January/February 2021

Hypertension in Black Americans
By Jamie Santa Cruz
Today’s Geriatric Medicine
Vol. 14 No. 1 P. 10

Why is the prevalence so high and what can physicians do?

Hypertension is prevalent among Black Americans, affecting approximately 4 in 10 non-Hispanic Black adults. This is a significantly higher incidence than that seen among other racial and ethnic groups: Only 27.8% of Hispanic adults and non-Hispanic white adults have hypertension.1

This racial disparity has been evident for decades, but its causes are complex, and it’s proven difficult to eradicate.

How Stark Are the Racial Inequities?
The disparity is not simply in the fact that Black individuals are more likely to be hypertensive than other groups. Among individuals with hypertension, Black individuals are also less likely to have their blood pressure controlled; approximately 48% of non-Hispanic white adults with high blood pressure have controlled hypertension, whereas only 41.5% of Black adults with high blood pressure have controlled hypertension.2 These disparities in hypertension control remain, even though research has found that Black patients with hypertension are treated more intensively on average than are white patients.3

There are also significant inequities in hypertension-related mortality. A 2020 report found that Black individuals are nearly twice as likely to die from hypertension-related heart disease than are their white peers. Whereas the mortality rate is just 117.2 per 100,000 people for white men, it is 206.6 per 100,000 for Black men.4

According to Sadiya Khan, MD, MSc, an assistant professor of medicine at the Feinberg School of Medicine at Northwestern University and one of the coauthors of the report, the study covered a period of close to two decades (up to the year 2018), and the disparities in mortality by race held steady throughout that time. “It was pretty similar across the study period,” Khan says. “That’s one of the things that was concerning. We haven’t made any progress in these disparities.”

The disparity in mortality rates certainly is related in part to the higher incidence of hypertension among Black individuals, but simple differences in hypertension prevalence don’t appear to explain all of the increased mortality among Black individuals. Even among subjects who all have hypertension, it appears that Black individuals are at greater risk of stroke and mortality than are white individuals.5

What Lies Behind the Disparities?
The causes of the racial disparities in hypertension are multifactorial, and the relative significance of various contributing factors is debated. However, there’s evidence that all of the following factors play a causal role:

• Traditional risk factors: Black individuals are more likely than white individuals to have several of the traditional risk factors for hypertension, including obesity, diabetes, and physical inactivity.6-8

• Social determinants of health: Although traditional risk factors explain much of the disparity in hypertension prevalence, many researchers are increasingly pointing to social determinants—that is, the conditions in which people are born, grow, work, live, and age9—as the underlying causes of many of those risk factors and of hypertension itself.

 “Let’s take economic instability,” says Yvonne Commodore-Mensah, PhD, MHS, RN, an assistant professor in the Johns Hopkins School of Nursing. “In the US, insurance is often tied to employment,” so those who lack insurance through an employer may not be able to access needed health care. In addition, she says, “lower-income populations have challenges accessing heart-healthy foods, which is required to manage hypertension.”

The neighborhood context and physical environment can also contribute to the excessive burden of hypertension in Blacks.10 “Blacks are more likely to live in racially segregated neighborhoods that are often unsafe and they are not walkable,” Commodore-Mensah says. “Physical activity is one of the recommendations that is made to manage hypertension11, [but] if your neighborhood is unsafe, it’s not walkable, you’re not going to maintain the recommended level of physical activity.”

Educational attainment and racial discrimination are additional social determinants of health that may disproportionately affect Black patients. Low educational attainment is linked to a higher burden of hypertension,10 as is self-reported racial discrimination.12

Some of the above-mentioned social determinants could influence health and hypertension risk directly. However, there’s also concern that they could also influence hypertension by contributing to a higher burden of stress,13 which has a pervasive effect on a range of physiological systems and is increasingly linked to cardiovascular disease, including hypertension. Some research has suggested that Black individuals are at greater risk of chronic toxic stress than are white individuals.14

• Structural racism: Social determinants of health stem in many cases from upstream structural factors (such as public and social policy) that perpetuate disparities in health outcomes. One of the key structural factors impacting social determinants of health is housing segregation.15 Housing segregation by race was established in the United States through a combination of both federal and private policies beginning in the 1940s that related to racially discriminatory zoning, mortgage discrimination, restrictive covenants, and other factors. Although housing discrimination has been illegal since the Fair Housing Act of 1968, the segregation established by previous policy has remained largely in place.

