While a shot of espresso may give people the sensation their hearts are racing, drinking more coffee reduced the likelihood that patients would be hospitalized for irregular heartbeats, researchers found.
A study of 130,054 adults found that people who drank four cups or more of coffee daily had an 18 percent lower risk of being hospitalized for irregular heartbeats and other heart- rhythm conditions than noncoffee drinkers, researchers at the health system Kaiser Permanente said Wednesday. The risk of hospitalization was 7 percent lower for people who drank one to three cups of coffee daily, the researchers said.
Cardiac rhythm disorders are problems in the heart's electrical systems that cause it to beat too fast, too slow or irregularly. Atrial fibrillation, a rapid, irregular heart beat that is the most common of these conditions, will affect an estimated 2.7 million Americans in 2010, according to the U.S. Centers for Disease Control and Prevention.
"People who are moderate coffee drinkers can be reassured that they are not doing harm because of their coffee drinking," said Arthur Klatsky, the study's lead investigator and a cardiologist at Kaiser's Division of Research.
The study is scheduled for presentation March 5 at an American Heart Association conference on cardiovascular disease in San Francisco.
The study's findings may be surprising because high doses of caffeine have been associated with a perception of heart "racing" in people, Klatsky said. Previous studies on the topic haven't found that the racing impression is a measurable increase in heart rate or an irregular heartbeat, he said.
The study looked at 130,054 adults who were members of the Kaiser Permanente health plan and had filled out questionnaires about their coffee- and tea-drinking habits from 1979 to 1985. The patients' health status was followed until 2008.
The 18 percent reduction in risk of hospitalization for those who drank four or more cups of coffee daily was consistent for men and women, different ethnic groups, and smokers and nonsmokers, according to the study.
The study shows "a progressive reduction in risk" of heart irregularities the more coffee people drank, Klatsky said. The research doesn't prove a cause-and-effect relationship between reduced risk and coffee drinking or that coffee protects the heart against such irregularities, he said.
"We shouldn't jump to the conclusion that there is a protective effect of coffee, although the study suggests there might be," he said.