Ethnicity, pressor reactivity, and children's blood pressure. Five years of observations

Disparities in Hypertension Among African-Americans: Implications of Insufficient Sleep

PURPOSE OF REVIEW

Sleep deficiency has been proposed as a potential contributor to racial disparities in cardiovascular health. We present contemporary evidence on the unequal burden of insufficient sleep in Blacks/African-Americans and the repercussions for disparate risk of hypertension.

RECENT FINDINGS

The prevalence of insufficient sleep is high and rising and has been recognized as an important cardiovascular risk factor. Presumably due to a constellation of environmental, psychosocial, and individual determinants, these risks appear exacerbated in Blacks/African-Americans, who are more likely to experience short sleep than other ethnic/racial groups. Population-based data suggest that the risk of hypertension associated with sleep deficiency is greater in those of African ancestry. However, there is a paucity of experimental evidence linking short sleep duration to blood pressure levels in African-Americans. Blacks/African-Americans may be more vulnerable to sleep deficiency and to its hypertensive effects. Future research is needed to unequivocally establish causality and determine the mechanism underlying the postulated racial inequalities in sleep adequacy and consequent cardiovascular risk.

Recovery from stress: an experimental examination of focused attention meditation in novices

Identifying strategies that aid in recovery from stress may benefit cardiovascular health. Ninety-nine undergraduate meditation novices were randomly assigned to meditate, listen to an audio book, or sit quietly after a standardized stressor. During recovery, meditators' heart rate variability and skin conductance levels returned to baseline, whereas only heart rate variability returned to baseline for the audio book and control groups. Positive and negative affect were no different than baseline following meditation, whereas, both audio book and control groups had lower positive affect and higher negative affect following the intervention. Findings suggest that the sympathetic nervous system is uniquely affected by meditation, and novices may benefit emotionally from meditating after a stressor. Further research is needed to determine meditation's utility in recovering from stress.

Accelerometer-determined physical activity and the cardiovascular response to mental stress in children

OBJECTIVES

Cardiovascular reactivity has been associated with future hypertension and cardiovascular mortality. Higher physical activity (PA) has been associated with lower cardiovascular reactivity in adults, but little data is available in children. The purpose of this study was to examine the relationship between PA and cardiovascular reactivity to mental stress in children.

DESIGN

Cross-sectional study.

METHODS

This study sample included children from the Oswego Lead Study (n=79, 46% female, 9-11 years old). Impedance cardiography was performed while children participated in a stress response protocol. Children were also asked to wear Actigraph accelerometers on their wrists for 3 days to measure intensity and duration of PA and sedentary time.

RESULTS

In multivariable models, moderate to vigorous (MV) PA was associated with lower body mass index (BMI) percentile and lower total peripheral resistance (TPR) response to stress (beta=-0.025, p=0.02; beta=-0.009, p=0.05). After additional adjustment for BMI, MVPA was also associated with lower diastolic blood pressure response to stress (beta=-0.01, p=0.03). Total PA and sedentary time were not associated with BMI or cardiovascular responses to stress.

CONCLUSIONS

A modest, inverse relation of PA to vascular reactivity to mental stress was observed in children. These data provide confirmatory evidence that the promotion of PA recommendations for children are important for cardiovascular health.

Cardiovascular Responses to Conflict Stress in African American Mother-Daughter Dyads

This study evaluated the effect of family conflict interactions on cardiovascular responses of African American hypertensive and normotensive mother-daughter dyads and determined degree of mother-daughter concordance of physiologic response. Sixteen African American hypertensive mothers and 21 African American normotensive mothers and their teenage daughters discussed 2 topics, one involving no conflict and the other involving participant-identified conflict. Differences in blood pressure (BP), both systolic and diastolic, and heart rate (HR) were examined. As expected, hypertensive mothers and their daughters had higher BP levels (responsivity) than did their normotensive counterparts. For mothers, differences were due largely to group differences at baseline. For daughters, differences were due largely to group differences in body mass. BP reactivity (change) did not differ significantly between the groups. Few HR effects were observed. There was moderate BP concordance and low HR concordance. The findings suggest that conflict management and body mass may be important factors to consider among families at risk for hypertension.

Personality traits modulate emotional and physiological responses to stress

An individual's susceptibility to psychological and physical disorders associated with chronic stress exposure, for example, cardiovascular and infectious disease, may also be predicted by their reactivity to acute stress. One factor associated with both stress resilience and health outcomes is personality. An understanding of how personality influences responses to acute stress may shed light upon individual differences in susceptibility to chronic stress-linked disease. This study examined the relationships between personality and acute responses to stress in 125 healthy adults, using hierarchical linear regression. We assessed personality traits using the Multidimensional Personality Questionnaire (MPQ-BF), and responses to acute stress (cortisol, heart rate, blood pressure, mood) using a standardized laboratory psychosocial stress task, the Trier Social Stress Test. Individuals with high Negative Emotionality exhibited greater emotional distress and lower blood pressure responses to the Trier Social Stress Test. Individuals with high agentic Positive Emotionality exhibited prolonged heart rate responses to stress, whereas those with high communal Positive Emotionality exhibited smaller cortisol and blood pressure responses. Separate personality traits differentially predicted emotional, cardiovascular, and cortisol responses to a psychosocial stressor in healthy volunteers. Future research investigating the association of personality with chronic stress-related disease may provide further clues to the relationship between acute stress reactivity and susceptibility to disease.

Regular exercise is associated with emotional resilience to acute stress in healthy adults

Physical activity has long been considered beneficial to health and regular exercise is purported to relieve stress. However empirical evidence demonstrating these effects is limited. In this study, we compared psychophysiological responses to an acute psychosocial stressor between individuals who did, or did not, report regular physical exercise. Healthy men and women (N = 111) participated in two experimental sessions, one with the Trier Social Stress Test (TSST) and one with a non-stressful control task. We measured heart rate, blood pressure, cortisol, and self-reported mood before and at repeated times after the tasks. Individuals who reported physical exercise at least once per week exhibited lower heart rate at rest than non-exercisers, but the groups did not differ in their cardiovascular responses to the TSST. Level of habitual exercise did not influence self-reported mood before the tasks, but non-exercisers reported a greater decline in positive affect after the TSST in comparison to exercisers. These findings provide modest support for claims that regular exercise protects against the negative emotional consequences of stress, and suggest that exercise has beneficial effects in healthy individuals. These findings are limited by their correlational nature, and future prospective controlled studies on the effects of regular exercise on response to acute stress are needed.

