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Stress is a psychophysical condition that causes an impairment in athletes' performance by causing an increase in sympathetic activity and an autonomic imbalance. The current methods for the measurement of psychophysiological stress introduce the use of the heart rate variability as a useful index of the well-being of these people. The heart rate variability corresponds to the time intervals between consecutive heartbeats, such as an irregularity in the normal sinus heart rhythm whose variability is due to the control exercised by a complex system of mechanisms, including the respiratory control system, and provides information about the activity of the sympathetic and parasympathetic branches of the autonomic nervous system. This review aims at summarizing the promising results, despite small amount, of the recent literature on the efficacy of heart rate variability biofeedback on the autonomic imbalance and psychophysical well-being of athletes as well as cognitive and motor performance. [ABSTRACT FROM AUTHOR]

BACKGROUND: Non-ordinary states of consciousness induced by psychedelics can be accompanied by so-called peak experiences, characterized at the emotional level by their intensity and positive valence. These experiences are strong predictors of positive outcomes following psychedelic-assisted therapy, and it is therefore important to better understand their biology. Despite growing evidence that the autonomic nervous system (ANS) plays an important role in mediating emotional experiences, its involvement in the psychedelic experience is poorly understood. The aim of this study was to investigate to what extent changes in the relative influence of the sympathetic (SNS) and parasympathetic nervous systems (PNS) over cardiac activity may reflect the subjective experience induced by the short-acting psychedelic N,N-Dimethyltryptamine (DMT). METHODS: We derived measures of SNS and PNS activity from the electrocardiograms of 17 participants (11 males, mean age = 33.8 years, SD = 8.3) while they received either DMT or placebo. RESULTS: Results show that the joint influence of SNS and PNS (sympathovagal coactivation) over cardiac activity was positively related to participants ratings of Spiritual Experience and Insightfulness during the DMT experience, while also being related to improved well-being scores 2 weeks after the session. In addition, we found that the state of balance between the two ANS branches (sympathovagal balance) before DMT injection predicted scores of Insightfulness during the DMT experience, as well as subsequent sympathovagal coactivation. CONCLUSION: These findings demonstrate the involvement of the ANS in psychedelic-induced peak experiences and may pave the way to the development of biofeedback-based tools to enhance psychedelic therapy.

To obtain reference ranges for heart rate variability (HRV) parameters in healthy children, taking into account their gender and age. The study included the results of testing 22,468 children ranging 5.5–12.5 years of age. The data were grouped by age and gender. The analysis of HRV parameters was carried out according to the standards described in existing guidelines. It was based on a 5-min rhythmogram obtained from a standard 12-lead electrocardiogram (ECG). The following characteristics of the temporal and spectral analyses of HRV were studied: standard deviation of NN intervals (SDNN), power in the low-frequency band of the HRV spectrum (LF), low-frequency power as mean percentage of total power (TP) of HRV spectrum (LF%), power in the high-frequency band of the HRV spectrum (HF), high-frequency power as mean percentage of TP of HRV spectrum (HF%), power in the very-low-frequency band of HRV (VLF), and LF/HF ratio. The values of SDNN, LF, HF, HF% and TP increased with age, reaching a peak at 8 and 9 years of age. It is notable that the values of SDNN, LF and TP were significantly lower in girls in each age group. The values of LF% and LF/HF decreased with age, with a peak decrease at 8 and 9 years of age, followed by a moderate increase or stabilization. The values of LF% and LF/HF did not differ statistically significantly between boys and girls. The VLF parameter exhibited a clear trend of growth with age and had higher values in boys of each age group. The correlation between HRV and heart rate (HR) was statistically significant. The correlation graphs had similar curves in both gender groups and both age groups. The parameters of the total HRV, as well as the activity of the parasympathetic nervous system (PNS), exhibited similar growth trends with age, with a peak increase in their values at 8 and 9 years of age. HR, as well as the activity of the sympathetic nervous system (SNS), decreased with age. Gender differences also followed a consistent pattern: parameters characterizing the activity of the peripheral nervous system were significantly higher in boys than in girls across all age groups. [ABSTRACT FROM AUTHOR]

Background: The modulation of cardiac sympathovagal balance alters following acute resistance training (RT) sessions. Nevertheless, the precise influence of RT at varying load intensities on this physiological response remains to be fully elucidated. Therefore, the aim of this study was to compare the time course of recovery following low- (40%), moderate- (60%), and high- (80%) load-intensity RT protocols performed up to muscle repetition failure in resistance-trained men. Method: Sixteen young, resistance-trained men (mean age: 21.6 ± 2.5 years, mean height: 175.7 ± 8.9 cm, mean weight: 77.1 ± 11.3 kg) participated in a randomized crossover experimental design involving three sessions, each taken to the point of muscle failure. These sessions were characterized by different load intensities: low (40% of 1-repetition maximum, 1RM), moderate (60% of 1RM), and high (80% of 1RM). The exercise regimen comprised four exercises—back squat (BS), bench press (BnP), barbell row (BR), and shoulder press (SP)—with each exercise consisting of three sets. Throughout each session, heart rate variability (HRV) and blood pressure (BP) parameters were assessed both pre-exercise and during a 40 min post-exercise period, segmented into 10 min intervals for stabilization. Statistical analysis involved the use of a repeated measures ANOVA. Results: It was observed that the 40% and 60% RT sessions resulted in a significantly higher root mean square of successive R-R intervals (RMSSD) value compared to the 80% RT session in the post-exercise recovery process in 30 min (respectively, p = 0.025; p = 0.028) and 40 min (respectively, p = 0.031; p = 0.046), while the 40% and 60% RT sessions produced similar responses. The 40% RT session was significantly higher in the high frequency (HF) value post-exercise in 40 min compared to the 80% RT session (p = 0.045). Conclusions: Our findings suggest that engaging in resistance training (RT) sessions to muscle failure at an intensity of 80% induces acute increases in sympathetic activity, potentially leading to elevated cardiovascular stress. For individuals with normal blood pressure, it is advisable to opt for lighter loads and higher repetition volumes when prescribing RT, as heavier-load RT may carry an increased risk of cardiac-related factors. [ABSTRACT FROM AUTHOR]

Introduction: Individuals with prehypertension are at an increased risk of developing hypertension. Family history is one of the paramount non modifiable risk factors for developing hypertension. Hence, it becomes mandatory to assess the cardiac autonomic functions, which play an important role in the regulation of Blood Pressure (BP), in prehypertensive individuals with a family history. Aim: To compare the variations in parameters of cardiac autonomic function tests in prehypertensive individuals with and without a family history of hypertension. Materials and Methods: This cross-sectional study was conducted at the Institute of Physiology and Experimental Medicine, Madras Medical College, Chennai, Tamil Nadu, India from October 2020 to October 2021. The study included 30 prehypertensive individuals without a family history of hypertension and 30 prehypertensive individuals with a family history of hypertension, aged between 20 and 50 years, of both genders. They were recruited from the non communicable diseases Outpatient Department (OPD) at Rajiv Gandhi Government General Hospital, Chennai, Tamil Nadu, India. The prehypertensive range refers to a Systolic Blood Pressure (SBP) of 120-139 mmHg or a Diastolic Blood Pressure (DBP) of 80-89 mmHg. After obtaining informed consent, baseline parameters such as resting Heart Rate Variability (HRV) using AD instruments powerlab recorder, deep breathing test, Valsalva maneuver, isometric handgrip test, and Cold Pressor Test (CPT) were evaluated. The data obtained was statistically analysed using a Student’s t-test. Results: The mean age of prehypertensive individuals without a family history was 36.90±4.6 years, and in prehypertensive individuals with a family history, it was 36.43±5.3 years. The male to female ratio was higher. The resting SBP and DBP, as well as the basal heart rate, were significantly increased in the prehypertensive subjects with a family history. Time domain variables such as the mean RR, Root Mean Square of Successive Difference (RMSSD), and pRR50 were reduced in prehypertensive individuals with a family history. Among the frequency domain variables, the total power was reduced, while the low-frequency component and LF:HF ratio were significantly increased. The E/I ratio and Valsalva Ratio (VR) were also significantly reduced in prehypertensive individuals with a family history. Thus, the results emphasise that there is significant autonomic dysfunction in prehypertensive individuals with a family history of hypertension compared to prehypertensive individuals without a family history. Conclusion: Cardiac autonomic function tests in prehypertensive individuals with a family history indicate a definite sympathovagal imbalance in the form of sympathetic overactivity. This may substantiate the role of genetic predisposition in them. Chronic activation of the sympathetic nervous system makes them more prone to developing early hypertension.

