Children's cardiovascular reactivity: stability of racial differences and relation to subsequent blood pressure over a one-year period

α-Adrenergic receptor blockade attenuates pressor response during mental stress in young black adults

Black individuals exhibit increased blood pressure (BP) responses to sympathetic stimulation that are associated with an increased risk of hypertension (HTN). We tested the hypothesis that α1 -adrenergic blockade inhibits the increased BP response during and after 45-min stress in young normotensive Black adults, which may be mediated, in part, by dampened vasoconstriction and decreased renal sodium retention. Utilizing a double-masked randomized, crossover study design, 51 normotensive Black adults (31 ± 8 yr) were treated with either a placebo or 1 mg/day of prazosin for 1 week. On the final day of each treatment, hemodynamic measures and urinary sodium excretion (UNaV) were collected before (Rest), during (Stress) and after (Recovery) 45 min of mental stress induced via a competitive video game task. During the Stress period, diastolic BP and total peripheral resistance (TPR) were significantly lower with prazosin compared to placebo (p < .05 for both). Similarly, we observed lower systolic BP, diastolic BP, and TPR during the Recovery period with prazosin versus placebo (p < .05 for both). There was no effect of prazosin on stress-associated UNaV. The change in systolic BP from Rest to Recovery was positively associated with the change in TPR with both treatments (p < .05 for both). In summary, prazosin treatment dampened BP reactivity to 45-min mental stress and lowered post-stress BP over the recovery period, which was linked to reduce TPR in young normotensive Black adults. These results suggest that α1 -adrenergic receptor activity may contribute to BP responses and delayed BP recovery to prolonged mental stress through increased vasoconstriction in Black adults.

Angiotensin II receptor blocker attenuates stress pressor response in young adult African Americans

African Americans (AAs) are susceptible to hypertension (HTN) and its associated organ damage leading to adverse cardiovascular (CV) outcomes. Psychological stress is proposed to contribute to the development of HTN; however, the potential role of the renin-angiotensin system (RAS) in stress-related HTN in AAs is largely unknown. In this study, we tested the hypothesis that activation of RAS is a potential contributing factor for altered CV responses to stress, and suppression of angiotensin II (Ang II) activity will improve hemodynamic responses to a prolonged mental stressor in healthy young AAs. Utilizing a double-blind, randomized, crossover study design, 132 normotensive AAs (25 ± 7 years) were treated with either a placebo (PLC) or 150 mg/d irbesartan (an Ang II type 1 receptor blocker; ARB) for 1 week. On the final day of each treatment, hemodynamic measures and urinary sodium excretion (UNaV) were collected before, during and after a 45 minute-mental stress. The magnitude of stress-induced increase in blood pressure with ARB was blunted and delayed compared to PLC. Systolic blood pressure at the end of recovery on ARB was significantly lower compared to either PLC (110 ± 13 vs 117 ± 12 mm Hg respectively; P < 0.001) or the prestress level on ARB (P = 0.02). ARB treatment reduced overall vasoconstriction and improved poststress UNaV. ARB attenuated blood pressure responses to mental stress and improved the poststress BP recovery process which were partly linked to reduced overall vasoconstriction and improved stress-induced UNaV in young adult AAs prior to the development of disease conditions. These results suggest that treatment approaches that inhibit RAS action could have significant relevance to potentially lower susceptibility to stress responses and eventually the premature development of HTN in AAs.

Two-year stability of individual differences in (para)sympathetic and HPA-axis responses to public speaking in childhood and adolescence

Long-term stability of individual differences in stress responses has repeatedly been demonstrated in adults, but few studies have investigated the development of stability in adolescence. The present study was the first to investigate the stability of individual differences in heart rate, parasympathetic (RMSSD, pNN50, HF), sympathetic (LF/HF, SC), and HPA-axis (salivary cortisol) responses in a youth sample (8-19 years). Responses to public speaking were measured twice over 2 years. Stability was moderate for absolute responses and task delta responses of HR, RMSSD, pNN50, and HF. Stability was lower for SC and task delta responses of LF/HF and cortisol. Anticipation delta responses showed low stability for HR and cortisol. The latter was moderated by age or puberty, so that individual differences were more stable in more mature individuals. The results support the suggestion that stress responses may be reset during adolescence, but only for the HPA axis.

