Haemodynamic adjustments to mental stress in normotensives and subjects with mildly elevated blood pressure

Physiological reactivity to acute mental stress in essential hypertension-a systematic review

Objective

Exaggerated physiological reactions to acute mental stress (AMS) are associated with hypertension (development) and have been proposed to play an important role in mediating the cardiovascular disease risk with hypertension. A variety of studies compared physiological reactivity to AMS between essential hypertensive (HT) and normotensive (NT) individuals. However, a systematic review of studies across stress-reactive physiological systems including intermediate biological risk factors for cardiovascular diseases is lacking.

Methods

We conducted a systematic literature search (PubMed) for original articles and short reports, published in English language in peer-reviewed journals in November and December 2022. We targeted studies comparing the reactivity between essential HT and NT to AMS in terms of cognitive tasks, public speaking tasks, or the combination of both, in at least one of the predefined stress-reactive physiological systems.

Results

We included a total of 58 publications. The majority of studies investigated physiological reactivity to mental stressors of mild or moderate intensity. Whereas HT seem to exhibit increased reactivity in response to mild or moderate AMS only under certain conditions (i.e., in response to mild mental stressors with specific characteristics, in an early hyperkinetic stage of HT, or with respect to certain stress systems), increased physiological reactivity in HT as compared to NT to AMS of strong intensity was observed across all investigated stress-reactive physiological systems.

Conclusion

Overall, this systematic review supports the proposed and expected generalized physiological hyperreactivity to AMS with essential hypertension, in particular to strong mental stress. Moreover, we discuss potential underlying mechanisms and highlight open questions for future research of importance for the comprehensive understanding of the observed hyperreactivity to AMS in essential hypertension.

Comparison of TWA and PEP as indices of α2- and ß-adrenergic activation

RATIONALE

Pre-ejection period (PEP) and T-wave amplitude (TWA) have been used to assess sympathetic nervous system (SNS) activity. Here we report two single-blinded, placebo-controlled intravenous (IV) drug application studies in which we pharmacologically modified SNS activity with epinephrine (study 1) as well as dexmedetomidine (alpha2-agonist) and yohimbine (alpha2-antagonist) (study 2). Restricted heart rate (HR) intervals were analyzed to avoid confounding effects of HR changes.

OBJECTIVE

Study 1 served to replicate previous findings and to validate our approach, whereas study 2 aimed to investigate how modulation of central SNS activity affects PEP and TWA.

METHODS

Forty healthy volunteers (58% females) participated in study 1 (between-subject design). Twelve healthy men participated in study 2 (within-subject design). TWA and PEP were derived from ECG and impedance cardiography, respectively.

RESULTS

Epinephrine shortened PEP and induced statistically significant biphasic TWA changes. However, although the two alpha2-drugs significantly affected PEP as expected, no effects on TWA could be detected.

CONCLUSION

PEP is better suited to reflect SNS activity changes than TWA.

Cardiovascular Stress Reactivity and Health: Recent Questions and Future Directions

OBJECTIVE

High cardiovascular reactions to psychological stress are associated with the development of hypertension, systemic atherosclerosis, and cardiovascular disease. However, it has become apparent that low biological stress reactivity also may have serious consequences for health, although less is known about the mechanisms of this. The objectives of this narrative review and opinion article are to summarize and consider where we are now in terms of the usefulness of the reactivity hypothesis and reactivity research, given that both ends of the reactivity spectrum seem to be associated with poor health, and to address some of the key criticisms and future challenges for the research area.

METHODS

This review is authored by the members of a panel discussion held at the American Psychosomatic Society meeting in 2019, which included questions such as the following: How do we measure high and low reactivity? Can high reactivity ever indicate better health? Does low or blunted reactivity simply reflect less effort on task challenges? Where does low reactivity originate from, and what is a low reactor?

RESULTS

Cardiovascular (and cortisol) stress reactivity are used as a model to demonstrate an increased understanding of the different individual pathways from stress responses to health/disease and show the challenges of how to understand and best use the reconstruction of the long-standing reactivity hypothesis given recent data.

CONCLUSIONS

This discussion elucidates the gaps in knowledge and key research issues that still remain to be addressed in this field, and that systematic reviews and meta-analyses continue to be required.

