Psychophysiological correlates of individual differences in patterns of hemodynamic reactivity

OLD IDEAS, NEW DIRECTIONS: RE-EXAMINING THE PREDICTIVE UTILITY OF THE HEMODYNAMIC PROFILE OF THE STRESS RESPONSE IN HEALTHY POPULATIONS

The 'reactivity hypothesis' has a long and fruitful history in health psychology and behavioural medicine, with elements of its thesis taken as core and others lost in the plethora of research on its utility as a theory of psychosomatic disease. One such thesis is that the underlying hemodynamic profile of the stress response may be particularly revealing when detailing the impact of psychological stress on the development of cardiovascular disease. This paper re-examines old ideas surrounding the hemodynamic profile of the stress response, asking why its health-predictive properties were never fully explored. Further, this paper reviews the evidence that a vascular profile of stress responding may be especially predictive of disease development, particularly in the case of hypertension. In addition, measurement of hemodynamic profile as well as its known psychosocial moderators are reviewed including how examination of patterns of cardiovascular-stress response adaptation may extend the field. This paper highlights that the extension of the reactivity hypothesis to include both hemodynamic profile and patterns of cardiovascular stress-response adaptation may hold much explanatory power in detailing the impact of how stress responding and stress tolerance promotes disease development.

Evaluation of the effects of food intake on task engagement based on psychophysiological states

The objective of this study was to evaluate the effects of food intake on performance and task engagement based on psychophysiological states. The experiment was conducted under two conditions: taking a break with his eyes opened between the repeated tracking tasks (Control), and taking a break with food intake (Intake). We found the rate of deterioration of the distance between target pointer and the mouse cursor, a performance index, showed significant differences between the two conditions. Significant differences were also found between the two conditions in all assessment items of subjective feelings. Considering the hemodynamic parameters and nasal skin temperature responses, it was found that the approach to the second task was different in the two conditions. Therefore, due to food intake between repeated tasks, psychological responses such as “Awareness” and “Refreshment” were maintained. Hence, it was confirmed that food intake stimulated positive task engagement in the task and maintained performance.

High Prevalence of Insecure Attachment in Patients with Primary Hypertension

Hypertension is a major cardiovascular (CV) risk factor and is predicted by heightened CV reactivity to stress in healthy individuals. Patients with hypertension also show an altered stress response, while insecure attachment is linked to a heightened stress reactivity as well. This is the first study aiming to assess attachment representations in patients with primary hypertension and to investigate their CV responses when their attachment system is activated. We studied 50 patients (38 men, 12 women) with primary hypertension. The Adult Attachment Projective Picture System (AAP), a widely used and validated interview, was performed to measure the patients' attachment representations, and to activate their attachment system. Blood pressure and heart rate were measured after 10 min at rest prior to and directly after the AAP interview. Mood and state anxiety were assessed using the Multidimensional Mood State Questionnaire (MDBF) and the State Trait Anxiety Inventory-State (STAI-S) before and after the experiment. The prevalence of insecure attachment (dismissing, preoccupied, unresolved) in hypertensive patients was predominant (88%), while in non-clinical populations, only about 50% of individuals had insecure attachment patterns. Blood pressure (p < 0.001), heart rate (p = 0.016), and rate pressure product (p < 0.001) significantly increased in response to the attachment interview. Secure attached patients showed the highest rise in systolic blood pressure (p = 0.020) and the lowest heart rate compared to the other attachment groups (p = 0.043). However, attachment representation showed no significant group or interaction effects on diastolic blood pressure (DBP) and rate pressure product. Insecure attachment was highly over-represented in our sample of patients with primary hypertension. Additionally, a robust CV response to the attachment-activating stimulus was observed. Our data suggest that insecure attachment is significantly linked to primary hypertension, which implies the need for further investigations to evaluate attachment insecurity as a possible risk factor for hypertension.

Cardiovascular responses to stress in Singapore and India

BACKGROUND

Epidemiological studies have shown significant ethnic differences in coronary heart disease death rates with South Asians showing significantly greater coronary heart disease mortality than other groups.

