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Health - Severe Hypertension

African-Americans More Likely to Develop Hypertension But Less Likely to Take Life-Saving Medication

Monday, Feb 20 2012

  

Racial disparities in hypertension control account for nearly 8,000 preventable deaths annually among African-Americans, making increased blood pressure control among African-Americans a ???compelling goal,??? reported Lisa M. Lewis, PhD, RN, of the University of Pennsylvania School of Nursing in the Journal of Cardiovascular Nursing.

African-Americans commonly develop hypertension at a younger age, are less likely to have their blood pressure under control, and disproportionately suffer strokes and fatality when compared with their Caucasian counterparts. Statistics include a 30 percent greater rate of non-fatal stroke, an 80 percent greater rate of fatal stroke, and a staggering 420 percent greater rate of end-stage kidney disease for African-Americans.

But research estimates show that only 51 percent of all patients with hypertension adhere to their medications and that adherence rates are even lower for African-American patients.

Dr. Lewis identified self-efficacy, depression, and patient-provider communication among the factors in medication nonadherence. She called for further study, but advised that these factors are important for healthcare providers to consider when treating hypertensive African-American patients.

???Increasing blood pressure control requires a comprehensive approach,??? wrote Dr. Lewis. ???Given that self-efficacy and patient-provider communication are modifiable factors, they can be the focus of interventions to increase medication adherence. [Clinicians also] may want to screen their hypertensive patients for depression and treat if necessary.???

The prevalence of essential hypertension in blacks is much higher than that in whites. In addition, the pathogenesis of hypertension appears to be different in black patients. For example, black patients present with a salt-sensitive hypertension characterized by low renin levels. Racial differences in renal physiology and socioeconomic factors have been suggested as possible causes of this difference, but reasons for this difference remain unclear. Endothelial cells are important in the regulation of vascular tonus and homeostasis, in part through the secretion of vasoactive substances.

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Despite substantial clinical and laboratory investigation, the reason or reasons for the increased prevalence of hypertension in blacks remain unknown. There clearly are socioeconomic and psychosocial factors involved. There also is accumulating evidence that the pathophysiological basis of hypertension in blacks is different than that in whites. Hypertension is characterized with an abnormal hemodynamic reactivity and increased salt sensitivity. Plasma levels of potent vasoactive peptide ET-1 are significantly higher in blacks in response to acute stress and in the hypertensive states than in whites. Given the fact that ET-1 induces long-lasting vasoconstriction and modulates the sympathetic system??“mediated contractility, it is likely that ET-1 contributes to the abnormal vascular reactivity in blacks. In the peripheral venous circulation, black patients have significantly lower numbers of ETB receptors. Future studies are necessary to determine the effect or effects of these differences in receptor subtype distribution on ET-1??“mediated contractility. Given that blacks exhibit an increased sympathetic system activity, how the vasomotor activity is modulated by the interaction of ET-1 and catecholamines in this population remains to be resolved. Moreover, studies are needed to investigate whether these differences in the receptor subtype distribution exist in healthy individuals and in other vascular beds. If the receptor subtype difference is true in the kidney epithelial cells where ETB receptors are involved in natriuresis and diuresis, the ET system may play an important role in the salt-sensitive component of high blood pressure in blacks. Therefore, a careful consideration of the ET system in blacks and longitudinal studies that investigate the role of ET-1 in the development and complications of hypertension are warranted. Agents that modulate the ET system (ie, ET receptor antagonists, ECE inhibitors, or both) may prove beneficial to reduce the long-term complications of hypertension as well as in the treatment of hypertension in this population.
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Adviye Ergul
From the Department of Surgery, Medical University of South Carolina, Charleston.


The University of Pennsylvania School of Nursing is one of the premier research institutions in nursing, producing new knowledge in geriatrics, pediatrics, oncology, quality-of-life choices, and other areas. Penn Nursing researchers consistently receive more research funding from the National Institutes of Health than any other private nursing school, and many master??™s programs are ranked first in the country. This year, faculty, students, alumni, and staff celebrate 125 years of nursing at Penn.

Hypertension is a serious issue in black populations because this group has the highest incidence of hypertensive morbidity and comorbid conditions (greater risk of stroke and heart and renal disease). Using the drug hydrochlorothiazide, Freis reported that 67% of younger (<55 years) black patients and 80% of older (55-65 years) black patients achieved blood pressure control (diastolic blood pressure of <90 mm Hg). In 1993, Materson et al. reported the similar finding that 40% of younger and 58% of older blacks achieved blood pressure control using hydrochlorothiazide as a single agent. Studies like these supported the position of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC V), which advised low doses of a thiazide diuretic (12.5-25 mg hydrochlorothiazide) as the agent of first choice for hypertensive black patients. JNC VI currently advises that diuretics be used for initial therapy unless there are contraindications or coexisting conditions that might be treated by another agent. In the presence of renal disease, a loop diuretic should be used, as thiazide diuretics become less effective. JNC VI also allows for initial therapy with β blockers. However, β blockers as first-line therapy have been shown to be less predictable than diuretics in black patients; labetalol, a combined blocker, might be recommended as equally effective in both black and Caucasian populations.

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References
Freis ED. Age and antihypertensive drugs (hydrochlorothi-azide, bendroflumethiazide, nadolol and captopril). Am J Cardiol. 1998;61:117-121.
Sixth Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High blood Pressure. Arch Intern Med. 1997;157:2413-2446.
Special report: A review of the sixth report of the Joint National Committee on Prevention, Detection, Evaluaton, and Treatment of High Blood Pressure. Washington, DC: American Pharmaceutical Association; 1998:1-18.
Hall WD. A rational approach to the treatment of hypertension in special populations. Am Fam Phys. 1999;60:156-162.

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Source: University of Pennsylvania School of Nursing


Provided by Armina Hypertension Association

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