Family History of Hypertension and Cardiovascular Responses to Orthostatic Stress

Cardiovascular effects of orthostatic stress (sitting to standing) were assessed in 60 healthy young male subjects according lo family history of hypertension (half with a positive and half with a negative family history' of hypertension). Systolic (SBP) and diastolic blood pressure (DBF) were recorded on each successive heart heal using a non-invasive blood pressure tracking system. Heart rate (HR) and respiration rate (RR) were also recorded. During the postural change, characteristic phasic changes were shown with an initial fall and subsequent recover of SBP and DBF and a mirror image response in MR and RR. Phasic analysis of the pre-standing sit, peak/trough, and recovery stand values indicated group differences in the initial as well as the later phases of orthostatic response. In the initial phase, subjects with a positive family history of hypertension showed an earlier trough in systolic and pulse pressure and an earlier peak in heart rate response immediately on standing up. The level of the pulse pressure trough was also higher in these subjects. In the later standing phase, these subjects showed higher levels of pulse pressure. The results were interpreted in terms of increased sympathetic nervous system activity during the initial phase and structural and neurocirculatory abnormalities in the later phase of orthostatic regulation in individuals with a positive family history of hypertension.     

Influences of Potential for Hostility, Type A Behavior, and Parental History of Hypertension on Adolescents'' Cardiovascular Responses During Stress

We investigated the influences of Type A behavior, potential for hostility, and parental history of diagnosed hypertension on adolescents’ cardiovascular responses to three behavioral stressors. The participants were 72 male and 99 female adolescents enrolled in grades 6 to 12. Results showed that adolescents with a hypertensive parent had larger diastolic blood pressure responses during all three stressors than did adolescents without hypertensive parents; this effect was particularly pronounced among the Type As. Adolescents rated as high on potential for hostility had elevated systolic and diastolic blood pressure responses, particularly during isometric exercise. Results regarding parental history of hypertension and Type A replicate previous studies in adolescents. Results regarding potential for hostility showed for the first time that early signs of hostility are related to psychophysiological responses thought to be pathophysiological mechanisms in the etiology of cardiovascular diseases.     

Parental Hypertension and Cardiovascular Response to Stress in Healthy Young Adults

One indicator of elevated risk for subsequent development of essential hypertension is the presence of the disorder in either or both parents. Exaggerated cardiovascular responsivity to stress has also been suggested as a possible precursor to hypertension. This study examined the relationship between parental hypertension and the heart rate (HR), systolic (SBP), and diastolic blood pressure (DBP) levels of 103 healthy college-age men, during two resting conditions and stressful cold pressor and reaction time tasks. Sons of hypertensive parents (N = 25) showed higher HR and SBP than sons of normotensive parents (N = 78) during both rest and stress, but these differences were greatest during the stressful reaction time (RT) task. No reliable differences in DBP were seen. A subsample of 45 subjects, including 14 with hypertensive parents, were also monitored during a second stress, the cold pressor test; only trends toward HR or BP differences related to parental hypertension were seen for this stress, although HR and SBP differences during the RT task were still significant (p<.05) even in this smaller group. Since the incidence of high blood pressure is known to be greater among the offspring of hypertensive parents, these findings suggest that cardiovascular responses to certain types of stress (e.g., active coping tasks) may help predict future risk of hypertension.     

Cardiovascular Reactivity in Borderline Hypertensives during Behavioural and Orthostatic Stress

Blood pressure and heart rate were measured in 16 borderline hypertensive and 10 normotensive subjects during mental arithmetic and reaction time tests, on standing, and during the pre-test period and instructions preceding these tests. The reliability of responses was assessed on 3 consecutive days. Increases in systolic blood pressure and heart rate during mental arithmetic instructions, increases in systolic blood pressure during the mental arithmetic test, and increases in diastolic blood pressure on standing were greater in borderline hypertensives. These differences persisted throughout the 3 experimental sessions. Apart from stress ratings for the reaction time test, other behavioural measures, including number of mental arithmetic mistakes and reaction times, did not differ between normotensives and borderline hypertensives. The possibility that the parasympathetic nervous system exerts a restraining influence on sympathetic overactivity in borderline hypertension was discussed.     

