The positive impact of coffee on the risk of atrial fibrillation

Atrial fibrillation (AF) is an arrhythmia characterized by very irregular (and most often rapid) heartbeats due to a disruption in the electrical activity of the left atrium, the chamber of the heart that receives oxygenated blood from the lungs. The transmission of the electrical signal becomes so chaotic that there is no proper contraction of the atrium, and the resulting stagnation of blood can lead to the formation of a clot (thrombus) that can be ejected at any time into the bloodstream via the aorta and reach the brain. Atrial fibrillation (AF) is the most common heart rhythm disorder in the population, affecting approximately one in three people during their lifetime and, if left untreated, is a leading cause of stroke.

For patients with AF that cannot be corrected with antiarrhythmic medications or that require emergency intervention, a common procedure is to restore a normal heart rhythm using cardioversion. This technique involves administering, under anesthesia, an electrical shock at a precise point in the heart rhythm, which briefly stops the heartbeat, and after a second or two, the heart resumes beating at a normal rate. Despite this short-term success, however, AF episodes frequently recur after cardioversion, with rates often reaching 50% or more within the first year, and sometimes even within the first month. Identifying factors that could prevent these recurrences, or at least reduce their frequency, is therefore of considerable interest for improving patients’ quality of life.

Coffee: an antiarrhythmic stimulant?

It is generally accepted that stimulants like caffeine have the potential to trigger arrhythmias, and for this reason, one of the most frequently recommended lifestyle changes for patients with atrial fibrillation (AF) is to reduce or even stop coffee consumption. However, this proarrhythmic effect of coffee remains somewhat unclear, as observational studies have generally not observed an increased risk of AF in coffee drinkers (see here and here, for example), and in fact, the majority of these studies report a decreased risk in coffee drinkers. This lack of negative effect is also suggested by a recent randomized clinical trial which observed that the consumption of caffeinated coffee did not lead to an increased number of premature atrial contractions, known to trigger episodes of AF.

The results of the DECAF (Does Eliminating Coffee Avoid Fibrillation) randomized trial, presented in early November at the American Heart Association’s annual meeting, confirm the absence of a negative effect of coffee on the risk of atrial fibrillation (AF). In this multicenter clinical trial, 200 patients with persistent AF (mean age 69 years) who had successfully undergone cardioversion were randomly divided into two groups: 1) a “coffee” group, who could continue to consume coffee regularly (an average of 1 cup per day, or about 7 cups per week), and 2) an “abstinent” group, who had agreed to eliminate coffee (and all forms of caffeine) from their daily routine. The study’s primary endpoint was any recurrence of AF lasting longer than 30 seconds within six months of cardioversion, as detected clinically or recorded by a device.

The results unequivocally show that coffee consumption is beneficial for patients with AF (Figure 1): its positive effect appears very early, as early as the first month of the study, and at six months, the probability of AF recurrence drops from 64% in the “abstinence” group to 47% in the “coffee” group, representing a 39% reduction in the risk of recurrence among regular coffee drinkers. In other words, not only does moderate coffee consumption (1 cup per day) appear to be completely safe for people with AF, but it could even improve their condition by reducing the risk of arrhythmia recurrence.

Coffee is good for the heart

These results add to the growing list of cardiovascular benefits attributable to coffee consumption that have been highlighted in recent years (see our article on this topic). Coffee is not simply a source of caffeine; rather, it is a very complex plant-based beverage containing several hundred phytochemicals (polyphenols, for example) that have positive effects on several processes involved in the development of chronic diseases (inflammation and insulin resistance, among others). It is therefore essential to avoid extrapolating the benefits observed in this study to caffeine present in high doses in other products, particularly energy drinks. These synthetic products do not provide anything truly useful beyond a temporary reduction in fatigue, and some studies suggest that certain additives they contain may have negative effects on cardiovascular and overall health (for example, taurine, a non-essential amino acid commonly added to energy drinks, has recently been observed to stimulate the growth of an aggressive type of leukemia).