Sex Differences in Lipid, Lipoprotein, Cardiovascular, and Neuroendocrine Responses to Acute Stress

This study had two objectives: (a) to examine whether or not lipids and lipoproteins change in response to acute behavioral stress in young adults; and (b) to test the extent of sex differences in the magnitude of the lipid, lipoprotein, neuroendocrine, and cardiovascular changes during stress. Nineteen women and 22 men participated in a serial subtraction task, a videotaped speech task, and a self-evaluation task. The cholesterol portions of low density and high density lipoproteins, triglycerides, free fatty acids, epinephrine, norepinephrine, heart rate, and blood pressure were examined at rest and during each stressor. Repeated measures analyses of variance indicated that stress-related levels of low density and high density lipoprotein-cholesterol, triglycerides, free fatty acids, norepinephrine, heart rate, and blood pressure were elevated, relative to baseline, and that these responses were partially task or order dependent. Subsequent analyses of sex differences showed that males had larger low density lipoprotein-cholesterol and blood pressure increases during all tasks, relative to those of females, and females had larger heart rate responses to the speech task, relative to those of males. There were no sex differences in plasma catecholamine adjustments. These data demonstrate that the cholesterol fractions of high and low density lipoproteins increase during acute psychological stress, and are the first to systematically examine male/female differences in those stress responses.     

Acute hemoconcentration during psychological stress: Assessment of hemorheologic factors

In this study, we examined the effects of acute psychological stress on hemorheology and hemoconcentration in humans and the associations between stress-induced cardiovascular reactivity and hemorheological changes. Stress-induced changes in hemorheology and hemoconcentration were assessed by measuring plasma viscosity, calculated plasma volume, and total plasma protein. Cardiovascular, hemorheologic, and hematologic variables were assessed in 29 healthy men during a 30-min baseline period and a 5-min speech task. Results indicated that the speech task produced a significant increase in plasma viscosity and total plasma protein and a significant decrease in calculated plasma volume. Significant correlations were observed between changes in blood pressure and heart rate and changes in plasma viscosity, total plasma protein, and calculated plasma volume. These results provide direct evidence that acute psychological stress can produce significant changes in hemorheology and hemoconcentration. The most likely mechanism for the stress-induced hemoconcentration effect is a fluid shift from the vascular to the interstitial spaces through increased blood pressure. This research was supported in part by National Institutes of Health Grants HL40962 and HL07560.     

Increases in lipids and immune cells in response to exercise and mental stress in patients with suspected coronary artery disease: effects of adjustment for shifts in plasma volume

This study examined the role of shifts in plasma volume on lipid and immune reactions to stress. Lipid, immune, rheological, and cardiovascular reactions to exercise and mental stress in 51 patients with suspected coronary artery disease were determined. Blood pressure and heart rate were measured during and blood samples taken at the end of each rest and task. Lipids (total cholesterol, triglycerides, HDL, LDL) and immune cells (lymphocytes, monocytes, granulocytes) increased with exercise, whereas cholesterol, LDL, and lymphocytes increased with mental stress. Plasma volume decreased by 1 and 5% following mental and exercise stress, respectively. The task-induced increases in lipids were no longer statistically significant following adjustment for changes in plasma volume, whereas the increases in immune cell numbers survived such correction. This study provides evidence that, in coronary artery disease patients, exercise and mental stress-induced increases in lipids but not immune cells can be largely accounted for by shifts in plasma volume.     