Aerobic Fitness and Opioidergic Inhibition of Cardiovascular Stress Reactivity

The role of endogenous opioids in aerobic fitness-induced decrements in cardiovascular stress reactivity was examined by comparing the effects of opioid antagonism with naltrexone on responses to stress in young adults with high versus low levels of aerobic fitness. Two hundred forty subjects were given an activity questionnaire and males with the highest (Fit) and lowest (Nonfit) aerobic activity profiles were recruited for maximal oxygen consumption (VO2max) treadmill testing and psychological stress testing (final sample N = 28). Heart rate and blood pressures were measured during performance on a computer-controlled arithmetic task after pretreatment with either naltrexone (Trexan, DuPont) or a placebo. During placebo challenges, Fit subjects, compared with Nonfit, showed lower heart rate reactivity during stress and lower mean arterial blood pressures immediately before and during recovery from stress. Naltrexone eliminated these reactivity differences by increasing heart rate reactivity and raising mean arterial blood pressure in Fit subjects. These data suggest that aerobic fitness is associated with enhanced opioidergic inhibition of circulatory stress reactivity. Opioidergic modulatory effects on stress reactivity may comprise an important mechanism in fitness-associated risk reduction for cardiovascular disease.     

Cardiovascular Reactivity to Psychological Stress in Healthy Children

Cardiovascular reactivity to stress has been implicated as a marker and/or mechanism in the development of cardiovascular disease. No normative data exist to classify children's reactivity to psychological stress. This investigation presents normative percentile data on the hemodynamic responses (heart rate and blood pressure) of 310 healthy, black or white, children between the ages of 6 and 18 years to the stress of a television video game. A series of three video games, played under three increasing levels of stress, elicited progressively higher values of blood pressure and heart rate. Both the child's race and gender, as well as the experimenter's race, significantly affected reactivity. Children demonstrated a wide range of interchild reactivity, thus allowing separation of individuals into high and low risk percentile groups.     

Cardiovascular Responses to Stress: I. Measures of Myocardial Response and Relationship to High Resting Systolic Pressure and Parental Hypertension

A comparison of pre-ejection period (PEP), heart rate (HR), and systolic (SBP) and diastolk (DBP) blood pressure responses to the cold pressor test and a pseudo-shock avoidance reaction time task was performed in 183 young men. These tasks differ in the extent to which they evoke enhanced myocardial and vascular adrenergic activity. Decreases in PEP were more pronounced during the reaction time task, while DBP increased more during the cold pressor test. MR and SBP responses did not differentiate the two tasks. PEP decreases occurred in the absence of any apparent increase in cardiac preload or decrease in afterload. Parental hypertension as determined by physician reports was associated with higher SBP across all conditions. A subgroup of individuals (15%) showed SBP levels >140 mm Hg when typical clinical stethoscopic determinations were made, but less than half as many showed such elevations during a more extended resting baseline using remotely operated devices. High stethoscopic SBP was associated with greater cardiovascular responses to the stressors, while high SBP during the extended baseline was not.     

Parental Hypertension and Cardiovascular Response to Cognitive and Isometric Challenge

The purposes of this investigation were to contrast the cardiovascular responses of sons of hypertensive and normotensive parents to tasks involving cognitive and isometric challenge, and lo examine the relationship of individual differences in heart rate (HR) reactivity to baseline blood pressure (BP) measurements. Thirty-six male, undergraduate volunteers (18 with and 18 without a parental history of hypertension) were scheduled for two, 1-hr experimental sessions (Days I and II). On Day 1, HR and BP measurements were obtained while subjects performed each of three laboratory tasks: a difficult test in concept formation, serial subtraction, and a sustained handgrip at 30% of maximum voluntary contraction. Each task lasted 3 min and was preceded by a 3-min baseline interval. On Day II, subjects were instructed to relax quietly while baseline measures of HR and BP were recorded. Relative to sons of normotensive parents, offspring of hypertensives exhibited higher mean Systolic BPs during all task periods; no corresponding group differences were observed on either Day I or Day II baseline recordings. Unlike SBP, Diastolic BP measurements did not vary reliably by parental hypertensive/normotensive status. Although the mean HRs of sons of hypertensives were significantly higher than in offspring of normotensives, these differences obtained uniformly across both the baseline and task intervals. Among subjects identified as High HR reactors during the two cognitive tasks, sons of hypertensive parents exhibited Day II baseline SBPs about 9 mmHg higher than did subjects without a parental history of hypertension. Among subjects identified as Low HR reactors, baseline SBPs did not differ reliably between sons of hypertensive and normotensive parents.     