Alpha-adrenergic receptor gene polymorphisms and cardiovascular reactivity to stress in Black adolescents and young adults

Cardiovascular reactivity to stress and α-adrenergic receptor (α-AR) function may contribute to the development of hypertension. As Black Americans have an increased risk of hypertension, we evaluated associations between α(1A) -AR (Arg492Cys), α(2A) -AR (-1291C/G), and α(2B) -AR (Ins/Del301-303) gene variants and cardiovascular reactivity in 500 normotensive Black youth. Heart rate, preejection period, total peripheral resistance, and blood pressure were measured during cold and psychological stress. The Arg492Cys polymorphism in the α(1A) -AR gene was associated with heart rate reactivity to stress, but the association depended on sex. The -1291C/G promoter polymorphism in the α(2A) -AR gene was associated with vascular reactivity to stress; vasoconstriction increased as a linear function of the number of copies of the variant G allele. Thus, specific associations emerged between genetic variations in α-Ars and cardiovascular reactivity in young Blacks.

Hemodynamic variables during exercise in childhood and resting systolic blood pressure levels 6 years later in adolescence: the European Youth Heart Study

The aim of this study was to analyze whether systolic blood pressure (SBP), heart rate (HR) and rate pressure product (RPP) during exercise in childhood can predict resting SBP levels in adolescence independent of resting SBP and conventional cardiovascular risk factors. We studied this in a sample of Danish children followed longitudinally for 6 years. The study comprised 226 children randomly sampled at age 9, who had their blood pressure and HR measured during ergometer exercise to exhaustion and was reassessed in adolescence. SBP and RPP during exercise in stage two of the test were positively associated with future resting SBP, independent of resting SBP in childhood (P=0.045 and P=0.013, respectively). After additional adjustment for conventional cardiovascular risk factors the associations with SBP and RPP during stage two on future resting SBP only slightly materially change, although only RPP remained significant (P=0.059 and P=0.012, respectively). No significant independent associations were observed for HR during exercise, but associations were in the same direction. Our results supports that measuring SBP and RPP, during a standard acute ergometer exercise test in children, improves the prediction of future SBP levels during rest in adolescence independent of resting SBP and conventional cardiovascular risk factors.

Beta-adrenergic receptor gene polymorphisms and cardiovascular reactivity to stress in Black adolescents and young adults

Cardiovascular reactivity to stress and beta-adrenergic receptor (beta-AR) function may contribute to the development of hypertension. As Black Americans have an increased risk of hypertension, we evaluated associations between beta(1)-AR (Arg389Gly) and beta(2)-AR (Arg16Gly, Gln27Glu) gene variants and cardiovascular reactivity in 500 Black youth. Heart rate, preejection period, total peripheral resistance, and blood pressure reactivity were measured during cold and psychological stress. The Arg389Gly polymorphism in the beta(1)-AR was associated with preejection period reactivity in males but not in females. The Arg16Gly polymorphism in the beta(2)-AR was associated with diastolic blood pressure reactivity only during video game stress. An association between the Gln27Glu polymorphism in the beta(2)-AR and vascular reactivity depended on sex. Thus, specific patterns of associations emerged between genetic variations in beta-ARs and cardiovascular reactivity in young Blacks.

A longitudinal study in youth of heart rate variability at rest and in response to stress

BACKGROUND

Few longitudinal studies have examined ethnic and sex differences, predictors and tracking stabilities of heart rate variability (HRV) at rest and in response to stress in youths and young adults.

METHODS

Two evaluations were performed approximately 1.5 years apart on 399 youths and young adults (189 European Americans [EAs] and 210 African Americans [AAs]; 190 males and 209 females). HRV was measured at rest and during a video game challenge.

RESULTS

AAs showed significantly higher resting root mean square of successive differences (RMSSD) of normal R-R intervals and high-frequency (HF) power than EAs (ps<0.01). Females displayed larger decrease of RMSSD and HF during video game challenge than males (ps<0.05). These ethnic and sex differences were consistent across 1.5 years. No significant sex difference of resting HRV or ethnic difference of HRV response to stress was observed. In addition to age, ethnicity or sex, baseline resting HRV or HRV response to stress are predictors of the corresponding variables 1.5 years later (ps<0.01). Furthermore, weight gain indexed by either body mass index or waist circumference predicts declined resting HRV levels during follow up (ps<0.05). Tracking stabilities were high (>0.5) for resting HRV, but relatively low (<0.3) for HRV in response to stress.

CONCLUSION

AAs show higher resting HRV than EAs, and females display greater HRV response to stress than males; and these ethnic and sex differences are consistent across 1.5 years. Resting HRV declines with weight gain.

Genetic influences on heart rate variability at rest and during stress

We tested whether the heritability of heart rate variability (HRV) under stress is different from rest and its dependency on ethnicity or gender. HRV indexed by root mean square of successive differences (RMSSD) and high-frequency (HF) power was measured at rest and during 3 stressors in 427 European and 308 African American twins. No ethnic or gender differences were found for any measures. There was a nonsignificant increase in heritability of RMSSD (from 0.48 to 0.58) and HF (from 0.50 to 0.58) under stress. Up to 81% and 60% of the heritabilities of RMSSD and HF under stress could be attributed to genes influencing rest levels. The heritabilities due to genes expressed under stress were 0.11 for RMSSD and 0.23 for HF. The findings suggest that, independent of ethnicity and gender, HRV regulation at rest and under stress is largely influenced by the same genes with a small but significant contribution of stress-specific genetic effects.

Cardiovascular effects in adolescents while they are playing video games: a potential health risk factor?

We analyzed heart rate (HR), systolic and diastolic blood pressure (SBP, DBP), oxygen consumption, and carbon dioxide production in 17 male adolescents during a racing simulation video game (VG) and compared to resting state (RS) and exercise testing (ET) measures. We were able to demonstrate a significant (p<.005) increase from RS to VG concerning HR (+13.1 bpm), SBP (+20.8 mmHg), and DBP (+12.1 mmHg) with SBP and DBP elevations exceeding 2 SD in all children and 14/17 children, respectively. The energy consumption during VG (max 1.71 kcal/min) was unaltered compared to RS and significantly lower compared to ET even at the starting strain of 25 W (1.94 kcal/min). Hemodynamic parameters tested demonstrated lower HR, unchanged SBP, and higher DBP during the VG compared with ET. Comparing all measured parameters it can be said that the relation of blood pressure and energy consumption during VG might not be favorable.

