Effects of bright light exposure on heart rate variability during sleep in young women.

To investigate the effects of evening bright light on the autonomic nervous system, heart rate variability (HRV) during sleep was analyzed in dim light (DL) and bright light (BL) conditions. We recorded polysomnography in nine healthy young women aged 20-21 years. Time series of % delta power was calculated in the 0.49-2.20 Hz band. Heart rate variability was analyzed from a 10-min segment of slow wave sleep. The low- to high-frequency ratio and the low-frequency component decreased significantly in the BL conditions compared with the DL conditions. However, the power of the high-frequency component did not change in the two conditions. These results indicate that evening BL affects the autonomic nervous system during slow wave sleep.     

Autonomic nervous function after evening bright light therapy: spectral analysis of heart rate variability

In order to investigate the effects of 5000 lx evening bright light on autonomic nervous function, a spectral analysis was used to assess heart rate variability in consecutive 5-min epochs just after 60 min of bright light therapy was given to 12 young women (range: 20-21 years of age). The study revealed that a low frequency band (LF) increased in bright light conditions (BL) in comparison with controlled conditions (CL). High frequency band (HF), LF:HF ratio and the coefficient of variance (CV R-R) were not significantly different between the two conditions. These results indicate that 5000 lx evening bright light may affect sympathetic nervous system activity in healthy women.     

Effects of caffeine on heart rate and QT variability during sleep

Administration of caffeine in the evening produces poor sleep. Patients with insomnia have characteristic electrocardiogram (ECG) changes, including increased heart rate (HR), increased sympathetic activity, and decreased parasympathetic activity. Fifteen young adult normal subjects slept in the laboratory for several nights prior to randomization into a caffeine protocol where subjects received caffeine 400 mg 30 min prior to one night of sleep and placebo randomly prior to another night. ECG was sampled at a rate of 500 Hz and recorded onto a PC. Data samples of 256-s periods of the ECG trace were taken from wake (before sleep), stage II, and REM for placebo and caffeine conditions. A peak detection algorithm was used to identify the R-R intervals (in milliseconds) from the ECG. A common QT variability algorithm was used to find the QT interval for each beat using the time-stretch model. The powers for HR and QT series were integrated in the bands of LF (low frequency: 0.04-0.15 Hz) and HF (high frequency: 0.15-0.5 Hz) bands. There was a significant caffeine by sleep stage interaction for LF/HF ratios (F = 4.0; df = 2, 18; P = .04). LF/HF ratios were significantly higher during REM following caffeine administration. There was also a significant caffeine by sleep stage interaction for QTvi (QT variability normalized for mean QT interval divided by HR variability normalized for mean HR; F = 5.6; df = 2, 12; P = .02). QTvi was also significantly higher during REM following caffeine administration. The higher LF/HF ratios and QTvi during REM are most likely due to the sympathetic effects of caffeine. These findings suggest that excessive caffeine intake may result in adverse cardiovascular events in vulnerable subjects.     

Human heart rate variability and sleep stages

With the aim of better understanding the dynamic changes in sympatho-vagal tone occurring during the night, human heart rate variability (HRV) during the various sleep stages was evaluated by means of autoregressive spectral analysis.Each recording consisted of an electroencephalogram, an electrooculogram, and electromyogram, an electrocardiogram, and a spirometry trace. All of the data were sampled and stored in digital form.Sleep was analysed visually, but HRV was analysed off-line by means of original software using Burg's algorithm to calculate the LF/HF ratio (LF: 0.04–0.12 Hz; HF: 0.15–0.35 Hz) for each sleep stage.Seven healthy subjects (four males; mean age 35 years) were enrolled in the study.Our findings show a progressive and significant reduction in the LF/HF ratio through sleep stages S1–S4, as a result of an increase in the HF component; this indicates the prevalence of parasympathetic activity during slow-wave sleep. During wakefulness, S1 and REM, the LF/HF values were similar and close to 1.

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Sommario Allo scopo di comprendere meglio le modificazioni del tono del sistema nervoso autonomo durante la notte, è stata valutata la variabilità del ritmo cardiaco (HRV) negli stadi del sonno, impiegando una metodica autoregressiva di analisi spettrale.Ciascuna registrazione consisteva di elettroencefalogramma, elettro-oculogramma, elettromiografia, spirometria ed elettrocardiogramma, campionati e registrati in forma digitale.L'ipnogramma è stato ottenuto ispettivamente, mentre l'analisi dell'HRV è stata eseguita con un software dedicato, utilizzando l'algoritmo di Burg e calcolando il rapporto LF/HF (LF: 0.04–0.12 Hz; HF: 0.15–0.35 Hz) per ciascuno stadio del sonno.Sono stati arruolati nello studio 7 soggetti sani (4 maschi, età media 35 anni). I nostri risultati mostrano una progressiva e significativa diminuzione di LF/HF dallo stadio 1 al 4, imputabile ad un aumento del tono del parasimpatico (aumento della componente HF), mentre il valore del rapporto durante veglia, REM e fase 1 è risultato simile (circa 1).

