Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology. Circulation. 1996;93:1043-1065. [PMID: 8598068 DOI: 10.1161/01.cir.93.5.1043]

Reducing decision-making deficits in patients with brain injury: effect of slow-paced breathing

Impairments in decision-making have been reported in brain-damaged (stroke/traumatic brain injury) patients with a wide range of lesion sites. Here, we propose that the performances of patients in complex sequential decision-making (DM) tasks can be explained by their negative affectivity, leading to deliberative processing associated with poor DM performances. We assumed that a slow-paced breathing (SPB) training, by reducing negative affectivity would improve performances in a complex DM task. For 24 days, 34 brain-damaged patients (16 males and 18 females; 12 had a hemorrhagic stroke, 17 with an ischemic stroke and 5 with a TBI), practiced either daily SPB or sham trainings for five min, three times a day. Before and after training, we assessed their vagal tone (electrocardiogram-ECG), affectivity (Positive and Negative Affect Schedule-PANAS) and certainty level (Dimensional Ratings Questionnaire-DRQ) and their performance on the Iowa Gambling Task. All participants showed initial weak performance, which improved only for patients in the SPB training condition. These results suggest that DM disorders in brain-damaged patients can be the consequence of their poor information processing strategy rather than an impairment in their DM abilities. Second, we showed that SPB could be efficient to normalize DM processes in brain injury patients.

Association Between Surgeon Stress and Major Surgical Complications

Importance

Surgeon stress can influence technical and nontechnical skills, but the consequences for patient outcomes remain unknown.

Objective

To investigate whether surgeon physiological stress, as assessed by sympathovagal balance, is associated with postoperative complications.

Design, Setting, and Participants

This multicenter prospective cohort study included 14 surgical departments involving 7 specialties within 4 university hospitals in Lyon, France. Exclusion criteria consisted of patient age younger than 18 years, palliative surgery, incomplete operative time-stamping data, procedures with a duration of less than 20 minutes, and invalid surgeon heart rate variability (HRV) data. Data were accrued between November 1, 2020, and December 31, 2021, with 30-day follow-up completed on May 8, 2022. Analyses were performed from January 1 to May 31, 2024.

Exposure

Sympathovagal balance of the attending surgeon in the first 5 minutes of surgery.

Main Outcomes and Measures

Major surgical complications, extended intensive care unit stay, and mortality within 30 days, after adjustment via mixed-effects multivariable logistic regression for surgeon age, professional status, the time of incision, the random effect of the surgeon, and a composite risk score incorporating patient comorbidities and surgery characteristics. Sympathovagal balance was quantified by the low frequency to high frequency (LF:HF) ratio derived from HRV data measured by chest monitors worn intraoperatively. The LF:HF ratio was normalized at the surgeon level to the median value observed for each surgeon during the study period to control for baseline differences.

Results

A total of 793 surgical procedures performed by 38 attending surgeons were included in the analysis. Median patient age was 62 (IQR, 47-72) years, and 412 (52.0%) were female, with a median of 2 (IQR, 1-4) comorbidities. Median surgeon age was 46 (IQR, 39-52) years, 39 (78.9%) were male, and 22 (57.9%) were professors. Median surgeon heart rate was 88 (IQR, 77-99) beats per minute. Median surgeon LF:HF ratio was 7.16 (IQR, 4.52-10.72) before and 1.00 (IQR, 0.71-1.32) after normalization. Increased surgeon sympathovagal balance during the first 5 minutes of surgery was associated with significantly reduced major surgical complications (adjusted odds ratio [AOR], 0.63; 95% CI, 0.41-0.98; P = .04), though not with reduced intensive care unit stay (AOR, 0.34; 95% CI, 0.11-1.01; P = .05) or mortality (AOR, 0.18; 95% CI, 0.03-1.03; P = .05).

Conclusions and Relevance

Increased surgeon stress at the beginning of a procedure was associated with improved clinical patient outcomes. The results are illustrative of the complex relationship between physiological stress and performance, identify a novel association between measurable surgeon human factors and patient outcomes, and may highlight opportunities to improve patient care.

Daily physical activity habits influence surgeons' stress in the operating room: a prospective cohort study

BACKGROUND

Exercise training improves heart rate variability, and evidence suggests it can mitigate the detrimental effects of stress. This study aims to evaluate the relationship between surgeons' physical activity habits and their stress, assessed as heart rate variability, at the start of surgery.

MATERIALS AND METHODS

This multispecialty prospective cohort study included surgeons from fourteen cardiac, endocrine, digestive, gynecologic, orthopedic, thoracic, and urologic surgical departments of four university hospitals. Surgeons wore accelerometers 24/7 from 1 November 2020 to 31 December 2021 to quantify the mean daily step counts and daily sedentary time for 7 days prior to each operation. RMSSD, the root mean square of successive differences between normal heart beats, is a heart rate variability (HRV) metric that reflects cardiac vagal tone. We evaluated RMSSD during the first 5 minutes of surgeries performed over five 15-day periods. Data were analyzed using a multivariable linear mixed model with a random effect for surgeons.

RESULTS

We analyzed 722 surgeries performed by 37 surgeons (median age = 47 (IQR 42-55); 29 (78.4%) male). On average (SD), surgeons walked 9762 (2447) steps and were sedentary 391 (102) minutes daily. The model showed a positive relationship between steps and cardiac vagal tone, with an increase in lnRMSSD (0.028, 95% CI 0.003 to 0.053, P = 0.026) for every 1000 more steps per day, but not for sedentary behavior. Surgeon professors presented lower lnRMSSD (-0.437, -0.749 to -0.126, P = 0.006), as did surgeons who spent less total time operating over the study period (-0.337, -0.646 to -0.027, P = 0.033), compared to their counterparts.

CONCLUSIONS

Higher daily step counts the week before surgery were associated with increased cardiac vagal tone, indicating lower stress levels at the beginning of surgery. This relationship highlights the influence of physical activity on surgeons' stress in the operating room.

Cardiovascular autonomic neuropathy is associated with SLEDAI in patients with systemic lupus erythematosus

INTRODUCTION

As a prevalent and severe complication of systemic lupus erythematosus (SLE), cardiovascular autonomic neuropathy (CAN) has garnered increasing attention. Reports suggested that CAN may be related to the disease activity of SLE. This study aims to explore whether Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) is associated with CAN and to evaluate its diagnostic value for CAN.

METHOD

Altogether, 144 patients with SLE from the Rheumatology Department of Nanjing Drum Tower Hospital were included. Each patient underwent assessment with the SLEDAI and cardiovascular reflex tests (CARTs). Patients were classified into three groups: non-CAN, early-CAN and diagnosed-CAN based on the CARTs results. The relationship of CARTs and SLEDAI were analyzed using SPSS 26.0.

RESULTS

After being divided into three groups, there were significant differences in SLEDAI among them. With increasing SLEDAI score (P < 0.05), both CARTs scores and four individual parameters score increased significantly, both before and after adjusting for influencing factors (P < 0.05). Besides, in Logistic regression analysis, it identified that SLEDAI as an independent risk factor for CAN (OR = 1.227, 95%CI = 1.143-1.316, P < 0.001). Finally, after accounting for the influence of glucocorticoids, a significant positive correlation between CARTs and SLEDAI remained (P < 0.05).

CONCLUSIONS

As the gold standard in the diagnosing CAN, CARTs and four parameters are significantly correlated with SLEDAI. Furthermore, SLEDAI is also an independent risk factors for its development. In conclusion, this research demonstrated that SLEDAI is a dependable indicator for the onset and progression of CAN. Key Points • This study is the first to demonstrate a strong association between SLEDAI and cardiovascular autonomic neuropathy, identifying SLEDAI as a risk factor for CAN in SLE patients. • This study offers a convenient and rapid method for the clinical evaluation of CAN in SLE patients, providing significant value in assessing cardiovascular complications.

Clinical neurocardiology: defining the value of neuroscience-based cardiovascular therapeutics - 2024 update

The intricate role of the autonomic nervous system (ANS) in regulating cardiac physiology has long been recognized. Aberrant function of the ANS is central to the pathophysiology of cardiovascular diseases. It stands to reason, therefore, that neuroscience-based cardiovascular therapeutics hold great promise in the treatment of cardiovascular diseases in humans. A decade after the inaugural edition, this White Paper reviews the current state of understanding of human cardiac neuroanatomy, neurophysiology and pathophysiology in specific disease conditions, autonomic testing, risk stratification, and neuromodulatory strategies to mitigate the progression of cardiovascular diseases.

Assessing surgeon stress during urological interventions: A descriptive study using heart rate variability (uRRology)

INTRODUCTION

In a difficult environment like surgery with continuous exposure to stress, surgeon's health and well-being is affected. The heart rate variability (HRV) is a valid stress indicator. This study aims to provide descriptive data regarding stress during urological intervention using HRV.

METHODS

This prospective, unicentric study, included urological interventions from June to December 2023. Surgeons were surveyed on general characteristic, and surgical skills level. Beat-by-beat heart rate (HR) recorded using POLAR A300® chest belt. HRV were analyzed in time (mean HR and the root mean square of successive differences [RMSSD]) and frequency (Fast Fourier transformation spectrum high frequency [FFT spectrum HF]) domain. Their baseline collected outside the operating room, 3 events during intervention examined: incision, closure, and adverse events. Visual stress and difficulty scale during intervention were completed. The differences between baseline and events were calculated.

RESULTS

A total of 171 urological interventions were included. Senior surgeons performed 54 (31.58%) and juniors 117 (68.42%). During interventions, seniors had significantly higher median difference of HR (incision: -11.92 [12.74] bpm versus -2.27 [10.99] bpm for juniors, P≤0.0001; closure: -10.73 [13.71] bpm, versus -4.18 [12.30] bpm for juniors, P=0.0005), lower HF (incision: 0.01 [0.07] hz, versus -0.006 [0.03] hz for juniors P≤0.0001; closure: 0.02 [0.06] hz, versus 0.00 [0.02] hz for juniors, P≤0.0001), and lower RMSSD (incision: -3.34 [13.09] ms for seniors versus -7.63 [10.57] ms for juniors, P=0.0098). No significant difference in RMSSD during closure (P=0.2049).