Reliability of cardiovascular reactivity to stress: Internal consistency

Research on the reliability of cardiovascular reactivity has focused on temporal stability and intertask consistency with only modest results. The present study evaluated the internal consistency reliability of cardiovascular reactivity in three large samples of adolescents and young adults (N=326, 136, and 142). Impedance cardiographic and blood pressure measures were recorded at rest and during standard laboratory stress tasks (math, video game, cold pressor). The reliability of cardiovascular reactivity within tasks, as assessed by Cronbach's alpha coefficient of internal consistency, ranged from alpha=.83 to .96 for 4-min to 5-min math tasks, and alpha=.65 to .94 for 3-min video game and cold pressor tasks. Although highly reliable within tasks, cardiovascular reactivity was less reliable across tasks, even within a single testing session. Possible reasons for the discrepancy between internal consistency and intertask consistency are discussed.

Interactive effects of perceived racism and coping responses predict a school-based assessment of blood pressure in black youth

BACKGROUND

Research indicates that perceived racism and coping responses are associated with basal blood pressure (BP) levels and BP reactivity in Black adults. No study could be found, however, that has explored the independent and interactive effects of perceived racism and coping responses in a cohort who probably has the greatest risk of developing primary hypertension--Black youth.

PURPOSE

This study examined the relationship of perceived racism and coping responses to a continuous measure of BP and to a categorical measure of BP status (normal vs. high-normal or high).

METHODS

The convenience sample consisted of 217 Black youth (M age = 11.4 years, SD = 1.3). Participants reported on perceived racism and coping responses (Accepting It, Self-Blame, Taking Action, and Talking to Someone). BP was assessed with an automated monitor in school.

RESULTS

Approximately 32% of the sample had average BP levels that were high-normal or high. Hierarchical linear and logistic regression analyses were used to assess the predictive utility of perceived racism and the four coping responses to the continuous and categorical BP assessments. Although perceived racism and the coping response variables did not emerge as significant independent predictors in the linear or logistic regression analyses, perceived racism interacted with Accepting It (p = .009) in the linear regression analysis predicting systolic BP. Follow-up linear regression analyses indicated that perceived racism was not significantly associated with systolic BP among participants low in Accepting It but was inversely related to systolic BP among participants high in Accepting It. Perceived racism also interacted with Accepting It (p = .016) and Talking to Someone (p = .0009) in the logistic regression analysis predicting BP status. Follow-up logistic regression analyses revealed that (a) perceived racism was not significantly associated with BP status among participants low in Accepting It but was inversely related to BP status among participants high in Accepting It, and (b) perceived racism was inversely associated with BP status among participants low in Talking to Someone but was not significantly related to BP status among participants high in Talking to Someone.

CONCLUSIONS

The contribution of environmental and psychosocial factors to hypertension risk should be considered when exploring correlates of continuous and categorical assessments of BP in Black youth.

Violence exposure and optimism predict task-induced changes in blood pressure and pulse rate in a normotensive sample of inner-city black youth

OBJECTIVE

This investigation examined the association of violence exposure (home and neighborhood) and optimism to task-induced changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse rate (PR).

METHODS

Drawn from a larger investigation, the convenience sample for this study consisted of 172 normotensive black youth (mean age = 11.5 years, standard deviation = 1.3). Violence exposure and optimism were self-reported by participants, and task-induced changes in SBP, DBP, and PR were measured with an automated monitor during two sequentially administered digit-forward and digit-backward tasks.

RESULTS

Hierarchical regression analyses revealed that violence exposure was inversely related to task-induced changes in SBP (p = .010) and DBP (p = .005). Optimism was not an independent predictor of blood pressure or PR changes (p-s > .32). The final step of these hierarchical analyses indicated that the effects of violence exposure and optimism interacted to predict task-induced changes in SBP (p = .013) and PR (p = .003). Follow-up regression analyses indicated that violence exposure was inversely related to task-induced changes in SBP among participants high in optimism and was positively associated with PR reactivity in participants low in optimism.