Preejection Period as a Sympathetic Activity Index: a Role of Confounding Factors

In previous studies, one of the systolic time intervals – preejection period (PEP) – was used as an index of sympathetic activity reflecting the cardiac contractility. However, PEP could be also influenced by several other cardiovascular variables including preload, afterload and diastolic blood pressure (DBP). The aim of this study was to assess the behavior of the PEP together with other potentially confounding cardiovascular system characteristics in healthy humans during mental and orthostatic stress (head-up tilt test – HUT). Forty-nine healthy volunteers (28 females, 21 males, mean age 18.6 years (SD=1.8 years)) participated in the study. We recorded finger arterial blood pressure by volume-clamp method (Finometer Pro, FMS, Netherlands), PEP, thoracic fluid content (TFC) – a measure of preload, and cardiac output (CO) by impedance cardiography (CardioScreen® 2000, Medis, Germany). Systemic vascular resistance (SVR) – a measure of afterload – was calculated as a ratio of mean arterial pressure and CO. We observed that during HUT, an expected decrease in TFC was accompanied by an increase of PEP, an increase of SVR and no significant change in DBP. During mental stress, we observed a decrease of PEP and an increase of TFC, SVR and DBP. Correlating a change in assessed measures (delta values) between mental stress and previous supine rest, we found that ΔPEP correlated negatively with ΔCO and positively with ΔSVR. In orthostasis, no significant correlation between ΔPEP and ΔDBP, ΔTFC, ΔCO, ΔMBP or ΔSVR was found. We conclude that despite an expected increase of sympathetic activity during both challenges, PEP behaved differently indicating an effect of other confounding factors. To interpret PEP values properly, we recommend simultaneously to measure other variables influencing this cardiovascular measure.

Physiological acoustic sensing based on accelerometers: a survey for mobile healthcare

This paper reviews the applications of accelerometers on the detection of physiological acoustic signals such as heart sounds, respiratory sounds, and gastrointestinal sounds. These acoustic signals contain a rich reservoir of vital physiological and pathological information. Accelerometer-based systems enable continuous, mobile, low-cost, and unobtrusive monitoring of physiological acoustic signals and thus can play significant roles in the emerging mobile healthcare. In this review, we first briefly explain the operation principle of accelerometers and specifications that are important for mobile healthcare. Applications of accelerometer-based monitoring systems are then presented. Next, we review a variety of accelerometers which have been reported in literatures for physiological acoustic sensing, including both commercial products and research prototypes. Finally, we discuss some challenges and our vision for future development.

Sex-related differences in cardiovascular stress reactivity in healthy and hypertensive rats

In healthy females the chronotropic effects of stress are more pronounced, while the hypertensive effects are weakened compared to males. Hemodynamic parameters in females returned to normal more rapidly than in males. Renovascular hypertension in males is more pronounced than in females and is associated with increased cardiovascular stress reactivity (in females it is associated with decreased cardiovascular stress reactivity), which increase the risk of cardiovascular complications in males.

[Cardiovascular impact of psychological stress]

The cardiovascular impact of stress depends on, first individual perception of stress and second individual cardiovascular reactivity to a stressful stimulation. Psychological stressors are filtered by cognitive appraisal mechanisms before causing biological response so that, for the same strain, individual effects may differ. Therefore, due to complexity of stress personal management, a multilevel stress measurement strategy is needed. To measure stress cardiovascular impact, stress should be precisely quantified. Recently, questionnaires have been developed to score not only the strain but also the personal perception of the strain. Individual stress reactivity can be evaluated by hormone response (epinephrine, norepinephrine, steroids) or by cardiovascular reactivity to a stress test. Until now, all the studies found that stress was independently related to blood pressure especially in active people. Prospective studies are still ongoing to definitively prove that stress could explain hypertension in a subset of hypertensives.

A prospective study of the impact of stress on quality of life: an investigation of low-income individuals with hypertension

The role that major and minor life events play in the quality of life in low-income hypertensives was examined. Participants were randomly recruited from 2 primary care clinics at a public medical center. The study utilized a prospective design. Participants were determined to have hypertension and were being treated with antihypertensive medication prior to and throughout the duration of the study. Participants were administered the Life Experiences Survey and the Weekly Stress Inventory repeatedly during Year 1 to assess major and minor stress, respectively. Participants were repeatedly administered the RAND 36-Item Health Survey during Year 2 to assess quality of life. Usable data were obtained from 183 patients. Analyses revealed that major and minor stress were significant predictors of all measured domains of quality of life, even after age and number of chronic illnesses were statistically controlled. Minor stress contributed uniquely to the prediction of each dimension of quality of life even when age, number of chronic illnesses, and major life events were accounted for. Findings suggest that stress has a significant, persistent impact on the quality of life of low-income patients with established hypertension. These findings extend prior research that has examined the impact of medications on quality of life and suggest that stress needs to be accounted for as well.

Blood pressure reactions to acute psychological stress and future blood pressure status: a 10-year follow-up of men in the Whitehall II study

OBJECTIVE

The aim of this study was to examine whether blood pressure reactions to mental stress predicted future blood pressure and hypertension.