The Effects of Caffeine and Stress on Blood Pressure in Individuals with and without a Family History of Hypertension

The effects of two doses of caffeine (125 mg, 250 mg) were compared to a placebo dose (3 mg) in a randomized double-blind cross-over design in 36 male caffeine users, half with and half without a family history of hypertension. Systolic blood pressure, heart rate, and respiration were recorded during rest, a mental arithmetic task, and recovery periods. I inter both resting and mental stress conditions, the two doses of caffeine on the average increased systolic pressure by 6.7 mini In compared to the placebo. The effects for the 125 me and 250 mg doses did not differ significantly. The pressor effects of caffeine and mental stress combined in an additive fashion. Systolic blood pressure levels were significantly greater in individuals with a family history of hypertension across all conditions, but not specifically in response to caffeine. The results arc comparable to those previously reported in caffeine-naive subjects.     

Parental History of Essential Hypertension, Active Coping, and Cardiovascular Reactivity

Differences in cardiovascular reactivity to stress between individuals with and without a family history of essential hypertension (EH) may be affected by stimulus characteristics and/or individual differences in behavioral response. Twenty-four male students with a parental history of EH and 24 without a parental history of EH participated in two laboratory sessions during which two “active’ (mental arithmetic and the Stroop word-color interference test) stressors and one “non-active’ (isometric hand-grip) stressor were presented. Family history subjects exhibited greater systolic blood pressure responses than non-family history subjects only to the two active stressors in Session 2, despite the fact that, overall, isometric hand-grip elicited the largest responses. High-performing Stroop subjects with a parental history of EH displayed greater heart rate responses to the task than high-performing subjects without a parental history of EH in both sessions. No group differences appeared among poor performers. The degree to which a stressor encourages active coping behavior appears to be one determinant of differences in cardiovascular response between individuals with and without a family history of EH.     

Cardiovascular Effects of Caffeine and Stress in Regular Coffee Drinkers

The effects of caffeine on cardiovascular activity at rest and in response to psychological stress were studied in a group of 30 healthy males who were regular coffee drinkers to replicate caffeine-stress interactions found previously in caffeine-naive subjects. Measures of heart rate, blood pressure, and forearm blood flow were recorded at rest and during the performance of a stressful mental task in two separate sessions. Caffeine (250 mg) or placebo was administered double-blind in a within-subject design. Relative to placebo, caffeine had a pressor effect at rest which persisted during stress and recovery such that blood pressure during stress was higher if caffeine had been consumed. Caffeine also magnified the forearm blood flow and forearm vascular resistance responses to stress, suggestive of a synergistic interaction of caffeine and stress. Analysis of individual difference variables suggested that caffeine effects on the forearm vascular variables were greatest in subjects who were Type B and had a positive family history of hypertension. Results suggest that regular caffeine use does not necessarily lead to tolerance for caffeine-stress interactions and that certain characteristics may be associated with greater sensitivity to caffeine's effects.     

Respiratory Sinus Arrhythmia and Cardiovascular Responses to Stress

The parasympathetic nervous system provides mechanisms that could attenuate sympathetically mediated heart rate stress responses and might have even more general antagonistic actions on stress reactivity. Individuals characterized by higher levels of parasympathetic tone might, through such mechanisms, be less reactive when stimuli elicit sympathetically mediated responses. Respiratory sinus arrhythmia (RSA) is considered to be a noninvasive index of cardiac parasympathetic (vagal) tone. The present study investigated whether individual differences in RSA level at rest could predict variations among individuals in the magnitude of cardiovascular responses to psychological stress. None of the measures of resting respiratory sinus arrhythmia, derived from spectral analysis of beat-to-beat changes in resting heart rate, predicted the observed variations in cardiovascular task reactivity. However, scores reflecting respiratory sinus arrhythmia as the percentage of total heart rate variability (RSAnorm) were negatively correlated with blood pressure levels, both at rest and during the task. Furthermore, subjects with higher scores for RSAnorm demonstrated a faster adaptation of heart rate responses during stress, which suggests the development of parasympathetic antagonism to ongoing sympathetic arousal. Although a simple relationship between respiratory sinus arrhythmia and reactivity was not observed, these results encourage further investigation of RSA measures as psychophysiological indices of individual differences in parasympathetic (vagal) cardiac tone, or perhaps of general parasympathetic/sympathetic balance, which could modulate the expression of potentially pathogenic stress responses.     

