March 2, 2010 -- People with disturbances in their heart rhythms are often advised to avoid caffeinated coffee, but a new study shows that moderate coffee drinking actually reduces the risk of being hospitalized for heart rhythm problems.
''People who reported four or more cups a day had almost an 18% reduction in the risk of being hospitalized for rhythm disturbances," says study researcher Arthur L. Klatsky, MD, senior consultant in cardiology at Kaiser Permanente Division of Research in Oakland, Calif.
The findings are due to be presented at this week's American Heart Association's 50th Annual Conference on Cardiovascular Disease Epidemiology and Prevention in San Francisco.
While experts have long known that very large doses of caffeine, coffee's most active ingredient, are linked with rhythm disturbances, less research has been done on the effect of typical daily coffee intake. The results are somewhat surprising, Klatsky says, since patients sometimes report feeling palpitations after drinking coffee.
Klatsky and his team evaluated data from more than 130,000 members of Kaiser Permanente, a large prepaid health care plan. During routine health exams over the years 1978 to 1985, participants provided information about coffee drinking and other habits such as drinking alcohol or smoking.
''We followed up this large group until 2008," Klatsky says.
The findings showed:
- 27% did not drink coffee.
- 14% had less than a cup a day.
- 42% had one to three cups a day.
- 17% had four or more cups a day.
Over the course of the follow-up, 3,137 people had a hospital discharge diagnosis of cardiac dysrhythmia. ''Half of the people had atrial fibrillation," Klatsky tells WebMD. In atrial fibrillation, the heart's two small upper chambers, or atria, quiver instead of beating effectively.
About 2.2 million Americans have atrial fibrillation, according to the American Heart Association. About 15% of those who suffer a stroke have the disorder.
Reduction in Hospitalizations
Those who drank the most coffee, four cups or more a day, had the biggest reduction in risk of being hospitalized for a heart rhythm problem, Klatsky found.
Those who drank one to three cups daily had a 7% reduction in risk.
''It doesn't prove cause and effect," he emphasizes. "A single, observational study can't."
But Klatsky describes the reduction in risk as ''meaningful'' and says that ''it's quite unlikely to be due to chance."
The reduced risk was similar in men, women, whites, and African-Americans, he found.
Exactly how coffee may reduce the risk isn't clear, he says.
The study findings seem to reaffirm what some heart specialists know from their clinical experience, says Sumeet S. Chugh, MD, associate director of the Heart Institute at Cedars-Sinai Medical Center, Los Angeles, who reviewed the findings for WebMD.
''It's a reaffirmation of the fact that we don't think coffee is related to generating an arrthymia," he says. The researchers "are affirming in a much larger universe of patients that coffee drinking to a moderate extent is not increasing or decreasing the risk of arrhythmias.''
The study doesn't address the effects of coffee if you already have a rhythm disturbance, Chugh says. ''If someone has an arrhythmia, I say, 'Cut back and let's see.' Sometimes it goes away."
One weakness of the study, Chugh says, is that the researchers totaled the diagnoses of heart rhythm problems by hospital codes, and these sometimes can be incorrect, he says.