Chronic effects of high salt intake and conflict stress on blood pressure in primates. A progress report.

The effects of combined behavioral stress and high dietary salt on blood pressure were examined in baboons (N = 4) over the course of 1 year. Either high salt diet (240 mEq Na+/day) or conflict stress were administered for 8 to 16 weeks, followed by high salt intake and stress combined. Mean arterial pressure (MAP) increased by 8 mmHg during high dietary salt alone, by 4 mmHg during stress alone, and increased further to 14 mmHg above baseline during combined salt and stress. Control baboons (N = 2) had no change in MAP across 47 weeks. The data indicate additive effects of chronic high dietary salt intake and behavioral stress on blood pressure in non-human primates.     

Chronic effects of high salt intake and conflict stress on blood pressure in primates

The effects of combined behavioral stress and high dietary salt on blood pressure were examined in baboons (N=4) over the course of 1 year. Either high salt diet (240 mEq Na⁺/day) or conflict stress were administered for 8 to 16 weeks, followed by high salt intake and stress combined. Mean arterial pressure (MAP) increased by 8 mmHg during high dietary salt alone, by 4 mmHg during stress alone, and increased further to 14 mmHg above baseline during combined salt and stress. Control baboons (N=2) had no change in MAP across 47 weeks. The data indicate additive effects of chronic high dietary salt intake and behavioral stress on blood pressure in non-human primates.     

Hypertension risk and caffeine's effect on cardiovascular activity during mental stress in young men

Examined the cardiovascular effects of caffeine plus behavioral stress in men low versus high in risk of essential hypertension. Caffeine (3.3 mg/kg, equivalent to 2 to 3 cups of coffee) or placebo was given on alternate days to 19 low-risk men (negative for parental hypertension and low-normal resting blood pressure, BP) and 20 high-risk men (positive history, high-normal BP). Forty minutes later, each worked for 15 min on a demanding psychomotor task during which BP, cardiac output, and vascular resistance were determined. During rest, caffeine raised vascular resistance in both groups. During the task, it supra-additively increased the systolic BP response by enhancing the rise in cardiac output, producing equivalent BP rises in both groups. Due to the higher resting pressures of the high-risk men, caffeine plus the task resulted in 50% of these having transient BP of 140/90 mg Hg or greater. Caffeine in combination with mental stress may produce undesirable BP in those at risk for hypertension.     

Biobehavioral effects of extended salt loading and conflict stress in intact baboons.

Behavioral stressors may inhibit sodium excretion, potentially increasing plasma volume and elevating blood pressure during chronic exposure. Blood pressure regulation may be especially deranged during manipulations that further challenge the kidney, such as a diet high in salt content. The effects on blood pressure and other variables of combined behavioral stress (food/shock conflict) and dietary salt (12 g NaCl per day; 218 mEq Na+ per day) were examined in adult male baboons over the course of 1 year. Mean arterial pressure was not significantly elevated over baseline after 5 months of high dietary salt alone (6 +/- 5 mmHg) but was maximally elevated by an average of 17 (+/- 3 SEM) mmHg after 5 months of combined salt and conflict stress. Control baboons showed no significant trends in mean arterial pressure across the same time period. Individual subjects whose blood pressure was "salt+stress resistant" or "salt+stress sensitive" were differentiated by their degree of pressure diuresis and natriuresis, urinary free cortisol, and a behavioral index of stress sensitivity. The data indicate additive effects of chronic high dietary salt intake and behavioral stressors on blood pressure in nonhuman primates that are dependent on renal function and pituitary-adrenocortical activity.     

Hemodynamic responses to active and passive coping tasks and the prediction of future blood pressure in Thai participants: A preliminary prospective cohort study

Cardiovascular responses to mental stress tests have been related to future blood pressure (BP) levels. However, most studies have been completed in North America and Europe; only one study has been conducted in Asia. Therefore, the study explored whether cardiovascular responses to mental stress predict future resting BP in Thailand. Hemodynamic measures were obtained from 101 healthy adults before, during and after mental arithmetic, a speech task, and a cold pressor task. A follow‐up assessment of resting BP was undertaken 1 year later. Results showed that Thais responded to standardized mental stress tasks with large and significant cardiovascular reactivity. Regression analyses indicated that, after adjustment for baseline BP and traditional risk factors, heightened systolic blood pressure (SBP) responses to mental arithmetic were associated with increased future SBP (ΔR² = .045). These findings suggest that BP reactivity predicts future BP and may play a role in the development of hypertension. In addition, Thais displayed large cardiovascular responses to standardized mental stress tasks, of a similar magnitude to previous studies of North Americans and Europeans.     

