Working memory impairment and cardiovascular hyperarousal in young primary insomniacs

We investigated memory performance and cardiovascular activity in 13 primary insomniacs (PI) compared to 13 good sleepers (GS). Cardiovascular and hemodynamic measures, including heart rate, pre‐ejection period, and blood pressure, were continuously recorded at rest and during two memory tasks. PI showed working memory impairment under high cognitive load, but performed as well as GS in an easy memory task. In addition, PI exhibited markers of hyperarousal both at rest and during the execution of the two tasks. However, we failed to find a clear‐cut relationship between cardiovascular hyperarousal and cognitive performance in insomniacs. Our data provide further evidence of both cognitive impairment and cardiovascular hyperarousal in primary insomnia, while not supporting the hypothesis of hyperarousal as a compensatory mechanism to overcome cognitive challenges.     

Cardiovascular down‐regulation in essential hypotension: Relationships with autonomic control and sleep

In this work, we aimed to clarify the autonomic involvement in the cardiovascular down‐regulation in essential hypotension. The relationships between cardiovascular response and sleep quality were also examined. Thirteen female hypotensives and 13 female normotensives performed a stress task followed by polysomnography. Measures derived from blood pressure monitoring, impedance cardiography, and heart rate variability were collected. Hypotensives exhibited lower cardiovascular and autonomic activation than controls during the task. While a better sleep quality (i.e., higher sleep efficiency and lower nocturnal wakefulness) correlated with a reduced reactivity in normotensives, the opposite pattern occurred in hypotensives. The results suggest that a blunted response in both autonomic branches underlies the cardiovascular hypoactivation in hypotension. Further, good sleep seems to be associated with optimal levels of physiological reactivity.     

Sex differences in cardiac autonomic function of depressed young adults

Background

Cardiac autonomic dysfunction has been proposed as an important contributing factor to the increased cardiovascular risk observed in major depression (MDD). However, the evidence regarding alterations in heart rate variability (HRV) in otherwise healthy depressed subjects has been inconclusive.

Methods

A case–control study in 50 treatment-naïve young adults with a first MDD episode without comorbid psychiatric disorders and 50 healthy control subjects was conducted. Time- and frequency-domain indexes of HRV were determined at baseline supine and after 5-min of orthostatic stress at 60°.

Results

There were no significant differences in the time- or frequency-domain variables of HRV between depressed patients and controls. However, a random-effect ANOVA model showed that during orthostatic stress depressed men had a reduced HRV and decreased parasympathetic activity compared to control subjects, while no differences were found between depressed women and controls.

Conclusion

These results suggest a sex-dependent relationship between major depression and cardiac autonomic dysfunction and provide one potential explanation for sex differences in the association of depressive symptoms with cardiovascular morbidity.     

Autonomic cardiac control. II. Noninvasive indices and basal response as revealed by autonomic blockades

Heart period, systolic time intervals, low and high frequency heart period variability, blood pressure, and respiration were measured in female subjects under three drug conditions (saline, atropine sulfate, metoprolol) while sitting and standing on three consecutive days. Following preinfusion baseline recordings, saline, metoprolol (14 mg), or atropine sulfate (2 mg) was infused for 15 min (by using a double-blind procedure). Recordings were taken during a postinfusion baseline and in response to an orthostatic stressor (standing versus sitting postures). At the end of the metoprolol session, atropine sulfate was infused and responses were monitored during the post-infusion (i.e., double blockade) baseline and during orthostatic stressor. Analyses of the blockade data revealed that the preejection period (PEP) reflected sympathetic but not vagal influences on the heart, and high frequency (HF, 0.12–0.40 Hz) heart rate variability (respiratory sinus arrhythmia) reflected vagal but not sympathetic influences on the heart. No other measure provided a specific index of the tonic sympathetic or vagal activation of the heart. Postinfusion PEP under saline predicted individual differences in postinfusion cardiac sympathetic activation, whereas postinfusion heart period (but not HF variability) under saline predicted individual differences in postinfusion cardiac vagal activation.     

