Conventional thinking about caffeine can increase the risk of cardiac arrhythmias is common.¹ Although some professional society guidelines warn against caffeine consumption to avoid arrhythmias, data clarifying this claim have been mixed and there is growing evidence to suggest coffee consumption may actually lower the risk for arrhythmias, diabetes and even mortality.¹ Professor Gregory M Marcus, Associate Chief of Cardiology for Research and Endowed Professor of Atrial Fibrillation Research at the University of California, San Francisco, and his team assessed the association between consumption of common caffeinated products and the risk of arrhythmias in The Coffee and Real-time Atrial and Ventricular Ectopy (CRAVE) trial, providing clinicians with an overview of the apparent benefits and risks associated with consuming caffeinated coffee.¹ While the majority of long-term observational studies have suggested multiple potential benefits of drinking coffee, this is the first randomized trial to investigate the effects of coffee consumption on cardiac ectopy, sleep and other factors, including serum glucose and physical activity.¹

The trial enrolled 100 healthy young volunteers, with no prior arrhythmias or cardiovascular (CV) disease, in which 51% were females with median age of 38 years and 48% were non-Hispanic White. Each participant was fitted with a continuously recording electrocardiogram (ECG) device, a continuous glucose monitor and a Fitbit and was randomized to consume or avoid coffee each day for 14 days and received daily texts and reminders.¹ At baseline, approximately 30% of participants reported drinking at least one cup of coffee per day, with 21% reporting two to three cups per day.¹ To assess adherence, participants were asked to press the button on the ZioPatch for every coffee drank and were queried daily regarding the actual coffee consumption the previous day.¹

Primary outcomes were premature atrial contractions (PACs) and daily premature ventricular contractions (PVCs) while the secondary outcomes assessed the daily counts of supraventricular tachycardia (SVT), daily counts of ventricular tachycardia (VT), daily mean step counts, nightly mean sleep duration and daily mean glucose.¹ Upon analysis, results indicated compliance with randomization assignment according to every metric used to measure compliance (p< 0.01).¹ After adjustment for demographic characteristics, comorbid conditions and lifestyle habits, intention-to-treat (ITT) analyses were associated with 54% (95% CI: 19-200, p=0.001) increase in PVCs; 36 (95% CI: 22-50, p<0.001) fewer minutes of sleep per night; and 1,058 (95% CI: 441-1,675, p=0.001) additional Fitbit-based steps per day.¹ Whereas the results of per-protocol analysis suggested each additional cup of habitual coffee consumed was associated with 587 (95% CI: 355-820, p<0.001) more steps per day, and 18 (95% CI:13-23, p<0.001) fewer minutes of sleep per night.¹ There were no differences between coffee drinking or not on the incidence of PACs [Relative risk (RR)=1.09; 95% CI: 0.98-1.2].¹ Drinking more coffee was associated with fewer episodes of supraventricular tachycardia (RR=0.84; 95% CI: 0.69-1.03), but with more PVCs (HR=1.54; 95% CI: 1.19-2.00).¹ By genetic analysis, slow caffeine metabolizers were more likely to be affected by sleep deprivation as compared with the fast metabolizers (p<0.001).¹

ZioPatch data collected over a median of 13.3 days showed a daily median of 12.8 PACs, 7.5 PVCs, 1 non-sustained SVT, and 1 non-sustained VT.¹ There were no significant differences observed when assessing glucose levels based on coffee consumptions.¹ Prof. Marcus highlighted coffee consumption increased physical activity among the participants, therefore increasing the health benefits such as reduced risks of type 2 diabetes and several cancers, and is associated with greater longevity.¹ He further emphasized the adverse psychiatric, neurologic and cardiovascular outcomes associated with reduced sleep.¹ Additionally, he cautioned that although findings did show coffee consumption enhanced overall physical activity, but the risk should be weighed against reduced sleep outcomes.¹ Prof. Marcus concluded, “the CRAVE trial demonstrated that coffee consumption was associated with no increase in atrial arrhythmias, but increased PVCs and physical activity, and reduced sleep in the overall healthy participants.”