Kim EJ, Hoffmann TJ, Nah G, et al. - This prospective cohort study showed that habitual coffee intake and genetically mediated differences in caffeine metabolism both were not related to a heightened risk of cardiac arrhythmias.

• From the UK Biobank, longitudinal data were analyzed from 386,258 persons (mean [SD] age, 56 [8] years; 52.3% female).

• Development of an incident arrhythmia was seen in 16,979 participants during a mean (SD) follow-up of 4.5 (3.1) years.

• Greater amounts of habitual coffee intake were related to a lower risk of arrhythmia.

• A 3% decreased risk of developing an arrhythmia (hazard ratio [HR], 0.97) was observed in relation to each additional daily cup of coffee consumed.

• These links were not significantly altered by genetic variants that impact caffeine metabolism.

• For atrial fibrillation and/or flutter and supraventricular tachycardia, statistically significant associations showing a similar magnitude were noted with HR, 0.97 and 0.96, respectively.

• Mendelian randomization did not provide evidence that caffeine intake was linked with arrhythmias.