Treatment of Hypertension Among African Americans: The Jackson Heart Study

Hypertension treatment regimens used by African American adults in the Jackson Heart Study were evaluated at the first two clinical examinations (2415 treated hypertensive persons at examination I [exam I], 2000–2004; 2577 at examination II [exam II], 2005–2008). Blood pressure (BP) was below 140/90 mm Hg for 66% and 70% of treated participants at exam I and exam II, respectively. The Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure treatment targets were met for 56% and 61% at exam I and exam II, respectively. Persons with diabetes or chronic kidney disease were less likely to have BP at target, as were men compared with women. Thiazide diuretics were the most commonly used antihypertensive medication, and persons taking a thiazide were more likely to have their BP controlled than persons not taking them; thiazides were used significantly less among men than women. Although calcium channel blockers are often considered to be effective monotherapy for African Americans, persons using calcium channel blocker monotherapy were significantly less likely to be at target BP than persons using thiazide monotherapy.     

Association of West African ancestry and blood pressure control among African Americans taking antihypertensive medication in the Jackson Heart Study

African Americans have a wide range of continental genetic ancestry. It is unclear whether racial differences in blood pressure (BP) control are related to ancestral background. The authors analyzed data from the Jackson Heart Study, a cohort exclusively comprised of self‐identified African Americans, to assess the association between estimated West African ancestry (WAA) and BP control (systolic and diastolic BP < 140/90 mm Hg). Three nested modified Poisson regression models were used to calculate prevalence ratios for BP control associated with the three upper quartiles, separately, vs the lowest quartile of West African ancestry. The authors analyzed data from 1658 participants with hypertension who reported taking all of their antihypertensive medications in the previous 24 hours. WAA was estimated using 389 ancestry informative markers and categorized into quartiles (Q1: <73.7%, Q2: >73.7%‐81.0%, Q3: >81.0%‐86.3%, and Q4: >86.3%). The proportion of participants with controlled BP in the lowest‐to‐highest WAA quartile was 75.2%, 76.1%, 76.6%, and 74.4%. The prevalence ratios (95% CI) for controlled BP comparing Q2, Q3, and Q4 to Q1 of WAA were 1.00 (0.93‐1.08), 1.02 (0.94‐1.10), and 0.99 (0.91‐1.07), respectively. Among African Americans in the Jackson Heart Study taking antihypertensive medication, BP control rates did not differ across quartiles of WAA.     

Sex differences in the association of psychosocial resources with prevalent type 2 diabetes among African Americans: The Jackson Heart Study

Aim

To examine the association of psychosocial resources with prevalent type 2 diabetes (T2D) in 5104 African American men and women.

Sleep-disordered breathing and hypertension among African Americans

This study investigated differences in sleep-disordered breathing (SDB) between hypertensives without a family history of hypertension and hypertensives with a family history. Furthermore, it examined whether these two groups differed in the severity of SDB. Patients were African Americans (n=162, mean age=51.19+/-13.77 years; mean body mass index (BMI)=37.85+/-9.51 kg/m2, male=57%), who were referred to the clinic because of a sleep complaint. Sleep was recorded in the laboratory using standard physiological parameters; all parameters were analysed by a trained scorer. Altogether, 91% of the patients received an SDB diagnosis. Of these patients, 25% were hypertensives without a family history, 20% were hypertensives with a family history, and 55% were normotensives. We found a significant difference between these patient groups regarding the severity of SDB (F14,158=1.823, P<0.05), but no significant group difference was observed in the rate of SDB. Increasing weight was accompanied by increasing severity of SDB. The finding that hypertensive patients with or without a positive family history showed worse oxygenation and respiratory characteristics than did normotensives is consistent with previous research. Of note, hypertensives reporting a family history were characterized by a greater number of oxygen desaturations and apnoea hypopnoea index than those typified only by a current diagnosis of hypertension. Hypertensives with a family history are likely to show a profile of greater blood pressure, higher BMI, and more severe SDB, which by all accounts are more common among African Americans.     

