Using data from a massive, four-year study, researchers have found that whites have a greater risk of developing atrial fibrillation, or an irregular heartbeat, than people of other races.
The findings by doctors at the University of California, San Francisco (UCSF), published online today in the journal Circulation, offer a starting point for new research into the causes of the most common type of irregular heartbeat. Although people over the age of 40 have a 26 percent lifetime risk of developing atrial fibrillation, according to the Framingham Heart Study, little is known about it.
The UCSF researchers mined the records of 14 million California patients who visited the emergency room, had outpatient services, or were hospitalized between 2005 and 2009. The patient sample included whites, blacks, Hispanics, and Asians.
In comparison to whites, blacks had a 16 percent lower risk of developing atrial fibrillation, while Hispanics and Asians had a 22 percent lower risk.
Why Are Europeans at Greater Risk?
For many years, researchers have been puzzled by the fact that blacks have a higher risk of developing heart-related problems, such as high blood pressure and diabetes, but do not develop atrial fibrillation as often as whites. This has led some to speculate that blacks may have a gene that protects them from the condition, while others have suspected that whites have a genetic predisposition to greater risk.
“Once you start looking at risk factors such as getting older, high blood pressure, heart failure, and diabetes, there is a very consistent finding that we thought was very interesting,” Dr. Gregory Marcus, the lead study author, told Healthline. “When you look at those risk factors, the difference in risk by race diminishes. In the absence of them, the difference by race is enhanced, which implies that the racial difference may be due to a kind of atrial fibrillation that is independent... of those risk factors.”
Over the years, Marcus explained, research has allowed our perception of conditions and their variations to change. For example, people once thought of cancer as just that: cancer. But now, we know that leukemia, for example, is very different from breast cancer. So, perhaps, the atrial fibrillation that tends to affect whites is somehow different from the kind that afflicts people of other races.
“Or, maybe more exciting, maybe it's from some environmental exposure. Have whites taken on some sort of behavior? Are they drinking more red wine, for example?” Marcus said. “Most genetic studies have been done only on whites, so part of the problem is, because it's within whites, it's hard to figure out what about being white increases risk.”
Marcus suggested that there might also be a gene or set of genes in whites related to European ancestry that raises their risk. Among blacks, those with European ancestry are at higher risk of atrial fibrillation, Marcus said. He is currently doing research among people with genes from different races, but added that large-scale studies are needed.
Currently, there is no preventive strategy for atrial fibrillation, Marcus said, despite the fact it can cause stroke or even death. “There is no way to predict who's going to get it," he said. "There is no one marker.”