CONCLUSIONS

The youth in this study have intact mechanisms for buffering blood pressure responses to violence exposure, especially those who are more optimistic about their future-a person factor whose moderating effects might wane with advancing age.

Ethnic differences in cardiovascular responses to laboratory stress: a comparison between asian and white americans

Compared to other ethnic groups, Asian Americans show significantly lower rates of cardiovascular disease (CVD). We tested the hypothesis that Asian Americans would show reduced cardiovascular responses to laboratory stressors than Caucasians. Forty-three Asians (18 men, 25 women) and 77 Caucasians (36 men, 41 women) with a mean age of 24 years (SD = 3.93) participated in a stress reactivity protocol consisting of four tasks (speech, serial subtraction, mirror tracing, handgrip) while heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were measured. Asian Americans demonstrated overall lower reactivity across tasks for SBP F(1,117 = 7.48, p < .01) and a trend toward lower HR response F(1,117 = 3.18, p < .10). A significant ethnicity by task interaction was observed for HR reactivity F(3,351 = 2.94, p < .05) such that Caucasians showed greater responses for the subtraction task.

Respiratory Sinus Arrhythmia During Stress Predicts Resting Respiratory Sinus Arrhythmia 3 Years Later in a Pediatric Sample

The author examined whether respiratory sinus arrhythmia (RSA) responses to stress predicted resting RSA approximately 3 years later in children and adolescents. A total of 149 children and adolescents (49% girls and women, 44% African Americans) participated in 2 laboratory protocols approximately 3 years apart. RSA reactivity during tasks was consistent within participants across tasks during each session. Resting RSA at Visit 1 explained 17% of the variance in resting RSA at Visit 2 when body mass index, duration between visits, race, gender, and age were controlled for. Visit 1 RSA reactivity explained an additional 5% of the variance in resting RSA at Visit 2. The positive relationship between Visit 1 reactivity and Visit 2 resting levels suggests that larger decreases in RSA during stress predicted lower resting RSA. Conversely, increases in RSA during stress were associated with higher resting RSA an average of 3 years later.

Salivary cortisol and heart rate in stunted and nonstunted Nepalese school children

OBJECTIVE

To test the hypothesis that stunted Nepalese children have an altered stress response system when compared with matched nonstunted children in response to a battery of psychological tests.

DESIGN

Case-control study.

SETTING

Poor urban areas of Kathmandu, Nepal.

SUBJECTS

A total of 64 stunted (less than -2 s.d. height-for-age) children compared with 64 nonstunted (> -1s.d. height-for-age) schoolchildren between 8 and 10 y old matched for school and sex.

METHODS

A psychological test session was administered, which included mental arithmetic and two tests of working memory. Salivary cortisol samples were obtained at five points during testing, and heart rate was measured during testing and also at baseline. Salivary cortisol samples were also obtained once early in the morning. Hemoglobin was assessed at the testing session, and extensive data were obtained on the social background of the children's families.

RESULTS

Stunted Nepalese children showed a blunted physiologic response (salivary cortisol and heart rate) to psychological stressors (P<0.05) when compared with nonstunted children, but were not different from the nonstunted children in baseline measures, when controlling for social background. The two groups were not different in terms of social background.

CONCLUSIONS

These findings suggest that childhood growth retardation may be associated with changes in physiological arousal, and that stunting could be associated with hyporesponsivity in response to psychological stress.

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.

