Effects of salt, race, and hypertension on reactivity to stressors

Sympathetic neural reactivity to mental stress differs in black and non-Hispanic white adults

Black adults have a higher risk of hypertension compared with non-Hispanic white (NHW) adults, but physiological mechanisms underlying this predisposition remain unclear. This study compared muscle sympathetic nerve activity (MSNA) responses to mental stress in a group of young black and NHW participants. We hypothesized that the sympathoexcitation associated with mental stress would be greater in black adults compared with NHW participants. Thirty-five male adults (19 black, 23 ± 1 yr; 16 NHW, 22 ± 1 yr) were examined during 5-min supine baseline and 5 min of mental stress (via mental arithmetic). Baseline mean arterial pressure (80 ± 2 vs. 82 ± 1 mmHg), heart rate (61 ± 4 vs. 61 ± 2 beats/min), MSNA (13 ± 1 vs. 15 ± 2 bursts/min), and sympathetic baroreflex sensitivity (-1.1 ± 0.4 vs. -1.5 ± 0.3 bursts·100 heart beats^-1·mmHg^-1) were not significantly different between NHW and black adults ( P > 0.05), respectively. MSNA reactivity to mental stress was significantly higher in NHW compared with black adults (time × race, P = 0.006), with a particularly divergent responsiveness during the first minute of mental stress in NHW (Δ4 ± 1 burst/min) and black (Δ-2 ± 2 burst/min; P = 0.022) men. Blood pressure and heart rate reactivity to mental stress were similar between groups. In summary, black participants demonstrated a lower MSNA responsiveness to mental stress compared with NHW adults. These findings suggest that, despite a higher prevalence of hypertension, black subjects do not appear to have higher neural and cardiovascular responsiveness to mental stress compared with NHW. NEW & NOTEWORTHY Black men have a blunted muscle sympathetic nerve activity response to mental stress compared with non-Hispanic white (NHW) men, especially at the onset of mental stress when muscle sympathetic nerve activity decreased in blacks and increased in NHW men. Thus, despite a high prevalence of hypertension in blacks, normotensive NHW men display a greater peripheral sympathetic neural reactivity to mental stress than black men.

Stress physiology in marine mammals: how well do they fit the terrestrial model?

Stressors are commonly accepted as the causal factors, either internal or external, that evoke physiological responses to mediate the impact of the stressor. The majority of research on the physiological stress response, and costs incurred to an animal, has focused on terrestrial species. This review presents current knowledge on the physiology of the stress response in a lesser studied group of mammals, the marine mammals. Marine mammals are an artificial or pseudo grouping from a taxonomical perspective, as this group represents several distinct and diverse orders of mammals. However, they all are fully or semi-aquatic animals and have experienced selective pressures that have shaped their physiology in a manner that differs from terrestrial relatives. What these differences are and how they relate to the stress response is an efflorescent topic of study. The identification of the many facets of the stress response is critical to marine mammal management and conservation efforts. Anthropogenic stressors in marine ecosystems, including ocean noise, pollution, and fisheries interactions, are increasing and the dramatic responses of some marine mammals to these stressors have elevated concerns over the impact of human-related activities on a diverse group of animals that are difficult to monitor. This review covers the physiology of the stress response in marine mammals and places it in context of what is known from research on terrestrial mammals, particularly with respect to mediator activity that diverges from generalized terrestrial models. Challenges in conducting research on stress physiology in marine mammals are discussed and ways to overcome these challenges in the future are suggested.

Dietary sodium influences the effect of mental stress on heart rate variability: a randomized trial in healthy adults

BACKGROUND

Dietary sodium influences intermediate physiological traits in healthy adults independent of changes in blood pressure. The purpose of this study was to test the hypothesis that dietary sodium affects cardiac autonomic modulation during mental stress.

METHOD

In a prospective, randomized cross-over design separated by 1 month between diets, 70 normotensive healthy young adults (F/M: 44/26, aged 18-38 years) consumed a 5-day low (10 mmol/day), normal (150 mmol), and high (400 mmol) sodium diet followed by heart rate variability (HRV) recordings at rest and during 5-min computerized mental arithmetic. Women were studied in the low hormone phase of the menstrual cycle following each diet.

