Short-term heart rate variability--influence of gender and age in healthy subjects

Heart rate variability is more sensitive to stress than heart rate in specialist police undergoing selection

Police tactical group (PTG) officers respond to the most demanding and high-risk police situations. As such, PTG personnel require exceptional physical fitness, and selection for employment often evaluates fitness both directly and indirectly. While heart rate (HR) is often used to measure physical effort, heart rate variability (HRV) may be a valuable tool for measuring stress holistically. The primary aim of this research was to investigate whether HRV was more sensitive than HR at monitoring workload during key PTG selection activities. As aerobic fitness is associated with workload during these tasks, a secondary aim was to investigate relationships between HRV, HR and aerobic fitness during the same tasks. The relationships between HRV (percentage of adjacent R-R intervals varying by 50% or more; pRR50%) and HR, as measured by ambulatory electrocardiograms obtained during a specialist police selection course, as well as aerobic fitness, as determined via total shuttles completed on the 20-meter multistage fitness test (MSFT; 'beep test'), were investigated. This study included a cohort of six male PTG candidates (n = 6) undergoing selection. As illustrated by a time-series plot, HR values were generally unremarkable, but HRV values were potentially depressed, and tentatively indicated overstress when count data from consecutive short-term analyses were derived. The MSFT was significantly, positively, correlated with pRR50% (ρ (6) = 0.812, p = 0.050, Fisher's z = 1.132). The MSFT and nonlinear HRV, frequency domain HRV, and HR were not significantly correlated. When assessed by linear regression, neither HRV nor HR were predicted by MSFT score. These findings indicate that HR alone is likely not sufficiently sensitive to provide detail on the stress response of candidates undertaking essential tactical tasks that combine physical stressors with cognitive load in adverse conditions. HRV analysis may provide additional insights regarding candidate suitability, particularly during dynamic and multifaceted assessments, though the causal direction of the relationship between HRV and aerobic fitness remains unclear.

Post-traumatic stress disorder (PTSD) symptom clusters associated with an indicator of heart rate variability: The ADVANCE cohort study

BACKGROUND

Heart rate variability (HRV) is governed by sympathetic and parasympathetic regulatory systems. Post-Traumatic Stress Disorder (PTSD) may influence these systems and consequently affect cardiovascular functioning.

METHODS

The sample consisted of 860 UK male military personnel approximately half of whom had sustained physical combat injuries in Afghanistan. HRV was measured via Root-Mean Square of Successive Differences (RMSSD) in normal heart beats and PTSD using a self-report questionnaire (Posttraumatic Checklist-Civilian version (PCL)). Associations between probable PTSD status (PCL score ≥ 50) and symptom clusters (avoidance behaviours, emotional numbing, hyperarousal and intrusive thoughts) with HRV were examined. Bootstrap inclusion frequencies and model averaging were employed prior to regression modelling to identify the most important symptom clusters associated with RMSSD.

RESULTS

Probable PTSD status was not associated with log RMSSD [-11.6 % (95 % Confidence Interval (CI) -22.2 %, 4.1 %). Increases in severity of emotional numbing were associated with reductions in RMSSD, with a - 1.1 % (95%CI -2.1 %, -0.2 %) decrease in the geometric mean of RMSSD per point increase on the emotional numbing subscale.

LIMITATIONS

High levels of comorbidity with depression/anxiety; possible endogeneity/bidirectionality due to PCL including both psychological and physiological symptoms.

CONCLUSIONS

Emotional numbing, the symptom cluster including symptoms such as anhedonia, cognitive dysregulation and feeling distant from other people, was associated with lower HRV whilst overall PTSD status was not. These results lend support to the hypothesis that different PTSD symptom clusters may have unique effects on the cardiovascular system, and that particular symptom clusters of PTSD or combinations thereof may be associated with distinctive cardiovascular profiles.

Depressive symptoms and heart rate variability in perinatal women: A narrative review

AIM

This study aims to review research on heart rate variability and psychiatric symptoms in perinatal women and explains how heart rate variability can be useful in preventing depressive symptoms in perinatal women.

METHODS

Data were collected from PubMed, CINAHL, PsycINFO, and Google Scholar. The literature search encompassed articles published until July 2024, with the inclusion criteria targeting studies on women within 1 year postpartum, starting from the gestation period. Further, articles exploring this population that discussed the relationship between anxiety, depression, stress, and heart rate variability were selected. The exclusion criterion was studies that confirmed a correlation between stressors and heart rate variability.

RESULTS

We identified 36 relevant articles. The results demonstrated that, since 2022, research has been conducted using smartwatches, smartphones, and so on. The effectiveness of using heart rate variability has been confirmed, particularly in studies linking it to depression. However, some studies lacked controls during measurements. Intervention studies demonstrated the effectiveness of heart rate variability biofeedback.

CONCLUSIONS

This is the first review to investigate the relationship between psychiatric symptoms and heart rate variability in perinatal women. Understanding and using the characteristics of heart rate variability may lead to the detection of psychiatric symptoms in perinatal women and to self-care among women.

Unraveling the discrepancies between REDUCE-IT and STRENGTH trials with omega-3 fatty acids: new analytical approaches

Two large-scale, randomized, double-blind, placebo-controlled trials-REDUCE-IT and STRENGTH-have garnered significant attention in cardiovascular medicine. Both trials aimed to evaluate the effects of prolonged administration of nutritional lipids, specifically omega-3 fatty acids, on major adverse cardiovascular events (MACEs) in high-risk patients undergoing statin therapy. REDUCE-IT used eicosapentaenoic acid (EPA) ethyl ester with mineral oil as a control, while STRENGTH utilized a carboxylic acid formulation of both EPA and docosahexaenoic acid (DHA) with corn oil as a control. Notably, REDUCE-IT demonstrated a reduction in MACE risk with EPA, whereas STRENGTH showed no such benefit with the combination of EPA and DHA. Despite extensive and insightful discussions following the publication of these trials, the underlying reasons for this discrepancy remain elusive. We posit that further investigation into resting heart rate (RHR), heart rate variability (HRV), and ethnic subgroup data-collected but not fully explored-is critical to unraveling the divergent outcomes of the REDUCE-IT and STRENGTH trials. These additional analyses could provide pivotal insights into the mechanisms driving the differential effects of omega-3 fatty acids in high-risk cardiovascular patients. Given that previous discussions have not fully addressed these potential variables, exploring them may illuminate unexplored pathways and offer a deeper understanding of the mechanistic and clinical roles of omega-3 s in cardiovascular health. We hypothesize that by delving into these under-analyzed factors, we can not only clarify the discrepancies between the trials but also advance our broader understanding of cardiovascular nutrition and medicine.

Effects of individualized resistance training prescription with heart rate variability on muscle strength, muscle size and functional performance in older women

Introduction

This study aimed to investigate whether individualizing autonomic recovery periods between resistance training (RT) sessions (IND) using heart rate variability (HRV), measured by the root mean square of successive R-R interval differences (RMSSD), would lead to greater and more consistent improvements in muscle strength, muscle mass, and functional performance in older women compared to a fixed recovery protocol (FIX).

Methods

Twenty-one older women (age 66.0 ± 5.0 years old) were randomized into two different protocols (IND: n = 11; FIX: n = 10) and completed 7 weeks of RT. Measurements of RMSSD were performed within a five-day period to establish baseline values. The RMSSD values determined whether participants were recovered from the previous session. The assessments included muscle cross-sectional area (CSA), one-repetition maximum (1RM), peak torque (PT), rate of force development (RFD), chair stand (CS), timed up and go (TUG), 6-minutes walking (6MW), and maximum gait speed (MGS).

Results

There were no significant (P > 0.05) group vs. time interactions. There were significant main effects of time (P < 0.05) for CSA, 1RM, PT, TUG, CS, 6MW, and MGS, while no significant changes were observed for RFD (P > 0.05).

Conclusion

IND does not seem to enhance responses in muscle mass, strength, and functional performance compared FIX in healthy older women.

Diagnostic accuracy of heart rate variability as a screening tool for mild neurocognitive disorder

Background

Mild neurocognitive disorder (mNCD) is recognized as an early stage of dementia and is gaining attention as a significant healthcare problem due to current demographic changes and increasing numbers of patients. Timely detection of mNCD provides an opportunity for early interventions that can potentially slow down or prevent cognitive decline. Heart rate variability (HRV) may be a promising measure, as it has been shown to be sensitive to cognitive impairment. However, there is currently no evidence regarding the diagnostic accuracy of HRV measurements in the context of the mNCD population. This study aimed to evaluate the diagnostic accuracy of vagally-mediated HRV (vm-HRV) as a screening tool for mNCD and to investigate the relationship between vm-HRV with executive functioning and depression in older adults who have mNCD.

Methods

We retrospectively analyzed data from healthy older adults (HOA) and individuals with a clinical diagnosis of mNCD with a biomarker-supported characterization of the etiology of mNCD. Diagnostic accuracy was evaluated using receiver operating characteristic curve analysis based on the area under the curve. Sensitivity and specificity were calculated based on the optimal threshold provided by Youden's Index. Multiple linear regression analyses were conducted to investigate the relationship between vm-HRV and executive functioning and depression.