Growth retardation is associated with changes in the stress response system and behavior in school-aged jamaican children

In the developing world, 39% of children <5 y old are short for their age (stunted, defined as height-for-age less than -2 SD of National Center for Health Statistics references), and many have poor levels of mental development along with behavioral problems. We showed previously that 8- to 10-y-old children from a longitudinal cohort who experienced early childhood stunting had altered hypothalamic-pituitary-adrenocortical (HPA) and sympathetic-adrenomedullary (SAM) system activity. We repeated the study with 31 newly recruited, stunted Jamaican school children (less than -2.0 SD height-for-age) and nonstunted controls (n = 31, more than -1.0 SD height-for-age) matched for sex, age and school. All children were tested in a 1.5-h session, including psychological and physiologic stressors, in which their behaviors, salivary cortisol concentrations and heart rates were measured. In addition, we measured urinary catecholamine (epinephrine, norepinephrine, dopamine) concentrations, which were not reported for the children in the longitudinal cohort. After controlling for covariates that differed between groups (child intelligence quotient, body mass index and birth weight), stunted children had faster resting heart rates while lying and sitting (P < 0.05) and also during psychological testing (P < 0.05), as well as higher concentrations of urinary epinephrine (P < 0.05) and norepinephrine (P < 0.05), compared with nonstunted children. In addition, the stunted children were less happy (P < 0.01), more inhibited (P < 0.01) and more frustrated (P < 0.05) during the psychological tests than nonstunted children. These results suggest that growth retardation is associated with alterations in stress-sensitive systems, particularly the SAM system, and that this connection may contribute to the poor levels of development observed in stunted children.

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.

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.

Cardiovascular responsivity to stress in adolescents with and without persistently elevated blood pressure

OBJECTIVES

The goal of this study was to compare the cardiovascular responses to behavioural stressors of three groups of adolescents who differed in blood pressure status across assessments.

DESIGN

Casual blood pressure of adolescents who were identified as having elevated blood pressure during a school screen was re-evaluated in the laboratory. The adolescents were classified into two groups: (i) those with consistently elevated blood pressure across school and laboratory assessments and (i) those with labile blood pressure whose blood pressure in the laboratory was below 130/80 mmHg. A comparison group of adolescents with consistently normal blood pressure was also included.

METHODS

Cardiovascular parameters were assessed during rest and during two behavioural stressors, the evaluated speaking task and the mirror tracing task.

RESULTS

Adolescents with elevated blood pressure were more vascularly responsive across stressors than adolescents with labile blood pressure, who, in turn, were more reactive than adolescents with normal blood pressure.

CONCLUSIONS

These results suggest that vascular reactivity to behavioural stressors may be useful in predicting risk of hypertension because of its sensitivity in distinguishing adolescents with consistently elevated blood pressure from those with labile blood pressure and those with normal blood pressure.

Preliminary study examining relationship between family environment and resting mean arterial pressure in African-American youth

This investigation examined the relationship between family environment and mean arterial pressure in a sample of African-American youth. Completed data were collected from 46 adolescents attending an inner-city junior high school. Blood pressure measurements were assessed in a seated position with a Dinamap 1846 Vital Signs Monitor. To assess the additive effects associated with the family environment, a composite risk score (cohesion, conflict, control, and organization subscales of the Family Environment Scale) was computed. Regression analyses indicated that the cumulative risk associated with the family environment was predictive of resting mean arterial pressure.

Family conflict predicts blood pressure changes in African-American adolescents: a preliminary examination

Reviews of the youth literature suggest that the precursors of elevated blood pressure begin in childhood. As such, it may be possible to identify processes among African-American adolescents that are associated with blood pressure changes. This study examined the relationship between family conflict and mean arterial pressure changes in a sample of 39 African-American adolescents. Resting mean arterial pressure, systolic blood pressure, and diastolic blood pressure were assessed at Time 1 and Time 2, separated by a period of 6 months. Assessments of perceived family conflict and negative life events were taken at Time 1. Findings from the multiple regression analyses indicated that family conflict predicted mean arterial blood pressure changes, independent of the effects of age, gender, and body mass index. Although preliminary, these findings highlight the importance of exploring environmental processes that may influence physiological outcomes in adolescents.

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.

The effects of blood pressure resting level and lability on cardiovascular reactions to laboratory stress

Evidence that individuals with elevated resting blood pressures display excessive cardiovascular reactions to laboratory stress is regarded as implicating excessive reactivity in the pathogenesis of hypertension. However, it remains possible that this relationship is artifactual, in that resting blood pressure levels and cardiovascular reactions might both reflect intrinsic cardiovascular lability. To examine this possibility, blood pressure and heart rate were measured at rest and in response to an active laboratory stressor in 1259 men. Systolic blood pressure and heart rate reactions to the stressor were predicted by resting blood pressure. Although cardiovascular lability showed some association with both reactivity and resting blood pressure level, the resting blood pressure level-reactivity relationship survived statistical adjustment for such associations. Accordingly, the excessive cardiovascular reactions characteristic of individuals with elevated resting blood pressure would not appear to be explainable, to any substantial extent, by lability effects.

