Originally published by 2 Minute Medicine^® (view original article). Reused on AccessMedicine with permission.

1. In this case-crossover study, consumption of caffeinated coffee was associated with fewer minutes of sleep per night and increased levels of daily activity.

2. Consumption of caffeinated coffee did not have a significant association with rates of premature daily atrial contractions.

Evidence Rating Level: 2 (Good)

Study Rundown:

Despite being one of the most prevalent compounds regularly consumed worldwide, the acute impacts of caffeine on health, such as its suspected proarrhythmic effects, are not yet clearly known. The present study had a prospective case-crossover design with the aim of evaluating the health impacts of caffeine. Specifically, the primary outcome of interest was the effect of coffee on several cardiac metrics, activity levels, sleep, and blood glucose levels over 14 days. The study found that caffeine was indeed associated with increased daily premature ventricular contractions, less sleep per night, and increased activity levels daily. However, it was not associated with increased rates of daily premature atrial contractions nor differences in blood glucose. In terms of limitations, this was an unblinded study with a relatively small sample size. However, these results are helpful in building the evidence base toward a better understanding of the acute health effects of caffeine. Although caffeine has long been considered a pro-arrhythmic compound, its effects on cardiac ectopy may yet be as straightforward as previously thought. Further large-scale, blinded investigations would further reduce bias levels and help clarify these effects.

Click to read the study in NEJM

In-Depth [case-crossover study]:

This study was a prospective, randomized case-crossover design trial evaluating the effect of caffeinated coffee on health. The primary outcomes of interest were: cardiac ectopy, activity levels, amount of sleep in minutes, and blood glucose levels. Participants were invited to participate if they were over 18 years of age, consumed caffeinated coffee at least once per year, and could use the Eureka smartphone application on their own smartphone. Participants with known atrial fibrillation in the past, heart failure, an implanted cardiac device, those with a medical reason to avoid coffee, or those on select antiarrhythmic medications were excluded from the study. After applying the inclusion and exclusion criteria, 100 participants were randomly assigned to the caffeinated coffee arm, or to abstain from consuming caffeine over select two-day periods for 14 days of the study’s duration. Primary results of the analysis found that there was no significant difference between the consumption of caffeinated coffee compared to caffeine avoidance in the number of daily premature atrial contractions (Rate Ratio, 1.09; 95% Confidence Interval [CI], 0.98 to 1.20). However, it was associated with a significantly increased rate of daily premature ventricular contractions (rate ratio, 1.51; 95% CI, 1.18 to 1.94). Further, results suggest that daily caffeine consumption is associated with increased activity levels and reduced minutes of sleep per night. There was no evidence to support that caffeine consumption was associated with mean daily glucose levels within this study. Overall, this study supports the evidence base of several known effects of caffeine, although it was not associated with a significant increase in premature atrial contractions daily.

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