The African Gene? Searching through History for the Roots of Black Hypertension
Fackelmann, Kathy A., Science News
When Byllye Avery took the microphone last month at a meeting in Washington, D.C., the statistics on hypertension suddenly coalesced into a painful reality faced by one black American family.
"Twenty-one years ago, my husband died of a massive heart attack," she said in a soft, determined voice. "He was 33 years old. He was hypertensive and we didn't know it."
Avery, founding president of the National Black Women's Health Project in Atlanta, recounted her experience at a Sept. 19 editors' seminar on cardiovascular disease in black Americans, organized by the Dallas-based American Heart Association (AHA).
Blacks in the United States run a hypertension risk twice as great as that of Caucasians, but scientists still don't know why. One controversial hypothesis, proposed in 1988 by hypertension research Clarence E. Grim, traces the disparity back to the 16th century, when European slave traders began shipping captured Africans to plantations in the New World. According to this scenario, blacks living in the United States today may owe their high hypertension rate to a genetic trait that helped their ancestors survive the grueling conditions of slavery. That trait is an inherited tendency to conserve salt within the body, says Grim, director of the Drew/UCLA Hypertension Research Center at the Charles R. Drew University of Medicine and Science in Los Angeles.
Now Grim reports new research findings that strengthen the slavery hypothesis. His results, which remain controversial and unconfirmed, hint that physicians might one day be able to use genetic testing to identify blacks, and perhaps others, with a particularly high risk of hypertension, so that preventive measures can begin at an early age. Grim presented the new findings at the AHA's 45th annual scientific sessions on high blood pressure, held in Chicago the week after the Washington meeting.
U.S. blacks afflicted with hypertension run a greater risk of its life-threatening complications than whites. Elevated blood pressure puts extra strain on blood vessels and can damage the vessel walls, increasing the risk of stroke if a clot blocks the brain's blood supply. And, if left untreated, years of high blood pressure can inexorably damage the heart and kidneys, raising the very real possibility that these crucial organs will fail. Among hypertensives in the United States, blacks are 10 to 18 times more likely than whites to suffer kidney failure, and three to five times more likely to develop chronic heart failure, notes Edward S. Cooper of the University of Pennsylvania in Philadelphia, who spoke at the Washington conference.
High blood pressure is defined as systolic (heart-pumping) pressure of at least 140 millimeters of mercury (mm Hg) and diastolic (heart-resting) pressure of at least 90 mm Hg. Several factors can boost a person's risk of developing the condition, including stress, advancing age, obesity, lack of exercise, alcohol use, salty diet and family history of hypertension. But in nine out of 10 cases, physicians cannot pinpoint the cause. And scientists can only speculate about what makes black Americans particularly vulnerable to this potentially deadly condition.
Some researchers have suggested that socio-economic differences may underlie the chronically elevated pressures that predispose U.S. blacks to hypertension (SN: 2/16/91, p.111). For one thing, they note, the high cost of medical care and lack of insurance can prevent low-income patients from getting regular examinations or treatment. In addition, the stress of poverty or racism may evoke a hormonal "fight or flight" response that boosts heart rate and blood pressure, says Curtis G. Hames of the Medical College of Georgia in Augusta. In earlier times, these metabolic changes helped people escape physical danger, Hames says, but today's artery-pounding pressures may spring instead from inescapable stresses of modern life. …