Cardiovascular Responses to Effortful Active Coping: Implications for the Role of Stress in Hypertension Development

Recent contributions to the literature on stress and hypertension are discussed. The significance of effortful active coping in evoking sympathetically-mediated heart rate and blood pressure increases is supported by results of studies involving both aversive and appetitive task incentives. Young healthy males who are above-average in heart rate during coping tasks show consistently higher heart rates and systolic pressures during other stresses as well, but are indistinguishable from less reactive persons when relaxed. Studies involving beta-blockade indicate that these above-average cardiovascular increases are partly due to a greater beta-adrenergic response among the high heart rate reactors. In addition, the parents of these high heart rate reactors report a greater incidence of hypertension than parents of low reactors, suggesting that high cardiovascular responses during active coping stress may reflect a high degree of susceptibility to later hypertension.     

The Relation Between Rhythmic Cardiovascular Variability and Reactivity to Orthostatic, Cognitive, and Cold Pressor Stress

Two groups of normotensive, male subjects having either a positive or negative parental history of essential hypertension were exposed to passive body tilt from horizontal to a 70° head-up posture, while systolic and diastolic blood pressure, heart period, and respiration amplitude were sampled on a beat-by-beat basis. Subjects also performed mental arithmetic and cold pressor tasks, and cardiovascular reactivity was expressed as change from baseline levels. The body tilt data were analyzed by cross-spectral analysis focusing on two frequency bands, one between .06-.1 Hz, and the other at the predominant breathing frequency. The two groups did not differ significantly in their basal levels of physiological activity or in their response to the tasks. Cross-spectral analysis identified tilt induced changes in the power spectra and coherence spectra within the two frequency bands. These changes differed between the two frequency bands and among the various physiological response systems investigated. Larger rhythmic oscillations in heart period within both frequency bands predicted greater cardiovascular reactivity to the mental arithmetic task but not the cold pressor task. The results are discussed in terms of neural control mechanisms (e.g., vagal tone) implicated in the dynamic regulation of cardiovascular function during psychophysiological states such as stress.     

Sibling Similarities in Cardiovascular Reactivity to Stress

To examine the similarities of nun-twin sibling pairs in cardiovascular reactivity to stress, in terms of both individual parameters such as heart rate and general cardiovascular reactivity, 36 young adult sibling pairs were recruited. Members of 12 same-sex male, 12 same-sex female, and 12 opposite-sex pairs participated in a 66-min experimental protocol consisting of alternating stress and relaxation periods. Pour stressors were employed: a challenging conceptual task, mental arithmetic, isometric bund-grip, and the cold pressor test. Repeated measurements of systolic and diastolic blood pressure (SBP. DBF), heart rate (HR), ear pulse transit time (EPTT), and digital blood volume pulse (DBVP) were obtained. Pair members exhibited significant similarities in resting SBP, DBP, and HR. A number of significant similarities in reactivity to stress were observed. To examine the specificity of familial influences on different aspects of cardiovascular response to stress, a number of canonical and cross-correlations were computed. The cardiovascular reactions of one sibling were used to predict those of his/her brother or sister. Several of the correlations attained significance. Most interestingly, familial influences on SBP, DBP, and DBVP reactivity to the cold pressor test appear to exhibit some degree of overlap, possibly reflecting more fundamental familial influences on alpha-adrenergic reactivity. Joint familial influences on behavioral and cardiovascular reactivity to stress are discussed.     