The aim of this systematic review with meta-analysis was to determine differences in cardiovascular autonomic parameters between patients with myasthenia gravis (MG) and healthy controls (HCs). Two reviewers searched four electronic databases, namely PubMed, Web of Science, EMBASE, and SCOPUS, from database inception to 7 July 2023 for studies investigating cardiovascular autonomic parameters in MG vs. HCs. A random-effects meta-analysis was performed to compute Hedges’ g ± 95% confidence intervals (CI). Out of a total of 2200 records, 8 observational studies with a sample size of 301 patients with MG and 454 HCs were included in the systematic review. Meta-analysis revealed lower values of expiration/inspiration ratio (g = −0.45, I2 = 74.7), baroreflex sensitivity (g = −0.56, 95%CI −0.80, −0.33; I2 = 0.3), percentage of adjacent NN intervals differing by more than 50 ms (g = −1.2, I2 = 82.8), square root of the mean of squared differences between successive beat intervals (g = −1.94, I2 = 95.1), mean of the standard deviations of all NN intervals (g = −0.83, 95%CI −1.37, −0.28; I2 = 55.5), and high frequency of HRV during tilt (g = −0.75, 95%CI −0.11, −0.39; I2 = 0). MG patients vs. HCs had higher systolic blood pressure (g = 0.39; I2 = 56.1), sympathovagal balance at rest/during tilt (LF/HF-RRIsupine, g = 0.44; I2 = 0; LF/HF-RRItilt, g = 0.86; I2 = 0; LF/HFtilt, g = 0.40; I2 = 0). As a group, MG patients have altered cardiac autonomic function, including decreased parasympathetic function, lower baroreflex sensitivity, and higher sympathovagal balance at rest and during orthostatic challenges.

Purpose: Acute decompensated heart failure (ADHF) is associated with inflammation, oxidative stress, and excess sympathetic drive. It is unknown whether neuromodulation would improve inflammation and oxidative stress in acute heart failure. We, therefore, performed this proof-of-concept study to evaluate the effects of neuromodulation using noninvasive low-level tragus stimulation on inflammation and oxidative stress in ADHF. Methods: Nineteen patients with ejection fraction < 40% were randomized to neuromodulation 4 h twice daily (6–10 a.m. and 6–10 p.m.) (n = 8) or sham stimulation (n = 11) during hospital admission. All patients received standard-of-care treatment. Blood samples were collected at admission and discharge. Serum cytokines were assayed using standard immunosorbent techniques. Reactive oxygen species inducibility from cultured coronary endothelial cells exposed to patient sera was determined using a dihydrodichlorofluorescein probe test (expressed as fluorescein units). Results: Compared to sham stimulation, neuromodulation was associated with a significant reduction of circulating serum interleukin-6 levels (−78% vs. −9%; p = 0.012). Similarly, neuromodulation led to a reduction of endothelial cell oxidative stress in the neuromodulation group (1363 units to 978 units, p = 0.003) compared to sham stimulation (1146 units to 1083 units, p = 0.094). No significant differences in heart rate, blood pressure, or renal function were noted between the two groups. Conclusion: In this proof-of-concept pilot study, in acute decompensated heart failure, neuromodulation was feasible and safe and was associated with a reduction in systemic inflammation and attenuation of coronary endothelial cellular oxidative stress. Clinical trial registration: NCT02898181. [ABSTRACT FROM AUTHOR]

Introduction: Individuals with prehypertension are at an increased risk of developing hypertension. Family history is one of the paramount non modifiable risk factors for developing hypertension. Hence, it becomes mandatory to assess the cardiac autonomic functions, which play an important role in the regulation of Blood Pressure (BP), in prehypertensive individuals with a family history. Aim: To compare the variations in parameters of cardiac autonomic function tests in prehypertensive individuals with and without a family history of hypertension. Materials and Methods: This cross-sectional study was conducted at the Institute of Physiology and Experimental Medicine, Madras Medical College, Chennai, Tamil Nadu, India from October 2020 to October 2021. The study included 30 prehypertensive individuals without a family history of hypertension and 30 prehypertensive individuals with a family history of hypertension, aged between 20 and 50 years, of both genders. They were recruited from the non communicable diseases Outpatient Department (OPD) at Rajiv Gandhi Government General Hospital, Chennai, Tamil Nadu, India. The prehypertensive range refers to a Systolic Blood Pressure (SBP) of 120-139 mmHg or a Diastolic Blood Pressure (DBP) of 80-89 mmHg. After obtaining informed consent, baseline parameters such as resting Heart Rate Variability (HRV) using AD instruments powerlab recorder, deep breathing test, Valsalva maneuver, isometric handgrip test, and Cold Pressor Test (CPT) were evaluated. The data obtained was statistically analysed using a Student's t-test. Results: The mean age of prehypertensive individuals without a family history was 36.90±4.6 years, and in prehypertensive individuals with a family history, it was 36.43±5.3 years. The male to female ratio was higher. The resting SBP and DBP, as well as the basal heart rate, were significantly increased in the prehypertensive subjects with a family history. Time domain variables such as the mean RR, Root Mean Square of Successive Difference (RMSSD), and pRR50 were reduced in prehypertensive individuals with a family history. Among the frequency domain variables, the total power was reduced, while the low-frequency component and LF:HF ratio were significantly increased. The E/I ratio and Valsalva Ratio (VR) were also significantly reduced in prehypertensive individuals with a family history. Thus, the results emphasise that there is significant autonomic dysfunction in prehypertensive individuals with a family history of hypertension compared to prehypertensive individuals without a family history. Conclusion: Cardiac autonomic function tests in prehypertensive individuals with a family history indicate a definite sympathovagal imbalance in the form of sympathetic overactivity. This may substantiate the role of genetic predisposition in them. Chronic activation of the sympathetic nervous system makes them more prone to developing early hypertension. [ABSTRACT FROM AUTHOR]

