Heart-rate variability: a biomarker to study the influence of nutrition on physiological and psychological health? Behav Pharmacol. 2018;29:140-151. [PMID: 29543648 PMCID: PMC5882295 DOI: 10.1097/fbp.0000000000000383]

Effects of light-intensity physical activity on cardiometabolic parameters in young adults with overweight and obesity: The SED-ACT randomized controlled crossover trial

AIMS

To investigate how a change in body position with light-intensity physical activity (PA) 'snacks' (LIPAS, alternate sitting and standing, walking or standing continuously) compared with uninterrupted prolonged sitting affects glucose metabolism and heart rate variability (HRV) parameters in young adults with overweight and obesity.

MATERIALS AND METHODS

We conducted a four-arm randomized controlled crossover trial. The following conditions were tested during an 8-h simulated workday: uninterrupted prolonged sitting (SIT), alternate sitting and standing (SIT-STAND; 2.5 h total), continuous standing (STAND), and continuous walking (1.0 mph; WALK). The primary outcome was to investigate how a change in body position (alternate sitting and standing, walking or standing continuously) compared with uninterrupted sitting affects mean 8-h glucose metabolism. Secondary outcomes included the effects on 2-h postprandial glucose concentrations, as well as on 8-h/24-h heart rate and HRV parameters, in the respective study arms. Capillary blood samples were drawn from an hyperemised earlobe in the fasted state and once every hour during each trial intervention by puncturing the earlobe with a lancet and collecting 20 μL of blood (Biosen S-Line Lab+; EKF diagnostics, Barleben, Germany). HRV was assessed for 24 h including the 8-h intervention phase, and a home phase by means of a Holter electrocardiogram. All participants received the same standardized non-relativised breakfast and lunch during the four trial visits.

RESULTS

Seventeen individuals (eight women, mean age 23.4 ± 3.3 years, body mass index 29.7 ± 3.8 kg/m2, glycated haemoglobin level 34.8 ± 3.1 mmol/mol [5.4 ± 0.3%], body fat 31.8 ± 8.2%) completed all four trial arms. Compared with SIT (89.4 ± 6.8 mg/dL), 8-h mean glucose was lower in all other conditions (p < 0.05) and this was statistically significant compared with WALK (86.3 ± 5.2 mg/dL; p = 0.034). Two-hour postprandial glucose after breakfast was approximately 7% lower for WALK compared with SIT (p = 0.002). Furthermore, significant time × condition effects on HRV parameters favouring light-intensity walking were observed (p < 0.001).

CONCLUSIONS

Replacement and interruption of prolonged sitting with light-intensity walking showed a significant blood glucose-lowering effect and improved HRV during an 8-h work environment in young adults with overweight and obesity.

Deconstructing depression by machine learning: the POKAL-PSY study

Unipolar depression is a prevalent and disabling condition, often left untreated. In the outpatient setting, general practitioners fail to recognize depression in about 50% of cases mainly due to somatic comorbidities. Given the significant economic, social, and interpersonal impact of depression and its increasing prevalence, there is a need to improve its diagnosis and treatment in outpatient care. Various efforts have been made to isolate individual biological markers for depression to streamline diagnostic and therapeutic approaches. However, the intricate and dynamic interplay between neuroinflammation, metabolic abnormalities, and relevant neurobiological correlates of depression is not yet fully understood. To address this issue, we propose a naturalistic prospective study involving outpatients with unipolar depression, individuals without depression or comorbidities, and healthy controls. In addition to clinical assessments, cardiovascular parameters, metabolic factors, and inflammatory parameters are collected. For analysis we will use conventional statistics as well as machine learning algorithms. We aim to detect relevant participant subgroups by data-driven cluster algorithms and their impact on the subjects' long-term prognosis. The POKAL-PSY study is a subproject of the research network POKAL (Predictors and Clinical Outcomes in Depressive Disorders; GRK 2621).

Measures of nutrition status and health for weight-inclusive patient care: A narrative review

In healthcare, weight is often equated to and used as a marker for health. In examining nutrition and health status, there are many more effective markers independent of weight. In this article, we review practical and emerging clinical applications of technologies and tools used to collect non-weight-related data in nutrition assessment, monitoring, and evaluation in the outpatient setting. The aim is to provide clinicians with new ideas about various types of data to evaluate and track in nutrition care.

Exploring heart rate variability in polycystic ovary syndrome: implications for cardiovascular health: a systematic review and meta-analysis

OBJECTIVES

Polycystic ovary syndrome (PCOS) is a prevalent and complex endocrine disorder that affects women of reproductive age. It has significant implications for female endocrine function, reproductive health, and metabolic disturbances, including insulin resistance, impaired glucose tolerance, and dyslipidemia. Studies have shown that decreased heart rate variability (HRV), a marker of autonomic dysfunction, is associated with adverse cardiovascular events. Recent research has focused on investigating autonomic function in PCOS, and some studies have suggested altered autonomic drive in these patients. The aim of this systematic review and meta-analysis was to evaluate cardiac autonomic function by analyzing HRV in women with PCOS.

METHODS

This systematic review was prepared using PRISMA reporting guidelines. The databases searched were PubMed, Scopus, Web of Science, and Cochrane. Risk of Bias was assessed using ROBINS-I for non-RCTs. The GRADE approach was employed to evaluate the level of certainty in the evidence for each outcome. In order to identify the underlying cause of high heterogeneity, a subgroup analysis was conducted. Sensitivity analysis was checked. A random effect model was used and calculated a pooled standardized mean difference (SMD) with a 95% confidence interval (CI).

RESULTS

Seventeen articles were included in the final analysis, varied in quality, ranging from a "low" to a "high risk of bias". Combined analyses indicated a notable decrease in HRV among individuals with PCOS compared to the control group. Significant changes were observed in SDNN (SMD: -0.763, 95%CI [-1.289 to -0.237], p=0.004), PNN50 (SMD: -1.245, 95%CI [-2.07, -0.419], p=0.003), LF/HF ratio (SMD: 0.670, 95%CI [0.248, 1.091], p=0.002), HFnu (SMD: -0.873, 95%CI [-1.257, -0.489], p=0.000), LFnu (SMD: 0.840, 95%CI [0.428, 1.251], p=0.000) and TP (SMD: -1.997, 95%CI [-3.306, -0.687], p=0.003). The heterogeneity was partially explained by types of study design. Subgroup analysis revealed significant alterations of HRV in normal-weighted and overweight PCOS cases. Conversely, no significant changes in HRV were observed in obese PCOS cases.

CONCLUSION

The findings of this meta-analysis provide evidence suggesting diminished HRV in individuals with PCOS compared to non-PCOS control group.

Reliability of an "At-Home" Method for Monitoring Resting and Reactive Autonomic Nervous System Activity in Children: A Pilot Study

BACKGROUND

Heart rate variability (HRV), an index of the functional status of the autonomic nervous system (ANS), provides an opportunity for early detection of ANS dysfunction. Lower resting, vagally related HRV parameters are associated with increased risk of physical and mental illness. External factors influencing the ANS, such as the testing environment, may impact the interpretation of HRV. This study's main aim was to determine the reliability of HRV resting and reactivity tests performed at home with children aged 4-9 years.

METHODS

Fourteen healthy children (female n = 8) aged 6.8 ± 1.5 years participated. Two HRV tests were performed at home via online supervision 7 days apart using a Polar H10 heart rate monitor. The absolute and relative reliability of the pre-exercise resting (5 min) and sub-maximal exercise step test recovery (4 × 30 s segments) HRV time and frequency domains were calculated.

RESULTS

The Pearson correlation coefficients for day 1 versus day 7 for the vagal activity HRV domains (RMSSD log) at rest and in the first 30 s and 30-60 s of recovery indicated good-to-excellent relative reliability (r > 0.8, p < 0.01). Absolute reliability was moderate for the resting RMSSD log, with a coefficient of variation (CV) of 5.2% (90% CI: 3.9, 7.8%), high for the first 30 s of standing recovery, with a CV of 10.7% (90% CI: 8.2, 15.7%), and moderate for 30-60 s of recovery, with a CV of 8.7% (90% CI: 6.6, 12.9%).

CONCLUSIONS

The findings of this pilot study indicate that the resting and exercise recovery HRV measures of vagal activity can be measured reliably at home in children. This represents a novel "at-home" protocol for monitoring ANS health and development in children.

Heart rate variability to track autonomic nervous system health in young children: Effects of physical activity and cardiometabolic risk factors

Evidence for a key role of dysregulated autonomic nervous system (ANS) activity in maladaptive stress response/recovery and non-communicable disease development is extensive. Monitoring ANS activity via regular heart rate variability (HRV) measurement is growing in popularity in adult populations given that low HRV has been associated with ANS dysregulation, poor stress response/reactivity, increased cardiometabolic disease risk and early mortality. Although cardiometabolic disease may originate in early life, regular HRV measurement for assessing ANS activity in childhood populations, especially those consisting of children < 6 years of age, remains largely unpractised. A greater understanding of ANS activity modifiers in early life may improve analysis and interpretation of HRV measurements, thereby optimising its usefulness. Taking into consideration that HRV and ANS activity can be improved via daily engagement in physical activity (PA), this review will discuss the ANS and HRV, ANS activity modifiers, cardiometabolic disease risk factors and PA as they relate to childhood/adolescent populations (≤ 18 years old).