Asthma and Asthma Severity among African American Adults in the Jackson Heart Study

The aims of this study were to investigate the baseline prevalence of and risk factors associated with asthma, classify asthma severity, and describe medication use in a population-based sample of African American men and women 21 to 84 years of age from the Jackson Heart Study (JHS). Participants provided responses to respiratory and medical history questions and a medication inventory and underwent spirometry and other clinical examinations. These data were used to examine the extent to which novel and traditional risk factors were associated with asthma. Of the 4,098 participants included in this analysis, 9.4% reported lifetime asthma (5.7% current, 3.7% former), and current asthma was higher in women (6.8%) than in men (3.8%). An additional 9.8% reported an attack of wheeze with shortness of breath or non-doctor confirmed asthma (i.e., “probable” asthma). The mean forced expiratory volume in 1 second (FEV₁)% predicted was lower in those reporting current asthma (women: 83.7 ± 18.0; men: 75.2 ± 16.8) compared to those not reporting asthma (women: 95.6 ± 16.7; men: 91.7 ± 16.0). Current and probable asthma was associated with lower serum cortisol levels and hypertension medication use, along with traditional risk factors (i.e., lower socio-economic status, higher global stress scores, obesity, and fair to poor perceived general health). Severe asthma was low among participants reporting current (9.8%), former (3.3%), and probable (4.9%) asthma. Asthma medication use was reported by nearly 60% of the participants reporting current asthma. Asthma in African American adults is associated with decreased serum cortisol, hypertension medication use, and considerable lung function impairment compared to those who did not report asthma. The prevalence of asthma in the JHS is lower than state and national estimates, although the estimates are not directly comparable. Furthermore, asthma is drastically underdiagnosed in this population.     

Hostility and prevalent diabetes among black adults: The Jackson Heart Study

Background and aimsThe relationship between hostility and the prevalence of diabetes mellitus (DM) among black adults was investigated using the Jackson Heart Study (JHS) cohort. We hypothesized that Cook-Medley Hostility scores will be positively related with the prevalence of DM.Methods and resultsA total of 3232 black adults who completed at least one question for each of the three subscales of the Cook-Medley Hostility Scale and had data available regarding DM status were included. Using multivariate logistic regression, we studied the cross-sectional relationship between the overall Total Cook-Medley Hostility scores and individual subscales, hostile affect (n = 3232), aggression (n = 3119) and cynical distrust (n = 3085), with prevalent DM, adjusting for known DM confounders. Our population was 36% male with a mean age of 53.5 ± 0.9 years. In risk-factor adjusted models, each point higher in the overall Total Cook-Medley Hostility scores was associated with increased odds of having DM [Adjusted OR 1.02, 95%CI 1.00–1.04, P = 0.03]. Higher scores of cynicism were independently associated with prevalent DM [Adjusted OR 1.04, 95%CI 1.01–1.07, p = 0.021].ConclusionsThere was a positive relationship between overall hostility levels and prevalent DM. Future studies should investigate the extent to which additional social determinants may impact the relationship between hostile affect and prevalent DM.     

Metabolic syndrome in African Americans: implications for preventing coronary heart disease

The metabolic syndrome represents a specific clustering of cardiovascular risk factors in the same individual (abdominal obesity, atherogenic dyslipidemia, elevated blood pressure, insulin resistance, a prothrombotic state, and a proinflammatory state). Almost 50 million American adults (about one in four) have the metabolic syndrome, which puts them at increased risk for the development of diabetes mellitus and cardiovascular disease. African Americans, especially African-American women, have a high prevalence of the metabolic syndrome. This is attributable mainly to the disproportionate occurrence in African Americans of elevated blood pressure, obesity, and diabetes. Management of the metabolic syndrome consists primarily of modification or reversal of the root causes (overweight/obesity and physical inactivity) and therapy to reduce or control the risk factors. Although all components of the metabolic syndrome should be addressed, optimal control of atherogenic dyslipidemia and elevated blood pressure may reduce cardiovascular risk by more than 80%.     