The aim of this systematic review with meta-analysis was to determine differences in cardiovascular autonomic parameters between patients with myasthenia gravis (MG) and healthy controls (HCs). Two reviewers searched four electronic databases, namely PubMed, Web of Science, EMBASE, and SCOPUS, from database inception to 7 July 2023 for studies investigating cardiovascular autonomic parameters in MG vs. HCs. A random-effects meta-analysis was performed to compute Hedges' g ± 95% confidence intervals (CI). Out of a total of 2200 records, 8 observational studies with a sample size of 301 patients with MG and 454 HCs were included in the systematic review. Meta-analysis revealed lower values of expiration/inspiration ratio (g = −0.45, I2 = 74.7), baroreflex sensitivity (g = −0.56, 95%CI −0.80, −0.33; I2 = 0.3), percentage of adjacent NN intervals differing by more than 50 ms (g = −1.2, I2 = 82.8), square root of the mean of squared differences between successive beat intervals (g = −1.94, I2 = 95.1), mean of the standard deviations of all NN intervals (g = −0.83, 95%CI −1.37, −0.28; I2 = 55.5), and high frequency of HRV during tilt (g = −0.75, 95%CI −0.11, −0.39; I2 = 0). MG patients vs. HCs had higher systolic blood pressure (g = 0.39; I2 = 56.1), sympathovagal balance at rest/during tilt (LF/HF-RRIsupine, g = 0.44; I2 = 0; LF/HF-RRItilt, g = 0.86; I2 = 0; LF/HFtilt, g = 0.40; I2 = 0). As a group, MG patients have altered cardiac autonomic function, including decreased parasympathetic function, lower baroreflex sensitivity, and higher sympathovagal balance at rest and during orthostatic challenges. [ABSTRACT FROM AUTHOR]

The relevance of the subject is the significance of exploring the role of the autonomic nervous system in regulating the cardiovascular system to improve the welfare of productive animals. Heart rate variability is a non-invasive research method that can be useful in exploring the health status of an animal and analysing its psychophysiological state in farm conditions. The purpose of the research – to determine the effect of the tone of autonomic nervous regulation on the cow’s body, which is reflected in changes in the sympathovagal balance. Experimental research was conducted on Ukrainian Black-and-White dairy cows. To explore the variability of heart rate, an electrocardiograph was used, followed by the determination of the main indicators according to the Baevsky method, which included the determination of mode, mode amplitude, variation range, autonomic balance index, autonomic rhythm index and stress index. Based on the results of the study, three experimental groups of animals were established: normotonics, vagotonics, and sympathotonics. Considering the results obtained, cows, depending on the influence of the tone of the autonomic nervous system, have differences in the activity of the cardiovascular system. It will result in different responses to stress, which in turn will affect their productivity. Determination of heart rate variability can be one of the indispensable indicators in analysing the health of an animal on a dairy farm. This issue is a promising area of research, especially when exploring the metabolic processes of high-yield cows to improve productivity while maintaining the physiological state of the animal

The authors compared the linear and nonlinear heart rate variability dynamics from rest through maximal exercise in postmenopausal women who trained at either moderate or high intensities. The outcome variables included the RR triangular index, TINN, SD1, SD2, SD1/SD2, DFA α1, DFA α2, and α1/α2. Maximal exercise reduced SD1, SD2, DFA α1, DFA α2, α1/α2, RRTri, and TINN in both groups and increased SD1/SD2 (p <.05). Two minutes of active recovery produced significant increases in SD1, SD2, DFA α1, and TINN, compared with exercise in both groups (p <.0001). There was also a significant main effect between groups for RRTri during exercise recovery, with the moderate group achieving higher levels (p <.04). The authors have shown that both moderate and vigorous exercise training can lead to a healthy response to maximal exercise and recovery, with the moderate group having a slightly improved recovery in the triangular index. [ABSTRACT FROM AUTHOR]

The present study examined the effects of a 12-week low-intensity resistance exercise training (LIRET) regimen on heart rate variability, strength, and body composition in obese postmenopausal women. Participants were randomly assigned to 12 weeks of either LIRET (n = 10) or nonexercising control group (n = 10). Heart rate variability, leg muscle strength, and body composition were measured before and after 12 weeks. There were significant decreases (p < .05) in sympathovagal balance (LnLF/LnHF) and sympathetic tone (nLF), as well as significant increases (p < .05) in parasympathetic tone (nHF) and strength following LIRET compared with no changes after control. There were no significant changes in body composition after LIRET or control. LIRET may be an effective therapeutic intervention for improving sympathovagal balance and strength in obese postmenopausal women. As obese postmenopausal women are at increased risk of developing cardiovascular diseases and physical disability, they could potentially benefit from LIRET. [ABSTRACT FROM AUTHOR]

Sympathovagal balance is important in the pathogenesis of hypertension and independently associated with mortality. We evaluated the value of automated analysis of cross-correlation baroreflex sensitivity (xBRS) and heart rate variability (HRV) and its relationship with clinical covariates in 13,326 participants from the multi-ethnic HELIUS study. Finger blood pressure (BP) was continuously recorded, from which xBRS, standard deviation of normal-to-normal intervals (SDNN), and squared root of mean squared successive difference between normal-to-normal intervals (RMSDD) were determined. A subset of 3356 recordings > 300 s was used to derive the minimally required duration by comparing shortened to complete recordings, defined as intraclass correlation (ICC) > 0.90. For xBRS and SDNN, 120 s and 180 s were required (ICC 0.93); for RMSDD, 60 s (ICC 0.94) was sufficient. We included 10,252 participants (median age 46 years, 54% women) with a recording > 180 s for the regression. xBRS, SDNN, and RMSDD decreased linearly up to 50 years of age. For xBRS, there was a signification interaction with sex, with for every 10 years a decrease of 4.3 ms/mmHg (95%CI 4.0–4.6) for men and 5.9 ms/mmHg (95%CI 5.6–6.1) for women. Using splines, we observed sex-dependent nonlinearities in the relation with BP, waist-to-hip-ratio, and body mass index. Future studies can help unravel the dynamics of these relations and assess their predictive value. Panel 1 depicts automatic analysis and filtering of finger BP recordings, panel 2 depicts computation of xBRS from interpolated beat to beat data of systolic BP and interbeat interval, and (IBI) SDNN and RMSDD are computed directly from the filtered IBI dataset. Panel 3 depicts the results of large-scale analysis and relation of xBRS with age, sex, blood pressure and body mass index. [ABSTRACT FROM AUTHOR]

The relevance of the subject is the significance of exploring the role of the autonomic nervous system in regulating the cardiovascular system to improve the welfare of productive animals. Heart rate variability is a non-invasive research method that can be useful in exploring the health status of an animal and analysing its psychophysiological state in farm conditions. The purpose of the research -- to determine the effect of the tone of autonomic nervous regulation on the cow's body, which is reflected in changes in the sympathovagal balance. Experimental research was conducted on Ukrainian Black-and-White dairy cows. To explore the variability of heart rate, an electrocardiograph was used, followed by the determination of the main indicators according to the Baevsky method, which included the determination of mode, mode amplitude, variation range, autonomic balance index, autonomic rhythm index and stress index. Based on the results of the study, three experimental groups of animals were established: normotonics, vagotonics, and sympathotonics. Considering the results obtained, cows, depending on the influence of the tone of the autonomic nervous system, have differences in the activity of the cardiovascular system. It will result in different responses to stress, which in turn will affect their productivity. Determination of heart rate variability can be one of the indispensable indicators in analysing the health of an animal on a dairy farm. This issue is a promising area of research, especially when exploring the metabolic processes of high-yield cows to improve productivity while maintaining the physiological state of the animal [ABSTRACT FROM AUTHOR]