Constructive anger verbal behavior predicts blood pressure in a population-based sample.

The creation of an observational Constructive Anger Behavior-Verbal Style Scale (CAB-V) and its relation to resting blood pressure (BP) in an age- and sex-stratified, population-based sample is examined. Participants (N = 1,862) provided hypertension risk factor information, had resting BP assessed multiple times, and completed a videotaped interview, which was later coded for CAB-V and Hostile Style. High CAB-V scores remained a significant predictor of lower resting BP when controlling for the effects of standard hypertension risk factors (age, sex, body mass index, physical activity, alcohol use, smoking status, parental myocardial infarction history, education, and diabetic status) and psychosocial measures (anxiety, depression, hostility, social support, and Hostile Style). This relation also remained when excluding known hypertensive persons. Results suggest that constructive anger expression may have an independent beneficial association with resting BP.     

The moderating role of proactive coping on the relationship between distress tolerance and elevated blood pressure

This study investigated the moderating role of proactive coping on the relationship between distress tolerance and elevated blood pressure (BP) among Nigerian adults with heart disease. Two hundred and forty hypertensive patients were recruited from the cardiology unit of a university teaching hospital (females = 56.2%%; mean age = 41.09 years, SD = 9.11 years). The participants responded to two self-reported measure including the Proactive Coping Inventory (PCI) and the Distress Tolerance Scale (DTS). Following moderated regression analysis, the results showed that proactive coping moderated the relationship between distress tolerance and elevated BP. The slope of the moderation analysis indicated that the relationship between distress tolerance and mean artery pressure was significantly higher for individuals with low proactive coping, as compared to individuals with higher proactive coping. Unlike reactive ways of coping, which addressed already existing stress, interventions aimed at increasing peoples’ proactive coping could be more efficacious in the management of people with high BP.     

Effects of social defeat on acute cardiovascular response in salt-sensitive and salt-resistant rats

We studied the effects of social stress (SS) and a high salt diet on systolic blood pressure (SBP) and heart rate (HR): S/JR male rats (which exhibit marked elevations in SBP when placed on a high sodium diet) and R/JR male rats (which are resistant to the BP-elevating effects of a high sodium diet) were maintained on a low sodium diet (0.3% NaCl) or placed on a high sodium diet (8% NaCl). Within each dietary condition independent groups were either exposed to SS, by placement in the cage of a trained fighter male (Long-Evans breed) for 25 min, or exposed to no stress. The dietary regimen was imposed for 10 days with stress exposures on Days 1, 2, 3, 5, 7, and 9, with SBP and HR measured indirectly by tail plethysmography 3 min following exposure to SS. SS produced an acute decrease in SBP (20-30 mm Hg) in S/JR rats on the second and subsequent exposures, but did not affect HR. SS did not affect SBP of R/JR rats, but did produce a significant elevation of HR. Maintenance on the high sodium diet increased SBP in S/JR, but not R/JR, rats when it was measured on the eighth (no stress) day, but SS obscured the effects of diet on SBP on days when rats were stressed. Following exposure to attacks, defeated SS rats displayed an upright submissive posture relatively late during the first stress exposure when no change in SBP was observed after SS in S/JRs, but displayed the submissive posture immediately and with long duration on the second and subsequent exposures when a marked decrement in SBP was seen.     

Effects of a high salt diet on blood pressure responses to acoustic stimuli in borderline hypertensive rats (BHR)

The borderline hypertensive rat (BHR) responds to environmental and dietary stressors with elevated blood pressure. The first two months of a high salt diet appear to be the time of greatest sensitivity to salt effects on the blood pressure of BHR. The current study was conducted to examine whether exposure to salt diets varying in duration for up to two months differentially affects baseline blood pressures (systolic, SBP, and diastolic, DBP) and blood pressure responses to novel acoustic stimuli in BHR and normotensive Wistar-Kyoto (WKY) rats. Male BHR and WKY were fed a control (1%) salt diet or a high (8%) salt diet for 1, 1.5, 2.5, or 8.5 weeks. SBP and DBP responses to an acoustic stimulus (85 dB, 3 kHz) were measured upon completion of the diets at 12 weeks of age. Ten acoustic trials (one stimulus/minute) were presented and blood pressure responses were recorded in 2-second blocks spanning the 10 seconds prior to and following stimulus presentation. BHR had higher resting SBP and DBP than WKY, and 8.5 weeks of 8 percent salt increased SBP markedly in BHR. SBP and DBP labilities in the initial trial were greater in BHR than WKY with high salt diet durations of 2.5 and 8.5 weeks producing greater lability in later trials. Few differences were noted in pressor responses, but BHR had more dramatic depressor responses than WKY in early trials, and BHR pressures had a more dramatic return to baseline. It appears that genetic history and salt diet can affect blood pressure lability and recovery in response to novel stimuli in genetically susceptible animals.     