CONCLUSION

Study demonstrated the possibility to assess HRV in standard medical practice, senior surgeons experienced more physiological changes during interventions.

LEVEL OF EVIDENCE: 4

Impact of the Menstrual Cycle on the Cardiovascular and Ventilatory Responses During Exercise in Normoxia and Hypoxia

Citherlet, Tom, Antoine Raberin, Giorgio Manferdelli, Nicolas Bourdillon, and Grégoire P Millet. Impact of the menstrual cycle on the cardiovascular and ventilatory responses during exercise in normoxia and hypoxia. High Alt Med Biol. 26:55-62, 2025. Introduction: Ovarian hormones influence several physiological functions in women. This study investigated how the hormonal variations across the menstrual cycle (MC) impact cardiovascular and ventilatory responses during rest and moderate exercise in normobaric hypoxia. Methods: Thirteen eumenorrheic women were tested during the early follicular (Fol1), late follicular (Fol2), and mid-luteal (Lut3) phases with measurement of hormonal levels. Heart rate (HR) variability, blood pressure, and baroreflex sensitivity (BRS) were evaluated at rest in normoxia. Ventilation (VE), peripheral oxygen saturation, and HR were monitored at rest and during moderate-intensity cycling exercise in hypoxia (FiO2 = 14%). Results: Despite expected hormone level variations, no significant changes were observed across the MC in HR variability (root mean square of successive differences; 64 (95% confidence interval [47, 81]) at Fol1, 54 [42, 66] at Fol2, 60 [44, 77] ms at Lut3), blood pressure (mean blood pressure; 85 [79, 90]), 87 [81, 93]), 84 [77, 92] mmHg), BRS (26 [17, 36], 28 [20, 35], 23 [17, 29] ms/mmHg), VE (rest: 8.9 [7.9, 9.8], 9.5 [9.0, 9.9], 9.0 [8.1, 9.9]; exercise: 53 [41, 66], 51.1 [36.4, 65.7], 54.4 [34.0, 74.8] l/min), peripheral oxygen saturation (rest: 89.8 [87.4, 92.1], 91.9 [88.7, 95.0], 90.2 [87.8, 92.6]; exercise: 80.5 [77.4, 83.5], 84.4 [80.4, 88.3], 81.9 [78.3, 85.4] %) HR (rest: 69.7 [60.2, 79.1], 70.8 [63.2, 78.3], 70.5 [64.0, 77.0]; exercise: 148 [136, 160], 146 [132, 161], 146 [132, 160] bpm), and cycling efficiency (0.17 [0.16, 0.18], 0.17 [0.13, 0.21], 0.16 [0.15, 0.18] %) (all p > 0.05). Discussion: From a practical point of view, there is no strong evidence of any usefulness of monitoring hormonal variations and the MC phases for women exercising in hypoxia.

Risk factors for fatigue severity in the post-COVID-19 condition: A prospective controlled cohort study of nonhospitalised adolescents and young adults

Long COVID is a global health concern, leading to persistent symptoms and disability long after the acute SARS-CoV-2 infection in most age groups. The condition can manifest even following mild COVID-19, and in young people, it may have serious adverse consequences for educational attainment and transition to adulthood. Fatigue is the most prevalent symptom, but the underlying mechanisms remain poorly understood. In this prospective study of 404 SARS-CoV-2-positive and 105 SARS-CoV-2 negative, non-hospitalised youth (ages 12-25, female 62%), we investigated which factors in the early convalescent stage (<28 days since test) were associated with the severity of persistent fatigue at 6 months after infection. Participants completed questionnaires regarding clinical symptoms, social factors and psychological traits, and were subject to clinical and functional testing and biomarker analyses. Variables with significant (p < 0.2) associations to the outcome in simple linear regression were chosen for multivariable modelling, together with potential confounders. In the final multivariable model, SARS-CoV-2-positivity was a minor risk factor for fatigue severity at six months. Baseline severity of symptoms was the main risk factor and correlated with psychosocial factors such as loneliness and neuroticism, rather than biomarkers. Our results suggest that factors not related to infection are major risk factors for persistent fatigue in this age group.

Individual Differences in Infants' Speech Segmentation Performance: The Role of Mother-Infant Cardiac Synchrony

Caregiver-infant coregulation is an early form of communication. This study investigated whether mother-infant biological coregulation is associated with 9-month-olds' word segmentation performance, a crucial milestone predicting language development. We hypothesized that coregulation would relate with infants' word segmentation performance. Additionally, we examined whether this relationship is influenced by the caregiving environment (i.e., parental reflective functioning) and the infant's emotional state (i.e., positive affect). Coregulation was investigated via cardiac synchrony in 28 nine-month-old infants (16 females) during a 5-min free-play with their German-speaking mothers. Cardiac synchrony was measured through Respiratory Sinus Arrhythmia (RSA), employing Recurrence Quantification Analysis to evaluate dyadic coupling (i.e., Recurrence Rate) and dyadic predictability (i.e., Entropy). Infants' word segmentation was measured with an eye-tracking central-fixation procedure. A stepwise regression revealed that higher dyadic coupling, but not predictability, of the dyads' RSA was associated with infants looking longer toward the screen when listening to novel as compared to familiar test words, indicating advanced word segmentation performance (Cohen's d = 0.25). Moreover, cardiac synchrony correlated positively with maternal sensitivity to their infant's mental states, but not with the infant's positive affect. These results suggest that caregiver-infant biological coregulation may play a foundational role in language acquisition.

Adverse childhood experiences and diurnal cortisol pattern and heart rate variability in adults

Dysregulation of hypothalamic-pituitary-adrenal axis (HPA axis) and of the autonomic nervous system may link stress throughout the life course with poorer health. This study aims to investigate whether multiple adverse childhood experiences have a long-term impact on markers of these systems - cortisol secretion and heart rate variability - in adulthood. Data were from the Whitehall II cohort study. Fourteen adversities, collected retrospectively in midlife, were considered. Outcomes were total amount of cortisol secretion during the day (area under the curve [AUC]), cortisol awakening response (CAR), and diurnal slope, estimated from six saliva samples taken on a weekday; and resting heart rate (rHR) and heart rate variability (HRV) measured for five minutes at three time points over 10 years with the last measures taken at the same time as the salivary measurement. Regression models were used to examine the association of adversities with AUC, CAR, rHR and HRV and multilevel modelling was applied to analyses of cortisol diurnal slope and the 10-year follow-up of rHR and HRV. At least one early life adversity was reported by 68 % of participants. There was little evidence that increasing number of adversities was associated with any measures of cortisol, rHR or HRV or 10-year change in rHR or HRV. Of the individual adversities, only parental death was associated with increased AUC and CAR. In conclusion, although the HPA axis and autonomic nervous system have been hypothesized as mechanisms relating to adverse childhood experiences with health, our study finds no evidence to support this.

Multimodal Assessment Battery and Heart Rate Variability Enhance Clinical Utility of Buffalo Concussion Treadmill Test

CONTEXT

The Buffalo Concussion Treadmill Test (BCTT) for exercise intolerance following concussion may highlight underlying autonomic dysfunction. Autonomic function at rest and with exertion may be predictive of neurocognitive performance for individuals with sports-related concussion. The purpose of this study is to explore the feasibility and utility of combining multimodal assessments with heart rate variability (HRV) measures during the BCTT for individuals with a remote history of concussion.

DESIGN

Prospective cohort study design, pretest/posttest.

METHODS

Participants included 5 males and 5 females (N = 10, age: 25.2 [3.3] y old, height: 173.2 [11.2] cm, mass: 73.4 [13.7] kg, body mass index: 24.5 [3.9], time since last concussion of 6.3 [4.5] y). All participants completed the multimodal assessment battery including: Concentration Reverse Digits (6 digits), Stroop Incongruent, and King-Devick Test under single- (seated) and dual-task conditions (walking on treadmill at 2.0 mph, 0% incline). Heart rate and HRV was collected at rest, during the BCTT, and during postexercise recovery. HRV data were processed and analyzed based on established protocols. Paired t tests were performed for pre- and postmeasurements separately for single- and dual-task tests of the multimodal assessment battery and HRV indices.

RESULTS

During the BCTT, HRV indices reflective of peripheral nervous system activity demonstrated a significant reduction with concomitant increase in HRV indices of sympathetic nervous system activity (P < .05). Recovery in these HRV indices toward baseline was observed during postexercise recovery. Neurocognitive performance on the Stroop task significantly improved with exercise (P < .05).

CONCLUSION

Implementation of multimodal assessments to evaluate physiological and neurocognitive responses to exercise in individuals with history of sports-related concussion is feasible. Addition of these objective measures may decrease reliance on self-reporting of exercise-induced symptom exacerbation, enabling clinicians to identify individuals whose neurocognitive performance or physiologic response to exercise on the BCTT deviates from the expected.

PR Interval as a Valuable Predictor of Tilt Table Test Results in Patients With Neurally Mediated Syncope

BACKGROUND

Neurally mediated syncope (NMS) is the primary cause of temporary and self-limiting loss of consciousness. The tilt table test (TTT) has been consistently employed as a supplementary diagnostic tool for syncope evaluation. However, TTT requires specialized equipment, which is lacking in several emergency room and clinic environments. We hypothesized that patients susceptible to NMS may have higher parasympathetic tone. Thus, this study investigates the correlation between PR interval and Herat rate variability parameters as indicators of parasympathetic tone and TTT results.

