Body fat and blood lipids in postmenopausal women are related to resting autonomic nervous system activity

The present study investigated the activity of the autonomic nervous system (ANS), a major influence in normal physiological function, and its association with unfavorable postmenopausal states in body composition, lipid and/or glucose metabolism, or cardiovascular profiles. Body composition, blood pressure, and blood profiles of lipid and glucose of 175 postmenopausal women were measured. Resting ANS activity was assessed by heart rate variability (HRV) power spectral analysis. To scrutinize the influence of ANS activity levels on postmenopausal obesity-related factors, we divided the subjects into a low group ( < 220 ms²) and a high group ( > 220 ms²), based on the total power of HRV. Low-frequency (P < 0.01) and high-frequency power (P < 0.01) were both significantly lower in the low group. No significant difference was found in age, age at menopause, or years after menopause between the two groups. In contrast, body mass index (P < 0.05), percentages of body fat (P < 0.01), and systolic (P < 0.01) and diastolic (P < 0.01) blood pressure were significantly greater in the low group. As to blood lipid profiles, triglycerides (P < 0.05), total cholesterol (P < 0.05), and low-density lipoprotein cholesterol (P < 0.05) were significantly higher in the low group. Our findings indicate that reduced sympatho-vagal activity is associated with higher postmenopausal body fat content, blood pressure, and blood lipid concentrations. This study further implies that such autonomic depression could be a crucial risk factor in undermining the health and, ultimately, the quality of life, of postmenopausal women.     

Cognitive depressive symptoms associated with delayed heart rate recovery following interpersonal stress in healthy men and women

Among cardiac patients, research suggests that somatic depressive symptoms are more strongly associated with altered cardiovascular responses to stress than cognitive depressive symptoms. This study sought to determine whether this was also the case in healthy individuals. One hundred and ninety-nine adults from the community completed the Beck Depression Inventory II (BDI-II) and underwent psychological laboratory stressors while their blood pressure, heart rate, and heart rate variability were monitored. A cognitive-affective factor and somatic-affective factor were identified within the BDI-II, but only the cognitive factor was associated with reduced heart rate recovery following the stressors in multivariate analyses examining both factors simultaneously. This suggests that cognitive depressive symptoms may be more strongly related to altered stress physiology following psychological stressors.     

Cardiovascular activity during laboratory tasks in women with high and low worry

Worry has been related to delayed stress recovery and cardiovascular disease risk. Cardiovascular responses to a range of laboratory tasks were examined in this study of high and low worriers. Undergraduate women were recruited with the Penn State Worry Questionnaire to form low (n=19) and high (n=22) worry groups. These individuals engaged in six laboratory tasks (orthostatic stress, supine rest, hand cold pressor, mental arithmetic, and worry and relaxation imagery) while heart rate (HR), HR spectral analysis, impedance cardiography, and blood pressure were acquired. The only significant group difference found was a consistently greater HR across tasks in high worriers (p<.05). No group by condition interactions emerged. High trait worry in healthy young women appears to be marked by elevated HR in the absence of autonomic abnormalities. These findings are discussed relative to the literature on worry, with particular reference to its health implications.     

