Longitudinal assessment of blood pressures in black and white children

Age-related suppression effect of current body weight on the association between birthweight and blood pressure: The Bogalusa heart study

BACKGROUND

It has been controversial whether to adjust for current body weight while examining the relationship between birthweight and blood pressure (BP).

OBJECTIVE

The present study aims to partition the total effect of birthweight on BP into its direct effect and indirect effect through current body mass index (BMI).

METHODS

The study cohort consisted of 6251 participants who had birthweight information with 13 443 observations on BMI and BP in pre-adolescence (4-11 years), adolescence (12-19 years), young adulthood (20-30 years) and mid-adulthood (31-58 years). General third-variable models were used to distinguish the mediation and suppression effects of current BMI on the birthweight-BP association at different ages.

RESULTS

The total effect of birthweight on systolic BP measured as standardized regression coefficient (β) without current BMI included in the model was 0.003 (P = .810) in pre-adolescents, -0.032 (P = .029) in adolescents, -0.066 (P = .002) in young adults and -0.051 (P = .023) in midlife adults. With additional adjustment for BMI, the direct effect of birthweight on systolic BP was strengthened to β = -0.066 (P = .013), β = -0.058 (P = .014), β = -0.094 (P = .020), β = -0.066 (P = .023); the suppression effects of BMI were calculated at 0.070, 0.027, 0.028 and 0.015 in the respective age groups. The decreasing trend of suppression effects with increasing age mimicked the trends of birthweight-BMI and BMI-BP correlations.

CONCLUSIONS

Current body weight has a suppression effect, not a mediation effect, on the birthweight-BP association, with pre-adolescents having the greatest suppression effect. The suppression effect is predominantly determined by birthweight-BMI and BMI-BP correlations.

Temporal relationship between body mass index and uric acid and their joint impact on blood pressure in children and adults: the Bogalusa Heart Study

OBJECTIVE

This study aimed to examine the temporal relationship between body mass index (BMI) and uric acid (UA), and their joint effect on blood pressure (BP) in children and adults.

METHODS

The longitudinal cohorts for temporal relationship analyses consisted of 564 and 911 subjects examined twice 5-14 years apart from childhood to adulthood. The cross-sectional cohorts for mediation analyses consisted of 3102 children and 3402 nondiabetic adults. Cross-lagged panel analysis models were used to examine the temporal relationship between BMI and UA, and mediation analysis models the mediation effect of UA on the BMI-BP association.

RESULTS

After adjusting for age, race, sex and follow-up years in children, and additionally smoking and alcohol drinking in adults, the path coefficients (standardized regression coefficients) from baseline BMI to follow-up UA (0.145 in children and 0.068 in adults) were significant, but the path coefficients from baseline UA to follow-up BMI (0.011 in children and 0.016 in adults) were not. In mediation analyses, indirect effects through UA on the BMI-systolic BP association were estimated at 0.028 (mediation effect = 8.8%) in children and 0.033 (mediation effect = 13.5%) in adults (P < 0.001 for both). Direct effects of BMI on systolic BP (0.289 in children and 0.212 in adults) were significant. The mediation effect parameters did not differ significantly between Blacks and Whites.

CONCLUSIONS

Changes in BMI precede alterations in UA, and the BMI-BP association is in part mediated through BMI-related increase in UA both in children and in adults. These findings have implications for addressing mechanisms of obesity hypertension beginning in early life.

Age-Related Blood Pressure Sensitivity to Aldosterone in Blacks and Whites

Aldosterone sensitivity, defined as the magnitude of the association of plasma aldosterone concentration with blood pressure (BP), seems to be a function of plasma volume. It increases as plasma renin activity decreases, and it is more significant in blacks but less so in whites. Age is a strong determinant of BP, and an increase in aldosterone sensitivity could contribute to the increase in BP. In the present study, we tested the hypothesis that aldosterone sensitivity increases with age. We used observational data collected from normotensive blacks and whites enrolled in a prospective cohort study. They were studied as children (248 blacks/357 whites) and again as young adults (74 blacks/125 whites) over an age range of 7 to 39 years. A varying-coefficient regression analysis was used to explore the influences of aldosterone on systolic BP. After controlling for body mass index, race, and sex, both plasma renin activity and plasma aldosterone concentration were lower in blacks, and their levels declined with age (P<0.001). In blacks, plasma aldosterone concentration decreased 0.25 ng/dL per year; in whites, plasma aldosterone concentration decreased 0.18 per year. Aldosterone's effect on BP, characterized by a smooth function of age, intensified as age increased, especially in blacks (P<0.01), suggesting an increased aldosterone sensitivity with age. In comparison to blacks, age-related changes in aldosterone sensitivity in whites were not statistically significant. These findings extend the rationale for targeting aldosterone in the treatment of hypertension, especially in blacks.

Beliefs about hypertension among Nigerian immigrants to the United Kingdom: A qualitative study

Objective

The aim of the study was to elicit beliefs about hypertension among Nigerian immigrants in the United Kingdom.

Background

The distributions of cardiovascular risk factors and diseases are not shared equally across ethnic and economic groups in the United Kingdom. Its burden is more clustered among minority ethnic populations and migrant groups including black African Nigerian migrants. Similar patterns have been reported across Europe, Australia, Canada, Nordic countries and the United States of America. There are about 300 distinct ethnic groups in Nigeria and reliable information about their beliefs about hypertension is not available. Given that the United Kingdom has a large community of Nigerian immigrants from these different ethno-cultural backgrounds, understanding their unique beliefs about hypertension may help promote appropriate care for this population in the United Kingdom and Nigeria.

Setting

A single Pentecostal church community in West London

Participants

Twenty-seven Nigerian migrant members of the church entered and completed the study

Methods and outcome measure

A qualitative interview study was conducted. The interviews were analysed using thematic framework analysis. The outcome measures were emerging themes from the thematic framework analysis.

Results

Participants expressed beliefs in four major areas related to hypertension: (1) The Meaning of the term hypertension, (2) Perceptions of causation, (3) Effects of hypertension, and (4) Perceptions of treatment. The study revealed a diversity of beliefs about hypertension which incorporated both orthodox and culturally framed ideas.

Conclusions

This study identified important beliefs among Nigerian migrants about hypertension that can contribute to our understanding of the management of hypertension in this group and suggests the need for further research to determine whether these beliefs may be representative of this group.

Ethnicity and arterial stiffness in children and adolescents from a Brazilian population

BACKGROUND

Increased stiffness of large arteries is an important determinant of cardiovascular disease risk. Higher values of arterial stiffness measured by carotid-femoral pulse wave velocity (cf-PWV) have been measured in adult African-Americans compared with whites. Studies assessing ethnic differences in cf-PWV among children and adolescents are scarce. This study sought to evaluate the association between ethnicity and cf-PWV in Brazilian children and adolescents.

METHODS

Seven hundred and seventy-one children and adolescents (211 blacks and 560 nonblacks, 11.3 ± 2.7 years) were included. Arterial stiffness was evaluated by cf-PWV. The ethnic classification was obtained by a single interviewer according to general phenotypes such as skin color, hair shape and facial traces.

RESULTS

Blood pressure was similar in blacks and nonblacks across all pubertal stages. Differently, cf-PWV was higher in blacks than nonblacks pubescent (5.9 ± 0.7 vs. 5.6 ± 0.8 m/s, P = 0.001) and postpubescent (6.1 ± 0.7 vs. 5.7 ± 0.7 m/s, P = 0.042), whereas no difference was detected between blacks and nonblacks prepubescent. These analyses were adjusted for sex, age, height, BMI, SBP and heart rate.

CONCLUSION

Our study showed that higher cf-PWV values in blacks appear in adolescence and are independent of blood pressure values. Therefore, our data suggest adolescence as the key phase for the appearance of the vascular profile found in adults black individuals.