Longitudinal relationship of parental hypertension with body mass index, blood pressure, and cardiovascular reactivity in children

OBJECTIVE

To investigate whether parental hypertension (HTN) affects children's body mass index (BMI) and cardiovascular reactivity (CVR) over time.

STUDY DESIGN

A longitudinal study of 315 students (black: 23 females, 19 males; white: 142 females, 131 males) was conducted in the public schools of Obion County, Tennessee, between 1987 and 1992. BMI and BMI z scores were calculated. The CVR task was a series of video games (taking approximately 10 minutes to play) given to the same students in their third-, fourth-, fifth-, seventh-, and eighth-grade years. CVR was defined as the change in blood pressure (delta_BP) or heart rate (delta_HR) between before playing and while playing the video game. Positive parental history of HTN (27.6%) was defined as at least 1 parent with HTN. Multivariable regression analyses were performed to estimate the effects of parental HTN on children's BMI and CVR over time.

RESULTS

Children with parental HTN had significant higher BMI, BMI z score, and R_BP than did children without parental HTN (BMI: 21.6 vs 19.9, P = .001; BMI z score: 1.6 vs 1.1, P = .003; R_SBP: 112.6 vs 110.4 mm Hg, P = .01; R_DBP 62.7 vs 60.6 mm Hg, P = .003) after adjustment for covariates. Increased CVR was observed in children with parental HTN compared with children without parental HTN but was statistically significant only for SBP (delta_SBP: 17.2 vs 14.9 mm Hg; P = .01) after adjustment for covariates.

CONCLUSIONS

Parental HTN independently predicted children's BMI, BMI z score, resting BP, and BP reactivity.

Cardiovascular reactivity in cardiovascular disease: "once more unto the breach"

Discussed here are conceptual and methodologic issues that bear on the role of behaviorally evoked cardiovascular reactivity in cardiovascular disease. It is argued that recent criticisms concerning the validity of cardiovascular reactivity as a stable dimension of individual differences arise from inadequacies of measurement prevalent in prior literature. With standardization of test stimuli and application of psychometric principles lo protocol development, assessment of reactivity are found to be highly reliable and, in turn, to demonstrate the dispositional nature of this construct. Recent studies also document an underlying heterogeneity of hemodynamic reactions to stress, with distinct cardiac and vascular components. Because hemodynamic adjustments show some plasticity under differing task conditions, responses seen in particular contexts reflect influences of both an individual-specific response potential and response-eliciting properties of the stimulus. On the question of disease relevance, it is concluded that cardiovascular reactivity cannot yet be considered an established risk factor for either coronary heart disease or hypertension. However, the preponderance of existing clinical, experimental. and epidemiologic evidence is consistent with such an association and warrants further study in the context or population-based, prospective investigation.

Association between smoking status and cardiovascular and cortisol stress responsivity in healthy young men

Acutely, cigarette smoking stimulates increases in blood pressure (BP), heart rate (HR), and cortisol, but little evidence is available concerning the impact of habitual smoking status on cardiovascular stress responsivity. This relation was assessed in 86 healthy male firefighters, age 19 to 31. comprising 52 nonsmokers and 34 smokers. Measures of BP, HR, salivary free cortisol, breathing pattern, and self-reported stress and alertness were obtained while subjects performed nonverbal mental arithmetic and a socially evaluative speech task. Systolic and diastolic BP were higher at rest in nonsmokers than smokers, and a consistent difference in stress responsivity was also found. BP, HR, and cortisol responses to mental arithmetic were significantly smaller in smokers than nonsmokers, with mean changes in BP (adjusted for body weight) averaging 19.3/11.0 mmHg and 28.5/15.4 mmHg in smokers and nonsmokers, respectively. There were no effects of smoking status on task performance or subjective stress responses and no differences between groups in family health history, health-related behaviors, o r psychological characteristics that might account for the reactivity difference. Possible explanations of the results are discussed, and methodological implications for cardiovascular stress reactivity studies are outlined.

Psychological Stress Tasks in the Prediction of Blood Pressure Level and Need for Antihypertensive Medication: 9-12 Years of Follow-Up

Increased blood pressure (BP) reactivity to subtypes of psychological stimuli may differentially predict the development of future BP elevation or hypertension. The authors present the 9-12-year follow-up results of 82 (86%) of 95 male participants with different BP levels. They were healthy, untreated, and age-matched volunteers from a routine health checkup carried out on all 35-, 40-, and 45-year-olds from a medium-sized city. Intra-arterial systolic blood pressure (SBP) during the psychological tasks improved the prediction of future casual SBP and noninvasive 24-hr ambulatory SBP compared with predictions from casual diagnostic measurements. Diastolic blood pressure (DBP) was very useful when added to casual DBP in predicting the need for antihypertensive medication. Reactivity to active tasks especially predicts the need for antihypertensive medication.

Parental history of hypertension and coping responses predict blood pressure changes in black college volunteers undergoing a speaking task about perceptions of racism

OBJECTIVE

This investigation explored the relationship of coping responses and parental history of hypertension to task-induced blood pressure changes.

MATERIALS AND METHODS

The sample consisted of 215 black college student volunteers (median age = 25.95 y). During the speaking task, participants responded to standardized questions about perceptions of intra-ethnic and inter-ethnic group racism. Systolic blood pressure and diastolic blood pressure were measured via an automated blood pressure monitor. Usual ways of coping with intra-ethnic group racism were assessed with the COPE Scale, and parental history of hypertension (PHH) was self-reported by participants.

RESULTS

Findings from the final step of hierarchical general linear models indicated that the main effect of emotion-focused coping was negatively associated with diastolic blood pressure (p = 0.02) and systolic blood pressure (p = 0.002) changes. Further, these analyses revealed that PHH interacted: (1) with the coping responses of planning (p = 0.007) and denial (p = 0.002) to predict changes in systolic blood pressure and (2) with the planning coping response to predict diastolic blood pressure changes (p = 0.02). The direction of these effects indicated that among participants who were high in these coping responses, participants who also had a positive PHH had larger blood pressure changes. Regression analyses also revealed that PHH interacted with the cognitive coping response (p = 0.01) to predict changes in systolic blood pressure. The direction of this effect indicated that among participants who were low in this coping response, participants who also had a positive PHH had larger systolic blood pressure changes.