Introduction: Medical education has been reported to be one of the most stressful academic curriculum worldwide, with a potential of negatively affecting the physical and mental health of medical students. Meditation is a self-produced relaxation technique which restores the mental peace by relieving emotional and physiological stress and is an accepted therapy to reduce stress. Aim: To study the effect of heartfulness meditation on cortisol levels and vital parameters in healthy female medical students. Materials and Methods: This study was a prospective longitudinal study conducted in the department of physiology at Sri Padmavathi Medical College for women, SVIMS, Andhra Pradesh, India. Sixty female medical students of age group 18 to 25 years were undergone heartfulness meditation training for a period of 6 months from September 2021 to February 2022 Baseline measurements of cortisol, heart rate, Respiratory Rate (RR) and Blood Pressure (BP) were taken at the beginning of the session and after 6 months of intervention program i.e., from September 2021 to February 2022. Later pre and postvalues were compared and analysed statistically by using paired sample t-test and the p-value

Postural orthostatic tachycardia syndrome (POTS) is a disorder of the autonomic nervous system characterised by orthostatic intolerance and orthostatic tachycardia without hypotension. Heart rate variability (HRV) is the most reliable and objective tool for assessing autonomic dysfunction severity. In the present study, we aimed to investigate HRV changes in resting supine position, predicting severity and cardiovascular risk in patients with POTS. We compared 100 POTS patients with 160 healthy controls matched for age and gender in a case-control design. Along with clinical characterization, heart rate variability was evaluated using ambulatory 5 min ECG in lead II and expressed in frequency and time-domain measures. The resting heart rate of patients with POTS was significantly higher than that of healthy controls. In HRV measures, root mean square successive difference of RR intervals (RMSSD), total and high frequency (HF) powers were statistically lower with an increased low frequency (LF) to high-frequency ratio in patients with POTS compared to healthy controls. Further, stepwise logistic regression analysis showed increased basal HR and LF/HF as significant predictors of POTS and its severity. This is the first study on a large cohort of patients with POTS from India wherein HRV was assessed. The study showed reduced parasympathetic activity and increased sympathetic activity in patients with POTS compared to healthy controls. These findings of increased resting heart rate and LF/HF were found to be potential predictors of POTS and future cardiovascular risks, which need to be replicated in a larger and more homogenized cohort. [ABSTRACT FROM AUTHOR]

The present study examined the effects of a 12-week Tai Chi (TC) training regimen on heart rate variability (HRV), symptomatology, muscle fitness and body composition in women with fibromyalgia. Participants were randomly assigned to either a TC training group (n = 18) or a control group (n = 19). HRV, symptomatology, muscle fitness and body composition were measured before and after 12 weeks. There were significant decreases (p < 0.05) in sympathovagal balance (LnLF/LnHF), sympathetic tone (LnLF, nLF), pain, and fatigue, and significant increases (p < 0.05) in parasympathetic tone (LnHF, nHF), strength and flexibility following TC compared with no changes after control. The changes in LnLF and LnLF/LnHF were correlated with changes in pain. There were no significant changes in HR, sleep quality and body composition after TC or control. TC may be an effective therapeutic intervention for improving sympathovagal balance, pain, fatigue, strength and flexibility in women with fibromyalgia. [ABSTRACT FROM AUTHOR]

Introduction: Obstructive sleep apnoea (OSA) in children is associated with numerous adverse outcomes, including elevated blood pressure. While the associations between OSA, obesity, and autonomic dysfunction are recognised, the precise mechanisms linking these factors and their relationship with elevated blood pressure in children remain unclear., Methods: This retrospective case series included 76 children with OSA. The relationships between night-time systolic and diastolic blood pressures, body mass index, and clinical, polysomnographic, and sleep heart rate variability variables were investigated. Mediation and moderation analyses were performed., Results: Correlation analyses revealed significant associations between both systolic and diastolic blood pressures with body mass index, age, sex, adenoidal-nasopharyngeal ratio, apnoea-hypopnoea index, and sleep low frequency/high frequency (LF/HF) ratio. In multivariable linear regression models, body mass index, adenoidal-nasopharyngeal ratio, and LF/HF ratio were independently associated with systolic blood pressure, while body mass index and adenoidal-nasopharyngeal ratio were independently associated with diastolic blood pressure. Mediation and moderation analyses identified a conceptual mediation with a moderated direct path model in which body mass index mediated, and the LF/HF ratio moderated, the relationship between apnoea-hypopnoea index and systolic blood pressure. Additionally, children with concomitant OSA and attention deficit hyperactivity disorder had a significantly higher LF/HF ratio than those with OSA alone., Conclusion: In children with OSA, the relationship between apnoea-hypopnoea index and systolic blood pressure was mediated by weight status and modulated by sleep sympathovagal balance. Children with OSA and attention deficit hyperactivity disorder exhibited greater disturbances in sympathovagal balance. Further research is warranted to explore these associations., (© 2025 John Wiley & Sons Ltd.)

CONTEXT: Obesity is one of the important causative factors for multiple co-morbid conditions that can lead to metabolic and cardiac disorders. Many research studies indicate the association of obesity and sudden cardiac deaths. AIMS: This study was aimed to evaluate the cardiac autonomic nervous system activity, given by the changes in heart rate variability (HRV) in healthy obese young adults. SETTINGS AND DESIGN: This cross-sectional study included thirty obese young adult males of 18–25 years and 30 age-matched healthy adult males. Power spectral analysis of HRV was used to determine the autonomic imbalance. SUBJECTS AND METHODS: HRV was performed using HRV software (Lab Chart 7). Numerical data of absolute values of low frequency (LF) and high frequency (HF) (in ms2), normalized units of LF and HF (in nu) and LF/HF ratio were expressed as mean ± standard deviation and analyzed. RESULTS: On statistical analysis, it was found that HF in normalized units was significantly low in obese young adults compared to age-matched controls. LF (nu) and LF/HF ratio were higher in obese subjects compared to controls, though they were not statistically significant. Although there was negative correlation between HRV parameters and body mass index in obese individuals, it was not significant. CONCLUSIONS: These results suggest that obese young adults present with changes in the autonomic nervous system, characterized by decrease in parasympathetic activity.

This study aimed to determine the effects of in-feed inclusion of humic substances (HS) and/or calcium carbonate (CaCO3) on the performance and welfare of laying hens. A total number of 144 Hy-Line Brown laying hens (55 weeks old) were randomly assigned to four treatments, T1--T4 (36 birds per treatment). T1 hens were fed on a control diet without HS or CaCO3, T2 hens were fed on the control diet + 2.00 g per bird per day CaCO3, T3 hens were fed on the control diet + 0.20% HS and T4 hens were fed on the control diet + 0.20% HS + 2.00 g/bird/day CaCO3. The experiment started after 15 days of adaptation and lasted 8 weeks. The parameters evaluated were percentage of hen-day egg production, food consumption, mortality, egg quality parameters and heart rate variability (welfare indicator). Hens in the T3 group showed a significantly lower feed intake than those in the other three groups, however, significantly higher daily egg production was recorded in groups T3 and T4 compared to T1 and T2. Eggshell quality characteristics were significantly improved by HS supplementation and eggs laid by hens in groups T1, and T4 presented paler yolk and shell color than those in the other groups. In conclusion, these results indicated that in-feed inclusion of HS had a beneficial effect on laying hens' productive performance including egg production and eggshells quality. [ABSTRACT FROM AUTHOR]