RESULTS

Diet did not affect resting blood pressure, but heart rate (HR) (mean ± SE) was 66 ± 1, 64 ± 1, and 63 ± 1 bpm in low, normal, and high sodium conditions, respectively (analysis of variance P = 0.02). For HRV, there was a main effect of sodium on resting SD of normalized RR intervals (SDNN), square root of the mean squared difference of successive normalized RR intervals (RMSSD), high frequency, low-frequency normalized units (LFnu), and high-frequency normalized units (HFnu) (P < 0.01 for all). The response to low sodium was most marked and consistent with sympathetic activation and reduced vagal activity, with increased LFnu and decreased SDNN, RMSSD, and HFnu compared to both normal and high sodium conditions (P ≤0.05 for all). Dietary sodium-by-mental stress interactions were significant for mean NN, RMSSD, high-frequency power, LFnu, and low frequency/high frequency ratio (P < 0.05 for all). The interactions signify that sodium restriction evoked an increase in resting sympathetic activity and reduced vagal activity to the extent that mental stress caused modest additional disruptions in autonomic balance. Conversely, normal and high sodium evoked a reduction in resting sympathetic activity and incremental increase in resting vagal activity, which were disrupted to a greater extent during mental stress compared to low sodium.

CONCLUSION

We conclude that autonomic control of HRV at rest and during mental stress is altered by dietary sodium in healthy normotensive young adult men and women.

Hindi translation and validation of dysfunctional beliefs and attitudes about sleep (DBAS - 16)

OBJECTIVES

The objective of this study is to translate and validate the Dysfunctional Beliefs and Attitudes about Sleep Brief Version (DBAS-16)) in Hindi language.

MATERIALS AND METHODS

The scale was obtained online, and the permission for translation was obtained from the author. The translation of the scale was carried out following back translation method. The scale was applied on 63 participants attending the adult psychiatry OPD who were included in the study.

RESULTS

Thirty-two patients were having insomnia, and 31 patients were controls without insomnia. The results show that the translated version had good reliability with internal consistency (Chronbach alpha = 0.901).

CONCLUSION

The Hindi translation of DBAS-16 is a reliable tool for assessing the dysfunctional beliefs and attitude about sleep.

Association between dietary behaviors and attention-deficit/hyperactivity disorder and learning disabilities in school-aged children

We aimed to comprehensively investigate the associations between a wide range of measures of dietary behaviors and learning disabilities and attention-deficit/hyperactivity disorder (ADHD) in community-dwelling Korean children in order to generate hypotheses for future work. The present study included 986 children [507 boys, 479 girls; mean (S.D.) age=9.1 (0.7) years] recruited from five South Korean cities. Children's dietary behaviors were assessed by the mini-dietary assessment (MDA) for Koreans. It consists of ten items to assess the level of intake of dairy products, high-protein foods, vegetables, fried foods, fatty meats, salt, and sweetened desserts and whether the subject is eating three regular meals and has a balanced diet. Learning disability was assessed via the Learning Disability Evaluation Scale (LDES). ADHD was assessed via the Diagnostic Interview Schedule for Children version-IV and the ADHD rating scale, and ADHD-related behavioral problems were assessed via the Child Behavior Checklist. After adjusting for potential confounders, a high intake of sweetened desserts, fried food, and salt is associated with more learning, attention, and behavioral problems, whereas a balanced diet, regular meals, and a high intake of dairy products and vegetables is associated with less learning, attention, and behavioral problems. Our data suggest that existing encouraged dietary habits mostly have beneficial effects on learning, attention, and behavioral problems in Korean children. These findings are in general the same results in other studies on ADHD children in other countries. However, the cross-sectional study design prevents our ability to assess causal relationships.