METHODS

We included 213 patients referred to our cardiology clinic with an impression of NMS in 2022 and 2023. Data was retrospectively collected from 24-h ambulatory electrocardiographic monitoring recordings, TTT results, and patients' history and physical examination records.

RESULTS

The analysis of the PR interval revealed a mean duration of 155 ms (95% CI: 148.61, 161.39) in negative TTT patients and 164.21 ms (95% CI: 158.44, 169.97) in positive TTT patients, indicating a statistically significant difference between two groups (p = 0.035). We also found that patients with a PR interval duration exceeding 160 ms demonstrated a significantly higher prevalence of positive TTT compared to those with a PR interval duration of less than 160 ms (p < 0.001, OR: 3.911, 95% CI: 2.143, 7.140).

CONCLUSIONS

Our study suggests a PR interval longer than 160 milliseconds as a valuable tool for predicting TTT results and identifying patients at higher risk of NMS.

The interplay of heart rate variability and ventricular repolarization parameters in the obese state: a review

The impact of obesity on heart rate variability (HRV) and ventricular repolarization, both vital indicators of cardiovascular health, is the focus of this review. Obesity, measured by BMI, waist circumference, and waist-to-hip ratio, significantly increases cardiovascular disease (CVD) risk due to structural and autonomic heart changes. Findings show that obese individuals exhibit prolonged QT and Tpeak-to-Tend (Tpe) intervals, suggesting delayed ventricular recovery and greater arrhythmia risk. Additionally, obesity-induced autonomic imbalance favors sympathetic activity over parasympathetic, reducing HRV and raising arrhythmogenic potential. Elevated QT and Tpe intervals reflect extended cardiac recovery phases, which contribute to poor cardiac outcomes. The Tpe interval could serve as an early marker of cardiac dysfunction in obese populations, highlighting the importance of early intervention to reduce CVD risk and enhance treatment strategies for obesity-related cardiovascular changes.

Examining the acute cardiovagal consequences of supine recovery during high-intensity interval exercise

PURPOSE

Exercise training requires the careful application of training dose to maximize adaptation while minimizing the risk of illness and injury. High-intensity interval training (HIIT) is a potent method for improving health and fitness but generates substantial autonomic imbalance. Assuming a supine posture between intervals is a novel strategy that could enhance physiological readiness and training adaptations. This study aimed to establish the safety and feasibility of supine recovery within a HIIT session and explore its acute effects.

METHODS

Fifteen healthy, active males (18-34 years) underwent assessment of cardiopulmonary fitness. Participants completed two identical HIIT treadmill sessions (4 x [3 min at 95% VO2max, 3 min recovery]) employing passive recovery in standing (STANDard) or supine (SUPER) posture between intervals. Heart rate variability (HRV), HRV recovery (HRVrec; lnRMSSD) and heart rate recovery at 1 min (HRrec) were assessed using submaximal constant speed running tests (CST) completed prior to, immediately after and 24 h following HIIT.

RESULTS

No severe adverse events occurred with SUPER, and compliance was similar between conditions (100 ± 0%). The change in HRVrec from the CST pre-to-post-HIIT was not different between conditions (p = 0.38); however, HRrec was faster following SUPER (39 ± 7 bpm) vs. STANDard (36 ± 5 bpm). HRV 24 h post-SUPER was also greater (3.56 ± 0.57 ms) compared to STANDard (3.37 ± 0.42 ms). Despite no differences in perceived exertion (p = 0.23) and blood lactate levels (p = 0.35) between SUPER and STANDard, average running HRs were lower (p = 0.04) with SUPER (174 ± 7 bpm) vs. STANDard (176 ± 7 bpm).

CONCLUSIONS

Supine recovery within HIIT attenuates acute cardioautonomic perturbation and accelerates post-exercise vagal reactivation. SUPER enhances recovery of vagal modulation, potentially improving physiological preparedness 24 h post-HIIT. Further research exploring the chronic effects of SUPER are now warranted.

Age-dependent influence of T wave amplitude on short period temporal dispersion in healthy subjects

BACKGROUND

T wave amplitude and repolarization variability in ECG showed inverse correlations. Sympathetic activation, induced by head-up tilt, is associated to a reduced T wave amplitude.

METHODS

Noninvasive hemodynamic and ECG data from three healthy subjects' groups (Group 1: 10-19 years-old; Group 2: 40-49 years-old; Group 3: 80-89 years-old) were analyzed. Measurements were taken during controlled-breathing rest, and during head-up tilt. The mean and standard deviation (SD) were calculated for these ECG intervals: QT, STp (from S to Tpeak) and Te (from Tpeak to Tend).

RESULTS

During tilt, a significant decrease in T wave amplitude was observed in the younger groups (p < 0.001), but not in Group 3. At rest, Group 1 exhibited higher voltage compared to Group 2 (p < 0.05) and 3 (p < 0.001), as Group 2 compared to Group 3 (p < 0.05). A negative correlation was confirmed between T wave amplitude and QTSD, STpSD and TeSD (p < 0.001). Low-frequency normalized units (p < 0.05) and high-frequency normalized units (p < 0.001) were inversely related to T-wave amplitude.

CONCLUSION

The findings suggest an age-dependent decline in T wave amplitude during tilt and elucidates the relationship between systolic function and T wave amplitude among healthy subjects. These insights warrant further investigations in clinical and research settings for cardiovascular diseases.

Vagal heart rate variability during rapid eye movement sleep reduces negative memory bias

Emotional memories change over time, but the mechanisms supporting this change are not well understood. Sleep has been identified as one mechanism that supports memory consolidation, with sleep selectively benefitting negative emotional consolidation at the expense of neutral memories, with specific oscillatory events linked to this process. In contrast, the consolidation of neutral and positive memories, compared to negative memories, has been associated with increased vagally mediated heart rate variability (HRV) during wakefulness. However, how HRV during sleep contributes to emotional memory consolidation remains unexplored. We investigated how sleep oscillations (i.e., sleep spindles) and vagal activity during sleep contribute to the consolidation of neutral and negative memories. Using a double-blind, placebo-controlled, within-subject, cross-over design, we examined the impact of pharmacological vagal suppression using zolpidem on overnight emotional memory consolidation. Thirty-three participants encoded neutral and negative pictures in the morning, followed by picture recognition tests before and after a night of sleep. Zolpidem or placebo was administered in the evening before overnight sleep, and participants were monitored with electroencephalography and electrocardiography. In the placebo condition, greater overnight improvement for neutral pictures was associated with higher vagal HRV in both Non-Rapid Eye Movement Slow Wave Sleep (NREM SWS) and REM. Additionally, the emotional memory tradeoff (i.e., difference between consolidation of neutral versus negative memories) was associated with higher vagal HRV during REM, but in this case, neutral memories were remembered better than negative memories, indicating a potential role for REM vagal HRV in promoting a positive memory bias overnight. Zolpidem, on the other hand, reduced vagal HRV during SWS, increased NREM spindle activity, and eliminated the positive memory bias. Lastly, we used stepwise linear mixed effects regression to determine how NREM spindle activity and vagal HRV during REM independently explained the variance in the emotional memory tradeoff effect. We found that the addition of vagal HRV in combination with spindle activity significantly improved the model's fit. Overall, our results suggest that sleep brain oscillations and vagal signals synergistically interact in the overnight consolidation of emotional memories, with REM vagal HRV critically contributing to the positive memory bias.

A method for dyadic cardiac rhythmicity analysis: Preliminary evidence on bilateral interactions in fetal-maternal cardiac dynamics

Cardiac activity responds dynamically to metabolic demands and neural regulation. However, little is known about this process during pregnancy. Reports show occasional fetal-maternal heart rate couplings, but it has remained unclear whether these couplings extend to more complex oscillatory patterns of the heart rhythm. We developed a framework of time-varying measures of heart rate and rhythm, to test the presence of co-varying patterns in concurrent maternal and fetal measures (late pregnancy dataset, n = 10, and labour dataset, n = 12). These measures were derived from first and second-order Poincaré plots, with the aim to describe changes in short- and long-term rhythmicity, but also the dynamic shifts in acceleration and deceleration of heart rate. We found episodes of maternal-fetal co-varying patterns of cardiac rhythm in all the measures explored, in both datasets (at least 90% of the dataset presented a significant maternal-fetal correlation in each measure, with P < 0.001), with dynamic delays suggesting bilateral interactions at different time scales. We also found that these couplings intensify during labour (test between late pregnancy vs. labour datasets, P < 0.0015 in all second-order Poincaré plot-derived measures). While most literature suggests that the fetal heart responds to maternal breathing patterns or contractions, we propose the possibility that the fetal heart may also have a signalling function in the context of co-regulatory mechanisms and maternal inter-organ interactions. Understanding these complex visceral oscillations in utero may enhance the assessment of a healthy fetal development.

Autonomic Disequilibrium at Rest in Autistic Children and Adults

Autism Spectrum Disorder (ASD) symptoms have been proposed to be linked to Autonomic Nervous System (ANS) atypical functioning, in particular sympathetic hyper-arousal and parasympathetic under-activation. The objective of this study was to characterize autonomic functioning at rest in autistic and neurotypical children and adults. To characterize several aspects of autonomic functioning, we recorded simultaneously pupil diameter, heart rate and electrodermal activity during 5 min of rest in 44 children (6-12 years old, 22 autistic) and 42 adults (19-52 years old, 21 autistic). Several parameters allowed to characterize tonic and phasic indices of sympathetic and parasympathetic systems at rest. Autistic children exhibited the expected pattern of parasympathetic under-activation at rest compared to their typically developing (TD) peers, and with a tendency for a higher phasic sympathetic activity. Adults exhibited a reverse autonomic pattern, with autistic individuals showing higher sympathetic tonus and lower sympathetic phasic activity than their TD peers. In conclusion, we observed an autonomic disequilibrium at rest both in autistic children and adults, but with opposite patterns that could reflect adaptive compensation mechanisms during maturation. This disequilibrium in autistic children would switch from excessive phasic components to excessive tonic components in adults, possibly subtended by an atypical locus coeruleus functioning.

