Framingham Heart Study data show that a person’s risk for developing atrial fibrillation is doubled when at least one parent is affected, according to an article in the June 16th issue of the Journal of the American Medical Association. The analysis, which represented 2,243 adults, is the first to find a genetic connection for the dysrhythmia in a community sample.

"This important research finding will need to be confirmed but it opens up a new avenue of research on atrial fibrillation. Now scientists can start looking at genetic factors that might contribute to atrial fibrillation - searching for the genes involved in this increasingly common disorder," said Barbara Alving, MD, of the National Institutes of Health.

The study's findings strongly support the notion that atrial fibrillation has genetic underpinnings. Most cases occur in older people, affecting about 1 in every 10 persons aged 80 years and over. In the new study, the risk tripled when both parents and the adult child were under age 75 years. The risk also tripled when the analysis was limited to adult children who had no clinically apparent heart disease.

"Disorders with a genetic component often occur at a younger age or in the absence of major diseases like heart disease that trigger the condition," said the study's lead investigator and author Caroline Fox, MD, MPH.

Atrial fibrillation is the most common heart rhythm disorder in the U.S., affecting more than 2 million adults. The prevalence is rising and scientists predict that about 5.6 million Americans will have the disorder by 2050. Known causes include abnormalities in the heart's structure and long-term uncontrolled hypertension.

The Framingham Offspring study involved 1165 women and 1078 men whose parents were members of the "original" Framingham Heart Study. The adults were at least 30 years of age and free of atrial fibrillation at the first exam. Both adult children and original study participants had routine clinic exams including physical examinations, interviews, lab tests, and electrocardiograms.

When researchers analyzed the data, they found that 30 percent of participants had at least one affected parent. Seventy adult children (47 men, 23 women) developed the dysrhythmia during the study (mean age, 62 years). When stated in terms of 1000 persons per year, the number of children developing atrial fibrillation would be 4.5 if a parent was affected and 3 if parents were not affected.

Fox cautioned that the Framingham findings should not alarm people who have a parent with atrial fibrillation. "Atrial fibrillation with or without a family history is a common condition in the elderly. Our findings indicate to the scientific community that we need more research on the genetic mechanisms of atrial fibrillation and how they interact with environmental influences," she said.

Study limitations, noted Fox, include the small number of offspring cases and a predominantly Caucasian group of participants.