The stability of and intercorrelations among cardiovascular, immune, endocrine, and psychological reactivity

Responsiveness of the hypothalamic-pituitary-adrenal axis to different novel environments is a consistent individual trait in adult male outbred rats

Susceptibility to some stress-induced pathologies may be strongly related to individual differences in the responsiveness of the hypothalamic-pituitary-adrenal (HPA) axis to stressors. However, there have been few attempts in rodents to study the reliability of the individual differences in the responsiveness of the HPA to stressors and the relationship to resting corticosterone levels. In the present work, we used a normal population of Sprague-Dawley rats, with a within-subject design. Our objectives were to study: (a) the reliability of the ACTH and corticosterone response to three different novel environments widely used in psychopharmacology and (b) the relationship between stress levels of HPA hormones and the daily pattern of corticosterone secretion (six samples over a 24-h-period). Animals were repeatedly sampled using tail-nick procedure. The novel environments were the elevated plus-maze, the hole-board and the circular corridor. Animals were sampled just after 15 min exposure to the tests and again at 15 and 30 min after the termination of exposure to them (post-tests). The hormonal levels just after the tests indicate that the hole-board seems to be more stressful than the circular corridor and the elevated plus-maze, the latter being characterized by the lowest defecation rate. Correlational analysis revealed that daily pattern of resting plasma corticosterone levels did not correlate to HPA responsiveness to the tests, suggesting no relationship between resting and stress levels of HPA hormones. In contrast, the present study demonstrates, for the first time, a good within-subject reliability of the ACTH and corticosterone responses to the three environments, suggesting that HPA responsiveness to these kind of stressors is a consistent individual trait in adult rats, despite differences in the physical characteristics of the novel environments.

Mothers with breast cancer and their adult daughters: the relationship between mothers' reaction to breast cancer and their daughters' emotional and neuroimmune status

OBJECTIVES

The objectives of this study were to assess the associations between psychologic distress of patients with breast cancer and of their adult daughters; and to assess the associations between mothers' psychologic distress and daughters' psychologic distress, stress hormone levels, natural cytotoxic activity (NCA), and Th1 cytokine secretion.

METHODS

Eighty mothers with breast cancer and 80 adult daughters participated in the study. They completed the Symptom Check List (SCL-90R) questionnaire. In addition, daughters completed a set of questions on their health status and habits and on the effects of their mothers' disease on their own lives. Thirty milliliters of heparinized venous blood and a first early-morning urine sample were collected from daughters between 8:00 and 9:00 am. Spontaneous and interleukin-2 (IL-2)-induced NCA, in vitro IL-2 and IL-12 secretion, and levels of plasma cortisol and urinary catecholamines were tested in daughters. Forty-seven healthy women, age- and education- matched to daughters, completed the psychologic, immunologic, and hormonal tests, and served as a control group.

RESULTS

Psychologic distress of mothers and daughters was highly correlated. However, mothers experienced a higher level of distress than daughters. Mothers with advanced disease and their daughters were more distressed than mothers with primary disease and their daughters. Daughters' distress was also related to their subjective caregiving burden and the frequency of meetings with mothers. Higher distressed daughters had lower IL-2-induced NCA and decreased in vitro IL-2 and IL-12 secretion. Norepinephrine secretion level mediated the relationship between daughters' level of distress and their immune functions. Cortisol mediated only the relationship between daughters' distress and IL-2 secretion.

CONCLUSIONS

This initial study shows that the psychologic distress of mothers with breast cancer and that of their adult daughters are similar. Stress hormone secretions and immune functions of daughters are related to both their own and their mothers' psychologic distress.

The buffering effects of active coping on the relationship between SES and cortisol among African American young adults

Cortisol levels have consistently been related to socioeconomic status (SES). Possible moderators for this relationship are coping styles that are known to moderate relationships between cardiovascular factors and SES. The authors examined whether coping style moderated a relationship between resting cortisol levels and various measures of SES in a sample of urban, African American young adults. Those scoring low on coping style had high cortisol levels if they were currently students or unemployed. This effect, however, differed for men and women. The authors suggest that coping style may play an adaptive role regarding salivary cortisol measures in young adults when they are students or unemployed. Active coping may help protect against stress among young African American adults.

