Risk Factor for Stroke More Common Among Whites

May 15 -- WEDNESDAY, May 13 (HealthDay News) -- Whites are more likely than blacks to experience atrial fibrillation, a cause of stroke, even though blacks have a higher prevalence of risk factors such as high blood pressure, new research shows.

About 2.2 million Americans have atrial fibrillation, a heart arrhythmia in which the two upper chambers, or atria, quiver chaotically instead of beating in a normal rhythmic pattern, according to the Heart Rhythm Society.

The less effective pumping action can cause blood to pool and clot in the atria, raising the risk of stroke.

The study proves that race has a direct impact on the incidence of atrial fibrillation, the researchers said. They planned to present their findings Wednesday at the Heart Rhythm Society's annual meeting, in Boston.

Researchers examined data on nearly 200,000 patients who had at least two clinical visits to the Henry Ford Health System in Detroit during 2007. The study included 110,333 whites, 65,657 blacks and 20,114 patients whose race was undefined.

About 42 percent of blacks had hypertension, commonly called high blood pressure, compared to 29 percent of whites. Seventeen percent of blacks were diabetic, compared to 12 percent of whites.

Hypertension and diabetes are risk factors for atrial fibrillation, yet blacks had a 50 percent lower prevalence of atrial fibrillation. About 1.2 percent of blacks had atrial fibrillation, compared to 2.5 percent of whites.

"Our results confirm what previous, smaller studies have suggested about African Americans and a lower prevalence of AF [atrial fibrillation]," said study author Dr. Kan Fang. "What is truly fascinating about our findings is that African Americans can have significant risk factors for AF, even higher than those of Caucasian patients, yet have a lower occurrence."

Atrial fibrillation is one of the most common cardiac arrhythmias in the country. Risk factors include being male and/or older, hypertension, diabetes and cardiovascular disease.