Results

This analysis included 42 HOA and 29 individuals with mNCD. The relative power of high frequency was found to be increased in individuals with mNCD. The greatest AUC calculated was 0.68 (with 95% CI: 0.56, 0.81) for the relative power of high frequency. AUCs for other vm-HRV parameters were between 0.53 and 0.61. No consistent correlations were found between vm-HRV and executive functioning or depression.

Conclusion

It appears that vm-HRV parameters alone are insufficient to reliably distinguish between HOA and older adults with mNCD. Additionally, the relationship between vm-HRV and executive functioning remains unclear and requires further investigation. Prospective studies that encompass a broad range of neurocognitive disorders, HRV measurements, neuroimaging, and multimodal approaches that consider a variety of functional domains affected in mNCD are warranted to further investigate the potential of vm-HRV as part of a multimodal screening tool for mNCD. These multimodal measures have the potential to improve the early detection of mNCD in the future.

The influence of virtual reality simulation on surgical residents' heart rate during an assessment of arthroscopic technical skills: A prospective, paired observational study

HYPOTHESIS

To demonstrate that a virtual reality (VR) simulation training program reduces heart rate variability during an assessment of surgical trainees' technical skills in arthroscopy.

STUDY DESIGN

Prospective observational matched study.

MATERIALS & METHODS

Thirty-six orthopaedic surgery residents, new to arthroscopy, received standard training in arthroscopic knee surgery, supplemented by additional monthly training for 6months on a VR simulator for 16 of them. At inclusion, the 2 groups (VR and NON-VR) answered a questionnaire and performed a meniscectomy on a VR simulator. After 6months of training, two independent trainers blinded to the inclusion arms evaluated the technical skills of the two groups during meniscectomies on a model and on an anatomical subject. Heart rate variability (HRV) was measured using a wireless heart rate monitor during baseline, VR training, and assessment.

RESULTS

After removing incomplete data, the analysis focused on 10 VR residents matched at inclusion with 10 NON-VR residents. The VR group had a significantly lower heart rate at the final assessment (p=0.02) and lower overall HRV (p=0.05). The low/high frequency ratio (LF/HF) was not significantly different between the groups (1.84 vs 2.05, p=0.66) but the before-after training comparison showed a greater decrease in this ratio in the VR group compared to the NON-VR group -0.76 (-41%) vs -0.08 (-4%).

CONCLUSION

This study demonstrates a significant difference in heart rate variability between trained residents versus untrained residents during the final assessment of their technical skills at 6months. It appears that improving stress management should be an integral part of training programs in arthroscopic surgery.

CLINICAL INTEREST

VR simulators in arthroscopy could improve non-technical skills such as heart rate variability, from the perspective of accountability.

LEVEL OF EVIDENCE

III.

The effect of heart rate variability on the choroidal vascularity of the optical coherence tomography and angiography in central serous chorioretinopathy

PURPOSE

To investigate the correlation between the autonomic nervous system and choroidal vascularity in patients with central serous chorioretinopathy (CSC), using heart rate variability (HRV) analysis, optical coherence tomography (OCT) and OCT angiography (OCTA).

METHODS

We retrospectively analyzed data of 25 patients with unilateral CSC (50 eyes, including the unaffected fellow eyes) and 25 healthy controls. The assessment involved a 5-minute HRV analysis encompassing both frequency and time domains, especially low frequency (LF), high frequency (HF), and LF/HF ratio. In OCT (12 × 9 mm) and en-face OCTA (3 × 3 mm) scans, we measured parameters including choroidal vascularity index (CVI), choroidal vessel density in the middle and deep layers, and choriocapillaris flow void. Regression analysis was conducted to elucidate the associations between HRV parameters and OCT/OCTA measurements.

RESULTS

Normalized LF(LFnorm) and LF/HF ratios were higher in patients with CSC than in healthy controls. LFnorm and the log-transformed ratio of LF to HF [log(LF/HF)] demonstrated a significant and borderline correlation with CVI in the linear regression analysis (P = 0.040, R2 = 0.171, and P = 0.059, R2 = 0.147, respectively). Both CVI and deep choroid vessel density showed a more significant association with LFnorm and log (LF/HF) in the non-linear quadratic regression analysis than in the linear analysis (all, P < 0.04, R2 > 0.25).

CONCLUSION

The frequency-domain parameters of HRV, including LFnorm and log (LF/HF), demonstrated a significant association with indicators reflective of large choroidal vessel luminal area on macular OCT/OCTA scans. This observation implies complicated modulation of choroidal blood flow by the autonomic nervous system in CSC.

Changes in Negative Emotions Across Five Weeks of HRV Biofeedback Intervention were Mediated by Changes in Resting Heart Rate Variability

Resting heart rate variability (HRV) is typically higher in those with better emotional well-being. In the current study, we examined whether changes in resting HRV mediated changes in negative emotions during a 7-week clinical trial of HRV biofeedback. Younger and older adults were randomly assigned to one of two daily biofeedback practices for 5 weeks: (1) engage in slow-paced breathing to increase the amplitude of oscillations in heart rate at their breathing frequency (Osc+); or (2) engage in self-selected strategies to decrease heart rate oscillations (Osc-). We assessed negative emotion using the State Anxiety Inventory (SAI) and Profile of Mood States (POMS). Resting HRV at pre-intervention was significantly higher among those with lower negative emotion scores. Those participants showing greater increases in resting HRV showed greater decreases in negative emotion. In a mediation model with all participants, resting HRV changes significantly mediated the relationship between training performance (i.e., heart rate oscillation during practice sessions) and changes in negative emotion. However, additional analyses revealed this mediation effect was significantly moderated by condition and was only significant in the Osc+ condition. Thus, resting HRV changes mediated how biofeedback to increase amplitude of heart rate oscillations reduced negative emotion.

Heart rate variability and autonomic nervous system imbalance: Potential biomarkers and detectable hallmarks of aging and inflammaging

The most cutting-edge issue in the research on aging is the quest for biomarkers that transcend molecular and cellular domains to encompass organismal-level implications. We recently hypothesized the role of Autonomic Nervous System (ANS) imbalance in this context. Studies on ANS functions during aging highlighted an imbalance towards heightened sympathetic nervous system (SNS) activity, instigating a proinflammatory milieu, and attenuated parasympathetic nervous system (PNS) function, which exerts anti-inflammatory effects via the cholinergic anti-inflammatory pathway (CAP) and suppression of the hypothalamic-pituitary-adrenal (HPA) axis. This scenario strongly suggests that ANS imbalance can fuel inflammaging, now recognized as one of the most relevant risk factors for age-related disease development. Recent recommendations have increasingly highlighted the need for actionable strategies to improve the quality of life for older adults by identifying biomarkers that can be easily measured, even in asymptomatic individuals. We advocate for considering ANS imbalance as a biomarker of aging and inflammaging. Measures of ANS imbalance, such as heart rate variability (HRV), are relatively affordable, non-invasive, and cost-effective, making this hallmark easily diagnosable. HRV gains renewed significance within the aging research landscape, offering a tangible link between pathophysiological perturbations and age-related health outcomes.

Gender differences in autonomic and psychological stress responses among educators: a heart rate variability and psychological assessment study

Introduction

This study explores the gender differences in psychological stress perception and autonomic modulation among teachers.

Methods

Utilizing heart rate variability (HRV) as a measure of autonomic function and a suite of validated psychological tests, the study examines the discrepancies in stress, anxiety, burnout, and personality traits between male and female educators.

Results

Results indicate that despite higher reported levels of stress and anxiety, women demonstrate a higher HRV, suggesting a stronger parasympathetic response.

Discussion

These findings highlight the complex interplay between psychological stressors and physiological responses, emphasizing the need for gender-specific interventions in stress management within the educational sector. Implications for enhancing educators' well-being and performance through tailored strategies are discussed.

Overnight Sleep Staging Using Chest-Worn Accelerometry

Overnight sleep staging is an important part of the diagnosis of various sleep disorders. Polysomnography is the gold standard for sleep staging, but less-obtrusive sensing modalities are of emerging interest. Here, we developed and validated an algorithm to perform "proxy" sleep staging using cardiac and respiratory signals derived from a chest-worn accelerometer. We collected data in two sleep centers, using a chest-worn accelerometer in combination with full PSG. A total of 323 participants were analyzed, aged 13-83 years, with BMI 18-47 kg/m2. We derived cardiac and respiratory features from the accelerometer and then applied a previously developed method for automatic cardio-respiratory sleep staging. We compared the estimated sleep stages against those derived from PSG and determined performance. Epoch-by-epoch agreement with four-class scoring (Wake, REM, N1+N2, N3) reached a Cohen's kappa coefficient of agreement of 0.68 and an accuracy of 80.8%. For Wake vs. Sleep classification, an accuracy of 93.3% was obtained, with a sensitivity of 78.7% and a specificity of 96.6%. We showed that cardiorespiratory signals obtained from a chest-worn accelerometer can be used to estimate sleep stages among a population that is diverse in age, BMI, and prevalence of sleep disorders. This opens up the path towards various clinical applications in sleep medicine.

