In a new study from the University of California, San Francisco, researchers found drinking caffeinated coffee appears to have both beneficial and harmful short-term health effects: increased abnormal heartbeats increased physical activity and reduced sleep duration.
Coffee is the most commonly consumed beverage in the world, yet its health effects remain uncertain.
In the study, the team enrolled 100 adult volunteers, and they were assigned to wear continuously recording ECG devices (to track heart rhythm), wrist-worn devices to track physical activity and sleep; and continuous glucose monitors to track blood sugar levels for two weeks.
The participants were an average age of 38 years, 51% were women and 48% were white.
Researchers also obtained DNA saliva samples from the participants to assess genetic variants that may affect caffeine metabolism.
Participants were then randomly assigned to either avoid or consume coffee for no more than two consecutive days each for 14 consecutive days.
The team found that coffee consumption was associated with a 54% increase in premature ventricular contractions, a type of abnormal heartbeat originating in the lower heart chambers reported to feel like a skipped heartbeat.
In contrast, drinking more coffee was linked to fewer episodes of supraventricular tachycardia, an abnormally rapid heart rhythm arising from the upper heart chambers.
Consuming coffee was consistently associated with more physical activity as well as less sleep. Specifically:
Participants who consumed coffee logged more than 1,000 additional steps per day compared to days when they did not drink coffee.
On the days participants drank coffee, they had 36 fewer minutes of sleep per night according to their Fitbit devices.
Drinking more than one coffee drink more than doubled the number of irregular heartbeats arising from the heart’s lower chambers.
Each additional cup of coffee consumed was associated with nearly 600 more steps per day and 18 fewer minutes of sleep per night.
There were no differences in continuously recorded glucose measured when the study participants consumed versus avoided coffee.
The team says more physical activity, which appears to be prompted by coffee consumption, has numerous health benefits, such as reduced risks of Type 2 diabetes and several cancers, and is associated with greater longevity.
On the other hand, reduced sleep is associated with a variety of adverse psychiatric, neurologic and cardiovascular outcomes.
More frequent abnormal heartbeats from the upper heart chambers influence risk of atrial fibrillation, and more frequent abnormal beats from the lower chambers, or ventricles, increase the risk of heart failure.
These results highlight the complex relationship between coffee and health.
The study is presented at the American Heart Association’s Scientific Sessions 2021. One author of the study is Gregory Marcus, M.D., M.A.S.
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