METHODS

Blood pressure was recorded at an initial medical screening examination after which blood pressure reactions to a mental stress task were determined. A follow-up screening assessment of blood pressure and antihypertensive medication status was undertaken 10 years later. Data were available for 796 male public servants, between 35 and 55 years of age upon entry to the study.

RESULTS

Systolic blood pressure reactions to mental stress were positively correlated with follow-up screening systolic blood pressure and to a lesser extent, follow-up diastolic pressure. In multivariate tests, by far the strongest predictors of follow-up blood pressures were initial screening blood pressures. In the case of follow-up systolic blood pressure, systolic reactions to stress emerged as an additional predictor of follow-up systolic blood pressure. With regard to follow-up diastolic blood pressure, reactivity did not enter the analogous equations. The same outcomes emerged when the analyses were adjusted for medication status. When hypertension at 10-year follow-up was the focus, both systolic and diastolic reactions to stress were predictive. However, with correction for age and initial screening blood pressure, these associations were no longer statistically significant.

CONCLUSIONS

The results of this study provide modest support for the hypothesis that heightened blood pressure reactions to mental stress contribute to the development of high blood pressure. At the same time, they question the clinical utility of stress testing as a prognostic device.

Vagal and cardiac reactivity to psychological stressors in trained and untrained men

PURPOSE

The aim of this study was to determine whether higher aerobic fitness is associated with enhanced vagal influences on the myocardium, resulting in moderation of chronotropic cardiac activity during psychological stress and recovery.

METHOD

Heart period (HP) and respiratory sinus arrhythmia (RSA) were obtained from 10 aerobically trained (AT) and 10 untrained (UT) college-aged men at rest and during three contiguous psychological challenges and 3 min of recovery. Ratings of perceived stress were obtained at the end of the rest period, at the midpoint of each stressor, and at 30 s into recovery. Time series methods were used to quantify RSA from the beat-to-beat HP series. Responsivity was assessed both in terms of absolute levels of activity and phasic changes in activity (task or recovery minus baseline).

RESULTS

Both groups reported similar levels of subjective stress throughout the experiment. The AT exhibited longer HP at rest and during psychological stress and recovery than did the UT. However, the groups did not differ on RSA at rest or during psychological stress and recovery, nor did they differ on phasic changes in RSA or HP during stress or recovery. Additionally, aerobic capacity was not correlated with absolute levels or phasic changes in RSA during psychological challenge for either group and, except in Min 2 for the UT, similar results were obtained for recovery.

CONCLUSIONS

The results supported the hypothesis that, among young men, higher aerobic fitness is associated with longer HP at rest and during psychological stress and recovery. However, the lower cardiac chronotropic activation observed among the AT relative to the UT was not paralleled by a group difference in the amplitude of RSA. These results suggest that the group difference in HP was not mediated directly by the vagal mechanisms manifested in the amplitude of RSA.

The effects of blood pressure resting level and lability on cardiovascular reactions to laboratory stress

Evidence that individuals with elevated resting blood pressures display excessive cardiovascular reactions to laboratory stress is regarded as implicating excessive reactivity in the pathogenesis of hypertension. However, it remains possible that this relationship is artifactual, in that resting blood pressure levels and cardiovascular reactions might both reflect intrinsic cardiovascular lability. To examine this possibility, blood pressure and heart rate were measured at rest and in response to an active laboratory stressor in 1259 men. Systolic blood pressure and heart rate reactions to the stressor were predicted by resting blood pressure. Although cardiovascular lability showed some association with both reactivity and resting blood pressure level, the resting blood pressure level-reactivity relationship survived statistical adjustment for such associations. Accordingly, the excessive cardiovascular reactions characteristic of individuals with elevated resting blood pressure would not appear to be explainable, to any substantial extent, by lability effects.

Health and safety problems associated with long working hours: a review of the current position

The European Community Directive on Working Time, which should have been implemented in member states of the European Community by November 1996, contains several requirements related to working hours, including the right of employees to refuse to work more than 48 hours a week. The United Kingdom government attempted to oppose the Directive, arguing that there is no convincing evidence that hours of work should be limited on health and safety grounds. Much of the research in this area has focused on the problems of shiftworking and previous reviews have therefore tended to emphasise this aspect of working hours. However, there is much less information about the effects of overtime work, which is a central element of the terms of the Directive. This paper reviews the current evidence relating to the potential effects on health and performance of extensions to the normal working day. Several gaps in the literature are identified. Research to date has been restricted to a limited range of health outcomes--namely, mental health and cardiovascular disorders. Other potential effects which are normally associated with stress--for example, gastrointestinal disorders, musculoskeletal disorders, and problems associated with depression of the immune system, have received little attention. Also, there have been few systematic investigations of performance effects, and little consideration of the implications for occupational exposure limits of extensions to the working day. Existing data relate largely to situations where working hours exceed 50 a week and there is a lack of information on hours below this level, which is of direct relevance to the European Community proposal. Finally, it is clear from investigations relating to shiftwork that a range of modifying factors are likely to influence the level and nature of health and performance outcomes. These include the attitudes and motivation of the people concerned, the job requirements, and other aspects of the organisational and cultural climate. It is concluded that there is currently sufficient evidence to raise concerns about the risks to health and safety of long working hours. However, much more work is required to define the level and nature of those risks.

