Research Magazine 2006

Study investigates hypertension in African Americans

blood pressure cuff

Kinesiology Assistant Professor David Keller is tracking a silent killer—high blood pressure. Often showing no symptoms, the condition can affect people for years without their knowledge.

In 2005 more than 70 million Americans were diagnosed with it, according to a study by the American Heart Association. The study showed that high blood pressure—also called hypertension—affected 31 percent of the African-American population compared to 21 percent of the white population, 20 percent of Hispanics, 19 percent of Asians, 22 percent of Pacific Islanders and 25 percent of American Indians.

Moreover, the study indicated that high blood pressure develops earlier in life in African Americans than in whites.

“It’s not entirely understood why that’s the case,” Dr. Keller says. “And not only are African Americans more likely to develop high blood pressure, they also get deadlier forms of it.”

These statistics convinced Keller to research blood pressure regulation in African Americans. Specifically, he is looking at blood pressure control mechanisms in African Americans who do not have hypertension and comparing them to mechanisms in African Americans who are pre-hypertensive.

In his lab, Keller investigates arterial baroreflex function at rest and during exercise. The arterial baroreflex is the primary short-term regulator of arterial blood pressure. This classic negative-feedback reflex continuously monitors the body’s blood pressure and initiates cardiovascular and neural responses that control it.

“The baroreflex is what keeps you from passing out every time you stand up,” he says. “It’s also crucial for keeping blood pressure from getting too high during exercise. Our body has a normal point that we operate around, and if our blood pressure falls too low or too high, this reflex kicks in to help bring blood pressure levels back to that normal point.”

What is not known, Keller says, is how the baroreflex works in African Americans. To investigate this, his study participants undergo baroreflex testing while measuring heart rate, blood pressure, blood flow and sympathetic nerve activity responses.

“By measuring all these variables concurrently, we can get a very integrated picture of how the baroreflex works on a neuro and cardiovascular level in African Americans,” he says.

The study, which began in fall 2008, is funded by grants from the National Institutes of Health and UT Arlington’s Research Enhancement Program.