Stress cardiovascular/autonomic interactions in mice

Studies evaluated the role of the autonomic nervous system in the cardiovascular response to stress using radiotelemetric blood pressure (BP) recording coupled with autoregressive spectral analysis. Conscious male C57/BL6 mice with carotid arterial telemetric catheters were exposed to acute episodes of shaker stress before and after administration of cholinergic, beta1-adrenergic and alpha1-adrenergic receptor antagonists. Pulse interval (PI) and systolic arterial pressure (SAP) were analyzed for variance and the low frequency (LF: 0.1-1.0 Hz) and high frequency (HF: 1-5 Hz) spectral components. Stress (5 min) increased BP and heart rate (HR) as well as PI and SAP variability. PI variance increased from 41+/-6 to 75+/-14 ms2 while SAP variance increased from 25+/-5 to 55+/-9 mm Hg2. Autonomic blockade had specific effects on stress-induced changes in PI and SAP and their respective variability. Atropine reduced the tachycardia and abolished the increase in PI variance and its LF component. Data documents that in mice the cholinergic system is fundamental for the maintenance of HR variability. Atropine had no effects on the BP responses, either the increase in SAP or the variance associated with stress. Atenolol blocked the increase in PI and SAP variability induced by stress. Prazosin reduced the tachycardia produced by stress and blocked the increase in PI (only LF) and SAP variability. Using quantitative spectral analysis of telemetrically collected BP data in mice along with pharmacological antagonism, we were able to accurately determine the role of autonomic input in the mediation of the stress response. Data verify the role of sympathetic/parasympathetic balance in stress-induced changes in HR, BP and indices of variance.     

Resistance training for hot flushes in postmenopausal women: Randomized controlled trial protocol

ObjectivesHot flushes and night sweats affect 75% of all women after menopause and is a common reason for decreased quality of life in mid-aged women. Hormone therapy is effective in ameliorating symptoms but cannot be used by all women due to contraindications and side effects. Engagement in regular exercise is associated with fewer hot flushes in observational studies, but aerobic exercise has not proven effective in randomized controlled trials. It remains to be determined whether resistance training is effective in reducing hot flushes and improves quality of life in symptomatic postmenopausal women. The aim of this study is to investigate the effect of standardized resistance training on hot flushes and other health parameters in postmenopausal women.Study designThis is an open, parallel-group, randomized controlled intervention study conducted in Linköping, Sweden. Sixty symptomatic and sedentary postmenopausal women with a mean of at least four moderate to severe hot flushes per day or 28 per week will be randomized to an exercise intervention or unchanged physical activity (control group). The intervention consists of 15 weeks of standardized resistance training performed three times a week under supervision of a physiotherapist.Main outcome measuresThe primary outcome is hot flush frequency assessed by self-reported hot flush diaries, and the difference in change from baseline to week 15 will be compared between the intervention group and the control group.ConclusionThe intention is that this trial will contribute to the evidence base regarding effective treatment for hot flushes.     

The relation of physiological changes to subjective symptoms in postmenopausal women with and without hot flushes

This study was designed to fully correlate the temporal relationship between augmented digital perfusion, (vasodilatation) and hot flushes, peripheral temperature, plasma luteinizing hormone, (LH) epinephrine and norepinephrine. Plasma samples were measured every 3 min for 2–4 h, in 5 symptomatic women before and after estrogen replacement and in 3 asymptomatic post-menopausal women. In all 5 symptomatic women the augmented digital perfusion occurred at a mean (±SEM) of 1.5±0.2 min before the initiation of the flush, at least 3 min before the initial rise in temperature and 9 min before the LH rise. There was a significant (P < 0.05) rise in epinephrine but not norepinephrine at 3 and 6 min after the initiation of augmented digital perfusion. Although subjective improvement occurred in all 3 women receiving estrogen, all measured parameters disappeared in only 1 subject and the 2 others continued having augmented digital perfusion, flushes, and temperature vasomotor changes although the related LH increase was absent. Surprisingly, asymptomatic women who never received estrogens also demonstrated similar augmented digital perfusion and temperature changes, but failed to show the LH related rise, as observed in women with short-term estrogen treatment. In conclusion, these results demonstrate that augmented digital perfusion consistently precedes the hot flush, the rise in temperature and plasma LH in symptomatic post-menopausal women. The increase in epinephrine may be a homeostatic mechanism to compensate for the peripheral vasodilatation. The finding that augmented digital perfusion and temperature changes also occur in asymptomatic post-menopausal women indicates that objective changes are more specific and reliable indicators of vasomotor instability than the subjective sensation of hot flushes.     