Alignment of Consumers' Expected Brain Benefits from Food and Supplements with Measurable Cognitive Performance Tests

Consumers often cite cognitive improvements as reasons for making dietary changes or using dietary supplements, a motivation that if leveraged could greatly enhance public health. However, rarely is it considered whether standardized cognitive tests that are used in nutrition research are aligned to outcomes of interest to the consumer. This knowledge gap presents a challenge to the scientific substantiation of nutrition-based cognitive health benefits. Here we combined focus group transcript review using reflexive thematic analysis and a multidisciplinary expert panel exercise to evaluate the applicability of cognitive performance tools/tasks for substantiating the specific cognitive benefits articulated by consumers with the objectives to (1) understand how consumers comprehend the potential benefits of nutrition for brain health, and (2) determine the alignment between consumers desired brain benefits and validated tests and tools. We derived a 'Consumer Taxonomy of Cognitive and Affective Health in Nutrition Research' which describes the cognitive and affective structure from the consumers perspective. Experts agreed that validated tests exist for some consumer benefits including focused attention, sustained attention, episodic memory, energy levels, and anxiety. Prospective memory, flow, and presence represented novel benefits that require the development and validation of new tests and tools. Closing the gap between science and consumers and fostering co-creative approaches to nutrition research are critical to the development of products and dietary recommendations that support realizable cognitive benefits that benefit public health.

A comprehensive evaluation of linear and non-linear HRV parameters between paced breathing and stressful mental state

Background

Heart rate variability (HRV) is a crucial metric that provides valuable insight into the balance between relaxation and stress. Previous research has shown that most HRV parameters improve during periods of mental relaxation, while decreasing during tasks involving cognitive workload. Although a comprehensive analysis of both linear and non-linear HRV parameters has been carried out in existing literature, there still exists a need for further research in this area. Additionally, limited knowledge exists regarding how specific interventions may influence the interpretation of these parameters and how the different parameters correlate under different interventions. This study aims to address these gaps by conducting a thorough comparison of different linear and non-linear HRV parameters under mentally relaxed versus stressful states.

Methodology

Participants were randomly and equally divided among two between-subjects groups: relaxed-stress (RS) (N = 22) and stress-relaxed (SR) (N = 22). In the RS group, a paced breathing task was given for 5 min to create relaxation, and was followed by a 5-min time-based mental calculation task to create stress. In the SR group, the order of the stress and relaxed tasks was reversed. There was a washout period of 15 min after the first task in both groups.

Results

Of the 37 HRV parameters, 33 differed significantly between the two interventions. The majority of the parameters exhibited an improving and degrading tendency of HRV parameters in the relaxed and stressed states, respectively. The correlation of the majority of HRV parameters decreases during stress, while prominent time domain and geometric domain parameters stand out in the correlation.

Conclusion

Overall, HRV parameters can be reliably used to assess a person's relaxed and stressed mental states during paced breathing and mental arithmetic task respectively. Furthermore, non-linear HRV parameters provide accurate estimators of the mental state, in addition to the commonly used linear parameters.

Sympathovagal quotient and resting-state functional connectivity of control networks are related to gut Ruminococcaceae abundance in healthy men

INTRODUCTION

Heart rate variability (HRV), brain resting-state functional connectivity (rsFC), and gut microbiota (GM) are three recognized indicators of health status, whose relationship has not been characterized. We aimed to identify the GM genera and families related to HRV and rsFC, the interaction effect of HRV and rsFC on GM taxa abundance, and the mediation effect of diet on these relationships.

METHODS

Eighty-eight healthy, young Colombian men were included in this cross-sectional study. HRV metrics were extracted from 24-hour Holter monitoring data and the resting functional connectivity strength (FCS) of 15 networks were derived from functional magnetic resonance imaging. Gut microbiota composition was assessed using the sequences of the V3-V4 regions of the 16 S rRNA gene, and diet was evaluated using a food frequency questionnaire. Multivariate linear regression analyses were performed to evaluate the correlations between the independent variables (HRV metrics and FCS) and the dependent variables (GM taxa abundance or alpha diversity indexes). Mediation analyses were used to test the role of diet in the relationship between HRV and GM.

RESULTS

The sympathovagal quotient (SQ) and the FCS of control networks were positively correlated with the abundance of the gut Ruminococcaceae family and an unclassified Ruminococcaceae genus (Ruminococcaceae_unc). Additionally, the interaction between the FCS of the control network and SQ reduced the individual main effects on the Ruminococcaceae_unc abundance. Finally, reduced habitual fiber intake partially mediated the relationship between SQ and this genus.

CONCLUSION

Two indicators of self-regulation, HRV and the rsFC of control networks, are related to the abundance of gut microbiota taxa in healthy men. However, only HRV is related to habitual dietary intake; thus, HRV could serve as a marker of food choice and GM composition in the future.

Electrophysiological Characteristics of Inhibitive Control for Adults with Different Physiological or Psychological Obesity

Individuals exhibiting high scores on the fatness subscale of the negative-physical-self scale (NPSS-F) are characterized by heightened preoccupation with body fat accompanied by negative body image perceptions, often leading to excessive dieting behaviors. This demographic constitutes a considerable segment of the populace in China, even among those who are not obese. Nonetheless, scant empirical inquiries have delved into the behavioral and neurophysiological profiles of individuals possessing a healthy body mass index (BMI) alongside elevated NPSS-F scores. This study employed an experimental paradigm integrating go/no-go and one-back tasks to assess inhibitory control and working memory capacities concerning food-related stimuli across three adult cohorts: those with normal weight and low NPSS-F scores, those with normal weight and high NPSS-F scores, and individuals classified as obese. Experimental stimuli comprised high- and low-caloric-food pictures with concurrent electroencephalogram (EEG) and photoplethysmogram (PPG) recordings. Individuals characterized by high NPSS-F scores and normal weight exhibited distinctive electrophysiological responses compared to the other two cohorts, evident in event-related potential (ERP) components, theta and alpha band oscillations, and heart rate variability (HRV) patterns. In essence, the findings underscore alterations in electrophysiological reactivity among individuals possessing high NPSS-F scores and a healthy BMI in the context of food-related stimuli, underscoring the necessity for increased attention to this demographic alongside individuals affected by obesity.

Refractory Autonomic Instability in Mild Traumatic Brain Injury: A Case Report

Although the specific relationship between concussion and the autonomic nervous system (ANS) has not been fully elucidated, it is generally understood that the pathologic response after a traumatic brain injury (TBI) is linked with systolic cardiac dysfunction. In this case, we present a patient with multiple concussion injuries over a five-year period who exhibited severe cardiac and autonomic dysfunction, in addition to prolonged impairments in vestibular function, oculomotor function, cognitive function, and headaches. The patient is a 28-year-old male with a past medical history of multiple concussions, with the first concussion occurring due to a skiing accident in January 2015. He initially presented in October 2016 after sustaining a concussion due to a motor vehicle accident (MVA) without loss of consciousness (LOC) two weeks prior. In July 2017, the patient was involved in another MVA with a positive head strike and without LOC, causing his third concussion. After each of his first three concussions, he displayed various symptoms that eventually resolved. In October 2020, the patient suffered a syncopal ground-level fall with several minutes of LOC due to dehydration and lightheadedness, leading to his fourth concussion. His fourth concussion resulted in chronic autonomic dysfunction with resting tachycardia refractory to medical management, and he eventually underwent a cardiac ablation. Although the patient underwent a cardiac ablation, his tachycardia and dysautonomia still cause dysfunction in his daily life. With millions of people living with the sequelae of TBI, the recognition and treatment of autonomic dysfunction should be a continued focus in brain injury research.

Dynamic vagal-mediated connectivity of cortical and subcortical central autonomic hubs predicts chronotropic response to submaximal exercise in healthy adults

BACKGROUND

Despite accumulation of a substantial body of literature supporting the role of exercise on frontal lobe functioning, relatively less is understood of the interconnectivity of ventromedial prefrontal cortical (vmPFC) regions that underpin cardio-autonomic regulation predict cardiac chronotropic competence (CC) in response to sub-maximal exercise.

METHODS

Eligibility of 161 adults (mean age = 48.6, SD = 18.3, 68% female) was based upon completion of resting state brain scan and sub-maximal bike test. Sliding window analysis of the resting state signal was conducted over 45-s windows, with 50% overlap, to assess how changes in photoplethysmography-derived HRV relate to vmPFC functional connectivity with the whole brain. CC was assessed based upon heart rate (HR) changes during submaximal exercise (HR change /HRmax (206-0.88 × age) - HRrest).

