Contrary to conventional thinking, drinking lots of coffee appears to be associated with a lower risk of hospitalization for an arrhythmia, researchers found.
In a long-term prospective study, patients who reported drinking at least four cups of coffee a day were 18 percent less likely to be admitted with a heart rhythm disturbance than those who drank no coffee at all, according to Dr. Arthur Klatsky, a senior consultant in cardiology at Kaiser Permanente Division of Research in Oakland, Calif.
Tea consumption did not have a similar effect.
The findings, which were presented at the American Heart Association's Conference on Cardiovascular Disease Epidemiology and Prevention this week, were unexpected, Klatsky said, because patient reports of palpitation or forceful heartbeat after drinking coffee are not uncommon.
People who can't tolerate coffee or caffeine should avoid both, Klatsky said in an interview, advice that should not change based on the results of the study.
But, he said, people who regularly drink a moderate amount of coffee should be reassured.
"There's no reason, even if they have a heart rhythm problem or risk of a heart rhythm problem, why they have to give up the coffee," he said.
However, he continued, "we're not going to recommend that people drink coffee to prevent rhythm problems."
Dr. Kenneth Ellenbogen, director of the electrophysiology and pacing lab at Virginia Commonwealth University in Richmond, said the findings contradict what clinicians have been telling patients with arrhythmias -- that they should avoid coffee.
"I think the take-home message from this very important epidemiologic study is that most people can drink coffee, even several cups of coffee, without increasing their risk of having a significant heart rhythm disturbance that would require hospitalization," said Ellenbogen, an AHA spokesman.
Although conventional wisdom dictates that coffee can increase the risk of arrhythmia, few studies have explored the relationship, according to Klatsky.
So he and his colleagues analyzed data on 130,054 men and women who were treated at Kaiser. As part of a baseline medical check-up between 1978 and 1985, all participants completed a questionnaire that included information on coffee, alcohol, and tea consumption. Most were not asked to differentiate between caffeinated and decaffeinated coffee.
Through follow-up, 2.6 percent were hospitalized for an arrhythmia; half had a serious heart rhythm disturbance known as an atrial fibrillation.
When coffee drinking was evaluated as a continuous variable, increasing consumption was associated with decreasing risk of hospitalization.
The findings were consistent across types of rhythm disturbance and patient subgroups. Even when smoking status, age, sex, ethnicity, alcohol consumption, body mass index, and education were taken into account, they did not substantially affect the findings.
In the small subset of 11,656 patients who provided specific information on their coffee consumption, it appeared the risk reduction was primarily attributed to caffeine, Klatsky said, although the small numbers precluded drawing firm conclusions.
While the observational design of the study meant that it could not establish a causal relationship, Klatsky said it was plausible that caffeine could be the protective agent involved.
"I do think this [study] is going to surprise people," he said. "I think conventional wisdom is that coffee can cause palpitations and it can cause rhythm problems. I think, though, that conventional wisdom is not always right, and the data that were available before this study really do not support the idea that moderate amounts of coffee provoke rhythm problems."