By Lisa Rapaport
(Reuters Health) - People who regularly drink higher amounts of coffee have a lower risk of cardiac arrhythmia than counterparts who consume less coffee or drink it less often, a new study suggests.
Researchers examined data on a subset of 386,258 adults aged 40 to 69 years (mean age 56 years) who participated in the UK Biobank study, had no history of arrhythmia at baseline, and completed questionnaires detailing daily coffee intake. After a mean follow-up period of 4.5 years, 16,369 participants developed an arrhythmia, including atrial fibrillation (n=12,811), supraventricular tachycardia (n=1,920), ventricular tachycardia (n=909), premature atrial complexes (n=97), premature ventricular complexes (n=632), and unspecified arrhythmias (n=610).
Biobank participants had median coffee consumption of two cups per day. After adjusting for factors including age, sex, race, education, physical activity, and a wide range of comorbidities, each additional daily cup of coffee was associated with a significantly lower risk of arrhythmia during the study (hazard ratio 0.97).
"Contrary to conventional wisdom, which relies on the simple assumption that caffeine increases adrenalin-like activity and that adrenalin-like activity leads to abnormal heart rhythms, there are actually several reasons that support the biological plausibility of coffee as an anti-arrhythmic, at least in some cases," said senior author Dr. Gregory Marcus, a professor of medicine and cardiac electrophysiologist at the University of California, San Francisco.
Because inflammation can play a role in arrhythmias, particularly atrial fibrillation, the anti-inflammatory effect of coffee may be one explanation for the lower arrhythmia risk seen with higher consumption, Dr. Marcus said by email. In addition, several arrhythmias, including atrial fibrillation, some premature ventricular contractions and premature atrial contractions, can be triggered by enhanced vagal tone, and coffee may help to reduce vagal tone.
Some evidence also suggests that coffee may enhance regular physical activity, which in turn reduces the risk of arrhythmias, Dr. Marcus said.
"Given other potential health benefits of coffee, including quality of life and the importance of simply enjoying a cup of coffee, broad-based prohibitions against coffee to reduce the risk of arrhythmias are likely unwarranted," Dr. Marcus said.
Researchers also looked at genetic markers for caffeine metabolism and didn't find any evidence of a significant association between markers of differing caffeine metabolism and arrhythmia risk.
One limitation of the study is that coffee consumption was self-reported, and the researchers also lacked detailed information on the exact type of coffee participants drank, the study team notes in JAMA Internal Medicine.
It's possible that some people might have abstained from coffee to avoid arrhythmias, but under-ascertainment of previous arrhythmias leading to misclassification of incident cases "would be unlikely" to explain "a graded reduction in arrhythmia risk with more habitual coffee consumption among large numbers of coffee drinkers," the authors write.
"It's important to recognize that this study is not telling us to drink more coffee, or start drinking coffee, to protect against developing arrhythmias," said Dr. Zachary Goldberger, an associate professor in the division of cardiovascular medicine at the School of Medicine and Public Health at the University of Wisconsin-Madison.
However, it should offer more reassurance that moderate coffee consumption is not necessarily harmful, and will not always lead to arrhythmias, Dr. Goldberger, co-author of an invited commentary accompanying the study, said by email.
"This is important, given the widespread notion that coffee is universally proarrhythmic," Dr. Goldberger said.
SOURCE: https://bit.ly/3rjk6rp and https://bit.ly/3Bkal0M JAMA Internal Medicine, online July 19, 2021.