Premenopausal and Postmenopausal Women Differ in their Cardiovascular and Neuroendocrine Responses to Behavioral Stressors

Middle-aged (45-51 years) women performed four tasks while their heart rate, blood pressure, and plasma catecholamines were measured. The tasks were serial subtraction, mirror image tracing, speech, and postural tilt. The speech task was considered to be particularly relevant to women because of its emphasis on social skills. Fifteen premenopausal women reported menstruating regularly and were tested in the early follicular phase. Sixteen postmenopausal women reported not menstruating for at least 12 months and their hormonal status was verified by serum levels of follicle-stimulating hormone. Results showed that postmenopausal women exhibited greater increases from baseline in heart rate during all tasks, relative to premenopausal women, with a particularly pronounced increase during the speech task. Postmenopausal women exhibited greater increases from baseline in systolic blood pressure and epinephrine, relative to premenopausal women, during the speech task only. Explanations for the stressor-specific effect of menopausal status were discussed. The results suggest that reproductive hormones may interact with stressor characteristics to determine middle-aged women's physiological responses to stress.     

Acute psychological stress reduces plasma triglyceride clearance

Acute stress elevates blood lipids, with the largest increases among men and postmenopausal women. The mechanisms for the effect are unknown, but may be due to altered lipid metabolism. This study investigated if acute stress induces transient reductions in triglyceride clearance in middle-aged men and women, and determined if gender and menopause affect triglyceride metabolism. Of the 35 women, half were premenopausal, and half were naturally postmenopausal; men (n = 35) were age matched. Clearance of an intravenously administered fat emulsion was assessed twice: once during a nonstress session, and again during a stress-testing session. During the stress session, a battery of behavioral stressors (serial subtraction, speech, mirror tracing, and Stroop) were performed for 40 min. The clearance rate of exogenous fat was significantly diminished during the stress, relative to the nonstress session. Women had more efficient clearance, relative to men, but there were no effects of menopausal status. The diminished ability to clear an intravenous fat emulsion during stress suggests one mechanism for stress-induced elevations in lipids.     

Sex differences in cardiovascular reactivity to physical appearance and performance challenges

We examined sex differences in cardiovascular reactivity to a novel body image speech task and to three performance-oriented challenges: serial subtraction, handgrip, and mirror tracing tasks. Forty-nine men and 64 women completed the four tasks while heart rate, systolic blood pressure, diastolic blood pressure, and mean arterial pressure were measured. The speech was perceived as requiring more emotionality and empathy for success, whereas the performance tasks were perceived as requiring greater competitiveness. As predicted, women showed greater heart rate reactivity to the body image speech, but men showed greater blood pressure reactivity to the subtraction, grip, and mirror tracing tasks. Results underscore the importance of contextual factors in influencing sex differences in stress responses; women may be more physiologically vulnerable to challenges in the domain of physical appearance, whereas men may react to competitive, performance-oriented challenges.     

Are Cardiovascular Responses to Behavioral Stressors a Stable Individual Difference Variable in Childhood?

The present paper reports two studies which address the extent to which cardiovascular responses to behavioral stress can be conceptualised as a stable individual difference variable in children. In the first study, eighth grade girls (mean age = 14.2 yrs) who had participated in a study of the familial aggregation of cardiovascular responses to behavioral stress were asked to repeat the assessment protocol when they were in (he ninth grade (mean age = 15.1 yrs). Results showed that mean task-induced increases in diastolic blood pressure and heart rate during serial subtraction, mirror image tracing, and isometric handgrip tasks were reliable across test sessions, particularly due to the reliable increases exhibited during the mirror image tracing task. In the second study, fifth grade boys (mean age = 10.4 yrs) who had participated in a previous experiment (Matthews & Jennings, 1984) of cardiovascular responses during a video game were tested in the ninth grade (mean age - 14.0 yrs) in the protocol used in Study 1. Results showed that mean tusk-induced increases in diastolic blood pressure and heart rate during video games were related to mean task-induced increases during serial subtraction, mirror image tracing, and isometric handgrip tasks over three years Liter. The association for heart rate increases during the video game and isometric handgrip task was particularly impressive. These results suggest that task-induced diastolic blood pressure and heart rate responses of children are stable over substantial periods of time and amiss important developmental transitions, and generalize across tasks requiring qualitatively different behavioral responses. Nonetheless, future research is needed in adults and children to further identify factors which influence the stability and generalizability of cardiovascular responses to behavioral stress.     