Cardiac Autonomic Neuropathy in Graves' Disease: Smoking and Age as Predictive Factors

OBJECTIVES

Hypermetabolic state in Graves' disease (GD) has a great impact on heart homeostasis, acting directly on the heart muscle and modulating the autonomic nervous system. To characterize cardiac autonomic neuropathy (CAN) as a possible complication in patients with GD.

METHODS

We evaluated euthyroid GD patients and a control group of healthy euthyroid people. CAN was assessed using autonomic tests of cardiovascular reflex and heart rate variability: respiratory, Valsalva, orthostatic and orthostatic hypotension tests, high frequency, low frequency, and very low-frequency bands. Transthoracic echocardiography was performed in GD patients.

RESULTS

Sixty GD patients and 50 people in control group were assessed. CAN was diagnosed in 20% of GD and 14% in the control group. Among GD, 13.3% presented incipient, and 6.7% established CAN, while in the control group, it was verified incipient in 8% and established in 6% (P = .7479). All GD patients with CAN presented an alteration in the deep breathing test. Age and smoking were evidenced as factors associated with the presence of CAN, while higher TRAb values at diagnosis decreased the chance of CAN.

CONCLUSIONS

The prevalence of CAN in euthyroid GD patients was 20%. Changes in the cardiac autonomic nervous system were identified, pointing to the importance of evaluating this complication in these patients. Smoking was a predictive factor for CAN, increasing its relationship with conditions that aggravate GD.

Publication guidelines for human heart rate and heart rate variability studies in psychophysiology-Part 1: Physiological underpinnings and foundations of measurement

This Committee Report provides methodological, interpretive, and reporting guidance for researchers who use measures of heart rate (HR) and heart rate variability (HRV) in psychophysiological research. We provide brief summaries of best practices in measuring HR and HRV via electrocardiographic and photoplethysmographic signals in laboratory, field (ambulatory), and brain-imaging contexts to address research questions incorporating measures of HR and HRV. The Report emphasizes evidence for the strengths and weaknesses of different recording and derivation methods for measures of HR and HRV. Along with this guidance, the Report reviews what is known about the origin of the heartbeat and its neural control, including factors that produce and influence HRV metrics. The Report concludes with checklists to guide authors in study design and analysis considerations, as well as guidance on the reporting of key methodological details and characteristics of the samples under study. It is expected that rigorous and transparent recording and reporting of HR and HRV measures will strengthen inferences across the many applications of these metrics in psychophysiology. The prior Committee Reports on HR and HRV are several decades old. Since their appearance, technologies for human cardiac and vascular monitoring in laboratory and daily life (i.e., ambulatory) contexts have greatly expanded. This Committee Report was prepared for the Society for Psychophysiological Research to provide updated methodological and interpretive guidance, as well as to summarize best practices for reporting HR and HRV studies in humans.

Blunted cardiac autonomic dynamics to active standing test in postmenopausal women

Introduction

Although both aging and menopause influence cardiovascular autonomic control, the effect of menopause per se remains unclear. The current study was undertaken to test the hypothesis that post-menopausal women (PMW) have a blunted cardiovascular autonomic adjustment to active standing compared to pre-menopausal women. Thus, we compared the heart rate variability (HRV) indexes from supine (SUP) to orthostatic (ORT) positions among young women (YW), young men (YM), older men (OM), and PMW.

Methods

The participants rested for 10 min in SUP and then stood up and remained for 5 min in ORT. ECG was continuously recorded, and R-R time series of about 300 beats were analyzed using linear (spectral analysis) and non-linear (symbolic analysis) methods. The variation from SUP to ORT was calculated (Δ = ORT-SUP) for each HRV index.

Results

In SUP, no difference was found for any HRV index among groups. However, Δ0V% and ΔLFn (cardiac sympathetic modulation) were reduced in PWM compared to all groups (OM, YW, and YM), while Δ2UV% and ΔHFn (cardiac vagal modulation) were reduced in PMW than the younger group (YW and YM). No differences were found among the male groups (OM and YM).

Discussion

In light of our results, the cardiac autonomic dynamic response to orthostatic stress is blunted in post-menopausal women compared to younger women and older men, a finding that might be influenced not only by aging.

Toward stressor-free stress estimation: The integrated information theory explains the information dynamics of stress

Recent neurological studies have revealed several detailed stress mechanisms. However, the latent variables behind stress study still interpret stress responses as difficult. Therefore, we propose a stressor-free method of stress evaluation using Integrated Information Theory (IIT) to address these issues. We conducted experiments inducing acute stress responses against tasks with three levels of difficulty, easy, moderate, and difficult, to verify the IIT in stress study. The moderate condition was related to active coping with stress. By contrast, the easy and difficult conditions are related to passive stress coping. Especially, the easy condition seemed to cause boredom. Our results revealed that the degree of entangled system fluctuation was associated with the subjective ratings for the tasks. Interestingly, our method could also evaluate stress as a state of boredom that had not received much research attention. Our method can be an alternative stress estimation method to overcome the latent variable problem.

Multi-ethnic variation in the ties that bind rumination and heart rate variability: Implications for health disparities

Higher self-reported rumination, a common form of trait perseverative cognition, is linked with lower resting heart rate variability (HRV), which indicates poorer cardiac function and greater disease risk. A meta-analysis and systematic review indicated that in samples with fewer European Americans, the association of rumination with both heart rate and blood pressure was stronger. Thus, trait rumination may be more strongly associated with resting HRV among ethnically minoritized populations. The current study investigated whether differences in the association of self-reported rumination with resting HRV varied by ethnicity in a sample (N = 513; Mage = 19.41; 226 Women) of self-identified African Americans (n = 110), Asian Americans (n = 84), and European Americans (n = 319). Participants completed a five-minute baseline period to assess resting HRV, followed by the Ruminative Responses Scale, which contains three facets of rumination including brooding, depressive, and reflective rumination. On average, Asian Americans reported higher levels of rumination relative to European Americans. African Americans had higher resting HRV than Asian Americans. Adjusting for covariates, higher self-reported rumination was significantly associated with lower resting HRV in both African and Asian Americans, but not significantly so in European Americans. This finding was consistent for brooding and reflective, but not depressive rumination. Overall, this study lends insight into a psychological mechanism-rumination-that may impact health disparities among ethnically minoritized individuals, contributing to an understanding of how stress gets under the skin among such minoritized populations.

Heartbeat-evoked potentials following voluntary hyperventilation in epilepsy patients: respiratory influences on cardiac interoception

Introduction

Current evidence indicates a modulating role of respiratory processes in cardiac interoception, yet whether altered breathing patterns influence heartbeat-evoked potentials (HEP) remains inconclusive.

Methods

Here, we examined the effects of voluntary hyperventilation (VH) as part of a clinical routine examination on scalp-recorded HEPs in epilepsy patients (N = 80).

Results

Using cluster-based permutation analyses, HEP amplitudes were compared across pre-VH and post-VH conditions within young and elderly subgroups, as well as for the total sample. No differences in the HEP were detected for younger participants or across the full sample, while an increased late HEP during pre-VH compared to post-VH was fond in the senior group, denoting decreased cardiac interoceptive processing after hyperventilation.

Discussion

The present study, thus, provides initial evidence of breathing-related HEP modulations in elderly epilepsy patients, emphasizing the potential of HEP as an interoceptive neural marker that could partially extend to the representation of pulmonary signaling. We speculate that aberrant CO2-chemosensing, coupled with disturbances in autonomic regulation, might constitute the underlying pathophysiological mechanism behind the obtained effect. Available databases involving patient records of routine VH assessment may constitute a valuable asset in disentangling the interplay of cardiac and ventilatory interoceptive information in various patient groups, providing thorough clinical data to parse, as well as increased statistical power and estimates of effects with higher precision through large-scale studies.

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).

Using Heart Rate Variability to Assess Nurses' Stress During the COVID-19 Pandemic

OBJECTIVE

This study aimed to assess subjective and objective parameters of stress among nurses during the COVID-19 pandemic and to examine the recovery effect of a day off.

METHODS

In this prospective observational trial, we measured heart rate variability (using a wearable device) and perceived stress levels on 3 working days and 1 day off. We obtained the following data using an online questionnaire: working conditions, COVID-19-related problems, depression (Patient Health Questionnaire-9), anxiety (Generalized Anxiety Disorder-7), effort-reward imbalance, and work-family conflict in a sample of German nurses (N = 41).

RESULTS

When comparing working days with a day off, we observed a significant difference for physical load (Cohen's d = 0.798, P < .001), mental load (Cohen's d = 0.660, P = .001), emotional exhaustion (Cohen's d = 0.945, P < .001), and overburdening (Cohen's d = 0.585, P = .002) with higher scores on working days. Regarding heart rate variability, we did not find a difference. Correlational analyses revealed a significant association between being afraid to get infected with COVID-19 and lower heart rate variability (r = -0.336, P = .045) and between being afraid to infect relatives and lower heart rate variability (r = -0.442, P = .007). Furthermore, a higher total sum score of work-family conflict was significantly associated with lower heart rate variability (r = -0.424, P = .01).