Feasibility and acceptance of transdermal auricular vagus nerve stimulation using a TENS device in females suffering from long COVID fatigue

BACKGROUND

The COVID-19 pandemic has led to significant health challenges, with some individuals developing long COVID characterized by persistent symptoms such as fatigue, dyspnea and cognitive difficulties lasting weeks or months after infection. This condition predominantly affects women and may involve prolonged inflammation and autonomic nervous system dysfunction. Current treatments focus on symptom relief and vagus nerve stimulation (VNS) is being investigated for its potential therapeutic benefits.

METHODS

This pilot study was a prospective, blinded, randomized controlled trial involving 36 female long COVID patients aged 18-70 years. Participants were assigned to three groups receiving VNS at frequencies of 10 Hz, 25 Hz, or a control of 2 Hz for 3 months. Outcomes were assessed at baseline, after 4 and 12 weeks.

RESULTS

The study revealed that all VNS treatment groups experienced reduction in symptoms associated with long COVID, particularly in fatigue and dyspnea, after 12 weeks. Participants across all frequencies reported an improvement in health-related quality of life. Heart rate variability remained stable throughout the trial, and no significant changes in morning salivary cortisol levels were seen across groups.

DISCUSSION

Vagus nerve stimulation may offer therapeutic benefits for women with long COVID, particularly in reducing fatigue and dyspnea. The treatment was found to be safe, with no significant side effects reported; however, further research with larger study groups is needed to confirm these findings and examine the long-term effects of VNS on autonomic nervous system function.

Non-invasive vagus nerve stimulation and exercise capacity in healthy volunteers: a randomized trial

BACKGROUND AND AIMS

Vagal parasympathetic dysfunction is strongly associated with impaired exercise tolerance, indicating that coordinated autonomic control is essential for optimizing exercise performance. This study tested the hypothesis that autonomic neuromodulation by non-invasive transcutaneous vagus nerve stimulation (tVNS) can improve exercise capacity in humans.

METHODS

This single-centre, randomized, double-blind, sham-controlled, crossover trial in 28 healthy volunteers evaluated the effect of bilateral transcutaneous stimulation of vagal auricular innervation, applied for 30 min daily for 7 days, on measures of cardiorespiratory fitness (peak oxygen consumption (VO2peak)) during progressive exercise to exhaustion. Secondary endpoints included peak work rate, cardiorespiratory measures, and the whole blood inflammatory response to lipopolysaccharide ex vivo.

RESULTS

tVNS applied for 30 min daily over 7 consecutive days increased VO2peak by 1.04 mL/kg/min (95% CI: .34-1.73; P = .005), compared with no change after sham stimulation (-0.54 mL/kg/min; 95% CI: -1.52 to .45). No carry-over effect was observed following the 2-week washout period. tVNS increased work rate (by 6 W; 95% CI: 2-10; P = .006), heart rate (by 4 bpm; 95% CI: 1-7; P = .011), and respiratory rate (by 4 breaths/min; 95% CI: 2-6; P < .001) at peak exercise. Analysis of the whole blood transcriptomic response to lipopolysaccharide in serial samples obtained from five participants showed that tVNS reduced the inflammatory response.

CONCLUSIONS

Non-invasive vagal stimulation improves measures of cardiorespiratory fitness and attenuates inflammation, offering an inexpensive, safe, and scalable approach to improve exercise capacity.

Extending Anxiety Detection from Multimodal Wearables in Controlled Conditions to Real-World Environments

This study quantitatively evaluated whether and how machine learning (ML) models built by data from controlled conditions can fit real-world conditions. This study focused on feature-based models using wearable technology from real-world data collected from young adults, so as to provide insights into the models' robustness and the specific challenges posed by diverse environmental noise. Feature-based models, particularly XGBoost and Decision Trees, demonstrated considerable resilience, maintaining higher accuracy and reliability across different noise levels. This investigation included an in-depth analysis of transfer learning, highlighting its potential and limitations in adapting models developed from standard datasets, like WESAD, to complex real-world scenarios. Moreover, this study analyzed the distributed feature importance across various physiological signals, such as electrodermal activity (EDA) and electrocardiography (ECG), considering their vulnerability to environmental factors. It was found that integrating multiple physiological data types could significantly enhance model robustness. The results underscored the need for a nuanced understanding of signal contributions to model efficacy, suggesting that feature-based models showed much promise in practical applications.

Stress management with HRV following AI, semantic ontology, genetic algorithm and tree explainer

Heart Rate Variability (HRV) serves as a vital marker of stress levels, with lower HRV indicating higher stress. It measures the variation in the time between heartbeats and offers insights into health. Artificial intelligence (AI) research aims to use HRV data for accurate stress level classification, aiding early detection and well-being approaches. This study's objective is to create a semantic model of HRV features in a knowledge graph and develop an accurate, reliable, explainable, and ethical AI model for predictive HRV analysis. The SWELL-KW dataset, containing labeled HRV data for stress conditions, is examined. Various techniques like feature selection and dimensionality reduction are explored to improve classification accuracy while minimizing bias. Different machine learning (ML) algorithms, including traditional and ensemble methods, are employed for analyzing both imbalanced and balanced HRV datasets. To address imbalances, various data formats and oversampling techniques such as SMOTE and ADASYN are experimented with. Additionally, a Tree-Explainer, specifically SHAP, is used to interpret and explain the models' classifications. The combination of genetic algorithm-based feature selection and classification using a Random Forest Classifier yields effective results for both imbalanced and balanced datasets, especially in analyzing non-linear HRV features. These optimized features play a crucial role in developing a stress management system within a Semantic framework. Introducing domain ontology enhances data representation and knowledge acquisition. The consistency and reliability of the Ontology model are assessed using Hermit reasoners, with reasoning time as a performance measure. HRV serves as a significant indicator of stress, offering insights into its correlation with mental well-being. While HRV is non-invasive, its interpretation must integrate other stress assessments for a holistic understanding of an individual's stress response. Monitoring HRV can help evaluate stress management strategies and interventions, aiding individuals in maintaining well-being.

Facial expressions during compound interventions of nociception, conspecific isolation, and sedation in horses

Facial expressions in prey animals such as equines can convey information regarding their internal state and are therefore often used as cues for welfare and pain evaluation. The state of pain is commonly compared to a neutral state with little consideration given to other experiences that could affect the animal, although this situation is rare outside of experimental contexts. To evaluate the effect of managerial contexts on facial expressions from a nociceptive input, conspecific isolation and sedation with known physiological effects were compared to compound states of nociception. Using an anatomically based facial action coding system and a short acting pain model, patterns of facial activity could discriminate between horses experiencing conspecific isolation, sedation, and a nociceptive stimulus separately. Nociception occurring together with conspecific isolation could not be discriminated from the conspecific isolation alone, and compound nociception and sedation could not be discriminated from control. While blinking frequency demonstrated potential to be a valuable marker when evaluating a nociceptive stimulus in sedated horses, careful consideration must be given to the biological interpretation of facial expressions during situations where managerial or drug effects may be present.

The effect of self-compassion versus mindfulness interventions on autonomic responses to stress in generalized anxiety disorders

Objective

Although research on psychological interventions in generalized anxiety disorder (GAD) has provided evidence of their effectiveness regarding self-reported outcomes, few studies have examined their psychophysiological effects. Heart rate is emerging as a potential biomarker of efficacy in anxiety disorders. This study aimed to investigate the effects of a self-compassion intervention versus a mindfulness intervention on physiological arousal in response to induced stress.

Methods

Forty-seven patients with GAD had heart rate data collected during a stress task before and after a 2-week pharmacological treatment (known as treatment as usual, TAU), a self-compassion intervention + TAU or a mindfulness intervention + TAU. They also reported state anxiety, positive affect, and negative affect at pre- and post- intervention before the stress task. ANOVAs were conducted to analyze the effects on electrocardiogram data self-reported measurements.

Results

Self-compassion intervention uniquely decreased heart rate response to a stressor whereas mindfulness intervention did not. Both treatments decreased state anxiety and negative affect to a stressor, while increased positive affect in this context. We also demonstrated a significant correlation between decreased heart rate response and less negative emotions.

Conclusion

The Findings provides novel physiological evidence that self-compassion interventions buffer stress reactivity in individuals with GAD. Attention shall be paid to the limitations in small and unequal sample size and a non-randomized study design.

The autonomous nervous system and the cholinergic anti-inflammatory reflex in postoperative neurocognitive disorders

PURPOSE OF REVIEW

Postoperative delirium (POD) is a common and serious complication after surgery. It is associated with postoperative neurocognitive disorder (PNCD). The vagal cholinergic anti-inflammatory pathway (CAP) has been hypothesized to play a role in POD/PNCD and may be a target for interventions such as transcutaneous auricular stimulation (taVNS). We aim to review associations of heart rate variability (HRV) as an indicator of vagal function with POD and postoperative immune reaction as well as taVNS as a potential preventive intervention for POD.

RECENT FINDINGS

Autonomous nervous system (ANS) dysfunction was a common finding in studies analysing HRV in POD and postoperative cognitive dysfunction, but results were heterogeneous. There was no evidence from HRV analysis that vagal activity prevents overshooting postoperative immune activation, but HRV may help to identify patients at risk for postoperative infections. Animal studies and preliminary trials suggest that taVNS may be used to prevent POD/PNCD.

SUMMARY

Our review provides no evidence that CAP suppression is associated with POD/PNCD. Future studies should consider that high vagal tone may also mediate immunosuppression in surgical patients, yielding an increased risk for postoperative infections. Although taVNS is a promising approach to prevent POD/POCD, future studies should take these concerns into account.