Race and Sex Differences of Long-Term Blood Pressure Profiles From Childhood and Adult Hypertension: The Bogalusa Heart Study

This study aims to characterize longitudinal blood pressure (BP) trajectories from childhood in black-white and sex groups and examine the association between childhood level-independent trajectories of BP and adult hypertension. The longitudinal cohort consisted of 2732 adults who had body mass index and BP measured 4 to 15 times from childhood (4-19 years) to adulthood (20-51 years). Model-estimated levels and linear slopes of BP and body mass index at childhood age points were calculated at 1-year intervals using the growth curve parameters and their first derivatives, respectively. Linear and nonlinear curve parameters differed significantly between race-sex groups; BP levels showed race and sex differences 15 years of age onward. Hypertensives had higher long-term BP levels than normotensives in race-sex groups. Although linear and nonlinear slope parameters of BP were race and sex specific, they differed consistently, significantly between hypertension and normotension groups. BP trajectories during young adulthood (20-35 years) were significantly greater in hypertensives than in normotensives; however, the trajectories during middle-aged adulthood (36-51 years) were significantly smaller in hypertensives than in normotensives. Level-independent linear slopes of systolic BP showed significantly negative associations (odds ratio=0.50≈0.76; P<0.001) during prepuberty period (4-11 years) but significantly positive associations (odd ratio=1.44≈2.80, P<0.001) during the puberty period (13-19 years) with adult hypertension, adjusting for covariates. These associations were consistent across race-sex groups. These observations indicate that adult hypertension originates in childhood, with different longitudinal BP trajectory profiles during young and middle-aged adulthood in black-white and sex groups. Puberty is a crucial period for the development of hypertension in later life.

Racial Disparities in Blood Pressure Trajectories of Preterm Children: The Role of Family and Neighborhood Socioeconomic Status

Racial disparities in cardiovascular disease mortality in the United States remain substantial. However, the childhood roots of these disparities are not well understood. In the current study, we examined racial differences in blood pressure trajectories across early childhood in a sample of African-American and European-American low-birth-weight preterm infants. Family and neighborhood socioeconomic status (SES), measured at baseline, were also examined as explanations for subsequent group disparities. Analyses focused on 407 African-American and 264 European-American children who participated in the Infant Health and Development Program, a US longitudinal study of preterm children born in 1985. Blood pressure was assessed on 6 occasions between the ages of 24 and 78 months, in 1987-1992. Across this age range, the average rate of change in both systolic and diastolic blood pressure was greater among African-American children than among European-American children. Neighborhood SES explained 29% and 24% of the racial difference in the average rate of change in systolic and diastolic blood pressure, respectively, whereas family SES did not account for group differences. The findings show that racial differences in blood pressure among preterm children emerge in early childhood and that neighborhood SES accounts for a portion of racial disparities.

Association of Maternal Plasma Folate and Cardiometabolic Risk Factors in Pregnancy with Elevated Blood Pressure of Offspring in Childhood

BACKGROUND

The prevalence of childhood elevated blood pressure (BP) has increased in the United States, particularly among African Americans. The influence of maternal plasma folate levels, alone or in combination with maternal cardiometabolic risk factors (hypertensive disorders, diabetes, and prepregnancy obesity), on child systolic BP (SBP) has not been examined in a prospective birth cohort. We hypothesize that adequate maternal folate levels can reduce the risk of elevated SBP in children born to mothers with cardiometabolic risk factors.

METHODS

This study included 1,290 mother-child dyads (875 African Americans (67.8%)) recruited at birth and followed prospectively up to age 9 years from 2003 to 2014 at the Boston Medical Center. Child SBP percentile was calculated according to US reference data and elevated SBP was defined as SBP ≥75th percentile.

RESULTS

Maternal folate levels, overall, were not associated with child SBP. However, we found a significant multiplicative interaction between maternal cardiometabolic risk factors and maternal folate levels (Pinteraction = 0.015) on childhood elevated SBP. Among children born to mothers with any cardiometabolic risk factors, those whose mothers had folate levels above (vs. below) the median had 40% lower odds of elevated childhood SBP (odds ratio = 0.60, 95% confidence interval: 0.40-0.90). The associations did not differ appreciably in analyses restricted to African Americans, and they were not explained by gestational age, size at birth, prenatal folate intake, or breastfeeding.

CONCLUSIONS

Findings from our urban minority birth cohort suggest that higher levels of maternal folate may help counteract the adverse associations of maternal cardiometabolic risk factors on child SBP.

Varying Influences of Aldosterone on the Plasma Potassium Concentration in Blacks and Whites

BACKGROUND

Aldosterone acts to restrain the extracellular potassium (K+) concentration. Blacks have on average lower plasma aldosterone concentrations (PACs) than Whites. Whether this ethnic difference is associated with similar changes in the concentration of K+ is unclear.

METHODS

Subjects were Blacks and Whites from an observational study of blood pressure regulation. PAC was known to be significantly lower in Blacks than Whites. We sought to test the hypothesis that the concentration of K+ remains constant despite variability in PAC. Initial enrollment took place in childhood in 1986. Some of the original enrollees were studied again in adulthood: 160 healthy Blacks and 271 healthy Whites (ages 5 to 39 years; all were studied as children and as adults).

RESULTS

Plasma renin activity [a biomarker of angiotensin II and, more proximally, extracellular fluid volume (ECFV)] and PAC were lower in Blacks (P < 0.0354 and P < 0.001, respectively, for all ages). At the same time no ethnic difference in levels of K+ was observed regardless of age. Plasma K+ concentration and PAC associated differently based on ethnicity: PAC increased in Blacks by 1.5-2.0 and in Whites by 2.3-3.0 ng/dl per mmol/l increase in K+ (P < 0.001).

CONCLUSIONS

Lower aldosterone levels in Blacks did not translate into higher K+ concentrations. We speculate that reaching the right concentration of K+ was an endpoint of aldosterone production in the presence of varying levels of ECFV and angiotensin II.

Temporal Relationship Between Elevated Blood Pressure and Arterial Stiffening Among Middle-Aged Black and White Adults: The Bogalusa Heart Study

This study assessed the temporal relationship between elevated blood pressure (BP) and arterial stiffness in a biracial (black-white) cohort of middle-aged adults aged 32-51 years from the semirural community of Bogalusa, Louisiana. Measurements of aortic-femoral pulse wave velocity (afPWV; n = 446) and large- and small-arterial compliance (n = 381) were obtained at 2 time points between 2000 and 2010, with an average follow-up period of 7 years. A cross-lagged path analysis model was used to examine the temporal relationship of elevated BP to arterial stiffness and elasticity. The cross-lagged path coefficients did not differ significantly between blacks and whites. The path coefficient (ρ2) from baseline BP to follow-up afPWV was significantly greater than the path coefficient (ρ1) from baseline afPWV to follow-up BP (ρ2 = 0.20 vs. ρ1 = 0.07 (P = 0.048) for systolic BP; ρ2 = 0.19 vs. ρ1 = 0.05 (P = 0.034) for diastolic BP). The results for this 1-directional path from baseline BP to follow-up afPWV were confirmed, although marginally significant, by using large- and small-artery elasticity measurements. These findings provide strong evidence that elevated BP precedes large-artery stiffening in middle-aged adults. Unlike the case in older adults, the large-arterial wall is not stiff enough in youth to alter BP levels during young adulthood.

The effect of body mass index on blood pressure varies by race among obese children

OBJECTIVE

Previous studies have shown that the effect of adiposity on blood pressure (BP) intensifies as children become increasingly obese. Black children tend to have greater body mass index (BMI) and higher BP than age-matched white children. It is unclear whether the BP effects of BMI are race-specific among black and white children, and data on obese Hispanic children are sparse. We compared the BP effect of BMI in obese white, black, and Hispanic children.

METHODS

We examined the medical records of children enrolled in a pediatric obesity clinic. Height, weight, BP, and fasting insulin were assessed as part of routine clinical care. The concurrent effects of age and BMI on BP percentile values were examined using semiparametric regression, which allows the accommodation of nonlinear effects.

RESULTS

The study included 873 children (338 male; 354 black, 447 white, 72 Hispanic; 11.7±3.5 years, BMI 36.2±8.5 kg/m2). While BMI Z-scores were similar among the groups, systolic BP (SBP) was higher in black children and Hispanic children (white: 107 mm Hg; black: 112 mm Hg; Hispanic: 112 mm Hg; p=0.0001). Age, sex, and height-adjusted SBP percentiles were significantly different among the three groups (white: 50; black: 59; Hispanic: 59; p=0.0006). In children of the same age, BP was higher at any given BMI in black children and Hispanic children.