RESULTS

During states of elevated HRV the vmPFC showed greater rsFC with an 83-voxel region of the hypothalamus (p < 0.001, uncorrected). Beta estimates of vmPFC connectivity extracted from a 6-mm sphere around this region emerged as the strongest predictor of CC (b = 0.283, p <.001) than age, BMI, and resting HRV F(8,144) = 6.30, p <.001.

CONCLUSION

Extensive glutamatergic innervation of the hypothalamus by the vmPFC allows for top-down control of the hypothalamus and its various autonomic efferents which facilitate chronotropic response during sub-maximal exercise.

How to properly evaluate cardiac vagal tone in oncology studies: a state-of-the-art review

Heart rate variability (HRV) analysis provides an assessment of cardiac vagal tone and consequently global cardiac health as well as systemic condition. In systemic diseases such as cancer and during treatments that affect the whole body, like chemotherapy, the vagus nerve activity is low and deregulated. Some studies focus on using HRV to predict mortality in oncology. However, in cancer patients, systemic alterations substantially increase artifacts during HRV measurement, especially atrial ectopic beats. Moreover, HRV may be altered by various factors (duration and time of measurement, breathing, drugs, and other confounding factors) that alter each metric in different ways. The Standard Deviation of all Normal to Normal intervals (SDNN) is the most commonly used metric to evaluate HRV in oncology, but it does not appear to be specific to the cardiac vagal tone. Thus, cardiac vagal activity diagnosis and vital prognosis of cancer patients can be biased. Our review presents the main HRV metrics that can be currently used in oncology studies and their links with vagus nerve and cancer. We present the influence of external factors and the required duration and time of measurement. Considering all these parameters, this review proposes seven key points for an assessment of HRV and cardiac vagal tone in patients with cancer.

Time-domain heart rate variability features for automatic congestive heart failure prediction

AIMS

Heart failure is a serious condition that often goes undiagnosed in primary care due to the lack of reliable diagnostic tools and the similarity of its symptoms with other diseases. Non-invasive monitoring of heart rate variability (HRV), which reflects the activity of the autonomic nervous system, could offer a novel and accurate way to detect and manage heart failure patients. This study aimed to assess the feasibility of using machine learning techniques on HRV data as a non-invasive biomarker to classify healthy adults and those with heart failure.

METHODS AND RESULTS

We used digitized electrocardiogram recordings from 54 adults with normal sinus rhythm and 44 adults categorized into New York Heart Association classes 1, 2, and 3, suffering from congestive heart failure. All recordings were sourced from the PhysioNet database. Following data pre-processing, we performed time-domain HRV analysis on all individual recordings, including root mean square of the successive difference in adjacent RR interval (RRi) (RMSSD), the standard deviation of RRi (SDNN, the NN stands for natural or sinus intervals), the standard deviation of the successive differences between successive RRi (SDSD), the number or percentage of RRi longer than 50 ms (NN50 and pNN50), and the average value of RRi [mean RR interval (mRRi)]. In our experimental classification performance evaluation, on the computed HRV parameters, we optimized hyperparameters and performed five-fold cross-validation using four machine learning classification algorithms: support vector machine, k-nearest neighbour (KNN), naïve Bayes, and decision tree (DT). We evaluated the prediction accuracy of these models using performance criteria, namely, precision, recall, specificity, F1 score, and overall accuracy. For added insight, we also presented receiver operating characteristic (ROC) plots and area under the ROC curve (AUC) values. The overall best performance accuracy of 77% was achieved when KNN and DT were trained on computed HRV parameters with a 5 min time window. KNN obtained an AUC of 0.77, while DT attained 0.78. Additionally, in the classification of severe congestive heart failure, KNN and DT had the best accuracy of 91%, with KNN achieving an AUC of 0.88 and DT obtaining 0.92.

CONCLUSIONS

The results show that HRV can accurately predict severe congestive heart failure. The findings of this study could inform the use of machine learning approaches on non-invasive HRV, to screen congestive heart failure individuals in primary care.

Wearable-derived maternal heart rate variability as a novel digital biomarker of preterm birth

Despite considerable health consequences from preterm births, their incidence remains unchanged over recent decades, due partially to limited screening methods and limited use of extant methods. Wearable technology offers a novel, noninvasive, and acceptable way to track vital signs, such as maternal heart rate variability (mHRV). Previous research observed that mHRV declines throughout the first 33 weeks of gestation in term, singleton pregnancies, after which it improves. The aim of this study was to explore whether mHRV inflection is a feature of gestational age or an indication of time to delivery. This retrospective case-control study considered term and preterm deliveries. Remote data collection via non-invasive wearable technology enabled diverse participation with subjects representing 42 US states and 16 countries. Participants (N = 241) were retroactively identified from the WHOOP (Whoop, Inc.) userbase and wore WHOOP straps during singleton pregnancies between March 2021 and October 2022. Mixed effect spline models by gestational age and time until birth were fit for within-person mHRV, grouped into preterm and term births. For term pregnancies, gestational age (Akaike information criterion (AIC) = 26627.6, R2m = 0.0109, R2c = 0.8571) and weeks until birth (AIC = 26616.3, R2m = 0.0112, R2c = 0.8576) were representative of mHRV trends, with significantly stronger fit for weeks until birth (relative log-likelihood ratio = 279.5). For preterm pregnancies, gestational age (AIC = 1861.9, R2m = 0.0016, R2c = 0.8582) and time until birth (AIC = 1848.0, R2m = 0.0100, R2c = 0.8676) were representative of mHRV trends, with significantly stronger fit for weeks until birth (relative log-likelihood ratio = 859.4). This study suggests that wearable technology, such as the WHOOP strap, may provide a digital biomarker for preterm delivery by screening for changes in nighttime mHRV throughout pregnancy that could in turn alert to the need for further evaluation and intervention.

Heart rate variability and cardiovascular diseases: A Mendelian randomization study

BACKGROUND

The causal relationship between heart rate variability and cardiovascular diseases and the associated events is still unclear, and the conclusions of current studies are inconsistent. We aimed to explore the relationship between heart rate variability and cardiovascular diseases and the associated events with the Mendelian randomization study.

METHODS

We selected normal-to-normal inter-beat intervals (SDNN), root mean square of the successive differences of inter-beat intervals (RMSSD) and peak-valley respiratory sinus arrhythmia or high-frequency power (pvRSA/HF) as the three sets of instrumental variables for heart rate variability. The outcome for cardiovascular diseases included essential hypertension, heart failure, angina pectoris, myocardial infarction, nonischemic cardiomyopathy and arrhythmia. Cardiac arrest, cardiac death and major coronary heart disease event were defined as the related events of cardiovascular diseases. The data for exposures and outcomes were derived from publicly available genome-wide association studies. Inverse variance weighted was used for the main causal estimation. Analyses of heterogeneity and pleiotropy were conducted using the Cochran Q test of Inverse variance weighted and MR-Egger, leave-one-out analysis, and MR-Pleiotropy Residual Sum and Outlier methods.

RESULTS

The Inverse variance weighted method indicated that genetically predicted pvRSA/HF was associated with the increased risk of cardiac arrest (odds ratio 2.02, 95% confidence interval 1.25-3.28, p = .004). The results were free of heterogeneity and pleiotropy. There were no outliers and the leave-one-out analysis proved that the results were reliable.

CONCLUSIONS

This study provides genetic evidence that pvRSA/HF is causally related to cardiac arrest.

HEART Rate Variability Biofeedback for LOng COVID Dysautonomia (HEARTLOC): Results of a Feasibility Study

Introduction

Post-COVID-19 syndrome, or Long Covid (LC) refers to symptoms persisting 12 weeks after the COVID-19 infection. LC comprises a wide range of dysautonomia symptoms, including fatigue, breathlessness, palpitations, dizziness, pain and brain fog. This study tested the feasibility and estimated the efficacy, of a Heart Rate Variability Biofeedback (HRV-B) programme via a standardised slow diaphragmatic breathing technique in individuals with LC.

Methods

LC patients underwent a 4-week HRV-B intervention for 10 minutes twice daily for 4 weeks using the Polar H10 ECG (Electrocardiogram) chest strap and Elite HRV phone application. Outcome measures C19-YRSm (Yorkshire Rehabilitation Scale modified), Composite Autonomic Symptom Score (COMPASS-31), WHO Disability Assessment Schedule (WHODAS), EQ5D-5L (EuroQol 5 Dimensions) and Root Mean Square of Successive Differences between heartbeats (RMSSD) using a Fitbit device were recorded before and after the intervention. The study was pre-registered at clinicaltrials.gov NCT05228665.

Results

A total of 13 participants (54% female, 46% male) completed the study with high levels of independent use of technology, data completeness and intervention adherence. There was a statistically significant improvement in C19YRS-m (P = .001), COMPASS-31 (P = .007), RMSSD (P = .047), WHODAS (P = .02) and EQ5D Global Health Score (P = .009). Qualitative feedback suggested participants could use it independently, were satisfied with the intervention and reported beneficial effects from the intervention.

