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.

Presence of human friends and pet dogs as moderators of autonomic responses to stress in women.

Autonomic responses were measured while 45 adult women performed a standard experimental stress task in the laboratory with only the experimenter present and 2 weeks later at home in the presence of a female friend, pet dog, or neither. Results demonstrated that autonomic reactivity was moderated by the presence of a companion, the nature of whom was critical to the size and direction of the effect. Ss in the friend condition exhibited higher physiological reactivity and poorer performance than subjects in the control and pet conditions. Ss in the pet condition showed less physiological reactivity during stressful tasks than Ss in the other conditions. The results are interpreted in terms of the degree to which friends and pets are perceived as evaluative during stressful task performance. Physiological reactivity was consistent across the laboratory and field settings.

Affect intensity and cardiac arousal.

Relationships between affect intensity and basal, evoked, and perceived cardiac arousal were investigated in 3 experiments. Affect intensity was assessed using Larsen and Diener's (1987) Affect Intensity Measure (AIM). Cardiac arousal was evoked with exercise in the 1st study and with mental arithmetic in the 2nd and 3rd. Perceived cardiac arousal was measured under optimal conditions using a standard heartbeat discrimination procedure. Women as a group scored higher on the AIM. Affect intensity was unrelated to basal or evoked cardiac arousal and was negatively related to perceived cardiac arousal in all 3 studies. Data suggest that affect intensity, although unrelated to actual physiological arousal, is negatively related to the accuracy with which individuals perceive their own arousal. Results are discussed within the context of an expanded arousal-regulation model (Blascovich, 1990).

Attitude accessibility as a moderator of autonomic reactivity during decision making.

Attitude functionality was assessed in 2 experiments examining attitude accessibility as a moderator of physiological responses during decision making. In Study 1, experimental Ss but not controls rehearsed attitudes toward novel objects (abstract paintings). Subsequently, all Ss made rapid preference judgments for pairs of the paintings. In Study 2, attitudes were rehearsed by all Ss toward 1 of 2 mutually exclusive sets of abstract paintings. During the subsequent decision-making task, half the Ss made rapid pairwise preference judgments for rehearsed abstract paintings and half for pairs from the unrehearsed set. Autonomic measures were recorded continuously throughout both experiments. As predicted, in both experiments less autonomic reactivity was evident during the criterion pairwise preference task for groups for whom attitude rehearsal was relevant to the criterion task.

Cardiorespiratory response under combined psychological and exercise stress.

The effects of combined physical and psychological stress on cardiovascular and respiratory responses were examined. Thirty-six undergraduate men performed a mental arithmetic task and moderate aerobic exercise, separately and in combination, while physiological measures were recorded continuously using electrocardiography, impedance cardiography, and respiratory gas analysis techniques. Cardiovascular responses during the combination of exercise and mental arithmetic stress were greater than those during either stressor alone, indicating that exercise did not mask the increases in cardiovascular performance evoked by psychological stress. In contrast, respiratory responses to the combined stressor were greater than those during isolated mental arithmetic, but less than those during isolated exercise. Thus the results indicate that physical and psychological stress exert a synergistic impact on cardiac performance, but not necessarily on respiratory performance. The results are consistent with the notion that the cardiovascular response to acute psychological stress exceeds concurrent metabolic demands.

The effects of epinephrine administration on impedance cardiographic measures of cardiovascular function.

The effects of epinephrine administration on cardiovascular function were examined in 26 men who were given a bolus injection of either 1:10,000 epinephrine hydrochloride or physiological saline. Impedance cardiographic and continuous blood pressure measures were recorded during a 2-min pre-injection baseline and in the post-injection period. Compared to a saline control, epinephrine elicited greater shortening of heart period, pre-ejection period, and the R-B interval; greater increases in cardiac output, stroke volume, dZ/dt amplitude, Heather Index, and systolic and diastolic pressures; and greater decreases in total peripheral resistance (all P < 0.05). Left ventricular ejection time and the Q-R interval were not affected. The results indicate that inotropic indices that are readily measured by impedance cardiography should be considered as important non-invasive indices of adrenergically mediated responses to stress.

Childhood physical abuse, personality, and adult relationship violence: a model of vulnerability to victimization.