Autonomic cardiovascular control is unaffected in children referred for assessment of excessive daytime sleepiness

There is conflicting evidence for impaired autonomic control of heart rate (HR) in adults with narcolepsy and idiopathic hypersomnolence (IH). Despite these chronic hypersomnia conditions primarily being diagnosed around the age of puberty, there are limited studies in children. The present study investigated cardiovascular control using heart rate variability (HRV) and the extent of nocturnal HR dipping during sleep in children and adolescents with narcolepsy and IH. Children having an overnight polysomnographic study followed by a multiple sleep latency test (MSLT) for investigation of excessive daytime sleepiness (EDS) between May 2010 to December 2023 were included: 28 children diagnosed with narcolepsy, 11 with IH, and 26 subjectively sleepy children who did not meet the diagnostic criteria for either narcolepsy or IH. Each clinically referred child was matched for age and sex with a control. Time domain and frequency domain HRV were calculated from ECG recorded at 512 Hz. There were no differences in either time domain or spectral analysis of HRV between clinical groups or between clinical groups and their control group. The expected sleep state differences in HRV were observed in all groups. There was also no difference in HR nocturnal dipping between groups. Despite evidence for abnormal autonomic function in adults with narcolepsy and IH, our study did not identify any abnormalities in HR, HR control, or nocturnal dipping of HR in children referred for assessment of EDS. This suggests that autonomic dysfunction may be a feature of these conditions that develops in later life.

Taste the emotions: pilot for a novel, sensors-based approach to emotional analysis during coffee tasting

BACKGROUND

Coffee is a natural drink with important properties for the human body and mind, capable of delivering energy and strong emotions, thus being appreciated since ancient times. The qualitative and quantitative assessment of the coffee properties is normally performed by trained panelists, though relying on standardized questionnaires, with possible biases arising. In this study, for the first time in the scientific literature, we applied a technology-based approach, based on the use of wearable sensors, to study the implicit emotional responses of a small cohort of experienced coffee judges, thus taking this chance to assess the feasibility of this approach in such a scenario. The merging of different technologies for capturing biomedical signals, including electrocardiogram, galvanic skin response, and electroencephalogram, was therefore adopted to retrieve results in terms of the relationships between implicit (i.e. psychophysiological) and explicit (i.e. derived from questionnaires) measurements.

RESULTS

Significant correlations were obtained between biomedical signals and data from the questionnaires within all the sensory domains (olfaction, vision, taste) investigated, particularly concerning autonomic-related features.

CONCLUSIONS

The results obtained confirmed the viability of this new approach in the psychophysical and emotional assessment in coffee tasting judges, paving the way for a new perspective into the universe of coffee quality assessment panels, eventually transferable to broader scale investigations, somewhat dealing with consumer satisfaction and neuromarketing at large. © 2023 Society of Chemical Industry.

Clinical Features and Physiological Signals Fusion Network for Mechanical Circulatory Support Need Prediction in Pediatric Cardiac Intensive Care Unit

We link the hemodynamic response to inotropic agents with outcomes related to Mechanical Circulatory Support (MCS) by analyzing physiological time series and clinical features using a Machine Learning/Deep Learning ensemble approach for multi-modal waveforms in the pediatric cardiac intensive care setting of a quaternary-care hospital. Unlike existing studies that typically process a single feature type or focus on short-term diagnoses from physiological signals, our novel system processes minute-by-minute multi-sensor data to identify the need for MCS in patients admitted with acute decompensated heart failure. The data used includes tabular clinical features, time series from hemodynamic monitors, and raw waveforms from electrocardiogram and arterial blood pressure signals. Our predictions support an early identification of high-risk patients after just two days of Intensive Care Unit (ICU) admission, with classification and feature importance results confirming the predictive ability of the early hemodynamic response to inotropic agent administration, achieving an AUC of 0.88 in the prediction classification task. This is particularly significant in cases where clinical decisions are not straightforward, such as those in the cohort for this study.

Comprehensive linear and nonlinear heart rate variability normative data in children

BACKGROUND

The autonomic nervous system (ANS) is critical in regulating involuntary bodily functions, including heart rate. Heart rate variability (HRV) reflects the complex interplay between the ANS and humoral factors, making it a valuable noninvasive tool for assessing autonomic function. While HRV has been extensively studied in adults, normative data for HRV in children, primarily based on long-term rhythm recordings, are limited.

OBJECTIVE

This study aimed to establish comprehensive normative data for HRV in children.

METHODS

In this retrospective study, we examined 24-h Holter monitors of children aged 1 day to 18 years, divided into six age groups, at Nemours Children's Health in Orlando, Florida, spanning the years 2013-2023. HRV analysis encompassed time-domain, frequency-domain, and nonlinear indices.

RESULTS

Holter data for a total of 247 patients in six age groups were included. An age-related uptrend was observed in all time- and frequency-domain variables except the normalized unit of low-frequency power. Entropy analysis revealed contradictory results among different entropy techniques. Sample and approximate entropy analyses were consistent and showed less complexity and more predictability of HRV with decreasing heart rate, while Shannon entropy analysis showed the opposite. Fractal detrended fluctuation analysis exhibited significant decreases across the age groups, suggestive of diminishing self-similarity of HRV patterns.

CONCLUSION

Control of heart rate and HRV is a highly complex process and requires further study for a better understanding. It seems that no single parameter can fully elucidate the entire process. A combination of time-domain, frequency-domain, and nonlinear indices may be necessary to explain HRV behavior in the growing body.

Substance Use is Associated With College Students' Acute Parasympathetic Nervous System Responses to Challenge

College students use substances for varied reasons, including to cope with stress. The parasympathetic nervous system (PNS) regulates bodily functions to promote energy conservation (the 'rest and digest' response), and individuals differ in their physiological sensitivity to challenge. It remains unclear whether greater PNS responses (i.e., declines in PNS activity, termed vagal withdrawal) to challenge could suggest difficulty regulating and thereby confer risk for using substances in community samples. We hypothesised that lower resting PNS activity and greater PNS responses to a challenge task would be associated with more frequent substance use (i.e., alcohol use, binge drinking, cannabis use). College students (N = 152; Mage = 20.5, SD = 3.2; 73.8% female) reported their past month frequency of substance use and completed a laboratory-based challenge task while having an electrocardiogram administered to derive respiratory sinus arrhythmia (RSA), a measure of PNS activity. They watched a 4-min neutral video (resting baseline) and then traced a star with their nondominant hand while only seeing the mirror reflection of their hand (challenge). Higher resting RSA was related to more frequent cannabis use. Individuals with larger declines in RSA from the video to the task (i.e., greater PNS responses) tended to use each substance more frequently. RSA recovery from the task was not related to substance use. Taken together, college students who are more physiologically responsive to challenge may use substances more frequently, potentially as a means of coping. Biofeedback interventions can be investigated for reducing college students' substance use risk.

Assessing operator stress in collaborative robotics: A multimodal approach

In the era of Industry 4.0, the study of Human-Robot Collaboration (HRC) in advancing modern manufacturing and automation is paramount. An operator approaching a collaborative robot (cobot) may have feelings of distrust, and experience discomfort and stress, especially during the early stages of training. Human factors cannot be neglected: for efficient implementation, the complex psycho-physiological state and responses of the operator must be taken into consideration. In this study, volunteers were asked to carry out a set of cobot programming tasks, while several physiological signals, such as electroencephalogram (EEG), electrocardiogram (ECG), Galvanic skin response (GSR), and facial expressions were recorded. In addition, a subjective questionnaire (NASA-TLX) was administered at the end, to assess if the derived physiological parameters are related to the subjective perception of stress. Parameters exhibiting a higher degree of alignment with subjective perception are mean Theta (76.67%), Alpha (70.53%) and Beta (67.65%) power extracted from EEG, recovery time (72.86%) and rise time (71.43%) extracted from GSR and heart rate variability (HRV) metrics PNN25 (71.58%), SDNN (70.53%), PNN50 (68.95%) and RMSSD (66.84%). Parameters extracted from raw RR Intervals appear to be more variable and less accurate (42.11%) so as recorded emotions (51.43%).

Heart rate variability during pregnancy moderates the impact of depressive symptoms on fetal growth

Depression occurs in up to 13 % of all pregnancies and is associated with adverse pregnancy outcomes. However, the literature regarding associations between depression and lower birth weight or fetal growth has been inconsistent. Here, we consider if high frequency heart rate variability (HF-HRV) may moderate the association between depression and birth weight. Lower HF-HRV has been associated with greater risk of depression and poorer health outcomes. However, during pregnancy, there is a normative decrease in HF-HRV that may be protective. Higher HF-HRV is associated with a person's ability to flexibly adapt to challenges. During pregnancy, less flexibility may reduce responses to challenges, including depression, thereby mitigating the vulnerability of the pregnancy to the effects of depression. The present study considers this possibility with 80 pregnant women who completed a measure of depressive symptoms during pregnancy at 24 to 28, 30 to 32, and 36 to 38 weeks gestation, and had HF-HRV measured at 24 to 28 weeks gestation. Fetal growth was derived using birth weight and length of gestation data gathered from medical charts. Results revealed that for women with higher HF-HRV, depressive symptoms were negatively associated with fetal growth. This relationship was not evident for women with lower HF-HRV, who appeared to be protected from the effects of depression on fetal growth. Considering the combined impact of HF-HRV and depression during pregnancy may help us better identify women at risk of having lower birth weight neonates, and improve our understanding of how depression is associated with adverse pregnancy outcomes.

Women With Polycystic Ovary Syndrome and Excess Body Fat Exhibit Atypical Sympathetic Autonomic Modulation That is Partially Reversed by Aerobic Physical Training

OBJECTIVE

The aetiology of impairments in autonomic modulation of heart rate variability (HRV) in polycystic ovary syndrome (PCOS) remains unclear, as does the impact of aerobic physical training (APT) on controlling endocrine-metabolic disorders and HRV. This is because these women often present excess body fat. Therefore, we assessed whether the dysregulation in autonomic modulation of HRV in women with PCOS is due to endocrine-metabolic disorders and whether the combination of excess body fat with endocrine-metabolic disorders amplifies cardiovascular autonomic deficits. We also investigated whether APT positively influences autonomic modulation of HRV in PCOS.