     

Assessment of the primary effect of aging on heart rate variability in humans

Beat-to-beat heart rate variability (HRV), reflecting cardiac autonomic control mechanisms, is known to change with age. However, the degree to which this change is mediated by aging per se or by physiologic changes characteristic of normative aging is still unclear. This study was designed to examine the association of aerobic fitness, body habitus or obesity, and blood pressure with age-related changes in HRV. Resting HRV data was recorded from 373 healthy subjects (124 men, 249 women; are range, 16–69 y) and analyzed by coarse-graining spectral analysis to decompose the total spectral power into its harmonic and fractal components. The low- and high-frequency (LF, 0.0–0.15 Hz; HF, >0.15 Hz) harmonic components were calculated from the former, whereas the latter was used to calculate the integrated power (FR) and the spectral exponent , which were, in turn, used to evaluate the overall complexity of HRV. Factor analysis was performed to test whether potentially age-related changes in the components of HRV might be observed secondarily through other variables affecting HRV. Significant (p<0.05) age-related changes in the harmonic (HF and LF) and fractal (FR and ) components of HRV were generally consistent with those described in the literature. In addition, factor analysis showed that there was a unique common factor that primarily explained correlations among age, HF, and (p<0.05) without the contributions from LF, FR, aerobic fitness, body habitus or obesity, and blood pressure. It was concluded that, in this population-based sample, age-related changes in HF and , both of which reflect vagal modulation of heart rate, were primarily mediated by aging per se and not by physiologic changes characteristic of normative aging.     

Interval training in elderly men increases both heart rate variability and baroreflex activity

Abstract Aims Autonomic nervous system activity decreases continuously with age and appears to be a powerful predictor of disease and death. Attempts are thus made to reactivate autonomic drive with the intent of improving health. Methods We assessed maximal oxygen consumption (VO_2max), auto- nomic nervous system activity by heart rate variability (HRV) analysis and spontaneous cardiac baroreflex activity (SBR) in eleven elderly men (73.5±4.2 years) before and after a 14-week program of intensive cycloergometer interval training. The standard HRV indices were calculated using time domain (mean RR, PNN50, RMSSD, SDNN, SDANN and SDNNIDX), and Fourier transform (total power, ULF,VLF, LF, LFnu, HF, HFnu and LF/HF) analyses of 24-hour, daytime and nighttime Holter recordings. The SBR was calculated from 15-minute recordings of spontaneous blood pressure and RR interval variations using the sequence (slope, slSBR) and cross-spectral (SBR_HF and SBR_LF) methods. Results After the training period,VO_2max increased by 18.6 % (26.8±4.4 to 31.8±5.2 ml · kg^–1 · min^–1, p<0.01). The nocturnal parasympathetic indices of HRV increased (PNN50: 3.05±2.21 to 5.00±2.87%, RMSSD: 29.1±7.6 to 38.8±10.9 ms, HF: 117±54 to 194±116 ms²/Hz, all p<0.05) as did the SBR indices (slSBR: 7.0±1.8 to 9.8±2.1 ms·mmHg^–1, p<0.01; SBR_HF: 6.9±2.2 to 10.5±3.7 ms ·mmHg^–1, p<0.05; SBR_LF: 5.3±2.3 to 6.9±3.1 ms ·mmHg^–1, p=0.22). Conclusion Intensive endurance training in elderly men enhanced parasympathetic parameters of HRV and, interestingly, of SBR. Physiological mechanisms and long-term clinical effects on health status should be further investigated.     

Stability over time of short-term heart rate variability

Abstract Heart rate variability (HRV) is a widely used method to assess cardiac autonomic control. However, the reproducibility of especially short-term HRV has not been properly evaluated. Therefore, we assessed the stability of short-term HRV over a three to four month period. We had seven consecutive electrocardiographic (ECG) recordings from 89 subjects with stable coronary artery disease obtained during a large multicenter study. The HRV assessments were performed from these 40-minute ECG-recordings simulating normal daily activities, i. e., recordings consisting of 5 to 10 minute periods of rest, paced breathing, standing, submaximal exercise and recovery. Both time and frequency domain HRV analyses were conducted from the whole 40-minute recordings and from the 5-minute periods of rest and paced breathing. The coefficient of variation (CV) varied between 5.1–16.7% for the 40-minute and 6.0–37.1% for the 5-minute time domain and 4.4–11.0 % for the 40-minute and 7.2–16.5 % for the 5-minute frequency domain measurements. The mean of the RR intervals and the total power showed the highest stability over time. The most unstable measure was the standard deviation of all NN intervals (SDNN). In conclusion, most short-term HRV measures were highly stable over time indicating low physiological variation. However, the SDNN showed large variability in consecutive recordings. Sources of support: EU Environment and Climate Research Program, contract NV4-CT97–0568.     