An association between childhood physical abuse and current relationship violence was observed in a sample of 56 young adult women, suggesting that childhood physical abuse may be a unique risk factor for victimization in intimate adult relationships. Aspects of personality and interpersonal functioning that reflect extreme doubt about one's interpretation and understanding of interpersonal events, and an inability to make sensible causal connections between people's thoughts, feelings, and actions largely mediated this link. Implications for intervention and directions for future research are discussed.

Electrodermal lability and myocardial reactivity to stress.

The relationship between electrodermal lability and myocardial reactivity to stress was examined in male undergraduates, who were classified as electrodermally labile (n = 19) or stabile (n = 19) based on the frequency of nonspecific skin conductance responses at rest. Heart rate, pre-ejection period, cardiac output, and skin conductance responses were recorded at rest, during task instructions, and during two mental arithmetic tasks that varied in level of difficulty. As predicted, labiles exhibited greater myocardial reactivity to the task instructions and the tasks than did stabiles, with more persistent group differences emerging for pre-ejection period and cardiac output than for heart rate. The group differences did not vary as a function of task difficulty, but did decline over time. These results support a positive relationship between electrodermal lability and beta-adrenergic myocardial reactivity to stress, particularly under conditions of task novelty or uncertainty, and suggest that electrodermal lability is related fundamentally to arousal and reactivity processes.

Object relations of sexually and physically abused female children: a TAT analysis.

Selected Thematic Apperception Test (Murray, 1943) stories of 17 sexually abused, 15 physically abused, and 15 nonabused but distressed clinical comparison subjects were analyzed using the Social Cognition and Object Relations Scales (Westen, Lohr, Silk, Kerber, & Goodrich, 1985). Results revealed significant differences in overall object relations between the abused and nonabused children both on mean scores, reflecting lower levels of typical functioning, and on frequency of Level 1 scores, indicating a propensity for more grossly pathological functioning. Further comparisons between sexual and physical abuse victims revealed differential impairments in the capacity to invest in relationships and moral standards. Diagnostic and theoretical implications are discussed.

An evaluation of the ensemble averaged impedance cardiogram.

The ensemble averaged impedance cardiogram was evaluated during rest and during vocal mental arithmetic stress in samples of female (n = 17) and male (n = 40) undergraduates. Measures of myocardial performance determined from ensemble averaged signals were compared to those determined by simple beat-to-beat averaging over 60-s and 20-s sampling intervals. In addition, the influence of cardiac interval variability on dZ/dt amplitude measures was assessed. As expected, measures derived by the two averaging techniques corresponded closely, with correlations ranging from r = 0.882 to r = 1.000 for the 60-s sampling intervals, and from r = 0.726 to r = 1.000 for the 20-s sampling intervals. Inverse relationships of comparable magnitude were found between cardiac interval variability and dZ/dt amplitude measures determined by both averaging techniques, suggesting that these relationships did not result simply from artifacts introduced by the ensemble averaging technique. The results support the validity of ensemble averaging as a method for deriving impedance cardiographic measures of myocardial performance.

Object relations and physical abuse: a TAT analysis.

Selected Thematic Apperception Test (Murray, 1943) stories of 39 physically abused children and a clinical group of 39 children with no recorded history of abuse were examined using the Social Cognition and Object Relations Scales (Westen, Lohr, Silk, Kerber, & Goodrich, 1985). As predicted, a history of physical abuse was associated with a more malevolent object world; a lower level capacity for emotional investment in relations and moral standards; and less accurate, complex, and logical attributions of causality in understanding human interaction. These impairments in object relations were manifest both as a typical level of functioning and as a propensity for more grossly pathological functioning. Results are discussed in terms of clinical and theoretical implications.

Rorschach assessment of malevolence in sexually abused girls.

Clinical samples of sexually abused and nonabused girls were compared on COP/AG, a proposed Rorschach index of malevolence. Defined as the co-occurrence of COP and AG in a single response, this variable is introduced as a Rorschach analog of a measure of malevolence devised for use with narrative material. Sexually abused girls scored significantly higher on COP/AG than did nonabused girls (p < .01), with no group differences emerging for either COP or AG alone. These findings provide empirical support for the salience of malevolence in the interpersonal perceptions and expectancies of victims of childhood sexual abuse. Clinical implications and directions for future research are discussed.