DESIGN

Non-randomised clinical trial.

PARTICIPANTS

Women with and without PCOS with different percentages of body fat.

MEASUREMENTS

Participants were divided into four groups: women without PCOS with a body fat percentage between 22% and 29% (CONTROL group; 22%-29%); CONTROL (30%-37%) group; PCOS (22%-29%) group; and PCOS (30%-37%) group. Hemodynamic, metabolic, and hormonal characteristics and HRV parameters were obtained before and after 16 weeks of APT.

RESULTS

The PCOS (22%-29%) group exhibited lower vagal modulation than the CONTROL (22%-29%) group. In contrast, no significant differences were observed between the CONTROL (30%-37%) and PCOS (30%-37%) groups. Furthermore, the PCOS (30%-37%) group demonstrated lower sympathetic modulation than the PCOS (22%-29%) group. After APT, the PCOS (22%-29%) group increased in vagal modulation, while the PCOS (30%-37%) group increased in sympathetic modulation.

CONCLUSION

PCOS affects vagal modulation; however, this effect may be masked at elevated levels of body fat. Additionally, the combination of excess body fat with endocrine-metabolic dysregulation appears to reduce sympathetic modulation, possibly due to sympathetic drive hyperactivity. APT positively affected HRV in both PCOS groups.

Ultra-short-term stress measurement using RGB camera-based remote photoplethysmography with reduced effects of Individual differences in heart rate

Stress is linked to health problems, increasing the need for immediate monitoring. Traditional methods like electrocardiograms or contact photoplethysmography require device attachment, causing discomfort, and ultra-short-term stress measurement research remains inadequate. This paper proposes a method for ultra-short-term stress monitoring using remote photoplethysmography (rPPG). Previous predictions of ultra-short-term stress have typically used pulse rate variability (PRV) features derived from time-segmented heart rate data. However, PRV varies at the same stress levels depending on heart rates, necessitating a new method to account for these differences. This study addressed this by segmenting rPPG data based on normal-to-normal intervals (NNIs), converted from peak-to-peak intervals, to predict ultra-short-term stress indices. We used NNI counts corresponding to average durations of 10, 20, and 30 s (13, 26, and 39 NNIs) to extract PRV features, predicting the Baevsky stress index through regressors. The Extra Trees Regressor achieved R2 scores of 0.6699 for 13 NNIs, 0.8751 for 26 NNIs, and 0.9358 for 39 NNIs, surpassing the time-segmented approach, which yielded 0.4162, 0.6528, and 0.7943 for 10, 20, and 30-s intervals, respectively. These findings demonstrate that using NNI counts for ultra-short-term stress prediction improves accuracy by accounting for individual bio-signal variations.

Quality in Question: Assessing the Accuracy of Four Heart Rate Wearables and the Implications for Psychophysiological Research

Heart rate (HR) and heart rate variability (HRV) are two key measures with significant relevance in psychophysiological studies, and their measurement has become more convenient due to advances in wearable technology. However, photoplethysmography (PPG)-based wearables pose critical validity concerns. In this study, we validated four PPG wearables: three consumer-grade devices (Kyto2935, Schone Rhythm 24, and HeartMath Inner Balance Bluetooth) and one research-grade device (Empatica EmbracePlus, successor to the widely-used but discontinued Empatica E4). All devices were worn simultaneously by 40 healthy participants who underwent conditions commonly used in laboratory research (seated rest, arithmetic task, recovery, slow-paced breathing, a neuropsychological task, posture manipulation by standing up) and encountered in ambulatory-like settings (slow walking and stationary biking), compared against a criterion electrocardiography device, the Vrije Universiteit Ambulatory Monitoring System (VU-AMS). We determined the signal quality, the linear strength through regression analysis, the bias through Bland-Altman analysis, and the measurement error through mean arctangent absolute percentage error for each condition against the criterion device. We found that the research-grade device did not outperform the consumer-grade devices in laboratory conditions. It also showed low agreement with the ECG in ambulatory-like conditions. In general, devices captured HR more accurately than HRV. Finally, conditions that deviated from baseline settings and involved slight to high movement, negatively impacted the agreement between PPG devices and the criterion. We conclude that PPG devices, even those advertised and designed for research purposes, may pose validity concerns for HRV measurement in conditions other than those similar to resting states.

Transcutaneous auricular vagus nerve stimulation inhibits mental stress-induced cortisol release-Potential implications for inflammatory conditions

Elevated glucocorticoid levels with reduced glucocorticoid responsiveness have been reported in chronic inflammatory conditions. Activation of neurons in the nucleus of the solitary tract by transcutaneous auricular vagus nerve stimulation (taVNS) may activate inhibitory pathways projecting to the hypothalamic paraventricular nucleus (PVN), thus inhibiting corticotropin-releasing hormone (CRH) release and improving glucocorticoid dysfunction in chronic inflammatory conditions. Healthy adults (n = 12) participated in experimental (taVNS) and control (sham-taVNS) sessions at least 4 days apart. A 30-min baseline recording was followed by 30 min of taVNS or sham-taVNS and 40 min of recovery. Ten minutes into taVNS or sham-taVNS, a mental arithmetic stress test (MAST) was conducted for 15 min. The MAST increased heart rate, low frequency (LF) heart rate variability (HRV), and the LF to high frequency ratio of HRV, confirming sympathetic activation. Salivary cortisol levels during the MAST were lower during taVNS (49.5 ± 48.0% from baseline; mean ± SD) compared to sham-taVNS (106.0 ± 81.1% from baseline; mean ± SD; p < 0.05). In a psoriasis patient, daily taVNS for 3 months reduced diurnal salivary cortisol levels from 58.2 ± 35.2 (ng/mL)*h (mean ± SD) to 34.9 ± 13.8 (ng/mL)*h (mean ± SD). While it is possible that taVNS inhibited CRH-releasing neurons in the PVN, our study design did not allow to confirm this potential mechanism.

Influence of biopsychosocial factors on a functionally delayed ageing process

PURPOSE

Increasing life expectancy and rising populations create new challenges for science, economy, politics, society and each individual. The bio-functional status (BFS) as a theoretical model incorporates the International Classification of Functioning (ICF) and the concept of active and healthy ageing (AHA). This study addresses the question of which the strengths and resources have the greatest positive impact on bio-functional age (BFA) and might be influencable.

METHODS

A monocenter, cross-sectional, observational, non-interventional trial was performed from 2012 to 2014 at Inselspital Bern to evaluate the BFS, a complex, generic, non-invasive, sex- and age-validated assessment tool. A standardized battery of assessments was performed on 464 females and 166 males, aged 18 to 65 years (n = 630). We aimed to statistically identify BFS items that might be influenceable to support healthy ageing and vitality.

RESULTS

341 participants of the original cohort were included. After carrying out regression analysis, 10 parameters (T = 8.992; p < 0.001) remained as possible variables that can be influenced (R2 = 0.758). Of those identified parameters, one can be assigned to subcategory I of BFS (pulse performance index), two to II (tapping frequency part I and II), two to III (strategy building and verbal reaction time) and three to IV [sense of coherence, social potency, complaint questionnaire (BFB total)]. Age and sex, nevertheless, have an influence on the BFA and the BFA-Index.

CONCLUSION

The most promising approach to support vitality, is to support low social stress, high social integration, a good sense of coherence and maintaining a good mental and cognitive status.

New evidence for baroreflex and respiratory chemoreflex-mediated cerebral sympathetic activation in humans

The brain is highly innervated by sympathetic nerve fibers; however, their physiological purpose is poorly understood. We hypothesized that unilateral cerebral norepinephrine (NE) spillover, an index of cerebral sympathetic nerve activity (SNA), would be elevated when engaging the baroreflex [via lower-body negative pressure (LBNP; -20 and -40 Torr)] and respiratory chemoreflexes [via carbon dioxide (CO2) administration (+8 Torr)], independently and in combination. Twelve young and healthy participants (five females) underwent simultaneous blood sampling from the right radial artery and internal jugular vein. Tritiated NE was infused through the participants' right forearm vein. Right internal jugular vein and internal carotid artery blood flow were measured using duplex ultrasound. Unilateral cerebral NE spillover remained unchanged when only LBNP was applied (P = 0.29) but increased with hypercapnia (P = 0.035) and -40 Torr LBNP + CO2 (P < 0.01). There were no changes in total NE spillover during the LBNP and LBNP + CO2 trials (both P = 0.66), nor during CO2 alone (P = 0.13). No correlations were present between the increase in unilateral cerebral NE spillover during -40 Torr LBNP + CO2 and reductions in internal carotid artery blood flow (P = 0.56). These results indicate that baroreflex and respiratory chemoreflex stressors elevate cerebral SNA; however, the observed cerebral sympathetic activation has no impact on blood flow regulation in the internal carotid artery.NEW & NOTEWORTHY The results of the current study suggest that baroreflex and respiratory chemoreflex stressors elevate cerebral sympathetic nervous activity, quantified using the brain norepinephrine spillover method. However, the observed cerebral sympathetic activation has no impact on blood flow regulation in the internal carotid artery.

Heart Rate Variability as a Digital Biomarker in Adolescents and Young Adults Receiving Hematopoietic Cell Transplantation

INTRODUCTION

Adolescents and young adults (AYAs) receiving hematopoietic cell transplantation (HCT) are at high risk for poor psychosocial outcomes. Heart rate variability (HRV), a surrogate for autonomic nervous system activity, is a promising digital biomarker that has been linked to important outcomes. The objectives of this study were to prospectively describe the trajectory of HRV among AYAs receiving HCT and explore the association between HRV and patient-reported outcomes (PROs).

