Caffeine, Heart Rhythm Link Is Questioned

Dedicated coffee drinkers may perceive it as good news: Contrary to the warnings of several previous studies, Canadian researchers have concluded that even heavy coffee consumption of 3 to 7 cups a day doesn’t trigger possibly dangerous changes in heart rhythm.

The new study at Victoria General Hospital in Halifax examined 34 subjects--average age: 31--who drank large amounts of coffee for 24 hours while hooked up to portable monitors that track heart movements continuously during routine activity.

The study was a sequel to earlier research concluding that, since coffee’s active ingredient, caffeine, is a type of stimulant, drinking the brew increased the incidence of irregular heartbeats. Some types of irregular beats are associated with heart attacks.

Canadian researchers concluded that earlier studies may have been flawed because heart activity wasn’t tracked for long periods in which subjects simply went about routine living. Instead, reported the researchers in the journal Chest, previous indictments of coffee were based on heart evaluations in doctors’ offices that checked cardiac activity for periods averaging only 2 minutes.

Research subjects were given caffeine doses in a coffee-like drink prepared in the laboratory and tailored to their weights. An editorial published in the journal concluded the doses were roughly equivalent to 3 to 7 cups of coffee a day.

Despite earlier findings from both laboratory studies and evaluations of human subjects that linked coffee to heart rhythm irregularities and increased pulse rates, “presently available evidence suggests that moderate or even high dose caffeine does not cause any clinically important effects,” the researchers found.

Reacting in the editorial to the findings, Dr. Martin Myers of Sunnybrook Hospital in Toronto observed that the finding “should be welcome news for cardiac patients who enjoy a morning coffee, afternoon tea or occasional caffeine-containing soft drink.”