Frequency Heart Rate Variability Research Articles

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

Background: Heart rate variability (HRV), an index of the functional status of the autonomic nervous system (ANS), provides an opportunity for early detection of ANS dysfunction. Lower resting, vagally related HRV parameters are associated with increased risk of physical and mental illness. External factors influencing the ANS, such as the testing environment, may impact the interpretation of HRV. This study’s main aim was to determine the reliability of HRV resting and reactivity tests performed at home with children aged 4–9 years. Methods: Fourteen healthy children (female n = 8) aged 6.8 ± 1.5 years participated. Two HRV tests were performed at home via online supervision 7 days apart using a Polar H10 heart rate monitor. The absolute and relative reliability of the pre-exercise resting (5 min) and sub-maximal exercise step test recovery (4 × 30 s segments) HRV time and frequency domains were calculated. Results: The Pearson correlation coefficients for day 1 versus day 7 for the vagal activity HRV domains (RMSSD log) at rest and in the first 30 s and 30–60 s of recovery indicated good-to-excellent relative reliability (r > 0.8, p < 0.01). Absolute reliability was moderate for the resting RMSSD log, with a coefficient of variation (CV) of 5.2% (90% CI: 3.9, 7.8%), high for the first 30 s of standing recovery, with a CV of 10.7% (90% CI: 8.2, 15.7%), and moderate for 30–60 s of recovery, with a CV of 8.7% (90% CI: 6.6, 12.9%). Conclusions: The findings of this pilot study indicate that the resting and exercise recovery HRV measures of vagal activity can be measured reliably at home in children. This represents a novel “at-home” protocol for monitoring ANS health and development in children.

Heart rate variability for neuro-prognostication after CA: insight from the Parisian registry

BackgroundHypoxic ischemic brain injury (HIBI) induced by cardiac arrest (CA) seems to predominate in cortical areas and to a lesser extent in the brainstem. These regions play key roles in modulating the activity of the autonomic nervous system (ANS), that can be assessed through analyses of heart rate variability (HRV). The objective was to evaluate the prognostic value of various HRV parameters to predict neurological outcome after CA. MethodsRetrospective monocentric study assessing the prognostic value of HRV markers and their association with HIBI severity. Patients admitted for CA who underwent EEG for persistent coma after CA were included. HRV markers were computed from 5 minutes signal of the ECG lead of the EEG recording. HRV indices were calculated in the time-, frequency-, and non-linear domains. Frequency-domain analyses differentiated very low frequency (VLF 0.003-0.04Hz), low frequency (LF 0.04-0.15Hz), high frequency (HF 0.15-0.4Hz), and LF/HF ratio. HRV indices were compared to other prognostic markers: pupillary light reflex, EEG, N20 on somatosensory evoked potentials (SSEP) and biomarkers (neuron specific enolase-NSE). Neurological outcome at 3 months was defined as unfavorable in case of best CPC 3-4-5. ResultsBetween 2007 and 2021, 199 patients were included. Patients were predominantly male (64%), with a median age of 60 [48.9-71.7] years. 76% were out-of-hospital CA, and 30% had an initial shockable rhythm. Neurological outcome was unfavorable in 73%. Compared to poor outcome, patients with a good outcome had higher VLF (0.21 vs 0.09 ms2/Hz, p<0.01), LF (0.07 vs 0.04 ms2/Hz, p=0.003), and higher LF/HF ratio (2.01 vs 1.01, p=0.008). Several non-linear domain indices were also higher in the good outcome group, such as SD2 (15.1 vs 10.2, p = 0.016) and DFA α1 (1.03 vs 0.78, p = 0.002). These indices also differed depending on the severity of EEG pattern and abolition of pupillary light reflex. These time-frequency and non-linear domains HRV parameters were predictive of poor neurological outcome, with high specificity despite a low sensitivity. ConclusionIn comatose patients after CA, some HRV markers appear to be associated with unfavorable outcome, EEG severity and PLR abolition, although the sensitivity of these HRV markers remains limited.

High Frequency Heart Rate Variability is Associated with Sensitivity to Affective Touch

C-tactile afferents (CTs) are a class of unmyelinated, mechanosensitive nerve fibre that respond optimally to skin temperature, slow moving touch typical of a caress. They are hypothesised to signal the rewarding value of affiliative tactile interactions. While CT firing frequency is positively correlated with subjective ratings of touch pleasantness, trait differences in sensitivity to the specific hedonic value of CT targeted touch have been reported.Inter-individual differences in vagally mediated, high frequency heart rate variability (HF-HRV) have been linked to variation in visual social cognition. Thus, the aim of the present study was to examine the relationship between resting state HF-HRV and sensitivity to socially relevant CT targeted touch.58 healthy participants first had a 5-minute electrocardiogram. They then rated the pleasantness of 5 randomly presented velocities of robotically delivered touch. Three velocities fell within (1, 3, 10 cm/s) and two outside (0.3, 30 cm/s) the CT optimal range. Each velocity was delivered twice.On a group level, affective touch ratings were described by a negative quadratic function, with CT optimal velocities rated as more pleasant than slower and faster speeds. Simple regression analysis confirmed participants’ HF-HRV was significantly predicted by the quadratic curve fit of their touch ratings, with higher HF-HRV was associated with a better quadratic fit.These findings indicate that, in line with previous observations that higher HF-HRV is associated with enhanced sensitivity to visual social cues, trait differences in autonomic control could account for previously reported individual differences in CT sensitivity.