PURPOSE

This research examined ethnic differences in cardiovascular reactivity (CVR) among Chinese, Malays and Indians in Singapore as well as a sample of Indians living in India.

METHODS

Experiment 1 examined differences across 303 Chinese, Malay and Indian undergraduates in Singapore, while Experiment 2 looked at differences in CVR between Indian participants from Singapore, and 145 Indians living in India. Systolic and diastolic blood pressure (SBP, DBP), heart rate (HR), cardiac index (CI) and total peripheral resistance index (TPRI) were measured during baselines and five laboratory tasks.

RESULTS

Ethnicity main effects for SBP and CI reactivity were obtained in Experiment 1, with Indians showing significantly lower BP and CI reactivity than the Chinese and Malays. Significant main effects for sex were found with females showing lower reactivity than males for TPRI, and greater reactivity than males for HR and CI. Experiment 2 found that participants from India showed higher reactivity for SBP, HR and CI, while Indian participants from Singapore showed higher TPRI reactivity. These differences, however, often varied by task.

CONCLUSIONS

These results point to differences in CVR among ethnic groups in Singapore as well as between Indians living in India and those living in Singapore. These differences may reflect cultural differences and need to be explored further with respect to their relationship to different rates of coronary heart disease among these groups.

Evaluation of the anaesthetic properties and tolerance of 1:100,000 articaine versus 1:100,000 lidocaine. A comparative study in surgery of the lower third molar

OBJECTIVES

To evaluate the anaesthetic properties and tolerance of articaine versus lidocaine at equal vasoconstrictor concentration.

STUDY DESIGN

A total of 96 male and female patients who underwent surgical treatment of the lower third molar participated. Patients were randomly assigned to articaine hydrochloride with epinephrine 1:100,000 and lidocaine hydrochloride with epinephrine 1:100,000. The variables analysed were latency period, duration of anaesthetic effect, tolerance and adverse reactions.

RESULTS

Both the latency period and the duration of anaesthetic effect were greater for articaine, although the differences were not statistically significant. Latency: mean difference of 2.70 ± 2.12 minutes (95%CI of -1.51 minutes - 6.92 minutes).

DURATION

mean difference of -33 minutes 5 seconds ± 31 minutes (95% CI -1 hour 35 minutes - 29 minutes). There were 4 adverse events that did not require the patients to be withdrawn from the study.

CONCLUSIONS

The anaesthetics in this study have very similar properties for use in surgery and have demonstrated a good safety and tolerability profile.

Genetic influences on cardiovascular stress reactivity

Individual differences in the cardiovascular response to stress play a central role in the reactivity hypothesis linking frequent exposure to psychosocial stress to adverse outcomes in cardiovascular health. To assess the importance of genetic factors, a meta-analysis was performed on all published twin studies that assessed heart rate (HR) or blood pressure (BP) reactivity to the cold pressor test or various mental stress tasks. For reactivity to mental stress, the pooled heritability estimate ranged from 0.26 to 0.43. Reactivity to the cold pressor test yielded heritability estimates from 0.21 to 0.55. An ensuing review of genetic association studies revealed a number of genes, mostly within the sympathoadrenal pathway, that may account for part of the heritability of cardiovascular stress reactivity. Future progress in gene finding, that should include measures of sympathetic and vagal stress reactivity, may help uncover the molecular pathways from genetic variation to stress reactivity.