CONCLUSIONS

Among children referred for treatment of obesity, black children and Hispanic children are at a greater risk for having elevated BP when compared to white children of similar age and BMI.

Effects of Hatha yoga on blood pressure, salivary α-amylase, and cortisol function among normotensive and prehypertensive youth

OBJECTIVE

Evidence is accumulating, predominantly among clinical trials in adults, that yoga improves blood pressure (BP) control, with downregulation of the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system (SNS) projected as underlying mechanisms. This pilot study assessed whether Hatha yoga has the potential to reduce BP among youth and whether dampening of the SNS and/or HPA activity is a likely pathway of change.

DESIGN

Thirty-one seventh graders were randomly assigned to a Hatha yoga program (HYP) or attention control (AC) music or art class. Baseline and 3-month evaluations included resting BP; overnight urine samples; and saliva collected at bedtime, upon awakening, and at 30 and 60 minutes after awakening for α-amylase and cortisol assays.

RESULTS

Twenty-eight (14 in the HYP group and 14 in the AC group) students were assessed both before and after the intervention. BP changes from pre- to post-intervention were -3.0/-2.0 mmHg for the HYP group and -0.07/-0.79 mmHg for the AC group (p=0.30 and 0.57, respectively). Changes in systolic BP (SBP)/diastolic BP (DBP) for the prehypertensive (75th-94th percentiles for SBP) subgroup analyses were -10.75/-8.25 mmHg for the HYP group (n=4) versus 1.8/1.0 mmHg for the AC group (n=5) (p for SBP=0.02; p for DBP=0.09). Although no statistically significant group differences were observed with changes in SNS or HPA awakening curves (area under curve for α-amylase and cortisol, respectively), a small to moderate effect size was seen favoring a reduction of α-amylase activation for the HYP group (Cohen d=0.34; prehypertensive d=0.20).

CONCLUSIONS

A school-based Hatha yoga program demonstrated potential to decrease resting BP, particularly among prehypertensive youth. Reduced SNS drive may be an underlying neurohormonal pathway beneficially affected by the program. A large-scale efficacy/effectiveness randomized clinical trial is warranted.

Hypertension in the teenager

Over the last two decades, essential hypertension has become common in adolescents, yet remains under-diagnosed in absence of symptoms. Diagnosis is based on normative percentiles that factor in age, sex and height. Evaluation is more similar to adult essential hypertension than childhood secondary hypertension. Modifiable risk factors such as obesity, sodium consumption and low exercise should be addressed first. Many anti-hypertensive medications now have specific regulatory approval for children. Sports participation need not be limited in mild or well-controlled cases. Primary care physicians play an important role in reduction of cardiovascular mortality by early detection and referral when needed.

Aldosterone contributes to elevated left ventricular mass in black boys

BACKGROUND

Left ventricular hypertrophy (LVH) poses a great risk of cardiovascular morbidity and mortality in adults and may pose a serious risk in children. Adult studies have shown that renin-angiotensin-aldosterone system (RAAS) levels directly correlate with left ventricular mass index (LVMI). The purpose of this study is to explore race- and sex-related effects of the RAAS on LVMI in adolescents.

METHODS

Data were collected from a sample of 89 blacks (44 girls, 45 boys) and 102 whites (40 girls, 62 boys) aged 15-19. Data collected included sex, age, body mass index (BMI), LVMI, baseline blood pressure, and levels of aldosterone and angiotensin II.

RESULTS

In black males, increased aldosterone levels correlated with decreased sodium excretion (r= -0.336, p=0.024), increased blood pressure (r=0.358, p=0.016), and increased LVMI (r=0.342, p=0.022). In black females, increased aldosterone levels correlated with increased baseline blood pressure (r=0.356, p=0.018). In white males, increased aldosterone correlated with decreased sodium excretion (r= -0.391, p=0.002). In white females, aldosterone levels correlated with increased baseline blood pressure (r=0.323, p=0.042) and decreased sodium excretion (r= -0.342, p=0.031).

CONCLUSIONS

The results suggest the following model in black males: increased aldosterone leads to increased sodium retention, causing a volume-mediated increase in blood pressure; increased blood pressure results in increased left ventricular mass, and eventually LVH.

Variations in the potassium channel genes KCNK3 and KCNK9 in relation to blood pressure and aldosterone production: an exploratory study

CONTEXT

Two potassium (K) channel genes, Kcnk3 and Kcnk9, when deleted in mice, produced a model of hyperaldosteronism and hypertension.

OBJECTIVE

Our objective was to explore genetic variation [single-nucleotide polymorphisms (SNP)] in KCNK3 and KCNK9 in relation to blood pressure (BP) and aldosterone production in humans.

SUBJECTS AND STUDY DESIGN

Two groups of healthy European Americans (EA) and African Americans (AA) were studied: 1) a longitudinal study group (age ∼14 yr when enrolled, 444 EA and 351 AA) and 2) an inpatient cross-sectional study group (age ∼23 yr, 85 EA and 109 AA). Plasma renin activity, plasma aldosterone concentration, and level of serum K were measured cross-sectionally; BP was measured semiannually in the longitudinal study. SNP were selected to provide coverage of the genes for both EA and AA (15 in KCNK3 and 74 in KCNK9).

RESULTS

No associations with KCNK3 were observed. In the longitudinal study, multiple SNP in KCNK9 associated with systolic BP in AA, whereas associations were primarily with aldosterone production in EA. The direction of the changes was the same for aldosterone production and BP, whereas serum K changed in the opposite direction. In the cross-sectional study, associations were observed only in AA. Combining the two studies, one SNP in particular, rs888345, was strongly associated with BP in AA and with indices of aldosterone production in AA and EA.

CONCLUSION

Results of an exploratory study suggest that BP and aldosterone production may be affected by variations in KCNK9. The findings could have relevance to risk for hypertension.

Lower Serum Adiponectin Levels in African-American Boys

OBJECTIVE

To examine adiponectin, an adipocyte-secreted hormone with anti-inflammatory and insulin-sensitizing effects, in relation to race or gender in younger subjects.

RESEARCH METHODS AND PROCEDURES

The relationship of adiponectin, quantitated by radioimmunoassay, to anthropometric and metabolic factors (fasting insulin, glucose, and leptin) and reproductive hormones was examined in 46 healthy African Americans (25 girls/21 boys) and 40 whites (20 girls/20 boys) ranging in age from 12 to 21 years.

RESULTS

There was no statistical difference in BMI or in BMI percentile among the four groups. Sums of skinfolds, but not skinfold percentile, were significantly lower in boys than girls (p = 0.001 and p = 0.896, respectively), whereas there was no difference between racial groups. Leptin was significantly greater in girls (p = 0.0002). There was no difference in fasting serum glucose, insulin, or homeostasis model assessment score among any of the groups. There was a significant negative univariate relationship between serum adiponectin and both BMI and BMI percentile for the entire group (p = 0.006 and p = 0.005). In a multivariate model, BMI percentile (p = 0.005) and the interaction between race and gender (p = 0.026) were significant predictors of serum adiponectin. In this model, African-American boys had the lowest serum adiponectin level, 37% less than white boys, who had the highest adiponectin levels.

DISCUSSION

Serum adiponectin levels are reduced in young obese subjects (African Americans and whites) and are lower in African-American boys than white boys. A lower adiponectin level in African-American boys may predispose this group to a greater risk of diabetes and cardiovascular disease.

Genetic variation of GPLD1 associates with serum GPI-PLD levels: a preliminary study

HDL is a heterogeneous mixture of lipoprotein particles varying in composition, size, and function. We and others have described a small (7.0nm), minor (0.1% of total apolipoprotein AI) particle containing apolipoprotein AI, AIV and glycosylphosphatidylinositol-specific phospholipase D (GPI-PLD) in humans the function of which is not entirely known. Circulating GPI-PLD levels are regulated by multiple factors including genetics. To determine if genetic variation in GPLD1 affects circulating GPI-PLD levels, we examined the relationship between 32 SNPS upstream, within, and downstream of GPLD1 and circulating GPI-PLD levels in Caucasians (n=77) and African-Americans (n=99). The genotype distribution among races differed at 13 SNPs. Nine SNPS were associated with circulating GPI-PLD levels in Caucasians but not African-Americans. These results suggest that genetic variation of GPLD1 appears to associate with circulating GPI-PLD levels. This article is part of a Special Issue entitled Advances in High Density Lipoprotein Formation and Metabolism: A Tribute to John F. Oram (1945-2010).