Acupuncture for postmenopausal hot flashes

OBJECTIVE: To determine whether individually tailored acupuncture is an effective treatment option for reducing postmenopausal hot flashes and improving quality of life. METHODS: In a randomized, placebo-controlled pilot study, 29 postmenopausal participants averaging at least seven moderate to severe hot flashes per 24h, with a baseline estradiol concentration of less than 50 pg/mL and a normal TSH level, were randomized to receive 7 weeks (nine treatment sessions) of either active acupuncture or placebo acupuncture (placebo needles that did not penetrate the skin at sham acupuncture points). Participants recorded hot flashes in logs that were reported daily. Global indices of the severity and frequency of hot flashes were derived from the participants' daily logs. RESULTS: Participants receiving the active treatment had a greater reduction in hot flash severity (24.5+/-30.7%) compared to those receiving placebo (4.4+/-17.1%, P=0.042). Within group repeated measures analyses of variance revealed a significant reduction in hot flash severity in the active (P=0.042), but not in the placebo treatment group (P=0.15). Although there was no significant group difference in the reduction of hot flash frequency between the active (42.4+/-32.2%) and placebo groups (32.0+/-26.5%; P>or=0.352), within group repeated measures analyses of variance revealed that the reduction was statistically significant in both groups (P相似文献   

低体温与心率变异性和血压变异性的关系

目的: 研究低体温与自主神经功能变化的关系。方法: 采用体表物理降温法逐步降低直肠温度,直肠温度变化范围为19-37 ℃。分别记录不同直肠温度下大鼠动态心电和血压信号。应用心率变异性和血压变异性分析系统评价低体温对心率变异性和收缩压变异性的影响。结果: 心率变异分析表明，直肠温度下降到29 ℃以下,R-R间期均延长（P<0.01）,提示心率明显降低;当直肠温度下降到19-21 ℃时,心率变异归一化低频功率降低（P<0.05）和归一化高频功率增加（P<0.05），而且自主神经的平衡向心迷走神经张力增强的方向发生了转移（P<0.05）。血压变异性分析表明，体温下降到31℃时与呼吸有关的归一化高频功率开始增加（P<0.01）；直肠温度下降到29 ℃以下(除27 ℃外),与呼吸有关的归一化高频功率增加（P<0.05或P<0.01），同时自主神经的平衡也发生了改变（P<0.05）。结论： 随着体温的降低，心血管迷走神经活性增加，自主神经的平衡向迷走神经张力增强的方向转移。低体温对血压变异性的影响敏感于心率变异性。     

Identification of low and high frequency ranges for heart rate variability and blood pressure variability analyses using pharmacological autonomic blockade with atropine and propranolol in swine

Understanding autonomic nervous system functioning, which mediates behavioral and physiological responses to stress, offers great potential for assessing farm animal stress and welfare. Evaluation of heart rate variability (HRV) and blood pressure variability (BPV), using time and frequency domain analyses may provide a sensitive and reliable measure of affective states and stress-mediated changes in sympathetic and parasympathetic tones. The aim of this research was to define low (LF) and high frequency (HF) power spectral ranges using pharmacological autonomic blockade, and to examine HRV and BPV parameter changes in response to atropine and propranolol in swine. Ten, 13-week old, barrows (n = 6) and gilts (n = 4) underwent surgery to place an intra-cardiac electrode and a blood pressure catheter attached to a biotelemetric transmitter; pigs had a 3-week recovery period prior to data collection. Each pig was subjected to administration of 4 intravenous (i.v.) drug treatments: a control treatment, 3 mL of saline, and 3 blockade treatments; 0.1 mg/kg of atropine, 1.0 mg/kg of propranolol, and .1 mg/kg of atropine together with 1.0 mg/kg of propranolol. All treatments were delivered by injection in the jugular vein with a minimum of 48 h between individual treatments. Behavior, ECG and blood pressure data were recorded continuously for a total of 1 h, from 30 min pre-injection to 30 min post-injection. For data analyses, two 512-beat intervals were selected for each treatment while the pig was lying and inactive. The first interval was selected from the pre-injection period (baseline), and the second was selected between 10 and 30 min post-injection. Time and frequency domain (power spectral density) analyses were performed on each data interval. Subsequent, LF and HF bands from the power spectral densities were defined based on general linear and regression analyses. The HRV and BPV were computed with a covariate (baseline) factorial analysis of treatment by sex interaction, and day of injection, with mixed models and Tukey's post-hoc tests. The best-fit range for LF was 0.0-0.09 Hz, and HF was 0.09-2.0 Hz (r²: 0.41 and 0.43, respectively). Propranolol and saline injections led to a greater overall total power and overall higher inter-beat interval, HF and LF power. Atropine led to a dominant sympathovagal balance of the cardiac activity in pigs. In addition, atropine led to an increase in LF power of both systolic and diastolic blood pressures in gilts suggesting vagal tone mediation of BPV. The understanding of autonomic regulation of HRV and BPV in domestic swine facilitates our ability to detect and quantify stress responses, and broadens its application in assessing farm animal welfare.     