CONCLUSION

This study highlights the importance of examining the joint contribution of biological and psychosocial parameters to blood pressure reactivity in blacks.

Allelic variation in the serotonin transporter gene-linked polymorphic region (5-HTTLPR) and cardiovascular reactivity in young adult male and female twins of European-American descent

OBJECTIVE

To examine the effect of length variation in the serotonin transporter gene-linked polymorphic region (5-HTTLPR) on individual differences in cardiovascular response to psychological challenge.

METHODS

Heart rate (HR) and systolic and diastolic blood pressure (SBP, DBP) responses to computerized versions of two psychological challenges, the Stroop Color-Word Interference Test and mental arithmetic, were measured among 131 monozygotic (MZ) and 60 dizygotic (DZ) male or female (same-sex) European-American twin pairs. Among the 382 participants, 140 were homozygous for the "long" allele (l/l) at 5-HTTLPR, 61 were homozygous for the "short" allele (s/s), and 181 participants had one long and one short allele (l/s). Association and sib-pair analyses were performed to characterize genetic associations.

RESULTS

In the full sample, 5-HTTLPR was associated with HR reactivity to psychological challenge, albeit in interaction with sex. Task-elicited HR responses of women homozygous for the short allele were significantly greater than among: a) men of the same genotype; and b) women having either one (l/s) or two (l/l) long alleles at 5-HTTLPR. SBP and DBP responsivity was unrelated to genotype. These results were corroborated on reanalysis in two genetically independent subsamples. Variability at 5-HTTLPR also predicted HR reactivity in sib-pair analyses among DZ twins.

CONCLUSIONS

These results suggest that the commonly observed sex difference in HR reactivity may be, in part, genetically mediated and perhaps occur only among individuals homozygous for the short allele at 5-HTTLPR.

Positional change in blood pressure and 8-year risk of hypertension: the CARDIA Study

OBJECTIVE

To assess the relationship between positional blood pressure change and 8-year incidence of hypertension in a biracial cohort of young adults.

SUBJECTS AND METHODS

Participants from the Coronary Artery Risk Development in Young Adults (CARDIA) study with complete data from year 2 (1987-1988), year 5 (1990-1991), year 7 (1992-1993), and year 10 (1995-1996) examinations were included (N = 2781). Participants were classified into 3 groups based on their year 2 systolic blood pressure response to standing: drop, a decrease in systolic blood pressure of more than 5 mm Hg; same, a change of between -5 and +5 mm Hg; and rise, more than 5-mm Hg increase.

RESULTS

The number of participants in each group was as follows: drop, 741; same, 1590; and rise, 450. The 8-year incidence of hypertension was 8.4% in the drop group, 6.8% in the same group, and 12.4% in the rise group (P < .001). Adjusted odds ratios for developing hypertension during the follow-up period in the rise group vs the same group were as follows: in black men, 2.85 (95% confidence interval [CI], 1.43-5.69), in black women, 2.47 (95% CI, 1.19-5.11), in white men, 2.17 (95% CI, 1.00-4.73), and in white women, 4.74 (95% CI, 1.11-20.30).

CONCLUSIONS

A greater than 5-mm Hg increase in blood pressure on standing identified a group of young adults at increased risk of developing hypertension within 8 years. These findings support a physiologic link between sympathetic nervous system reactivity and risk of hypertension in young adults.

Blood pressure reactivity to mental stress task as a determinant of sustained hypertension after 5 years of follow-up

Previous studies have reported an increased risk of developing sustained hypertension (SH) in borderline or mildly hypertensive subjects showing an exaggerated response of blood pressure (BP) to mental stress. The aim of this study was to assess if the response of BP to mental stress tasks is an independent predictor of SH. A total of 89 patients with grade 1 hypertension, aged 18-64 years, 62% males, were included. The mean of follow-up was 5.3 years (s.d. 2.1 years). SH was defined as the development of grades 2-3 hypertension (Systolic BP>or=160 mmHg or diastolic BP>or=100 mmHg) or to be in antihypertensive treatment after follow-up. Two mental stress tasks: mental arithmetic stress task and a stressful interview (SI) were applied at entry. The subjects were classified as hyper-reactors when BP increase was greater than 35 mmHg for systolic BP or greater than 21 mmHg for diastolic BP, according to the results obtained previously in a normotensive control group. In the univariate analysis, the factors associated with the development of SH were age (P=0.0007), office diastolic BP (P=0.014) and hyper-reactivity of BP during a stressful interview (P=0.003). In the Cox regression model, after adjusting for gender, age, and office BP, the hyper-reactivity of BP during SI was an independent predictor of development of SH. In conclusion, the response of BP to mental stress tasks is useful in predicting SH in young and middle-aged subjects with grade 1 hypertension.

Cardiovascular reactivity and development of preclinical and clinical disease states

OBJECTIVE

The objective of this review is to evaluate the evidence for the hypothesis that cardiovascular reactivity can predict the development of preclinical (elevated blood pressure, ventricular remodeling, carotid atherosclerosis) and/or clinical cardiovascular disease states.

METHODS

A review of the literature was conducted examining prospective studies.

RESULTS

Three large epidemiological studies with long-term follow-up periods (20 years or more) have found blood pressure responses to the cold pressor task to be predictive of subsequent essential hypertension in initially normotensive samples. Studies showing less consistent results have tended to use shorter-term follow-up periods. A larger body of literature demonstrates consistent associations between stress-related cardiovascular reactivity and blood pressure elevations in youth over the course of 1 to 6 years; such relationships have not been consistently shown among adult samples. Moderately consistent evidence points to a positive relationship between reactivity and other measures of subclinical disease (increased left ventricular mass and carotid atherosclerosis) among the few prospective studies that have examined these issues to date. A number of additional factors, however, such as baseline levels of disease risk and exposure to psychosocial stress, seem to moderate these relationships. Health status at baseline also seems to moderate the association between reactivity and clinical coronary heart disease in recent reports: two of three existing studies in initially healthy samples show no evidence of a relationship between reactivity and clinical outcomes, whereas three of four studies in samples with preexisting coronary heart disease or essential hypertension show a positive relationship between reactivity and subsequent disease states.

