-year follow up, data were adjusted for demographic characteristics, health and lifestyle habits.
Ultimately, approximately 4% of the sample developed an arrhythmia. No evidence of a heightened risk of arrhythmias was observed among those genetically predisposed to metabolise caffeine differently. The researchers said that higher amounts of coffee were actually associated with a 3% reduced risk of developing an arrhythmia.
The authors noted limitations including the self-reporting nature of the study, and that detailed information on the type of coffee—such as espresso or not—was unavailable.
“Only a randomised clinical trial can definitively demonstrate clear effects of coffee or caffeine consumption,” said Marcus. “But, our study found no evidence that consuming caffeinated beverages increased the risk of arrhythmia. Coffee’s antioxidant and anti-inflammatory properties may play a role, and some properties of caffeine could be protective against some arrhythmias.”
