Mystery of Racial Differences in Health Risks

Atrial fibrillation risks lower for blacks for unknown reasons

(RxWiki News) African Americans have a greater risk of hypertension and diabetes. But for unknown reasons, they are less likely to have an irregular heart beat.

Atrial fibrillation is the most common diagnosis for an abnormal heartbeat. It affects about 2 million people in the US, and having atrial fibrillation puts people at risk for stroke and death. 

A recent study looked at risk factors for atrial fibrillation in older African Americans and whites. None of the risk factors explained why African Americans had lower rates of atrial fibrillation.

"See a doctor regularly to keep track of your heart health."

Paul Jensen, MPH, of the Department of Cardiovascular Health Research Unit at the University of Washington in Seattle, and colleagues led the study to determine what factors could explain the lower rate of atrial fibrillation among African Americans.

A total of 4,774 whites and 911 African Americans participated in the study. The participants were 65 or older and did not have a history of atrial fibrillation when the study started.

Information was collected from the participants through interviews and physical examinations. Results from their annual electrocardiogram tests were also collected. This test measures the heart's electrical activity.

The study followed the participants on average for a little over 11 years. A total of 1,403 white and 182 African American participants developed atrial fibrillation. The risk of developing atrial fibrillation was 25 percent lower for African Americans after accounting for age and sex.

Risk factors for atrial fibrillation were similar for whites and African Americans, except for one. African Americans risk for atrial fibrillation was associated with increases in left ventricular posterior wall thickness.

The left ventricle of the heart pumps blood to the aorta. The aorta gets the blood to the rest of the body. The posterior wall is part of the ventricle's muscle that does the pumping. The thickness of the wall can affect the muscles ability to pump.

The study authors commented that further research is needed to understand the racial differences in atrial fibrillation. The study did not suggest any explanation for the lower rate of atrial fibrillation among African Americans.

The study had some limitations. Atrial fibrillation can often come and go. Detecting it with only an annual electrocardiogram could be difficult. Atrial fibrillation can also have no symptoms and therefore the patient might not seek treatment. 

This study, titled "Racial Differences in the Incidence of and Risk Factors for Atrial Fibrillation in Older Adults: The Cardiovascular Health Study," was published by the Journal of American Geriatric Society. It was funded by the National Heart, Lung and Blood Institute, the National Institute of Neurological Disorders and Stroke and the National Institute on Aging. Dr. Jensen and co-authors disclosed no conflict of interest.

Review Date: 
January 22, 2013