HYPERTENSION IN AFRICAN AMERICANS: TARGETING PREVENTION

Development of disease is an area in which each societal group is disadvantaged in one way or another.  Practically every group has a tendency to develop one or more afflictions at a higher rate than the general population.  For the African American community, one particular problem is hypertension.

The existing data show that hypertension is more common in African Americans and is more aggressive and less well managed in African Americans than in whites.  African Americans also have higher rates of morbidity and mortality from disease related to high blood pressure, such as stroke and renal failure.  The natural nocturnal fall in blood pressure is less pronounced in African Americans, and their systolic blood pressure while awake is higher than in people of other races.

The exact causes of these differences have not been pinpointed, but research seems to be focused in two general areas.

Some research suggest that certain physical and genetic factors contribute to increased incidence of hypertension in African Americans, whereas other studies have shown that hypertension in African Americans is related to environmental stress.  This debate involve not just medical data but socioeconomic factors as well.  In short, it is a nature vs. nurture debate, and there are supporting data for both arguments.

Nature vs. Nurture

Studies have shown that environmental stress may contribute to increased hypertension in African Americans.  A study conducted by Dr. Norman Anderson of Duke University shows that chronic stress may lead to an increase in the release of the hormone norepineohrine reduces the amount of salt eliminated from the kidneys, and the resulting increase in blood salt content can lead to increased blood pressure.  This chain reaction has been shown to occur in animal studies.  The high rate of chronic exposure to stress in many African American communities has been well documented.  If these studies hold true for humans, it would lend credence to the idea that certain stressful factors found in some African American communities could cause hypertension.  Stressors such as poverty, unemployment, the threat of violence, and racial discrimination could be shown to cause kidneys to reduce elimination of salt and thus may also increase the risk of hypertension.

Anger in response to racism may be a significant contributing factor in increased hypertension in African Americans.  A study conducted jointly at the University of Tennessee and Saint Louis University showed that blood pressure in African Americans increased significantly when they were shown film clips of racially motivated violence.  The responses of African Americans to these scenes of racial discrimination were more pronounced than their responses to viewing scenes that were anger-provoking but had no racial component.  The increases in blood pressure were not into the hypertension range, but researchers believe that over time, such continued elevation of blood pressure could become dangerous.

Such conclusion seem to suggest that socioeconomic factors are the main cause of hypertension among African Americans.  A study performed on twenty-six African Americans women on strict low-fat diets seems to support this.  The data showed that women of higher socioeconomic status had more excretion of salt than those of lower status.  Since proportionately more African Americans are in lower socioeconomic classes than whites, increased stress from lower status could be the main factor behind the inflated rate of hypertension among the African American population.

But is it all due to environment?  Perhaps not.  Other groups of traditionally lower socioeconomic status, such as Hispanics, Asians, and Native Americans, have been found to have the same incidence of hypertension as whites.  African American children have been found to have higher blood pressure in general than white children; it is not known whether stress plays a significant role in affecting the blood pressure of these children so early in life.

There is also evidence that African Americans may be predisposed to hypertension at the cellular level.  Microscopic studies of blood vessels in African Americans with severe hypertension revealed that reduced renal arterioles were thickened and had reduced flow.  This thickening, not found in the renal arterioles of hypertensive whites, was caused by hypertrophy (excess growth) of smooth muscle cells in the muscle walls of the arterioles.  This thickening reduced the size of the lumen (inside opening) of the vessels, and the resulting reduced blood flow, may have caused increased blood pressure.  The smooth muscle cells were thought to be responding abnormally to growth factors, which caused the hypertrophy to occur.  The reason behind this abnormal reaction was not determined, however.

The best explanation of why African Americans are more prone to develop hypertension may not involve environmental or genetics alone, but a combination of the two.  Stress factors unique to the African American community may serve to aggravate or intensify an existing physical predisposition toward hypertension.  It has already been shown that the tendency toward developing hypertension can be passed from parents to their children.  Add several unique stress factors to a population already predisposed to high blood pressure, and the potential exists for high numbers of people to develop hypertension.  Commenting on the UT-SLU study, Dr. Elijah Saunders agreed that “racism and Black rage are emotional stressors that could worsen a physiological tendency toward hypertension.

Treatment for Hypertension in African Americans

The good news is that African Americans respond to medical treatment in similar manner to whites.  The treatment regimen for African Americans may have to be altered somewhat, however, since they do not respond as well to some hypertension medications as people of other races.  For unknown reasons, drugs such as beta blockers and ACE (angiotensin converting enzyme) inhibitors do not work as well in African Americans and may need to be supplemented by other medications, such as diuretics.

Lifestyle changes may also be needed and may be a more effective tool in lowering blood pressure in African Americans than in people of other races.  Effort should be made to exercise and lose weight if needed, since excess weight can be a contributing factor in hypertension.  Hypertensive African Americans tend to have lower intakes of potassium and calcium, so diet changes should be made that ensure that these minerals are in adequate supply.  A reduction in sodium may also be desirable, since research suggests that African Americans may be more sensitive to the effects of sodium on the cardiovascular system.

Although African Americans are more likely to develop high blood pressure, prevention and treatment can help keep hypertension from becoming a deadly affliction.  Proper diagnosis is more essential, so people at risk should see their doctors to determine whether they have hypertension or are at risk for developing it.  Through recommending lifestyle modifications, prescribing medications, or both, a physician can help manage this condition or help prevent its onset.

For Discussion

Do you feel that people in lower (or higher) socioeconomic groups suffer more from everyday stress? Do you believe physiological or genetic differences may exist between different ethnic or racial groups?