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Acute Effects of Coffee Consumption on Health Among Ambulatory Adults
Coffee is one of the most commonly consumed beverages in the world, but the acute health effects of coffee consumption remain uncertain.
We conducted a prospective, randomized, case-crossover trial to examine the effects of caffeinated coffee on cardiac ectopy and arrhythmias, daily step counts, sleep minutes, and serum glucose levels. A total of 100 adults were fitted with a continuously recording electrocardiogram device, a wrist-worn accelerometer, and a continuous glucose monitor. Participants downloaded a smartphone application to collect geolocation data. We used daily text messages, sent over a period of 14 days, to randomly instruct participants to consume caffeinated coffee or avoid caffeine. The primary outcome was the mean number of daily premature atrial contractions. Adherence to the randomization assignment was assessed with the use of real-time indicators recorded by the participants, daily surveys, reimbursements for date-stamped receipts for coffee purchases, and virtual monitoring (geofencing) of coffee-shop visits.
The mean (±SD) age of the participants was 39±13 years; 51% were women, and 51% were non-Hispanic White. Adherence to the random assignments was assessed to be high. The consumption of caffeinated coffee was associated with 58 daily premature atrial contractions as compared with 53 daily events on days when caffeine was avoided (rate ratio, 1.09; 95% confidence interval [CI], 0.98 to 1.20; P = 0.10). The consumption of caffeinated coffee as compared with no caffeine consumption was associated with 154 and 102 daily premature ventricular contractions, respectively (rate ratio, 1.51; 95% CI, 1.18 to 1.94); 10,646 and 9665 daily steps (mean difference, 1058; 95% CI, 441 to 1675); 397 and 432 minutes of nightly sleep (mean difference, 36; 95% CI, 25 to 47); and serum glucose levels of 95 mg per deciliter and 96 mg per deciliter (mean difference, -0.41; 95% CI, -5.42 to 4.60).
In this randomized trial, the consumption of caffeinated coffee did not result in significantly more daily premature atrial contractions than the avoidance of caffeine. (Funded by the University of California, San Francisco, and the National Institutes of Health; CRAVE ClinicalTrials.gov number, NCT03671759.).
Disclosure statements are available on the authors' profiles:
Acute Effects of Coffee Consumption on Health among Ambulatory AdultsN. Engl. J. Med 2023 Mar 23;388(12)1092-1100, GM Marcus, DG Rosenthal, G Nah, E Vittinghoff, C Fang, K Ogomori, S Joyce, D Yilmaz, V Yang, T Kessedjian, E Wilson, M Yang, K Chang, G Wall, JE Olgin
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
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Although coffee is one of the most commonly consumed substances in the world, the great majority of research regarding health effects have been observational and therefore prone to confounding by other factors. The Coffee and Real-time Atrial and Ventricular Ectopy (CRAVE) trial was a randomized, case–crossover assessment of acute health effects attributed to coffee consumption. One hundred volunteers were fit with wearable continuously recording ECG devices, a wrist-worn accelerometer to assess step counts and sleep, and a continuously recording glucose monitor. Their DNA was genotyped for common genetic variants that influence caffeine metabolism. Participants were then randomized via daily text messages to either consume all the caffeinated coffee they wanted versus to avoid all caffeine. Adherence to the randomization assignment was assessed by: 1) real-time participant activation button presses on the ECG monitor to timestamp every cup of coffee (a strategy previously validated by the same group for alcohol consumption compared with wearable alcohol sensors1); 2) daily surveys regarding the previous day’s coffee consumption; 3) reimbursing all coffee consumption evidenced by a date-stamped receipt of coffee purchased for immediate consumption (whether they were supposed to have coffee that day based on randomization assignment or not); and 4) the Eureka digital research mobile application installed on participants’ smartphones, which was used to “geofence” visits to those coffee shops.
In both intention-to-treat analyses and “as-treated” (based on the amount of coffee actually consumed), no statistically significant differences in the primary outcome — premature atrial contraction (PAC) counts — were observed when individuals were exposed to caffeinated coffee versus no caffeine. In contrast, days randomized to coffee were associated with 51% more premature ventricular contractions (PVCs) (rate ratio [RR], 1.51; 95% CI, 1.18–1.94). In the as-treated analysis, those who consumed more than two cups of coffee experienced more than a doubling of their PVCs (RR, 2.24; 95% CI, 1.06–4.71). On days randomly assigned to coffee, participants took about 1000 more steps (mean difference, 1058 steps; 95% CI, 441–16750) but experienced more than a half-hour less sleep (36 fewer minutes of sleep per night; 95% CI, 25–47). Despite epidemiologic evidence that coffee consumers experience a lower risk of developing diabetes, no differences in serum glucose were observed in any of the analyses comparing exposure to coffee with caffeine avoidance. Two statistically significant interactions by caffeine metabolism–related genotype were observed: faster caffeine metabolizers exhibited an amplified relationship between coffee and an increased frequency of PVCs, whereas the slower caffeine metabolizers experienced the worst sleep when exposed to coffee (mean, −47 min; 95% CI, −69 to −25 min). In fact, the fast caffeine metabolizers experienced no detectable differences in sleep when exposed to coffee.
Taken all together, these data reveal complex acute effects of coffee related to several physiologic processes fundamental to overall health that themselves manifest heterogeneously across individuals. While those concerned about the frequency of PACs (a potent harbinger of atrial fibrillation risk2) should be reassured, those concerned about PVC frequency (and the associated risk of subsequent heart failure3) might consider reducing or eliminating coffee. Although the health benefits of coffee may arise from motivating more physical activity, those struggling with insomnia should incorporate these randomized data to motivate at least a trial of strict coffee avoidance to determine if it might benefit their sleep.