Priming recognition in good sleepers and in insomniacs

Insomniacs often report memory and concentration problems, but these complaints have not been consistently supported by performance measurements. Furthermore, while the majority of studies have addressed explicit memory, few have investigated the implicit domain, and very little is known concerning other types of implicit memory besides procedural memory, such as priming. Thus, the purpose of the study was to investigate priming effect for visual stimuli in insomniacs and good sleepers. Twenty‐three insomniacs and 20 good sleepers performed a visual priming task in which they were asked to name new and old pictures presented at nine ascending levels of spatial filtering. Both neutral and sleep‐related stimuli were used, as previous research evidenced an attentional bias for sleep‐related stimuli. Visual priming effect was observed in both groups, suggesting that poor sleep quality does not affect this type of implicit memory. However, the identification process in insomniacs is influenced by the nature of the stimulus to identify: insomniacs recognized both new and old sleep‐related stimuli at lower spatial frequencies compared with good sleepers. The tendency to selectively attend to sleep‐related stimuli may influence top‐down processes occurring during identification of filtering stimuli, by determining a pre‐allocation of attentional resources and facilitating identification processes even when sensorial information is scant. Differences in the identification processes of sleep‐related stimuli compared with neutral ones should be carefully taken into account as possible pre‐clinical markers of insomnia in poor sleepers.     

Analysis of cardiac autonomic modulation in obese and eutrophic children

INTRODUCTION:

Obesity causes alterations in cardiac autonomic function. However, there are scarce and conflicting data on this function with regard to heart rate variability in obese children.

OBJECTIVE:

To compare the autonomic function of obese and eutrophic children by analyzing heart rate variability.

METHODS:

One hundred twenty-one children (57 male and 64 female) aged 8 to 12 years were distributed into two groups based on nutritional status [obese (n  =  56) and eutrophic (ideal weight range; n  =  65) according to the body mass index reference for gender and age]. For the analysis of heart rate variability, heart rates were recorded beat by beat as the children rested in the dorsal (prone) position for 20 minutes. Heart rate variability analysis was carried out using linear approaches in the domains of frequency and time. Either Student''s t-test or the Mann-Whitney U-test was applied to compare variables between groups. Statistical significance was set at 5%.

RESULTS:

The SDNN, RMSSD, pNN50, SD1, SD2, LF and HF indices in milliseconds squared were lower among the obese children when compared to the eutrophic group. There were no alterations in the SD1/SD2 ratio, LF/HF ratio, LF index or HF index in normalized units. There was a significant difference between groups in the RR interval (R-to-R EKG interval).

CONCLUSION:

The obese children exhibited modifications in heart rate variability, characterized by a reduction in both sympathetic and parasympathetic activity. These findings stress the need for the early holistic care of obese children to avoid future complications.     

The influence of social stress on time perception and psychophysiological reactivity

Time perception is a fundamental component of everyday life. Although time can be measured using standard units, the relationship between an individual's experience of perceived time and a standard unit is highly sensitive to context. Stressful and threatening stimuli have been previously shown to produce time distortion effects, such that individuals perceive the stimuli as lasting for different amounts of time as compared to a standard unit. As a highly social species, humans are acutely sensitive to social stressors; however, time distortion effects have not been studied in the context of social stress. We collected psychophysiological (electrocardiogram and impedance cardiography) and time perception data before, during, and after a modified version of the Trier Social Stress Test for 42 participants. Based on prior theories and evidence from the time perception literature, we hypothesized that experiencing a stressful event would result in time distortion. This hypothesis was supported by the data, with individuals on average reproducing short and long duration negative and positive stimuli as lasting longer after experiencing social stress, t(41) = −3.55, p = .001, and t(41) = −4.12, p < .001 for negative stimuli, and t(41) = −2.43, p = .02, and t(41) = −3.07, p = .004 for positive stimuli. However, changes in time perception were largely unrelated to psychophysiological reactivity to social stress. These findings are in line with some other studies of time distortion, and provide evidence for the interoceptive salience model of time perception. Implications for mechanisms of time distortion are discussed.     