CONCLUSION

As heart rate variability observations were different from those regarding subjectively perceived stress, further studies are needed to evaluate and differentiate the influence of work stress and other types of stress on heart rate variability.

Heart rate vARiability and physical activity in inpatient treatMent of burnOut and DepressIon (HARMODI): protocol of a cross-sectional study with up to 8-week follow up

INTRODUCTION

Chronic stress can cause an imbalance within the autonomic nervous system, thereby affecting cardiovascular and mental health. Physical activity (PA) may have a positive effect on the autonomic nervous system and stress-related disorders, such as depression and burnout. Heart rate variability (HRV) is a non-invasive marker of the autonomic nervous system. However, limited and inconsistent data exist on the exact relationship between HRV, PA and depression and burnout symptoms. The HARMODI study aims to explore whether HRV is a feasible marker of depression and burnout symptoms and aims to evaluate the role of PA in the treatment of stress-related disorders.

METHODS AND ANALYSES

This is an observational study with a cross-sectional up to 8 week follow-up study design. A total of 153 patients, undergoing psychiatric inpatient treatment with burnout syndrome (Z73) and depressive episode (F32 or F33) or adjustment disorder (F43.2), will be recruited. Data on depression and burnout symptoms, HRV recordings (24-hour, supine, standing and exercise stress test), cognitive function, cardiorespiratory fitness, cardiovascular health, balance and strength will be collected at baseline (T1) and after up to 8 weeks (T2). Continuous data on PA and Ecological Momentary Assessments of exhaustion, mood and tension will be monitored daily throughout inpatient treatment. Multiple regression models, adjusted for potential confounders, will assess the association between HRV as the primary outcome, PA and depression and burnout severity score.

ETHICS AND DISSEMINATION

The protocol has been approved by Swiss Ethics Committee, Cantonal Ethics Committee Zürich. Results of HARMODI will be disseminated through peer-reviewed journals and conference presentations.

TRIAL REGISTRATION NUMBER

NCT05874856.

Sex differences of signal complexity at resting-state functional magnetic resonance imaging and their associations with the estrogen-signaling pathway in the brain

Sex differences in the brain have been widely reported and may hold the key to elucidating sex differences in many medical conditions and drug response. However, the molecular correlates of these sex differences in structural and functional brain measures in the human brain remain unclear. Herein, we used sample entropy (SampEn) to quantify the signal complexity of resting-state functional magnetic resonance imaging (rsfMRI) in a large neuroimaging cohort (N = 1,642). The frontoparietal control network and the cingulo-opercular network had high signal complexity while the cerebellar and sensory motor networks had low signal complexity in both men and women. Compared with those in male brains, we found greater signal complexity in all functional brain networks in female brains with the default mode network exhibiting the largest sex difference. Using the gene expression data in brain tissues, we identified genes that were significantly associated with sex differences in brain signal complexity. The significant genes were enriched in the gene sets that were differentially expressed between the brain cortex and other tissues, the estrogen-signaling pathway, and the biological function of neural plasticity. In particular, the G-protein-coupled estrogen receptor 1 gene in the estrogen-signaling pathway was expressed more in brain regions with greater sex differences in SampEn. In conclusion, greater complexity in female brains may reflect the interactions between sex hormone fluctuations and neuromodulation of estrogen in women.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-023-09954-y.

Effects of Exercise Training on Heart Rate Variability in Healthy Adults: A Systematic Review and Meta-analysis of Randomized Controlled Trials

This meta-analysis was conducted to investigate the effects of exercise training on heart rate variability (HRV) parameters associated with the autonomic nervous system (ANS) activity. Randomized controlled trials (RCTs) involving healthy adults (aged ≥ 18 years) were included. We searched PubMed, Scopus, Web of Science, and EBSCO databases to identify relevant studies. A random-effects meta-analysis was performed using the standardized mean difference (SMD) and 95% confidence interval (CI). Sixteen RCTs with a total of 623 participants were selected for the final analysis. The analysis showed that exercise training improved the standard deviation of normal-to-normal intervals (SDNN) (SMD: 0.58 (0.16, 1.00); p = 0.007), the root mean square of successive differences in heart period series (RMSSD) (SMD: 0.84 (0.36, 1.31); p = 0.0005), and the absolute power of high-frequency band (HF) (SMD: 0.89 (0.27, 1.51); p = 0.005) parameters compared to the control group. Analysis of the moderator variables showed that the effect of exercise on HRV indices may be influenced by sex, age, and type of exercise used, specifically in HF band, absolute power of low-frequency band (LF), and LF/HF ratio parameters. Despite the limited number of existing RCTs related to the subject, the results suggest that exercise training enhances HRV parameters associated with vagal-related activity (RMSSD and HF) and both sympathetic and parasympathetic activities (SDNN). This study overcomes the lack of meta-analyses on the effects of exercise training on autonomic modulation among healthy adults and may bridge the gap in understanding the potential physiological underpinnings of the acknowledged positive health benefits of exercise.

The effects of irrelevant speech on physiological stress, cognitive performance, and subjective experience - Focus on heart rate variability

Irrelevant speech impairs cognitive performance, especially in tasks requiring verbal short-term memory. Working on these tasks during irrelevant speech can also cause a physiological stress reaction. The aim of this study was to examine heart rate variability (HRV) as a non-invasive and easy-to-use stress measure in an irrelevant speech paradigm. Thirty participants performed cognitive tasks (n-back and serial recall) during two sound conditions: irrelevant speech (50 dB) and quiet (33 dB steady-state noise). The influence of conditions as well as presentation orders of conditions were examined on performance, subjective experience, and physiological stress. Working during irrelevant speech compared to working during quiet reduced performance, namely accuracy, in the serial recall task. It was more annoying, heightened the perceived workload, and lowered acoustic satisfaction. It was related to higher physiological stress by causing faster heart rate and changes in HRV frequency-domain analysis (LF, HF and LF/HF). The order of conditions showed some additional effects. When speech was the first condition, 3-back performance was less accurate, and serial recall response times were longer, heart rate was faster, and successive heart beats had less variability (lower RMSSD) during speech than during quiet. When quiet was the first condition, heart rate was faster and reaction times in 3-back were slower during quiet than during speech. The negative effect of irrelevant speech was clear in experience, performance, and physiological stress. The study shows that HRV can be used as a physiological stress measure in irrelevant speech studies.

Association between heart rate variability metrics from a smartwatch and self-reported depression and anxiety symptoms: a four-week longitudinal study

Background

Elucidating the association between heart rate variability (HRV) metrics obtained through non-invasive methods and mental health symptoms could provide an accessible approach to mental health monitoring. This study explores the correlation between HRV, estimated using photoplethysmography (PPG) signals, and self-reported symptoms of depression and anxiety.

Methods

A 4-week longitudinal study was conducted among 47 participants. Time-domain and frequency-domain HRV metrics were derived from PPG signals collected via smartwatches. Mental health symptoms were evaluated using the Patient Health Questionnaire-9 (PHQ-9) and Generalized Anxiety Disorder-7 (GAD-7) at baseline, week 2, and week 4.

Results

Among the investigated HRV metrics, RMSSD, SDNN, SDSD, LF, and the LF/HF ratio were significantly associated with the PHQ-9 score, although the number of significant correlations was relatively small. Furthermore, only SDNN, SDSD and LF showed significant correlations with the GAD-7 score. All HRV metrics showed negative correlations with self-reported clinical symptoms.

Conclusions

Our findings indicate the potential of PPG-derived HRV metrics in monitoring mental health, thereby providing a foundation for further research. Notably, parasympathetically biased HRV metrics showed weaker correlations with depression and anxiety scores. Future studies should validate these findings in clinically diagnosed patients.

Direct and indirect effects of adiposity on markers of autonomic nervous system activity in older adults

Several cardiovascular disease (CVD) risk factors (e.g., hypertension, poor glycemic control) can affect and be affected by autonomic nervous system (ANS) activity. Since excess adiposity can influence CVD development through its effect on hypertension and diabetes mellitus, it is important to determine how adiposity and altered ANS activity are related. The present study employed structural equation modeling to investigate the relation between adiposity and ANS activity both directly and indirectly through biological variables typically associated with glycemic impairment and cardiac stress in older adults. Utilizing the Atherosclerosis Risk in Communities (ARIC) dataset, 1,145 non-smoking adults (74±4.8 yrs, 62.8% female) free from known CVD, hypertension, and diabetes and not currently taking beta-blockers were evaluated for fasting blood glucose (FBG), insulin, and HbA1c concentrations, waist circumference (WC), blood pressure (BP), and markers of ANS activity. WC was recorded just above the iliac crest and was used to reflect central adiposity. Resting 2-minute electrocardiograph recordings, pulse wave velocity, and ankle-brachial index data were used to assess the root mean square of successive differences in RR intervals (RMSSD) and the pre-ejection period (PEP), markers of parasympathetic and sympathetic activity, respectively. FBG, insulin, and HbA1c inferred a latent variable termed glycemic impairment (GI), whereas heart rate and diastolic BP inferred a latent variable termed cardiac stress (CS). The structural equation model fit was acceptable [root mean square error of approximation = 0.050 (90% CI = .036, .066), comparative fit index = .970, Tucker Lewis Index = 0.929], with adiposity having both significant direct (β = 0.208, p = 0.018) and indirect (β = -.217, p = .041) effects on PEP through GI. Adiposity displayed no significant direct effect on RMSSD. CS displayed a significant pathway (β = -0.524, p = 0.035) on RMSSD, but the indirect effect of WC on RMSSD through CS did not reach statistical significance (β = -0.094, p = 0.137). These results suggest that adiposity's relation to ANS activity is multifaceted, as increased central adiposity had opposing direct and indirect effects on markers of sympathetic activity in this population of older adults.