Autonomic function and change in insulin for exercising postmenopausal women

Purpose

Obesity, physical inactivity and altered estrogen metabolism play an integrated role contributing to the disease risk profiles of postmenopausal women. These same risk factors also affect modulation of the autonomic nervous system (ANS).

Methods

We examined 332 postmenopausal, overweight, previously sedentary women (mean ± SD; age, 57.6 ± 6.3 years; weight, 84.3 ± 11.9 kg; BMI, 31.7 ± 3.7 kg/m²) participating in a 6-month, moderate intensity, aerobic exercise training intervention to determine the relationship between heart rate variability (HRV) derived autonomic function and fasting insulin. We analyzed quartiles of change in time and frequency domain indices of ANS activity and changes in insulin for between and within group differences using ANCOVA and Tukey post hoc tests adjusted for age, ethnicity, randomization group, change in fitness, and change in weight.

Results

We observed at baseline that insulin was positively correlated with body anthropometry (body weight, r² = 0.34; BMI, r² = 0.39; waist circumference, r² = 0.29; all, P < 0.001), and inversely associated with rMSSD (r² = −0.12) and SDNN (r² = −0.18; all, P < 0.01). After the intervention, changes in rMSSD (r² = −0.21, P < 0.002) and SDNN r² −0.19, P < 0.0001) were inversely correlated to insulin change. Further ANCOVA analysis revealed that rMSSD and SDNN were both significant (P < 0.0001); however, only rMSSD exhibited a step-wise pattern of improvement when quartiles of rMSSD were compared to corresponding insulin reductions: Q1 (referent group, 8.41 ± 3.2 uIU/ml), Q2 (−3.30 ± −3.2 uIU/ml), Q3 (−5.66 ± −3.2 uIU/ml; P < 0.02), and Q4 (−9.60 ± −3.2 uIU/ml; P < 0.006).

Conclusion

Our study shows that changes in autonomic function are associated with changes in insulin and that exercise training may influence this relationship in postmenopausal women.     

Differential factors associated with hot flashes in Chinese perimenopausal and postmenopausal women

Objective

This study investigated factors associated with hot flashes in Chinese perimenopausal and postmenopausal women.

Methods

This cross-sectional study recruited Chinese women aged 40–60 years who were perimenopausal or postmenopausal and examined factors associated with hot flashes. Participants completed a questionnaire detailing demographic information, characteristics of menstruation, reproductive history, use of hormone replacement therapy or oral contraceptives, personal lifestyle factors (exercise, multivitamin use, soy products use, diet), and symptoms of hot flashes. Height, weight, blood pressure, and waist and hip circumference were also measured.

