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Coffee and Your Heart: The Impact May Be Different Than You Think
New study finds no effect on atrial contractions though there may be other health impacts
Americans drank 517 million cups of coffee a day in 2022.
By Julie Wernau, WSJ
Updated March 22, 2023 5:08 pm ET
Coffee lovers take heart. America’s favorite stimulant might not be so risky for cardiac health after all, but there may still be other health effects, researchers say.
Coffee consumption doesn’t increase abnormal heartbeats associated with an increased risk of the most common heart rhythm disturbance, according to a new study published Wednesday in the New England Journal of Medicine. Researchers monitored the hearts, activity and sleep of 100 people without underlying heart conditions over two weeks. They found that the key cardiac risk marker remained about the same for coffee drinkers as it did for non-coffee drinkers. The irregular heart rhythm known as atrial fibrillation, can lead to dangerous blood clots that can cause stroke and heart failure.
“The common arrhythmia known as atrial fibrillation isn’t caused or worsened by caffeine, despite the widespread belief among many physicians and patients that coffee should be avoided in these conditions,” said Deepak Bhatt, director of Mount Sinai Heart in New York, who wasn’t involved in the study.
Cardiologists have long considered coffee a potential heart health risk in individuals with underlying health conditions since it contains caffeine, a stimulant that increases heart rate. A study published in the Journal of the American Heart Association in 2022 found that drinking two or more cups of coffee a day was associated with twice the risk of heart death in people with severe hypertension compared with non-coffee drinkers. But other research has shown an association between moderate coffee intake and a reduced risk of mortality in the population overall. Researchers are still trying to understand the underlying reasons for these effects.
The group of 100 volunteers, ranging from their 20s to their 70s, were strictly monitored. Researchers had them wear continuously recording electrocardiogram devices, which record electrical signals from the heart, Fitbits to monitor their step counts and sleep, and continuous glucose monitors.
The participants also downloaded a smartphone application that tracked their location so that researchers knew when they had entered a coffee shop. The study authors texted instructions each night letting them know the days they could drink coffee or needed to avoid caffeine altogether.
Americans drank 517 million cups of coffee a day in 2022, according to the National Coffee Association, and 66% of Americans surveyed reported drinking coffee within the past day.
Other findings from the study painted a more mixed picture of coffee’s impact on health. People who were assigned to drink coffee recorded 10% more steps—10,646 steps versus 9,665 for non-coffee drinkers—with steps increasing the more coffee they drank. Several large prospective studies have found a 6%-15% reduction in mortality associated with additional steps each day.
But coffee drinkers also recorded 35 fewer minutes of sleep per night. Research points to significantly increased mortality risk for people who don’t get enough sleep. The study also found coffee drinkers had a higher number of premature ventricular heartbeats (154 versus 102 a day for no-caffeine days), a type of irregular heartbeat that can contribute to heart weakening if experienced at much higher levels over several years.
Since the risk of premature atrial contractions and atrial fibrillation increases with age, it is unclear how the findings might affect older patients than those who participated in the study, said Muhammad Afzal, a clinical assistant professor of internal medicine at the Ohio State University Wexner Medical Center, who wasn’t involved in the study. At the same time, patients with symptomatic premature ventricular contractions should avoid or minimize coffee consumption based on the findings, he said.
The electrical signal that starts your heartbeat typically comes from the top right chamber of the heart, or the atrium. Premature ventricular contractions occur when the electrical signal that starts your heartbeat comes from one of your bottom two heart chambers and makes the heart contract differently. It can feel like a skipped heartbeat, according to the Cleveland Clinic. The contractions are common and typically not problematic unless they represent a large number of heartbeats, according to research findings.
Premature atrial contraction is only problematic at higher frequency. Most people experience them at least once a day. When the signal comes early, there may not be much blood in the heart at the moment, according to the Cleveland Clinic.
“A pause and a strong beat may follow the extra heartbeat, making it feel like a skipped beat,” the medical group concluded.
At the same time, participants in the NEJM study were tested for genetic markers that determined if they were likely to metabolize caffeine slowly or more quickly. Those with a slower metabolism lost nearly an hour of sleep a night and faster metabolizers experienced more premature ventricular contractions when they consumed coffee.
“The true health effects of coffee are complicated,” said lead study author Gregory Marcus, professor of medicine in residence and endowed professor in atrial fibrillation research at the University of California, San Francisco. “That is just the nature of the substance that is one of the most commonly consumed substances in the world.”
A study published last May in the Annals of Internal Medicine used U.K. Biobank Data from 171,616 people that detailed their coffee-drinking habits and followed their health outcomes over several years. The study found that moderate coffee drinkers were 30% less likely to die, even after accounting for lifestyle and socioeconomic factors. Those benefits dissipated as people increased their intake.
Dr. Larry Chinitz, director of the Heart Rhythm Center and co-lead of NYU Langone Heart, said if people are looking to improve their heart health, drinking coffee or staying away from it isn’t likely to be the most critical factor.
He said the kind of lifestyle choices that most people need to make to prevent and control cardiac conditions are much harder than picking up or avoiding that daily cup of coffee.
“People ignore exercise, diet and sleep patterns, and those may be the greatest contributors to cardiovascular disease,” he said.
Write to Julie Wernau at julie.wernau@wsj.com