CONCLUSIONS

There is reasonable evidence to suggest that cardiovascular reactivity can predict the development of some preclinical states (eg, increased left ventricular mass and blood pressure) states and perhaps even new clinical events in some patients with essential hypertension or coronary heart disease. However, much more information is needed concerning moderating and potentially confounding variables before the robustness of the positive relationships can become clinically useful.

Variability within alpha- and beta-adrenoreceptor genes as a predictor of cardiovascular function at rest and in response to mental challenge

OBJECTIVES

To investigate the association between polymorphic variation in alpha- and beta-adrenoreceptor genes and cardiovascular activity at rest and in response to psychological challenge in a sample in which the heritability of these cardiovascular phenotypes may be established.

METHODS

Several common polymorphisms were characterized within ADRA1B (alpha1B), ADRA2A (alpha2A), ADRB1 (beta1) and ADRB2 (beta2) and examined in relation to heart rate (HR) and systolic (SBP) and diastolic (DBP) blood pressure, both at rest and in response to stress. Participants were 309 European-American, young adult men and women (including 101 monozygotic and 44 dizygotic twin pairs).

RESULTS

In the full sample, participants carrying any G allele at base pair (bp) 1165 in ADRB1 exhibited elevated resting SBP and DBP and a larger DBP response to mental challenge compared to homozygotes for the C allele (P < 0.04). An AA genotype at bp 145 in ADRB1 was also associated with higher resting SBP and DBP than AG or GG genotypes (P < 0.03). At bp 46 in ADRB2, GG homozygotes had higher resting DBP than subjects possessing any A allele (P < 0.05). For the same polymorphism, however, AG heterozygotes showed lower SBP than both AA and GG homozygotes (P < 0.05). In a subsample of genetically unrelated individuals, ADRB1 (1165) continued to predict resting SBP, DBP and DBP response to stress (P < 0.03), while ADRB2 (46) was associated with resting SBP (P < 0.04) but not DBP. Finally, the degree of allele sharing at ADRB1 (1165) also predicted variability in SBP and DBP at rest among dizygotic twin pairs (P < 0.04).

CONCLUSIONS

These results indicate that some polymorphic variation within adrenoreceptor genes contributes to interindividual variability in resting SBP and DBP and in DBP response to mental challenge.

Isolated systolic hypertension, obesity, and hyperkinetic hemodynamic states in children

OBJECTIVE

To determine the factors that contribute to the pathogenesis of isolated systolic hypertension in children.

METHODS

School-based measurement was performed of blood pressure (BP), heart rate, weight, and height in 2460 students (49% Hispanic, 31% black, 13% white) 12 to 16 years of age in 8 urban public schools. An independent group of 71 untreated children underwent 24-hour ambulatory BP monitoring (ABPM) to confirm clinic hypertension and assess circadian BP patterns.

RESULTS

Hypertension and obesity were found in 17% and 23% of students, respectively. Among hypertensive students, 88% (363/413) had isolated systolic hypertension. Hypertension was more prevalent in obese than nonobese students (33% vs 11%, P <.0001). Obese hypertensive students had higher resting heart rate than nonobese normotensive patients (85.9 vs 79.6 beats/min, P <.001). Among patients who underwent ABPM, isolated systolic hypertension was found in 51% (36/71) by clinic BP and in 62% (18/29) with confirmed hypertension by ABPM. Blood pressure variability during daytime and sleep periods was higher in obese than nonobese patients for systolic BP (P <.01) and diastolic BP (P <.05).

CONCLUSIONS

The findings of increased heart rate and BP variability in obese children with isolated systolic hypertension suggest that sympathetic nervous system hyperactivity may contribute to its pathogenesis.

Cardiovascular recovery from stress predicts longitudinal changes in blood pressure

Cardiovascular reactivity and recovery were examined as predictors of blood pressure changes over 3 years. Blood pressure and heart rate readings were obtained from 73 men and women aged 18-20 years during cold pressor, mental arithmetic, tourniquet ischemia, cycle exercise and step exercise tasks. Regression analyses indicated that after adjustment for initial blood pressure, initial age, initial body-mass index, sex, parental history of hypertension, and length of follow-up, heightened heart rate reactivity to mental arithmetic was associated with increased follow-up systolic blood pressure (DeltaR(2)=0.04, P<0.05). Systolic blood pressure recovery from cold pressor and tourniquet ischemia were also positively related to follow-up systolic blood pressure (DeltaR(2)=0.04 and 0.04, respectively, P<0.05) and remained so even after adjustment for the corresponding cardiovascular reactivity measures. These findings suggest that cardiovascular reactivity and recovery measures are modest predictors of longitudinal changes in blood pressure.

Hypertension in black people: study of specific genotypes and phenotypes will provide a greater understanding of interindividual and interethnic variability in blood pressure regulation than studies based on race

Hypertension is more frequent and more severe in some Black populations. Although many studies have focused on hypertension in black people in an attempt to understand the genetic and environmental factors that regulate blood pressure, this approach has not been productive. Study of the relationship between specific phenotypes and genotypes, both within and across ethnic groups, is more likely to advance our understanding of the regulation of blood pressure than studies focused on race and blood pressure.

Ethnic differences in pain tolerance: clinical implications in a chronic pain population

OBJECTIVE

Although numerous studies have independently examined ethnic differences in clinical and experimental pain, few have investigated differences in both sensitivity to controlled noxious stimuli and clinical pain reports in the same sample. The present experiment examined the effects of ethnicity (African American vs. white) on experimental pain tolerance and adjustment to chronic pain.

METHODS

Three hundred thirty-seven (68 African American and 269 white) patients with chronic pain referred to a multidisciplinary treatment center participated in the study. In addition to completing a number of standardized questionnaires assessing adjustment to chronic pain, participants underwent a submaximal effort tourniquet procedure. This experimental pain procedure yields a measure of tolerance for a controlled noxious stimulus (ie, arm ischemia).

RESULTS

African American subjects reported higher levels of clinical pain as well as greater pain-related disability than white participants. In addition, substantial group differences were observed for ischemic pain tolerance, with African Americans demonstrating less tolerance than whites. Correlational analyses revealed a small but significant inverse relationship between ischemic pain tolerance and the reported severity of chronic pain.

CONCLUSIONS

Collectively these findings support previous research revealing ethnic differences in responses to both clinical and experimental pain. Moreover, the present results suggest that enhanced sensitivity to noxious stimuli on the part of African Americans may be associated with ethnic differences in reported clinical pain, although the magnitude of ethnic differences was much greater for ischemic pain tolerance than for clinical pain measures.