Differential Impact of Stress Reduction Programs upon Ambulatory Blood Pressure among African American Adolescents: Influences of Endothelin-1 Gene and Chronic Stress Exposure

Stress-activated gene × environment interactions may contribute to individual variability in blood pressure reductions from behavioral interventions. We investigated effects of endothelin-1 (ET-1) LYS198ASN SNP and discriminatory stress exposure upon impact of 12-week behavioral interventions upon ambulatory BP (ABP) among 162 prehypertensive African American adolescents. Following genotyping, completion of questionnaire battery, and 24-hour ABP monitoring, participants were randomized to health education control (HEC), life skills training (LST), or breathing awareness meditation (BAM). Postintervention ABP was obtained. Significant three-way interactions on ABP changes indicated that among ET-1 SNP carriers, the only group to show reductions was BAM from low chronic stress environments. Among ET-1 SNP noncarriers, under low chronic stress exposure, all approaches worked, especially BAM. Among high stress exposure noncarriers, only BAM resulted in reductions. If these preliminary findings are replicated via ancillary analyses of archival databases and then via efficacy trials, selection of behavioral prescriptions for prehypertensives will be edging closer to being guided by individual's underlying genetic and environmental factors incorporating the healthcare model of personalized preventive medicine.

Intensified effect of adiposity on blood pressure in overweight and obese children

In children, blood pressure (BP) and risk for hypertension are proportional to degree of adiposity. Whether the relationship to BP is similar over the full range of adiposity is less clear. Subjects from a cohort study (n=1111; 50% male and 42% black) contributed 9102 semiannual BP and height/weight assessments. The mean enrollment age was 10.2 years, and mean follow-up was 4.5 years. Adiposity was expressed as body mass index percentile, which accounted for effects of age and sex. The following observations were made. The effect of relative adiposity on BP was minimal until the body mass index percentile reached 85, beginning of the overweight category, at which point the effect of adiposity on BP increased by 4-fold. Similarly intensified adiposity effects on BP were observed in children aged ≤10, 11 to 14 years, and ≥15 years. Serum levels of the adipose tissue-derived hormone, leptin, together with heart rate, showed an almost identically patterned relation to BP to that of body mass index percentile and BP, thus implicating a possible mediating role for leptin. In conclusion, there is a marked intensification of the influence of adiposity on BP when children reach the categories of overweight and obese. Among the possible pathways, leptin may be a potentially important mediator acting through the sympathetic nervous system (reflected in heart rate). The findings have relevance to interventions designed to prevent or treat adiposity-related increases in BP and to the analytic approaches used in epidemiological studies.

Impact of Stress Reduction Interventions on Hostility and Ambulatory Systolic Blood Pressure in African American Adolescents

This study examined the impact of breathing awareness meditation (BAM), life skills (LS) training, and health education (HE) interventions on self-reported hostility and 24-hour ambulatory blood pressure (ABP) in 121 African American (AA) ninth graders at increased risk for development of essential hypertension. They were randomly assigned to BAM, LS, or HE and engaged in intervention sessions during health class for 3 months. Before, after, and 3 months following intervention cessation, self-reported hostility and 24-hour ABP were measured. Results indicated that between pre- and postintervention, BAM participants displayed significant reductions in self-reported hostility and 24-hour systolic ABP. Reductions in hostility were significantly related to reductions in 24-hour systolic ABP. Between postintervention and follow-up, participants receiving LS showed a significant reduction in hostility but not in 24-hour ABP. Significant changes were not found for the HE group in 24-hour ABP or self-reported hostility, but these change scores were significantly correlated. The implications of the findings are discussed with regard to behavioral stress reduction programs for the physical and emotional health of AAs.

Relationship of home blood pressure with target-organ damage in children and adolescents

The objective of this study was to compare home blood pressure (HBP) vs. ambulatory (ABP) and clinic (CBP) measurements in terms of their association with target-organ damage in children and adolescents. A total of 81 children and adolescents (mean age 13 ± 3 years, 53 boys) referred for elevated CBP had measurements of CBP (1 visit), HBP (6 days) and ABP (24-h). Seventy-six participants were also assessed with carotid-femoral pulse wave velocity (PWV) and 54 with echocardiography. Average CBP was 122.1 ± 15.1/71 ± 12.9 mm Hg (systolic/diastolic), HBP 121.3 ± 11.5/69.4 ± 6.6 mm Hg and 24-h ABP 118.9 ± 12/66.6 ± 6.1 mm Hg. Left ventricular mass (LVM) was correlated with systolic blood pressure (BP) (coefficient r = 0.55/0.54/0.45 for 24-h/daytime/nighttime ABP, 0.53 for HBP and 0.41 for CBP; all P< 0.01). No significant correlations were found for diastolic BP. PWV was also significantly correlated with systolic BP (r = 0.52/0.50/0.48 for 24-h/daytime/nighttime ABP, 0.50 for HBP and 0.47 for CBP; all P < 0.01). Only diastolic ABP and HBP were significantly correlated with PWV (r = 0.30 and 0.28, respectively, P<0.05). In multivariate stepwise regression analysis (with age, gender, body mass index [BMI], clinic, home and 24-h ambulatory systolic/diastolic BP and pulse pressure, clinic, home and 24-h heart rate as independent variables), PWV was best predicted by systolic HBP (R(2) = 0.22, beta ± s.e. = 0.06 ± 0.01), whereas LVM was determined (R(2) = 0.67) by 24-h pulse pressure (beta = 1.21 ± 0.41), age (beta = 2.93 ± 1.32), 24-h heart rate (beta = -1.27 ± 0.41) and BMI (beta = 1.78 ± 0.70). These data suggest that, in children and adolescents, ABP as well as HBP measurements appear to be superior to the conventional CBP measurements in predicting the presence of subclinical end-organ damage.

Breathing awareness meditation and LifeSkills Training programs influence upon ambulatory blood pressure and sodium excretion among African American adolescents

PURPOSE

To evaluate the effect of breathing awareness meditation (BAM), Botvin LifeSkills Training (LST), and health education control (HEC) on ambulatory blood pressure and sodium excretion in African American adolescents.

METHODS

Following 3 consecutive days of systolic blood pressure (SBP) screenings, 166 eligible participants (i.e., SBP >50th-95th percentile) were randomized by school to either BAM (n = 53), LST (n = 69), or HEC (n = 44). In-school intervention sessions were administered for 3 months by health education teachers. Before and after the intervention, overnight urine samples and 24-hour ambulatory SBP, diastolic blood pressure, and heart rate were obtained.

RESULTS

Significant group differences were found for changes in overnight SBP and SBP, diastolic blood pressure, and heart rate over the 24-hour period and during school hours. The BAM treatment exhibited the greatest overall decreases on these measures (Bonferroni adjusted, ps < .05). For example, for school-time SBP, BAM showed a change of -3.7 mmHg compared with no change for LST and a change of -.1 mmHg for HEC. There was a nonsignificant trend for overnight urinary sodium excretion (p = .07), with the BAM group displaying a reduction of -.92 ± 1.1 mEq/hr compared with increases of .89 ± 1.2 mEq/hr for LST and .58 ± .9 mEq/hr for HEC group.

CONCLUSION

BAM appears to improve hemodynamic function and may affect sodium handling among African American adolescents who are at increased risk for development of cardiovascular disease.

Adult hypertension is associated with blood pressure variability in childhood in blacks and whites: the bogalusa heart study

BACKGROUND

Blood pressure (BP) is a variable physiological parameter in health and disease. Increased BP variability over time in adults is associated with severity of end-organ damage and a higher rate of cardiovascular events, even after adjusting for the mean levels. This study tested the hypothesis that childhood BP variability, besides the mean levels, is also predictive of adulthood hypertension.

METHODS

The study cohort consisted of 1,797 subjects (1,091 whites and 706 blacks; age = 21-48 years) enrolled in the Bogalusa Heart Study since childhood. BP variability was depicted as s.d. of 4-8 serial measurements in childhood.