Conclusion

HRV-B using diaphragmatic breathing is a feasible intervention for LC. The small sample size limits generalisability. HRV-B in LC warrants further exploration in a larger randomised controlled study.

Prediction of fetal RR intervals from maternal factors using machine learning models

Previous literature has highlighted the importance of maternal behavior during the prenatal period for the upbringing of healthy adults. During pregnancy, fetal health assessments are mainly carried out non-invasively by monitoring fetal growth and heart rate (HR) or RR interval (RRI). Despite this, research entailing prediction of fHRs from mHRs is scarce mainly due to the difficulty in non-invasive measurements of fetal electrocardiogram (fECG). Also, so far, it is unknown how mHRs are associated with fHR over the short term. In this study, we used two machine learning models, support vector regression (SVR) and random forest (RF), for predicting average fetal RRI (fRRI). The predicted fRRI values were compared with actual fRRI values calculated from non-invasive fECG. fRRI was predicted from 13 maternal features that consisted of age, weight, and non-invasive ECG-derived parameters that included HR variability (HRV) and R wave amplitude variability. 156 records were used for training the models and the results showed that the SVR model outperformed the RF model with a root mean square error (RMSE) of 29 ms and an average error percentage (< 5%). Correlation analysis between predicted and actual fRRI values showed that the Spearman coefficient for the SVR and RF models were 0.31 (P < 0.001) and 0.19 (P < 0.05), respectively. The SVR model was further used to predict fRRI of 14 subjects who were not included in the training. The latter prediction results showed that individual error percentages were (≤ 5%) except in 3 subjects. The results of this study show that maternal factors can be potentially used for the assessment of fetal well-being based on fetal HR or RRI.

Short-term exposure to ultrafine and fine particulate matter with multipollutant modelling on heart rate variability among seniors and children from the CorPuScula (coronary, pulmonary, sanguis) longitudinal study in Germany

Background

Short-term exposure particulate matter with a diameter of 10 µm or less (PM10) and fine particulate matter (PM2.5) has been associated with heart rate variability (HRV), but exposure to ultrafine particles (UFP) has been less well examined. We investigated the associations between the HRV outcomes and short-term exposure to UFP, PM10 and PM2.5 among school-aged children and seniors.

Methods

CorPuScula (Coronary, Pulmonary and Sanguis) is a longitudinal, repeated-measure panel study conducted in 2000-2002 in Munich, Germany including 52 seniors (58-94 years old) with 899 observations and 50 children (6-10 years old) with 925 observations. A 10-min resting electrocardiogram was performed to assess resting HRV outcomes [Standard Deviation of Normal to Normal Intervals (SDNN), Root Mean Square of Successive Differences between Normal Heartbeats (RMSSD), Low Frequency power (LF), High Frequency power (HF), ration between low and high frequency (LF/HF)]. UFP and PM exposures were measured near the care home and school yard for seniors and children, respectively. Mean exposures during the day of examination (9-21 h) as well as 3-h, 12-h, 24-h, one-day, and two-day lags were assessed. Linear mixed-effect models were used to investigate the associations between short-term air pollution and HRV outcomes separately in children and seniors. The models were adjusted for sex, age, weather conditions (temperature, precipitation, and water vapor pressure), BMI, lifestyle and medical information. Two and multipollutant models adjusted for NO2 and O3 were performed.

Results

Among seniors, we observed increases in SDNN, LF, HF and LF/HF ratio after short-term exposure to UFP (hourly and daily lags) in contrast to decreases in SDNN and RMSSD after exposure to PM10. Associations were generally robust to two- and multipollutant adjustment. Among children, we observed increases of the LF/HF ratio after short-term exposures to UFP at lags 12 and 24 h. In contrast, we observed decreases of the ratio after exposure to PM2.5 and PM10. Results were largely unchanged for multipollutant modelling, however we found a more pronounced increase in SDNN and LF/HF (UFP lag 12 and 24 h) after adjusting for NO2.

Conclusions

Overall, among seniors, we observed associations of UFP and PM10 exposure with sympathetic responses of the ANS, which play an important role in sudden heart attacks or arrhythmia. Among children we found more inconsistent associations between UFP and a delayed increase in HRV. Adjusting for co-pollutants including NO2 and O3 yielded robust results.

Methods for Heart Rate Variability Biofeedback (HRVB): A Systematic Review and Guidelines

Heart Rate Variability Biofeedback (HRVB) has been widely used to improve cardiovascular health and well-being. HRVB is based on breathing at an individual's resonance frequency, which stimulates respiratory sinus arrhythmia (RSA) and the baroreflex. There is, however, no methodological consensus on how to apply HRVB, while details about the protocol used are often not well reported. Thus, the objectives of this systematic review are to describe the different HRVB protocols and detect methodological concerns. PsycINFO, CINALH, Medline and Web of Science were searched between 2000 and April 2021. Data extraction and quality assessment were based on PRISMA guidelines. A total of 143 studies were finally included from any scientific field and any type of sample. Three protocols for HRVB were found: (i) "Optimal RF" (n = 37), each participant breathes at their previously detected RF; (ii) "Individual RF" (n = 48), each participant follows a biofeedback device that shows the optimal breathing rate based on cardiovascular data in real time, and (iii) "Preset-pace RF" (n = 51), all participants breathe at the same rate rate, usually 6 breaths/minute. In addition, we found several methodological differences for applying HRVB in terms of number of weeks, duration of breathing or combination of laboratory and home sessions. Remarkably, almost 2/3 of the studies did not report enough information to replicate the HRVB protocol in terms of breathing duration, inhalation/exhalation ratio, breathing control or body position. Methodological guidelines and a checklist are proposed to enhance the methodological quality of future HRVB studies and increase the information reported.

The application of virtual reality exposure versus relaxation training in music performance anxiety: a randomized controlled study

BACKGROUND

Performance anxiety is the most frequently reported anxiety disorder among professional musicians. Typical symptoms are - on a physical level - the consequences of an increase in sympathetic tone with cardiac stress, such as acceleration of heartbeat, increase in blood pressure, increased respiratory rate and tremor up to nausea or flush reactions. These symptoms can cause emotional distress, a reduced musical and artistical performance up to an impaired functioning. While anxiety disorders are preferably treated using cognitive-behavioral therapy with exposure, this approach is rather difficult for treating music performance anxiety since the presence of a public or professional jury is required and not easily available. The use of virtual reality (VR) could therefore display an alternative. So far, no therapy studies on music performance anxiety applying virtual reality exposure therapy have investigated the therapy outcome including cardiovascular changes as outcome parameters.

METHODS

This mono-center, prospective, randomized and controlled clinical trial has a pre-post design with a follow-up period of 6 months. 46 professional and semi-professional musicians will be recruited and allocated randomly to an VR exposure group or a control group receiving progressive muscle relaxation training. Both groups will be treated over 4 single sessions. Music performance anxiety will be diagnosed based on a clinical interview using ICD-10 and DSM-5 criteria for specific phobia or social anxiety. A behavioral assessment test is conducted three times (pre, post, follow-up) in VR through an audition in a concert hall. Primary outcomes are the changes in music performance anxiety measured by the German Bühnenangstfragebogen and the cardiovascular reactivity reflected by heart rate variability (HRV). Secondary outcomes are changes in blood pressure, stress parameters such as cortisol in the blood and saliva, neuropeptides, and DNA-methylation.

DISCUSSION

The trial investigates the effect of VR exposure in musicians with performance anxiety compared to a relaxation technique on anxiety symptoms and corresponding cardiovascular parameters. We expect a reduction of anxiety but also a consecutive improvement of HRV with cardiovascular protective effects.

TRIAL REGISTRATION

This study was registered on clinicaltrials.gov. (ClinicalTrials.gov Number: NCT05735860).

Signal Quality Analysis of Single-Arm Electrocardiography

The number of people experiencing mental stress or emotional dysfunction has increased since the onset of the COVID-19 pandemic, as many individuals have had to adapt their daily lives. Numerous studies have demonstrated that mental health disorders can pose a risk for certain diseases, and they are also closely associated with the problem of mental workload. Now, wearable devices and mobile health applications are being utilized to monitor and assess individuals' mental health conditions on a daily basis using heart rate variability (HRV), typically measured by the R-to-R wave interval (RRI) of an electrocardiogram (ECG). However, portable or wearable ECG devices generally require two electrodes to perform bipolar limb leads, such as the Einthoven triangle. This study aims to develop a single-arm ECG measurement method, with lead I ECG serving as the gold standard. We conducted static and dynamic experiments to analyze the morphological performance and signal-to-noise ratio (SNR) of the single-arm ECG. Three morphological features were defined, RRI, the duration of the QRS complex wave, and the amplitude of the R wave. Thirty subjects participated in this study. The results indicated that RRI exhibited the highest cross-correlation (R = 0.9942) between the single-arm ECG and lead I ECG, while the duration of the QRS complex wave showed the weakest cross-correlation (R = 0.2201). The best SNR obtained was 26.1 ± 5.9 dB during the resting experiment, whereas the worst SNR was 12.5 ± 5.1 dB during the raising and lowering of the arm along the z-axis. This single-arm ECG measurement method offers easier operation compared to traditional ECG measurement techniques, making it applicable for HRV measurement and the detection of an irregular RRI.