Evaluation of transformation invariant loss function with distance equilibrium in prediction of imaging photoplethysmography characteristics

Objective. Monitoring changes in human heart rate variability (HRV) holds significant importance for protecting life and health. Studies have shown that Imaging Photoplethysmography (IPPG) based on ordinary color cameras can detect the color change of the skin pixel caused by cardiopulmonary system. Most researchers employed deep learning IPPG algorithms to extract the blood volume pulse (BVP) signal, analyzing it predominantly through the heart rate (HR). However, this approach often overlooks the inherent intricate time-frequency domain characteristics in the BVP signal, which cannot be comprehensively deduced solely from HR. The analysis of HRV metrics through the BVP signal is imperative.

APPROACH

In this paper, the transformation invariant loss function with distance equilibrium (TIDLE) loss function is applied to IPPG for the first time, and the details of BVP signal can be recovered better. In detail, TIDLE is tested in four commonly used IPPG deep learning models, which are DeepPhys, EfficientPhys, Physnet and TS_CAN, and compared with other three loss functions, which are mean absolute error (MAE), mean square error (MSE), Neg Pearson Coefficient correlation (NPCC).

MAIN RESULTS

The experiments demonstrate that MAE and MSE exhibit suboptimal performance in predicting LF/HF across the four models, achieving the Statistic of Mean Absolute Error (MAES) of 25.94% and 34.05%, respectively. In contrast, NPCC and TIDLE yielded more favorable results at 13.51% and 11.35%, respectively. Taking into consideration the morphological characteristics of the BVP signal, on the two optimal models for predicting HRV metrics, namely DeepPhys and TS_CAN, the Pearson coefficients for the BVP signals predicted by TIDLE in comparison to the gold-standard BVP signals achieved values of 0.627 and 0.605, respectively. In contrast, the results based on NPCC were notably lower, at only 0.545 and 0.533, respectively.

SIGNIFICANCE

This paper contributes significantly to the effective restoration of the morphology and frequency domain characteristics of the BVP signal.

Inter-day reliability of heart rate complexity and variability metrics in healthy highly active younger and older adults

PURPOSE

To investigate the inter-day reliability of time-domain, frequency-domain, and nonlinear HRV metrics in healthy highly active younger and older adults. The study also assessed the effect of age on the HRV metrics.

METHODS

Forty-four older adults (34 M, 10F; 59 ± 5 years;V ˙ O 2peak  = 40.9 ± 7.6 ml kg-1 min-1) and twenty-two younger adults (16 M, 6F; 22 ± 4 years;V ˙ O 2peak  = 47.2 ± 12.8 ml kg-1 min-1) attended the laboratory. Visit one assessed aerobic fitness through an exercise test. In visits two and three, participants completed a 30-min supine RR interval measurement to derive the HRV metrics.

RESULTS

The younger group (YG) and older group (OG) demonstrated poor to good day-to-day relative and absolute reliability for all HRV metrics (OG, ICCs = 0.33 to 0.69 and between day CVs = 3.8 to 29.2%; YG, ICCs = 0.37 to 0.93 and between day CVs = 3.5 to 36.5%). There was a significant reduction in ApEn (P < 0.001), SampEn (P = 0.031), RMSSD (P < 0.001), SDNN (P < 0.001), LF power (P < 0.001) and HF power (P < 0.001), HRV metrics with ageing. There was no significant effect of age the complexity metrics DFA α1 (P = 0.107), α2 (P = 0.147) and CI-8 (P = 0.493).

CONCLUSION

HRV metrics are reproducible between days in both healthy highly active younger and older adults. There is a decline in linear and nonlinear HRV metrics with age, albeit there being no age-related change in the nonlinear metrics, DFA α1, α2 and CI-8.

Heart rate and heart rate variability in obsessive-compulsive disorder: Evidence from patients and unaffected first-degree relatives

Altered heart rate (HR) and heart rate variability (HRV) are common observations in psychiatric disorders. Yet, few studies have examined these cardiac measures in obsessive-compulsive disorder (OCD). The current study aimed to investigate HR and HRV, indexed by the root mean square of successive differences (RMSSD) and further time domain indices, as putative biological characteristics of OCD. Electrocardiogram was recorded during a five-minute resting state. Group differences between patients with OCD (n = 96), healthy participants (n = 112), and unaffected first-degree relatives of patients with OCD (n = 47) were analyzed. As potential moderators of group differences, we examined the influence of age and medication, respectively. As results indicated, patients with OCD showed higher HR and lower HRV compared to healthy participants. These group differences were not moderated by age. Importantly, subgroup analyses showed that only medicated patients displayed lower HRV compared to healthy individuals, while HR alterations were evident in unmedicated patients. Regarding unaffected first-degree relatives, group differences in HRV remained at trend level. Further, an age-moderated group differentiation showed that higher HRV distinguished relatives from healthy individuals in young adulthood, whereas at higher age lower HRV was indicative of relatives. Both the role of familial risk and medication in HRV alterations need further elucidation. Pending future studies, alterations in HR and potentially HRV might serve as useful indices to characterize the pathophysiology of OCD.

The effectiveness of an osteopathic manual technique compared with a breathing exercise on vagal tone as indicated by heart rate variability, a crossover study

INTRODUCTION

Parasympathetic nervous system (PSNS) function can be inferred by heart rate variability (HRV) providing indications about an individual's health. Manual therapy may influence PSNS function, however the research outcomes in this regard are equivocal. This study explored the PSNS effect of a measured breathing technique with suboccipital balanced ligamentous tension, an osteopathic manipulative therapy technique.

METHODS

Healthy adult participants in this crossover study (n = 18) were randomly allocated into two groups with differing order of interventions. A 1:1 breathing rate of 6 breaths per minute maintained for 5 min was compared to the osteopathic intervention. HRV was measured for 5 min before and after each intervention and analysed using the root mean square of successive differences (RMSSD) between normal heartbeats and high frequency normalised units (HFnu).

RESULTS

The RMSSD data demonstrated no significant difference between groups or within groups (p > 0.05) over time. HFnu results showed a significant between-group difference over the four time points (p = 0.004) with a medium effect size (ηp2 = 0.240), and no significant within-group difference (p > 0.05).

DISCUSSION

The osteopathic intervention raised HRV to a small extent, however measured breathing lowered HRV. In the group that received the osteopathic technique first, HFnu values continued to rise post-osteopathic treatment possibly indicating an increasing parasympathetic effect over time. Recommendations for future studies include changing the breathing ratio to ensure parasympathetic response, take into account potential delayed effects of interventions, consider outcome measures less variable than HRV, and longer follow up times.

CONCLUSION

This study suggests parasympathetic stimulation may occur with the application of suboccipital balanced ligamentous tension and sympathetic stimulation from measured breathing.

The relationship between sustained attention and parasympathetic functioning

Sustained attention (SA) is an important cognitive ability that plays a crucial role in successful cognitive control. Resting vagally-mediated heart rate variability (vmHRV) has emerged as an informative index of parasympathetic nervous system activity and a sensitive correlate of individual differences in cognitive control. However, it is unclear how resting vmHRV is associated with individual differences in sustained attention. The primary aim of the current study was to assess if resting vmHRV was associated with individual differences in performance on a neuropsychological assessment of sustained attention. We further aimed to characterize the relationship between resting vmHRV and dispositional factors related to sustained attention, specifically attentional errors in daily life, self-regulation, mindfulness and media-multitasking. Based on previous work, we hypothesized higher resting vmHRV would be associated with better sustained attention across task-based and self-report measures. We did not find resting vmHRV to be significantly associated with performance measures on a task-based assessment of sustained attention. Further, resting vmHRV was not significantly associated with attention errors, self-regulation, mindfulness, or media-multitasking. This work stands to expand the current understanding between parasympathetic functioning, cognition, and behavior, investigating the unexplored domain of sustained attention and related dispositional factors.