Difference in human cardiovascular response between upright and supine recovery from upright cycle exercise

Cardiovascular responses were examined in seven healthy male subjects during 10 min of recovery in the upright or supine position following 5 min of upright cycle exercise at 80% peak oxygen uptake. An initial rapid decrease in heart rate (f _c) during the early phase of recovery followed by much slower decrease was observed for both the upright and supine positions. The average f _c at the 10th min of recovery was significantly lower (P < 0.05) in the supine position than in the upright position, while they were both significantly greater than the corresponding pre-exercise levels (each P < 0.05). Accordingly, the amplitude of the high frequency (HF) component of R-R interval variability (by spectrum analysis) in both positions was reduced with a decrease in mean R-R interval, the relationship being expressed by a regression line – mean R-R interval = 0.006 × HF amplitude + 0.570 (r = 0.905, n = 28, P < 0.001). These results would suggest that the slower reduction in f _c following the initial rapid reduction in both positions is partly attributable to a retardation in the restoration of the activity of the cardiac parasympathetic nervous system. Post-exercise upright stroke volume (SV, by impedance cardiography) decreased gradually to just below the pre-exercise level, whereas post-exercise supine SV increased markedly to a level similar to that at rest before exercise. The resultant cardiac output (Q˙ _c) and the total peripheral vascular resistance (TPR) in the upright and supine positions returned gradually to their respective pre-exercise levels in the corresponding positions. At the 10th min of recovery, both average SV and Q˙ _c were significantly greater (each P < 0.005) in the supine than in the upright position, while average TPR was significantly lower (P < 0.05) in the supine than in the upright position. In contrast, immediately after exercise, mean blood pressure dropped markedly in both the supine and upright positions, and their levels at the 10th min of recovery were similar. Therefore we concluded that arterial blood pressure is maintained relatively constant through various compensatory mechanisms associated with f _c, SV, Q˙ _c, and TPR during rest and recovery in different body positions. Accepted: 4 September 1999     

The impact of menstrual cycle phase on cardiac autonomic regulation

This study investigated menstrual cycle phase differences in heart rate (HR) and RR interval variability (RRV) in 49 healthy, premenopausal, eumenorrheic women (age 30.2±6.2 years). HR and RRV were computed from ambulatory 24-h electrocardiogram, collected for up to 6 days, with at least 1 day each during early to midfollicular and midluteal menstrual phases. Phase effects on HR and RRV were assessed using linear mixed effects models with a random intercept to account for the correlation of observations within each subject as well as intrasubject variation. During follicular phase monitoring, women had significantly lower average HR (−2.33 bpm), and higher standard deviation, the root mean squared successive difference, and high frequency (0.04–0.15 Hz) and low frequency (0.15–0.40 Hz) RRV than during the luteal phase. These results provide strong support for the influence of menstrual phase on cardiac autonomic regulation in premenopausal women.     

Gender differences in cardiac autonomic modulation during medical internship

Medical internship is known to be a time of high stress and long working hours, which increases the risk of depression and cardiovascular disease. Gender differences in medical interns' cardiovascular risk have not been reported previously. Thirty‐eight medical interns (29 males) were repeatedly tested for depressive symptoms using the Hospital Anxiety and Depression Scale and 5‐min spectral analysis of heart rate variability (HRV) at 3‐month intervals during their internship. Among the male interns, the variance of the heart rate decreased at 6, 9, 12 months, and a reduced high frequency, which suggests reduced cardiac parasympathetic modulation, was found at 9 and 12 months into their internship. Increased depressive symptoms were also identified at 12 months in the male group. No significant differences in depression or any of the HRV indices were identified among the female interns during their internship.     

Gastric myoelectrical and autonomic cardiac reactivity to laboratory stressors

We evaluated the effects of two laboratory stressors (speech preparation and isometric handgrip) on gastric myoelectrical and autonomic cardiac activity, and the extent to which autonomic responses to these stressors and somatization predict reports of motion sickness during exposure to a rotating optokinetic drum. Both stressors prompted a decrease in preejection period (PEP) and respiratory sinus arrhythmia (RSA), and an increase in a dysrhythmic pattern of gastric myoelectrical activity, termed gastric tachyarrhythmia. Stressor-induced decreases in RSA and higher somatization scores predicted increased reports of motion sickness during drum rotation. These results demonstrate that laboratory stressors concurrently affect gastric myoelectrical activity and autonomic control of the heart, and that stressor-induced decreases in RSA and higher levels of somatization predict motion sickness susceptibility.     