Predicting Therapeutic Efficacy of Pharmacological Treatments in Children with Postural Orthostatic Tachycardia Syndrome: A Mini-Review

Postural orthostatic tachycardia syndrome (POTS) is common in children, with an excessive increment in heart rate when moving from the supine to upright position. It has significant negative impacts on the daily life of pediatric patients. The pathogenesis of POTS includes peripheral vascular dysfunction, central hypovolemia, abnormal autonomic function, a high-adrenergic state, impaired skeletal-muscle pump function, the abnormal release of vasoactive factors, and autoimmune abnormalities. Therefore, the empirical use of pharmacological treatments has limited therapeutic efficacy due to the diversity of its mechanisms. A crucial aspect of managing POTS is the selection of appropriate treatment targeting the specific pathogenesis. This review summarizes the commonly used pharmacological interventions, with a focus on their predictive indicators for treatment response. Factors such as heart rate variability, plasma biomarkers, and cardiac-function parameters are discussed as potential predictors of therapeutic efficacy, enabling the implementation of individualized treatment to improve therapeutic effectiveness. This review consolidates the current knowledge on POTS, encompassing its clinical characteristics, epidemiological patterns, underlying pathogenic mechanisms, and predictive indicators for treatment response. Further research is warranted to enhance the understanding of POTS and facilitate the development of more effective therapeutic approaches for this challenging syndrome.

Short-term effects of a maqui-based nutraceutical on heart rate variability, psycho-physical resilience and on a few metabolic biomarkers: a randomized controlled study

OBJECTIVES

To assess the immediate/short-term outcomes of a maqui berry-based nutraceutical (MBN) supplementation on the autonomic nervous system (ANS), resilience level, metabolism and body composition.

METHODS

A randomized controlled single-blind study was performed on healthy subjects. Throughout 30 days, one group took 1,000 mg/day of an MBN (Maqui 500^®), the control group had no supplementation. On day 0 (T0) and 30 (T3) all subjects performed blood tests, bioimpedance spectroscopy and questionnaires for resilience, perceived stress and short-form 12 (SF12). At T0, 75' after T0 (T1), on day 7 and at T3 the subjects underwent biometric parameter measurement and heart rate variability (HRV) test to investigate psycho-physical resilience.

RESULTS

Fifteen subjects per group were included; abnormal seasonal high temperatures altered individuals' lifestyle and nutrition, influencing the trial's outcomes. Biometric parameters, blood pressure, oxygen saturation and blood tests did not differ between T0 and T3 in both groups. In the MBN group the HRV analysis showed a significant increase of ANS coordination (p=0.05), parasympathetic activity at 75', very low frequencies and total power at T3, whereas these parameters decreased in the control group. SF12 mental score improved in the maqui group (p=0.02); the questionnaire-based outcomes showed no further variations. In the control subjects bioimpedance showed an increase of resistance and fat mass, with decreased total body water and lean mass (p=n.s.).

CONCLUSIONS

The maqui-based nutraceutical improved HRV, namely ANS activation/coordination, and SF12 mental component. Blood tests and bioimpedance/biometric parameters mildly varied. The elapsed hot weather likely biased many investigated variables.

Short-term high-salt consumption does not influence resting or exercising heart rate variability but increases MCP-1 concentration in healthy young adults

High salt consumption increases blood pressure (BP) and cardiovascular disease risk by altering autonomic function and increasing inflammation. However, it is unclear whether salt manipulation alters resting and exercising heart rate variability (HRV), a noninvasive measure of autonomic function, in healthy young adults. The purpose of this investigation was to determine whether short-term high-salt intake 1) alters HRV at rest, during exercise, or exercise recovery and 2) increases the circulating concentration of the inflammatory biomarker monocyte chemoattractant protein 1 (MCP-1). With the use of a randomized, placebo-controlled, crossover study, 20 participants (8 females; 24 ± 4 yr old, 110 ± 10/64 ± 8 mmHg) consumed salt (3,900 mg sodium) or placebo capsules for 10 days each separated by ≥2 wk. We assessed HRV during 10 min of baseline rest, 50 min of cycling (60% V̇o2peak), and recovery. We quantified HRV using the standard deviation of normal-to-normal RR intervals, the root mean square of successive differences (RMSSD), and additional time and frequency domain metrics of HRV. Plasma samples were collected to assess MCP-1 concentration. No main effect of high salt or condition × time interaction was observed for HRV metrics. However, acute exercise reduced HRV (e.g., RMSSD time: P < 0.001, condition: P = 0.877, interaction: P = 0.422). High salt elevated plasma MCP-1 (72.4 ± 12.5 vs. 78.14 ± 14.7 pg/mL; P = 0.010). Irrespective of condition, MCP-1 was moderately associated (P values < 0.05) with systolic (r = 0.32) and mean BP (r = 0.33). Short-term high-salt consumption does not affect HRV; however, it increases circulating MCP-1, which may influence BP in young adults.

Electromagnetic fields - do they pose a cardiovascular risk?

Mobile wireless communication technologies have now become an everyday part of our lives, 24 hours a day, 7 days a week. Monitoring the autonomous system under exposition to electromagnetic fields may play an important role in broading of our still limited knowledge on their effect on human body. Thus, we studied the interaction of the high frequency electromagnetic field (HF EMF) with living body and its effect on the autonomic control of heart rate using Heart Rate Variability (HRV) linear and nonlinear analyses in healthy volunteers. A group of young healthy probands (n=30, age mean: 24.2 ± 3.5 years) without any symptoms of disease was exposed to EMF with f=2400 MHz (Wi Fi), and f=2600 MHz (4G) for 5 minutes applied on the chest area. The short-term heart rate variability (HRV) metrics were used as an indicator of complex cardiac autonomic control. The evaluated HRV parameters: RR interval (ms), high frequency spectral power (HF-HRV in [ln(ms2)]) as an index of cardiovagal control, and a symbolic dynamic index of 0V %, indicating cardiac sympathetic activity. The cardiac-linked parasympathetic index HF-HRV was significantly reduced (p =0.036) and sympathetically mediated HRV index 0V % was significantly higher (p=0.002) during EMF exposure at 2400 MHz (Wi-Fi), compared to simulated 4G frequency 2600 MHz. No significant differences were found in the RR intervals. Our results revealed a shift in cardiac autonomic regulation towards sympathetic overactivity and parasympathetic underactivity indexed by HRV parameters during EMF exposure in young healthy persons. It seems that HF EMF exposure results in abnormal complex cardiac autonomic regulatory integrity which may be associated with higher risk of later cardiovascular complications already in healthy probands.

Is the Effect of the COVID-19 Vaccine on Heart Rate Variability Permanent?

Background and Objectives: The risk of autonomic dysfunction with COVID-19 vaccines used worldwide in the COVID-19 pandemic remains a topic of debate. Heart rate variability has a number of parameters that can be used to assess autonomic nervous system dynamics. The aim of this study was to investigate the effect of a COVID-19 vaccine (Pfizer-BioNTech) on heart rate variability and autonomic nervous system parameters, and the duration of the effect. Materials and Methods: A total of 75 healthy individuals who visited an outpatient clinic to receive the COVID-19 vaccination were included in this prospective observational study. Heart rate variability parameters were measured before vaccination and on days 2 and 10 after vaccination. SDNN, rMSSD and pNN50 values were evaluated for time series analyses, and LF, HF, and LF/HV values for frequency-dependent analyses. Results: The SDNN and rMSDD values declined significantly on day 2 after vaccination, while the pNN50 and LF/HF values increased significantly on day 10. The values at pre-vaccination and at day 10 were comparable. The pNN50 and LF/HF values declined significantly on day 2 and increased significantly on day 10. The values at pre-vaccination and at day 10 were comparable. Conclusions: This study showed that the decline in HRV observed with COVID-19 vaccination was temporary, and that the Pfizer-BioNTech COVID-19 vaccination did not cause permanent autonomic dysfunction.

Sex differences in post-exercise fatigue and function in myalgic encephalomyelitis/chronic fatigue syndrome

To assess biobehavioral sex differences in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) utilizing a low burden exercise protocol, 22 females and 15 males with ME/CFS and 14 healthy controls underwent two six-min walk tests. Fifteen daily assessments were scheduled for fatigue and function ratings and heart monitoring. Six-min walk tests were conducted on days 8 and 9. The ME/CFS group showed high self-report fatigue and impaired physical function, whereas healthy controls did not show fatigue or function abnormalities. In patients, no significant post-exercise changes were found for heart rate variability (HRV); however, heart rate decreased in ME/CFS males from Day 14 to Day 15 (p = 0.046). Female patients showed increased fatigue (p = 0.006) after the initial walk test, but a downward slope (p = 0.008) in fatigue following the second walk test. Male patients showed a decrease in self-report work limitation in the days after exercise (p = 0.046). The healthy control group evidenced a decrease in HRV after the walk tests from Day 9-14 (p = 0.038). This pilot study did not confirm hypotheses that females as compared to males would show slower exercise recovery on autonomic or self-report (e.g. fatigue) measures. A more exertion-sensitive test may be required to document prolonged post-exertional abnormalities in ME/CFS.Trial registration: NCT NCT03331419.