Results

A total of 1399 participants (817 perimenopausal women and 582 postmenopausal women) completed the study. In perimenopausal women, college or higher education decreased the prevalence of hot flashes (odds ratio (OR) 0.63; 95% confidence interval (CI) 0.46–0.86). In postmenopausal women, an omnivorous diet decreased the prevalence of hot flashes (OR 0.38; 95% CI 0.17–0.85). Strenuous exercise (≥3 times a week) increased the prevalence of hot flashes (OR 1.41; 95% CI 1.08–1.83) in perimenopausal women.

Conclusions

It is possible that modifiable risk factors for hot flashes exist in Chinese perimenopausal and postmenopausal women. Future studies with larger populations are needed to confirm these findings.     

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.     

Assessment of phasic work stress using autonomic indices

The present paper concerns the assessment of phasic work stress using autonomic indices such as skin temperature, respiratory measures, and heart rate, blood pressure, and their variabilities. A physiological model of the autonomic regulation of the cardiovascular and respiratory systems is also introduced in order to simulate and interpret the changes in these indices. Two experiments were conducted to investigate high tension and monotony as two types of mental work stress. A tracking task was used to induce high-tension work stress with and without an instruction intended to induce additional emotional stress. The same tracking task was repeated 12 times to simulate monotonous work stress. Fifty healthy adults participated in each experiment. Many physiological measures showed task-dependent changes in the high-tension experiment and at the beginning of the monotonous stress condition. These changes were explained by sympathetic activation, parasympathetic withdrawal, and respiratory rate activation. An additional drop in skin temperature and an additional HR increase were caused by the stressful instruction, which may reflect an emotional strain and can be explained by sympathetic activation. Furthermore, the mid-frequency component (approx. 0.1 Hz) of respiration and respiratory instability showed an obvious increase during the course of the monotonous stress experiment, which may reflect boredom and disgust. It was concluded that multidimensional recordings of autonomic measures that can be obtained during work without extra load on the worker would be helpful to assess different types of phasic work stress. The proposed model was further shown to be able to detect periods of stress in a complex work environment.     

Modulation of heart rate variability by estrogen in young women undergoing induction of ovulation

Estrogens are involved in the modulation of the cardiovascular system, yet their effects in young women remains largely unknown. Women who undergo ovulation induction treatments attain extremely high estrogen concentrations during a very short time period. The aim of the present study was to evaluate the effects of an acute increase in estrogens on the autonomic nervous system modulation of heart rate variability (HRV). A total of 27 women undergoing ovulation induction and 14 normally menstruating women were prospectively studied. HRV was assessed during nadir and peak estrogen using time domain and power spectral density analyses. A significant increase in high-frequency spectral power (243 ± 77 vs. 188 ± 73 ms²/Hz, P < 0.01) with a significant decrease in the ratio of low to high-frequency power was observed during estrogen peak in women undergoing induction of ovulation. The acute increase in estrogen in women undergoing ovulation induction was associated with vagal activation and altered sympathovagal balance.     

Relations between psychometric profiles and cardiovascular autonomic regulation in physical education students

This study was designed to investigate physical education (PE) students the link between mood disturbances, caused by psychological or physical stressors associated with studying, and the autonomic nervous system modifications. PE students completed the profile of mood state (POMS) questionnaire at the end of the university year. Heart rate variability (HRV) was then measured during a head-up tilt test (HUT) in those with the highest and lowest total mood disturbance (TMD) scores on three successive POMS. Among the 218 students who completed the POMS (85 female and 137 male), 65 had high TMD scores, suggesting mood disturbances and fatigue. The final sample included 12 subjects in the potentially overtrained (POT) group and 16 subjects in the control (CTL) group. A greater decrease of two indices of the autonomic system (SD1 and RMSSD) was observed during the HUT in the POT than in the CTL group (P < 0.05). The depression (Dep) and vigor (Vig) subscales of POMS were correlated with several HRV indices. More specifically, in the POT group, the Vig score was correlated with autonomous activity in the supine position, and the Dep score with percentages of change of sympatho-vagal activity during the HUT. This suggests that (1) POT students could present a weaker autonomic response to HUT, (2) Dep and Vig subscales of the POMS questionnaire may indicate autonomic dysregulations.     