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Introduction: Medical education can impose significant psychological stress on undergraduate students. A considerable degree of psychological morbidity has been reported among medical students ranging from stress, interpersonal problems, and suicidal ideation to psychiatric disorders and they tend to have greater psychological distress than the general population. Stress is one of the factors known to cause variation in heart rate variability. Heart Rate Variability (HRV) is a proven reliable non invasive marker of cardiovascular health and has been used in cardiovascular risk stratification. Aim: To study the effect of stress on heart rate variability in medical students. Materials and Methods: This cross-sectional study was conducted in the Department of Physiology at JSS Medical College, Mysuru, Karnataka, India, from December 2017 to February 2018. Total 58 healthy first year MBBS medical students aged between 18- 25 years with normal Body Mass Index (BMI) were included in the study. The Medical Student Stressor Questionnaire (MSSQ), a validated instrument to identify sources of stress in medical students were used to assess the level of stress. AD Instruments PowerLab (Data Acquisition System) was used to record the frequency and time domain analysis of HRV from the limb leads. Kruskal-Wallis test was applied to assess the association between stress domains and HRV domains, using Statistical Package for Social Sciences (SPSS) version 23.0. Results: Most of the medical students had mild to moderate degrees of stress in all the domains of the MSSQ. There was no statistically significant (p-value >0.05) association found between domains of stress with the time and frequency domains of the HRV. Conclusion: Though it was found that medical students were exposed to significant stressors during their medical training, the stress was of mild to moderate degree which had no significant effect on HRV. [ABSTRACT FROM AUTHOR]

This study analyzed the effects of physical training programs on heart rate variability, as a measure of sympathovagal balance, in children and adolescents with chronic diseases. Relevant articles were systematically searched in Pubmed, Science Direct, Web of Science, Scopus, Google Scholar and Embase scientific databases. We performed a meta-analysis using an inverse variance heterogeneity model. Effect size calculation was based on the standardized mean differences between pre- and post-intervention assessments, assuring at least a single-group repeated-measures model for each extracted group. Ten studies (252 participants) were included, seven in obese subjects, two in type-1 diabetes, and one in cerebral palsy. When time-domain variables were analyzed, exercise was found to moderately increase RMSSD (SMD=0.478; 95%CI: 0.227 to 0.729; p <0.001), SDNN (SMD=0.367; 95%CI: 0.139 to 0.595; p =0.002) and pNN50 (SMD=0.817; 95%CI: 0.139 to 0.595; p =0.002). As for frequency-domain variables, exercise presented a moderate increasing effect on HF (SMD=0.512; 95%CI: 0.240 to 0.783; p <0.001), a negligible effect for LF (SMD=0.077; 95%CI: –0.259 to 0.412; p <0.001) and a non-significant reduction for LF/HF (SMD=–0.519; 95%CI: -1.162 to 0.124; p =0.114). In conclusion, physical training programs are able to modulate heart rate variability in children and adolescents with chronic diseases, affecting mainly the time-domain variables. [ABSTRACT FROM AUTHOR]

The effects of caffeine or caffeine-based energy drinks on the recovery of autonomic nervous system balance after exercise have been the subject of several studies which yielded inconclusive results. In a recent study by Porto et al., the impact of a caffeine-based energy drink on heart rate variability (HRV) before and after a moderate aerobic exercise (running on a treadmill) has been studied in a randomized, crossover trial on healthy and active young males. It was concluded that an energy drink consumed before exercise did not affect HRV indices during post-exercise recovery. However, this conclusion is somewhat inconsistent with the reported data and hence may be misleading. Here, I discuss the shortcomings of that study and point out some inaccuracies in the reported results. Considering the above, it appears that energy drink consumption may affect some HRV indices after exercise, at least those related to high frequency changes in the autonomic activity. [ABSTRACT FROM AUTHOR]

Regular physical activity is important for cardiovascular health. However, high-volume endurance exercise has been associated with increased number of electrocardiogram (ECG) abnormalities, including disturbances in cardiac rhythm (arrhythmias) and abnormalities in ECG pattern. The aim of this study was to assess if heart rate variability (HRV) is associated with ECG abnormalities. Fifteen participants with previous cycling experience completed a 21-day high-volume endurance exercise cycle over 3,515 km. Participants wore a 5-lead Holter monitor for 24 h pre- and post-exercise, which was used to quantify ECG abnormalities and export sinus R-to-R intervals (NN) used to calculate HRV characteristics. As noise is prevalent in 24-h HRV recordings, both 24-h and heart rate collected during stable periods of time (i.e., deep sleep) were examined. Participants experienced significantly more arrhythmias post high-volume endurance exercise (median = 35) compared to pre (median = 12; p = 0.041). All 24-h and deep sleep HRV outcomes were not different pre-to-post high-volume endurance exercise (p > 0.05). Strong and significant associations with arrhythmia number post-exercise were found for total arrhythmia (total arrhythmia number pre-exercise, ρ = 0.79; age, ρ = 0.73), supraventricular arrhythmia (supraventricular arrhythmia number pre-exercise: ρ = 0.74; age: ρ = 0.66), and ventricular arrhythmia (age: ρ = 0.54). As a result, age and arrhythmia number pre-exercise were controlled for in hierarchical regression, which revealed that only deep sleep derived low frequency to high frequency (LF/HF) ratio post high-volume endurance exercise predicted post total arrhythmia number (B = 0.63, R 2Δ = 34%, p = 0.013) and supraventricular arrhythmia number (B = 0.77, R 2Δ = 69%, p < 0.001). In this study of recreationally active people, only deep sleep derived LF/HF ratio was associated with more total and supraventricular arrhythmias after high-volume endurance exercise. This finding suggests that measurement of sympathovagal balance during deep sleep might be useful to monitor arrhythmia risk after prolonged high-volume endurance exercise performance. [ABSTRACT FROM AUTHOR]

Regular physical activity is important for cardiovascular health. However, high-volume endurance exercise has been associated with increased number of electrocardiogram (ECG) abnormalities, including disturbances in cardiac rhythm (arrhythmias) and abnormalities in ECG pattern. The aim of this study was to assess if heart rate variability (HRV) is associated with ECG abnormalities. Fifteen participants with previous cycling experience completed a 21-day high-volume endurance exercise cycle over 3,515 km. Participants wore a 5-lead Holter monitor for 24 h pre- and post-exercise, which was used to quantify ECG abnormalities and export sinus R-to-R intervals (NN) used to calculate HRV characteristics. As noise is prevalent in 24-h HRV recordings, both 24-h and heart rate collected during stable periods of time (i.e., deep sleep) were examined. Participants experienced significantly more arrhythmias post high-volume endurance exercise (median = 35) compared to pre (median = 12; p = 0.041). All 24-h and deep sleep HRV outcomes were not different pre-to-post high-volume endurance exercise (p > 0.05). Strong and significant associations with arrhythmia number post-exercise were found for total arrhythmia (total arrhythmia number pre-exercise, ρ = 0.79; age, ρ = 0.73), supraventricular arrhythmia (supraventricular arrhythmia number pre-exercise: ρ = 0.74; age: ρ = 0.66), and ventricular arrhythmia (age: ρ = 0.54). As a result, age and arrhythmia number pre-exercise were controlled for in hierarchical regression, which revealed that only deep sleep derived low frequency to high frequency (LF/HF) ratio post high-volume endurance exercise predicted post total arrhythmia number (B = 0.63, R2Δ = 34%, p = 0.013) and supraventricular arrhythmia number (B = 0.77, R2Δ = 69%, p < 0.001). In this study of recreationally active people, only deep sleep derived LF/HF ratio was associated with more total and supraventricular arrhythmias after high-volume endurance exercise. This finding suggests that measurement of sympathovagal balance during deep sleep might be useful to monitor arrhythmia risk after prolonged high-volume endurance exercise performance.