METHODS

This was a multi-site study embedded in a randomized trial among AYAs receiving HCT (NCT03640325). We collected sequential 24-h HRV metrics, including the standard deviation of normal-to-normal beats (SDNN), root-mean-square of successive differences (RMSSD), as well as frequency domain measures. PRO surveys queried anxiety, depression, quality of life, hope, and resilience at baseline and 3 months. We summarized outcomes using descriptive statistics, and Pearson correlation coefficients were used to examine the relationship between HRV and PROs.

RESULTS

Thirty-nine HRV recordings were collected from n = 16 participants aged 12-21 years. There was a moderately strong correlation between inferior baseline HRV and higher anxiety and depression (anxiety: r = -0.35 (p = 0.18) for SDNN, r = -0.47 (p = 0.07) for RMSSD; depression: r = -0.26 (p = 0.34) for SDNN, r = -0.39 (p = 0.14) for RMSSD). Among participants with elevated baseline anxiety, higher HRV suggested greater improvement in anxiety over time (r = -0.66 (p = 0.08) for SDNN, r = -0.31 (p = 0.45) for RMSSD).

CONCLUSIONS

There was a correlation between HRV and PROs in this study, and among those with elevated anxiety, HRV predicted improvement over time. Digital biomarkers may augment behavioral intervention design and implementation.

Pre-existing parasympathetic dominance seems to cause persistent heart rate slowing after 6 months of fingolimod treatment in patients with multiple sclerosis

PURPOSE

Vagomimetic fingolimod effects cause heart rate (HR) slowing upon treatment initiation but wear off with sphingosine-1-phosphate receptor downregulation. Yet, prolonged HR slowing may persist after months of fingolimod treatment. We evaluated whether cardiovascular autonomic modulation differs before and 6 months after fingolimod initiation between patients with RRMS with and without initially prolonged HR slowing upon fingolimod initiation.

METHODS

In 34 patients with RRMS, we monitored RR intervals (RRI) and blood pressure (BP), at rest and upon standing up before fingolimod initiation. Six hours and 6 months after fingolimod initiation, we repeated recordings at rest. At the three time points, we calculated autonomic parameters, including RRI standard deviation (RRI-SD), RRI-total-powers, RMSSD, RRI high-frequency [HF] powers, RRI and BP low-frequency (LF) powers, and baroreflex sensitivity (BRS). Between and among patients with and without prolonged HR slowing upon fingolimod initiation, we compared all parameters assessed at the three time points (analysis of variance [ANOVA] with post hoc testing; significance: p < 0.05).

RESULTS

Six hours after fingolimod initiation, all patients had decreased HRs but increased RRIs, RRI-SDs, RMSSDs, RRI-HF-powers, RRI-total-powers, and BRS; 11 patients had prolonged HR slowing. Before fingolimod initiation, these 11 patients did not decrease parasympathetic RMSSDs and RRI-HF-powers upon standing up. After 6 months, all parameters had reapproached pretreatment values but the 11 patients with prolonged HR slowing had lower HRs while the other 23 patients had lower parasympathetic RMSSDs and RRI-HF-powers, and BRS than before fingolimod initiation.

CONCLUSION

Our patients with prolonged HR slowing upon fingolimod initiation could not downregulate cardiovagal modulation upon standing up even before fingolimod initiation, and 6 months after fingolimod initiation still had more parasympathetic effect on HR while cardiovagal modulation and BRS were attenuated in the other 23 patients. Pre-existing parasympathetic predominance may cause prolonged HR slowing upon fingolimod initiation.

Association of Novel EEG Biomarkers of Sleep Depth and Cortical Arousability with Cardiac Autonomic Modulation in Adolescents

STUDY OBJECTIVES

To examine the developmental association of the odds ratio product (ORP), an electroencephalographic measure of sleep depth, during non-rapid eye movement (NREM) sleep with 24-hour heart rate variability (HRV), an electrocardiographic measure of cardiac autonomic modulation (CAM), in the transition to adolescence.

METHODS

Leveraging data from the Penn State Child Cohort, we performed longitudinal analyses on 313 children (median [Md] age 9 years) followed-up after Md=7.4y and cross-sectional analyses on 344 adolescents (Md=16y). We extracted ORP during NREM sleep and in the 9 seconds following cortical arousals (ORP-9) from 9-hour, in-lab polysomnography, and frequency- and time-domain HRV indices from 24-h Holter ECG monitoring. Longitudinal and cross-sectional, multivariable-adjusted, regression models examined the association between ORP and ORP-9 with adolescent 24-h HRV indices.

RESULTS

Longitudinally, a greater increase in ORP-9 since childhood was associated with lower daytime Log-LF, SDNN, RMSSD and higher HR in adolescence (p<0.05). A greater increase in ORP since childhood was associated with lower nighttime Log-LF and SDNN (p<0.05). Cross-sectionally, higher ORP and ORP-9 were associated with lower daytime and nighttime Log-LF, SDNN or RMSSD and higher HR within adolescence (p<0.05).

CONCLUSIONS

A greater increase in cortical arousability since childhood is a strong developmental predictor of daytime cardiac autonomic imbalance in adolescence. Shallower sleep depth additionally arises as a proximal determinant of both daytime and nighttime cardiac autonomic imbalance within adolescence. These data suggest a coupling between fine-grained spectral measures of the sleeping brain and those of CAM, which may inform sleep-related cardiovascular risk early in life.

Cholesterol, triglycerides, HDL, and nitric oxide as determinants of resting heart rate variability in non-hospitalized mild post-COVID individuals: a cross-sectional study

BACKGROUND

The association between plasma lipids, nitric oxide (NO) and cardiovascular risk has been well documented in the literature, however, the association between these outcomes and heart rate variability (HRV) in COVID-19 remains incipient as there is no scientific evidence that has investigated this outcome.

OBJECTIVE

Investigate whether metabolic outcomes may be associated with cardiac autonomic behavior arising from short-term HRV variables in non-hospitalized mild post-COVID individuals.

METHODS

This is a cross-sectional study. Individuals of both sexes, aged ≥ 18 years, who tested positive for SARS-CoV-2 according to the RT-PCR test, without the need for hospitalization, were included. The HRV was collected in the supine position for at least 10 min for later analysis in the Kubios software. Metabolic outcomes [high density lipoprotein (HDL) (mg/dL), cholesterol (mg/dL), triglycerides (mg/dL) and NO (µmol/L)] were collected through a blood sample.

RESULTS

Seventy-three individuals were included (post-COVID = 32; control = 41). HRV was worse in the post-COVID group when compared to the control group (p < 0.05). Cholesterol, HDL, triglycerides and NO showed significant correlations with HRV indices. Regression models indicated that cholesterol and triglycerides, as well as NO, explain up to 30.3% of the variations in certain HRV indices, suggesting an impact of metabolic outcomes on autonomic modulation.

CONCLUSION

There is a relationship between plasma lipids, NO and HRV in non-hospitalized individuals with mild COVID-19. Metabolic outcomes are associated and explain between 16.6% and 30.30% of certain variables of resting HRV in post-COVID individuals.

CLINICAL TRIAL NUMBER

Not applicable.

The acute effect of bitemporal electroconvulsive therapy on synchronous changes in heart rate variability and heart rate in patients with depression

Objective.The transient autonomic nervous system responses induced by electroconvulsive therapy (ECT) may serve as critical indicators of treatment efficacy and potential side effects; however, their precise characteristics remains unclear. Considering that the intense stimulation of ECT may disrupt the typical antagonistic relationship between the sympathetic and parasympathetic branches, this study aims to conduct a meticulous analysis of the rapid changes in heart rate variability (HRV) and HR during ECT, with a particular focus on their synchronized interplay.Methods.Pulse interval sequences were collected from 50 sessions of bitemporal ECT administered to 27 patients diagnosed with major depressive disorder. The average HR and ultra-short term HRV indices RMSSD and SDNN, as well as the Poincaré indices SD1, SD2 and SD2/SD1, were calculated using a 10 s sliding window with a step size of 1 s. In particular, the synchronous changes between SD1, SD2, SD2/SD1 and HR were analyzed.Results.The synchronous changes of the indices showed different characteristics over time. In particular, SD1, SD2 and HR increased significantly by 41.50 ± 11.45 ms, 33.97 ± 10.98 ms and 9.68 ± 2.00 bpm respectively between 8 and 20 s, whereas they decreased significantly by 19.89 ± 9.07 ms, 17.54 ± 8.54 ms and 3.80 ± 1.33 bpm respectively between 45 and 53 s after ECT stimulus onset. SD1 and SD2 both had highly significant positive correlations with HR in the above phases.Conclusion.The results suggest that bitemporal ECT induces the sympathetic and parasympathetic co-activation during the early ictal period and brief co-inhibition approximately 45 s after stimulus. Our findings may provide new insights comprehending the mechanisms of ECT and its associated cardiovascular risks.

Optimal frequency bands for pupillography for maximal correlation with HRV

Assessing cognitive load using pupillography frequency features presents a persistent challenge due to the lack of consensus on optimal frequency limits. This study aims to address this challenge by exploring pupillography frequency bands and seeking clarity in defining the most effective ranges for cognitive load assessment. From a controlled experiment involving 21 programmers performing software bug inspection, our study pinpoints the optimal low-frequency (0.06-0.29 Hz) and high-frequency (0.29-0.49 Hz) bands. Correlation analysis yielded a geometric mean of 0.238 compared to Heart Rate Variability features, with individual correlations for low-frequency, high-frequency, and their ratio at 0.279, 0.168, and 0.286, respectively. Extending the study to 51 participants, including a different experiment focusing on mental arithmetic tasks, validated the previous findings and further refined bands, maintaining effectiveness with a geometric mean correlation of 0.236 and surpassing common frequency bands reported in the existing literature. This study represents a pivotal step toward converging and establishing a coherent framework for frequency band definition to be used in pupillography analysis. Furthermore, based on this, it also contributes insights into the importance of more integration and adoption of eye-tracking with pupillography technology into authentic software development contexts for cognitive load assessment at a very fine level of granularity.