Epidemiological studies provide consistent evidence that segregation is linked to poorer health.15 According to Andrea Westby, MD, an assistant professor in the department of family medicine and community health at the University of Minnesota Medical School, it’s not difficult to understand why.

“Predominantly Black neighborhoods are more likely to have environmental toxins—they’re more likely to have air toxins, water toxins, substandard and poor-quality housing.16 They’re less likely to have adequate green spaces, which […] independently affects health, stress, blood pressure, [and] cardiac risk,” Westby says, adding that the majority of Black neighborhoods tend to be underresourced in terms of access to fresh food and good-quality health care facilities compared to white neighborhoods. “Access to all of those things has been stratified by race because of the ways that residential racial segregation has led to the resourcing of neighborhoods.”

• Genetic factors: Several genetic factors can predispose individuals to salt retention, which is thought to increase the risk of hypertension. In particular, Black individuals with hypertension are significantly more likely than white counterparts to have low-renin hypertension due to salt and water retention, with either a Liddle phenotype (low renin/low aldosterone) or a phenotype of primary aldosteronism.

The Liddle phenotype, which can be caused by variants of six different genes, is characterized by suppression of both renin and aldosterone as a result of overactivity of the renal tubular epithelial sodium channel. The primary aldosteronism phenotype (low renin/high aldosterone), also driven by variants in six genes, is usually the result of bilateral adrenocortical hyperplasia.17 Genetic factors such as these are thought to account in part for the high rates of resistant hypertension in individuals who have these variants.

• Adherence to treatment: Multiple studies have found that Black individuals have lower adherence to prescribed hypertension treatment than that of white individuals. Lack of treatment adherence does not explain why Black individuals have higher rates of hypertension in the first place, but it may in part account for the fact that Black individuals tend to have hypertension that’s less well controlled than white counterparts.

Some studies suggest that lack of insurance (which disproportionately affects Black patients) is a key barrier to medication adherence.18 However, other research has found lower adherence among Black patients even in health care systems of the VA, where access to care is typically equal regardless of ability to pay.

Other common patient-side barriers for Black patients include lack of self-efficacy and depression, while a key barrier on the provider side is lack of collaborative provider-patient communication.19

Should Race Factor Into Treatment Decisions?
In 2014, the clinical practice guideline of the Eighth Joint National Committee introduced race into its algorithm for making treatment decisions for hypertension—the first time race had been incorporated into the algorithm of such a guideline.20 For Black patients, the guideline recommends only two first-line treatment options: either a thiazide diuretic or calcium channel blocker. For white patients, by contrast, the guideline indicates that angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers can also be used as first-line treatments.

The use of race in the algorithm—and the use of race in general as a biological proxy—has caused controversy. According to Commodore-Mensah, the guideline reflects the fact diuretics and calcium-channel blockers have been shown in clinical trials to work well for Black patients due to what’s known about the biology of hypertension in the Black population. “The fact that we know Blacks are more likely to have salt sensitivity, that influences the choice of medications,” she says.

At the same time, she acknowledges that “in a lot of these trials that have tested the efficacy of different types of medications, there hasn’t been adequate representation of Blacks. So what we know about which treatments work effectively in Blacks is based on a limited number of clinical trials.”

In addition to concern about the insufficient inclusion of Black subjects in clinical trials, there’s also the concern that race is merely a social construct rather than a biological indicator. How should mixed-race patients be classified, for example—should they be treated as white or Black? Even if a patient clearly has dark skin, that’s not actually a good reflector of genes, Westby says.

“In the US, a lot of our multigenerational African Americans are from West Africa originally because of the trans-Atlantic slave trade, but not everyone. There is more human genetic variation within the continent of Africa than between populations from other continents. So when we look at patients from North Africa and South Africa, they have very different genotypes than [people from] mid-West Africa,” she says.

In the end, skin color is a poor way to establish biology. “There are probably plenty of people who look white who have that same amount of genetic ancestry from Africa,” Westby says.

Based on her reading of the studies used in the Joint National Committee recommendation, Westby isn’t convinced that ACE inhibitors aren’t useful for Black patients, and she’s concerned about the potential harm to individual Black patients who won’t receive a prescription simply because of their skin color.