A prospective study of psychophysiological arousal, acute stress disorder, and posttraumatic stress disorder

This study investigated the role of acute arousal in the development of posttraumatic stress disorder (PTSD). Hospitalized motor-vehicle-accident survivors (n = 146) were assessed for acute stress disorder (ASD) within 1 month of the trauma and were reassessed (n = 113) for PTSD 6 months posttrauma. Heart rate (HR) and blood pressure (BP) were assessed on the day of hospital discharge. Participants with subclinical ASD had higher HR than those with ASD and no ASD. Participants who developed PTSD had higher HR in the acute posttrauma phase than those without PTSD. Diagnosis of ASD and resting HR accounted for 36% of the variance of the number of PTSD symptoms. A formula composed of a diagnosis of ASD or a resting HR of > 90 beats per minute possessed strong sensitivity (88%) and specificity (85%) in predicting PTSD. These findings are discussed in terms of acute arousal and longer term adaptation to trauma.     

High calcium intake does not prevent stress-salt hypertension in dogs

Avoidance conditioning sessions and isotonic saline (1.3 L/day) were administered to dogs for 12 days under conditions of a low (0.1%) or high (1.5%) calcium diet. Twenty-four-hour mean arterial pressure increased comparably during the stress-salt conditioning periods on both the low (systolic: +16 ± 5 mm Hg; diastolic: +6 ± 2 mm Hg) and high (systolic: +17 ± 4 mm Hg; diastolic: +11 ± 4 mm Hg) calcium diets. Urine volume, sodium excretion, and serum calcium levels on the high calcium diet were not significantly different from those on the low calcium diet. In a second experiment, calcium was infused continuously for six days into the arterial circulation of normotensive or stress-salt hypertensive dogs at a rate of 0.12–0.23 mEq/min. Although serum calcium levels increased by up to 50% under these conditions, there were no significant effects on 24-hour levels of arterial pressure. In contrast to the protective effect of augmented potassium intake, these findings indicate that calcium intake does not influence the development of stress-salt hypertension in dogs.     

Hemodynamic characteristics of young men at risk for hypertension at rest and during laboratory stressors.

Examined hemodynamic activity--at rest, during mental arithmetic, and during hand cold pressor--in young men varying in risk for hypertension. Classification into low-risk (n = 72), moderate-risk (n = 20), and high-risk (n = 13) groups was based on resting systolic blood pressure (SBP) and parental history of essential hypertension (PH). Dependent variables were SBP, diastolic BP (DBP), heart rate, and rate-pressure product (RPP). Progressively greater hemodynamic activity was seen across risk groups at rest and during the tasks. Risk groups differed significantly in SBP, DBP, and RPP at baseline (ps less than .003) and in size of response to mental arithmetic (ps less than .05) but not to cold pressor. These relationships were either absent or weaker when using either risk factor alone to form risk groups. These findings suggest that hemodynamic reactivity to mental stress is predicted better by a combination of resting SBP and PH than by either risk factor alone and that physiological reactivity may be an important accompaniment of increased risk for hypertension.     

Blood pressure hyperreactivity in non-human primates during dietary sodium combined with behavioral stress

The potential for behavioral stress alone or combined with dietary salt to augment pressor reactivity to the onset of daily experimental sessions was examined in normotensive, intact baboons over the course of four months. During twice daily experimental sessions, adult male baboons experienced food/shock conflict such that lever pulling not only served to earn food, but was also occasionally punished with cued mild electric shock. Blood pressure and heart rate were measured during a baseline period of fixed-ratio food reinforcement (3 weeks), during conflict stress (2 weeks), and after dietary salt was added to the daily conflict protocol (CONFLICT + SODIUM, 3 weeks). Reactivity, i.e., acute changes in blood pressure and heart rate to the daily experimental sessions, was not evident during food reinforcement sessions nor during the CONFLICT stress alone condition. The addition of a high salt diet virtually doubled blood pressure increases and heart rate decreases to the onset of experimental sessions. Average reactivities during CONFLICT + SODIUM periods were 11.2/7.9% delta for SBP/DBP (systolic/diastolic blood pressure, mmHg), and -5.65% delta for HR (heart rate, BPM). Neither atenolol nor hydrochlorothiazide diuretic significantly altered cardiovascular reactivity during CONFLICT + SODIUM in comparison to a preceding non-drug CONFLICT + SODIUM period. When atenolol and diuretic effects were directly compared, atenolol mildly augmented, while diuretic mildly decreased DBP but not SBP reactivity during CONFLICT + SODIUM. Reactivity was eliminated after salt loading and behavioral sessions were terminated. These findings provide evidence that enhanced salt ingestion may synergistically act with behavioral stress to produce pressor hyperresponsiveness to otherwise benign environmental events.     

