Coffee Doesn’t Disturb Heart Rhythm: UK Biobank Analysis

A daily jolt of coffee doesn’t appear to provoke arrhythmias and in fact is linked to significantly lower risks of not only atrial fibrillation (AF) but also less-common conditions like supraventricular and ventricular tachycardia, data from the UK Biobank study show.

In a population with a median consumption of two cups per day, each serving was associated with a 3% relative reduction in risk, researchers report in a study published this week in JAMA Internal Medicine.

“Conventional wisdom holds that caffeine causes arrhythmias and that, once an arrhythmia is diagnosed, caffeine should be avoided,” senior author Gregory M. Marcus, MD (University of California, San Francisco), told TCTMD in an email. “However, this is based on only a few studies in relatively small numbers of individuals and anecdotal reports where the more-rare cases of caffeine-sensitive arrhythmias may have subsumed recommendations pertinent to the great majority of individuals.”

With many patients following the advice to avoid caffeine, it’s been impossible to know how often arrhythmias would have occurred otherwise, Marcus explained. In recent years, he added, carefully conducted observational studies have shown coffee to have no effect on AF or to actually be protective against that particular arrhythmia.

As such, the reduced AF risk seen here wasn’t unexpected, said Marcus, though “we were surprised that in no circumstance could we identify a type of abnormal heart rhythm that appeared to be more likely among those who consumed more coffee.”

Their findings as a whole show that “blanket prohibitions against coffee consumption with the intent of avoiding arrhythmias are likely not warranted,” he stressed.

UK Biobank Data

Led by Eun-jeong Kim, MD (University of California, San Francisco), the researchers analyzed data from the UK Biobank that was prospectively collected between 2006 and 2018 for 386,258 individuals (mean age 56 years; 52.3% women). Around one-quarter did not drink caffeinated coffee, while one-quarter consumed fewer than the median level of two cups per day and half drank at least two cups. People whose daily coffee quota was less than the median tended to be older, white, and male; were more apt to smoke and drink alcohol, but less apt to drink tea; and were more likely to have PAD and cancer, but less likely to have hypertension, diabetes, and chronic kidney disease.

In all, 16,979 people developed an arrhythmia over a mean follow-up of 4.5 years. These were predominately AF (75%), followed by supraventricular tachycardia (11%), ventricular tachycardia (5%), premature ventricular complexes (4%), and premature atrial complexes (< 1%). Around 4% had unspecified arrhythmias.

Adjusted for demographics (eg, age, sex, educational level, and race/ethnicity), comorbidities (eg, hypertension, diabetes, CVD, and cancer), and lifestyle (eg, physical activity, smoking, and alcohol use), arrhythmia risk decreased by 3% for each cup of coffee (HR 0.97; 95% CI 0.96-0.98). Atrial fibrillation and/or flutter and supraventricular tachycardia were reduced by a similar magnitude.

Further analyses focused on genetic variants associated with caffeine metabolism. While people whose bodies processed caffeine more slowly tended to drink less coffee, the association between coffee consumption and arrhythmia risk remained largely the same for these individuals. A mendelian randomization study based on these genetic traits also confirmed the arrhythmia link.

“These data suggest that common prohibitions against caffeine to reduce arrhythmia risk are likely unwarranted,” Kim et al conclude. Still, “it is plausible that some individuals experience coffee or caffeine-induced arrhythmias, whereas others do not,” the researchers acknowledge. For instance, there may be genes related to arrhythmia risk (rather than caffeine metabolism) that modify the association.

The majority of individuals . . . should be able to enjoy their coffee, and perhaps associated health benefits, without worrying about the risks of cardiac arrhythmias. Gregory M. Marcus

Marcus said the idea that caffeine can trigger arrhythmias is “very widely” held among clinicians.

“In my own cardiac electrophysiology clinic practice, it is essentially the norm that patients seeing me for the first time for an arrhythmia diagnosis or palpitations have already been instructed by their primary care physicians or general cardiologists” to avoid caffeine, he told TCTMD. Indeed, US guidelines for ventricular arrhythmias and for supraventricular arrhythmias advise caffeine avoidance.

Marcus said he wouldn’t recommend patients start drinking coffee as a means to reduce their risk, but rather wouldn’t automatically recommend against it.

“In my clinical practice, I frequently suggest patients experiment with coffee if drinking coffee is something they enjoy—in that admittedly anecdotal experience, most patients do not experience an increase in their arrhythmias and in some cases I have observed a reduction in their arrhythmias,” said Marcus.

While most people don’t need to take precautions, though, some have a “fairly idiosyncratic response to caffeine,” he said, and those who find it exacerbates their symptoms should reduce or avoid it. Fortunately, “the majority of individuals . . . should be able to enjoy their coffee, and perhaps associated health benefits, without worrying about the risks of cardiac arrhythmias,” Marcus concluded.