State anxiety is associated with cardiovascular reactivity in young, healthy african americans

Although several studies have shown that enhanced cardiovascular reactivity can predict hypertension development in African Americans, these findings have not been consistent among all studies examining reactivity and hypertension susceptibility. This inconsistency may be explained by the influence of anxiety (state and trait) on the blood pressure response to stress. Therefore, this study sought to determine whether anxiety is associated with blood pressure response to cold pressor (CP) and anger recall (AR) stress tests in young healthy African Americans. Modeling using state and trait anxiety revealed that state anxiety predicts systolic (SBP) and diastolic blood pressure DBP response to CP and AR (P ≤ 0.02). Interestingly, state anxiety predicted heart rate changes only to CP (P < 0.01; P = 0.3 for AR). Although trait anxiety was associated with SBP response to AR and not CP, it was not a significant predictor of reactivity in our models. We conclude that anxiety levels may contribute to the variable blood pressure response to acute stressors and, therefore, should be assessed when performing cardiovascular reactivity measures.

Ethnic differences in cardiovascular-somatosensory interactions and in the central processing of noxious stimuli

Ethnic differences in central sensitization of pain processing and stress-relevant endogenous pain regulatory mechanisms were examined. Forty-four African Americans (AAs; 50% women) and 44 non-Hispanic Whites (nHWs; 50% women) matched for socioeconomic status, were tested for pain responses to the temporal summation of heat pulses and ischemic and cold pain. Resting and stress blood pressure (BP) and norepinephrine (NE) were assessed. AAs had heightened pain responses to all 3 pain tasks relative to nHWs. In nHWs, higher BP and NE were related to reduced pain. In AAs, there was no relationship between BP and pain, but higher NE was related to increased pain. This study provides evidence for ethnic differences in centrally mediated pain and extends prior research demonstrating ethnic differences in endogenous pain regulatory mechanisms. These results have implications for understanding biobehavioral factors contributing to ethnic disparities in clinical pain.

Sleep health in U.S. Hispanic population

The importance of sleep on health has only been recently recognized, and the general public and the medical community are not yet fully knowledgeable about this issue. The great majority of sleep research has been performed in whites of European descent and to a lesser extent in African Americans, making generalization of the findings to other ethnic and racial groups difficult. Very little sleep research has been done in U.S. Hispanics. However, based on the available literature and the high prevalence of risk factors in Hispanics, such as obesity, diabetes, living in the inner city, and use of alcohol, the prevalence of such important sleep disorders such as obstructive sleep apnea and sleep habits such as poor sleep hygiene are suspected to be high. There is also some evidence that acculturation to the U.S. life style may lead to worse sleep habits in Hispanics, including fewer hours of sleep. Two current large NIH sponsored studies of sleep in U.S. Hispanics promise to significantly add to the literature on various sleep disorders such as sleep disordered breathing, insomnia, restless legs syndrome, periodic limb movement disorder, and sleep habits such as short sleep duration and sleep hygiene.

Major depressive disorder is associated with attenuated cardiovascular reactivity and impaired recovery among those free of cardiovascular disease

OBJECTIVE

To examine cardiovascular reactivity and recovery to laboratory stress among a naturalistic sample of individuals diagnosed with major depressive disorder (MDD) and healthy control participants. Prospective evidence suggests that MDD confers risk for cardiovascular disease equal to or greater than the risk associated with depressed mood. Enhanced cardiovascular reactivity has been proposed as a mechanism explaining increased risk, but data are inconsistent as to whether depressed individuals exhibit enhanced or attenuated reactivity. Further, few studies have examined appraisal and recovery differences.

DESIGN

Participants diagnosed with MDD (N = 25) and healthy control participants (N = 25) engaged in a cardiovascular reactivity protocol including 2 tasks, each followed by a brief recovery period.

MAIN OUTCOME MEASURES

Blood pressure, heart rate, pre-ejection period, cardiac output and total peripheral resistance were assessed. Appraisals of tasks were assessed prior to each task.

RESULTS

Depressed participants exhibited significantly less systolic blood pressure, heart rate, and cardiac output reactivity during speech, less heart rate reactivity during mirror tracing, and less heart rate recovery after speech and mirror tracing than controls. Depressed participants appraised the tasks as more demanding, threatening, and stressful and reported being less able to cope than controls. Appraisals were related to heart rate reactivity, but appraisals did not mediate the relationship between depression group and reactivity.

CONCLUSION

Impaired recovery rather than exaggerated cardiovascular reactivity may partially explain the increased prospective cardiovascular disease risk in depressed individuals.