Epidemiology, heritability, and genetic linkage of C-reactive protein in African Americans (from the Jackson Heart Study)

C-reactive protein (CRP) has been studied largely in white non-Hispanic cohorts. There is limited information on CRP's range of values, heritability, and relation to cardiovascular disease risk factors in African Americans. The aim of this study was to evaluate the distribution, clinical correlates, heritability, and genetic linkage of log-transformed CRP in participants in the middle-aged to elderly African American cohort in the community-based Jackson Heart Study. The distribution and correlates of CRP were analyzed for the entire study cohort who underwent the first examination (2001 to 2004). Heritability was estimated for the family cohort nested within the larger Jackson Heart Study (246 families, n = 1,317). The relation between CRP and cardiovascular disease risk factors was tested with multivariable stepwise regression analyses. Heritability was estimated using a variance-components method. Linkage analysis was performed using the multipoint variance-components approach. The study sample consisted of 4,919 participants (mean age 55 +/- 13 years, 63% women); the median CRP concentration was 2.7 mg/L. In stepwise models, traditional risk factors explained 23.8% of CRP's variability, with body mass index (partial R(2) = 13.6%) explaining 57.1% of the variability of CRP due to traditional risk factors. The heritability of CRP (adjusted for age, gender, and body mass index) was 0.45. The strongest linkage evidence for CRP was observed on chromosome 11 (11p13 to 11p11.2), with a logarithm of odds score of 2.72. In conclusion, in this large population-based cohort of African Americans, circulating CRP concentration was heritable and associated with several traditional cardiovascular risk factors, particularly body mass index.     

The association of nocturnal hypertension and nondipping blood pressure with treatment‐resistant hypertension: The Jackson Heart Study

Apparent treatment‐resistant hypertension (aTRH), nocturnal hypertension, and nondipping blood pressure (BP) have shared risk factors. The authors studied the association between aTRH and nocturnal hypertension and aTRH and nondipping BP among 524 black Jackson Heart Study participants treated for hypertension. Nocturnal hypertension was defined by mean nighttime systolic BP ≥120 mm Hg or diastolic BP ≥70 mm Hg. Nondipping BP was defined by mean nighttime to daytime systolic BP ratio >0.90. aTRH was defined by mean clinic systolic BP ≥140 mm Hg and/or diastolic BP ≥90 mm Hg with three medication classes or treatment with four or more classes. The risk for developing aTRH associated with nondipping BP and nocturnal hypertension was estimated. After multivariable adjustment, participants with aTRH were more likely to have nocturnal hypertension (prevalence ratio, 1.20; 95% confidence interval, 1.03–1.39) and nondipping (prevalence ratio, 1.25; 95% confidence interval, 1.09–1.43). Over a median 7.3 years of follow‐up, nocturnal hypertension and nondipping BP at baseline were not associated with developing aTRH after adjustment.     

Visceral fat and prevalence of hypertension among African Americans and Hispanic Americans: findings from the IRAS family study

BackgroundWe examined the relationship between visceral adipose tissue (VAT), independent of overall adiposity, and prevalent hypertension among adults enrolled in the Insulin Resistance Atherosclerosis (IRAS) Family Study. We also examined the role of insulin sensitivity (S(I)) upon hypertension. This was a cross-sectional epidemiological study in which African-American and Hispanic-American families were recruited from three clinical sites. The main outcome measure was prevalent hypertension, as defined by standardized protocol.MethodsThe relationship between VAT and prevalent hypertension was examined in adjusted marginal models among 1,582 participants. All continuous variables were standardized.ResultsA significant VAT by gender interaction prompted separate analyses for VAT according to gender. Further adjustment for S(I) was performed to determine its potential roles in the VAT-hypertension relationship. The mean age (s.d.) of the sample was 41.3 (13.8) years, with a mean body mass index (BMI) (s.d.) of 28.7 (6.0) kg/m(2). Women comprised 58.5% of the sample (N = 925), and Hispanic Americans comprised 69.2% of the sample (N = 1,095). One in five participants (21.2%) had prevalent hypertension. In women, VAT was significantly associated with hypertension, independent of BMI (odds ratio (OR) = 1.49, P = 0.006). African-American women demonstrated increased odds of prevalent hypertension compared to Hispanic-American women (OR = 3.08, P < 0.001). Among men, VAT was not associated with hypertension independent of BMI, and BMI explained a significant amount of the variation in hypertension.ConclusionsA significant relationship may exist between VAT and hypertension among women, but not among men. The relationship between VAT and hypertension in women was not associated with insulin resistance.American Journal of Hypertension (2008). doi:10.1038/ajh.2008.213American Journal of Hypertension (2008); 21, 8, 910-916. doi:10.1038/ajh.2008.213.     