Ambulatory blood pressure and heart rate in healthy male paramedics during a workday and a nonworkday.

Compared ambulatory blood pressure (BP) and heart rate (HR) in 30 paramedics during a 24-hr workday and a 24-hr nonworkday. During the 24-hr period as a whole, there were no BP differences between the workday and the nonworkday, but HR was higher during the nonworkday than during the workday. Systolic BP (SBP) recorded in the ambulance on the workday was elevated 9.8 mm Hg, compared to SBP recorded in a car on the nonworkday; it was also 7.2 mm Hg higher at the scene of an accident and at the hospital than during nonworkday activities. Ratings of moods in diaries indicated that paramedics felt more unhappiness, stress, and sadness and less feelings of pleasantness at work than at home. Rather than being elevated for the entire 24-hr period, work BP seemed to reflect the relatively high stress associated with specific situations in the work of a paramedic.     

An exploration of the benefits of animal‐assisted activities in undergraduate students in Singapore

The rise in psychological problems, attrition, and suicide rates of university students has been linked to the stressful challenges faced during university life. To buffer this, animal assisted activities (AAA) may assist in improving psychological and physiological well‐being in students, however, to date, there is little empirical evidence for their effectiveness. Consequently, this study explored the psychological and physiological benefits of AAA in a sample of undergraduate students. Sixty‐two students from two local universities participated in an hour‐long AAA session delivered by Therapy Dogs Singapore. Measures of perceived stress, anxiety, state self‐esteem, and blood pressure (BP) were taken before and after the sessions. The results indicated that students experienced significant decreases in state anxiety, systolic, and diastolic BP post AAA, and when compared to a quiet reading comparison session. State self‐esteem increased post AAA and, further, was found to moderate the change in anxiety in addition to perceived stress, whereby perceived anxiety reduced more in those with low state self‐esteem and high perceived stress. These results suggest that AAA can be an effective intervention for stress among undergraduate students, which utilizes a novel, easy to implement and enjoyable approach for Singaporean students.     

The effects of stressors and coping resources on anxiety and peripheral narrowing

Abstract

The purpose of the study was to examine possible mechanisms which might help explain why individuals with high life stress and/or low coping resources are at greater risk for incurring athletic injuries. The effects of life events, daily hassles (DH), and coping resources (CR) on state anxiety and peripheral vision narrowing during a stress condition were examined. Subjects were 74 recreational athletes who completed the Life Events Survey, Daily Hassles Scale (DHS), Vulnerability to Stress Questionnaire (CR), and state portion of the State-Trait Anxiety Inventory. Peripheral vision was measured alone during baseline and while simultaneously performing a Stroop Color-Word Test accompanied by distracting noise during the stress condition. State anxiety was assessed during baseline and the stress condition. Analyses of covariance revealed that high negative life events (NLE) (p = .01) were related to greater peripheral narrowing during the stress condition. High TLE (p = .01) and DH (p = .005) were related to elevated state anxiety during the stress condition. The peripheral vision TLE main effect (p = .03) and the state anxiety interactions of NLE × CR and DHS × CR (ps = .05) approached significance. High CR tended to reduce perceived state anxiety during the stress condition for high NLE and DH subjects compared to similar subjects with low CR. Thus, partial support was offered for the mechanisms proposed in the Andersen and Williams (1988) stress-injury model. The results are discussed in terms of future research needs.     

Cardiovascular reactivity to psychological stress in aerobically trained versus untrained mild hypertensives and normotensives

Cardiovascular reactivity to video game and mental arithmetic stressors was compared among three groups of men: aerobically trained mild hypertensives, untrained mild hypertensives, and a comparison group of untrained normotensives. Relative to the untrained hypertensives, the trained hypertensives reacted to the video game with marginally smaller systolic blood pressure and diastolic blood pressure, but there were no significant differences between these groups in reactivity during the mental arithmetic task. Comparisons between each hypertensive group and the normotensive group showed that blood pressure (BP) reactivity of normotensives during the video game was generally similar to that of trained hypertensives but smaller than that of untrained hypertensives. These results indicate that aerobic training, which has been found to reduce resting BP in mild hypertensives, may also exert a favorable impact in reducing cardiovascular reactivity of hypertensives during some stressful situations.     

