Moderate, daily coffee consumption had no apparent adverse effect for triggering incident heart arrhythmias, and even linked with a small but statistically significant drop in arrhythmias in an analysis of prospectively collected data from nearly 300,000 U.K. residents.
“In this large, population-based, prospective study, moderate habitual coffee drinking was associated with a lower risk of arrhythmia,” EunJeong Kim, MD, said at the annual scientific sessions of the Heart Rhythm Society, held online because of COVID-19.
Her analysis found that on average each additional daily cup of coffee that people said they drank reduced the incidence of arrhythmic episodes by a statistically significant 3%, compared with those who drank fewer daily cups. The relationship held for people who reported drinking as many as five or six cups of coffee daily.
“The main message of our study is that it does not appear to be deleterious to continue with moderate amounts of habitual coffee intake regarding a risk of overall arrhythmia,” said Dr. Kim, a cardiac electrophysiologist at the University of California, San Francisco.
Evidence builds for coffee’s safety
The finding adds to a substantial existing evidence base documenting the safety of moderate, habitual coffee drinking when it comes to heart rhythms. For example, a recent report from the Physicians Health Study of nearly 19,000 American men showed a statistically significant decrease in the incidence of atrial fibrillation during an average follow-up of 9 years among men who reported drinking one to three cups of coffee daily (J Am Heart Assoc. 2019 Aug 6;8:e011346). In addition, a recent review of several reports found that “mild-to-moderate habitual consumption of caffeinated beverages, particularly a daily intake of 2-3 cups of coffee or tea, appears to be safe across a broad range of cardiovascular conditions, and may even be beneficial with respect to diabetes mellitus, atherosclerosis, heart failure, arrhythmia and total mortality,” but also concluded that “acute consumption of high doses of caffeine, particularly in the form of energy drinks, is best avoided”(Trends Cardiovasc Med. 2019 Aug;29:345-50). Specifically about cardiac arrhythmias, the review said “while caffeine is commonly considered a trigger for arrhythmias by physicians and patients alike there is minimal evidence to support this misconception. Rather caffeine is associated with a mild reduction in the incidence of atrial fibrillation in observational studies.”
“There has been a lot of public interest about a possible association of caffeine and arrhythmias,” but an adverse effect from daily consumption of a moderate amount of coffee “is more legend and anecdote than fact based,” commented Andrew D. Krahn, MD, an electrophysiologist, professor of medicine, and head of cardiology at the University of British Columbia and St. Paul’s Hospital in Vancouver. “Increasingly we’re finding that there really is nothing here” when the proarrhythmic effects of moderate coffee undergo detailed assessment, he said in an interview.
What the study did
The study run by Dr. Kim and her associates used prospectively collected data from 296,227 participants in the UK Biobank during 2006-2016 who had complete data on their coffee intake and for the other covariables used in the analysis. During an average 5.25 years of follow-up, these people had more than 13,000 incident arrhythmic events, including 4,748 episodes of atrial fibrillation or flutter and 798 supraventricular tachycardia events, as well as fewer numbers of ventricular arrhythmias and many episodes of less clinically relevant events like skipped beats.
The multivariate analysis the researchers ran controlled for more than 20 demographic, lifestyle, and clinical variables, including adjustment for tea intake but not for consumption of other caffeine-containing drinks.
The adjusted analysis showed an average, statistically significant 3% incremental drop in both all incident arrhythmias and in incident atrial fibrillation episodes for each additional cup of coffee drunk a day, for up to 6 daily cups.
A strength of this study is that it included a large number of people, Dr. Krahn noted, and “the UK Biobank includes a very diverse, community-based sample” of people, said Dr. Kim. The analysis excluded people with prevalent arrhythmia at baseline, so the study couldn’t address the impact of coffee consumption in this setting. A limitation of the study is that participants in the UK Biobank are all volunteers, which could result in a selection bias, Dr. Krahn said.