Exploring the use of Granger causality for the identification of chemical exposure based on physiological data

Wearable sensors offer new opportunities for the early detection and identification of toxic chemicals in situations where medical evaluation is not immediately possible. We previously found that continuously recorded physiology in guinea pigs can be used for early detection of exposure to an opioid (fentanyl) or a nerve agent (VX), as well as for differentiating between the two. Here, we investigated how exposure to these different chemicals affects the interactions between ECG and respiration parameters as determined by Granger causality (GC). Features reflecting such interactions may provide additional information and improve models differentiating between chemical agents. Traditional respiration and ECG features, as well as GC features, were extracted from data of 120 guinea pigs exposed to VX (n = 61) or fentanyl (n = 59). Data were divided in a training set (n = 99) and a test set (n = 21). Minimum Redundancy Maximum Relevance (mRMR) and Support Vector Machine (SVM) algorithms were used to, respectively, perform feature selection and train a model to discriminate between the two chemicals. We found that ECG and respiration parameters are Granger-related under healthy conditions, and that exposure to fentanyl and VX affected these relationships in different ways. SVM models discriminated between chemicals with accuracy of 95% or higher on the test set. GC features did not improve the classification compared to traditional features. Respiration features (i.e., peak inspiratory and expiratory flow) were the most important to discriminate between different chemical’s exposure. Our results indicate that it may be feasible to discriminate between chemical exposure when using traditional physiological respiration features from wearable sensors. Future research will examine whether GC features can contribute to robust detection and differentiation between chemicals when considering other factors, such as generalizing results across species.

Cross Dataset Analysis for Generalizability of HRV-Based Stress Detection Models

Stress is an increasingly prevalent mental health condition across the world. In Europe, for example, stress is considered one of the most common health problems, and over USD 300 billion are spent on stress treatments annually. Therefore, monitoring, identification and prevention of stress are of the utmost importance. While most stress monitoring is carried out through self-reporting, there are now several studies on stress detection from physiological signals using Artificial Intelligence algorithms. However, the generalizability of these models is only rarely discussed. The main goal of this work is to provide a monitoring proof-of-concept tool exploring the generalization capabilities of Heart Rate Variability-based machine learning models. To this end, two Machine Learning models are used, Logistic Regression and Random Forest to analyze and classify stress in two datasets differing in terms of protocol, stressors and recording devices. First, the models are evaluated using leave-one-subject-out cross-validation with train and test samples from the same dataset. Next, a cross-dataset validation of the models is performed, that is, leave-one-subject-out models trained on a Multi-modal Dataset for Real-time, Continuous Stress Detection from Physiological Signals dataset and validated using the University of Waterloo stress dataset. While both logistic regression and random forest models achieve good classification results in the independent dataset analysis, the random forest model demonstrates better generalization capabilities with a stable F1 score of 61%. This indicates that the random forest can be used to generalize HRV-based stress detection models, which can lead to better analyses in the mental health and medical research field through training and integrating different models.

Supplementation with okra combined or not with exercise training is able to protect the heart of animals with metabolic syndrome

The metabolic syndrome (MetS) is a clinical manifestation strongly associated with cardiovascular disease, the main cause of death worldwide. In view of this scenario, many therapeutic proposals have appeared in order to optimize the treatment of individuals with MetS, including the practice of exercise training (ET) and the consumption of okra (O). The aim of the present study was to evaluate the effect of O consumption and/or ET in animals with MetS. In all, 32 male Zucker rats (fa/fa) at 10 weeks old were randomly distributed into four groups of 8 animals each: MetS, MetS+O, MetS+ET and MetS+ET+O, and 8 lean Zucker rats (fa/ +) comprised the control group. Okra was administered by orogastric gavage 2x/day (morning and night, 100 mg/kg), 5 days/week, for 6 weeks. The ET was performed on a treadmill 1x/day (afternoon), 5 days/week, 60 min/day, in an intensity of 70% of maximal capacity, for the same days of O treatment. It was found that, O consumption alone was able to promote improved insulin sensitivity (MetS 93.93 ± 8.54 mg/dL vs. MetS+O 69.95 ± 18.7 mg/dL, p ≤ 0.05, d = 1.65, CI = 50.32 -89.58, triglyceride reduction (MetS 492.9 ± 97.8 mg/dL vs. MetS+O 334.9 ± 98.0 mg/dL, p ≤ 0.05, d = 1.61, CI = 193.2-398.7). In addition, it promoted a reduction in systolic blood pressure (MetS 149.0 ± 9.3 mmHg vs. MetS+O 132.0 ± 11.4 mmHg, p ≤ 0.05, d = 1.63, CI = 120-140), prevented an increase in cardiac collagen (MetS 12.60 ± 2.08% vs. MetS+O 7.52 ± 0.77%, p ≤ 0.05, d = 3.24, CI = 6.56-8.49). When associated with ET, the results were similar. Thus, we conclude that O consumption combined or not with aerobic ET can have a protective effect on the cardiac tissue of rats with MetS.

Integrative perspective of the healthy aging process considering the metabolome, cardiac autonomic modulation and cardiorespiratory fitness evaluated in age groups

The aging process causes changes at all organic levels. Although metabolism, cardiac autonomic modulation (CAM), and cardiorespiratory fitness (CRF) are widely studied as a function of age, they are mainly studied in isolation, thus making it difficult to perceive their concomitant variations. This study aimed to investigate the integrated changes that occur in the metabolome, CAM, and CRF throughout aging in apparently healthy individuals. The subjects (n = 118) were divided into five groups according to age (20-29, 30-39, 40-49, 50-59, and 60-70 years old) and underwent blood collection, autonomic assessment, and a cardiopulmonary exercise test for metabolomics analysis using mass spectrometry and nuclear magnetic resonance, cardiac autonomic modulation analysis, and CRF by peak oxygen consumption analysis, respectively. The Tukey's post hoc and effect size with confidence interval were used for variables with a significant one-way ANOVA effect (P < 0.01). The main changes were in the oldest age group, where the CRF, valine, leucine, isoleucine, 3-hydroxyisobutyrate, and CAM reduced and hippuric acid increased. The results suggest significant changes in the metabolome, CAM, and CRF after the age of sixty as a consequence of aging impairments, but with some changes in the metabolic profile that may be favorable to mitigate the aging deleterious effects.

Remote Heart Rate Prediction in Virtual Reality Head-Mounted Displays Using Machine Learning Techniques

Head-mounted displays are virtual reality devices that may be equipped with sensors and cameras to measure a patient's heart rate through facial regions. Heart rate is an essential body signal that can be used to remotely monitor users in a variety of situations. There is currently no study that predicts heart rate using only highlighted facial regions; thus, an adaptation is required for beats per minute predictions. Likewise, there are no datasets containing only the eye and lower face regions, necessitating the development of a simulation mechanism. This work aims to remotely estimate heart rate from facial regions that can be captured by the cameras of a head-mounted display using state-of-the-art EVM-CNN and Meta-rPPG techniques. We developed a region of interest extractor to simulate a dataset from a head-mounted display device using stabilizer and video magnification techniques. Then, we combined support vector machine and FaceMash to determine the regions of interest and adapted photoplethysmography and beats per minute signal predictions to work with the other techniques. We observed an improvement of 188.88% for the EVM and 55.93% for the Meta-rPPG. In addition, both models were able to predict heart rate using only facial regions as input. Moreover, the adapted technique Meta-rPPG outperformed the original work, whereas the EVM adaptation produced comparable results for the photoplethysmography signal.

A comparison of fine particulate matter (PM2.5) in vivo exposure studies incorporating chemical analysis

The complex, variable mixtures present in fine particulate matter (PM_2.5) have been well established, and associations between chemical constituents and human health are expanding. In the past decade, there has been an increase in PM_2.5 toxicology studies that include chemical analysis of samples. This investigation is a crucial component for identifying the causal constituents for observed adverse health effects following exposure to PM_2.5. In this review, investigations of PM_2.5 that used both in vivo models were explored and chemical analysis with a focus on respiratory, cardiovascular, central nervous system, reproductive, and developmental toxicity was examined to determine if chemical constituents were considered in the interpretation of the toxicity findings. Comparisons between model systems, PM_2.5 characteristics, endpoints, and results were made. A vast majority of studies observed adverse effects in vivo following exposure to PM_2.5. While limited, investigations that explored connections between chemical components and measured endpoints noted significant associations between biological measurements and a variety of PM_2.5 constituents including elements, ions, and organic/elemental carbon, indicating the need for such analysis. Current limitations in available data, including relatively scarce statistical comparisons between collected toxicity and chemical datasets, are provided. Future progress in this field in combination with epidemiologic research examining chemical composition may support regulatory standards of PM_2.5 to protect human health.

