finally a prospective crossover design study, even with a smallish sample size (100)


https://www.nejm.org/doi/full/10.1056/NEJMoa2204737

In this randomized trial, the consumption of caffeinated coffee did not result in significantly more daily premature atrial contractions than the avoidance of caffeine.

I'd like to read the full report in addition to the abstract. There was an increase in premature atrial contractions with caffeine intake, but just not enough to be considered "significant." There seemed to be an even greater increase in more worrisome premature ventricular contractions, though again not enough to be considered significant. You'd need a much larger study population to define how strongly caffeine consumption relates to cardiac ectopy. Outfitting 100 people with ZioPatch monitors and analyzing the data wasn't cheap, so it's nice they got this study done. Maybe they could use the results to convince someone to fund a study of several thousand subjects... There are also other confounders that need to be considered, like whether or not (and how much) caffeine abstinence is associated with cardiac irregularities.