Comparison of Stress Responses between Mental Tasks and White Noise Exposure

The purpose of this study was to compare the cardiovascular responses to different types of mental stress. Ten healthy males performed a mental arithmetic task (MA) on one day and were exposed to white noise (WN, 80dB) on another day. Both the MA and the WN were composed of four 5-min consecutive periods with a 3-min rest between them. On each day, the systolic and diastolic blood pressure (SBP and DBP), mean arterial pressure (MAP), cardiac output (CO), and total peripheral resistance (TPR) were measured continually during the entire experimental period. The changes from the baseline (Delta) in all periods were calculated for both mental stresses. As for the results, the DeltaMAP, DeltaCO, DeltaHR, and DeltaTPR in the MA did not significantly change during the task periods. However, in the WN, the DeltaMAP and DeltaTPR showed significant increases over the time of the consecutive periods. In addition, we discuss the response patterns for the two mental stresses. We examine three hemodynamic reactivity patterns: a cardiac pattern characterized by increased CO and decreased TPR, a mixed pattern characterized by a moderate increase in both CO and TPR, and a vascular pattern characterized by increased TPR and decreased CO. The results show that throughout all task/exposure periods, the response pattern remained the same for six subjects in each stress. Furthermore, of these six subjects, half showed the same response pattern in both the MA and the WN. In conclusion, compared to the MA task, consecutive WN exposure showed an accumulation of stress responses. A change in TPR contributed to a gradual increase in MAP in the WN. It is also possible that among the subjects there were different types of response to the MA and WN.

Different Types of Circulatory Responses to Mental Tasks

The present study investigated the circulatory responses to two mental tasks. Forty males and females performed a mental subtraction task and a color-word task. During each task, the systolic and diastolic blood pressure, mean arterial pressure, heart rate, stroke volume, cardiac output, and total peripheral resistance were measured as cardiovascular indices for a 5-min baseline, a 5-min task period, and a 10-min recovery period. As for the results, three hemodynamic reactivity patterns were verified: Pattern C, characterized by increased cardiac output and decreased total peripheral resistance; Pattern M, characterized by a moderate increase in both cardiac output and total peripheral resistance; and Pattern V, characterized by increased total peripheral resistance and decreased cardiac output. Also, four response types were found among all subjects: Type 1: cardiovascular responses showed the cardiac pattern for both tasks; Type 2: cardiovascular responses changed between the cardiac pattern and the mixed pattern with a change of tasks; Type 3: cardiovascular responses showed the mixed pattern for both tasks; Type 4: cardiovascular responses changed between the mixed pattern and the vascular pattern with a change of tasks. The comparison between types showed that Type 3 and Type 4 had an elevation in their blood pressure by an increased total peripheral resistance. On the other hand, Type 1 and Type 2 tended to have an increased blood pressure by a rise in their cardiac output. And Type 3 and Type 4 showed higher blood pressure and higher scores on the Type A behavior pattern questionnaire. In conclusion, at least four types of circulation response to the mental tasks existed, with Type 3 and Type 4 having higher blood pressure responses and tending to have an elevated blood pressure by a rise in their total peripheral resistance.

Temporal stability of ambulatory stroke volume and cardiac output measured by impedance cardiography

Recently, devices have become available that allow non-invasive measurement of stroke volume and cardiac output through ambulatory thorax impedance recording. If such recordings have adequate temporal stability, they offer great potential to further our understanding of how repeated or chronic cardiovascular activation in response to naturalistic events may contribute to cardiovascular disease. In this study, 24 h ambulatory impedance-derived systolic time intervals, stroke volume and cardiac output were measured in 65 healthy subjects across an average time span of 3 years and 4 months. Stability was computed separately for sleep and daytime recordings. To avoid confounding by differences in posture and physical activity across measurement days, temporal stability was computed using sitting activities only. During the day intraclass correlations were moderate for stroke volume (.29-.46) and cardiac output (.33-.46) and good for systolic time intervals (.55-.81). When test-retest comparison was limited to two comparable days (two work days or two leisure days), correlations for both SV (.42-.46) and CO (.43-.50) improved.

CONCLUSION

Moderate long-term temporal stability is found for individual differences in ambulatory stroke volume and cardiac output measured by impedance cardiography.

Approach to human adaptability to stresses of city life

Interest of human adaptability to city life is one of the most principal topics of physiological anthropology. Especially, cultural adaptation and flowing stresses by itself is the most important viewpoint of human adaptability in the recent modern life. In this paper, the authors reviewed the keywords of physiological anthropology, especially with the focus on techno-adaptability, and presented our experimental trials to study physiological polymorphism of cardio-vascular reactivity to mental stresses. We scoped the psychological stresses by means of mental tasks as an experimental model of techno-stress. Techno-stress was defined as not only from inadequate interface of man-machine system, but also from increased social complexity owing to highly advanced technological social system. In the experimental trial, we observed different types of cardio-vascular responses to several mental tasks. Blood pressure rose significantly during the tasks. However, contribution of change in cardiac output and total peripheral resistance on it was not the same between subgroups of the subjects.