Does background stress heighten or dampen children's cardiovascular responses to acute stress?

OBJECTIVE

Does background stress heighten or dampen children's cardiovascular responses to acute stress?

METHOD

To address this question, the cardiovascular responses to four acute laboratory stressors of 150 children and adolescents were evaluated according to their self-reported background stress level. Background stress was determined during a standardized interview and was a priori classified according to its importance, frequency, and whether it was ongoing or resolved.

RESULTS

Results showed that children and adolescents who reported important stressors or stressors that were ongoing and frequent exhibited a larger increase in diastolic blood pressure and total peripheral resistance during all four laboratory stressors than their low stress counterparts. Additional analysis showed that the results could not be accounted for by sociodemographic variables or by the personality traits measured in this study.

CONCLUSIONS

Results suggest the importance of measuring background stress in understanding an individual's acute stress response.

Influence of ethnicity and gender on cardiovascular responses to active coping and inhibitory-passive coping challenges

OBJECTIVE

The goal of this study was to evaluate how black and white men and women responded physiologically to specific laboratory challenges.

METHODS

Hemodynamic responses to an active coping (evaluated speaking) and two inhibitory-passive coping (mirror tracing, cold pressor) tasks were examined in 138 black and white men and women.

RESULTS

Significant ethnicity by gender interactions occurred for the evaluated speaking task. Black men responded with lower blood pressure, cardiac output or heart rate, or both, than black women, white men, and white women, who did not differ from each other. Black men, relative to the other subgroups, also reported more inhibitory-passive coping, hostility, and pessimism, and less social support. Whites also responded with greater increases in systolic blood pressure during mirror tracing than blacks.

CONCLUSIONS

These findings indicate that black-white differences in physiological responsivity obtained for men may have limited generalizability for women. The results also suggest that environmental and social factors rather than genetic or constitutional factors may play a role in black-white reactivity differences.

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.

Anxiety, antisocial behavior, and heart rate regulation in adolescent males

We explored relationships between anxiety and antisocial behavior and autonomic heart rate regulation in a homogenous sample (N = 175) of 15-year-old males. Measures of anxiety and antisocial behavior were obtained at yearly intervals over a period of 4-6 years. Components of heart rate variability associated with postural (sympathetic) and respiratory (vagal) change and transfer of respiratory to heart rate variability were estimated at age 15 using spectral analytic techniques. Anxiety and antisocial behavior were predictably related to enhanced and diminished levels of mean heart rate, respectively. Anxiety was also predictably related to enhanced sympathetic mediation of phasic postural effects on heart rate. Antisocial behavior was unexpectedly related to disruption of vagally mediated, phasic respiratory effects on heart rate. Anxiety and antisocial behavior showed distinct relationships to heart rate, and to the autonomically mediated components of heart rate variability from postural and respiratory sources. Spectral analytic techniques helped elucidate these unique regulatory patterns, suggesting utility for future research in this area.

Relationships between children's cardiovascular stress responses and resting cardiovascular functioning 1 year later

Resting cardiovascular parameters were predicted from anthropometric data, resting baseline cardiovascular data, and cardiovascular responses to three laboratory stressors completed 1 year earlier. Subjects were 106 male and female children (72 Whites, 34 Blacks) aged 6-7 years at the initial evaluation. During initial testing, blood pressure, heart rate, cardiac output, and total peripheral resistance were assessed at rest and also during a forehead cold pressor task, postural change, and treadmill exercise. The same cardiovascular parameters were then assessed at rest 1 year later. After controlling for significant anthropometric measures and the pertinent previous year's resting data, systolic and diastolic responses to the cold pressor were predictive of respective follow-up resting levels. Postural change heart rate responses were predictive of follow-up resting heart rate after controlling for initial resting levels. Exercise cardiac index reactivity predicted follow-up cardiac index after controlling for earlier resting levels and adiposity. Follow-up total peripheral resistance index was predicted by earlier resting levels.