Cardiovascular reactivity to psychological stressors in late adulthood is predicted by gestational age at birth

The relationships of body size and gestational age at birth with adult blood pressure (BP) are relatively modest compared to their stronger associations with cardiovascular disease. BP reactivity is a strong predictor of cardiovascular morbidity, and it is possible that reactivity, rather than resting level, is determined in utero. We investigated whether body size and gestational age at birth predict BP reactivity during experimentally induced psychosocial stress in late adulthood. A total of 73 men and 80 women born after 36 weeks' gestation in Helsinki, Finland, during 1934-1944 underwent the Trier Social Stress Test (TSST); a standardized psychosocial stress test consisting of a public speech and an arithmetic task. Changes in BP were monitored continuously by a non-invasive finger photoplethysmography (Finometer, FMS, Amsterdam, The Netherlands). The results showed that the most robust early determinant of BP reactivity was gestational age; however, with opposite relationships between the sexes (P for interaction <0.001). A 1-week increase in gestational age was associated with a 3.1 mm Hg (95% confidence interval (CI), 0.2 to 6.0) and 1.2 mm Hg (95% CI, -0.1 to 2.6) decreases in systolic and diastolic BP reactivity in women, but with 5.2 mm Hg (95% CI, 1.9 to 8.4) and 2.3 mm Hg (95% CI, 0.9 to 3.8) increases in men. In conclusion, normal variation in gestational age at birth predicts cardiovascular stress reactivity in later adulthood. Given that hypothalamic-pituitary-adrenal axis contributes to the regulation of autonomic nervous system function and the timing of parturition, and shows well-established sex differences, we speculate a role for early programming of this axis in explaining the findings.

Age and ethnicity differences in short-term heart-rate variability

OBJECTIVE

Hypertension is more frequent and more severe in older individuals and in African Americans. Differences in autonomic nervous system activity might contribute to these differences. Autonomic effects on the heart can be studied noninvasively through analysis of heart rate variability (HRV). We examined the effects of age and ethnicity on HRV.

METHODS

We studied 135 subjects (57 African Americans and 78 Caucasian Americans), aged 23 to 54 years. Using their surface electrocardiogram (ECG) data, we calculated the HRV indices with spectral analyses. High frequency (HF) power was used to index parasympathetic activity, whereas the ratio of low to high frequency power (LF/HF) was used to index sympathovagal balance.

RESULTS

Three HRV indices (HF, LF power, and LF/HF) were significantly related to age in Caucasian Americans but not in African Americans. The effect of age, ethnicity, and the age-by-ethnicity interaction on HF and LF power was significant, even after controlling for gender, body mass index, and blood pressure.

CONCLUSIONS

Young African Americans manifested a pattern of HRV response similarly to older Caucasian Americans. These results suggest that young African American individuals might show signs of premature aging in their autonomic nervous system.

Psychophysiological reactivity: mechanisms and pathways to cardiovascular disease

OBJECTIVE

This article examines possible sources of heightened psychophysiological reactivity in relation to risk for hypertension and coronary artery disease. The idea that exaggerated reactions to psychological stress may predict greater risk for future disease has some support in the psychosomatic and behavioral medicine literature. However, the pathways by which exaggerated reactivity could arise in a given person and the implications of different sources of reactivity for potential disease relationships have received little attention.

METHODS

This topic is approached through a selective literature review and by means of a neurophysiologically based model of individual differences in physiological reactivity. Temperament characteristics, cognitive processes, neurophysiology, and peripheral physiology are used to indicate three levels that could contribute to exaggerated physiological reactivity.

RESULTS

At the top level in the model, activity of the frontal cortex and limbic system establish cognitive-emotional sources of activation that may underlie exaggerated physiological reactivity. In the absence of these influences, large responses may be more likely when exaggerated subcortical response tendencies are present via the hypothalamus or brain stem. Finally, peripheral alterations may account for larger reactions in persons who have otherwise normal emotional and hypothalamic and brainstem response tendencies. Cognitive-emotional and hypothalamic-brainstem sources of altered reactivity may cause or aggravate disease. In contrast, altered peripheral reactivity suggests that a pathophysiologic process may be present, serving as a marker for disease.

