Prevalence Of Hypertension In Blacks Research Articles

Abstract P405: Racial Disparities in Ischemic and Hemorrhagic Post-stroke Mortality in United States Veterans

Introduction: Blacks and Hispanics have been shown to have higher stroke mortality than non-Hispanic whites. However, this may be due to higher incidence of strokes in blacks and Hispanics. Fewer studies have investigated health disparities in post-stroke mortality stratified by stroke type. We studied risk of mortality by race/ethnicity after either incident acute ischemic stroke (AIS) or intracerebral hemorrhage (ICH) in a national sample of patients from the Veteran’s Health Administration (VHA). Methods: We included patients with a first occurrence of an inpatient AIS or ICH in a VHA hospital between 2002-2007. We categorized patients as non-Hispanic white, non-Hispanic black, or Hispanic. Veterans with any prior stroke-related code were excluded. For each of AIS and ICH, we constructed a piecewise multivariate survival model for post event all-cause mortality. We separated follow-up intervals into <30 day, 30-90 day, 90 day-1 year, and >1 year post admission. Results: We identified 36,569 patients with an incident stroke in 2002-2007 (91% AIS, 9% ICH). The proportion of white, black, and Hispanic patients with AIS was 68%, 26%, and 6% respectively; and in ICH was 63%, 27%, and 10%. Compared to whites, blacks had better survival for AIS in the first 30 days, while Hispanics tended to have better survival in the 30-90 day and >1 year intervals. With ICH, blacks had higher mortality in the first 30 days. (Table 1) Conclusion: Blacks experience better 30-day survival after AIS compared to whites, but worse 30-day survival after ICH. This may be driven by higher prevalence of hypertension in blacks leading to small vessel occlusion, which is associated with lower mortality, or poorer control of blood pressure in the setting of ICH, which is associated with higher mortality. Hispanic patients may have better long-term survival after stroke compared to whites, a ‘Hispanic paradox’ that has been shown in other studies. Stroke events should be stratified by ischemic and hemorrhagic type when evaluating for racial disparities in outcomes.

Hypertension in Blacks: Individualized Therapy Based on Renin/Aldosterone Phenotyping.

The prevalence of hypertension in blacks is higher than in other groups. The following is quoted from the 2015 statistical report of the American Heart Association1: “In 2009 to 2012, the age-adjusted prevalence of hypertension was 44.9% and 46.1% among non-Hispanic black men and women, respectively; 32.9% and 30.1% among non-Hispanic white men and women, respectively; and 29.6% and 29.9% among Hispanic men and women, respectively.” In the national REGARDS cohort (Reasons for Geographic and Racial Differences in Stroke)2, among 27 744 participants followed up for 4.4 years (2003–2010), the overall age- and sex-adjusted black/white incidence rate ratio for ischemic stroke was 1.51, but for ages 45 to 54 years, it was 4.02, whereas for those ≥85 years of age, it was 0.86. This suggests that those who survived to 85 years of age did not have resistant hypertension. Among blacks, compared with whites, the relative risk of intracranial atherosclerotic stroke was 5.85; of extracranial atherosclerotic stroke, 3.18; of lacunar stroke, 3.09; and of cardioembolic stroke, 1.58.3 Similarly, Markus et al4 reported that in South London, United Kingdom, the relative risk of stroke because of small vessel disease in black patients was 2.94 (95% confidence interval, 1.97–4.39; P 20 years of age, the age-adjusted relative risk of intracerebral hemorrhage among blacks compared with white patients was 2.4 for men and 3.2 for women.5 In the Northern Kentucky study, “The greatest excess risk of ICH in blacks compared with whites was found among young to middle-aged (35 to 54 years) persons with brain stem (RR, 9.8; 95% CI, 4.2 to 23.0) and deep cerebral (RR, 4.5; 95% CI, 3.0 to 6.8) hemorrhage.”6 Strokes due to small vessel disease …

