“The key to wisdom is this – constant and frequent questioning, for by doubting we are led to question and by questioning we arrive at the truth.” – Peter Abelard
Jay Harold hopes everyone reads this important post about hypertension. Daniel T. Lackland’s “Racial Differences in Hypertension: Implications for High Blood Pressure1 ” reviews the data that lead to his conclusion. Black Americans have good reason to question this data because they have been abused in medical research. The Tuskegee Experiment2 is the most famous example.
The racial disparity in hypertension and hypertension-related outcomes has been recognized for decades with African Americans with greater risks than Caucasians. Blood pressure levels have consistently been higher for African Americans with an earlier onset of hypertension. While awareness and treatment levels of high blood pressure have been similar, racial differences in control rates are evident. The higher blood pressure levels for African Americans are associated with higher rates of stroke, end-stage renal disease, and congestive heart failure. The reasons for the racial disparities in elevated blood pressure and hypertension-related outcomes risk remain unclear. However, the implications of the disparities of hypertension for prevention and clinical management are substantial identifying African American men and women with excel hypertension risk and warranting interventions focused on these differences. In addition, focused research to identify the factors attributed to these disparities in risk burden is an essential need to address the evidence gaps.
The racial disparities in hypertension and hypertension-related disease outcomes have been related mortality(death), and morbidity (sickness) risks compared with their white counterparts. These excess risks from elevated blood pressure have a dramatic effect on life expectancy for African-American men and women which is significantly less than for Caucasian Americans. Stroke mortality risks are two-fold greater for African Americans.1 End-stage renal disease is five times more common for African-American men and women. In addition, the age of onset of diseases such as stroke is considerably earlier for African Americans. For example, a 45-year-old African-American man residing in the Southeast has the stroke risk of a 55-year-old white man in the Southeast and a 65-year-old white man residing in the Midwest.1 While high blood pressure affects all segments of the population, high blood pressure rates are more prevalent among African-American men and women.2
The increased prevalence and relative risks constitute significant population attributable risks.3 Specifically, the population attributable risk for hypertension and 30-year mortality among white men was 23.8% compared with 45.2% among black men and 18.3% for white women compared with 39.5% for black women. These excess disease risks have been long recognized and reported from the Evans County Heart Study4 and the Charleston Heart Study5 which were both initiated in 1960 specifically to study these racial disparities in cardiovascular disease in adults. Similarly, the Bogalusa Heart Study6 assessed the racial differences in children and young adults. More recently, the Jackson Heart Study 7 has been established to assess cardiovascular risk factors in this population. Further, the REasons for Geographic And Racial Differences in Stroke (REGARDS) study has further documented and confirmed the racial and geographic differences in awareness, treatment, and control of hypertension.8.With these large epidemiology studies, high blood pressure has been a common significant factor associated with the excess disease burden for African Americans.9
Blood Pressure and Hypertension Levels
Nearly one-third of the adult population in the United States are considered to have hypertension with elevated blood pressure (>= 140/90 mmHg) and/or being treated with antihypertensive medication. The prevalence of hypertension is higher in both middle-aged and older African Americans compared with non-Hispanic whites.10,11 As presented in Figure 1, data from the National Health and Nutrition Examination Survey (NHANES), show the racial disparities with black men and women having significantly higher rates of hypertension than white men and women.12 ,13 The prevalence rates increased for all four race-sex groups from 1988 –1994 period to 2009-2010. However, the racial disparities in hypertension prevalence remained consistent over the time periods. These racial differences are evidence at all ages. Blacks are found to develop hypertension at an earlier age than whites. An assessment of US children aged 8–17 years found systolic blood pressures to be 2.9 mmHg and 1.6 mmHg higher in black boys and girls compared with age-matched white boys and girls.14 With the consistent racial differences at all ages it is evidence disparities in hypertension represent a lifetime consideration.,15,16,17
Hypertension Treatment and Control
While large-scale clinical trials have consistently demonstrated that the control of elevated blood pressure significantly reduces the risk for major cardiovascular disease, stroke and end-stage renal disease outcomes, a substantial portion of hypertensive patients do not achieve blood pressure control.15 Data from the National Health and Examination Survey suggest that blood pressure is controlled for less than two-thirds of all patients on antihypertensive medications. 12,18 African Americans demonstrated poorer blood pressure control compared with Caucasians.
Figure 2 presents the hypertension control rates for all four race-sex groups from 1988 to 2010. While the high blood pressure control rates improved from the 1988-1994 period to the 2009-2010 period for all four race-sex groups, the racial disparities remained consistent. These findings of disparities in hypertension control are consistent with other studies.8,11,12,19–21The racial differences in control rates cannot be attributed to differences in rates of awareness and treatment.8,9,11,12,15,18,21,22
Rates of awareness of hypertension as well as treatment patterns of antihypertensive therapy are similar for both race groups and even better among black men and women compared to white men and women. Likewise, treatment with non-pharmacological therapy does not explain the racial disparities in hypertension control. Results from clinical trials have included race in results with suggested treatment effects for the various racial groups. Dietary factors including sodium and potassium, while different for blacks and whites, do not explain the racial disparities in hypertension. The Dietary Approaches to Stop Hypertension (DASH) diet with sodium restriction found better BP reduction for African Americans than Caucasians, indicating that black individuals may respond differently than whites.23,24 Similarly, treatment of elevated blood pressure with antihypertensive medications and different medications may produce different effects in African Americans and whites. Calcium channel blockers and diuretics have been proposed as being particularly effective for African Americans with hypertension.25–27Angiotensin-converting enzyme (ACE) inhibitors, and angiotensin receptor blockers (ARBs) have not been shown to be as effective in black populations compared with white populations.26–28 Similarly, ACE inhibitors, ARBs, and β blockers have been reported to be less effective in blacks with heart failure compared with white patients.29 However, it is important to consider sample size and confounders as well as study design when interpreting these results.