Changes in plasma volume associated with mental stress ischemia in patients with coronary artery disease.

Psychological stress has been shown to trigger angina and myocardial ischemia in patients with coronary artery disease. However, the mechanisms by which stress may trigger cardiac events has yet to be fully elucidated. Twenty five patients underwent radionuclide ventriculography during a multiple stress challenge. Plasma volume was assessed during rest and at the end of the stress task. Flow-mediated dilatation was also measured. Controlling for endothelial function and medications, patients with ischemia had greater reductions in plasma volume than non-ischemic patients. Reduced plasma volume may be one mechanism by which mental stress may increase the risk for acute coronary events.     

Lipids in psychological research: the last decade.

We review the recent literature examining lipid changes during stressful experiences, and the psychological and constitutional differences that influence lipid levels at rest and that may modulate lipid response to stress. Mild forms of chronic or episodic stress are apparently not associated with alterations in lipids and lipoproteins, but severe forms of real or perceived stress do appear to alter lipid levels. Acute laboratory stress is frequently associated with short-term alterations in lipids and lipoproteins, but the significance of these changes is unclear. Several individual characteristics, such as heightened neuroendocrine or autonomic reactivity to stressors, Type A component behavior, and other aspects of personality, appear to be associated with an atherogenic lipid profile. Stress may influence lipid concentrations and metabolism through a variety of physiological and behavioral mechanisms, but none have been clearly elucidated. Future research should concentrate on understanding these mechanisms.     

Pediatric impedance cardiography: temporal stability and intertask consistency

The pathogenic processes responsible for cardiovascular disease have their origins in childhood. Although children's measures of heart rate and blood pressure have been found to be reliable, the reliability of impedance cardiography derived measures have not been evaluated. Thirty-three children, ages 8-11 participated in two sessions. Stressors included serial subtraction, isometric handgrip, and mirror-image tracing. Results indicated the impedance measures showed moderately high temporal stability (average scores r(avg) = .74; difference scores r(avg) = .53) and intertask consistency (average scores r(avg)= .78; difference scores r(avg)= .53). Blood pressure demonstrated the lowest reliability; Heather index, preejection period, and stroke volume demonstrated the highest. These findings suggest children's cardiovascular reactivity to laboratory stressors can be reliably and consistently assessed using impedance cardiography.     

Effects of utterance length and vocal loudness on speech breathing in older adults

Age-related reductions in pulmonary elastic recoil and respiratory muscle strength can affect how older adults generate subglottal pressure required for speech production. The present study examined age-related changes in speech breathing by manipulating utterance length and loudness during a connected speech task (monologue). Twenty-three older adults and twenty-eight young adults produced a monologue at comfortable loudness and pitch and with multi-talker babble noise playing in the room to elicit louder speech. Dependent variables included sound pressure level, speech rate, and lung volume initiation, termination, and excursion. Older adults produced shorter utterances than young adults overall. Age-related effects were larger for longer utterances. Older adults demonstrated very different lung volume adjustments for loud speech than young adults. These results suggest that older adults have a more difficult time when the speech system is being taxed by both utterance length and loudness. The data were consistent with the hypothesis that both young and older adults use utterance length in premotor speech planning processes.     

Time course and mechanisms of decreased plasma volume during acute psychological stress and postural change in humans

In this study, we examined the effects of psychological stress on calculated plasma volume, the relationship of these changes to changes in hematologic factors, and the time course of plasma volume changes. Plasma volume changes were assessed using mass densitometry techniques, which measured changes in blood and plasma density. Hematologic and hemodynamic variables were assessed in 40 healthy men and women during a mental arithmetic (math) or benign reading task and during postural change (standing). Results indicated that math and posture change produced a significant decrease in plasma volume (ps < .001) and increases in blood pressure (ps < .001), blood and plasma density (ps < .001), and total plasma protein (p < .001). Correlations were observed between plasma volume changes and changes in systolic (r= .55, p < .0001), diastolic (r= .61, p < .0001), and mean (r= .65, p < .0001) arterial pressure during math; plasma volume and blood pressure returned to baseline within 12 min following the math task. These results suggest that an important mechanism for stress-induced decreases in plasma volume is increased blood pressure leading to increased fluid shifts from the vasculature into the interstitial spaces.     