Individual differences in the autonomic origins of heart rate reactivity: the psychometrics of respiratory sinus arrhythmia and preejection period

Heart rate reactivity has been conceptualized, at least implicitly, as a unidimensional construct ranging from low to high, reflecting individual differences in adrenergic reactivity to daily stressors. However, an individual's classification as high in heart rate reactivity ignores possible individual differences in the autonomic origins of this reactivity. Sixty-eight women were exposed to orthostatic and speech stressors to determine the psychometric properties (postural stability, convergent and discriminant validity) of heart rate, preejection period, and respiratory sinus arrhythmia. Results revealed that (a) basal, stress, simple reactivity (stress - baseline), and residualized change indices of heart rate, preejection period, and respiratory sinus arrhythmia were stable across postures and (b) heart rate reactivity was significantly related to preejection period and respiratory sinus arrhythmia reactivity, whereas the latter two measures were unrelated. Reactivity classifications may therefore be significantly improved by attention to concurrent estimates of the activity of both autonomic branches.     

Effects of long-term exercise training on cardiac autonomic nervous activities and baroreflex sensitivity

Reductions in tonic vagal controls of the heart and depressed baroreflex sensitivity (BRS) have been associated with a postural fall in blood pressure (BP) and the incidence of cardiac events among older people. We examined the hypothesis that BP regulation during orthostatic challenge as well as heart rate variability (HRV) at rest can be better maintained in long-term exercise-trained, healthy, older men (aged 60–70 years). Subjects were classified into two groups; long-term exercise-trained (LTET, n=14) and sedentary (SED, n=10) according to their history of physical activity. Prior to the dynamic BRS assessment, supine resting autonomic cardiac modulation was assessed by means of time domain HRV [standard deviation of ECG R–R interval (RRISD) and the coefficient of variation (CV)]. The BRS was assessed during 60° head-up tilting by simultaneously measuring beat-by-beat systolic blood pressure (SBP) and ECG R–R interval changes. The BRS gain was determined by the regression slope coefficient based on the extent of the SBP fall and the corresponding ECG R–R shortening during the orthostatic challenge. The results indicated that the LTET group manifested greater ECG R–R interval fluctuations with significantly higher resting RRISD and CV, compared with the SED group [59.5 (10.4) versus 27.7 (7.8) ms, p<0.05; 5.5 (0.8) versus 2.8 (0.7)%, p<0.05], respectively. Using dynamic BRS testing during the acute orthostatic challenge, the LTET group showed a significantly higher BRS gain than the SED [6.4 (0.8) versus 3.8 (0.6) ms·mmHg⁻¹, p<0.017] group. These results indicate that CV and BRS are well maintained in healthy, LTET older individuals when compared with their sedentary peers. Our data suggest that this augmented autonomic cardiac modulation reflects better parasympathetic responsiveness in LTET individuals. Data provide further support for long-term exercise training as another possible cardioprotective factor that might decrease susceptibility to ventricular fibrillation as well as assist arterial BP at the onset of an orthostatic challenge in older men. Electronic Publication     

Hostility and sex differences in the magnitude, duration, and determinants of heart rate response to forehead cold pressor: Parasympathetic aspects of risk

Recent models hypothesize that hostility confers increased risk of CHD through weaker parasympathetic dampening of cardiovascular reactivity (CVR). We tested this possibility using the forehead cold pressor task, a common maneuver which elicits the “dive reflex” characterized by a reflexive decrease in HR presumably through cardiac-parasympathetic stimulation. Participants were initially chosen from the outer quartiles of a sample of 670 undergraduates screened using the hostility subscale of the Aggression Questionnaire ([Buss, A.H., Perry, M., 1992. The Aggression Questionnaire. Journal of Personality and Social Psychology, 63, 452-459.]). The final sample of 80 participants was evenly divided between men and women and high and low hostility. Following a 10-min baseline, participants underwent a 3-min forehead cold pressor task. The task evoked a significant HR deceleration that was mediated by PNS activation, as assessed by respiratory sinus arrhythmia (RSA). Replicating prior research, men displayed greater decrease in HR. More important, low hostiles maintained larger HR deceleration over time compared to high hostiles although the autonomic basis for this effect was unclear. The findings broaden understanding of hostility and sex-related cardiovascular functioning and support the task as a method for evoking PNS-cardiac stimulation.     