CONCLUSIONS

These three levels of analysis allow for organization of existing data in the area of cardiovascular reactivity and for planning future studies in a hypothesis-building framework.

Mood states and impedance cardiography-derived hemodynamics

OBJECTIVE

This exploratory study investigated the relation between psychological mood states and hemodynamic variables obtained at rest.

METHODS

We measured resting hemodynamic variables using impedance cardiography, blood pressure, heart rate, and the Profile of Mood States (POMS) in 71 participants.

RESULTS

Mood states were not significantly associated with heart rate, systolic, diastolic, or mean arterial pressure. In comparison with these basic measures of physiology, a number of impedance derived measures of hemodynamics were associated with mood states. Log stroke volume was negatively correlated with POMS tension-anxiety (r = -.319, p = .009) and fatigue-inertia (r = -. 316, p = .009). Log cardiac output was negatively associated with fatigue-inertia (r = -.346, p < .01). Log total peripheral vascular resistance was positively correlated with POMS fatigue-inertia (r = .276, p = .024).

CONCLUSIONS

Our findings suggest that mood states are associated with hemodynamic variables underlying blood pressure.

Hypertension in black people: study of specific genotypes and phenotypes will provide a greater understanding of interindividual and interethnic variability in blood pressure regulation than studies based on race

Hypertension is more frequent and more severe in some Black populations. Although many studies have focused on hypertension in black people in an attempt to understand the genetic and environmental factors that regulate blood pressure, this approach has not been productive. Study of the relationship between specific phenotypes and genotypes, both within and across ethnic groups, is more likely to advance our understanding of the regulation of blood pressure than studies focused on race and blood pressure.

Increased vascular adrenergic vasoconstriction and decreased vasodilation in blacks. Additive mechanisms leading to enhanced vascular reactivity

Blood pressure reactivity is enhanced in young black subjects through mechanisms that are poorly understood. We compared alpha-adrenergic-mediated vasoconstrictor and ss-adrenergic vasodilator sensitivity and their relation to sympathetic activity in blacks and whites. Ten healthy black (age, 29.9+/-2.4 years) and 10 white (age, 28.3+/-1.9 years) men were studied. Forearm blood flow was measured with strain-gauge plethysmography after the intrabrachial artery administration of phenylephrine (1.25 to 20 microgram/min) and isoproterenol (60 and 400 ng/min) after application of lower-body negative pressure and after a cold pressor test. Forearm and systemic norepinephrine spillover were measured with a radioisotope dilution technique. alpha-Adrenergic vasoconstriction was markedly increased (ANOVA P=0.008) and ss-adrenergic vasodilation decreased (ANOVA P=0.02) in blacks. Phenylephrine (10 microgram/min) decreased forearm blood flow by 58.0+/-2.5% in blacks but only by 26.6+/-6.0% in whites (P<0.001). Vasoconstrictor response to endogenous norepinephrine, stimulated by a cold pressor test, resulted in a higher forearm vascular resistance in blacks than in whites (107.3+/-13 versus 64.8+/-13 mm Hg. mL(-)(1). 100 mL(-)(1), P=0.03). There were no significant ethnic differences in basal or stimulated forearm or systemic norepinephrine spillover. Increased vasoconstrictor and decreased vasodilator responses in blacks were not correlated. Increased sympathetically mediated vascular tone caused by enhanced vasoconstriction and attenuated vasodilation, effects that would be additive, and not increased sympathetic activity could enhance vascular reactivity and may play a role in the pathogenesis of hypertension in blacks.

Stalked by the past: the influence of ethnicity on health

Ethnicity impacts the course of illness and medical treatment. There are enormous ethnic differences in care delivered to patients who are treated for pain. However, in addition to these social forces, there are enormous ethnic differences in physiological response to stimuli as diverse as diet, exposure to agonist infusions, or habitual patterns of response to stressors. The author's clinical research studies on this topic for the last 20 years are reviewed in this article.

Influence of ethnicity and gender on cardiovascular responses to active coping and inhibitory-passive coping challenges

OBJECTIVE

The goal of this study was to evaluate how black and white men and women responded physiologically to specific laboratory challenges.

METHODS

Hemodynamic responses to an active coping (evaluated speaking) and two inhibitory-passive coping (mirror tracing, cold pressor) tasks were examined in 138 black and white men and women.