RESULTS

Blacks showed significantly greater childhood systolic BP (SBP) variability than whites. In multivariable logistic regression analyses, adjusting for race, sex, mean childhood age, s.d. of childhood body mass index (BMI), mean childhood BP levels, adulthood age and BMI, adult hypertension was significantly associated with s.d. of childhood SBP (odds ratio (OR) (95% confidence intervals) = 1.28 (1.09, 1.51), P = 0.002) and s.d. of childhood diastolic BP (DBP; 1.36 (1.16, 1.58), P < 0.001). When using adulthood BP levels as continuous dependent variables in linear regression models, adjusting for the same covariates, adulthood SBP and DBP levels were significantly associated with s.d. of childhood SBP (standardized regression coefficient β = 0.086, P < 0.001) and s.d. of childhood DBP (β = 0.105, P < 0.001), respectively.

CONCLUSIONS

Increases in BP variations as well as levels in early life are predictive of adult hypertension, which underscore the childhood origin of the natural history of essential hypertension.

Synchronization of adolescent blood pressure and pubertal somatic growth

BACKGROUND

Blood pressure (BP) and growth increase at an accelerated rate during puberty. The temporal relationship of the two events has not been well characterized.

OBJECTIVE

The purpose of this current investigation was to examine the rate of BP change in relation to pubertal growth with the intent to shed light on new mechanisms by which BP is regulated.

METHODS

We examined data from a cohort of 182 normotensive children who had measurements made semiannually for up to 12 yr. From the recorded heights, we identified the subject-specific pubertal growth spurt (PGS) using a growth curve model. With the estimated PGS as an anchoring point, we obtained the rates at which BP and weight changed as continuous functions of time for the duration of pubertal growth. Examining BP on a scale relative to PGS placed BP development in the context of pubertal growth.

RESULTS

Average ages at PGS were 11.5 for girls and 13.3 for boys. Fitted spline models estimated that at the time of PGS, the mean systolic BP was 100 mm Hg for girls and 107 mm Hg for boys; the mean diastolic BP at the PGS was 59 mm Hg for girls and 61 mm Hg for boys. The most intriguing observation was that rate of change in systolic BP and weight peaked at precisely the estimated PGS.

CONCLUSION

The time synchronization of rates of change in BP, weight, and height suggests common regulating mechanisms for somatic growth and BP or growth changes that secondarily affect BP.

Ethnic differences in proximal and distal tubular sodium reabsorption are heritable in black and white populations

BACKGROUND

Segmental handling of sodium along the proximal and distal nephron might be heritable and different between black and white participants.

METHODS

We randomly recruited 95 nuclear families of black South African ancestry and 103 nuclear families of white Belgian ancestry. We measured the (FENa) and estimated the fractional renal sodium reabsorption in the proximal (RNaprox) and distal (RNadist) tubules from the clearances of endogenous lithium and creatinine. In multivariable analyses, we studied the relation of RNaprox and RNadist with FENa and estimated the heritability (h) of RNaprox and RNadist.

RESULTS

Independent of urinary sodium excretion, South Africans (n = 240) had higher RNaprox (unadjusted median, 93.9% vs. 81.0%; P < 0.001) than Belgians (n = 737), but lower RNadist (91.2% vs. 95.1%; P < 0.001). The slope of RNaprox on FENa was steeper in Belgians than in South Africans (-5.40 +/- 0.58 vs. -0.78 +/- 0.58 units; P < 0.001), whereas the opposite was true for the slope of RNadist on FENa (-3.84 +/- 0.19 vs. -13.71 +/- 1.30 units; P < 0.001). h of RNaprox and RNadist was high and significant (P < 0.001) in both countries. h was higher in South Africans than in Belgians for RNaprox (0.82 vs. 0.56; P < 0.001), but was similar for RNadist (0.68 vs. 0.50; P = 0.17). Of the filtered sodium load, black participants reabsorb more than white participants in the proximal nephron and less postproximally.

CONCLUSION

Segmental sodium reabsorption along the nephron is highly heritable, but the capacity for regulation in the proximal and postproximal tubules differs between whites and blacks.

Association of the calcium-sensing receptor gene with blood pressure and urinary calcium in African-Americans

CONTEXT

Calcium binding to the Ca-sensing receptor (CASR) expressed in thick ascending limb inhibits the Na,K,2Cl cotransporter, which decreases sodium reabsorption and secondarily decreases Ca reabsorption. CASR gene variants could influence blood pressure (BP) by affecting Na retention.

OBJECTIVE

The objective of the study was to determine whether variations in CASR associated with BP in African-Americans, an ethnic group at high risk for hypertension.

DESIGN

Population- and family-based association studies of single-nucleotide polymorphisms (SNPs) in CASR with BP measured over the age range 5.6-25 yr (14 biannual visits per subject on average) were carried out. In a cross-sectional study where urinary Ca excretion had been measured, Ca excretion was used as an additional phenotype of CASR influence on Na,K,2Cl cotransporter activity.

PARTICIPANTS

Subjects were normotensive. In the longitudinal study, there were 223 subjects (mean age 14 yr) and 123 families (one or both parents provided a DNA sample); in the cross-sectional study, there were 106 subjects (mean age 23 yr) and 88 families.

RESULTS

Three SNPs in linkage disequilibrium associated with systolic BP at P < 0.005 (the significance threshold corrected for multiple comparisons) in the population-based longitudinal study. In the cross-sectional study, SNPs contained in the same linkage disequilibrium block associated with urinary Ca excretion in both population- and family-based association studies.

CONCLUSION

The findings suggest that in African-Americans, functional heterogeneity of the CASR in thick ascending limb may influence BP.

Inverse associations between androgens and renal function: the Young Men Cardiovascular Association (YMCA) study

BACKGROUND

Men exhibit higher risk of nondiabetic renal diseases than women. This male susceptibility to renal disease may be mediated by gender-specific factors such as sex hormones.

METHODS

We have undertaken a cross-sectional examination of associations between renal function (creatinine clearance estimated based on Cockcroft-Gault equation) and circulating levels of sex steroids (total testosterone, total estradiol, estrone, androstenedione, dehydroepiandrosterone sulfate (DHEA-S), and dihydrotestosterone) in 928 young (mean age: 18.5 +/- 1.2 years) men.

RESULTS

Both androstenedione and DHEA-S showed inverse linear associations with renal function in the crude analysis of lean men (those with body mass index (BMI) less than median). However, only DHEA-S retained its association with renal function in lean subjects after adjustment--assuming no changes in other independent variables 1 s.d. increase in DHEA-S was associated with 13%-s.d. decrease in creatinine clearance (P = 0.004). Testosterone decreased across tertiles of creatinine clearance only in the crude analysis of nonlean (BMI greater than median) subjects (P < 0.001). The adjusted regression analysis that assumed no changes in other independent variables showed that 1 s.d. increase in total testosterone was associated with 11%-s.d. decrease in creatinine clearance of nonlean men (P = 0.006). Factor analysis confirmed an inverse association of renal function with both sex steroids and a different pattern of their loadings on glomerular filtration-related factors in lean (DHEA-S) and nonlean (testosterone) subjects.

CONCLUSIONS

Our data may suggest that androgens are inversely associated with estimated renal function in apparently healthy men without history of cardiovascular disease.

Ethnic Differences in Renal Responses to Furosemide

Blacks have a greater tendency to retain Na than whites. The present study sought evidence for ethnic differences in parameters reflective of Na uptake by the Na,K,2Cl cotransporter in the thick ascending limb, namely, the urine concentration and urinary excretion of certain cations before and after furosemide administration (40 mg IV). Subjects were healthy (ages 18 to 36 years). During the preceding overnight period, urine volume was lower, and osmolality was higher in blacks than in whites, an ethnic difference that disappeared when water intake was restricted to infused normal saline (60 mL/h). Plasma vasopressin levels were higher in black males than in other sex/ethnic groups. Baseline urinary excretion rates of K, Ca, and Mg were significantly lower in blacks than in whites. After furosemide (0 to 1 hour), K and Ca excretion rates increased, but the proportionate ethnic difference decreased from 44% to 22% and from 22% to 10%, respectively, consistent with blacks having more basal Na,K,2Cl cotransporter activity to inhibit. During a later postfurosemide period (1 to 5 hours), urinary concentrations of Ca and Mg recovered more slowly in blacks, consistent with greater reuptake in the thick ascending limb. In summary, there were distinct ethnic differences in renal handling of Ca and Mg basally and in response to furosemide that were consistent with a more active Na,K,2Cl cotransporter in the thick ascending limb in blacks. An increase in vasopressin levels appeared to explain greater urine concentrations in black males but not black females.