Sensitivity to Aldosterone

See related article, p 1212–1218 In this issue, Tu et al1 show clear differences in sensitivity of blood pressure (BP) to aldosterone between blacks and those of predominantly white ancestry, in both children and adults. It has long been known that blacks are more salt sensitive than whites: this contribution thus complements the previous findings and has ramifications for the role of aldosterone across the board. The article reports the unusual combination of a long-term (>20 years) observational study on children aged 5 to 17 years starting in 1986 and an acute intervention study comparing the effects of fludrocortisone administration for 2 weeks on BP, weight, and hormonal parameters in black and white adults. The long-term study enrolled 580 children (266 blacks, 314 whites). Age, height, weight, systolic and diastolic BP (DBP), concentrations of plasma electrolytes (Na+ K+), plasma aldosterone (PAC), and renin activity (PRA) were measured, plus urinary excretion of Na+, K+, and creatinine. At baseline, black children were on average 18 months older, with a higher body mass index and slightly but significantly higher BP (103/43 versus 100/41 mm Hg). They also showed significantly lower PAC (9 versus 14 ng/dL) and PRA levels (2.8 versus 3.3 ng/mL per hour), with indistinguishable plasma [K+] and overnight urinary excretion levels of K+ and Na+. In the subsequently re-enrolled adult subcohort, the blacks were 17 months younger, with higher body mass index (31 versus 28) but identical systolic and DBP (116/74 mm Hg). They had lower levels of PRA (1.0 versus 1.5 ng/mL per hour) and PAC (5 versus 9 ng/dL), with levels of plasma K+ and BP indistinguishable from those in whites. Urinary Na+ excretion was similar (78 versus 81 nmol/mg creatinine), but K+ excretion …

Why Do Black Americans Have Higher Prevalence of Hypertension?

See related article, pp 383–389 Studies have consistently reported a higher prevalence of hypertension in blacks than in whites, a main reason for the higher incidence of cardiovascular disease in blacks.1 The long list of putative causes for this higher prevalence suggests that the real reasons are still unknown. Biological differences in the mechanisms of blood pressure control or in the environment and habits of whites and blacks are among the potential causes. The higher prevalence of hypertension in blacks living in the United States instead of Africa2 demonstrates that environmental and behavioral characteristics are the more likely reasons for the higher prevalence in blacks living in the United States. They could act directly or by triggering mechanisms of blood pressure increase that are dormant in blacks living in Africa. Kaplan and Victor3 listed 18 genotypes and intermediate phenotypes that were implicated with an increase of blood pressure in blacks. A higher sensitivity to alcohol could be added to that list.4 Some of these mechanisms, such as a higher renal retention of sodium by blacks, are attractive. The “slavery hypertension hypothesis” states that the higher prevalence of hypertension among blacks could have resulted from an enhanced ability to conserve salt by slaves, protecting them from fatal salt-depletive diseases during the stormy Atlantic passage, such as diarrhea and vomiting.5 This condition would induce hypertension when they and their descendants consumed the much higher sodium content in American compared with African foods. This hypothesis …

The Management of Hypertension in African Americans

The prevalence of hypertension in blacks in the United States is among the highest in the world. Compared with whites, blacks develop hypertension at an earlier age, their average blood pressures are much higher and they experience worse disease severity. Consequently, blacks have a 1.3 times greater rate of nonfatal stroke, 1.8 times greater rate of fatal stroke, 1.5 times greater rate of heart disease death, 4.2 times greater rate of end-stage kidney disease, and a 50% higher frequency of heart failure; overall, mortality due to hypertension and its consequences is 4 to 5 times more likely in African Americans than in whites. The increased prevalence of hypertension and excessive target organ damage is due to a combination of genetic and, most likely, environmental factors. There are no clinical trial data at present to suggest that lower-than-usual BP targets should be set for high-risk demographic groups such as African Americans. The primary means of prevention and early treatment of hypertension in African Americans will be the appropriate use of lifestyle modification. The International Society of Hypertension in Blacks guidelines realize that most patients will require combination therapy, many of them first-line, to reach appropriate BP goals. Although certain classes and combinations of antihypertensive agents have been well-established to be effective, the choice of drugs for combination therapy in African American patients may be different. Within the African American group, the responsiveness to monotherapy with ACE inhibitors, angiotensin receptor blockers, and beta blockers may be less than the responsiveness to diuretics and calcium channel blockers, but these differences are corrected when diuretics are added to the neurohormonal antagonists. Of note, African American patients with systolic BP >15 mm Hg or a diastolic BP >10 mm Hg above goal should be treated with first-line combination therapy.

Racial disparities in hypertension prevalence, awareness, and management.