Beliefs regarding menopausal hot flushes among climacteric women as assessed with the Hot Flush Beliefs Scale

Background

Hot flushes (HFs) and night sweats are frequent complaints among both peri- and postmenopausal women. Beliefs regarding these complaints may vary from one population to another.

Objective

To assess HF beliefs and factors related to negative beliefs in a climacteric Hispanic population using the Hot Flush Beliefs Scale (HFBS).

Methods

A total of 1154 healthy women (40–59 years) were assessed with the Menopause Rating Scale (MRS), those presenting HFs were requested to fill out the HFBS and a questionnaire containing socio-demographic data (female and partner).

Results

A total of 646 presented HFs (56%) graded according to the first item of the MRS as mild (28.6%), moderate (33.2%), severe (29.1%) and very severe (9.1%). Mean age of these women was 49.5 ± 5.2 years, with 51.9% having 12 or less years of education, 61.5% being postmenopausal and 47.2% living in high altitude. At the moment of the survey 13.9% were on HT, 12.8% on phytoestrogens and 7.1% on psychotropic drugs. Women strongly disagreed in more negatively oriented items of those contained in subscale one (beliefs about self in social context). Contrary to this, women strongly agreed in more negative oriented items contained in subscale two which assesses beliefs about coping with HFs. Women presenting with severe–very severe HFs displayed higher HFBS total and subscale scores indicating a more negative belief regarding HFs. Logistic regression analysis determined that HF severity was related to higher HFBS scores for the total and subscales one and two. Current smoking, higher parity, lower female education, female psychiatric consultation, time since menopause and partner unhealthiness and alcohol consumption were also related to higher HFBS scorings. Postmenopausal status and church attendance were related to lower scores.

Conclusion

In this mid-aged Ecuadorian female series negative beliefs regarding HFs were related to the severity of HFs and individual female or partner characteristics. Data provided from clinical research using this tool, alone or in combination with other tests, is warranted.     

Cardiac autonomic dysfunction in rats chronically treated with anabolic steroid

To date no published data exist regarding the effects of chronic high-dose anabolic-androgenic steroid administration on tonic cardiac autonomic control. The aim of this study was to evaluate, by power spectral analysis of heart rate variability (HRV), the effects of chronic treatment with supraphysiological doses of nandrolone decanoate (DECA) on tonic cardiac autonomic regulation in sedentary rats. Male Wistar rats were treated weekly with 10 mg kg⁻¹ of DECA (n=7) or vehicle (CONTROL, n=7) for 10 weeks. At the 8th week of treatment, electrocardiogram was recorded in the conscious state, for time- and frequency-domain HRV analysis. Parasympathetic indexes were reduced in DECA group: high-frequency power (CONTROL=11.1±3.0 ms2 vs. DECA=3.8±0.6 ms2, P<0.05), RMSSD (CONTROL=5.9±0.9 ms vs. DECA 3.5±0.3 ms; P<0.05) and pNN5 (CONTROL=31.5±7.5 ms vs. DECA=13.2±2.6 ms; P<0.05). The sympathetic index LF/HF tended to be higher in DECA group (CONTROL=0.65±0.15 vs. DECA=1.17±0.26, P=0.0546). In conclusion, chronic treatment with DECA, in rats, impairs tonic cardiac autonomic regulation, which may provide a key mechanism for anabolic steroid-induced arrhythmia and sudden cardiac death.     