Temperament, health-related behaviors, and autonomic cardiac regulation: the cardiovascular risk in young Finns study

Temperament, as indicated by Cloninger's psychobiological model predicts coronary heart disease risk, but its association with autonomic cardiac regulation, a potential mediating mechanism, is unclear. We examined the associations between temperament traits and autonomic cardiac regulation in a resting situation in 798 women and 580 men derived from a population-based sample. After adjustment for age and sex, harm avoidance was associated with lower level of high-frequency (HF) variation, root mean square successive differences (RMSSDs), the percentage of successive R–R intervals >50 ms (pNN50) and higher heart rate (HR) (all p ≤ 0.005), suggesting that harm avoidance is related to low parasympathetic activity. Additional adjustments for behavioral factors attenuated these associations more than the adjustment for biological risk factors. Novelty seeking was associated with higher RMSSD (p = 0.007) and pNN50 (p = 0.012) and lower heart rate (p < 0.001). With adjustment for behavioral risk factors, the associations with RMSSD (p = 0.136) and pNN50 (p = 0.236) attenuated to the null, but adjustment for biological risk factors had little effect. Reward dependence and persistence were unrelated to indices of cardiac regulation.     

Impedance-Derived cardiac indices in supine and upright exercise

Impedance cardiography was used to determine the classical systolic time intervals (STI's) (i.e., pre-ejection period (PEP), left ventricular ejection time (LVET) and the quotient PEP/LVET), in young, healthy, male subjects during supine and seated exercise. With increasing exercise, there was a tendency toward decreases in PEP, LVET, and PEP/LVET. In the seated position, there was an increase in transthoracic Z_o incident to the caudal migration of thoracic blood—a result of the postural change. With seated exercise, there were—in contrast to supine exercise—greater decreases in PEP/LVET and greater increases in the Heather index. Similarly, there was a tendency toward increases in dZ/dt_min and the Rapid Ejection Index. We suggest that these differences are related to increased myocardial contractility resulting from the postural augmentation of cardio-sympathetic activity, added to that of exercise per se. This study, as well as previous ones, indicates that impedance cardiography is reliable, effective, and more practicable than the arteriographic method for monitoring STI's. We also believe that certain impedance-derived indices (i.e., transthoracic Z_o, dZ/dt_min and the Heather Index) have considerable potential value for physiologic and clinical investigation.     

Systemic hypoxia affects cardiac autonomic activity and vascular hemodynamic control modulated by physical stimulation

This study investigates how various hypoxic interventions affect cardiac autonomic activity and hemodynamic control during posture change and the Valsalva maneuver. Ten healthy sedentary men exposed to 12, 15 and 21% O₂ for 1 h in a normobaric hypoxia chamber in a random order. Before and after various O₂ concentrations were administered, subjects performed the sit-up test and Valsalva maneuver, respectively. An impedance plethysmography was utilized to measure blood pressure (BP) and vascular hemodynamics, whereas spectral analysis of heart rate variability (HRV) was performed to determine cardiac autonomic activity. Analytical results can be summarized as follows: while the patient rests in a supine position, exposure to 12% O₂ reduces the ratio of lower to upper extremity systolic BP, which is accompanied by (1) suppressed arterial reactive hyperemia and increased venous flow resistance, as well as (2) decreased total power and high frequency (HF) and increased low frequency (LF) and the ratio of LF to HF. Moreover, the hypoxia-induced changes of time and frequency domains in HRV at resting supine disappear following the sit-up test, whereas this hypoxic exposure attenuates the BP and heart rate responses to the Valsalva maneuver. Conversely, resting and physical stimuli-mediated HRV and vascular hemodynamic values are unaltered by both 15 and 21% O₂ exposures. We conclude that acute hypoxic exposure affects cardiovascular autonomic functions, with reactions determined by the intervening O₂ concentrations. Moreover, the BP and cardiac autonomic responses to 12% O₂, but not 15% O₂, exposure are depressed while performing posture change and the Valsalva maneuver.     