Illusions, arithmetic, and the bidirectional modulation of vagal control of the heart

Behavioral contexts can evoke a variety of autonomic modes of response, characterized by reciprocal, coactive, or independent changes in the autonomic divisions. The present study investigated the modes of autonomic response to visual illusion and mental arithmetic tasks, by the use of noninvasive measures of sympathetic (pre-ejection period; PEP) and parasympathetic (respiratory sinus arrhythmia; RSA) cardiac control. As previously demonstrated, mental arithmetic was associated with a reciprocal pattern of sympathetic activation and vagal withdrawal. The illusion task, however, yielded a distinct mode of vagal activation in the absence of sympathetic change. Responses within tasks were reliable. In contrast to the general intertask consistency reported for stress tasks that yield similar autonomic modes of response, however, neither PEP nor RSA responses were correlated across the illusion and arithmetic tasks. This may be attributable to the dissimilar modes of autonomic control evoked by these tasks. The distinct modes of autonomic response to arithmetic and illusions emphasize the importance of a bivariate model of autonomic control, and may offer important experimental tools for psychophysiological studies of autonomic control.

Pressor reactions to psychological stress and prediction of future blood pressure: data from the Whitehall II Study

OBJECTIVE

To examine whether reactions of blood pressure to psychological stress predict future blood pressure.

DESIGN

Blood pressure was recorded at a medical screening examination after which pressor reactions to a psychological stress task were determined. Follow up measurement of blood pressure was undertaken, on average, 4.9 years later.

SETTING

20 civil service departments in London.

SUBJECTS

1003 male civil servants aged between 35 and 55 years at entry to the study.

MAIN OUTCOME MEASURE

Blood pressure at follow up screening.

RESULTS

Reactions of systolic blood pressure to stress correlated positively with systolic blood pressure at follow up screening (r = 0.22, P < 0.01). The dominant correlate of follow up blood pressure was blood pressure at initial screening (r = 0.60; P < 0.01 between initial and follow up systolic blood pressure; r = 0.59, P < 0.01 between initial and follow up diastolic blood pressure). Stepwise multiple regression analysis indicated that reactions to the stressor provided minimal prediction of follow up blood pressure over and above that afforded by blood pressure at initial screening. In the case of follow up systolic blood pressure, systolic reactions to stress accounted for only 1% of follow up variance; systolic blood pressure at initial screening accounted for 34%. With regard to diastolic blood pressure at follow up, the independent contribution from diastolic reactions to stress was less than 1%.

CONCLUSION

Pressor reactions to psychological stress provide minimal independent prediction of blood pressure at follow up. Measurement of reactivity is not a useful clinical index of the course of future blood pressure.

Laboratory reactivity assessment: effects of casual blood pressure status and choice of task difficulty

In a study of 60 healthy young men, 26 with high and 34 with normal casual systolic pressure, blood pressure and its underlying hemodynamic determinants were measured at rest and during exposure to a series of laboratory tasks. Subjects were given a choice of performing either a difficult or an easy version of a mental arithmetic task, and then offered a similar choice of an easy or difficult stimulated public speaking task. All subjects were given the same tasks, regardless of choice, but led to believe the tasks were the ones they had chosen. During all tasks, subjects with high casual systolic pressure showed greater blood pressure, cardiac output, heart rate and myocardial contractility increases than subjects with normal casual pressure. Within the high casual pressure group, subjects who chose difficult for the mental arithmetic task exhibited greater increases in systolic pressure and heart rate during that task than subjects who chose easy. This subgroup maintained their greater responses during a subsequent mental arithmetic task in which all subjects were told that the difficulty level was the reverse of what they had initially chosen. Choosing difficult on the speaking task was associated with greater increases in cardiac output during performance on that task. Differences in cardiovascular responses associated with choice of difficulty were not evident during performance on tasks which did not pertain to the choice. For mental arithmetic, choice of difficulty was also associated with the psychological trait, fear of failure. These findings are relevant to the development of cardiovascular reactivity assessment procedures, which should attempt to detect psychological as well as physiological determinants of individual differences.