Inducing unconscious stress: Cardiovascular activity in response to subliminal presentation of threatening and neutral words

Stress‐related cognitive processes may occur outside of awareness, here referred to as unconscious stress, and affect one's physiological state. Evidence supporting this idea would provide necessary clarification of the relationship between psychological stress and cardiovascular (CV) health problems. We tested the hypothesis that increases in mean arterial pressure (MAP) and total peripheral resistance (TPR) and decreases in heart rate variability (HRV) would be larger when threatening stimuli are presented outside of awareness, or subliminally, compared with neutral stimuli. Additionally, it was expected that trait worry and resting HRV, as common risk factors for CV disease, would moderate the effect. We presented a subliminal semantic priming paradigm to college students that were randomly assigned to the threat (n = 56) or neutral condition (n = 60) and assessed changes from baseline of MAP, TPR, and HRV. Level of trait worry was assessed with the Penn State Worry Questionnaire. The findings indicate that CV activity changed according to the hypothesized pattern: A higher MAP and TPR and a lower HRV in the threat condition compared with the neutral condition were found with practically meaningful effect sizes. However, these findings were only statistically significant for TPR. Furthermore, changes in CV activity were not moderated by trait worry or resting HRV. This is the first study to explicitly address the role of subliminally presented threat words on health‐relevant outcome measures and suggests that unconscious stress can influence peripheral vascular resistance.     

Cardiovascular reaction to job stress in middle-aged train drivers

In this study, cardiovascular (CV) response to a standard laboratory challenge was compared to 24-hr noninvasive monitoring of heart rate (HR) and blood pressure (BP) in 30 healthy middle-aged train drivers. Laboratory stress test consisted of the orthostatic test, the cold pressor test, the Valsalva maneuver, the Stroop test, and the numerical square. In addition, the participants completed an extensive questionnaire on their health state and family health history, lifestyle, job stress, social and family support, personality characteristics, and health risk behaviors. In waking activities (leisure time, traveling to work, preparations for driving, and an uneventful driving) HR and systolic Wood pressure (SBP), but not diastolic Wood pressure (DBP), were normal (e.g., mean HR = 78.3, SBP = 128.6. and DBP= 92.3 during driving). In occasional stressful work situations, most participants reacted with a considerable rise in SBP and DBP (maximum values 201 for SBP and 126 for DBP). Interindividual differences in maximum BP reactions to emergency stress were predicted reliably by several psychological characteristics and by the CV reactions to the laboratory psychological challenge. The frequency, intensity, and persistence of psychological and physiological reactions to urgent situations appear to be more relevant measures of the health impact of psychological job stress than are the shift average values of physiological stress markers.     

Cardiovascular response to Stroop: Effect of verbal response and task difficulty

The purpose was to examine the effect of verbal response and task difficulty on cardiovascular response to the Stroop task. Heart rate, mean arterial blood pressure, forearm blood flow (FBF), and catecholamine response of 13 males was assessed during 3, 5-min differing versions of the Stroop task. Heart rate, epinephrine, and FBF were significantly greater during Stroop 1 (the color-word conflict task) compared to Stroop 3 (a non-verbal version of Stroop where participants responded cognitively without any oral or behavioural response), whereas mean arterial pressure was significantly greater during Stroop 1 than that of Stroop 2 (slides in monochrome without color conflict) and Stroop 3. Rating of level of difficulty and concentration was lower for Stroop 2 compared to the other two Stroop tasks. These results suggest that performance of the traditional Stroop task caused significant cardiovascular, FBF, and epinephrine reactivity. This reactivity was attenuated during reading of monochrome words and was virtually abolished when performing the Stroop without verbally responding.     

Cardiovascular response to Stroop: effect of verbal response and task difficulty

The purpose was to examine the effect of verbal response and task difficulty on cardiovascular response to the Stroop task. Heart rate, mean arterial blood pressure, forearm blood flow (FBF), and catecholamine response of 13 males was assessed during 3, 5-min differing versions of the Stroop task. Heart rate, epinephrine, and FBF were significantly greater during Stroop 1 (the color-word conflict task) compared to Stroop 3 (a non-verbal version of Stroop where participants responded cognitively without any oral or behavioural response), whereas mean arterial pressure was significantly greater during Stroop 1 than that of Stroop 2 (slides in monochrome without color conflict) and Stroop 3. Rating of level of difficulty and concentration was lower for Stroop 2 compared to the other two Stroop tasks. These results suggest that performance of the traditional Stroop task caused significant cardiovascular, FBF, and epinephrine reactivity. This reactivity was attenuated during reading of monochrome words and was virtually abolished when performing the Stroop without verbally responding.     