CONTEXT: Obesity is one of the important causative factors for multiple co-morbid conditions that can lead to metabolic and cardiac disorders. Many research studies indicate the association of obesity and sudden cardiac deaths. AIMS: This study was aimed to evaluate the cardiac autonomic nervous system activity, given by the changes in heart rate variability (HRV) in healthy obese young adults. SETTINGS AND DESIGN: This cross-sectional study included thirty obese young adult males of 18-25 years and 30 age-matched healthy adult males. Power spectral analysis of HRV was used to determine the autonomic imbalance. SUBJECTS AND METHODS: HRV was performed using HRV software (Lab Chart 7). Numerical data of absolute values of low frequency (LF) and high frequency (HF) (in ms2), normalized units of LF and HF (in nu) and LF/HF ratio were expressed as mean ± standard deviation and analyzed. RESULTS: On statistical analysis, it was found that HF in normalized units was significantly low in obese young adults compared to age-matched controls. LF (nu) and LF/HF ratio were higher in obese subjects compared to controls, though they were not statistically significant. Although there was negative correlation between HRV parameters and body mass index in obese individuals, it was not significant. CONCLUSIONS: These results suggest that obese young adults present with changes in the autonomic nervous system, characterized by decrease in parasympathetic activity. [ABSTRACT FROM AUTHOR]

Vagus nerve stimulation (VNS) exerts a cortical modulating effect through its diffuse projections, especially involving cerebral structures related to autonomic regulation. The influence of VNS on cardiovascular autonomic function in drug-resistant epilepsy patients is still debated. We aimed to evaluate the impact of VNS on cardiovascular autonomic function in drug-resistant epilepsy patients, after three months of neurostimulation, using the heart rate variability (HRV) analysis.

Background: Disruptions in central autonomic processes in people with epilepsy have been studied through evaluation of heart rate variability (HRV). Decreased HRV appears in epilepsy compared to healthy controls, suggesting a shift in autonomic balance toward sympathetic dominance; recent studies have associated HRV changes with seizure severity and outcome of interventions. However, the processes underlying these autonomic changes remain unclear. We examined the nature of these changes by assessing alterations in whole-brain functional connectivity, and relating those alterations to HRV.Methods: We examined regional brain activity and functional organization in 28 drug-resistant epilepsy patients and 16 healthy controls using resting-state functional magnetic resonance imaging (fMRI). We employed an HRV state-dependent functional connectivity (FC) framework with low and high HRV states derived from the following four cardiac-related variables: 1. RR interval, 2. root mean square of successive differences (RMSSD), 4. low-frequency HRV (0.04–0.15 Hz; LF-HRV) and high-frequency HRV (0.15–0.40 Hz; HF-HRV). The effect of group (epilepsy vs. controls), HRV state (low vs. high) and the interactions of group and state were assessed using a mixed analysis of variance (ANOVA). We assessed FC within and between 7 large-scale functional networks consisting of cortical regions and 4 subcortical networks, the amygdala, hippocampus, basal ganglia and thalamus networks.Results: Consistent with previous studies, decreased RR interval (increased heart rate) and decreased HF-HRV appeared in people with epilepsy compared to healthy controls. For both groups, fluctuations in heart rate were positively correlated with BOLD activity in bilateral thalamus and regions of the cerebellum, and negatively correlated with BOLD activity in the insula, putamen, superior temporal gyrus and inferior frontal gyrus. Connectivity strength in patients between right thalamus and ventral attention network (mainly insula) increased in the high LF-HRV state compared to low LF-HRV; the opposite trend appeared in healthy controls. A similar pattern emerged for connectivity between the thalamus and basal ganglia.Conclusion: The findings suggest that resting connectivity patterns between the thalamus and other structures underlying HRV expression are modified in people with drug-resistant epilepsy compared to healthy controls.

Background: Disruptions in central autonomic processes in people with epilepsy have been studied through evaluation of heart rate variability (HRV). Decreased HRV appears in epilepsy compared to healthy controls, suggesting a shift in autonomic balance toward sympathetic dominance; recent studies have associated HRV changes with seizure severity and outcome of interventions. However, the processes underlying these autonomic changes remain unclear. We examined the nature of these changes by assessing alterations in whole-brain functional connectivity, and relating those alterations to HRV. Methods: We examined regional brain activity and functional organization in 28 drug-resistant epilepsy patients and 16 healthy controls using resting-state functional magnetic resonance imaging (fMRI). We employed an HRV state-dependent functional connectivity (FC) framework with low and high HRV states derived from the following four cardiac-related variables: 1. RR interval, 2. root mean square of successive differences (RMSSD), 4. low-frequency HRV (0.04–0.15 Hz; LF-HRV) and high-frequency HRV (0.15–0.40 Hz; HF-HRV). The effect of group (epilepsy vs. controls), HRV state (low vs. high) and the interactions of group and state were assessed using a mixed analysis of variance (ANOVA). We assessed FC within and between 7 large-scale functional networks consisting of cortical regions and 4 subcortical networks, the amygdala, hippocampus, basal ganglia and thalamus networks. Results: Consistent with previous studies, decreased RR interval (increased heart rate) and decreased HF-HRV appeared in people with epilepsy compared to healthy controls. For both groups, fluctuations in heart rate were positively correlated with BOLD activity in bilateral thalamus and regions of the cerebellum, and negatively correlated with BOLD activity in the insula, putamen, superior temporal gyrus and inferior frontal gyrus. Connectivity strength in patients between right thalamus and ventral attention network (mainly insula) increased in the high LF-HRV state compared to low LF-HRV; the opposite trend appeared in healthy controls. A similar pattern emerged for connectivity between the thalamus and basal ganglia. Conclusion: The findings suggest that resting connectivity patterns between the thalamus and other structures underlying HRV expression are modified in people with drug-resistant epilepsy compared to healthy controls. [ABSTRACT FROM AUTHOR]

Background: In precapillary pulmonary hypertension (PH), nasal high flow therapy (NHF) may favorably alter sympathovagal balance (SVB) and sleep-related breathing through washout of anatomical dead space and alleviation of obstructive sleep apnea (OSA) due to generation of positive airway pressure. Objectives: To investigate the effects of NHF on SVB, sleep, and OSA in patients with PH, and compare them with those of positive airway pressure therapy (PAP). Methods: Twelve patients with PH (Nice class I or IV) and confirmed OSA underwent full polysomnography, and noninvasive monitoring of SVB parameters (spectral analysis of heart rate, diastolic blood pressure variability). Study nights were randomly split into four 2-h segments with no treatment, PAP, NHF 20 L/min, or NHF 50 L/min. In-depth SVB analysis was conducted on 10-min epochs during daytime and stable N2 sleep at nighttime. Results: At daytime and compared with no treatment, NHF20 and NHF50 were associated with a flow-dependent increase in peripheral oxygen saturation but a shift in SVB towards increased sympathetic drive. At nighttime, NHF20 was associated with increased parasympathetic drive and improvements in sleep efficiency, but did not alter OSA severity. NHF50 was poorly tolerated. PAP therapy improved OSA but had heterogenous effects on SVB and neutral effects on sleep outcomes. Hemodynamic effects were neutral for all interventions. Conclusions: In sleeping PH patients with OSA NHF20 but not NHF50 leads to decreased sympathetic drive likely due to washout of anatomical dead space. NHF was not effective in lowering the apnea-hypopnoea index and NHF50 was poorly tolerated. [ABSTRACT FROM AUTHOR]

