In fact, an adjusted analysis found that “each additional cup of coffee intake was associated with a 3% lower risk of incident arrhythmia,” Eun-jeong Kim, MD, of the division of cardiology at the University of California, San Francisco, and colleagues reported in JAMA Internal Medicine.
In addition, genetic differences that affect caffeine metabolism did not significantly influence the odds of arrhythmias, the researchers found.
Still, these findings should not necessarily encourage people to start drinking coffee if they don’t already, or to guzzle additional cups with abandon, they said.
American Heart Association
Dr. Gregory M. Marcus
“We certainly don’t want to say drink coffee and it will reduce your risk of arrhythmias,” study author Gregory M. Marcus, MD, MAS, associate chief of cardiology for research at UCSF Health, said in an interview. “But rather, we think the main point is that a blanket prohibition against coffee or caffeine to reduce the risk of arrhythmias among patients who have a diagnosis of arrhythmias is likely unwarranted. And given some evidence that coffee consumption may actually have other benefits regarding diabetes, mood, and perhaps overall mortality, it may be problematic to admonish patients to avoid coffee or caffeine when it is not really warranted.”
Methods and results
The conventional wisdom that caffeine increases arrhythmic risk has not been well substantiated. To further examine whether moderate, habitual coffee drinking relates to arrhythmia risk, and whether certain genetic variants influence the association, Dr. Kim and colleagues analyzed data from the UK Biobank. They focused on longitudinal data collected between 2006 and 2018 from 386,258 people who did not have a prior diagnosis of arrhythmia.
Participants had an average age of 56 years, and about 52% were female. They provided information about their coffee consumption, and the researchers grouped the participants into eight categories based on their daily coffee intake: 0, less than 1, 1, 2, 3, 4, 5, and 6 or more cups per day.
Over an average follow-up of 4.5 years, 16,979 participants developed an incident arrhythmia. After adjusting for demographic characteristics, comorbid conditions, and lifestyle habits, the decreased risk with each cup of coffee was similar for atrial fibrillation or flutter (hazard ratio, 0.97) and supraventricular tachycardia (HR, 0.96).
Taking into account genetic variations that relate to caffeine metabolism did not modify the findings. Mendelian randomization analyses that used a polygenic score of inherited caffeine metabolism patterns “failed to provide evidence that caffeine consumption leads to a greater risk of arrhythmias,” the researchers said.
Professional society guidelines have suggested staying away from caffeinated products to reduce the risk of arrhythmia, but this guidance has “relied on assumed mechanisms and a small observational study from 1980,” the authors wrote. Subsequent research has indicated that coffee’s reputation of increasing the risk of arrhythmia may be undeserved.
“The investigators should be commended on performing a high-quality observational study to try to further understand the association between coffee consumption and arrhythmias, or the lack of one,” commented Zachary D. Goldberger, MD, MS, with the division of cardiovascular medicine at the University of Wisconsin–Madison, who was not involved in the study. “This is not a randomized, controlled trial, and coffee consumption was self-reported, but the methods employed are rigorous, despite these and other important limitations. However, we need to be extremely cautious in how we interpret these findings, and not use these data as a prescription for more coffee. 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. However, it should offer more reassurance that moderate coffee consumption is not necessarily harmful, and will not always lead to arrhythmias. This is important, given the widespread notion that coffee is universally proarrhythmic.”