In a large, prospective, population-based community cohort study of 386,258 coffee drinkers, greater amounts of habitual coffee consumption were inversely associated with a lower risk of cardiac arrhythmia; in fact, each additional daily cup of coffee was associated with a 3% reduced risk of developing an arrhythmia; these associations were not significantly modified by genetic variants that affect caffeine metabolism.
“Coffee is the primary source of caffeine for most people, and it has a reputation for causing or exacerbating arrhythmias,” said Professor Gregory Marcus, a researcher in the Division of Cardiology at the University of California, San Francisco.
“But we found no evidence that caffeine consumption leads to a greater risk of arrhythmias.”
“Our population-based study provides reassurance that common prohibitions against caffeine to reduce arrhythmia risk are likely unwarranted.”
In the study, Professor Marcus and his colleagues explored whether habitual coffee intake was associated with a risk of arrhythmia, and whether genetic variants that affect caffeine metabolism could modify that association.
They used data on 386,258 coffee drinkers (average mean age of 56 years) from the UK Biobank project.
In addition to a conventional analysis examining self-reported coffee consumption as a predictor of future arrhythmias, they employed a technique called ‘Mendelian Randomization,’ leveraging genetic data to infer causal relationships.
As those with the genetic variants associated with faster caffeine metabolism drank more coffee, the 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, the 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 metabolize caffeine differently.
The higher amounts of coffee were actually associated with a 3% reduced risk of developing an arrhythmia.
“Only a randomized clinical trial can definitively demonstrate clear effects of coffee or caffeine consumption,” Professor Marcus said.
“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.”
The results were published in the journal JAMA Internal Medicine.
Eun-jeong Kim et al. Coffee Consumption and Incident Tachyarrhythmias: Reported Behavior, Mendelian Randomization, and Their Interactions. JAMA Intern Med, published online July 19, 2021; doi: 10.1001/jamainternmed.2021.3616
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