Virtual Reality Breathing Interventions for Mental Health: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

Breathing exercises have been shown to reduce mental health problems among clinical and non-clinical populations. Although virtual reality (VR) breathing interventions are assumed to have potential benefits, it remains unclear whether VR breathing interventions are more effective at improving mental health than non-VR breathing interventions. We conducted a systematic literature search in six electronic databases (Web of Science, PsycINFO, Embase, Cochrane Central Register of Controlled Trials, Scopus, and PubMed) from inception to 30th September, 2022. We included randomized controlled trials in adults evaluating effects of VR compared to non-VR breathing interventions on primary outcomes of mental health (stress, anxiety and mood), and secondary outcomes of physiological stress measures (e.g., heart rate (HR), heart rate variability (HRV)). Within these selected studies, we explored differences in likeability and future use between VR and non-VR breathing interventions. 2.848 records were identified of which 65 full-text articles were assessed. Six RCTs were included, of which five were suitable for meta-analyses. Comparing VR to non-VR breathing interventions, there were no significant differences in overall mental health, stress, anxiety or mood, nor in HR or HRV. There was no evidence that participants liked VR breathing interventions more than non-VR, nor would use them more in the future. These results suggest that there is no evidence that VR breathing interventions are more effective than non-VR in improving mental health outcomes, HR, HRV. Further research is required to determine whether there may be advantages to longer-term VR-implementation and practice, and explore possible mechanisms.

The Pulse of Singapore: Short-Term HRV Norms

Short-term heart rate variability (HRV) is increasingly used to assess autonomic nervous system activity and found to be useful for monitoring and providing care due to its quick measurement. With evidence of low HRV associated with chronic diseases, mental disorders, and an increased risk of cardiovascular disease, having normative data of HRV across the age spectrum would be useful for monitoring health and well-being of a population. This study examines HRV of healthy Singapore sample, with ages ranging from 10 to 89 years. Short-term HRV of five minutes was measured from 2,143 participants. 974 males and 1,169 females, and overall HRV was found to be 42.4ms (RMSSD) and 52.0 ms (SDNN) with a further breakdown of HRV by age and gender. Overall HRV declined with age and gender, although gender differences dissipated in the 60s age range onwards, with the 50s age range having the sharpest decline in HRV. Short-term HRV norms were similar to Nunan et al.'s (2010) systematic review in various populations and less similar to Choi et al.'s (2020) study on Koreans.

The Appropriateness of Medical Devices Is Strongly Influenced by Sex and Gender

Until now, research has been performed mainly in men, with a low recruitment of women; consequentially, biological, physiological, and physio-pathological mechanisms are less understood in women. Obviously, without data obtained on women, it is impossible to apply the results of research appropriately to women. This issue also applies to medical devices (MDs), and numerous problems linked to scarce pre-market research and clinical trials on MDs were evidenced after their introduction to the market. Globally, some MDs are less efficient in women than in men and sometimes MDs are less safe for women than men, although recently there has been a small but significant decrease in the sex and gender gap. As an example, cardiac resynchronization defibrillators seem to produce more beneficial effects in women than in men. It is also important to remember that MDs can impact the health of healthcare providers and this could occur in a sex- and gender-dependent manner. Recently, MDs' complexity is rising, and to ensure their appropriate use they must have a sex-gender-sensitive approach. Unfortunately, the majority of physicians, healthcare providers, and developers of MDs still believe that the human population is only constituted by men. Therefore, to overcome the gender gap, a real collaboration between the inventors of MDs, health researchers, and health providers should be established to test MDs in female and male tissues, animals, and women.

Reliability and validity of a non-linear index of heart rate variability to determine intensity thresholds

Exercise intensity distribution is crucial for exercise individualization, prescription, and monitoring. As traditional methods to determine intensity thresholds present limitations, heart rate variability (HRV) using DFA a1 has been proposed as a biomarker for exercise intensity distribution. This index has been associated with ventilatory and lactate thresholds in previous literature. This study aims to assess DFA a1's reliability and validity in determining intensity thresholds during an incremental cycling test in untrained healthy adults. Sixteen volunteers (13 males and 3 females) performed two identical incremental cycling stage tests at least 1 week apart. First and second ventilatory thresholds, lactate thresholds, and HRV thresholds (DFA a1 values of 0.75 and 0.5 for HRVT1 and HRVT2, respectively) were determined in heart rate (HR), relative oxygen uptake (VO2rel), and power output (PO) values for both tests. We used intraclass correlation coefficient (ICC), change in mean, and typical error for the reliability analysis, and paired t-tests, correlation coefficients, ICC, and Bland-Altman analysis to assess the agreement between methods. Regarding reliability, HRV thresholds showed the best ICCs when measured in PO (HRVT1: ICC = .87; HRVT2: ICC = .97), comparable to ventilatory and lactate methods. HRVT1 showed the strongest agreement with LA 2.5 in PO (p = 0.09, r = .93, ICC = .93, bias = 9.9 ± 21.1), while HRVT2 reported it with VT2 in PO (p = 0.367, r = .92, ICC = .92, bias = 5.3 ± 21.9). DFA a1 method using 0.75 and 0.5 values is reliable and valid to determine HRV thresholds in this population, especially in PO values.

Normative values of short-term heart rate variability in a cross-sectional study of a Danish population. The DanFunD study

AIMS

The autonomic nervous system includes parasympathetic and sympathetic components that monitor and regulate most of the bodily functions and play a central role in the physiology and homeostasis of the human body. Heart rate variability is a non-invasive tool for quantification of rhythmic fluctuations in heart rate that reflects the function of the autonomic nervous system. The study aims to describe the heart rate variability distribution in the general population, stratified in sex and age groups, which is currently insufficiently described.

METHODS

A cross-sectional population-based study recruited participants in 10 municipalities in the western part of the greater Copenhagen area in Denmark, including 6891 men and women aged 18-72 years (participation rate was 29.5%). Short-term heart rate variability measures were obtained and related to age and gender.

RESULTS

Both time and frequency domain measures showed a huge variation in the different sex and age groups. Women had a higher median heart rate than men, and the association with age was U-shaped. Measures indicating a predominance of the parasympathetic component in relation to the sympathetic component were more frequent in women and younger age groups.

CONCLUSIONS

Both sex and age influence the heart rate variability in this adult Danish population. Therefore, our age- and sex-related reference values of heart rate variability in the time and frequency domain should be used in further epidemiological and clinical research.

Respiratory sinus arrhythmia (RSA), vagal tone and biobehavioral integration: Beyond parasympathetic function

Linchpin to the entire area of psychophysiological research and discussion of the vagus is the respiratory and cardiovascular phenomenon known as respiratory sinus arrhythmia (RSA; often synonymous with high-frequency heart-rate variability when it is specifically linked to respiratory frequency), i.e. rhythmic fluctuations in heart rate synchronized to inspiration and expiration. This article aims 1) to clarify concepts, terms and measures commonly employed during the last half century in the scientific literature, which relate vagal function to psychological processes and general aspects of health; and 2) to expand upon an earlier theoretical model, emphasizing the importance of RSA well beyond the current focus upon parasympathetic mechanisms. A close examination of RSA and its relations to the vagus may 1) dispel certain commonly held beliefs about associations between psychological functioning, RSA and the parasympathetic nervous system (for which the vagus nerve plays a major role), and 2) offer fresh perspectives about the likely functions and adaptive significance of RSA, as well as RSA's relationship to vagal control. RSA is neither an invariably reliable index of cardiac vagal tone nor of central vagal outflow to the heart. The model here presented posits that RSA represents an evolutionarily entrenched, cardiovascular and respiratory phenomenon that significantly contributes to meeting continuously changing metabolic, energy and behavioral demands.

Dyadic and Individual Variation in 24-Hour Heart Rates of Cancer Patients and Their Caregivers

BACKGROUND

Twenty-four-hour heart rate (HR) integrates multiple physiological and psychological systems related to health and well-being, and can be continuously monitored in high temporal resolution over several days with wearable HR monitors. Using HR data from two independent datasets of cancer patients and their caregivers, we aimed to identify dyadic and individual patterns of 24 h HR variation and assess their relationship to demographic, environmental, psychological, and clinical variables of interest.

METHODS

a novel regularized approach to high-dimensional canonical correlation analysis (CCA) was used to identify factors reflecting dyadic and individual variation in the 24 h (circadian) HR trajectories of 430 people in 215 dyads, then regression analysis was used to relate these patterns to explanatory variables.

RESULTS

Four distinct factors of dyadic covariation in circadian HR were found, contributing approximately 7% to overall circadian HR variation. These factors, along with non-dyadic factors reflecting individual variation exhibited diverse and statistically robust patterns of association with explanatory variables of interest.

CONCLUSIONS

Both dyadic and individual anomalies are present in the 24 h HR patterns of cancer patients and their caregivers. These patterns are largely synchronous, and their presence robustly associates with multiple explanatory variables. One notable finding is that higher mood scores in cancer patients correspond to an earlier HR nadir in the morning and higher HR during the afternoon.