The biological aspects of physiological anthropology with reference to its five keywords

The methodology of physiological anthropology has been defined in the capacity of an independent academic field by five keywords: environmental adaptability, technological adaptability, physiological polymorphism, whole-body coordination and functional potentiality, clearly suggesting the direction of approach to human beings in the field of physiological anthropology. Recently, these keywords have attracted a great deal of attention from physiological anthropologists in Japan. Physiological anthropology is based on a biological framework. From the viewpoint of biology, it is essential to discuss the biological function of human behavior. In this brief conceptual manuscript, the biological aspects of physiological anthropology are discussed in relation to the five keywords.

Dominance hierarchy influences adult neurogenesis in the dentate gyrus

Many mammalian species form dominance hierarchies, but it remains unknown whether differences in social status correspond to structural differences in the brain. Stressful experiences may arise naturally during the establishment of dominance, and stress has been linked to adult neurogenesis in the hippocampus. To determine whether position in a dominance hierarchy leads to changes in adult neurogenesis in the hippocampus, we examined the brains of rats housed in a visible burrow system (VBS), a seminaturalistic environment with opportunities for social interaction. Dominance hierarchies emerged among the males in all colonies within 3 d of living in the VBS. Although cell proliferation in the dentate gyrus did not differ between the groups, more new neurons were observed in the dentate gyrus of the dominant males compared with both subordinates and controls. Dominant and subordinate animals showed similar basal, stress, and recovery from stress levels of corticosterone, as well as similar thymus, adrenal gland, and body weights, suggesting that variables other than stress are responsible for the observed changes in adult neurogenesis. The differences in brain structure persisted among the animals that had no access to the burrow system after the dominance hierarchy stabilized, suggesting that social status rather than living in a complex environment accounts for the effect of dominance on adult neurogenesis.

Heart rate variability

BACKGROUND

The authors conducted a study to evaluate the sensitivity of heart rate variability, or HRV, in quantifying the cardiocirculatory reaction to dental stress compared with other clinical parameters more frequently used in clinical practice.

METHODS

Twenty-five healthy subjects (15 men and 10 women aged 19 through 73 years) who underwent dental extractions were enrolled in the study. The authors measured systolic blood pressure, or SBP; diastolic blood pressure, or DBP; heart rate, or HR; and HRV at baseline, immediately after local anesthetic was administered, during the dental extraction and five minutes after the dental extraction. Time domain measures of HRV were based on interbeat intervals and were obtained by using standard deviations of the R-R intervals, which were calculated during a five-minute period in a continuous electrocardiographic record.

RESULTS

Analysis of variance for repeated measures showed no time-related difference between the four study periods with regard to SBP and DBP. However, HR values were significantly different in three of the four periods, and HRV values were significantly different in all four testing periods. Furthermore, HRV values exhibited greater variability in the maximum changes recorded during dental extractions compared with HR values (0 to 80 milliseconds versus 0 to 31 beats/minute, respectively).

CONCLUSIONS

HRV is a highly sensitive parameter for quantifying the sympathetic drive to the heart during a cardiovascular reaction to a dental operation.

CLINICAL IMPLICATIONS

Clinicians may find that HRV evaluation is useful in monitoring patients with heart disease to detect early signs of cardiac impairment related to local, high sympathetic activity and to prevent cardiovascular emergencies.