Effectively reducing cardiovascular disease disparities requires identifying and reducing disparities in risk factors. Improved understanding of hypertension disparities is critical. Cross-sectional analysis of nationally representative samples of black and white adults 20 years and older who participated in the National Health and Nutrition Examination Survey (NHANES) 1999-2002 (white, n = 4624; black, n = 1837) and NHANES III conducted in 1988-1994 (white, n = 7121; black, n = 4709). We examined differences in hypertension prevalence, awareness, treatment, and blood pressure (BP) control among both treated and prevalent cases across the 2 periods. Hypertension prevalence increased significantly from 35.8% to 41.4% among blacks and from 24.3% to 28.1% among whites and remains significantly higher among blacks. Awareness is higher among blacks (77.7% vs 70.4%; P<.001), as is treatment (68.2% vs 60.4%; P<.001). These results are driven by higher rates in black women. Blood pressure control rates among those treated have increased in both races, primarily as a result of increased BP control in black and white men (27.3% and 44.7%, respectively; P<or=.03). Despite the improved BP control rates, disparity in BP control among treated cases increased, with 59.7% of treated whites and 48.9% of treated blacks now reaching BP goal (P<.001). Racial differences in BP control rates among those treated cannot be explained by nonpharmacologic management or health insurance, but educational attainment is associated with BP control. The higher prevalence of hypertension in blacks and the growing disparity in BP control among those treated pharmacologically are causes for concern.

Reactivity as a predictor of subsequent blood pressure: racial differences in the Coronary Artery Risk Development in Young Adults (CARDIA) Study.

This study investigated the association between cardiovascular reactivity and subsequent ambulatory blood pressure in 316 black and white men and women in the Coronary Artery Risk Development in Young Adults (CARDIA) Study. Cardiovascular laboratory reactivity was examined in subjects 20 to 33 years old, and ambulatory blood pressure and heart rate were measured 3 years later. Average ambulatory pressure during a 24-hour period was regressed separately on stress reactivity and standard covariate risk factors in each race/gender subgroup. Blacks had higher blood pressure and heart rates than whites, men had higher blood pressure than women, and women had higher heart rates than men. After controlling for age, baseline systolic pressure, familial history of hypertension, smoking, alcohol consumption, body mass index, and exercise, systolic blood pressure reactivity to star tracing and cold pressor stress were significantly associated with systolic ambulatory pressure in black men and women 3 years later (partial r=0.24 to 0.37). Heart rate reactivity to video challenge and star tracing were also significantly predictive of subsequent ambulatory heart rate in blacks. Diastolic star tracing reactivity was significantly associated with subsequent ambulatory blood pressure in black women (r=0.23), and diastolic reactivity to video and star tracing were significantly predictive of ambulatory diastolic pressure in white men (r=0.39). We conclude that hyperresponsivity to stress may be a risk factor for subsequent blood pressure elevation in blacks and may be one pathway leading to the higher prevalence of hypertension in blacks than in whites.

Where does the black population of South Africa stand on the nutrition transition?

To review data on selected risk factors related to the emergence of noncommunicable diseases (NCDs) in the black population of South Africa. Data from existing literature on South African blacks were reviewed with an emphasis placed on changes in diet and the emergence of obesity and related NCDs. Review and analysis of secondary data over time relating to diet, physical activity and obesity and relevant to nutrition-related NCDs. Urban, peri-urban and rural areas of South Africa. National prevalence data are also included. Black adults over the age of 15 years were examined. Shifts in dietary intake, to a less prudent pattern, are occurring with apparent increasing momentum, particularly among blacks, who constitute three-quarters of the population. Data have shown that among urban blacks, fat intakes have increased from 16.4% to 26.2% of total energy (a relative increase of 59.7%), while carbohydrate intakes have decreased from 69.3% to 61.7% of total energy (a relative decrease of 10.9%) in the past 50 years. Shifts towards the Western diet are apparent among rural African dwellers as well. The South African Demographic and Health Survey conducted in 1998 revealed that 31.8% of African women (over the age of 15 years) were obese (body mass index (BMI) > or = 30kg m(-2)) and that a further 26.7% were overweight (BMI > or = 25 to <30 kg m(-2)). The obesity prevalence among men of the same age was 6.0%, with 19.4% being overweight. The national prevalence of hypertension in blacks was 24.4%, using the cut-off point of 140/90 mmHg. There are limited data on the population's physical activity patterns. However, the effects of the HIV/AIDS epidemic will become increasingly important. The increasing emergence of NCDs in black South Africans, compounded by the HIV/AIDS pandemic, presents a complex picture for health workers and policy makers. Increasing emphasis needs to be placed on healthy lifestyles.