Differences in heart rate variability between depressed and non-depressed elderly

OBJECTIVE: To determine whether older primary care patients with a Major Depressive Disorder (MDD) have lower heart rate variability (HRV) compared to non-depressed patients. HRV is a measure of cardiac autonomic functioning. METHOD: A cross-sectional comparison of 136 elderly persons with MDD and 136 non-depressed controls (matched for age and gender) recruited in family practices in the Netherlands. Depression was determined according to the DSM-IV criteria using the PRIME-MD. HRV was measured with an electrocardiogram (ECG) during a 5-minute supine rest. RESULTS: Multivariate analyses showed statistically significant decrease in HRV in MDD patients compared with controls. CONCLUSION: Older primary care patients with MDD have a reduced HRV. This may explain why depression is a risk factor for cardiovascular disease and mortality.     

Carotid atherosclerosis and heart rate variability in ischemic stroke

The significant association between heart rate variability (HRV) and the outcomes of stroke has led to a particular interest in alterations of HRV in stroke patients. To date, several clinical variables have been associated with alterations of HRV in stroke patients. The present study adds the new information that carotid atherosclerosis may affect HRV alterations in stroke patients.     

Correlation between electroencephalography and heart rate variability during sleep

It is known that autonomic nervous activities change in correspondence with sleep stages. However, the characteristics of continuous fluctuations in nocturnal autonomic nerve tone have not been clarified in detail. The study aimed to determine the possible correlation between the electroencephalogram (EEG) and autonomic nervous activities, and to clarify in detail the nocturnal fluctuations in autonomic nerve activities. Overnight EEGs and electrocardiograms of seven healthy males were obtained. These EEGs were analyzed by fast Fourier transformation algorithm to extract delta, sigma and beta power. Heart rate and heart rate variability (HRV) were calculated in consecutive 5-min epochs. The HRV indices of low frequency (LF), high frequency (HF) and LF/HF ratio were calculated from the spectral analysis of R-R intervals. The sleep stages were manually scored according to Rechtschaffen and Kales' criteria. Low frequency and LF/HF were significantly lower during non-rapid eye movement (NREM) than REM, and were lower in stages 3 and 4 than in stages 1 and 2. Furthermore, delta EEG showed inverse correlations with LF (r = - 0.44, P < 0.001) and LF/HF (r = - 0.41, P < 0.001). In contrast, HF differed neither between REM and NREM nor among NREM sleep stages. Detailed analysis revealed that correlation was evident from the first to third NREM, but not in the fourth and fifth NREM. Delta EEG power showed negative correlations with LF and LF/HF, suggesting that sympathetic nervous activities continuously fluctuate in accordance with sleep deepening and lightening.     

躯体化症状为主的抑郁症心率变异性对照研究

目的：探讨躯体化症状为主的抑郁症患者自主神经系统的特点及抑郁症躯体化表现的发生机制。方法：对30例躯体化症状为主的患者（A组）和30例情绪症状为主的患者（B组）及30例健康正常者（C组）分别进行汉密尔顿抑郁量表（HAMD）和汉密尔顿焦虑量表（HAMA）评定及短时（10min）心率变异性（HRV）分析。结果：A、B、C3组HRV分析指标RR间期标准差（SDNN）分别为（50.84±19.92）ms、（94.93±28.80）ms、（105.77±22.05）ms,A组显著低于C组（t=5.68,P〈0.01）,较B组低（t=3.73,P〈0.05）;3组LF/HF分别为（6.26±2.11）ms、（3.51±2.44）ms、（1.80±1.07）ms,A组显著高于C组（t=6.35,P〈0.01）,较B组高（t=2.50,P〈0.05）;A组HAMD评分（28.30±6.26）分高于B组（24.35±6.69）分,二者差异有显著性（t=3.14,P〈0.05）;A组HAMA评分（22.70±4.92）分显著高于B组（13.05±4.71）分,二者差异有显著性（t=6.17,P〈0.01）;HAMD焦虑/躯体化因子分与HRV指标SDNN、LF、HF、VLF和LF/HF均呈中度相关（r分别为0.49、0.61、0.58、0.50、0.63）（P〈0.05或P〈0.01）。结论：躯体化症状表现为主的抑郁症患者多伴有焦虑,自主神经功能紊乱。     