Genetic bottlenecks, perceived racism, and hypertension risk among African Americans and first-generation African immigrants

The complexity of factors influencing the development of hypertension (HTN) in African Americans has given rise to theories suggesting that genetic changes occurred due to selection pressures/genetic bottleneck effects (ie, constriction of existing genetic variability) over the course of the slave trade. Ninety-nine US-born and 86 African-born health professionals were compared in a cross-sectional survey examining genetic and psychosocial predictors of HTN. We examined the distributions of three genetic loci (G-protein, AGT-235, and ACE I/D) that have been associated with increased HTN risk. There were no significant differences between US-born African Americans and African-born immigrants in the studied genetic loci or biological variables (eg, plasma renin and angiotensin converting enzyme activity), except that the AGT-235 homozygous T genotype was somewhat more frequent among African-born participants than US-born African Americans. Only age, body mass index, and birthplace consistently demonstrated associations with HTN status. Thus, there was no evidence of a genetic bottleneck in the loci studied, ie, that US-born African Americans have different genotype distributions that increase their risk for HTN. In fact, some of the genotypic distributions evidenced lower frequencies of HTN-related alleles among US-born African Americans, providing evidence of European admixture. The consistent finding that birthplace (ie, US vs Africa) was associated with HTN, even though it was not always significant, suggests potential and unmeasured cultural, lifestyle, and environmental differences between African immigrants and US-born African Americans that are protective against HTN.     

Chronic kidney disease and incident apparent treatment‐resistant hypertension among blacks: Data from the Jackson Heart Study

It is unclear whether black patients with chronic kidney disease (CKD) vs those without CKD who take antihypertensive medication have an increased risk for apparent treatment‐resistant hypertension (aTRH). The authors analyzed 1741 Jackson Heart Study participants without aTRH taking antihypertensive medication at baseline. aTRH was defined as uncontrolled blood pressure while taking three antihypertensive medication classes or taking four or more antihypertensive medication classes, regardless of blood pressure level. CKD was defined as an albumin to creatinine ratio ≥30 mg/g or estimated glomerular filtration rate <60 mL/min/1.73 m². Over 8 years, 20.1% of participants without CKD and 30.5% with CKD developed aTRH. The multivariable‐adjusted hazard ratio for aTRH comparing participants with CKD vs those without CKD was 1.45 (95% CI, 1.12–1.86). Participants with an albumin to creatinine ratio ≥30 vs <30 mg/g (hazard ratio, 1.44; 95% CI, 1.04–2.00) and estimated glomerular filtration rate of 45 to 59 mL/min/1.73 m² and <45 vs ≥60mL/min/1.73 m² (hazard ratio, 1.60 [95% CI, 1.16–2.20] and 2.05 [95% CI, 1.28–3.26], respectively) were more likely to develop aTRH.     

Pathogenesis of hypertension in African Americans

Hypertension is a compelling disease process that disproportionately affects African Americans. It is the single largest risk factor for cardiovascular disease in African Americans. The end organ manifestations of hypertension are striking and include higher rates of stroke, significantly increased renal disease including end-stage renal disease requiring dialysis, higher risk of left ventricular hypertrophy, and an associated higher risk of heart failure. The cause of these more aggressive end organ phenomena is likely multifactorial and includes a mix of genetic and environmental influences. Intriguing polymorphisms of the epithelial sodium channel are consistent with patterns of hypertension seen in African Americans. Obesity, especially in African-American women, may be closely related to hypertension as a result of sympathetic nervous system stimulation.