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MILWAUKEE - About 25 percent of Americans age 40 and older eventually will develop an irregular heartbeat known as atrial fibrillation, a new study has found.
Atrial fibrillation, the most common arrhythmia, affects about 2.2 million people, a number that is expected to grow as Americans get older.
The new study, published in Circulation: Journal of the American Heart Association, is the first to estimate the lifetime risk of developing the condition, said lead author Donald Lloyd-Jones, an assistant professor of medicine and preventive medicine at the Northwestern University Feinberg School of Medicine.
The researchers used data from 8,700 men and women who took part in the Framingham Heart Study in 1968-99 to estimate the lifetime risk.
They found that a 40-year-old man has a 26 percent lifetime risk of developing atrial fibrillation. For women, the risk is 23 percent.
"We were quite surprised they were this high," Lloyd-Jones said.
Atrial fibrillation is a condition in which the two upper chambers of the heart, called the atria, quiver or fibrillate, instead of beating normally.
That results in blood that is not completely pumped out of the chambers, which can cause it to pool and clot.
Because those clots can travel to the brain, people with the condition are at higher risk of having a stroke. It is estimated that 15 percent to 20 percent of strokes are the result of atrial fibrillation.
Marilyn Ezri, an associate professor of medicine at the Medical College of Wisconsin, said the study's findings were surprising.
"They were much higher than I would have guessed," said Ezri, a cardiologist and electrophysiologist at Froedtert Memorial Lutheran Hospital in Wauwatosa. "I think this is a huge public health issue."
Even after separating out people with conditions such as congestive heart failure and previous heart attacks, she said, the lifetime risk still is one in six. "That's substantially higher than breast cancer."
Risk factors for atrial fibrillation include age, high blood pressure and heart disease.
Common symptoms include a fluttering feeling in the chest, fatigue, dizziness and difficulty sleeping.
Some people are asymptomatic, while others may be bothered by the condition on a regular basis.
Often drugs can control the condition, but they have side effects and, for some, medications do not work. At least two catheter-based surgical treatments also are available.
Lloyd-Jones said the new research underscores the importance of being checked for the condition.
Symptoms sometimes are hard to detect, but an indication of the condition is palpitations or a feeling that the heart has skipped a beat or is beating irregularly. Unusual shortness of breath with exertion also may be a sign.
The most accurate way to check for the condition is with an electrocardiogram, he said. But a basic check can be done by monitoring a person's pulse for an unsteady beat.
Lloyd-Jones noted that the heart association recommends that adults have their pulse checked by a doctor for irregularities at least every two years as well as at every doctor's visit.
"We have effective medications for reducing the risk of stroke in atrial fibrillation, but if AF goes undiagnosed, we can't protect people from the potential complications."
The study was funded by the National Heart, Lung and Blood Institute, part of the National Institutes of Health.
Other researchers in the study were from Boston University School of Medicine, Massachusetts General Hospital in Boston and Harvard Medical School.
(c) 2004, Milwaukee Journal Sentinel. Distributed by Knight Ridder/Tribune News Service.