Relation of a postmortem renal index of hypertension to atherosclerosis in youth. The Pathobiological Determinants of Atherosclerosis in Youth (PDAY) Research Group.

In a cooperative multicenter study, Pathobiological Determinants of Atherosclerosis in Youth, of 1164 young men 15 through 34 years of age who died of external causes and were autopsied in forensic laboratories, we measured atherosclerosis of the aorta and the right coronary artery. Using the ratio of intimal thickness to outer diameter of the small renal arteries to predict mean arterial pressure (MAP) during life, we classified the cases as either normotensive (MAP < 110 mm Hg) or hypertensive (MAP > or = 110 mm Hg). By this criterion, the prevalence of hypertension in blacks was 16%; in whites, 12%. Hypertension was associated directly with blood level of glycohemoglobin (an indicator of blood glucose concentration) and with body mass index (BMI) but inversely with thickness of the panniculus adiposus. Among hypertensive compared with normotensive cases, the extent of raised lesions (mainly fibrous plaques) was greater in the aortas of 30- to 34-year-old men and in the right coronary arteries of 25- to 34-year-old men. The prevalence of raised lesions involving 5% or more of the intimal surface was twofold greater in the aortas and right coronary arteries of hypertensive men throughout the 15-to-34-year age span of the study cases. The association of hypertension with raised lesions was not accounted for by adjusting for glycohemoglobin level, BMI, or thickness of the panniculus adiposus. Hypertension is associated with accelerated atherosclerosis in youth.

α 2-Adrenergic receptor gene polymorphism and hypertension in blacks

alpha 2-Adrenergic receptors are found on presynaptic neurons of the central and peripheral nervous systems, on blood vessels, on platelets, on adipocytes, and in the kidney and pancreas. Activation of these ubiquitous adrenoreceptors results in decreased neuronal norepinephrine release, vasodilation, a fall in blood pressure, platelet aggregation, increased sodium excretion, and decreased insulin release. We hypothesized that defects in alpha 2-adrenergic receptors, or postreceptor defects, could explain the increased prevalence of hypertension in blacks. To test our hypothesis, we first determined whether or not a polymorphism of the alpha 2-adrenergic receptor gene was associated with pathologic elevations in blood pressure in American blacks. Dra-I identified a restriction fragment-length polymorphism (RFLP) of 6.3 and 6.7 kb of the alpha 2-adrenergic receptor gene on chromosome 10 in humans. Of 227 patients studied, 13/107 hypertensive subjects were homozygous for the 6.3-kb allele, whereas only 3/120 normotensive volunteers were homozygotes (P = .008). When analyzed by race, 13/82 black hypertensive subjects were homozygous for the 6.3-kb allele, whereas only 2/59 normotensive blacks were homozygous for the 6.3-kb alleles (P = .02). However, only 1/61 white normotensive and 0/25 white hypertensive subjects were homozygous for the 6.3-kb allele (P = 1.00). Ethnic variation among blacks may explain our findings. Alternatively, a genetic polymorphism in, or near, the alpha 2-adrenergic receptor on chromosome 10 can contribute to the development of hypertension in blacks.

Potassium and calcium intake, excretion, and homeostasis in blacks, and their relation to blood pressure

Blacks in the United States have higher blood pressures than whites. They ingest and excrete less calcium and potassium. There is some evidence that blacks have a difference in vitamin D metabolism that might increase any problem caused by low calcium intake. Some studies can be interpreted to suggest that calcium or potassium therapy has greater hypotensive effects in blacks than in whites. Decreased intake of calcium and potassium may be major causes of the greater prevalence of hypertension in blacks than in whites.

Racial Differences in the Incidence of Hypertensive End-Stage Renal Disease (ESRD) Are Not Entirely Explained by Differences in the Prevalence of Hypertension

Blacks experience a disproportionate risk of end-stage renal disease (ESRD) compared with whites. The increased prevalence of hypertension in blacks has been suggested as an explanation for this increased risk. We were able to examine this possibility using hypertensive ESRD incidence rates in a population with well-characterized prevalence of hypertension and rate of its control. After adjusting rates of hypertensive ESRD for age, sex, and differences in the prevalence of hypertension by race, we found black:white (B:W) relative risk still to be increased. Prevalence estimates for moderate-severe hypertension and differences in the control of hypertension between the two race groups are of insufficient magnitude to explain the increase in adjusted relative risk. This observation provides further support for the possibility that there are racial differences in the susceptibility to renal damage from elevated BP, which may explain increased risk for hypertensive ESRD in blacks, or that hypertension is being erroneously diagnosed as the cause of ESRD in blacks when another cause is present.