The susceptibility of cardiac arrhythmias after spinal cord crush injury in rats

High-level spinal cord injury (SCI) often interrupts supraspinal regulation of sympathetic input to the heart. Although it is known that dysregulated autonomic control increases the risk for cardiac disorders, the mechanisms mediating SCI-induced arrhythmias are poorly understood. Here, we employed a rat model of complete spinal cord crush injury at the 2nd/3rd thoracic (T2/3) level to investigate cardiac rhythm disorders resulting from SCI. Rats with T9 injury and naïve animals served as two controls. Four weeks after SCI, rats were implanted with a radio-telemetric device for electrocardiogram and blood pressure monitoring. During 24-h recordings, heart rate variability in rats with T2/3 but not T9 injury exhibited a significant reduction in the time domain, and a decrease in power at low frequency but increased power at high frequency in the frequency domain which indicates reduced sympathetic and increased parasympathetic outflow to the heart. Pharmacological blockade of the sympathetic or parasympathetic branches confirmed the imbalance of cardiac autonomic control. Activation of sympatho-vagal input during the induction of autonomic dysreflexia by colorectal distention triggered various severe arrhythmic events in T2/3 injured rats. Meanwhile, intravenous infusion of the β1-adrenergic receptor agonist, dobutamine, caused greater incidence of arrhythmias in rats with T2/3 injury than naïve and T9 injured controls. Together, the results indicate that high-level SCI increases the susceptibility to developing cardiac arrhythmias likely owing to compromised autonomic homeostasis. The T2/3 crush model is appropriate for studying abnormal cardiac electrophysiology resulting from SCI.

Sleep medicine: Practice, challenges and new frontiers

Sleep medicine is an ambitious cross-disciplinary challenge, requiring the mutual integration between complementary specialists in order to build a solid framework. Although knowledge in the sleep field is growing impressively thanks to technical and brain imaging support and through detailed clinic-epidemiologic observations, several topics are still dominated by outdated paradigms. In this review we explore the main novelties and gaps in the field of sleep medicine, assess the commonest sleep disturbances, provide advices for routine clinical practice and offer alternative insights and perspectives on the future of sleep research.

Effect of occupational exposure to welding fumes and noise on heart rate variability: An exposed-unexposed study on welders and airport workers' population

Introduction

Welding fumes (WF) are a complex mixture of gas and particles. Action of occupational exposure to WF on cardiovascular system has been recently studied as for noise.

Research question

The main objectives of our study are therefore to evaluate the impact of exposure to WF, noise, and combined WF and noise on autonomic nervous system as assessed by heart rate variability (HRV).

Methods

The study groups were 16 welders and eight airport workers (as a control group). All the participants underwent ambulatory electrocardiogram, personal WF, and noise exposure monitoring, respectively, with dust track and calibrated noise dosimeter during workday. Atmospheric environmental assessments at workplaces have been also performed. HRV parameters were summarized for all the workday and hourly. Correlation tests were used to examine relation between HRV parameters and levels of noise exposure in the two population. Analysis of covariance (ANCOVA) was used for mean of each HRV parameters.

Results

For HRV parameters, we found significant higher levels for mean range of high frequency (HF), standard deviation of normal-to-normal R-R interval (SDNN), and root mean square of successive heartbeat interval difference (RMSSD) in welders which suggested an imbalance between sympathetic and parasympathetic nervous system in this population. For relation between noise and HRV parameters, we noted that levels of low frequency (LF), HF, and SDNN were significantly correlated with mean noise levels for welders (respectively, r = 0.62, r = 0.357, r = 0.48), not in control group. Using ANCOVA, we found that working as a welder significantly increases mean of HF (p = 0.01) and RMSSD (p = 0.02) and decreases in LF/HF (p = 0.008). Indeed, the interaction between exposure to WF and mean noise levels for HF (p = 0.005), LF/HF (p = 0.01), and RMSSD (p = 0.007) was significant.

Conclusion

This study shows an impact of WF and noise on ANS balance. One hypothesis is WF exposure could increase sensibility to noise exposure on autonomic nervous system or there is a synergic effect.

Mediterranean Diet, Interoception and Mental Health: Is it time to look beyond the 'Gut-Brain Axis'?

OBJECTIVE

A Mediterranean style diet (i.e., high in fruit, vegetables, fish, pulses, and wholegrains) is said to benefit psychological health. Many low-level interoceptive processes, such as those involved in the 'gut-brain' axis, are suggested to play a mechanistic role in in this relationship. However, interoceptive sensations in other domains, and at higher hierarchical levels of abstraction, have hitherto been overlooked. One domain often studied in relation to psychological health is cardioception. Therefore, we examined whether the Mediterranean diet was associated with first-order perceptual and second-order metacognitive cardioception.

METHODS

Participants completed the Heartbeat Detection Task, the Heartbeat Counting Task, and the EPIC-Norfolk Food Frequency Questionnaire from which diet was quantified.

RESULTS

Adherence to a Mediterranean style diet was associated with higher cardioceptive accuracy (i.e., perceptual performance) across both tasks. In addition, those consuming a Mediterranean diet had a better ability to detect errors in first order perceptual performance, and a lower prediction error (the magnitude of the difference between accuracy and confidence).

DISCUSSION

These findings indicated that deepening our understanding of how interoceptive processes beyond the 'gut-brain' axis are shaped by diet could deepen our understanding of the link between diet and mental health and wellbeing.

Meta-Analysis and Systematic Review of Resting-State High-Frequency Heart Rate Variability in Binge-Eating Disorder

Abstract. Binge-eating disorder (BED) is associated with a greater risk for cardiac problems and co-occurring health conditions. Resting-state measures of high-frequency heart rate variability (HF-HRV), which is a physiological proxy of self-regulatory neural functioning, may aid understanding of health risks. We systematically reviewed and meta-analyzed the literature on HF-HRV in individuals with BED and without BED. Six studies were reviewed in the qualitative synthesis, and five studies assessing HRV in individuals with BED ( n = 153) and without BED ( n = 124) were included in the meta-analysis. A non-significant effect size (Hedges’ g = .08, SE = 0.36, 95% CI [−0.62, 0.78]; z = 0.23, p = .82) was found, suggesting no difference in HF-HRV between groups. Age, BMI, and BMI-matched control status were not significant covariates. Synthesizing the five studies with available data, we found no difference in resting-state HF-HRV between individuals with and without BED. There was high heterogeneity in the sample, suggesting potential moderators. We discuss potential mechanisms, methodological and demographic confounds, and future directions for study.

Heart rate variability predicts outcome of short-term psychotherapy at the workplace

The bio-psycho-social model highlights intra-individual and inter-individual interactions, including psychotherapy. The processing of these interactions within a person takes place, among others, in the central autonomic network (CAN). The CAN's autonomic output to the periphery can be indexed by heart rate variability (HRV), representing individual adaptive capacity. Further, the CAN influences the hypothalamus-pituitary-adrenal axis with its product cortisol. The aim consisted in investigating HRV and cortisol as well as their relation to symptom course in response to short-term psychotherapy. A single-arm, uncontrolled, explorative study was conducted at an outpatient psychotherapeutic consultation in the workplace offered to employees with mental or psychosomatic complaints. Questionnaires included symptoms of depression, irritation and functional impairment. Circadian profile of HRV and salivary cortisol concentrations collected pre and post short-term psychotherapeutic intervention (4-12 sessions) were assessed. Multilevel-linear mixed regressions were calculated. Out of 29 participants (mean age 42; 72% female), 24% were on sick leave from work. Cortisol concentrations were neither affected by intervention nor by symptom course. The proportion of individuals showing a vagally mediated HRV in the range of the lowest quartile assessed for age- and sex-matched healthy controls was reduced at follow-up (pre 34%, post 22%; p = .017). Higher vagally mediated HRV at baseline predicted lower symptom burden at follow-up. Thus, the results support the assumption that HRV reflects the capability of an organism to adapt and recover. Patients with reduced HRV might need additional psychotherapeutic sessions to achieve the same symptom improvements than patients with retained HRV.