Cardiovascular and cortisol reactions to acute psychological stress and cognitive ability in the Dutch Famine Birth Cohort Study

Given evidence linking blunted cardiovascular and cortisol reactions to acute stress and a range of adverse behavioral outcomes, the present study examined the associations between cardiovascular and cortisol reactivity and cognitive ability measured independently of the stress task exposure. Cognitive ability was assessed using the Alice Heim-4 test of general intelligence and two memory tasks in 724 men and women who were part of the Dutch Famine Birth Cohort Study. Blood pressure and heart rate, as well as cortisol reactivity, were measured to a battery of three standard acute stress tasks. Poorer cognitive ability was associated with lower cardiovascular reactions to stress and lower cortisol area under the curve. Our results are consistent with recent findings implicating low physiological stress reactivity in a range of adverse behavioral and health outcomes.     

Sympathetic Neuronal Function and Left Ventricular Performance During Behavioral Stress in Humans: The Relationship between Plasma Catecholamines and Systolic Time Intervals

We studied the relationship between sympathetic neuronal function and left ventricular performance during stress in humans by analysis of endogenous catecholamine levels and systolic time intervals. The results showed that performance on a stressful cognitive task was accompanied by changes in plasma catecholamines, heart rate (HR), blood pressure (BP), and systolic time intervals. The cardiovascular responses were significantly correlated with plasma levels of epinephrine (E) and norepinephrine (NE). The relationship between plasma catecholamines and systolic time intervals is thought to reflect sympatho-adrenomedullary impact on left ventricular performance during stress.     

Children''s Cardiovascular Reactivity: Stability of Racial Differences and Relation to Subsequent Blood Pressure over a One-Year Period

After measuring blood pressure and heart rate at rest and during a video game procedure in 477 children enrolled in 3rd grade, 434 (91%) children had these measurements repeated a year later in 4th grade. Black children demonstrated greater blood pressure and heart rate reactivity than White children in both years, and an increase in heart rate reactivity from 3rd to 4th grade. Gender effects were inconsistent. Systolic and diastolic blood pressures during the video game were more highly correlated from year-to-year than were the resting measures. Regression analysis indicated that systolic reactivity was significantly related to subsequent systolic pressure at rest, particularly among Black girls. Diastolic reactivity was associated with subsequent resting diastolic pressure only among White children. Associations between reactivity and future blood pressure were independent of initial resting blood pressure. This study suggests that cardiovascular reactivity to psychological stress may be one important factor in future level of blood pressure and that the increased heart rate reactivity of Black children may be associated with the prevalence of hypertension among Black adults.     

Cardiovascular and Electrodermal Response Patterns in Heart Rate Reactive Individuals During Psychological Stress

The goal of this research was to examine the cardiovascular and electrodermal response patterns of heart rate reactive and nonreactive individuals to psychological stress. Sixty males were tested while resting, listening to tones, identifying tone patterns, and performing mental arithmetic. Dependent variables were blood pressure, heart rate (HR), and skin conductance responses. Based on the change in HR from baseline to the first minute of mental arithmetic, two extreme reactivity groups of 15 subjects each were formed. Results indicated that HR reactive subjects had higher systolic blood pressure and HR than nonreactives. Reactives showed greater HR lability during all the tasks and a phasic acceleration to tones, while nonreactives showed a deceleration. Finally, comparisons of skin conductance responses indicated that subjects who were nonreactive when measuring HR were more reactive when measuring skin conductance. The HR reactivity seen in these subjects has been linked to predisposition to psychosomatic illness, and the current findings are discussed in that light.     

Efficiency of Coping with a Real-Life Stressor: A Multimodal Comparison of Aerobic Fitness

The mediating effects of aerobic fitness on the psychological and physiological responses to a real-life psychological stressor (rappelling) were examined. Subjective anxiety, heart rate, nor epinephrine, epinephrine, and cortisol were monitored in IS male novice rappellers at various intervals before and following the rappel task. Results showed that high fit compared to low fit subjects maintained overall lower heart rate levels. Aerobic power was associated with faster recovery from subjective anxiety and a more efficient recovery for relative plasma epinephrine measures. Norepinephrine, heart rate, and cortisol did not parallel this recovery pattern. These results provide some support for the research which indicates that high levels of aerobic power are associated with greater coping efficiency.