Cardiovascular diseases and oxidative stress

We are always exposed to oxidative stress, when oxygen is used for production of energy for our daily activity. Mild to moderate oxidative stress affects intracellular signal transduction, accelerating the protective system for oxidation; thereby inflammatory cytokines are produced leading to increased levels of acute phase proteins. Vascular endothelial cells protect the vessels from oxidative stress, however, when they are damaged by shear stress to the vascular wall, oxidation spreads into the subendothelial matrix, leading to oxidation of low-density lipoproteins(LDL) accumulated there. Oxidized LDL is easily and abundantly taken up into macrophages via the scavenger receptors such as LOX-1, which leads to the formation of atherosclerosis. Markers for oxidative stress in vivo are being sought for prevention and treatment of cardiovascular diseases. There are a number of parameters as candidates, and among them, we chose biopyrrins, oxidative products of bilirubin, and have studied their role in coronary heart diseases. Urinary excretions of biopyrrins are significantly elevated in patients with coronary arterial stenosis and with ischemic changes on electrocardiogram. Similar finding have been obtained in patients with vasospastic angina. These findings suggest that markers for oxidative stress will be a good laboratory test for evaluation of coronary heart diseases.     

Cardiovascular response to localized heating of the anterior hypothalamus

1. The effects, on the systemic and pulmonary circulation, of localized heating of the anterior hypothalamus, at different environmental temperatures, have been studied in the unanaesthetized ox.2. In a cool environment (15 degrees C), heating the hypothalamus elicited panting which was associated with increases in cardiac output, heart rate, pulmonary arterial pressure and central blood volume, and decreases in systemic total peripheral resistance, and the percentage of red cells in mixed venous blood.3. In a hot environment (40 degrees C), the cardiovascular responses were of smaller magnitude than in the cool environment. It was suggested that the smaller responses in the hot environment were probably related to a higher level of blood flow through the skin before the hypothalamus was heated.4. The cardiovascular responses to localized heating of the anterior hypothalamus were similar to those which occur during hyperthermia. However, there were also differences between the effects of the two procedures and it was concluded that hyperthermia involves the stimulation of other receptors in addition to those in the anterior hypothalamus.     

Openness to experience and adapting to change: Cardiovascular stress habituation to change in acute stress exposure

Underlying psychophysiological mechanisms of effect linking openness to experience to health outcomes, and particularly cardiovascular well‐being, are unknown. This study examined the role of openness in the context of cardiovascular responsivity to acute psychological stress. Continuous cardiovascular response data were collected for 74 healthy young female adults across an experimental protocol, including differing counterbalanced acute stressors. Openness was measured via self‐report questionnaire. Analysis of covariance revealed openness was associated with systolic blood pressure (SBP; p = .016), and diastolic blood pressure (DBP; p = .036) responsivity across the protocol. Openness was also associated with heart rate (HR) responding to the initial stress exposure (p = .044). Examination of cardiovascular adaptation revealed that higher openness was associated with significant SBP (p = .001), DBP (p = .009), and HR (p = .002) habituation in response to the second differing acute stress exposure. Taken together, the findings suggest persons higher in openness are characterized by an adaptive cardiovascular stress response profile within the context of changing acute stress exposures. This study is also the first to demonstrate individual differences in cardiovascular adaptation across a protocol consisting of differing stress exposures. More broadly, this research also suggests that future research may benefit from conceptualizing an adaptive fitness of openness within the context of change. In summary, the present study provides evidence that higher openness stimulates short‐term stress responsivity, while ensuring cardiovascular habituation to change in stress across time.     

Cardiovascular response to interval and continuous training in women

Summary Three groups of five women (age = 18–25 years) participated in a 12-week training program. Cardiovascular responses up to 85% VO₂ max to interval (ITG) and continuous (CTG) training were studied in two groups, before training and after 4, 8, and 12 weeks of training four times per week. A control group was assessed before and after 6 and 12 weeks. Both exercise groups demonstrated significant increases in Ca _o2–C¯v _o2 after 8 weeks with only slight further increases after 12 weeks (CTG=8.9%, ITG=20.0% at 85% VO₂ max). No significant changes were noted in either group in SV (+ 5 ml ITG, + 9 ml CTG) or in their Q _c. These results indicated that, in response to high intensity training, women may demonstrate similar cardiovascular adaptations to training as have been observed for men.Supported by the Ontario Exercise-Heart Collaborative Study, a grant from the Ontario Department of Health — Project No. 263. Principal Investigators at the University of Western Ontario include Doctors C. Buck, D. A. Cunningham, P. A. Rechnitzer, and M. S. Yuhasz     