Duffy antigens and hypertension in a black population.

Skin color and social class have been suggested as reasons to explain the greater prevalence of hypertension in Blacks as compared to Whites. The presence of Duffy red blood cell proteins, a measure of "whiteness" in Blacks, was unrelated to the presence of elevated blood pressure in 722 Black hospital patients. The finding suggests that social class rather than skin color is associated with the greater prevalence of hypertension in Blacks.

Black-white comparison of indices of coronary heart disease and myocardial infarction in the stepped-care cohort of the Hypertension Detection and Follow-Up Program

As part of the initial examination of individuals enrolled in the Hypertension Detection and Follow-Up Program, a standardized questionnaire to elicit symptoms of angina pectoris and myocardial infarction and to inquire about the clinical diagnosis of myocardial infarction was administered. Angina pectoris was more prevalent in black males than white males and more prevalent in black females than white females. In white and black males and in white females, baseline prevalence of angina was associated with and approximate doubling of the 5-year mortality. A positive Rose Questionnaire for myocardial infarction, a positive clinical history of myocardial infarction, or a positived ECG for myocardial infarction was also associated with increased mortality in all of the race-sex groups, with the exception of black females, in whom the ECG evidence of myocardial infarction at baseline was only modestly associated with mortality. The Rose Questionnaire evidence of myocardial infarction was actually associated with a lesser 5-year mortality. The higher prevalence of angina pectoris in black hypertensive males in the face of a high prevalence of hypertension in blacks suggests that the combination of coronary artery disease and hypertension is more of a health problem in black males than in white males. The situation in black females, however, is less clear. The 5-year incidence of myocardial infarction, positive ECG or history, or positive Rose Questionnaire was approximately equal in blacks and whites among the treated hypertensive patients.

Blood pressure in blacks and whites and its relationship to dietary sodium and potassium intake

The 24-hour dietary intake and blood pressure of 1928 black and 9739 white adults derived from the data sets of the first US National Health and Nutrition Examination Survey (NHANES I) of 1971–1974 were analyzed. Contrary to expectation, the absolute and relative intakes of sodium and potassium in blacks were less than those of whites. However, because the difference in potassium was greater than the difference in sodium, blacks did have a significantly higher sodium/potassium ratio than whites. Blacks had significantly higher blood pressure than whites even when adjusted for differences in sodium/potassium ratio. It is concluded that the higher blood pressure and prevalence of hypertension in blacks does not appear to be a function of an absolutely greater dietary sodium intake, but related to a relatively low intake of potassium. It is possible that blacks have a greater sensitivity than whites to the hypertensinogenic effects of sodium which, coupled with the relatively low dietary intake of potassium, accounts for their increased blood pressure.

Racial differences in blood pressure in evans county, Georgia: Relationship to sodium and potassium intake and plasma renin activity

To investigate the hypothesis that the higher prevalence of hypertension in blacks may be related to a greater dietary intake of sodium, we studied the relationship between race, blood pressure, estimates of dietary sodium and potassium intake, and plasma renin activity (PRA), in two population samples from Evans County, Georgia. In the first random sample obtained in 1961, dietary electrolyte intake was estimated by duplicate dietary collections and simultaneous 24-hr urine collections. In the second sample obtained in 1968, a single-morning urine specimen was obtained and PRA was measured in each subject. The data demonstrate that blacks and whites ingested similar quantities of sodium, but that the dietary potassium intake of blacks was consistently less than that of whites. Blacks had higher blood pressures than whites and a greater prevalence of individuals with diastolic blood pressures >90 mmHg. PRA was inversely correlated with age, blood pressure and estimates of sodium intake. The higher blood pressures and higher prevalence of hypertension in blacks does not appear to be a function of a greater dietary sodium intake in blacks. However, an increased susceptibility to the hypertensinogenic effects of sodium in blacks remains a possibility.