The ability of active versus passive coping tasks to predict future blood pressure levels in normotensive men and women

Casual blood pressure (BP) after a 2-year follow-up interval was determined in 40 normotensive men and women (20 Blacks and 20 Whites), who had been initially tested for cardiovascular responses to a variety of active and passive coping tasks, including active speech, passive speech, reaction time, and forehead cold pressor tasks. Stepwise multiple regression analyses were used to identify the best model for predicting follow-up BP. Average systolic blood pressure (SBP) level during cold pressor stress was the single most powerful predictor of casual SBP over 2 years even after controlling for initial resting SBP. Other predictors of follow-up SBP were initial SBP, parental history of hypertension, and heart rate and SBP during passive speech (final model R(2) = .78). For follow-up diastolic blood pressure (DBP), the only significant predictors were initial DBP and male gender. These results contribute to a growing body of literature that suggests that cardiovascular measures observed during stressors have predictive validity above and beyond that of traditional predictor variables.

Cardiac profile and disruptive behavior in boys at risk for delinquency

The objective of this study was to examine associations in youth between antisocial behavior and cardiovascular profile. Younger brothers of adjudicated delinquents (N = 120) received a standardized psychiatric assessment and an assessment of three factors often studied in behavioral cardiology research: family history of hypertension, resting blood pressure, and obesity. As a group, relative to population norms, these youth exhibited signs of obesity and elevated blood pressure, with 30% of the sample appearing clinically obese and 24% having a blood pressure above the 90th percentile for national norms in their age cohort. Within the sample, score on the Child Behavior Checklist (CBCL) Delinquency scale correlated with blood pressure (r = .29-.34) and an index of obesity, weight/height3 (r = .20). Further, scores on the CBCL Delinquency, Aggression, and Externalizing scales were elevated in boys with a positive family history of hypertension. Among boys at risk for delinquency, disruptive psychopathology relates to factors often studied in behavioral cardiology research. Relationships between risk factors for ischemic cardiovascular disease and hostile behavior may be manifested with measures of disruptive psychopathology.

Reproducibility of blood pressure and heart rate reactivity: a meta-analysis

Reproducibilities of blood pressure and heart rate (HR) reactivity reported in studies assessing responses to the same laboratory stressors across occasions were reviewed with meta-analytic techniques. Changes in HR had the greatest reproducibility (r = .555), followed by systolic blood pressure (SBP) (.407) and diastolic blood pressure (DBP) (.348). Both SBP and HR response reproducibility was higher at shorter test-retest intervals, whereas DBP values varied unsystematically with length of test-retest interval. Older samples exhibited higher SBP and DBP reproducibility to stressors. SBP and DBP reproducibilities were better for tasks that did not make speech demands. The reliability of reactivity assessment was higher when based on three or more measurements. On the basis of available evidence, the drop in stress reproducibility, as test-retest interval increases, places limits on the viability of BP reactivity as a strong marker or risk factor for coronary heart disease.

Pressor reactions to psychological stress and prediction of future blood pressure: data from the Whitehall II Study

OBJECTIVE

To examine whether reactions of blood pressure to psychological stress predict future blood pressure.

DESIGN

Blood pressure was recorded at a medical screening examination after which pressor reactions to a psychological stress task were determined. Follow up measurement of blood pressure was undertaken, on average, 4.9 years later.

SETTING

20 civil service departments in London.

SUBJECTS

1003 male civil servants aged between 35 and 55 years at entry to the study.

MAIN OUTCOME MEASURE

Blood pressure at follow up screening.

