Reference: JAMA Intern Med. 2021 Jul 19
By the time you’re reading this, you’ve probably already had your morning cup of coffee (at least the writers and editors at DynaMed have). As one of the most popular beverages on the planet, coffee intake not only increases alertness and focus, but it is associated with a wide range of potential health benefits including a decreased risk of liver disease, cancer, type 2 diabetes, cardiovascular disease, and Parkinson disease (just to name a few). For all these benefits, coffee (or rather caffeine consumption) is often blamed for provoking cardiac arrhythmias, though hard evidence for this link is lacking. A recent study however sought to clarify the relationship between the beloved beverage and its association to arrhythmias.
This prospective cohort study analyzed data of 386,258 participants from the UK Biobank between 2006 to 2018. Coffee intake was measured via questionnaire and participants were categorized by their coffee consumption (0, less than 1, 1, 2, 3, 4, 5, and 6 or more cups daily). The primary outcome was any incident arrhythmia including atrial fibrillation/flutter (AF), supraventricular tachycardia (SVT), ventricular tachycardia (VT), premature atrial complexes (PACs), and premature ventricular complexes (PVCs) according to ICD-9 and ICD-10 codes from inpatient and outpatient medical records. Incidence of individual arrhythmias were analyzed as secondary outcomes. Investigators also used genetic polymorphisms to estimate caffeine metabolism and compared it to coffee consumption and risk of arrhythmia.
A total of 16,979 incident arrhythmias occurred during a mean follow-up of 4.5 years. After adjusting for age, sex, race, ethnicity, comorbidities, and lifestyle factors, there was a 3% lower risk of incident arrhythmia (hazard ratio [HR] 0.97, P < 0.001) for every extra cup of coffee routinely consumed. When analyzed independently, results were similar for AF (HR, 0.97, P < 0.001) and SVT (HR, 0.96, P = 0.002). There were no statistically significant associations observed for VT, PACs, or PVCs. Participants with slower caffeine metabolism were found to consume less coffee. However, there were no significant associations between caffeine metabolism and incident arrhythmia.
Does this mean we should quit telling our patients to ditch coffee in an effort to reduce the risk of arrhythmia? Well, despite a robust sample size, true coffee consumption may have been underestimated or misreported due to self-reporting bias (when participants answer in a way that makes them look favorable to researchers). The lack of randomization is obviously a problem, but starting with an inception cohort could have also made a difference. It is possible that people with arrhythmias stop drinking coffee on their own without seeing a clinician, and then later appear to have had a “new” arrhythmia since they were not specifically queried about arrhythmias that occurred prior to the start of the observation period. The analysis also assumes that coffee consumption measured at baseline reflected consumption that continued throughout the study. 208,810 study participants were missing outpatient medical records so there may have been arrhythmias which were unaccounted for. Although drinking more coffee was correlated with a reduced risk of arrhythmia, investigators failed to analyze whether this link coincided with decreased mortality. Overall the association between coffee intake and arrhythmias remains murky but the data suggests that routinely recommending against coffee consumption to reduce arrhythmia risk is probably unjustified.
For more information, see the topic Atrial Fibrillation in DynaMed.
DynaMed EBM Focus Editorial Team
This EBM Focus was written by Nicole Jensen, MD, family physician at WholeHealth Medical. Edited by, Alan Ehrlich, MD, Executive Editor at DynaMed and Associate Professor in Family Medicine at the University of Massachusetts Medical School; Dan Randall, MD, Deputy Editor at DynaMed; Carina Brown, MD, Assistant Professor at Cone Health Family Medicine Residency; Katharine DeGeorge, MD, MS, Associate Professor of Family Medicine at the University of Virginia and Clinical Editor at DynaMed; Tanya Tupper, RT(N), CNMT, PET, Senior Medical Writer at DynaMed, Vincent Lemaitre, PhD, Medical Writer at DynaMed and Christine Fessenden, Editorial Operations Assistant at DynaMed.