“The blood pressure medication that they recommend avoiding in African American and Black patients [that is, ACE inhibitors]—I believe there are potentially beneficial effects on the kidneys with use of that medication. And if we limit and don’t give that medication to appropriate patients just because they phenotypically look Black, I think we are doing people a disservice,” she says.

David Spence, MD, MBA, FRCPC, FAHA, FCAHS, a professor of neurology and clinical pharmacology at Western University in Ontario, Canada, whose research on hypertension has focused on genetic contributors, also shies away from a race-based algorithm. He prefers a more individualized approach based on understanding of the actual biology behind the patient’s hypertension.17

Phenotype matters greatly in determining the appropriate treatment, argues Spence, who is concerned that many Black patients have uncontrolled hypertension because their phenotype isn’t understood. “If the problem is excess production of aldosterone, then the treatment is […] aldosterone antagonists,” he says. “But the specific treatment for Liddle syndrome and the Liddle phenotype is a medication called amiloride, which is almost never used. I think it’s perhaps the most neglected feature of blood pressure treatment.”

In turn, for patients with a renal phenotype (high renin with secondary hyperaldosteronism), the best treatment is angiotensin receptor blockers or renin inhibitors, according to Spence.

Takeaways for Providers
The causes of hypertension related to racial disparities are complicated and cannot be solved in the exam room alone. Still, clinicians can help address the problem with the following steps:

• Understand various hypertension phenotypes and how they should be treated differently. Spence recommends offering usual care for any patient who presents with only moderately high blood pressure, but if a patient comes to his office with extremely high blood pressure, he evaluates their renin and aldosterone right away—regardless of their race. The same goes for any patient with resistant hypertension.

“When someone has high blood pressure that’s not controlled by usual therapy, [providers] should say to themselves, ‘Why is this patient different? What is different about this patient that is causing him or her to be resistant to usual therapy?’” he says. “When that question comes up, providers should be doing the plasma renin and aldosterone to figure out the cause of the hypertension and then know how to treat it.”

A trial in Africa reported a marked improvement in blood pressure control using this algorithm.21

• Establish collaborative communication. As noted previously, provider-patient communication affects medication adherence, which likely explains part of why Black patients are less likely to achieve hypertension control. Thus, according to Khan, providers should ensure there is “ample time spent on explaining and understanding why blood pressure is being treated, why blood pressure is important, and understanding concerns related to medications, so that there is a meeting of the minds and a shared understanding of how to manage blood pressure together.”

• Prescribe single-pill combination therapies. Given the high rates of resistant hypertension among Black patients, many will need more than one medication. According to Commodore-Mensah, providers can improve medication adherence by providing single-pill combination pills.

• Assess social determinants, then refer to social services to help address issues the patient may be facing. Given that social determinants influence hypertension, providers need to know their patients’ socioeconomic and educational status, as well as cultural, work, and home environments. “It’s not enough to say, you need to follow the DASH [Dietary Approaches to Stop Hypertension] diet, eat five servings of fruits and vegetables a day, and not ask the patient, ‘Do you have enough food?’” Commodore-Mensah says. “We don’t acknowledge the realities that patients are living in. We also lose credibility, because people are dealing with some difficult issues in their home environment and their social context. We need to acknowledge these issues and bring them to the fore”—and then refer patients to social services who can help.

Of course, time constraints are always an issue, but if providers aren’t able to ask patients about social determinants themselves, Commodore-Mensah encourages providers to recruit other members of their teams to fill that role.

• Encourage patients to come back if treatment isn’t working. According to Commodore-Mensah, providers should recommend home blood pressure monitors to patients who are having difficulty controlling their hypertension. But recommending the monitors isn’t enough: “If [their blood pressure is] consistently elevated and they are being adherent to therapy, we also need to teach patients how to reach out to their providers and communicate freely so that therapy can be adjusted.”

That being the case, it’s important to make sure patients feel comfortable talking to their providers.

• Look beyond the exam room and work to dismantle social structures that perpetuate racial disparities. Physicians can only do so much in their individual interactions with patients, Westby says. “We’re also going to need to move beyond that and think about what are the systems and structures in place that continue to put our particular patient as well as the whole community of folks who have been impacted by racism at risk of those increased exposures, increased stress, and residential segregation, and how do we think about mitigating that even beyond the exam room,” she says.