Corin variant associated with hypertension and cardiac hypertrophy exhibits impaired zymogen activation and natriuretic peptide processing activity

Corin is a cardiac serine protease that acts as the pro-atrial natriuretic peptide (ANP) convertase. Recently, 2 single-nucleotide polymorphisms (SNPs) (T555I and Q568P) in the human corin gene have been identified in genetic epidemiological studies. The minor I555/P568 allele, which is more common in African Americans, is associated with hypertension and cardiac hypertrophy. In this study, we examined the effect of T555I and Q568P amino acid substitutions on corin function. We found that corin frizzled-like domain 2, where T555I/Q568P substitutions occur, was required for efficient pro-ANP processing in functional assays. Mutant corin lacking this domain had 30+/-5% (P<0.01) activity compared to that of wild type. Similarly, corin variant T555I/Q568P had a reduced (38+/-7%, P<0.01) pro-ANP processing activity compared to that of wild type. The variant also exhibited a low activity (44+/-15%, P<0.05) in processing pro-brain natriuretic peptide (BNP). We next examined the biochemical basis for the loss of activity in T555I/Q568P variant and found that the zymogen activation of the corin variant was impaired significantly, as indicated by the absence of the activated protease domain fragment. This finding was confirmed in human embryonic kidney (HEK)293 cells and murine HL-1 cardiomyocytes. Thus, our results show that the corin gene SNPs associated with hypertension and cardiac hypertrophy impair corin zymogen activation and natriuretic peptide processing activity. Our data suggest that corin deficiency may be an important mechanism in hypertensive and heart diseases.

Tracking of blood pressure from childhood to adulthood: a systematic review and meta-regression analysis

BACKGROUND

A large number of studies have examined the tracking of blood pressure (BP) from childhood to adulthood, but the reported findings are inconsistent and few systematic analyses have been conducted.

METHODS AND RESULTS

We conducted a systematic search of PubMed for studies that examined the tracking of BP from childhood to adulthood published between January 1970 and July 2006. From 301 retrieved papers, 50 cohort studies met our inclusion criteria and provided 617 data points (Pearson/Spearman correlation coefficients) for systolic BP (SBP) and 547 data points for diastolic BP (DBP) for our meta-analysis. Information on sample characteristics and BP measurement protocols was extracted. Fisher z transformation and random-effects meta-regression analysis were conducted. The reported BP tracking correlation coefficients varied from -0.12 to 0.80 for SBP and from -0.16 to 0.70 for DBP, with an average of 0.38 for SBP and 0.28 for DBP. BP tracking varied significantly by baseline age and length of follow-up. The strength of BP tracking increased with baseline age by 0.012 for SBP (P<0.001) and 0.009 for DBP (P<0.001) and decreased with follow-up length by 0.008 for SBP (P<0.001) and 0.005 for DBP (P<0.001). BP tracking did not vary markedly across the number of BP measurements or race/population groups.

CONCLUSIONS

Data from diverse populations show that the evidence for BP tracking from childhood into adulthood is strong. Childhood BP is associated with BP in later life, and early intervention is important.

High blood pressure in school children: prevalence and risk factors

Background

The purpose of this study was to determine the prevalence of high blood pressure (HBP) and associated risk factors in school children 8 to 13 years of age.

Methods

Elementary school children (n = 1,066) were examined. Associations between HBP, body mass index (BMI), gender, ethnicity, and acanthosis nigricans (AN) were investigated using a school based cross-sectional study. Blood pressure was measured and the 95^th percentile was used to determine HBP. Comparisons between children with and without HBP were utilized. The crude and multiple logistic regression adjusted odds ratios were used as measures of association.

Results

Females, Hispanics, overweight children, and children with AN had an increased likelihood of HBP. Overweight children (BMI ≥ 85^th percentile) and those with AN were at least twice as likely to present with HBP after controlling for confounding factors.

Conclusion

Twenty one percent of school children had HBP, especially the prevalence was higher among the overweight and Hispanic group. The association identified here can be used as independent markers for increased likelihood of HBP in children.

Hypertension in young children and neonates

Hypertension is most often considered a disease of old age, but the precursors are often present in young children long before the clinically accepted definitions of hypertension in the adult are manifested. Essential hypertension is by far the most common form of the disease, comprising a complex interaction of genetic and environmental factors. Many individual genes that play a role in the maintenance of blood pressure have been identified; however, none has been shown specifically to be a component of essential hypertension. Hypertension is among the leading risk factors for coronary heart disease, stroke, and end-stage renal disease, making it critically important to identify individuals at risk early in life prior to manifestation of clinical signs and symptoms.

The change in blood pressure during pubertal growth

Blood pressure (BP) in children may increase more during puberty. Using a cohort of children where BP and body size had been closely monitored, we compared the rates of change in BP during the 3-yr period before puberty, during puberty ( approximately 4.5-yr period), and the 3-yr period after puberty. Because there was no specific staging information with respect to puberty, we used pubertal growth (PG) as a surrogate of puberty. The latter was determined from serial measurements of height. All subjects (n = 151) were followed from before the period of PG to the period after PG; none were related. An age-dependent increase in systolic BP in the pre-PG period was similar regardless of sex or race. During PG, systolic BP in males increased three to six times faster than in the pre-PG period. In females, systolic BP increased less than in males during PG but still increased two to four times faster than in the pre-PG period. The increase in males was significantly greater than in females (P < 0.001). Post-PG changes in BP were similar to changes in pre-PG BP. In summary, PG was associated with profound increases in systolic BP. There were noticeably greater increments in males than in females consistent with the emergence of the well known sexual dimorphism in BP.

Ethnicity and tracking blood pressure in children

There is growing evidence that hypertension, one of the major modifiable risk factors for cardiovascular disease (CVD), is established early in life. Given this, it is important to discover when hypertension first becomes apparent. Further, it is of particular importance to examine the ethnic differences in blood pressure (BP) in children, given the variation in rates of CVD morbidity and mortality among adults from different ethnic groups.

Do variations in blood pressures of South Asian, African and Chinese descent children reflect those of the adult populations in the UK? A review of cross-sectional data

The objective of this study was to assess whether variations in BP in children of UK ethnic minority populations correspond to those seen in adults. A systematic literature review was carried out using MEDLINE 1966-2003 and EMBASE 1980-2003, supplemented by correspondence with expert informants, and citations from references. Five studies were identified. There were important differences between studies in terms of age and sex of samples, definition of ethnic minority children and methods of evaluating BP. Three studies of children of African descent reported lower mean SBP in boys from African descent compared to white boys, the differences being significant only in one study. In African descent girls, the mean SBP was significantly lower in one study, while DBP was significantly higher in one study. Four studies included children of South Asian origin. The Health Survey for England '99 reported on South Asian groups separately. Pakistani boys had a significantly higher age- and height-standardised mean SBP than the general population. The mean DBP was significantly higher in Indian and Pakistani boys than the general population. Pakistani and Bangladeshi girls had a significantly higher mean DBP than the general population. The other three studies, which combined South Asian subgroups found no significant differences in the mean BP between South Asians and white subjects. One study included children of Chinese descent and reported significantly higher mean DBP in Chinese boys and girls compared to the general population. Overall, BP across ethnic groups was similar. These similarities in BP patterns particularly in African, Bangladeshi and Pakistani descent children contrasts with those in the corresponding adult populations in the UK where BP is comparatively high in those of African descent and comparatively low in those of Bangladeshi and Pakistani descent.