Heart rate variability in a case of pheochromocytoma

Indices of heart rate variability (HRV) reflect cardiac autonomic tone and may be markedly affected by pheochromocytoma. The effect of pheochromocytoma on HRV was determined by Holter monitoring before diagnosis, under pre-operative -blockade and 5 and 19 months after surgery in a 40 year-old female. Mean heart rates, although higher under -blockade, were unchanged by surgery but indices of HRV reflecting both short term (vagally mediated) and longer term (mediated by vagal, sympathetic and other influences) rhythms were diminished under -blockade and post-surgery. High frequency power (0.15–0.40 Hz), an index of vagal tone, declined from 512 ms² pre-diagnosis to 220 ms² under -blockade to just over 100 ms² post-surgery. Low frequency power (0.04–0.15 Hz), a measure reflecting both vagal and sympathetic tone, declined from 409 ms² pre-diagnosis to 186 ms² under -blockade and was just over 200 ms² post-surgery. SDNN, the standard deviation of normal-to-normal interbeat intervals over 24 hours, declined from 118 ms pre-diagnosis to just over 70 ms both under -blockade and post-surgery. The ratio of low frequency to high frequency power (LF/HF ratio) increased to 0.84 under -blockade, and doubled after surgery (0.79; before, 2.05; after). These changes in HRV may provide insights into the effects of endogenous catecholamines and intrinsic counter-regulatory autonomic mechanisms on HRV.     

Impaired heart rate variability in euthymic bipolar patients

Background:  Power spectral analysis of heart rate variability (HRV) has recently been shown to be a reliable non-invasive test for quantitative assessment of the central sympathovagal interaction that modulates cardiovascular autonomic function.
Methods:  We studied 39 euthymic bipolar patients and 39 controls, matched for age and sex. A high-resolution electrocardiogram was obtained during complete rest. Spectral analysis of R–R intervals was performed by the fast Fourier transform algorithm.
Results:  Euthymic bipolar patients at rest are characterized by markedly low HRV, independent of specific drug treatments.
Conclusion:  While these results of autonomic stability in euthymic bipolar patients are counter-intuitive, the findings may be important in understanding pathophysiology of bipolar affective illness.     

The effects of acetylic salicylic acid on heart rate variability in healthy subjects

In this placebo controlled double blind cross over study multiple daily dosing with 500 mg acetylic salicylic acid did not influence heart rate variability in 16 healthy male volunteers aged 25 (22–28) years (median; range) to a relevant extent (p > 0.05). M. Siepmann and R. Rauh contributed equally to this work     

Decreased heart rate variability in amyotrophic lateral sclerosis

Autoregressive spectral analysis of heart rate variability (HRV) was performed in 29 patients with amyotrophic lateral sclerosis (ALS) and 33 age-matched healthy subjects to evaluate the involvement of the autonomic nervous system. HRV analysis provides a means to recognize low (LF) and high (HF) frequency components, respectively mediated by sympathetic and parasympathetic heart control. An increase in the mean heart rate at rest (P < 0.001), a decrease in standard deviation of R-R interval as well as in PNN50 (P < 0.001), and an increase in the LF/HF component ratio (P < 0.01) were found in the ALS patients, indicating a vagal–sympathetic imbalance. These alterations were not related to the clinical features and to the duration of the disease. Our results suggest a subclinical involvement of the autonomic nervous system in ALS, particularly affecting parasympathetic cardiovascular control. © John Wiley & Sons, Inc.     

Sevoflurane anesthesia decreases cardiac vagal activity and heart rate variability

We evaluated cardiac vagal activity during sevoflurane anesthesia in neurosurgical patients. Heart rate variability was determined by power spectral analysis and entropy with the patient awake and during sevoflurane anesthesia. High frequency power (0.15–0.50 Hz) and heart rate entropy decreased during sevoflurane and these effects were significantly correlated (r = 0.71 ± 0.12, P < 0.05). The results confirm that cardiac vagal activity was the primary determinant of heart rate variability, which was attenuated by sevoflurane.     

Relationship between frequency spectrum of heart rate variability and autonomic nervous activities during sleep in newborns

Introduction

We analyzed the frequency spectrum of two neonatal sleep stages, namely active sleep and quiet sleep, and the relationship between these sleep stages and autonomic nervous activity in 74 newborns and 16 adults as a comparison.

Development of an analysis system for 24-hour blood pressure and heart rate variability in the rat

Abstract We have developed a system to evaluate 24-h changes of heart rate (HR) and blood pressure variability (BPV) in free moving rat. As a sensor to monitor electrocardiogram, we used the telemetry system. Analog data were sent to an analog to digital converter directly. The data were digitized at a sampling frequency of 1250 Hz and digitally stored on a computer. RR-intervals (difference of successive RR in electrocardiogram) were calculated using custom designed programs. Circadian change of the blood pressure and heart rate variability were calculated. We suggest that the system is a powerful tool in the evaluation of circadian changes of hemodynamics and autonomic nervous function in free moving rats.