Prevention of essential hypertension in minority populations

The precursors of essential hypertension (EH) begin in childhood. If the etiology of the evolution of EH were discovered, interventions may be developed to lead to the primary prevention of EH. In particular, one ethnic group, African-Americans (Blacks), are at increased risk of development of EH in adulthood. Hemodynamic changes in response to stressors are termed measures of cardiovascular reactivity (CVR). Ethnic difference in CVR are known to exist; are these markers or mechanisms of EH evolution? Investigations are underway to discover the mechanism(s) of the excessive vasoconstriction which appears to be characteristic of the CVR responses in Blacks. These may lead to the pharmacologic, or non-pharmacologic, interventions which may be initiated in childhood and prevent EH in adults.

Racial differences in hemodynamic responses to environmental thermal stress among adolescents

BACKGROUND

Previous studies by our laboratory and others have shown that blood pressure (BP) responses to many short-term laboratory stressors are greater in black than in white children. We sought to determine the cardiac and vascular contributions to these differences in BP reactivity and whether racial differences in vascular reactivity involve excessive vasoconstriction or deficient vasodilation.

METHODS AND RESULTS

We evaluated BP, heart rate, and impedance cardiographic measures of preejection period (PEP) and total peripheral resistance (TPR) in healthy black (n=76) and white (n=60) adolescents (mean age, 14.8 years) during passive exposure to a vasoconstrictive cold chamber (8 degrees C to 10 degrees C) and a vasodilatory heat chamber (40 degrees C to 42 degrees C). Results indicated greater decreases in PEP and increases in TPR in blacks than whites during cold exposure (P<0.05) but no group differences during heat exposure. Covariance analyses indicated that the racial differences during cold exposure probably reflected greater beta-adrenergic cardiac reactivity and alpha-adrenergic vasoconstrictive reactivity in blacks than whites.

CONCLUSIONS

Blacks and whites exhibited comparable myocardial and vasodilatory responses to heat stress, but blacks exhibited heightened myocardial and vasoconstrictive reactivity to cold stress. These results suggest that the locus of racial differences in vascular reactivity involves vasoconstrictive rather than vasodilatory function. The pattern of racial differences during cold stress raises the possibility that both myocardial and vasoconstrictive mechanisms may contribute to the increased risk of hypertension in blacks.

Role of cardiovascular reactivity to mental stress in predicting future hypertension

Hypertension (HT) has been known since times immemorial to be one of the major causes of morbidity and mortality. It contributes to atherosclerotic cardiovascular disease, increasing its risk 2-3 times and is also associated with dyslipidemia, insulin resistance, glucose intolerance and obesity (1). The age of onset of hypertension is now earlier than before, making it essential that early detection of people who could be future hypertensives is done. Therefore, cardiovascular reactivity to stress in predicting future hypertension becomes important. In this fast paced age most people are exposed to mental stress which is the most common and prevalent form of stress. Increase in blood pressure (BP) in response to emotional arousal is well known, but support for this hypothesis of reactivity in predicting future hypertension is limited. We are attempting here to put forth a review of the various endeavours done so far to support this hypothesis.

Perceptions of interethnic group racism predict increased vascular reactivity to a laboratory challenge in college women

African-Americans have disproportionately higher rates of hypertension than any other U.S. ethnic group. Researchers have postulated that the psychosocial-stress association with racism may help explain these higher rates in African-Americans, as well as blood pressure variability among African-Americans. Using a quasi-experimental design, this study examined the relationship between perceived interethnic group racism (racism) and blood pressure responses in 39 African-American females. Measurements of blood pressure were obtained before, during, and after a laboratory challenge where participants spoke about their personal views and feelings concerning animal rights. Perceptions of racism, as well as psychological and coping responses to racism, were assessed via the Perceived Racism Scale. The results revealed that on average, participants perceived racism 75.25 times/year. Racist statements were perceived most often, and speaking up was the most frequently reported coping response. The overwhelming majority of participants (76.47%) used active and passive coping responses to deal with racism. Among the psychological responses to racism, the magnitude of emotional responding was greatest for anger. Multivariate regression analyses indicated that perceived racism was significantly and positively related to diastolic blood pressure changes during the speech (p = .01), early recovery (p < .003), and late recovery (p = .01) periods. Potential confounders did not mitigate these effects. The findings highlight the importance of delineating the role of more real-world behavioral challenges in future research exploring blood pressure variability and hypertension risk in African-Americans.

High stress responsivity predicts later blood pressure only in combination with positive family history and high life stress

High cardiovascular responsivity to stressors has not consistently improved prediction of later blood pressure increases beyond the predictive effects of baseline pressure. Animal models suggest that genetic susceptibility to hypertension and frequent stress exposure are important modulating factors in stress-related hypertension. Thus in 103 men originally tested at age 18 to 22 years and reassessed 10 years later, interactive effects of genetic susceptibility (defined as 1 or more hypertensive parents) with high stress responsivity (defined as top 25% on the basis of blood pressure and cardiac responses during both reaction time and cold pressor tasks) were examined in relation to follow-up systolic and diastolic levels and to change in blood pressure status from normal (diastolic<80 mm Hg) to marginally elevated (diastolic 85 to 95 mm Hg). Men with the combination of high stress response and hypertensive parents demonstrated higher systolic (P<0.05) and diastolic levels (P<0.05) at follow-up, and they showed a 7-fold increase (7.5, 95% confidence intervals 2.3, 24.3; P<0.001) in relative risk of change in blood pressure status versus men with no family history and a 3-fold increase (3.8, confidence intervals 1.5, 9.6; P<0.004) versus less stress-responsive men who also had hypertensive parents. In 65 men who also provided ratings of daily stress, family historyxstress responsivityxdaily stress interactions were significant in predicting follow-up systolic and diastolic levels (P<0.006 and 0.03, respectively), with highest pressure levels seen when high life stress was reported by high stress responders and/or men with hypertensive parents. In conclusion, results suggest that stress responsivity as a long-term predictor is modulated by both genetic and environmental factors.

Longitudinal association of cardiovascular reactivity and blood pressure in Samoan adolescents

OBJECTIVE

The longitudinal association between blood pressure (BP) reactivity to a video game and resting BP 3 to 4 years later was investigated in 83 Samoan adolescents from American and (Western) Samoa as part of a multidisciplinary study of cardiovascular disease (CVD) risk in modern Samoans.