Ethnicity, gender, and age effects on adrenoceptors and physiological responses to emotional stress

We examined the unique and joint effects of ethnicity, gender, and age on cardiovascular and catecholamine responses to the anger recall interview, and beta(2)-adrenergic receptor density and function on peripheral blood mononuclear cells. Participants were 179 nonsmoking, normotensive men and women aged 18-49 years. All subjects showed similar blood pressure increases during the anger recall interview. Black men, however, showed the smallest increases in heart rate in conjunction with an attenuated peripheral vasodilatation. Black women and Whites showed similar increases in heart rate and peripheral vasodilatation. Increasing age was associated with greater norepinephrine increases to anger recall in Black males. Black men also exhibited higher epinephrine levels throughout the protocol, higher dissociation constant to (125)I-pindolol, and age-dependent increases in beta(2)-receptor density. Relative to Whites and Black females, arousal of negative affect in Black males led to a pattern of sympathetic nervous system activity that may help explain the higher prevalence of hypertension in this population.

Blood pressure and muscle sympathetic nerve activity during cold pressor stress: fitness and gender

We examined putative autonomic and hemodynamic mechanisms that might explain our prior finding that cardiorespiratory fitness mitigates blood pressure responses by normotensive women during the hand cold pressor test. We report that fitness level was inversely related to increases in systolic and diastolic blood pressures and muscle sympathetic nerve activity (MSNA) during the cold pressor among women but not men. The pattern of responses among fitter women was consistent with decreased central sympathetic outflow resulting in reduced stroke volume or dampened peripheral resistance in vascular beds other than calf skeletal muscle. Fitter men and women had slightly larger increases in blood pressure during mental arithmetic, but otherwise fitness was not directly related to stress responses. The results further encourage consideration of cardiorespiratory fitness as a modifying covariate when the hand cold pressor test is used as a predictor of future hypertension among women.

Socioeconomic status and hemodynamic recovery from mental stress

We assessed the changes in cardiac index and total peripheral resistance underlying blood pressure reactions and recovery from acute mental stress, in relation to socioeconomic status. A sample of 200 men and women aged 47-59 years was divided on the basis of occupation into higher, intermediate, and lower socioeconomic status groups. Blood pressure was monitored using the Portapres, and hemodynamic measures were derived by Modelflow processing of the arterial pressure waveform. Blood pressure increases during two stressful behavioral tasks were sustained by increases in cardiac index and total peripheral resistance. During the 45-min posttask recovery period, cardiac index fell below baseline levels, whereas peripheral resistance remained elevated. Peripheral resistance changes during recovery varied with socioeconomic status and blood pressure stress reactivity, with particularly high levels in reactive low status participants. Results are consistent with the hypothesis that disturbances of stress-related autonomic processes are relevant to the social gradient in cardiovascular disease risk.

Interindividual differences in sympathetic and effector responses to arousal in humans

Surprising sensory stimuli have been found to attenuate one or two sympathetic discharges in human muscle nerves of some, but not all subjects, an effect suggested to be due to arousal. The aims of the present study were: (1) to provide evidence for or against an arousal mechanism by searching for evidence of habituation, and (2) to investigate if the presence or absence of inhibitory response is reproducible. To this end we recorded peroneal muscle sympathetic nerve activity (MSNA), electrocardiogram (ECG), finger blood pressure and changes of skin electrical resistance in 17 awake healthy subjects, while sensory stimuli consisting of five electrical pulses were delivered to a finger. The electrical pulses were triggered on five consecutive R waves of the ECG after a delay of 200 ms. Dummy stimuli, consisting of five trigger pulses without electrical pulses were used as controls, and the interval between two successive stimuli (real or dummy) was 30 s. On a group basis, the stimuli attenuated two initial and one late MSNA bursts. On an individual basis, significant attenuation of one or two initial bursts occurred in eight subjects, whereas in nine subjects there was no significant inhibition. In nine subjects the experiments were repeated once and in three subjects they were repeated twice. The effects on MSNA were reproducible in 11 of the12 subjects. In the group of subjects without significant MSNA inhibition the stimuli induced a small, transient increase in mean blood pressure, which was not present in the group with significant MSNA inhibition. Heart rate did not change in either group. In conclusion, the inhibitory effect on MSNA of five repeated electrical pulses to a finger is largely similar to that previously shown for one pulse, i.e. there is rapid habituation of the response, compatible with an arousal-induced effect. The inhibitory responsiveness shows marked interindividual differences, which are reproducible over several months and associated with different effects on blood pressure.