Effect of Transcranial Pulsed Current Stimulation on Fatigue Delay after Medium-Intensity Training

The purpose of this study was to investigate the effect of transcranial pulsed current stimulation (tPCS) on fatigue delay after medium-intensity training. Materials and Methods: Ninety healthy college athletes were randomly divided into an experimental group (n = 45) and control group (n = 45). The experimental group received medium-intensity training for a week. After each training, the experimental group received true stimulation of tPCS (continuous 15 min 1.5 mA current intensity stimulation). The control group received sham stimulation. The physiological and biochemical indicators of participants were tested before and after the experiment, and finally 30 participants in each group were included for data analysis. Results: In the experimental group, creatine kinase (CK), cortisol (C), time-domain heart rate variability indices root mean square of the successive differences (RMSSD), standard deviation of normal R-R intervals (SDNN), and frequency domain indicator low frequency (LF) all increased slowly after the intervention. Among these, CK, C, and SDNN values were significantly lower than those in the control group (p < 0.05). Testosterone (T), T/C, and heart rate variability frequency domain indicator high frequency (HF) in the experimental group decreased slowly after the intervention, and the HF value was significantly lower than that in the control group (p < 0.05). The changes in all of the indicators in the experimental group were smaller than those in the control group. Conclusion: The application of tPCS after medium-intensity training enhanced the adaptability to training and had a significant effect on the maintenance of physiological state. The application of tPCS can significantly promote the recovery of autonomic nervous system function, enhance the regulation of parasympathetic nerves, and delay the occurrence of fatigue.

Higher Resting Cardiovagal Activity Predicts Larger Decrease of Depressive Symptoms in Inpatients Treated for Stress-Related Depression

Abstract. Depression is one of the most prevalent mental disorders, with treatment outcomes generally being unsatisfactory. The identification of outcome predictors could contribute to improving diagnosis, treatment, and outcome. Heart rate variability (HRV), an index of cardiovagal activity, has been proposed as a potential correlate of depression as well as a predictor of treatment effectiveness. The aim of the present study was to examine if HRV at baseline could predict the outcome of inpatient treatment for stress-related depressive disorder (SRDD). Depressive symptoms of n = 57 inpatients with an SRDD, who were treated in a specialized burnout ward, were assessed using the Beck Depression Inventory (BDI) at the beginning, the end of treatment, and at 3-month follow-up. HRV (i.e., RMSSD, the root mean square of successive RR interval differences) was determined from a five-minute measurement in the supine position. RMSSD was not significantly associated with the BDI score at the beginning, end, and follow-up. Higher RMSSD was revealed to be a significant predictor of a stronger decrease in depressive severity from the beginning to the end of the treatment. Thereby, the regression model explained 7.6% of the total variance in the BDI decrease. The results revealed initial HRV to predict a larger decrease in depressive severity. Therefore, resting HRV represents a physiological resource and index of successful neurovisceral interaction, which supports inpatients in benefitting from specialized treatment.

Machine Learning Models and Videos of Facial Regions for Estimating Heart Rate: A Review on Patents, Datasets, and Literature

Estimating heart rate is important for monitoring users in various situations. Estimates based on facial videos are increasingly being researched because they allow the monitoring of cardiac information in a non-invasive way and because the devices are simpler, as they require only cameras that capture the user’s face. From these videos of the user’s face, machine learning can estimate heart rate. This study investigates the benefits and challenges of using machine learning models to estimate heart rate from facial videos through patents, datasets, and article review. We have searched the Derwent Innovation, IEEE Xplore, Scopus, and Web of Science knowledge bases and identified seven patent filings, eleven datasets, and twenty articles on heart rate, photoplethysmography, or electrocardiogram data. In terms of patents, we note the advantages of inventions related to heart rate estimation, as described by the authors. In terms of datasets, we have discovered that most of them are for academic purposes and with different signs and annotations that allow coverage for subjects other than heartbeat estimation. In terms of articles, we have discovered techniques, such as extracting regions of interest for heart rate reading and using video magnification for small motion extraction, and models, such as EVM-CNN and VGG-16, that extract the observed individual’s heart rate, the best regions of interest for signal extraction, and ways to process them.

Exercise dose-response relationship with heart rate variability in individuals with overweight and obesity: protocol for a systematic review and meta-analysis of randomised controlled trials

INTRODUCTION

Obesity is a chronic relapsing disease process and serious public health concern that can lead to chronic diseases, medical complications and a higher risk of disability. Another significant feature of obesity is dysfunction in cardiac autonomic function, which leads to changes in parasympathetic and sympathetic regulation, which can be measured using heart rate variability (HRV). The objective of this review is to estimate the extent to which exercise doses impacts on HRV among individuals living with overweight and obesity class I and II.

METHODS AND ANALYSIS

A systematic literature search will be performed using PubMed/Medline, Scopus, EMBASE, ProQuest, CINAHL, Web of Science and the Cochrane Library for articles dating from 1965 to December 2021. Inclusion criteria include studies designed as parallel-arm randomised trials, enrolling adolescent and adult individuals with overweight (body mass index, BMI≥25 to ≤29.9) and obesity (class I BMI: 30-34.9 and class II BMI: 35-39.9) undergoing aerobic or resistance training or concurrent exercise training. For data synthesis, sensitivity analysis, subgroup analysis and risk of bias assessment, Stata V.13.0 software will be used.

ETHICS AND DISSEMINATION

Formal ethical approval is not required. This systematic review will be submitted to a peer-reviewed journal.

PROSPERO REGISTRATION NUMBER

CRD42019104154.

Stress Management Intervention for Leaders Increases Nighttime SDANN: Results from a Randomized Controlled Trial

Stress management interventions aim to reduce the disease risk that is heightened by work stress. Possible pathways of risk reduction include improvements in the autonomous nervous system, which is indexed by the measurement of heart rate variability (HRV). A randomized controlled trial on improving stress management skills at work was conducted to investigate the effects of intervention on HRV. A total of 174 lower management employees were randomized into either the waiting list control group (CG) or the intervention group (IG) receiving a 2-day stress management training program and another half-day booster after four and six months. In the trial, 24 h HRV was measured at baseline and after 12 months. Heart rate (HR), root mean square of successive differences (RMSSD), standard deviation of normal-to-normal intervals (SDNN), and standard deviation of the average of normal-to-normal intervals (SDANN) were calculated for 24 h and nighttime periods. Age-adjusted multilevel mixed effects linear regressions with unstructured covariance, time as a random coefficient, and time × group interaction with the according likelihood-ratio tests were calculated. The linear mixed-effect regression models showed neither group effects between IG and CG at baseline nor time effects between baseline and follow-up for SDANN (24 h), SDNN (24 h and nighttime), RMSSD (24 h and nighttime), and HR (24 h and nighttime). Nighttime SDANN significantly improved in the intervention group (z = 2.04, p = 0.041) compared to the control group. The objective stress axis measures (SDANN) showed successful stress reduction due to the training. Nighttime SDANN was strongly associated with minimum HR. Though the effects were small and only visible at night, it is highly remarkable that 3 days of intervention achieved a measurable effect considering that stress is only one of many factors that can influence HR and HRV.

The Evaluation of Biomarkers of Physical Activity on Stress Resistance and Wellness

Physical activity can improve health as well as reduce stress and the risk of developing several widespread diseases. However, there exists no accepted standard biomedical examination-method for stress evaluation. The purpose of this study was to investigate the effect of regular physical activity on stress and wellness as well as the evaluation of potential biomarkers in this field. This study included 105 people (mean age = 36.57 ± 1.4 years) who were randomly assigned into the exercise group 1 (EG-1) (n = 41), the exercise group 2 (EG-2) (n = 30), and the control group (CG) (n = 34). Measurements of stress and wellness were obtained by Multiscan BC-OXI before and after experimental period. This device presents a multifrequency segmental body composition 3D analyser with digital pulse oximeter. The key indicators of stress as well as for wellness were significantly improved in the EG-1. Parasympathetic activity showed significant changes as potential stress biomarker. Statistically significant gender differences were not observed in the comparable groups. The results suggest that the stress resistance and well-being significantly improved in the EG-1 due to regular physical activity. However, further research is necessary to determine effects of physical activity on integral health indicators.

The Consumption of a Synbiotic Does Not Affect the Immune, Inflammatory, and Sympathovagal Parameters in Athletes and Sedentary Individuals: A Triple-Blinded, Randomized, Place-bo-Controlled Pilot Study

This investigation aimed to identify the effect of a synbiotic in athletes and sedentary people, and their potential varying responses regarding the immune system, autonomic regulation and body composition. Twenty-seven participants were involved in the protocol: 14 sedentary and 13 semi-professional soccer players. Both groups were randomly divided into an experimental and control group. A synbiotic (Gasteel Plus^®, Heel España S.A.U.) comprising a blend of probiotic strains, including Bifidobacterium lactis CBP-001010, Lactobacillus rhamnosus CNCM I-4036, and Bifidobacterium longum ES1, was administered to the experimental group, and a placebo was given to the control group for 30 days. Heart rate variability, body composition, and immune/inflammatory cytokines were determined. Statistically significant differences were observed between sedentary individuals and athletes in heart rate variability but not between the experimental and control groups. A difference between the athletic and sedentary group is observed with the influence of training on the effects of the synbiotic on the levels of fat mass and body-fold sum. No significant differences were shown in cytokines after the protocol study. No changes occur with the synbiotic treatment between the athlete and sedentary groups, while no negative effect was produced. Further research will be necessary to see chronic effects in the analyzed biomarkers.