Heritability of blood pressure and hemodynamics in African- and European-American youth

Hypertension prevalence is much higher in African-Americans (AAs) than in European-Americans (EAs). It is unknown whether this difference is related to potential ethnic differences in the relative contribution of genes and environment to population variation in blood pressure and underlying hemodynamics. We studied 308 EA and 226 AA twin pairs, including monozygotic and dizygotic twins, of the same as well as the opposite sex (mean+/-SD age, 14.7+/-3.1 years). Supine resting systolic blood pressure (SBP), diastolic blood pressure (DBP), pulse pressure, and heart rate (HR) were measured by a Dinamap instrument and hemodynamics (stroke volume, cardiac index, and total peripheral resistance [TPR] index) by impedance cardiography. Ethnic and sex effects on genetic and environmental contributions to resting blood pressure and hemodynamics were estimated by genetic model fitting. For most measures, the best-fitting model showed no differences in heritability between AAs and EAs or between males and females, with heritabilities of 0.50 for cardiac index, of 0.64 for HR, and of SBP, pulse pressure, and stroke volume in between. Heritability of DBP was 0.45 in EAs and 0.58 in AAs with no effect of sex. For TPR index in EAs, 46% of the variance could be attributed to familial effects, but no significant distinction could be made between shared environmental and genetic factors. Heritability of TPR index in AAs was 0.51. Adjustment for obesity yielded virtually identical heritabilities. In summary, relative influences of genetic and environmental factors on blood pressure and hemodynamics in AA and EA youth are similar and independent of (genes for) obesity.

Moderators of blood pressure development from childhood to adulthood: a 10-year longitudinal study

OBJECTIVE

To examine the effect of ethnicity on the development of blood pressure (BP) from childhood into early adulthood within the context of height, sex, adiposity, and socioeconomic status (SES).

STUDY DESIGN

Individual growth curves of systolic BP (SBP) and diastolic BP (DBP) were created for 745 black and white male and female youths, with annual assessments over a 10-year period (age range, 4.9-27.5 years).

RESULTS

Blacks had higher SBP levels (P <0.01) than whites, respectively. Moreover, black female subjects showed a greater SBP increase over time (P <.05) than white female subjects. Black male and female subjects also showed higher DBP levels (P <.001) than white male and female subjects, respectively, but the rate of change of DBP did not differ. Ethnic differences in BP trajectories persisted after adjusting for SES and/or changes in height and/or adiposity in both male and female subjects.

CONCLUSIONS

Ethnic differences in SBP become manifest in childhood in girls, in early adolescence in boys, and tend to increase with age. Ethnic differences in DBP become manifest in childhood in both boys and girls and remain stable over time. The ethnic differences cannot be entirely explained by individual differences in SES, growth, or adiposity. Identification of mechanisms responsible for increase of BP in childhood will improve prevention of hypertension in adulthood.

Hypertension prevalence, control and survivorship in an Afro-Caribbean population

OBJECTIVE

To evaluate the prevalence, distribution, awareness, treatment and control of hypertension in an Afro-Caribbean population, and their relationship to 4-year survival. DESIGN Population-based prospective cohort study.

SETTING AND PARTICIPANTS

Simple random sample of Barbados-born citizens (4709 persons; 84% participation), with 4-year follow-up.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Hypertension prevalence, awareness, treatment and control were evaluated at baseline. Four-year cumulative mortality was assessed by the product-limit method and relative risk of mortality by the Cox proportional hazards method.

RESULTS

Mean systolic (SBP) and diastolic (DBP) blood pressure were higher among black than white participants. In the black population, age-specific prevalence of hypertension increased from 32.7% in men and 34.0% in women at 40-49 years of age to 63.4% in men and 85.5% in women at ages 80 years and older, with an overall prevalence of 55.4%. Hypertension awareness, treatment and control rates were 62.5, 53.8 and 18.5%, respectively. Compared to DBP 80 mmHg, the presence of a DBP between 80 and 84 mmHg, 100-109 mmHg and > or = 110 mmHg was associated with adjusted death rate ratios of 1.6, 1.7 and 2.0, respectively. Systolic blood pressure was not related to the risk of cardiovascular mortality, after adjustment for age or other potential confounders. Hypertensives were at modestly increased risk of 4-year cardiovascular mortality [RR = 1.4; 95% confidence inteval (CI) (1.0, 2.0)], while treated uncontrolled hypertensives were at increased risk of all cause [RR = 1.4; 95% CI (1.0, 1.9)] and cardiovascular [RR = 1.6; 95% CI (1.1, 2.5)] mortality.

CONCLUSIONS

High rates of hypertension in this population coexist with conservative levels of treatment and low rates of blood pressure control. In contrast to other reports, elevated SBP was not independently associated with increased risk of cardiovascular mortality. The modest impact of elevated blood pressure might partly explain the comparatively lower hypertension-related mortality rates in populations of Caribbean-origin. Treated uncontrolled hypertensives are at increased risk of early mortality, signaling the need for strict blood pressure control in this group.

Racial difference in the activity of the amiloride-sensitive epithelial sodium channel

Compared with whites, blacks appear to retain additional sodium that suppresses secretion of renin and aldosterone. The epithelial sodium channel (ENaC) is an aldosterone-regulated site for sodium reabsorption. ENaC activity could be higher in blacks, contributing to sodium retention or, alternatively, lower because of reduced stimulation by aldosterone. To examine the level of ENaC activity in blacks relative to whites, blood pressure (BP) responses to amiloride (5 mg/d), an inhibitor of ENaC, were measured in 20 black and 25 white normotensive young people. After 1 week, systolic BP decreased by 3.0+/-9.2 (SD) and diastolic by 2.8+/-8.3 mm Hg in the whites, whereas systolic BP increased by 2.5+/-7.1 and diastolic by 3.8+/-8.0 mm Hg in the blacks; the racial difference in the BP response was significant for both systolic (P=0.034) and diastolic BP (P=0.010). As ENaC activity increases, renal secretion of potassium increases proportionately, and in a larger sample of subjects, the urinary potassium excretion rate was lower in the blacks (n=301) than in the whites (n=461): 3.2+/-0.1 versus 3.8+/-0.1 mmol/mmol creatinine (P=0.0001). The concentration of serum potassium was higher in the blacks (n=81) than in the whites (n=167): 4.36+/-0.05 versus 4.21+/-0.03 (P=0.012). In summary, a favorable BP response to amiloride in the whites as well as the evidence for greater retention of potassium in the blacks is consistent with blacks having less ENaC activity than whites. We suggest that increased sodium retention in blacks occurring at other nephron sites suppresses aldosterone secretion and in turn ENaC function.

Angiotensinogen gene polymorphism at -217 affects basal promoter activity and is associated with hypertension in African-Americans

Hypertension is a serious health problem in Western society, in particular for the African-American population. Although previous studies have suggested that the angiotensinogen (AGT) gene locus is involved in human essential hypertension, the molecular mechanisms involved in hypertension in African-Americans remain unknown. We show that an A/G polymorphism at -217 in the promoter of the AGT gene plays a significant role in hypertension in African-Americans. The frequency of the -217A allele was increased significantly in African-American hypertensive subjects compared with normotensive controls. We also show that the nucleotide sequence of this region of the AGT gene promoter bound strongly to CAAT/enhancer-binding protein (C/EBP) family transcription factors when nucleoside A was present at -217. In addition, we show that reporter constructs containing the human AGT gene promoter with nucleoside A at -217 had increased basal transcriptional activity upon transient transfection in HepG2 cells compared with reporter constructs with nucleoside G at -217. Finally, we show that interleukin-6 treatment in the presence or absence of overexpressed C/EBPbeta increased the promoter activities of reporter constructs containing nucleoside A at -217 compared with reporter constructs containing nucleoside G at -217. Because the AGT gene is expressed primarily in liver and adipose tissue, and C/EBP family transcription factors play an important role in gene expression in these tissues, we propose that increased transcriptional activity of the -217A allele of the human AGT gene is associated with hypertension in African-Americans.

Socioeconomic disadvantage and change in blood pressure associated with aging

BACKGROUND

Few studies have examined how the longitudinal change in blood pressure associated with aging differs across social groups within industrialized countries.