— Jamie Santa Cruz is a health and medical writer in the greater Denver area.

References
1. Fryar CD, Ostchega Y, Hales CM, Zhang G, Kruszon-Moran D; Centers for Disease Control and Prevention, National Center for Health Statistics. Hypertension prevalence and control among adults: United States, 2015–2016. https://www.cdc.gov/nchs/data/databriefs/db289.pdf. Published October 2017.

2. Muntner P, Hardy ST, Fine LJ, et al. Trends in blood pressure control among US adults with hypertension, 1999-2000 to 2017-2018. JAMA. 2020;324(12):1190-1200.

3. Howard G, Prineas R, Moy C, et al. Racial and geographic differences in awareness, treatment, and control of hypertension: the REasons for Geographic And Racial Differences in Stroke study. Stroke. 2006;37(5):1171-1178.

4. Rethy L, Shah NS, Paparello JJ, Lloyd-Jones DM, Khan SS. Trends in hypertension-related cardiovascular mortality in the United States, 2000 to 2018. Hypertension. 2020;76(3):e23-e25.

5. Howard G, Lackland DT, Kleindorfer DO, et al. Racial differences in the impact of elevated systolic blood pressure on stroke risk. JAMA Intern Med. 2013;173(1):46-51.

6. Hales CM, Carroll MD, Fryar CD, Ogden CL; Centers for Disease Control and Prevention, National Center for Health Statistics. Prevalence of obesity and severe obesity among adults: United States, 2017–2018. https://www.cdc.gov/nchs/data/databriefs/db360-h.pdf. Published February 2020.

7. Centers for Disease Control and Prevention. National Diabetes Statistics Report, 2020: estimates of diabetes and its burden in the United States. https://www.cdc.gov/diabetes/pdfs/data/statistics/national-diabetes-statistics-report.Pdf.

8. Adult physical inactivity prevalence maps by race/ethnicity. Centers for Disease Control and Prevention website. https://www.cdc.gov/physicalactivity/data/inactivity-prevalence-maps/index.html. Updated January 16, 2020. Accessed September 24, 2020.

9. Social determinants of health. World Health Organization website. https://www.who.int/social_determinants/sdh_definition/en/. Accessed September 25, 2020.

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12. Dolezsar CM, McGrath JJ, Herzig AJM, Miller SB. Perceived racial discrimination and hypertension: a comprehensive systematic review. Health Psychol. 2014;33(1):20-34.

13. Warnecke RB, Oh A, Breen N, et al. Approaching health disparities from a population perspective: the National Institutes of Health Centers for Population Health and Health Disparities. Am J Public Health. 2008;98(9):1608-1615.

14. Hicken MT, Lee H, Morenoff J, House JS, Williams DR. Racial/ethnic disparities in hypertension prevalence: reconsidering the role of chronic stress. Am J Public Health. 2014;104(1):117-123.

15. Williams DR, Lawrence JA, Davis BA. Racism and health: evidence and needed research. Annu Rev Public Health. 2019;40:105-125.

16. Muntner P, Abdalla M, Correa A, et al. Hypertension in Blacks: unanswered questions and future directions for the JHS (Jackson Heart Study). Hypertension. 2017;69(5):761-769.

17. Spence JD, Rayner BL. Hypertension in Blacks: individualized therapy based on renin/aldosterone phenotyping. Hypertension. 2018;72(2):263-269.

18. Gu A, Yue Y, Desai RP, Argulian E. Racial and ethnic differences in antihypertensive medication use and blood pressure control among US adults with hypertension: the National Health and Nutrition Examination Survey, 2003 to 2012. Circ Cardiovasc Qual Outcomes. 2017;10(1):e003166.

19. Lewis LM, Ogedegbe C, Ogedegbe G. Enhancing adherence of antihypertensive regimens in hypertensive African-Americans: current and future prospects. Expert Rev Cardiovasc Ther. 2012;10(11):1375-1380.

20. Armstrong C; Joint National Committee. JNC8 guidelines for the management of hypertension in adults. Am Fam Physician. 2014;90(7):503-504.

21. Akintunde A, Nondi J, Gogo K, et al. Physiological phenotyping for personalized therapy of uncontrolled hypertension in Africa. Am J Hypertens. 2017;30(9):923-930.