Comparing the Effects of Square, 4-7-8, and 6 Breaths-per-Minute Breathing Conditions on Heart Rate Variability, CO2 Levels, and Mood

Square and 4-7-8 breathing are popularly promoted by psychotherapists but have little empirical support. We hypothesized that breathing at 6 breaths per minute (bpm) would improve HRV, reduce blood pressure, and improve mood more than either square or 4-7-8 breathing. We also hypothesized square and 4-7-8 breathing would increase end-tidal CO2 (PETCO2). Eighty-four college students (60% female) had HRV measured at baseline and during 1) square breathing, 2) 4-7-8 breathing, 3) 6 bpm with a 4:6 inhale-to-exhale ratio, and 4) 6 bpm with a 5:5 ratio. We used a 3-lead electrocardiogram to measure HRV and a capnometer to measure PETCO2. We measured mood using the Scale of Positive and Negative Experience (SPANE) after each breathing condition. We used a repeated measures mixed effects model to examine the effects of each breathing technique on HRV, blood pressure, mood, and PETCO2 levels. Breathing at 6 bpm increased HRV measures more than square or 4-7-8 breathing with small to medium effects. None of the breathing conditions resulted in meaningful changes in blood pressure or mood. Unexpectedly, breathing at 6 bpm led to mild over-breathing. While various breathing techniques are used in psychotherapy, their relative efficacy remains unclear. This study found that breathing at 6 bpm is likely more effective at increasing HRV than square or 4-7-8 breathing, albeit with a higher risk of over-breathing. Future studies could examine whether these effects hold over multiple weeks of breathing practice and attend to the effects of different breathing techniques on CO2 levels.

A systematic review of automated prediction of sudden cardiac death using ECG signals

Background. Sudden cardiac death (SCD) stands as a life-threatening cardiac event capable of swiftly claiming lives. It ranks prominently among the leading causes of global mortality, contributing to approximately 10% of deaths worldwide. The timely anticipation of SCD holds the promise of immediate life-saving interventions, such as cardiopulmonary resuscitation. However, recent strides in the realms of deep learning (DL), machine learning (ML), and artificial intelligence have ushered in fresh opportunities for the automation of SCD prediction using physiological signals. Researchers have devised numerous models to automatically predict SCD using a combination of diverse feature extraction techniques and classifiers. Methods: We conducted a thorough review of research publications ranging from 2011 to 2023, with a specific focus on the automated prediction of SCD. Traditionally, specialists utilize molecular biomarkers, symptoms, and 12-lead ECG recordings for SCD prediction. However, continuous patient monitoring by experts is impractical, and only a fraction of patients seeks help after experiencing symptoms. However, over the past two decades, ML techniques have emerged and evolved for this purpose. Importantly, since 2021, the studies we have scrutinized delve into a diverse array of ML and DL algorithms, encompassing K-nearest neighbors, support vector machines, decision trees, random forest, Naive Bayes, and convolutional neural networks as classifiers.Results. This literature review presents a comprehensive analysis of ML and DL models employed in predicting SCD. The analysis provided valuable information on the fundamental structure of cardiac fatalities, extracting relevant characteristics from electrocardiogram (ECG) and heart rate variability (HRV) signals, using databases, and evaluating classifier performance. The review offers a succinct yet thorough examination of automated SCD prediction methodologies, emphasizing current constraints and underscoring the necessity for further advancements. It serves as a valuable resource, providing valuable insights and outlining potential research directions for aspiring scholars in the domain of SCD prediction.Conclusions. In recent years, researchers have made substantial strides in the prediction of SCD by leveraging openly accessible databases such as the MIT-BIH SCD Holter and Normal Sinus Rhythm, which contains extensive 24 h recordings of SCD patients. These sophisticated methodologies have previously demonstrated the potential to achieve remarkable accuracy, reaching levels as high as 97%, and can forecast SCD events with a lead time of 30-70 min. Despite these promising outcomes, the quest for even greater accuracy and reliability persists. ML and DL methodologies have shown great promise, their performance is intrinsically linked to the volume of training data available. Most predictive models rely on small-scale databases, raising concerns about their applicability in real-world scenarios. Furthermore, these models predominantly utilize ECG and HRV signals, often overlooking the potential contributions of other physiological signals. Developing real-time, clinically applicable models also represents a critical avenue for further exploration in this field.

Attenuated cardiac autonomic function in patients with long-COVID with impaired orthostatic hemodynamics

PURPOSE

Long-coronavirus disease (long-COVID) is associated with initial orthostatic hypotension and postural orthostatic tachycardia syndrome. Whether altered autonomic tone underlies these abnormalities is unknown. We compared autonomic function between patients with long-COVID and healthy controls, and within patients with long-COVID with different orthostatic hemodynamic phenotypes.

METHODS

Patients with long-COVID (n = 94; F = 76; 42 years [36, 53 years] with initial orthostatic hypotension: n = 40; F = 32; 49 years [39, 57 years]; postural orthostatic tachycardia syndrome: n = 29; F = 26; 39 years [33, 47 years]; or no abnormalities: n = 25; F = 18; 42 years [35, 49 years]), and healthy controls (n = 33; F = 25; 49 years [30, 62 years]) completed a 10-min active stand with beat-to-beat hemodynamics. Heart rate variability, blood pressure variability, and baroreflex sensitivity were calculated as indirect measures of cardiovascular autonomic health. Continuous data (median [95% confidence interval]) were analyzed with Mann-Whitney U tests or Kruskal-Wallis tests with Dunn's corrections.

RESULTS

Patients with long-COVID had lower upright high frequency heart rate variability (p = 0.04) and low frequency blood pressure variability (p = 0.001) than controls. Patients with initial orthostatic hypotension had lower supine baroreflex sensitivity compared with patients without abnormalities (p = 0.01), and lower supine baroreflex sensitivity (p = 0.001) and high frequency heart rate variability (p = 0.03) than patients with postural orthostatic tachycardia syndrome. Patients with postural orthostatic tachycardia syndrome had lower upright high frequency heart rate variability (p < 0.001) and baroreflex sensitivity (p < 0.001) compared with patients without abnormalities and lower upright low frequency blood pressure variability (p = 0.04) compared with controls.

CONCLUSIONS

Patients with long-COVID have attenuated cardiac autonomic function. Patients with initial orthostatic hypotension have lower supine baroreflex sensitivity. Patients with postural orthostatic tachycardia syndrome have lower upright vascular sympathetic and cardiac parasympathetic modulation. Long-COVID subgroups do not present with homogeneous pathophysiology, necessitating targeted treatment strategies.

Identification of Athleticism and Sports Profiles Throughout Machine Learning Applied to Heart Rate Variability

Heart rate variability (HRV) is a non-invasive health and fitness indicator, and machine learning (ML) has emerged as a powerful tool for analysing large HRV datasets. This study aims to identify athletic characteristics using the HRV test and ML algorithms. Two models were developed: Model 1 (M1) classified athletes and non-athletes using 856 observations from high-performance athletes and 494 from non-athletes. Model 2 (M2) identified an individual soccer player within a team based on 105 observations from the player and 514 from other team members. Three ML algorithms were applied -Random Forest (RF), Extreme Gradient Boosting (XGBoost), and Support Vector Machine (SVM)- and SHAP values were used to interpret the results. In M1, the SVM algorithm achieved the highest performance (accuracy = 0.84, ROC AUC = 0.91), while in M2 Random Forest performed best (accuracy = 0.92, ROC AUC = 0.94). Based on these results, we propose an athleticism index and a soccer identification index derived from HRV data. The findings suggest that ML algorithms, such as SVM and RF, can effectively generate indices based on HRV for identifying individuals with athletic characteristics or distinguishing athletes with specific sports profiles. These insights underscore the importance of integrating HRV assessments systematically into training regimens for enhanced athletic evaluation.

Sex Differences in the Association Between Cardiovascular Autonomic Neuropathy and Mortality in Patients With Type 2 Diabetes: The ACCORD Study

BACKGROUND

Cardiovascular autonomic neuropathy (CAN) is a severe complication of type 2 diabetes. Significant sex-related differences have been observed in type 2 diabetes consequences such as mortality. However, the effect of sex on the association between CAN and mortality in patients with type 2 diabetes is currently unknown.

METHODS AND RESULTS

We assessed 7866 participants in the ACCORD (Action to Control Cardiovascular Risk in Diabetes) trial, including 4730 men and 3136 women. CAN was diagnosed using a combination of heart rate variability and QT interval index, which has 3 different definitions. There were 1364 cases of all-cause mortality and 452 cases of cardiovascular disease mortality during a median follow-up of 9.7 years. We used multivariable Cox regression models to assess the association between different CAN definitions and mortality. In women, various CAN measures were statistically significant associated with an increased risk of all-cause mortality (CAN1: hazard ratio [HR], 1.64 [95% CI, 1.28-2.09]; CAN2: HR, 1.58 [95% CI, 1.17-2.15]; CAN3: HR, 1.78 [95% CI, 1.20-2.65]) and mortality (CAN1: HR, 2.25 [95% CI, 1.44-3.52]; CAN 2: HR, 2.22 [95% CI, 1.28-3.87]; CAN3: HR, 3.31 [95% CI, 1.67-6.57]). CAN was not significantly associated with mortality in men. A significant multiplicative interaction of CAN and sex was observed on both mortality outcomes (P<0.01).

CONCLUSIONS

Significant sex-related differences were observed in CAN and its associated mortality. In terms of mortality risk prevention, CAN should be given greater consideration in women with type 2 diabetes.