Stress responses and innate immunity: aging as a contributory factor

Evolutionary pressure has selected individuals with traits that allow them to survive to reproduction, without consideration of the consequences for the post-child rearing years and old age. In the 21st century, society is populated increasingly by the elderly and with the falling birth rate and improved health care this trend is set to continue for the foreseeable future. To minimize the potential burden on health services one would hope that 'growing old gracefully' should also mean 'growing old healthily'. However, for too many the aging process is accompanied by increasing physical and mental frailty producing an elevated risk of physical and psychological stress in old age. Stress is a potent modulator of immune function, which in youth can be compensated for by the presence of an optimal immune response. In the elderly the immune response is blunted as a result of the decline in several components of the immune system (immune senescence) and a shifting to a chronic pro-inflammatory status (the so-called 'inflamm-aging' effect). We discuss here what is known of the effects of both stress and aging upon the innate immune system, focusing in particular upon the age-related alterations in the hypopituitary-adrenal axis. We propose a double hit model for age and stress in which the age-related increase in the cortisol/sulphated dehydroepiandrosterone ratio synergizes with elevated cortisol during stress to reduce immunity in the elderly significantly.

Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry

The present report meta-analyzes more than 300 empirical articles describing a relationship between psychological stress and parameters of the immune system in human participants. Acute stressors (lasting minutes) were associated with potentially adaptive upregulation of some parameters of natural immunity and downregulation of some functions of specific immunity. Brief naturalistic stressors (such as exams) tended to suppress cellular immunity while preserving humoral immunity. Chronic stressors were associated with suppression of both cellular and humoral measures. Effects of event sequences varied according to the kind of event (trauma vs. loss). Subjective reports of stress generally did not associate with immune change. In some cases, physical vulnerability as a function of age or disease also increased vulnerability to immune change during stressors.

Psychological stress and the human immune system: a meta-analytic study of 30 years of inquiry

The present report meta-analyzes more than 300 empirical articles describing a relationship between psychological stress and parameters of the immune system in human participants. Acute stressors (lasting minutes) were associated with potentially adaptive upregulation of some parameters of natural immunity and downregulation of some functions of specific immunity. Brief naturalistic stressors (such as exams) tended to suppress cellular immunity while preserving humoral immunity. Chronic stressors were associated with suppression of both cellular and humoral measures. Effects of event sequences varied according to the kind of event (trauma vs. loss). Subjective reports of stress generally did not associate with immune change. In some cases, physical vulnerability as a function of age or disease also increased vulnerability to immune change during stressors.

Acute stressors and cortisol responses: a theoretical integration and synthesis of laboratory research

This meta-analysis reviews 208 laboratory studies of acute psychological stressors and tests a theoretical model delineating conditions capable of eliciting cortisol responses. Psychological stressors increased cortisol levels; however, effects varied widely across tasks. Consistent with the theoretical model, motivated performance tasks elicited cortisol responses if they were uncontrollable or characterized by social-evaluative threat (task performance could be negatively judged by others), when methodological factors and other stressor characteristics were controlled for. Tasks containing both uncontrollable and social-evaluative elements were associated with the largest cortisol and adrenocorticotropin hormone changes and the longest times to recovery. These findings are consistent with the animal literature on the physiological effects of uncontrollable social threat and contradict the belief that cortisol is responsive to all types of stressors.

Acute stress affects heart rate variability during sleep

OBJECTIVE

Although stress can elicit profound and lasting effects on sleep, the pathways whereby stress affects sleep are not well understood. In this study, we used autoregressive spectral analysis of the electrocardiogram (EKG) interbeat interval sequence to characterize stress-related changes in heart rate variability during sleep in 59 healthy men and women.

METHODS

Participants (N = 59) were randomly assigned to a control or stress condition, in which a standard speech task paradigm was used to elicit acute stress in the immediate presleep period. EKG was collected throughout the night. The high frequency component (0.15-0.4 Hz Eq) was used to index parasympathetic modulation, and the ratio of low to high frequency power (0.04-0.15 Hz Eq/0.15-0.4 Hz Eq) of heart rate variability was used to index sympathovagal balance.

RESULTS

Acute psychophysiological stress was associated with decreased levels of parasympathetic modulation during nonrapid eye movement (NREM) and rapid eye movement sleep and increased levels of sympathovagal balance during NREM sleep. Parasympathetic modulation increased across successive NREM cycles in the control group; these increases were blunted in the stress group and remained essentially unchanged across successive NREM periods. Higher levels of sympathovagal balance during NREM sleep were associated with poorer sleep maintenance and lower delta activity.

CONCLUSIONS

Changes in heart rate variability associated with acute stress may represent one pathway to disturbed sleep. Stress-related changes in heart rate variability during sleep may also be important in association with chronic stressors, which are associated with significant morbidity and increased risk for mortality.