RESULTS

Significant ethnicity by gender interactions occurred for the evaluated speaking task. Black men responded with lower blood pressure, cardiac output or heart rate, or both, than black women, white men, and white women, who did not differ from each other. Black men, relative to the other subgroups, also reported more inhibitory-passive coping, hostility, and pessimism, and less social support. Whites also responded with greater increases in systolic blood pressure during mirror tracing than blacks.

CONCLUSIONS

These findings indicate that black-white differences in physiological responsivity obtained for men may have limited generalizability for women. The results also suggest that environmental and social factors rather than genetic or constitutional factors may play a role in black-white reactivity differences.

Race and sex differences in cardiovascular recovery from acute stress

To evaluate the effects of race and gender on recovery, i.e. the relative return to baseline after a stress challenge, cardiovascular and catecholamine measures were examined before, during and after two standardized laboratory stressors (a speaking and a mirror tracing task) in a group of 85 Black and White men and women (mean age 35.6 years, range 20 to 52). For the speech task, White men showed the least systolic (p < 0.025) and diastolic (p < 0.05) blood pressure recovery as compared to Black men and women. For the mirror star tracing task, total peripheral resistance (p < 0.03) recovery was least for Whites as compared to Blacks and heart rate (p < 0.04) recovery was least for White women as compared to Black women and men. There were no significant group effects in terms of catecholamine recovery from either task. The findings extend prior studies on race and gender by suggesting that these same characteristics affect recovery from stressors.

Comparison of cardiac versus vascular reactors and ethnic groups in plasma epinephrine and norepinephrine responses to stress

This study examined differences in plasma epinephrine (EPI) and norepinephrine (NOREPI) responses to stressors in 67 healthy African-American and Caucasian American men and women of the ages 18 to 49. Subjects were divided into three groups: (a) those who showed high blood pressure (BPI responses to stress associated with consistently high cardiac output (CO) increases with no substantial increases in total peripheral resistance (TPR), labeled cardiac reactors: (b) those with equally high BP increases associated with consistently higher TPR increases and lesser CO increases. labeled vascular reactors; (c) those who showed mixed hemodynamic responses or were low BP reactors. Ethnic and gender group differences in EPI and NOREPI responses were also examined. Cardiac reactors, vascular reactors and mixed + low reactors did not differ in EPI or NOREPI levels at baseline. During stressors, cardiac reactors showed greater increases in plasma EPI than vascular reactors or others during math, reaction time, and passive and active speech tasks: they also showed a weak trend toward greater NOREPI increases during these challenges as well. No differences were seen during the cold pressor: this stressor evoked the least change in EPI of all tasks, whereas the active speech elicited the greatest increases in both EPI and NOREPI of all tasks. Vascular reactors did not differ from mixed + low reactors in EPI or NOREPI reactivity, and men and women did not differ in EPI or NOREPI reactivity to any task. In contrast, Black subjects showed greater increases in NOREPI levels across all stressors compared to White subjects. These findings have implications for investigations of the role of sympathetic nervous system activity in the pathogenesis of hypertension in both African-American and Caucasian American populations.

Temporal stability of task-induced cardiovascular, adrenergic, and psychological responses: the effects of race and hypertension

This study examined the test-retest reliability of task-induced responses of blood pressure, heart rate, norepinephrine, epinephrine, anger, and anxiety in 98 black and white normotensive and hypertensive individuals. Subjects completed three laboratory tasks (standing, mental arithmetic, and cold pressor) on two occasions 10 days apart. For all subjects, all baseline and test-retest correlation coefficients were significant (rs = .23-.71; median = .58). Baseline-adjusted (residual scores) reactivity test-retest correlation coefficients were consistently smaller (rs = .02-.55; median = .36). In contrast to the white hypertensives, white normotensives, and black normotensives, the black hypertensives showed no significant baseline-adjusted test-retest correlation coefficients (rs = -.21-.40; median = .12). Epinephrine responses revealed a significant session by race interaction; blacks had 20% higher mean values and whites had 10% lower mean values upon retesting. The data suggest that race and hypertension may interact to affect the temporal stability of task-induced responses to stressors.