Verbal-autonomic response dissociations as traits?

Dissociations between subjective and physiological responses to stress are of central interest in coping research. However, little is known about their stability across situations and time. Two experimental sessions - separated by 1 year - were conducted to examine cross-situational consistency and longterm-stability of HR-derived and SCL-derived dissociation scores. In year 1, a speech stressor, the cold pressor and a video stressor (viewing of the speech video) were applied. In year 2, mental arithmetics, anagrams and a torture video were presented. Thirty-five students participated and HR, SCL and negative affect were recorded. For each stressor, standardized changes in negative affect were subtracted from changes in autonomic reactivity (HR and SCL, respectively). Dissociation scores were relatively consistent across the stressors with HR-derived scores exceeding SCL-derived scores. Longterm-stability proved acceptable (r=.61, P<.001 for HR-derived and r=.40, P<.05 for SCL-derived scores). In sum, verbal-autonomic response dissociations show considerable cross-situational and temporal stability and thus might be considered as traits.     

Depressed mood is related to high-frequency heart rate variability during stressors

OBJECTIVE: The purpose of this study was to examine the relationships between depressed mood and parasympathetic control of the heart in healthy men and women at rest and during two stressors. METHODS: Fifty-three healthy college students completed a laboratory stress protocol that included a baseline resting period, a challenging speech task, and a forehead cold pressor task. Depressed mood was assessed using the Beck Depression Inventory (BDI). Parasympathetic cardiac control was measured as the high-frequency (0.12-0.40 Hz) component (HF) of heart rate variability using power spectrum analysis. Blood pressure, respiration rate, and respiration amplitude were measured simultaneously. RESULTS: Participants were categorized as having a high or low depressed mood on the basis of median splits of their BDI scores. Those in the high depressed mood group had significantly greater reductions in HF during the speech task and significantly smaller increases in HF during the forehead cold pressor task than those in the low depressed mood group. Women had significantly greater reductions in HF during the speech task and smaller increases in HF during the forehead cold pressor task than men. However, gender and depressed mood did not interact to predict changes in HF. CONCLUSIONS: Depressed mood is related to the magnitude of decrease in parasympathetic cardiac control during stressors in healthy men and women. These findings extend those of previous studies, in which a similar phenomenon was observed among patients with cardiac disease. Because the participants in this study were healthy, the relationship between depressed mood and parasympathetic cardiac control does not seem to be secondary to cardiovascular disease.     

Secretory immunoglobulin A reactions to prolonged mental arithmetic stress: inter-session and intra-session reliability.

Although previous evidence suggests that mucosal immunity may be influenced by mental stress, the importance of the duration of stress exposure on secretory immunoglobulin A (sIgA) has yet to be fully elucidated. Salivary sIgA and cardiovascular activity were measured at rest, following 14 and 28 min of mental arithmetic, and after recovery in 24 men and women on two sessions 2-4 days apart. Mental arithmetic was, on both sessions and after both the early and late phases of the task, associated with increases in sIgA concentration and sIgA secretion rate compared to rest and recovery. Task levels of sIgA concentration and sIgA secretion rate showed moderate to high intra- and inter-session test-retest reliability, while test-retest reliability was lower for change scores. Blood pressure and pulse rate were also elevated by the mental stress task, although correlational analyses revealed that stress-induced changes in sIgA were not related to cardiovascular reactions.     