Uncertainties in the Analysis of Heart Rate Variability: A Systematic Review

Heart rate variability (HRV) is an important metric with a variety of applications in clinical situations such as cardiovascular diseases, diabetes mellitus, and mental health. HRV data can be potentially obtained from electrocardiography and photoplethysmography signals, then computational techniques such as signal filtering and data segmentation are used to process the sampled data for calculating HRV measures. However, uncertainties arising from data acquisition, computational models, and physiological factors can lead to degraded signal quality and affect HRV analysis. Therefore, it is crucial to address these uncertainties and develop advanced models for HRV analysis. Although several reviews of HRV analysis exist, they primarily focus on clinical applications, trends in HRV methods, or specific aspects of uncertainties such as measurement noise. This paper provides a comprehensive review of uncertainties in HRV analysis, quantifies their impacts, and outlines potential solutions. To the best of our knowledge, this is the first study that presents a holistic review of uncertainties in HRV methods and quantifies their impacts on HRV measures from an engineer's perspective. This review is essential for developing robust and reliable models, and could serve as a valuable future reference in the field, particularly for dealing with uncertainties in HRV analysis.

Sex differences in the age-related decrease of spontaneous baroreflex function in healthy individuals

The baroreflex is a powerful physiological mechanism for rapidly adjusting heart rate in response to changes in blood pressure. Spontaneous baroreflex sensitivity (BRS) has been shown to decrease with age. However, studies of sex differences in these age-related changes are rare. Here we investigated several markers of spontaneous baroreflex function in a large sample of healthy individuals. Cardiovascular signals were recorded in the supine position under carefully controlled resting conditions. After quality control, n = 980 subjects were divided into five age groups [age < 30 yr (n = 612), 30-39 yr (n = 140), 40-49 yr (n = 95), 50-59 yr (n = 61), and >60 yr (n = 72)]. Spontaneous baroreflex function was assessed in the time domain (bradycardic and tachycardic slope) and in the frequency domain in the low- and high-frequency band (LF-α, HF-α) applying the transfer function. General linear models showed a significant effect of factor age (P < 0.001) and an age × sex interaction effect (P < 0.05) on each indicator of the baroreflex function. Simple main effects showed a significantly higher BRS as indicated by tachycardic slope, LF-α and HF-α in middle-aged women compared with men (30-39 yr) and higher LF-α, bradycardic and tachycardic slope in men compared with women of the oldest age group (>60 yr). Changes in BRS over the lifespan suggest that baroreflex function declines more slowly but earlier in life in men than in women. Our findings could be linked to age-related changes in major sex hormone levels, suggesting significant implications for diverse cardiovascular outcomes and the implementation of targeted preventive strategies.NEW & NOTEWORTHY In this study, we demonstrate that the age-related decrease of spontaneous baroreflex sensitivity is different in men and women by analyzing resting state cardiovascular data of a large sample of healthy individuals.

Cardioprotective Effects of Sodium-Glucose Cotransporter 2 Inhibitors and Their Possible Association With Normalization of the Circadian Index of Heart Rhythm

BACKGROUND

Updated recommendations for the treatment of heart failure with reduced ejection fraction (HFrEF) include sodium-glucose cotransporter 2 (SGLT2) inhibitors and other long-established HFrEF therapies. These drugs' mechanisms of action have yet to be fully clarified.

OBJECTIVE

This study evaluated the effects of SGLT2 inhibitors on the modulation of autonomic function at 1 month beyond conventional HF therapy.

METHODS

This single-center, observational, prospective study was conducted from January 2020 to December 2022. Patients with type 2 diabetes who had ischemic HFrEF and met the study criteria were considered for SGLT2 inhibitor treatment with empagliflozin or dapagliflozin. Changes in the circadian index were used as the primary outcome to assess the early effects of SGLT2 inhibitors on autonomic function. Changes in functional effort capacity and laboratory findings were also evaluated. Participants' circadian index was measured by a 24-hour rhythm Holter monitoring recorder (BTL-08 Holter H100). A symptom-limited treadmill test assessed patients' effort capacities. Tests were repeated after 1 month of therapy.

RESULTS

The mean (SD) age of the 151 participants was 56.95 (7.29) years; their mean (SD) left ventricular EF was 35.69% (7.10%), and 95 participants were men (62.9%). From baseline to 1 month, mean (SD) daytime heart rate (80.63 [9.17] vs 77.67 [8.04] beats per minute; P = .004) and nighttime heart rate (76.83 [11.34] vs 73.81 [10.25] beats per minute; P = .03) decreased significantly. Variation in the circadian indexes (mean [SD], 1.04 [0.02] vs 1.10 [0.04]; P < .001) was statistically significant, favoring increased modulation of autonomic function. The increases in exercise duration (mean [SD], 8.88 [3.69] minutes and median [IQR], 8.81 [5.76-12.13] minutes vs 9.72 [3.14] and 9.59 [7.24-12.22] minutes; P = .04) and exercise capacity (mean [SD], 203.38 [65.18] m and median [IQR], 119.22 [149.43-259.15] m vs 335.61 [51.39] and 325.79 [293.59-376.91] m; P < .001] were also significant.

CONCLUSION

The use of SGLT2 inhibitors during early treatment can favorably affect both autonomic dysfunction and functional effort capacity of patients with type 2 diabetes with ischemic HFrEF.

The short-term effect of weather variables on heart rate variability in patients after open-heart surgery

The aim of the study was to detect the associations between heart rate variability (HRV) and weather variables in patients who underwent coronary artery bypass grafting or valve surgery. The study was performed in Kaunas, Lithuania, during 2008-2012. We used data of 220 patients. HRV was assessed by a 5-minute electrocardiogram. The data were collected at 1.5 months, 1 year, and 2 years after the surgery (495 measurements). A negative association of standard deviation of beat-to-beat interval (SDNN), very low frequency (VLF), low frequency, and high frequency (HF) powers with a decrease in air temperature (T) during a 3-day period in the range of T < 1°C wind speed >2.75 knots 2 days before, and the daily North Atlantic Oscillation indices were observed. The effect of wind speed on SDNN and VLF power was stronger in males. Two days after relative humidity >89%, a lower mean VLF and higher HF in normalized units were found; in females, this effect was stronger 1.5 months after the surgery. Among patients after open-heart surgery, the HRV variables may be related to specific weather changes and the effect of weather was different for males and females and at different times after the surgery.

Acute Effects of Fatigue on Cardiac Autonomic Nervous Activity

The onset of fatigue disrupts the functioning of the autonomic nervous system (ANS), potentially elevating the risk of life-threatening incidents and impairing daily performance. Previous studies mainly focused on physical fatigue (PF) and mental fatigue (MF) effects on the ANS, with limited knowledge concerning the influence of physical-mental fatigue (PMF) on ANS functionality. This study aimed to assess the immediate impact of PMF on ANS function and to compare its effects with those of PF and MF on ANS function. Thirty-six physically active college students (17 females) without burnout performed 60-min cycling exercises, AX-Continuous Performance Task (AX-CPT), and cycling combined with AX-CPT to induce PF, MF, and PMF respectively. Subjective fatigue levels were measured using the Rating of Perceived Exertion scale and the Visual Analog Scale-Fatigue. Heart rate variability was measured before and after each protocol to assess cardiac autonomic function. The proposed tasks successfully induced PF, MF, and PMF, demonstrated by significant changes in subjective fatigue levels. Compared with baseline, PMF decreased the root mean square of successive differences (RMSSD) between normal heartbeats (P < 0.001, d = 0.50), the standard deviation of normal-to-normal RR intervals (SDNN) (P < 0.01, d = 0.33), and the normalized high-frequency (nHF) power (P < 0.001, d = 0.32) while increased the normalized low-frequency (nLF) power (P < 0.001, d = 0.35) and the nLF/nHF ratio (P < 0.001, d = 0.40). Compared with MF, PMF significantly decreased RMSSD (P < 0.001, η2 = 0.431), SDNN (P < 0.001, η2 = 0.327), nLF (P < 0.01, η2 = 0.201), and nHF (P < 0.001, η2 = 0.377) but not the nLF/nHF ratio. There were no significant differences in ΔHRV (i.e., ΔRMSSD, ΔSDNN, ΔnLF/nHF, ΔnLF, and ΔnHF), heart rate, and training impulse between PF- and PMF-inducing protocols. Cognitive performance (i.e., accuracy) in AX-CPT during the PMF-inducing protocol was significantly lower than that during the MF-inducing protocol (P < 0.001, η2 = 0.101). PF and PMF increased sympathetic activity and decreased parasympathetic activity, while MF enhanced parasympathetic activity.

Attachment insecurity, heart rate variability, and perceived social support in a diverse sample of young adults

Psychological and physical factors are robustly associated with perceived social support. Drawing from the literature on attachment style in adults and psychophysiology, we examined the possibility that the interaction of attachment insecurity and resting heart rate variability (HRV) was associated with perceived social support in a diverse sample of young adults living in the U.S (N = 145, Mage = 20.45) that was majority Latino (n = 77). Analyses revealed three key findings. First, in the overall sample, attachment avoidance and attachment anxiety were negatively associated with perceived social support, but in the Latino sample, only attachment avoidance was negatively associated with perceived social support. Second, HRV was not associated with perceived social support in the overall sample nor in the Latino sample. Third, attachment insecurity and HRV interacted to predict perceived social support only in the Latino sample such that, for those with lower levels of HRV, attachment anxiety was positively associated with perceived social support. This study underscores the importance of examining both psychological and physiological processes with careful consideration of ethnicity/culture in order to better understand perceived social support.