Cardiovascular responses to occupational stress and caffeine in telemarketing employees

Cardiovascular responses to the combination of caffeine and a challenging occupational activity were examined using a within-subject, double-blind design. Seventeen female and 11 male telemarketing employees received drinks that did and did not contain 250 mg of caffeine on two consecutive days, with order of presentation counterbalanced across subjects. Repeated measurements of systolic and diastolic blood pressure, heart rate, and digital blood volume pulse were obtained during a pre-drug resting baseline and a post-drug working period on each day. Repeated measures analyses of variance revealed significant main effects of Period on all measures of cardiovascular activity, indicating that occupational demands elicited significant cardiovascular adjustments. Only systolic blood pressure revealed a significant Drug X Period effect, indicating that responses were significantly greater on the caffeine versus placebo day. The changes in diastolic blood pressure and heart rate, although not significant, were consistent in direction with the results from previous laboratory studies. There were no significant differences between males and females in cardiovascular response to the combination of stress and caffeine.     

Cardiovascular response to exercise in humans following acclimatization to extreme altitude

The purpose of this study was to assess the effects of acclimatization to extreme altitude on the cardiovascular system, using vagal and adrenergic blockade and acute restoration of normoxia during exercise to maximum with one and two legs. Fourteen climbers on an expedition to the Himalayas were studied at a lower base camp (5250 m) following 56–81 days at altitudes between 5250 and 8700 m. After acclimatization, peak heart rate (HR_peak), oxygen uptake (o_2k) and noradrenaline (NA) were similar during maximal one- and two-legged cycling, whereas peak plasma lactate was higher during the one-legged protocol. HR_peak (range 113–168 beats min“¹) was lowest when subjects returned from the higher camps. The degree of partial restoration of HR_peak to more normal values within seconds of 60% 0₂ inhalation (range 5–35 beats min?^l HR_peak increase) was greatest in subjects with low HR_peak. HR responses to /?-l blockade increased as a function of HR_peak and the HR responses to atropine were the least in subjects with high HRpeak- These findings suggest that (a) the reduction in HR_peak is linked to the duration and severity of the hypoxaemia, (b) the degree of restoration of HR_peak with acute normoxia is dependent on the level of attenuation or down-regulation of cardiac sympathetic activation (SNA), (c) cardiac vagal drive is masked to a lesser extent in chronic hypoxia because of attenuated SNA and lower HR_peak values, and (d) the lower blood lactate levels at altitude is a function of muscle mass involvement rather than adrenergic activation, as normal peak values were reached during exercise with a small muscle mass.     

Cardiovascular reactivity to stress: an examination of familial trends

Mental stress elicits changes in cardiovascular functioning such as increases in blood pressure and heart rate and leads to biochemical changes which may facilitate the development of cardiovascular disease. This study examined the correlations between levels of cardiovascular change seen in healthy fathers and their sons who underwent stress testing (cold pressor test and mental arithmetic). No correlation between fathers' and sons' levels of reactivity were found. Certain personality traits such as hostility and anger directed inward have previously been shown to correlate with both reactivity and presence of arterial disease. In this study, hostility levels and assertiveness levels were measured and were found to correlate modestly with reactivity in the fathers but not in the sons. Sons showed less assertiveness and greater hostility overall; thus, restriction of the range of these variables may limit potential correlations with physiological measures in this group. Finally, although no family trends were observed, several of the adolescents did show extreme changes under stress, suggesting reactivity is a trait which is expressed early in life.     

Cardiovascular stress reactivity tasks successfully predict the hypotensive response of isometric handgrip training in hypertensives

This study aimed to determine whether: (a) isometric handgrip (IHG) training lowers resting blood pressure (BP), (b) cardiovascular reactivity to a serial subtraction (SST), IHG (IHGT), and cold pressor (CPT) task predicts this hypotensive response, and (c) cardiovascular reactivity is attenuated posttraining. Resting BP and cardiovascular reactivity to a SST, IHGT, and CPT were measured in 24 hypertensives (51–74 years) before and after 10 weeks of IHG training (n = 12) or control (n = 12). IHG training lowered resting BP (Δ8/5 mmHg), whereby the decrease in systolic BP was correlated to pretraining systolic BP reactivity to the SST (r = ?.85) and IHGT (r = ?.79; all ps < .01), but not the CPT (r = .34; p > .01). Furthermore, following IHG training, systolic BP reactivity to the SST (Δ7 mmHg) and IHGT (Δ8 mmHg) was reduced (all ps < .01). The results offer promising implications for hypertensives and may provide a tool to identify IHG training responders.