METHODS AND RESULTS

Data from the Atherosclerosis Risk In Communities Study were used to investigate differences in the incidence of hypertension and in aging-related changes in blood pressure by neighborhood and individual socioeconomic factors over a 9-year follow-up. Disadvantage in multiple socioeconomic dimensions was associated with the greatest risk of developing hypertension (age- and sex-adjusted hazard ratio [HR] and 95% CI: HR 1.95, 95% CI 1.38 to 2.75 in whites and HR 1.43, 95% CI 0.96 to 2.13 in blacks). Aging-related increases in systolic blood pressure were inversely associated with socioeconomic position in whites (mean [SEM] 5-year increase in systolic blood pressure 7 [0.7] mm Hg in the most disadvantaged category and 5.4 [0.4] mm Hg in the most advantaged category). In whites, low socioeconomic position was also associated with more rapid declines in diastolic blood pressure after 50 years of age. Socioeconomic differences in hypertension incidence and changes in systolic blood pressure were reduced after adjustment for baseline blood pressure.

CONCLUSION

The change in blood pressure associated with aging varies by social groups within the United States.

The magnitude of familial associations of cardiovascular risk factor variables between parents and offspring are influenced by age: the Bogalusa Heart Study

PURPOSE

Although parent-offspring associations of cardiovascular risk factor variables are known, the age-specific nature of this familial relationship is not clear.

METHODS

This aspect was examined in 727 unrelated children (mean age: 11.2 years) and their parents who participated in the Bogalusa Heart Study during their childhood (mean age: 11.3 years) and adulthood (mean age: 25.5 years).

RESULTS

After adjusting for covariates, the mothers' childhood-offspring correlations were consistently higher than mothers' adulthood-offspring correlations for body mass index (BMI) [r = 0.45 vs. 0.32], systolic blood pressure (SBP) [r = 0.30 vs. 0.10], diastolic blood pressure (DPB) [r = 0.22 vs. 0.13] and low-density lipoprotein cholesterol (LDLC) [r = 0.20 vs. 0.11]. In contrast, high-density lipoprotein cholesterol (HDLC) and triglycerides did not show such age-specific trends in mother-offspring correlations. Corresponding father-offspring correlations showed similar patterns, but the differences were of lesser magnitude. Multiple regression analyses using offspring's risk factor variables as dependent variables revealed that parents' childhood obesity, blood pressure and LDLC levels were better predictors of the corresponding variables in the young offspring than parents' adulthood values. Further, sex of either parents or offspring made no difference in the above findings.

CONCLUSIONS

The magnitude of the familial associations of cardiovascular risk factor variables between parents and offspring are influenced by age. Intrinsic genetic make-up, duration of exposure to environment and gene-environment interactions may play a role in this association.

Blood pressure responses to small doses of amiloride and spironolactone in normotensive subjects

The epithelial sodium channel (ENaC) is a principal site for sodium reabsorption and as such may participate importantly in blood pressure (BP) regulation. Amiloride, a direct inhibitor of ENaC, characteristically has mild antihypertensive properties, consistent with ENaC having more minor influences on BP regulation. Counter-regulatory influences may, however, prevent amiloride from effectively lowering BP. Aldosterone secretion is known to increase in response to the reduced sodium reabsorption that follows amiloride inhibition of ENaC, and because aldosterone upregulates ENaC function, we considered the possibility that secondary hyperaldosteronism mitigates the ability of amiloride to reduce BP. In the present study, the BP responses to amiloride (5 mg per day), spironolactone (25 mg per day), the combination of the 2 drugs, and placebo were studied in healthy normotensive subjects. Over 4 weeks of treatment, the combination of amiloride and spironolactone lowered systolic BP by 4.6+/-1.6 (mean+/-SEM) mm Hg (P=0.022) and diastolic BP by 2.2+/-1.2 mm Hg (P=0.30), whereas either drug alone had no significant effect on BP. The findings suggest that the 2 drugs with different modes of action-amiloride, a direct inhibitor of ENaC, and spironolactone, a mineralocorticoid receptor antagonist-may compliment each other's ability to inhibit ENaC and thereby reduce sodium reabsorption to a point at which BP decreases. On the other hand, we cannot rule out that the BP response resulted from the greater dose of total drug. The lowering of BP with small doses of inhibitors of ENaC serves as additional evidence for the importance of ENaC to the tonic maintenance of BP.

Blood pressure and sexual maturity in adolescents: the Heartfelt Study

This study investigates sexual maturity as a predictor of resting blood pressures independent of other known predictors, in 179 boys and 204 girls 11-16 years of age from the Heartfelt Study. The sample included youth of African (n = 140), Mexican (n = 117), and European and "other" (n = 126) backgrounds. Sexual maturity was assessed during clinical examination of three standard indicators for each sex. Systolic and diastolic blood pressures were higher in children of maturity stages IV and V, compared to stages I-III, in each gender/ethnic group (P < 0.01 in almost all groups). Boys and girls advanced in sexual maturity for their age group, had significantly higher systolic blood pressures (but not diastolic) than the less advanced in linear models that included height, body mass index (BMI), ethnicity, and age as co-predictors. Diastolic blood pressures were predicted by height in boys and by age and the BMI in girls. This analysis, using a very conservative approach, suggests that sexual maturity provides important and independent information on systolic blood pressure in adolescents. Further investigation of its role in 24-hr blood pressures and in blood pressures taken during physical and emotional stress, is recommended.

Genetic determinants of homocysteine thiolactonase activity in humans: implications for atherosclerosis

A metabolite of homocysteine (Hcy), the thioester Hcy thiolactone, damages proteins by modifying their lysine residues which may underlie Hcy-associated cardiovascular disease in humans. A protein component of high density lipoprotein, Hcy thiolactonase (HTase) hydrolyzes thiolactone to Hcy. Thiolactonase is a product of the polymorphic PON1 gene, also involved in detoxification of organophospates and implicated in cardiovascular disease. Polymorphism in PON1 affects the detoxifying activity of PON1 in a substrate-dependent manner. However, how PON1 polymorphism affects HTase activity is unknown. Here we report a strong association between the thiolactonase activity and PON1 genotype in human populations. High thiolactonase activity was associated with L55 and R192 alleles, more frequent in blacks than in whites. Low thiolactonase activity was associated with M55 and Q192 alleles, more frequent in whites than in blacks. High thiolactonase activity afforded better protection against protein homocysteinylation than low thiolactonase activity. These results suggest that variations in HTase may play a role in Hcy-associated cardiovascular disease.

Obesity in the pediatric patient: cardiovascular complications

The prevalence and severity of obesity are increasing in children and adolescents. This raises concerns about the accompanying cardiovascular complications. Such complications include hypertension, dyslipidemia, type II diabetes which may accelerate vascular disease, left ventricular hypertrophy and pulmonary hypertension due to obstructive sleep apnea. The evaluation of an obese child or adolescent should include careful consideration of these possible cardiovascular complications. If they are present, treatment should be directed at both obesity and the risk factor abnormality. This treatment may be important for prevention of future cardiovascular morbidity and mortality. In addition, research is necessary to better understand the mechanisms by which obesity increases the risk of cardiovascular disease.

Is greater tissue activity of creatine kinase the genetic factor increasing hypertension risk in black people of sub-Saharan African descent?

We postulate that the genetic factor increasing the propensity of black people of sub-Saharan African descent to develop high blood pressure is the relatively high activity of creatine kinase, predominantly in vascular and cardiac muscle tissue. Such greater activity of creatine kinase has been reported in skeletal muscle of black untrained subjects has been reported to be almost twice the activity found in white subjects. Creatine kinase, a key enzyme of cellular energy metabolism, increases the capacity of the cell to function under high demands. The enzyme regulates, buffers and transports, via phosphocreatine and creatine, energy produced by glycolysis and oxidative phosphorylation to sites of energy consumption such as myofibrils and membrane ion pumps. At these cellular locations, it is involved in the contraction process and active trans- membranous transport by readily providing the ATP needed for these processes. In addition, creatine kinase is increasingly reported to be involved in trophic responses. Furthermore, by using H+ and ADP to synthesize ATP, creatine kinase prevents acidification of the cell, providing relative protection against the effects of ischaemia. Greater creatine kinase activity in cardiovascular muscle and other tissues with high energy demands could increase cardiovascular contractile reserve, enhance trophic responses and increase renal tubular ability to retain salt. This could facilitate the development of arterial hypertension under chronic provocative circumstances, with higher mean blood pressures, more left ventricular hypertrophy and relatively fewer ischaemic events. Therefore, greater cellular activity of creatine kinase might explain the greater hypertension risk and the clinical characteristics of hypertensive disease observed in the black population.