METHODS

Participants ranged in age from 11 to 14 years at baseline, in 1992 to 1993, and 14 to 18 years at follow-up in 1996. Video game BP reactivity was defined as the residual score of the regression of the maximum BP during the video game on the minimum resting BP before the video game. The predictive effect of baseline video game BP reactivity on follow-up resting BP was tested using regression models with baseline resting BP, baseline body mass index (BMI), and age as covariates.

RESULTS

Systolic BP reactivity to the video game at baseline was significantly, p=.04, and independently associated with resting systolic BP 3 to 4 years later. Samoan adolescents who had higher systolic BP reactivity scores at baseline had significantly higher resting systolic BP at follow-up after adjustment for the significant effects of baseline resting systolic BP, age, and BMI. There were no interactions between sex and reactivity or between residence, American Samoa or (Western) Samoa, and reactivity in the models, indicating that the effects of systolic BP reactivity in early adolescence on later adolescent resting systolic BP were similar in the entire study sample.

CONCLUSIONS

Video game cardiovascular reactivity seems to assess aspects of psychophysiological arousal and prospective CVD risk in Samoan adolescents of both sexes residing in both Samoas, and may be useful for understanding the role of psychosocial stress and health in modernizing societies.

Effects of race, sex, and socioeconomic status upon cardiovascular stress responsivity and recovery in youth

Cardiovascular (CV) responsivity to and recovery from acute laboratory stressors, as derived from aggregate scores of CV functioning during and after postural change, video game challenge, social competence interview, and parent-child conflict discussion, were evaluated in 272 youths [mean age 13.5 +/- 2.6 years; 162 Blacks (77 males, 85 females), 110 Whites (60 males, 50 females)], all with a positive family history of essential hypertension. Blacks demonstrated greater systolic and diastolic blood pressure (SBP, DBP) and lower heart rate responsivity compared to Whites (all P values < 0.05). A race by neighborhood socioeconomic status (SES) interaction for SBP responsivity was also observed where low SES Whites and high SES Blacks had the greatest responsivity compared to their same race cohorts. Additionally, upper SES Whites had the lowest total peripheral resistance responsivity. For recovery, Blacks and males exhibited higher SBP during recovery compared to Whites and females, respectively. These findings extend previous studies and provide further support for the hypothesis that recovery from stress is a potentially informative component of the contribution of stress responsivity to cardiovascular disease.

Inverse relationship of urinary cyclic GMP to blood pressure reactivity in the CARDIA study: vasodilatory regulation of sympathetic vasoconstriction. Coronary Artery Risk Development in Young Adults

OBJECTIVE

To determine whether urinary cyclic GMP (cGMP), which mediates the actions of the vasodilators nitric oxide and atrial natriuretic factor, is inversely related to blood pressure (BP) reactivity. In previous work, we found that urinary cGMP was inversely related to diastolic BP, but cGMP levels were higher among individuals presumed to have increased adrenergic activity, increased reactivity, and increased risk of hypertension (blacks, individuals with a family history of hypertension).

METHOD

We measured 24-hour urinary cGMP levels in a substudy of 529 individuals in the Coronary Artery Risk Development in Young Adults (CARDIA) study; the sample was 23 to 35 years of age and approximately balanced for race (black/white) and gender. BP reactivity to stressors (video game, star-tracing, cold pressor) was tested 3 years earlier. Baseline BP was included as a covariate in all analyses.

RESULTS

Diastolic BP reactivity to cold pressor was inversely related to cGMP excretion (p < .05); the relationship was strongest among black women with a family history of hypertension (partial r = -.33, p < .01). Systolic BP reactivity to star-tracing was also inversely related to cGMP (p < .01); the relationship for both star-tracing and video game stressors was strongest among black men (partial r values = -.25 and -.24, respectively; p values < .01).

CONCLUSIONS

The results indicate that vasodilatory activity may impact the BP response to stress through modulation of adrenergic activation, particularly among blacks.

Predictors of future ambulatory blood pressure in youth

OBJECTIVE

The objective of this study was to determine the predictors of future ambulatory blood pressure in normotensive youths with family histories of essential hypertension.

STUDY DESIGN

Eighty-eight healthy youths (mean age 10.9 +/- 2.5 years; 52 blacks, 36 whites; 45 boys) were studied. During an initial visit anthropometric variables and hemodynamics were measured at rest and before, during, and after three laboratory stressors: postural change, forehead cold, and video game challenge. The subjects' ambulatory blood pressure was monitored for 24 hours as part of a follow-up evaluation an average of 2.5 years later.

RESULTS

Anthropometric and demographic variables and measures of reactivity to laboratory stressors were related to future daytime and nighttime ambulatory blood pressure.

CONCLUSION

These findings provide important information on the predictors of ambulatory blood pressure and underscore the importance of resting blood pressure and adiposity. These results support the guidelines of the Second Task Force, which recommend the measurement of blood pressure and adiposity in the context of ongoing health care.

Effects of parental history of hypertension and urbanization on blood pressure in zimbabweans

The increasing prevalence of essential hypertension is a growing public health concern for Zimbabwe and other African countries. Two important risk factors for hypertension are urbanization and parental history of hypertension. The relations among parental history of hypertension, urbanization, and blood pressures (BPs) are poorly understood. The objective of this study is to clarify these relations in a population of urbanized, African, young adults. The relation between parental history of hypertension and urbanization on resting BP's and Bp responses to a mental arithmetic stressor was examined in a group of normotensive, Black medical students with (n = 36) and without (n = 34) a parental history of high BP, and with (n = 49) and without (n = 19) a parental history of urbanization. Results indicate that those with a positive parental history counterparts. Further, those with parents residing in urban areas had higher resting SBPs than those with parents residing in rural areas. However, no reactivity differences were apparent between the urban and rural parent groups. These data suggest that although parental history for hypertension influences both resting and reactivity BP's parental history of urbanization may influence only resting BP.

Cardiovascular reactivity to video game predicts subsequent blood pressure increases in young men: The CARDIA study

OBJECTIVE

This study was undertaken to determine the relationship between heightened reactivity of blood pressure (BP) during stress and 5-year changes in blood pressure and hypertensive status, using the CARDIA study.