RESULTS

Reactions of systolic blood pressure to stress correlated positively with systolic blood pressure at follow up screening (r = 0.22, P < 0.01). The dominant correlate of follow up blood pressure was blood pressure at initial screening (r = 0.60; P < 0.01 between initial and follow up systolic blood pressure; r = 0.59, P < 0.01 between initial and follow up diastolic blood pressure). Stepwise multiple regression analysis indicated that reactions to the stressor provided minimal prediction of follow up blood pressure over and above that afforded by blood pressure at initial screening. In the case of follow up systolic blood pressure, systolic reactions to stress accounted for only 1% of follow up variance; systolic blood pressure at initial screening accounted for 34%. With regard to diastolic blood pressure at follow up, the independent contribution from diastolic reactions to stress was less than 1%.

CONCLUSION

Pressor reactions to psychological stress provide minimal independent prediction of blood pressure at follow up. Measurement of reactivity is not a useful clinical index of the course of future blood pressure.

1-Year stability and prediction of cardiovascular functioning at rest and during laboratory stressors in youth with family histories of essential hypertension

Blood pressure (BP). heart rate, cardiac index, and total peripheral resistance index were measured at rest and in response to postural change, forehead cold stimulation, and a video game challenge in a sample of 128 White and 155 African-American normotensive youth with family histories of essential hypertension (EH). These measurements were readministered 1 year later (12.5 +/- 3.2 months). Moderate temporal stability was observed for all resting and absolute stress responses. Reliability estimates for reactivity change scores were lower, although some were within acceptable ranges. African-American youth exhibited greater BP and peripheral resistance index reactivity to forehead cold on both evaluations. After controlling for various anthropometric and demographic parameters and the pertinent previous year's resting cardiovascular (CV) parameter, mean video game systolic blood pressure (SBP) responses were predictive of resting SBP whereas absolute forehead cold and video game diastolic responses predicted resting diastolic blood pressure (DBP) 1 year later. Mean video game DBP responses were also predictive of resting peripheral resistance index after controlling for significant demographic and anthropometric measures. CV reactivity is discussed with regard to possible value in prediction of changes in resting BP and cardiac structure prior lo establishment of EH.

Chronobiologic evaluation of blood pressure in school children

Blood pressure (BP) and heart rate (HR) data were collected over 24 h with an ambulatory BP monitor to (a) determine the existence of 12-, 24-, and combined 12- and 24-h BP patterns in children as previously noted for adults; (b) provide MESOR (an acronym for midline estimating statistics of rhythm), amplitude, and acrophase data for subgroups of students by race and gender; and (c) determine the influence of HR (as an estimate of activity) on BP and BP patterns for 100 normal, healthy students 9-12 years of age. We found no statistically significant differences between various racial groups or between gender for MESOR, amplitude, acrophase, or degree of sinusoidality of circadian rhythmicity (R2 values) for BP; clinically interesting differences were observed, including lower MESOR BPs in Hispanic males when compared with their female counterparts and slightly higher MESOR BPs in blacks of both genders when compared with whites. In addition, we demonstrated subgroups of students who exhibited specific 24-h and combined 12- and 24-h patterns. Also, 67% of subjects showed stable or nonrhythmic BP patterns, perhaps related to BP sampling intervals. Differences in HR, as a surrogate measure of activity, accounted for 56% of the variation in systolic BP but only 26% in diastolic BP over the 24 h.

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

During the 5 years of this investigation, resting blood pressure and pressor reactivity were measured in 292 white children and 46 black children in 1987, 1988, 1989, and 1991. In 1987, all children were in the third grade; in 1991, the children were in the seventh grade. Reactivity was assessed with a standardized psychological stressor, a television video game. Children displayed significant stability of absolute blood pressure and heart rate reactivity between grades 3 and 7. At all examinations, black children demonstrated blood pressure reactivity that was significantly greater in magnitude (both absolute level and change from resting measurements) than that of white children. Black children exhibited significantly greater heart rate reactivity only when defined as change from the resting measurements; absolute levels of heart rate reactivity were comparable for blacks and whites. For black children, blood pressure reactivity in 1987 was the strongest predictor of resting blood pressure (both systolic and diastolic) in 1991. Among white children, resting blood pressure was the strongest predictor of future resting blood pressure. Further research is needed to determine if ethnic differences in children's pressor reactivity are associated with ethnic differences in the prevalence of hypertension.