Background: Increased sympathetic drive is the key determinant of systolic heart failure progression, being associated with worse functional status, arrhythmias, and increased mortality. Central sleep apnea is highly prevalent in systolic heart failure, and its effects on sympathovagal balance (SVB) and hemodynamics might depend on relative phase duration and background pathophysiology. Objective: This study compared the effects of central apneas in patients with and without systolic heart failure on SVB and hemodynamics during sleep. Methods: During polysomnography, measures of SVB (heart rate and diastolic blood pressure variability) were non-invasively recorded and analyzed along with baroreceptor reflex sensitivity and hemodynamic parameters (stroke volume index, cardiac index, total peripheral resistance index). Data analysis focused on stable non-rapid eye movement N2 sleep, comparing normal breathing with central sleep apnea in subjects with and without systolic heart failure. Results: Ten patients were enrolled per group. In heart failure patients, central apneas had neutral effects on SVB (all p > 0.05 for the high, low, and very low frequency components of heart rate and diastolic blood pressure variability). Patients without heart failure showed an increase in very low and low frequency components of diastolic blood pressure variability in response to central apneas (63 ± 18 vs. 39 ± 9%; p = 0.001, 43 ± 12 vs. 31 ± 15%; p = 0.002). In all patients, central apneas had neutral hemodynamic effects when analyzed over a period of 10 min, but had significant acute hemodynamic effects. Conclusion: Effects of central apneas on SVB during sleep depend on underlying systolic heart failure, with neutral effects in heart failure and increased sympathetic drive in idiopathic central apneas. [ABSTRACT FROM AUTHOR]

Background: Elevated heart rate (HR) increases cardiovascular morbidity and mortality in hypertension. The impact of beta-blockers on patient prognosis in hypertension is controversial. This study examined the age-related effects of betaxolol on HR, muscle sympathetic nerve activity (MSNA), blood pressure (BP) and sympathovagal balance in untreated males with hypertension and tachycardia. Methods: Ten young (age 26 ± 1 years) and seven older (age 50 ± 4 years) males underwent measurement of BP, HR, HR variability (Poincare plot) and MSNA before and after 8 weeks treatment with betaxolol at the initial starting dose of 10 mg/day, which was increased to 20 mg/day once daily after 4 weeks in all subjects. Results: In younger subjects, betaxolol decreased systolic BP (−13 ± 4 mm Hg, p = .01) and HR (−29 ± 4 bpm, p

The heart may be a mirror of the soul, but the human mind is more than its heart rate variability (HRV). Many techniques to quantify HRV promise to give a view of what is going on in the body or even the psyche of the subject under study. This "Hypothesis" paper gives, on the one hand, a critical view on the field of HRV-analysis and, on the other hand, points out a possible direction of future applications. In view of the inherent variability of HRV and the underlying processes, as lined out here, the best use may be found in serial analysis in a subject/patient, to find changes over time that may help in early discovery of developing pathology. Not every future possibility is bright and shining, though, as demonstrated in a fictional diary excerpt from a future subject, living in a society geared toward preventive medicine. Here implanted biochips watch over the health of the population and artificial intelligence (AI) analyses the massive data flow to support the diagnostic process. [ABSTRACT FROM AUTHOR]

Background: Post‐traumatic stress disorder (PTSD) is a public health concern that may elevate the risk for cardiovascular disease (CVD). There are established sex differences in both PTSD risk and CVD risk. Purpose: To examine sex‐specific associations between subclinical PTSD symptom severity and subclinical CVD risk in young men and women. Methods: A total of 61 young adults (women: n = 29, mean age: 26 ± 7 years) completed the post‐traumatic stress disorder civilian checklist (PCL) and the Center for Epidemiologic Studies Depression Scale (CES‐D). Aortic stiffness was measured as carotid‐femoral pulse wave velocity (cfPWV). Peripheral vasomotor function was measured as flow‐mediated slowing (FMS) of carotid‐radial PWV following 5‐min forearm occlusion. Heart rate variability was used to assess sympathovagal balance as LF/HF ratio. Results: PCL score was positively correlated with CES‐D score (r = 0.79, p <.001), cfPWV (r = 0.33, p =.03) and LF/HF ratio (r = 0.42, p =.009) in men. PCL score was positively correlated to CES‐D score (r = 0.80, p <.001) in women, but was inversely correlated to cfPWV (r = −0.38, p =.02) and LF/HF ratio (r = −0.34, p =.04). PCL score was also inversely associated with FMS in women (r = −0.49, p =.01). Conclusion: There are sex differences in the association of PTSD symptoms and subclinical atherosclerosis. In men, increased PTSD symptoms may increase CVD risk by increasing sympathovagal balance and aortic stiffness. In women, increased PTSD symptoms may increase CVD risk via reducing vasomotor function. [ABSTRACT FROM AUTHOR]

In contrast to continuous positive airway pressure (CPAP), the use of adaptive servo-ventilation (ASV) for treatment of central sleep apnoea (CSA) was associated with increased mortality in patients with chronic systolic heart failure (CHF). In order to characterize the interplay between sleep-disordered breathing, CHF and sympathovagal balance (SVB) this study investigated the effect of nocturnal CPAP and ASV on SVB in CSA patients with or without CHF. Thirty-seven patients with ongoing positive airway pressure therapy (CPAP or ASV) for CSA (17 patients with systolic CHF - left ventricular ejection fraction <50% - and 20 patients with CSA but no CHF) underwent evaluation of SVB (spectral analysis of heart rate -HRV- and diastolic blood pressure variability) during full nocturnal polysomnography. The night was randomly split into equal parts including no treatment (NT), automatic CPAP and ASV. Data analysis was restricted to stable N2 sleep. In patients with CSA and systolic CHF, neither automatic CPAP nor ASV showed favourable effects on parameters reflecting SVB during N2 sleep (all p > 0.05). In contrast, in subjects with CSA without CHF automatic CPAP, but not ASV, favourably altered SVB by decreasing the low frequency and increasing the high frequency component of HRV (both p = 0.03). Effects of various modes of positive airway pressure therapy of CSA on SVB during sleep depend on the mode of pressure support and underlying cardiac function. Automatic CPAP but not ASV favourably influences SVB in subjects without CHF, whereas both interventions leave SVB unchanged in patients with CHF. • In CSA patients without CHF CPAP, but not ASV, favourably alters sympathetic drive. • Both CPAP and ASV leave sympathetic drive unchanged in CSA patients with CHF. • ASV does not lead to desired changes in CHF at night from a translational perspective. • These findings contribute to our understanding of the mechanism behind SERVE-HF. [ABSTRACT FROM AUTHOR]