Cyberbullying victimization and psychopathological symptoms among adolescents varied in BDNF Val66Met polymorphism and vagal tone

BackgroundCyberbullying victimization increases psychopathological symptoms among adolescents. Brain-derived neurotrophic factor (BDNF) gene rs6265 polymorphism or vagal tone as individual diathesis or plasticity has been identified to interact with adverse experiences to affect developmental psychopathology. However, how these different individual factors combined to interact with adverse experiences to affect developmental psychopathology remains unknown. This study sought to investigate the integrally moderating role of BDNF gene rs6265 polymorphism and vagal tone in the relationship between cyberbullying victimization and psychopathological symptoms among adolescents. MethodsThe Cyberbullying Victimization Scale (CVS) and the Youth Self-Report (YSR-2001-CV) were administered to 382 junior school students, their saliva were collected for DNA genotyping and 5 min resting high frequency heart rate variability (HF-HRV) were recorded for assessing vagal tone. ResultsA positive relation between cyberbullying victimization and psychopathological symptoms was found, and this relation was independently and jointly moderated by resting HF-HRV and BDNF gene rs6265 polymorphism. Specifically, the relation was weaker only among adolescents with Val/Val genotype and low resting HF-HRV, but not those with Val/Val genotype and high resting HF-HRV, or Met/Met or Val/Met genotype regardless of resting HF-HRV. ConclusionThese findings suggest a combined moderating effect of BDNF gene rs6265 polymorphism and vagal tone on the relation between cyberbullying victimization and psychopathological symptoms among adolescents.

Effect of series of periodic limb movements in sleep on blood pressure, heart rate and high frequency heart rate variability.

The phenomenon known as periodic limb movements in sleep (PLMS) has been linked to a change in autonomic nervous system (ANS) activity and its effect on circulatory regulation. Autonomic dysfunction or dysregulation in patients with PLMS has been described in some domains; however, any relationship between heart rate variability (HRV) and PLMS has not been clearly established. HRV analysis is a recognised, non-invasive research method that describes the influence of the ANS on heart rate (HR). The aim of our study was to further investigate the dysregulation of autonomic HR control in patients with PLMS. We undertook a retrospective analysis of the polysomnographic (PSG), demographic and medical data of five patients with a total number of 1,348 PLMS. We analysed HR, HRV HF, systolic blood pressure (SBP), and diastolic blood pressure (DBP) for 10 heartbeats before the series of PLMS and 10 consecutive heartbeats as beat-to-beat measurements. The presented method of using successive, short, 10 RR interval segments refers to the time-frequency measurement, which is very clear and useful for presenting changes in the calculated parameters over time and thereby illustrating their dynamics. This method allowed us to assess dynamic changes in HRV HF during successive PLMS series. Statistical analysis was performed using IBM SPSS Statistics (v. 28.0.0.0). The Kruskal-Wallis test was performed to find statistically significant changes from baseline. No statistically significant changes in HR, SBP, or DBP were found in our group, although an increase in the value of the HRV HF was noted, suggesting an increase in intracardiac parasympathetic activity during the subsequent series of PLMS. Our study indicates an increase in parasympathetic activity during the appearance of successive PLMS, which, with the simultaneous lack of changes in HR, may suggest an increase in sympathetic activity, and therefore the appearance of so-called 'autonomic co-activation' resulting in the possibility of life-threatening cardiac events. Our findings add to the literature information regarding HRV in PLMS, and highlight the need for further studies to elucidate the effects of these conditions on the ANS, and on cardiovascular health.

Following your heart: Cardiac autonomic modulation as a feature of decision-making under ambiguity and risk

Decision-making requires a bidirectional flow of information from perception, emotion, and bodily behaviour. Heart rate variability (HRV) provides a non-invasive, cost-effective way to assess this connection. 112 healthy participants completed two established decision tasks under ambiguity and risk. Heart rate was continuously recorded at rest, during, and after task performance. To account for differences in cardiac modulation the sample was stratified by sex. Time, frequency, and non-linear HRV domains were selected to assess vagal modulation and sympatho-vagal balance. Vagally meditated HRV showed a pattern corresponding to a replenishment effect by increasing during decision-making in both tasks compared to rest, and then gradually returning to initial levels during recovery. This effect may indicate successful self-regulation, such as enhanced concentration, or emotional regulation. Regarding decision-making, women and men making disadvantageous decisions under ambiguity had higher vagally mediated HRV than those making advantageous decisions. Consistent with this finding are the results for decisions under risk for women. Contrary, men making disadvantageous decisions under risk, showed lower vagally mediated HRV than those making advantageous decisions. The results suggest that there are sex-specific differences to be investigated in the future. HRV analysis is an effective approach for differentiating somatic characteristics associated with decision-making performance.