Heart rate variability as a marker and predictor of inflammation, nosocomial infection, and sepsis - A systematic review

PURPOSE

The autonomic nervous system interacts with the immune system via the inflammatory response. Heart rate variability (HRV), a marker of autonomic activity, is associated with inflammation, and nosocomial infections/sepsis, and has clinical implications for the monitoring of at-risk patients. Due to the vagal tone's influence on anti-inflammatory immune response, this association may predominately be reflected by vagally-mediated HRV indices. However, HRV's predictive significance on inflammation/infection remains unclear.

METHODS

843 studies examining the associations/prognostic value of HRV indices on inflammation, and nosocomial infection/sepsis were screened in this systematic review. According to inclusion and exclusion criteria, 68 associative studies and 14 prediction studies were included.

RESULTS

HRV and pro-inflammatory state were consistently associated in healthy subjects and patient groups. Pro-inflammatory state was related to reduced total power HRV including vagally- and non-vagally-mediated HRV indices. Similar, compared to controls, HRV reductions were observed during nosocomial infections/sepsis. Only limited evidence supports the predictive value of HRV in the development of nosocomial infections/sepsis. Reduced very low frequency power HRV showed the highest predictive value in adults, even with different clinical conditions. In neonates, an increased heart rate characteristic score, combining reduced total power HRV, decreased complexity, and vagally-dominated asymmetry, predicted sepsis.

CONCLUSIONS

Pro-inflammatory state is related to an overall reduction in HRV rather than a singular reduction in vagally-mediated HRV indices, reflecting the complex autonomic-regulatory changes occurring during inflammation. The potential benefit of using continuous HRV monitoring for detecting nosocomial infection-related states, and the implications for clinical outcome, need further clarification.

Unraveling Autonomic Dysfunction in GBA-Related Parkinson's Disease

Background

Patients with Parkinson's disease (PD) and GBA gene mutations (GBA-PD) develop nonmotor complications more frequently than noncarriers. However, an objective characterization of both cardiovascular and sudomotor autonomic dysfunction using extensive clinical and instrumental measures has never been provided so far. Survival is reduced in GBA-PD regardless of age and dementia, suggesting that other hitherto unrecognized factors are involved.

Objectives

To provide instrumental measures of pattern and severity of autonomic dysfunction in GBA-PD and explore their correlation with other non-motor symptoms and implications for clinical practice.

Methods

In this cross-sectional study, 21 GBA-PD and 24 matched PD noncarriers underwent extensive assessment of motor and non-motor features, including neuropsychological testing. Cardiovascular autonomic function was explored through a comprehensive battery of indexes, including power spectral analysis of the R-R intervals and blood pressure short-term variability during resting state and active maneuvers. Dynamic Sweat Test was used to assess post-ganglionic sudomotor dysfunction.

Results

Despite minimal or absent clinical correlates, cardiovagal and sympathetic indexes, heart rate variability parameters and sudomotor postganglionic function were more severely impaired in GBA-PD than noncarriers (overcoming relatively preserved compensatory peripheral sympathetic function), suggesting more prominent cardiac sympatho-vagal demodulation, efferent baroreflex failure and peripheral sympathetic dysfunction in GBA-PD. Cardiovascular dysautonomia showed marginal correlations with cognitive impairment.

Conclusions

Compared to PD noncarriers, GBA-PD display more severe instrumental autonomic abnormalities, which may be underestimated by purely clinical measures, despite their relevance on morbidity and mortality. This supports the necessity of implementing instrumental autonomic assessment in all GBA-PD, regardless of clinically overt symptoms.

Age and Gender Impact on Heart Rate Variability towards Noninvasive Glucose Measurement

Heart rate variability (HRV) parameters can reveal the performance of the autonomic nervous system and possibly estimate the type of its malfunction, such as that of detecting the blood glucose level. Therefore, we aim to find the impact of other factors on the proper calculation of HRV. In this paper, we research the relation between HRV and the age and gender of the patient to adjust the threshold correspondingly to the noninvasive glucose estimator that we are developing and improve its performance. While most of the literature research so far addresses healthy patients and only short- or long-term HRV, we apply a more holistic approach by including both healthy patients and patients with arrhythmia and different lengths of HRV measurements (short, middle, and long). The methods necessary to determine the correlation are (i) point biserial correlation, (ii) Pearson correlation, and (iii) Spearman rank correlation. We developed a mathematical model of a linear or monotonic dependence function and a machine learning and deep learning model, building a classification detector and level estimator. We used electrocardiogram (ECG) data from 4 different datasets consisting of 284 subjects. Age and gender influence HRV with a moderate correlation value of 0.58. This work elucidates the intricate interplay between individual input and output parameters compared with previous efforts, where correlations were found between HRV and blood glucose levels using deep learning techniques. It can successfully detect the influence of each input.

Insights into vascular physiology from sleep photoplethysmography

STUDY OBJECTIVES

Photoplethysmography (PPG) in consumer sleep trackers is now widely available and used to assess heart rate variability (HRV) for sleep staging. However, PPG waveform changes during sleep can also inform about vascular elasticity in healthy persons who constitute a majority of users. To assess its potential value, we traced the evolution of PPG pulse waveform during sleep alongside measurements of HRV and blood pressure (BP).

METHODS

Seventy-eight healthy adults (50% male, median [IQR range] age: 29.5 [23.0, 43.8]) underwent overnight polysomnography (PSG) with fingertip PPG, ambulatory blood pressure monitoring, and electrocardiography (ECG). Selected PPG features that reflect arterial stiffness: systolic to diastolic distance (∆T_norm), normalized rising slope (Rslope) and normalized reflection index (RI) were derived using a custom-built algorithm. Pulse arrival time (PAT) was calculated using ECG and PPG signals. The effect of sleep stage on these measures of arterial elasticity and how this pattern of sleep stage evolution differed with participant age were investigated.

RESULTS

BP, heart rate (HR) and PAT were reduced with deeper non-REM sleep but these changes were unaffected by the age range tested. After adjusting for lowered HR, ∆T_norm, Rslope, and RI showed significant effects of sleep stage, whereby deeper sleep was associated with lower arterial stiffness. Age was significantly correlated with the amount of sleep-related change in ∆T_norm, Rslope, and RI, and remained a significant predictor of RI after adjustment for sex, body mass index, office BP, and sleep efficiency.

CONCLUSIONS

The current findings indicate that the magnitude of sleep-related change in PPG waveform can provide useful information about vascular elasticity and age effects on this in healthy adults.

Heart Rate Variability Assessment of Land Navigation and Load Carriage Activities in Specialist Police Selection

Police tactical group (PTG) personnel are exposed to physical, mental, and emotional stressors. Consequently, PTG selection courses (SCs) impart similar challenges, often resulting in candidate attrition. Holistic assessment may provide additional support to stakeholders given these risks. Heart Rate Variability (HRV) is an objective holistic stress measure that may be applicable in PTG SCs but has not been thoroughly researched. Therefore, this study aimed to report HRV data in an end-user accessible format and determine the relationship between HRV and attrition. A total of 18 qualified Australian State law enforcement officers completed a 1-day physical readiness assessment. Of those, six males progressed to an additional two-day course, on which this study is focused. This two-day selection consisted of additional physical challenges and occupational assessments. HRV was obtained from 2-lead ECGs and defined as the percentage of R-R intervals that varied by ≥50 ms (pRR50). Data were summarized in a heat map of consecutive short-term analyses. Three candidates withdrew. A logistic regression based on heat map data found high HRV was significant for predicting attrition, χ2 (6) = 8.318, p = 0.004. HRV may provide insight for PTG stakeholders monitoring attrition. While the sample size was limited and replication is needed, this study tentatively establishes value for HRV monitoring in PTG SCs.

Impact of air pollution on cardiovascular aging

The world population is aging rapidly, and by some estimates, the number of people older than 60 will double in the next 30 years. With the increase in life expectancy, adverse effects of environmental exposures start playing a more prominent role in human health. Air pollution is now widely considered the most detrimental of all environmental risk factors, with some studies estimating that almost 20% of all deaths globally could be attributed to poor air quality. Cardiovascular diseases are the leading cause of death worldwide and will continue to account for the most significant percentage of non-communicable disease burden. Cardiovascular aging with defined pathomechanisms is a major trigger of cardiovascular disease in old age. Effects of environmental risk factors on cardiovascular aging should be considered in order to increase the health span and reduce the burden of cardiovascular disease in older populations. In this review, we explore the effects of air pollution on cardiovascular aging, from the molecular mechanisms to cardiovascular manifestations of aging and, finally, the age-related cardiovascular outcomes. We also explore the distinction between the effects of air pollution on healthy aging and disease progression. Future efforts should focus on extending the health span rather than the lifespan.