Autonomic activity and baroreflex sensitivity in patients submitted to carotid stenting

Arterial baroreflex and cardiac autonomic control play important roles in hemodynamic instability after carotid artery stenting (CAS). Spontaneous baroreflex sensitivity (BRS), heart rate variability (HRV) and blood pressure variability (BPV) are established tools for the assessment of arterial baroreflex and cardiac autonomic activity. Aim of the study was to evaluate cardiac autonomic activity (by means of HRV, BPV and BRS) after CAS and to explore the impact of internal carotid artery stenosis on BRS changes after CAS. 37 patients (68±10.45 years) with internal carotid stenosis underwent CAS. HRV, BPV and BRS were measured in all subjects before and at 1 and 72h after CAS. ANOVA was performed to compare BRS, HRV and BPV parameters before and after CAS. Spearman analysis was performed to determine a possible correlation between carotid stenosis degree (or carotid plaque diameter) and BRS changes (ΔBRS). LF/HF (index of sympatho-vagal balance) decreased during postoperative period, in comparison with baseline (2.32±1.70 vs 1.65±1.40, p<0.05). There was a significant negative correlation between carotid stenosis degree and ΔBRS (r=-0.35, p=0.03) and between carotid plaques thickness and ΔBRS (r=-0.36, p=0.02). CAS procedure may cause an alteration of carotid wall mechanical properties, increasing baroreflex sensitivity. BRS does not increase in all the patients, because arterial wall damage and nerve destruction determined by atherosclerotic plaque may reduce ΔBRS.     

A comparative scale of autonomic function with age through the tone-entropy analysis on heart period variation

Tremendous numbers of heart rate variability studies have aimed to elucidate age-associated alterations of autonomic function in the past decades. However, the studies, far from clarifying ageing mechanisms, fell into confusion by a lack of common scales. The purpose of this study is to show a possibility to establish a comparative scale of autonomic function through a method, tone-entropy (T-E) analysis on heart period variation, whose validity has been already examined on typical physiological cases (Oida et al. in J Appl Physiol 82:1794–1801, 1997; Oida et al. in J Gerontol 54A:M219–M224, 1999a; Oida et al. in Acta Physiol Scand 165:129–134, 1999b; Oida et al. in Acta Physiol Scand 165:421–422, 1999c; Amano et al. in Eur J Appl Physiol 94:602–610, 2005). In this study, 276 subjects from teens to seventies were examined at rest by T-E analysis together with conventional time and frequency domain analyses. The tone (negativity represents vagal predominance) became significantly high [−0.174 ± 0.026 (teens) to −0.024 ± 0.004 (seventies), P < 0.05 for one-way ANOVA], and the entropy (total autonomic activity), significantly low [4.40 ± 0.12 (teens) to 2.90 ± 0.09 bit (seventies), P < 0.05] with advancing age. The result, plotted in 2-D T-E space, showed that the ageing traced a curvi-linear relation from right-bottom to left-top, and was consistent with previously studied typical physiological cases. The conventional analyses showed almost the same autonomic reduction as T-E did, but failed in detecting delicate alteration of autonomic balance. The results, showing that autonomic activity reduced in both pathways impairing vagal predominance significantly with ageing, suggested a possibility to assess autonomic function in 2-D T-E space in a comparative way.     

Consistency of heart rate and sympathovagal reactivity across different autonomic contexts

Theories that psychophysiological reactivity constitutes a risk factor for coronary artery disease assume that reactivity is a consistent individual characteristic. We tested this assumption by measuring reactivity to three psychologically challenging tasks performed by 22 healthy subjects across different autonomic contexts produced by positional change. Dependent variables included heart rate (HR), low-frequency (LF; 0.04–0.15 Hz) and high-frequency (HF; 0.15–0.50Hz) heart period variability, and the LF/HF ratio. HR (r= .44, p < .05) and LF/HF ratio (r= .48, p= .03) reactivity were modestly correlated across the different autonomic contexts, but HF and LF power reactivity were not. These findings suggest that HR reactivity to psychological challenge is a modestly consistent characteristic of individuals, despite differences in autonomic context. Although the same is true of cardiac sympathovagal balance, reactivity of HF and LF power were less consistent.