Streptozotocin-induced type 1 and 2 diabetes in rodents: a model for studying diabetic cardiac autonomic neuropathy

BackgroundSeveral animal models are continually being developed to study diabetic complication. Several conflicting regimen for diabetes induction exist in the literature with varying dose strength and regimen for different study interest in diabetes. This study aims to show the effect of high dose streptozotocin (STZ) on the one hand compared with multiple low doses after high fat diet induction on diabetic cardiac autonomic neuropathy (DCAN).MethodologyEighty-four Wistar rats were used to demonstrate DCAN induction using 2 approaches one for T1DM (STZ 50mg/kg) and the other for T2DM (HFD for 8 weeks with STZ 25mg/Kg daily for five days). DCAN features were assessed using invasive biomarkers, histology patterns and cardiac nerve densities.ResultsDiabetes induction rate was 76% and 89% in T1DM and T2DM model respectively. T1DM group had significant weight loss, reduced c-peptide, and insulin level post induction. The T2DM additionally showed significantly higher total cholesterol and Homeostatic model assessment (HOMA) compared with control. Serum levels of catecholamine, choactase, nerve growth factor and cardiac nerve density confirms development of DCAN.ConclusionHigh single dose of STZ and HFD with multiple low doses of STZ may be recommended for DCAN study in T1DM and T2DM rat model respectively.     

Association of Type D personality with the autonomic and hemodynamic response to the cold pressor test

Mechanisms relating Type D personality to poor health are largely unknown, with autonomic nervous system function being a candidate. This study examined the physiologic response to cold stress. Undergraduates (N = 101, 84% female) underwent a cold pressor test. An electrocardiogram, impedance cardiogram, and blood pressure were recorded. Type D personality was assessed by self‐report questionnaire. Type D was associated with increased systolic and diastolic blood pressure reactivity. Exploratory analyses showed Type D men to respond with increased respiratory sinus arrhythmia (i.e., higher parasympathetic activity), and decreased pre‐ejection period (i.e., larger sympathetic activity), while Type D women showed a reciprocal response pattern. In conclusion, Type D personality was associated with an exaggerated hemodynamic response to cold stress, which may contribute to an increased risk of hypertension in Type D individuals.     

Stroke volume response to progressive exercise in athletes engaged in different types of training

Summary Using the impedance cardiography method, heart rate ( _c) matched changes on indexed stroke volume (SI) and cardiac output (CI) were compared in subjects engaged in different types of training. The subjects consisted of untrained controls (C), volleyball players (VB) who spent about half of their training time (360 min · week^–1) doing anaerobic conditioning exercises and who had a maximal oxygen uptake ( ) 41% higher than the controls, and distance runners (D) who spent all their training time (366 min·week^–1) doing aerobic conditioning exercises and who had a 26% higher than VB. The subjects performed progressive submaximal cycle ergometer exercise (10 W·min^–1) up to _c of 150 beats·min^–1. In group C, SI had increased significantly (P<0.05) at _c of 90 beats·min^–1 ( + 32%) and maintained this difference up to 110 beats·min^–1, only to return to resting values on reaching 130 beats·min^–1 with no further changes. In group VB, SI peaked (+ 54%) at _c of 110 beats·min^–1, reaching a value significantly higher than that of group C, but decreased progressively to 22010 of the resting value on reaching 150 beats·min^–1. In group D, SI peaked at _c of 130 beats·min^–1 (+ 54%), reaching a value significantly higher than that of group VB, and showed no significant reduction with respect to this peak value on reaching 150 beats·min^–1. As a consequence, the mean CI increase per _c unit was progressively higher in VB than in C (+46%) and in D than in VB (+ 105%). It was concluded that thef _c value at which SI ceased to increase during incremental exercise was closely related to the endurance component in the training programme.