Reactivity of immune, endocrine and cardiovascular parameters to active and passive acute stress

This study clarified associations among immune, autonomic, and endocrine activities during mental arithmetic and cold pressor stress tasks in 26 women in the follicular phase. Both tasks decreased CD3+ T cells, CD4+ T cells, and CD19+ B cells, whereas they increased lymphocytes, granulocytes, NK cells, and NK cell activity (NKCA). The mental arithmetic task had a greater impact than the cold pressor task on changes in CD3+ T cells and in NK cells. Cardiovascular reactivity to active stress was associated with increased NK cells and decreased CD3+ T cells. Reduced cortisol levels during passive stress were associated with decreased CD19+ B cells and with increased NK cells. The merits of this study are that it controlled the following factors. Perceived stress during the two tasks was matched; both tasks lasted long enough to elicit high-magnitude responses; and the length of the intervening rest period minimized probable carryover effects between tasks.

Stable individual differences in physiological response to stressors: implications for stress-elicited changes in immune related health

Stress reactivity refers to a stable individual difference in response to stressors. This article addresses three questions about reactivity: (1) Are cardiovascular, endocrine, and immune responses to acute laboratory stressors stable over time and across stressor tasks? (2) Are cardiovascular, endocrine, and immune reactors the same people? and (3) Are reactive people more vulnerable to stressor-induced effects on susceptibility to infectious disease? We conclude that for many individual indicators of physiological responsiveness to stressors there is moderate stability over time and across stressor tasks indicating the possible existence of underlying dispositional characteristics; the commonality of immune and cardiovascular and hormonal responses to stress depend on the nature of regulation of the immune response being assessed; reactivity appears to have implications for vulnerability to stressor-associated disease risk (stress-by-reactivity interaction) in the natural environment, but the exact nature of this vulnerability is not as yet entirely clear.

Socioeconomic status, C-reactive protein, immune factors, and responses to acute mental stress

Low socioeconomic status (SES) is associated with increased risk of coronary heart disease and immune-related disorders. We hypothesised that SES would be inversely associated with the acute phase reactant C-reactive protein (CRP) and with circulating lymphocyte levels, and that lymphocyte responses to acute psychological stress would also vary with SES. CRP was obtained from 226, and lymphocyte counts from 127 healthy volunteers from the Whitehall II cohort, and SES was defined primarily by grade of employment. CRP concentration was greater in lower compared with higher SES participants (1.18+/-0.75 vs. 0.75+/-0.8 mg/l,p=.002) independently of sex, age, body mass, waist/hip ratio, smoking, alcohol, and season of the year. Similar differences were evident when SES was defined by income and educational attainment. Higher SES was also associated with lower total lymphocyte (p=.023), T-lymphocyte (p=.024) and natural killer (NK) cell counts (p=.006). Total, T- and B-lymphocyte, and NK cell counts increased with stress, but immune stress reactivity did not vary with SES. Post-stress recovery was delayed in women compared with men. The results suggest that moderate inflammation and immune activation may be processes through which lower SES increases disease risk.

Neuroendocrine and cardiovascular reactivity to stress in mid-aged and older women: long-term temporal consistency of individual differences

We report long-term temporal consistency of stress-related neuroendocrine and cardiovascular variables in mid-aged and older women who performed mental math and speech stress tasks two times approximately 1 year apart. Epinephrine, norepinephrine, ACTH, cortisol, cardiac preejection period (PEP), respiratory sinus arrhythmia, heart rate (HR), blood pressure, and respiration rate were measured at baseline, after or during stressors, and 30 min posttask. Although there were exceptions, year-to-year Spearman coefficients showed mostly moderate to high consistency (rs approximately equal to .5-.8) for baseline, stressor, and posttask values. For reactivity, HR and PEP were most consistent (rs approximately equal to .65); consistency for other variables was moderate to low (rs approximately equal to .1-.4). Means of most variables changed from year to year. Results support the use of baseline, stressor, and posttask values in longitudinal studies.

Natural killer cell and proinflammatory cytokine responses to mental stress: associations with heart rate and heart rate variability

Associations between natural killer (NK) cell, proinflammatory cytokine stress responsivity, and cardiac autonomic responses (indexed by heart rate and heart rate variability) were assessed in 211 middle-aged men and women. Blood was drawn at baseline, immediately following color-word interference and mirror tracing tasks for the assessment of NK cell numbers, and 45 min post-stress for assessing plasma interleukin 6 (IL-6) and tumor necrosis factor alpha (TNFalpha) responses. Heart rate variability was measured as the root mean square of successive differences (RMSSD) in R-R intervals. Increases in NK cell counts following stress were positively associated with heart rate responses independently of age, sex, socioeconomic status, smoking, and change in hematocrit. Heart rate 45 min post-stress was positively associated with plasma IL-6 post-stress, and with TNFalpha changes from baseline, independently of covariates. No relationship between immune responses and heart rate variability was observed. We conclude that individual differences in sympathetically-driven cardiac stress responses are associated with NK and proinflammatory cytokine responses to psychological stress.