Open-field behavior in two models of genetic hypertension and the behavioral effects of salt excess

In order to assess the relationship of behavior to blood pressure and salt intake, open-field behavior was studied in 123 rats of the spontaneously hypertensive (SHR), Wistar-Kyoto (WKY), Sprague-Dawley (SD), and Dahl resistant (DR) and sensitive (DS) strains. DS rats become hypertensive upon exposure to either high dietary salt or psychogenic stress, while DR rats remain normotensive. A circular photobeam open field was used under full room illumination. Three 5-min trials were given on consecutive days. Rats were tested with or without 5 days of an 8% NaCl diet. We found that DS rats were less active than DR rats, regardless of diet. In contrast, SHR rats were more active than WKY rats. However, DS and SHR rats were equally active. Thus, behavioral differences between these two models of hypertension are expressed by the normotensive control strains. The relative ranking of activity levels between strains was DR = SD greater than SHR = DS greater than WKY. High-salt-enhanced intertrial habituation, defined as the decrease in activity across trials (DS, 100%; SD, 82%; SHR, 90%; WKY, 1350%; but DR, -50%) as well as intratrial habituation, defined as the decrease from the first to the second half of the trial (14%, all subjects). Defecation was increased with high salt (DS, 975%; SD, 59%; SHR, 267%; WKY, 89%; but DR, 40%). These effects of high salt may reflect an increase in an emotionality factor. DR rats were largely resistant to the behavioral effects of salt. Total activity was positively correlated with blood pressure in hypertensive rats, r(42) = 0.33, p less than .01, but negatively correlated in normotensive rats, r(81) = -0.34, p less than .01. The proportion of total activity occurring in the first half of the trial for the initial test day was correlated with blood pressure in normotensive rats r(81) = 0.44, p less than .01. Dietary salt excess has behavioral as well as cardiovascular consequences.     

Relations among heavy training stress,mood state,and performance for male junior rowers

This study investigated the influence of rapidly increased training volume on performance and recovery-stress state perceived by 10 male junior rowers. The training during the 6-day period amounted to 21.5 +/- 2.2 hr., which was equivalent to an average increase in training load by approximately 100% compared to their average training volume during the previous 4 wk. The time to row 2,000 m on a rowing ergometer and resting cortisol level were significantly increased after the 6-day training period. Scores on subscales of the Recovery Stress Questionnaire for Athletes significantly increased for somatic component of stress (Fatigue) and decreased factor indicating recovery (Social Relaxation) after the heavy training period. A correlation of .63 was found between increased training volume and scores on the Conflicts/Pressure subscale at the end of the heavy training period. Correlations were also found between changes in training volume with changes on subscales of Sleep Quality (r=-.64) and Burnout/Personal Accomplishment (r=-.66). Changes in resting cortisol levels as a result of heavy training stress were related to the changes in the following stress subscales: Social Stress (r=.76), Fatigue (r=.64), Disturbed Breaks (r=.65), and Fitness/Injury (r=.67). Changes in performance, perceived recovery-stress state and resting plasma cortisol level reflect increased stress due to high training. These results suggest that the Recovery Stress Questionnaire for Athletes could be used to evaluate the effects of rapidly increased training volume for male junior rowers.     

Race differences in stress-induced reactivity in young adults

The cardiovascular response to the stress of mental arithmetic was studied in young Black and White adults. Stress-induced reactivity was studied before and following 14 days of oral sodium loading (10 gm NaCl per day). Marginal hypertensives, both Black and White, had greater systolic blood pressure (SBP) levels (p less than 0.001) and greater diastolic blood pressure (DBP) levels (p less than 0.01) in response to stress. Whites had a greater SBP level during mental stress than Blacks (p = 0.008) and greater reactivity (change from baseline; p less than 0.001). The prevalence of sodium sensitivity was greater in Blacks (37.3%) than in Whites (18.4%). Sodium loading did not augment the BP reactivity to the mental stress in any of the racial or BP groups. These data demonstrate racial variation in the cardiovascular response to centrally mediated adrenergic stimuli. The results also suggest that mild BP elevation in Blacks may be regulated through changes in vascular resistance.