Drinking coffee does not increase the risk of the most common arrhythmias, according to a study from the University of California at San Francisco (UCSF) presented today in The New England Journal of Medicine.
The study has found that when a person consumes coffee on a regular basis, they walk more than when they abstain. Specifically, 10% more steps per day, a fact that researchers attribute to the stimulating effect of caffeine. Conversely, sleep duration is shortened by 35 minutes a day when drinking coffee.
"Our results are reassuring for those who are concerned about the most common forms of arrhythmia, including atrial fibrillation," cardiologist Gregory Marcus, first author of the study, said by email. But he defends "an individualized strategy for coffee consumption."
The groups in which it may be advisable to limit or eliminate coffee consumption include, according to Marcus, "people who have difficulty sleeping." In addition, the results of previous research advise against the consumption of coffee during pregnancy, since caffeine reaches the fetus through the placenta and increases the risk of low birth weight.
For the majority of the population, regular coffee consumption is safe and even reduces the risk of several diseases, according to a growing number of investigations, now joined by that of UCSF. Coffee is associated with a lower risk of different types of cancer (breast, prostate, melanoma and liver, among others), Parkinson's (but not Alzheimer's, in which no effect has been detected), type diabetes 2 and on gallstones.
In the case of cardiovascular diseases, coffee has not been shown to increase the risk of hypertension, coronary diseases such as heart attacks or strokes. On the contrary, a consumption of between three and five cups a day has been associated with a reduction in cardiovascular risk.
But the question remained as to whether coffee can cause or aggravate arrhythmias. For this reason, coffee is discouraged for some people, although "the evidence in favor of this recommendation is conflicting," the authors of the new study write in The New England Journal of Medicine.
To clarify, one hundred healthy volunteers from California, half men and half women, with an average age of 39 years, have been given to wear a device to record their electrocardiogram for 14 days. In addition, they have worn an accelerometer on their wrist and a geolocator on their mobile to monitor their movements 24 hours a day, as well as a glucometer to control their blood sugar level.
Each volunteer has been told that they could have as much coffee as they wanted on some days and to abstain from coffee on others. In this way it has been possible to compare, for each person, what changes between the days that he drinks coffee and the days that he does not drink it.
The results show that the number of premature atrial contractions, which occur when an atrium (one of the chambers at the top of the heart) contracts at the wrong time, does not change significantly. Although they are quite common and usually irrelevant, they have been associated with the risk of developing atrial fibrillation, the most common type of arrhythmia. According to the results of the study, a healthy adult person suffers an average of 58 premature atrial contractions per day when they drink coffee and 53 when they do not.
On the contrary, a significant difference has been observed in the number of premature ventricular contractions. These occur when one of the ventricles (located in the lower part of the heart and larger than the atria) contracts at the wrong time. The difference has been 102 abnormal ventricular contractions per day without coffee and 154 with coffee.
Although usually of no consequence either, "people with more premature ventricular contractions may be at greater risk of developing heart failure," warns Gregory Marcus. "If someone has bothersome symptoms from this or is worried about heart failure, it may be worth trying to stop drinking coffee."
Study participants walked an average of 10,646 steps a day on days they drank coffee and 9,665 steps on days they didn't, a difference of 10%. This result confirms that of previous studies that had found that regular coffee consumption leads to a 5% increase in calorie expenditure and a reduction in weight gain with age. "The favorable effects of coffee on physical activity may outweigh other potentially detrimental effects," says Marcus.
Participants slept an average of 6 hours and 37 minutes on days they drank coffee and 7 hours and 12 minutes on days they did not. "Sleep is an important factor in numerous aspects of health, such as the risk of cardiovascular disease, cancer, and cognitive problems," the authors of the research point out in the scientific article in which they present their results. For this reason, they advocate that people with sleep disorders assess whether coffee consumption affects them negatively.
Caffeine concentration in the blood rises rapidly after drinking coffee, peaking 15 minutes to two hours after consumption, according to another article on the health effects of coffee published in 2020 in The New England Journal of Medicine. . Then it starts to go down and usually takes between 2.5 and 4.5 hours to halve, although there are important differences between people depending on their greater or lesser ability to metabolize caffeine and according to the medications they take.