New Findings: What is the central question of this study?Delayed cardiovascular responses occur following a single bout of remote ischaemic preconditioning (RIPC). Is heart rate variability (HRV), a surrogate marker of cardiac vagal control, able to detect a delayed effect after a single bout of RIPC? Do repeated bouts of RIPC further alter HRV?What is the main finding and its importance?Indices of HRV indicated a shift in sympathovagal balance toward greater parasympathetic activity following 2 weeks of RIPC but not after a single bout of RIPC. Thus, repeated bouts of RIPC were necessary to elicit changes in autonomic function. Remote ischaemic preconditioning (RIPC), induced by brief periods of ischaemia followed by reperfusion, protects against ischaemia–reperfusion injury and improves microvascular function. However, the effect of RIPC on autonomic function remains unclear. We hypothesized that RIPC, administered as a single bout or repeated over a 2‐week period, will increase markers of cardiac vagal control measured by heart rate variability (HRV). Thirty‐two young adults performed a single bout (n = 13), repeated bouts (n = 11), or served as a time control (n = 8). RIPC sessions consisted of four repetitions of 5 min unilateral brachial artery occlusion interspersed by 5 min of reperfusion. For the single bout protocol, resting lead II electrocardiogram (ECG) was collected before and 24, 48, 72 and 168 h post‐RIPC. The repeated bout protocol consisted of three 4‐day periods of RIPC training, each interspersed by a 1‐day break. Similar to time controls, ECG was collected before and 24 h after the last RIPC bout. HRV was analysed by power spectral density and symbolic dynamics using 350‐beat ECG segments. After a single bout of RIPC, no changes in HRV were observed at any time point (P > 0.05). After 2 weeks of repeated RIPC, the percentage of zero‐variation fragments (baseline = 13.1 ± 1.9%, post‐RIPC = 6.9 ± 1.5%, P < 0.05) and the LF/HF ratio decreased (baseline = 1.1 ± 0.2, post‐RIPC = 0.7 ± 0.1, P < 0.01), whereas the percentage of two‐variation fragments increased (baseline = 42.9 ± 3.6%, post‐RIPC = 52.5 ± 3.0%, P < 0.01). These data indicate that repeated RIPC is necessary to elicit changes in sympathovagal balance, specifically resulting in increased vagal and decreased sympathetic activity. [ABSTRACT FROM AUTHOR]

Objectives: Our study aimed to assess the impact of one night of slow-wave sleep (SWS) suppression on glucose tolerance, and explore whether melatonin plays a role in glucose tolerance impairment after SWS suppression.Methods: In sum, 20 volunteers participated in two experimental sessions: a session with SWS suppression during one night's sleep and a session with a regular night's sleep (control). Each session included collecting seven salivary samples. The following morning, an oral glucose tolerance test (OGTT) was performed.Results: SWS suppression effects depended on the individual blood glucose response to the OGTT. During the control session, 'responders' (N = 11), already presented with low glucose tolerance, which further declined after SWS suppression. 'Non-responders' (N = 9) experienced high glucose tolerance in both conditions. Among the responders, SWS suppression led to an increase in melatonin at the moment of awakening, while in non-responders melatonin increased during the first half of the night. In both conditions, responders were characterized by a shorter total sleep time (TST) and less rapid eye movement (REM) sleep. During SWS suppression, they had more non-rapid eye movement (NREM) stage 1 and longer nocturnal wakefulness. Responders and non-responders showed a comparable amount of SWS.Conclusions: This study highlights three key findings: first, SWS suppression leads to an increase in salivary melatonin; second, melatonin's effect on glucose tolerance depends on its secretion timing; and third, durations of REM sleep and nocturnal awakenings, appear to play an important role in melatonin secretion and glucose tolerance, indicating the potential clinical relevance of these findings for type 2 diabetes risk assessment. [ABSTRACT FROM AUTHOR]

Abstract Neuromodulation based on the vagal anti‐inflammatory reflex has emerged as an exciting therapeutic approach for chronic inflammatory diseases. However, it is unclear whether direct stimulation of the vagus or of pelvic nerves coming from sacral roots, providing the bulk of colonic parasympathetic innervation, is the best approach. We hypothesized that sacral nerve stimulation (SNS) would be an effective treatment for colitis. Age and sex‐matched Sprague‐Dawley rats were administered 5% dextran sulphate sodium (DSS) in drinking water ad libitum for 7 days. A group of rats was sacrificed after DSS treatment, and the remaining rats were randomized to either sham‐SNS or SNS groups, which were performed for 1 hr daily for 10 days. Stimulations were delivered via chronically implanted electrodes using an 8‐channel universal pulse generator. Sacral nerve stimulation promoted recovery of colitis demonstrated by decreased disease activity index, myeloperoxidase activity, tissue TNF‐alpha, and histological scores as well as an increased colonic M2 macrophage population. Heart rate variability analysis demonstrated a decrease in low frequency and increase in high frequency with SNS, corresponding to increased vagal tone. Additionally, plasma pancreatic peptide was increased and norepinephrine was decreased after SNS in colitis while colon tissue acetylcholine was increased with SNS. This is the first study to the best of our knowledge that demonstrates the benefit of SNS with autonomic mediation. SNS alters the expression of inflammatory cytokines and macrophages as well as modulates neurotransmitters involved in systemic inflammation.

IntroductionFlow describes a state of optimal experience that can promote a positive adaptation to increasing stress. The aim of the current study is to identify the ideal autonomic state for peak cognitive performance by correlating sympathovagal balance during cognitive stress with (1) perceived flow immersion and (2) executive task performance.Materials and MethodsAutonomic states were varied in healthy male participants (n = 48) using combinations of patterned breathing and skeletal muscle contraction that are known to induce differing levels of autonomic response. After autonomic variation, a Stroop test was performed on participants to induce a mild stress response, and autonomic arousal was assessed using heart rate variability. Subjective experience of flow was measured by standardized self-report, and executive task performance was measured by reaction time on the Stroop test.ResultsThere were significant associations between autonomic state and flow engagement with an inverted U-shaped function for parasympathetic stimulation, sympathetic response, and overall sympathovagal balance. There were also significant associations between autonomic states and reaction times. Combining sympathetic and parasympathetic responses to evaluate overall sympathovagal balance, there was a significant U-shaped relationship with reaction time.DiscussionOur results support the flow theory of human performance in which the ideal autonomic state lies at the peak of an inverted-U function, and extremes at either end lead to both suboptimal flow experience. Similarly, cognitive task performance was maximized at the bottom of the U-function. Our findings suggest that optimal performance may be associated with predominant, but not total, sympathetic response.

Metabolic diseases are one of the leading causes of death worldwide. Due to its lack of clinical manifestations for long periods, metabolic diseases are generally detected in advanced stages, when the risk of cardiovascular, ocular and renal complications is high. Thus, early detection of these disorders is essential to design effective health promotion strategies. Herein we provide a preliminary approach for the early diagnosis of metabolic diseases based on Principal Component Analysis (PCA) of autonomic features of sympathovagal Balance (SVB) to characterize the activity of the carotid bodies (CB). CBs are small chemoreceptors located in the bifurcation of the carotid arteries whose overactivation is intimately linked to early stages of metabolic disease through asymptomatic deregulation of the sympathetic nervous system. Herein we discuss parameters that can be extracted from these recordings using a PCA approach in response to two different challenge tests: 100% oxygen and administration of a mixed meal in healthy and type 2 diabetes volunteers. This methodology may represent a paradigm shift in the diagnosis of metabolic diseases through the characterization of CB activity, and aims to bridge the existing gap in early assessment of metabolic dysfunction. [ABSTRACT FROM AUTHOR]