Personality and physiological reactions to acute psychological stress

Stable personality traits have long been presumed to have biological substrates, although the evidence relating personality to biological stress reactivity is inconclusive. The present study examined, in a large middle aged cohort (N = 352), the relationship between key personality traits and both cortisol and cardiovascular reactions to acute psychological stress. Salivary cortisol and cardiovascular activity were measured at rest and in response to a psychological stress protocol comprising 5 min each of a Stroop task, mirror tracing, and a speech task. Participants subsequently completed the Big Five Inventory to assess neuroticism, agreeableness, openness to experience, extraversion, and conscientiousness. Those with higher neuroticism scores exhibited smaller cortisol and cardiovascular stress reactions, whereas participants who were less agreeable and less open had smaller cortisol and cardiac reactions to stress. These associations remained statistically significant following adjustment for a range of potential confounding variables. Thus, a negative personality disposition would appear to be linked to diminished stress reactivity. These findings further support a growing body of evidence which suggests that blunted stress reactivity may be maladaptive.     

Interactive effects of type A personality and psychological and physical stressors on human cardiovascular functions

The first part of this study examined the relationship(s) between Type A behavior scores and heart rate, blood pressure and impedance derived cardiovascular measures in response to discrete stressors during a standardized psychophysiological assessment. Expts. 2A and 2B considered cardiovascular responses to dynamic exercise stress alone and in combination with psychological and cold pressor tests. Gender and stroke volume changes during the psychological stress correlated 0.45 (P less than 0.02) with Type A score. Subscale scores of Job Involvement correlated 0.78 (P less than 0.02) with stroke volume, total systemic resistance and heart rate during the psychological stressor, and systolic blood pressure during the cold pressor task. The combined effects of psychological stress and dynamic exercise on systolic and diastolic blood pressure were significantly greater than the individual effects of these stressors. The use of impedance cardiography in measuring cardiovascular variables that correlate with Type A behavior, during psychophysiological assessments, may further elucidate our understanding of Type A behavior in addition to providing information about how stress interacts with aerobic exercise.     

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.     

Interactions of Respiratory and Cardiovascular Adjustments to Behavioral Stressors

The relationships among a variety of cardiovascular and respiratory measures were examined in young college males subjected to a cold pressor task, reaction-time shock avoidance task, and three levels of graded exercise. As expected, the relationships between cardiovascular (e.g., heart rate and cardiac output) and respiratory (e.g., oxygen uptake and minute ventilation) variables were tightly linear when considering rest and exercise values. However, the range of individual cardiopulmonary responses during cold pressor and reaction time was considerable, often leading to disruptions in the cardiovascular/respiratory interactions. Analyses of extreme high and low ventilation reactors during both reaction time and cold pressor revealed that the excessive ventilation responders in cold pressor showed clear signs of hyperventilation. Increases in ventilation by the high reactors during reaction time were of smaller magnitude than during cold pressor, with potential hyperventilation much less clear. Increases in minute ventilation by reactors during the cold pressor task were primarily due to large increases in tidal volume, with only modest increases in respiratory rate. For reaction time, however, the increases in ventilation by reactive individuals stemmed from rate increases with tidal volume remaining essentially unchanged.     

Heart Rate Reactivity, Behavior Pattern, and Parental Hypertension as Predictors of Cardiovascular Activity During Cognitive Challenge

Hemodynamic responses were studied during work on serial subtraction and digits backwards tasks in 99 healthy male undergraduates jointly classified as high or low heart rate reactors, Type A or Type B behavior pattern, and as having positive or negative parental history of hypertension. Heart rate, systolic blood pressure, and diastolic blood pressure were recorded, and rate pressure product was calculated at rest and during the tasks. High heart rate reactors to a cold pressor task responded with relatively higher heart rate and rate pressure product during both cognitive tasks than low heart rate reactors. Type A subjects defined by Jenkins Activity Survey did not differ from Type Bs on any of these physiological variables, although behavioral evidence demonstrated greater effort and superior performance by the Type As. Subjects with a positive parental history of hypertension manifested greater systolic and diastolic pressures and rate pressure product responses to the cognitive challenge than those lacking such parental history. These results indicate that the individual difference variables of heart rate reactivity and parental history of hypertension predicted different hemodynamic response patterns to behavioral challenge.