METHOD

A total of 3364 participants (910 white men, 909 white women, 678 black men, and 867 black women), initially 20 to 32 years old and normotensive, were included. Cardiovascular reactivity to psychological stressors (video game and star-tracing tasks for 3 minutes, cold pressor test for 1 minute) was measured in 1987-1988. We then examined reactivity as a predictor of significant BP change (> or = 8 mm Hg, thought to represent a clinically significant increase) over the next 5 years. Logistic regression models were used to control for potential covariates. Significant BP change and the development of hypertension (BP greater than 140/90 or taking medication for hypertension) over the 5-year follow-up were examined in separate analyses.

RESULTS

Increased systolic blood pressure (SBP) reactivity to the video game was associated with a significant 5-year SBP increase among the entire cohort, independent of resting SBP (p < .0001). Subsequent analyses showed that this relationship held for men but not for women. Reactivity to the star-tracing task or the cold pressor test did not predict significant BP change. Among black men only, new hypertensives (N = 36) had greater diastolic blood pressure (DBP) reactivity to the video game (p = .01).

CONCLUSIONS

Although BP reactivity to all physical and mental stressors used in this study did not consistently predict 5-year change in BP in this young cohort, the results indicate that reactivity to a video game stressor predicts 5-year change in BP and early hypertension among young adult men. These findings are consistent with other studies showing the usefulness of stressors producing a primarily beta-adrenergic response in predicting BP change and hypertension. The results may be limited by the shortened initial rest and recovery periods used in the CARDIA protocol.

Cardiovascular reactivity to stress and left ventricular mass in youth

We studied the relationships of cardiovascular reactivity during mental stress with left ventricular mass index in a group of prepubertal children 8 to 10 years old and in a group of peripubertal or postpubertal adolescents 15 to 17 years old. One hundred fifteen participants, varying in age group, sex, and race (black and white), took part in a laboratory stress protocol consisting of a reaction-time task, a mirror tracing task, a cold forehead challenge, and a stress interview. Cardiovascular measures included blood pressure and heart rate, as well as cardiac output, stroke volume, total peripheral resistance, and preejection period obtained noninvasively with impedance cardiography. Measures of left ventricular mass were made by echocardiography. Results indicated that across all participants, left ventricular mass index was associated with cardiovascular responses during the mirror tracing and cold forehead tasks, especially with those responses reflecting increased vasoconstriction. Subgroup analyses showed that these associations were significant for males and sometimes adolescents but not for females and children. As mirror tracing and cold forehead tasks most consistently produce alpha-adrenergic activation, the results suggest a model in which vasoconstriction due to mental stress is related to increased left ventricular mass in susceptible individuals, even at a young age.

Potassium intake and cardiovascular reactivity in children with risk factors for essential hypertension

OBJECTIVES

Our study objectives were as follows: (1) to determine whether urinary excretion of potassium is lower in black than in white children, (2) to determine whether cardiovascular reactivity (CVR) varies inversely with dietary intake of potassium, and (3) to confirm that CVR is greater in black than in white children, and in children with a family history of hypertension than in those without such a history.

STUDY DESIGN

Baseline measurements included 24-hour urinary sodium, potassium, and creatinine levels and food intake (by questionnaire). Resting and stress blood pressure were measured during blood sampling, cold water foot immersion, and a video game before and after 1 week each of supplementation with potassium citrate, 1.5 mmol/kg per day, and placebo administered in random order.

RESULTS

Thirty-nine children aged 7 to 15 years were studied. White subjects had higher baseline excretion of potassium than black subjects (p < 0.001) and higher vegetable intake (p < 0.01), which were positively correlated (r = 0.53, p < 0.001). At baseline, the 24-hour urinary potassium/creatinine ratio varied inversely with diastolic CVR to the video game stressor in white children (r = -0.55, p = 0.02). Cardiovascular reactivity was not attenuated measurably by potassium supplementation compared with placebo. The CVR was greater in children with a family history of hypertension than in those without, but was not greater in black children than in white children.

CONCLUSIONS

The urinary potassium/creatinine ratio is higher in white than black children because their intake of vegetables is greater; dietary potassium intake may modulate CVR, particularly in white children with a family history of hypertension, but may need to be supplemented for more than 1 week to demonstrate attenuation of CVR; and a family history of hypertension may be a stronger predictor of enhanced CVR than is race.

Reduced dietary potassium reversibly enhances vasopressor response to stress in African Americans

Acute vasopressor responses to stress are adrenergically mediated and hence potentially subject to differential modulation by dietary potassium and sodium. The greater vasopressor responsiveness in blacks compared with whites might then be consequent not only to a high dietary salt intake but also to a marginally reduced dietary potassium intake. Under controlled metabolic conditions, we compared acute vasopressor responses to cold and mental stress in black and white normotensive men during three successive dietary periods: (1) while dietary potassium was reduced (30 mmol K+/70 kg per day) and salt was restricted (10 to 14 days); (2) while salt was loaded (15 to 250 mmol Na+/70 kg per day) (7 days); and (3) while salt loading was continued and potassium was either supplemented (70 mmol K+/70 kg per day) (7 to 21 days) in 9 blacks and 6 whites or continued reduced (30 mmol K+/70 kg per day) (28 days) in 4 blacks (time controls). At the lower potassium intake, cold-induced increase in forearm vascular resistance in blacks was twice that in whites during both salt restriction and salt loading. Normalization of dietary potassium attenuated cold-induced increases in both forearm vascular resistance and systolic and diastolic blood pressures in blacks but only in systolic pressure in whites. In blacks but not in whites, normalization of dietary potassium attenuated mental stress-induced increases in systolic and diastolic pressures. In normotensive blacks but not whites, a marginally reduced dietary intake of potassium reversibly enhances adrenergically mediated vasopressor responsiveness to stress. That responsiveness so enhanced over time might contribute to the pathogenesis of hypertension in blacks.

Pathophysiology and treatment implications of hypertension in the African-American population

Regardless of the etiology, hypertension remains a major public health problem in African-Americans and is associated with significant morbidity and mortality. Additional data on the pathophysiology of this disease in this population are needed, as are data on the best therapies to decrease the high complication rate. Because many of the large studies on hypertension have included few African-Americans, recruitment of this ethnic group into clinical trials should be promoted. Further studies into the genetic factors in the pathophysiology of racial differences in hypertension may shed more light on this complex issue.