Consistency of hemodynamic responses to cold stress in adolescents.

Laboratory research on hypertension often is performed with cold stress to elicit vasoconstriction and increases in blood pressure. Several studies have shown that cardiovascular responses to the cold pressor test predict the development of hypertension. We extended this research by comparing cardiovascular responses to a traditional forehead cold pressor test and a naturalistic whole-body cold exposure. We evaluated blood pressure and impedance cardiographic measures of cardiac output and total peripheral resistance in healthy black (n=69) and white (n=47) adolescents (mean age, 14.7 years) during forehead cold pressor (3 degrees C to 4 degrees C) and passive whole-body exposure to a cold chamber (8 degrees C to 10 degrees C). Both tasks elicited increases in vascular resistance and blood pressure, but forehead cold elicited an increase in cardiac output, whereas whole-body cold elicited a decrease in cardiac output (P<0.05). Consistent with previous research, there was a tendency toward greater vasoconstrictive reactivity to cold stress in blacks than in whites, particularly during whole-body cold exposure (P<0.05). Cardiovascular reactivity correlated significantly between tasks, but substantial intertask consistency occurred only for cardiac and vascular reactivity in male subjects (r>0.30) but not in female subjects (r<0.15). These gender differences might reflect diminished adrenergic receptor function in female subjects. We conclude that whole-body cold exposure offers a viable, relatively naturalistic alternative to traditional cold pressor tests for the assessment of cardiovascular reactivity.

Object relations of sexually abused female subjects: a TAT analysis.

TAT stories of 17 sexually abused female subjects and a clinical group of 25 female subjects with no documented history of sexual abuse were analyzed using the Object Relations and Social Cognition Scoring System (Western, Lohr, Silk, Kerber, & Goodrich, 1985). Subjects ranged in age from 5 to 16 years. As predicted, mean scores on a measure of overall object relations were significantly different between groups. Specifically, the mental representations of subjects in the abuse group were characterized by more primitive and simple characterizations of people, more negative and punitive affect in their perceptions of the interpersonal world, an inability to invest in people and relationships in other than need-gratifying ways, and an inability to make sensible attributions of self and others. Abuse subjects also produced more pathological responses overall than did their nonabuse counterparts, indicating a tendency toward more extreme and immature functioning. These group differences were independent of any contribution of age and a measure of verbal productivity. Treatment and diagnostic implications are discussed.

Vagal rebound and recovery from psychological stress.

OBJECTIVE: To characterize cardiovascular recovery and examine the possible relationship of vagal activity and reflexes to risk for heart disease. METHODS: Subjects performed cold pressor and mental arithmetic tasks. Heart rate, heart period variability, and pre-ejection period were obtained for 1 minute before, during, and after each task (Experiment 1). In the second experiment, subjects performed a Stroop color-word task and a mental arithmetic task. Heart rate, heart period variability, blood pressure, and baroreflex sensitivity were obtained during the 5-minute baseline, task, and recovery periods (Experiment 2). RESULTS: In Experiment 1, heart rate during recovery was lower than baseline despite continued pre-ejection period shortening, whereas recovery heart period variability was higher than baseline. In Experiment 2, blood pressure increased throughout the session. However, recovery heart rate after mental arithmetic was lower than baseline heart rate, and heart period variability was higher during both recovery periods than during baseline. Vagal rebound, a sharp increase in variability in the first minute of recovery, was reduced in men in Experiment 1 and in individuals with a family history of cardiovascular disease in Experiment 2 and was associated with degree of change in baroreflex sensitivity between task and rest. CONCLUSIONS: Cardiovascular recovery from stress is associated with increased vagal modulation despite residual sympathetic activation. Vagal rebound may be involved in mechanisms resetting the baroreflex sensitivity at the onset and offset of stress. Diminished vagal rebound during recovery from stress is associated with standard risk factors for cardiovascular disease. The results support an association between attenuated vagal reflexes and risk for cardiovascular disease.

Psychophysiological characteristics of narcissism during active and passive coping.