Stress-related immune changes in middle-aged and older women: 1-year consistency of individual differences

This study reviews prior research and reports longer-term consistency of stress-related immune variables in middle-aged and older women who performed mental math and speech tasks 2 times 1 year apart. Leukocyte subsets, mitogen-induced lymphocyte proliferation, and natural killer cell activity were measured at baseline, after tasks, and after 30-min recovery. Epstein-Barr virus (EBV) antibody titers were assessed at baseline. Pearson coefficients and standardized maximum-likelihood estimates of year-to-year covariances for leukocyte subsets and EBV titers showed moderately high to high baseline and posttask consistency and lower recovery consistency; consistency for other functional immune assays and reactivity scores for all variables was moderate to low. Results support longitudinal study of psychosocial context effects on tonic immune function and posttask scores.

Temporal stability of acute stress-induced changes in leukocyte subsets and cellular adhesion molecules in older adults

This study investigated the temporal stability of enumerative immune and catecholamine responses to acute psychosocial stress in 67 Alzheimer's caregivers ages 56-82 years (45 women and 22 men) who were required to prepare and deliver two 3-min speeches on three occasions at 2-week and 6-week intervals. All leukocyte subsets and adhesion molecules (CD62L and CD11a) changed significantly from rest to postspeak at each of the three testing sessions (p's <.0005). Responses showed moderate to high temporal stability across baseline and absolute task values (r's =.65-.96). Reliability was predictably lower for both forms of change scores (r's = -.16-.64). The level of temporal stability achieved is comparable to that seen previously in younger adults, indicating that acute psychosocial stress produces reliable changes in circulating leukocytes and cell adhesion molecules in older adults.

Reactivity and vulnerability to stress-associated risk for upper respiratory illness

OBJECTIVE

We tested the hypothesis that the greater a person's laboratory stress-elicited elevation in cortisol, the greater the life stress-related risk for upper respiratory infection (URI). We also tested the prediction that the greater the laboratory stress-elicited rise in natural killer cell (NK) cytotoxicity, the smaller the life stress-related URI risk. Finally, we explored whether sympathetic nervous system (SNS) and enumerative immune reactivities to laboratory stress moderate the relation between life stress and URI.

METHODS

At baseline, 115 healthy subjects were administered a negative stressful life events checklist and were tested to assess their SNS (blood pressure, heart rate, and catecholamines), HPA (cortisol), and immune (NK cell cytotoxicity and lymphocyte subsets) reactivities to laboratory speech tasks administered 2 weeks apart. Responses were averaged across the two laboratory assessments to create reactivity scores. After these assessments were completed, participants were followed weekly for 12 consecutive weeks. At each follow-up they completed a measure of perceived stress experienced over the last week. They were also instructed to contact the study coordinator if they had a cold or flu at any time during follow-up. A health care worker verified reported illnesses.

RESULTS

In a traditional prospective analysis, high cortisol reactors with high levels of life events had a greater incidence of verified URI than did high reactors with low levels of life events and low reactors irrespective of their life event scores. Using hierarchical linear modeling, CD8(+) number, Natural Killer (NK) cell number, and NK cell cytotoxicity, each interacted with weekly perceived stress levels in predicting concurrent occurrences of self-reported URIs. For these outcomes, low immune reactors were more likely to experience an URI during high stress than low stress weeks. High immune reactors did not exhibit differences in weekly URIs as a function of weekly stress level. The SNS reactivity markers did not moderate the association of stress and URI incidence in either analysis.

CONCLUSIONS

Acute HPA and immune responses to laboratory stressors are markers of how vulnerable people are to the increased risk for URI associated with stressors in the natural environment.

Implicit anxiety measure predicts cardiovascular reactivity to an evaluated speaking task

Explicit personality tests assess introspectively accessible self-descriptions. By contrast, implicit personality tests assess introspectively inaccessible processes that operate outside of awareness. Despite their inaccessibility, implicit processes are presumed to influence a variety of current responses. This study tested the hypothesis that an implicit anxiety test should predict cardiovascular reactivity during a speech stressor task. In all, 97 participants completed a measure of attention allocation toward threat (implicit test) and an anxiety questionnaire (explicit test) 1 week before giving an evaluated speech. Whereas the explicit test showed modest relations within only 1 measure of cardiovascular reactivity, the implicit test predicted heart rate and blood pressure reactivity during preparation and delivery of the speech. These findings encourage the broader use of implicit measures to assess cardiovascular responses to threat.