This study provides the first psychophysiological analysis of narcissism by measuring autonomic responses during active and passive anticipatory coping in 40 undergraduate men who scored high or low on the Narcissistic Personality Inventory (NPI). Compared to the low NPI group, the high NPI group showed greater preejection period (PEP) shortening, cardiac deceleration, and skin conductance response (SCR) habituation during anticipation of an aversive stimulus (p < .02). As expected, SCR and PEP reactivity were greater during active than passive coping. In the case of PEP, this effect emerged only in the low NPI group; the high NPI group showed the greatest PEP reactivity during the first task, regardless of coping demands. These data support hypothesized relationships among narcissism, psychopathy, and psychological predictors of cardiovascular disease, and suggest that a psychobiological dimension may underlie important features of narcissism.

Breast-feeding and maternal cardiovascular function.

Two studies examined the effects of breast-feeding on maternal cardiovascular function. In the first experiment, groups of breast-feeding and bottle-feeding women were compared on preejection period (PEP), heart rate (HR), cardiac output (CO), and total peripheral resistance (TPR) recorded for 1-min periods before and during standard laboratory stressors. Compared with bottle-feeders, breast-feeders had higher CO throughout the session, and greater decreases in CO and increases in TPR during cold pressor. In the second experiment, HR and blood pressure (BP) were compared before and after one breast-feeding and one bottle-feeding session in a within-subjects design. Both feeding methods increased BP but decreased HR, and systolic BP was higher for the breast-feeding than the bottle-feeding condition. Both studies support the notion that breast-feeding alters maternal cardiovascular function, possibly through the actions of oxytocin.

Cardiovascular reactivity and adaptation to recurrent psychological stress: the moderating effects of evaluative observation.

The impact of evaluative observation on cardiovascular reactivity and adaptation to recurrent psychological stress was evaluated in 162 undergraduate men and women. All participants performed three mental arithmetic tasks with or without evaluative observation. Impedance cardiographic, blood pressure, task performance, and stress appraisal measures were recorded for each task. Evaluative observation moderated the effects of task repetition on cardiac reactivity but not vascular reactivity. The introduction of evaluative observation disrupted cardiac adaptation, resulting in a resurgence of beta-adrenergic cardiac reactivity (p < .005), whereas the removal of evaluative observation promoted cardiac adaptation. Evaluative observation also increased stress appraisals and slowed task performance. The results support the dual process theory of habituation, rather than stimulus comparator theory, but only partially support cognitive appraisal theory.

The ensemble-averaged impedance cardiogram: an evaluation of scoring methods and interrater reliability.

The interrater reliability and concurrent validity of two methods of scoring the ensemble-averaged impedance cardiogram were evaluated. Impedance cardiographic and electrocardiographic signals were recorded from 40 undergraduate men and women during a baseline rest period and a vocal mental arithmetic task period. Recordings were scored by four rates using a conventional method, involving ensemble averaging after careful editing of beat-to-beat waveforms, and a streamlined method, involving ensemble averaging without beat-to-beat editing. Intraclass correlations for interrater reliability exceeded .92, whereas intraclass correlations for concurrent validity exceeded .97, indicating excellent agreement between rates and scoring methods for all cardiac measures. The streamlined method was significantly faster than the conventional method. The results indicate that variations in beat-to-beat editing do not constitute a serious source of error in the ensemble-averaged impedance cardiogram and support the interrater reliability and concurrent validity of the two scoring methods.

Cardiovascular reactivity and adaptation to recurrent psychological stress: effects of prior task exposure.

The effects of prior task exposure on cardiovascular reactivity to stress were examined in two experiments by randomly assigning participants to repeated exposure groups that performed mental arithmetic pretest and test tasks versus delayed exposure groups that performed only the test task after prolonged rest. Impedance cardiographic and blood pressure measures were recorded continuously from 60 undergraduate men in Experiment 1 and 112 undergraduate men and women in Experiment 2. Task repetition attenuated cardiovascular reactivity and improved task performance in repeated exposure groups (p < .001), suggesting an integrated process of behavioral adaptation. During the test task, delayed exposure groups showed greater cardiac reactivity (p < .01), but not vascular reactivity, than repeated exposure groups. Thus, cardiac reactivity varied as a specific function of prior task exposure, whereas vascular reactivity varied as a general function of time.