Analysis of the factors of heart rate variability affected after a hypoxia tolerance test as a function of gender

Heart rate variability (HRV), the variation of time intervals between heartbeats, reflects the result of the interaction between the autonomic nervous system and the cardiovascular system. Hypoxia is a stressor that causes changes in HRV and a decrease in arterial oxygen saturation (SaO2). The aim of our study is to analyse if the time and frequency domains of HRV are affected after a hypoxia tolerance test in healthy participants as a function of gender. Material and methods: 23 healthy volunteers (11 women and 12 men) with a mean age of 23.08±2.99 performed a hypoxia tolerance test (11%, 5050 m) with the iAltitude simulator. Heart rate and SaO2 were monitored during the test and HRV frequency domain (FD) and time domain (TD) data were obtained. We analysed the five minutes before and after each session. Outcomes: Simulated altitude-induced hypoxia can cause changes in HRV in a group of healthy individuals. Statistically significant differences were also found between before and after the normobaric hypoxia test in the time-domain variables RRm, SDNN, HRm, HR STD, pNN50. In addition, in women statistically significant differences were found in RMSSD, and in the frequency-domain variables HF and LF/HF. While in males, statistically significant differences were found in SDNN. In both men and women, significant differences were observed in RRm, HRm and pNN50. Conclusion: The differences found in HRV after the hypoxia tolerance test indicate that females show a greater activation of the parasympathetic nervous system compared to males. While males showed greater sympathetic activation. Keywords: Heart rate variability, normobaric hypoxia, stress, autonomic nervous system.

Abstract P241: Stress-Induced Autonomic Dysfunction is Associated With Mental Stress-Induced Myocardial Ischemia in Patients With Coronary Artery Disease

Background: Mental stress-induced myocardial ischemia (MSIMI) is associated with adverse cardiovascular outcomes in individuals with coronary artery disease (CAD), but the mechanisms underlying this phenomenon are unknown. We examined the relationship between stress-induced autonomic dysfunction, measured by lower heart rate variability (HRV) in response to stress, and MSIMI in patients with stable CAD. We hypothesized that stress-induced autonomic dysfunction is associated with higher odds of MSIMI. Methods: In 735 participants with stable CAD, we measured high frequency (HF) and low frequency (LF) HRV in 5-minute intervals before and during a standardized laboratory-based speech stressor using Holter monitoring. MSIMI was evaluated with single-photon emission computed tomography myocardial perfusion imaging. HRV at rest and stress were categorized into low (lowest quartile) versus high (upper three quartiles) categories; low category was used as an indicator of autonomic dysfunction. Multivariable logistic regression models were used to examine the association of autonomic dysfunction with MSIMI. Results: The mean age was 58 (SD ±10) years, 35% were women, 44% were Black participants, and 16% developed MSIMI. Compared with high stress HRV, low stress HRV (both HF and LF) was associated with higher odds of MSIMI after adjusting for demographic and clinical factors. LF HRV at rest was also significantly associated with MSIMI with slightly reduced effect estimates. Conclusions: In individuals with CAD, mental stress-induced autonomic dysfunction may be an independent mechanism in the pathogenesis of MSIMI.

Heart Rate Variability (HRV) serves as an objective correlate of distress and symptom burden in multiple sclerosis

BackgroundAutonomic nervous system (ANS) dysfunction is frequently seen in people living with multiple sclerosis (MS). Heart rate variability (HRV) is an easy and objective index for evaluating ANS functioning, and it has been previously used to explore the association between ANS and the experience of symptom burden in other chronic diseases. Given ANS functioning can be influenced by physical and psychological factors, this study investigated whether emotional distress and/or the presence of ANS dysfunction is associated with symptom severity in people living with MS. MethodsParticipants with MS and healthy controls (HC) with no history of cardiac conditions were recruited to self-collect HR data sampled from a chest strap HR monitor (PolarH10). Short-term HR signal was collected for five minutes, and time and frequency HRV analyses were performed and compared between groups. HRV values were then compared to self-reported distress (Kessler Psychological Distress Scale) and MS participants’ self-reported measures of symptom burden (SymptoMScreen). ResultsA total of n = 23 adults with MS (51 ± 12 years, 65 % female, median Patient Determined Disease Steps [PDDS]: 3.0) and n = 23 HCs (43 ± 18 years, 40 % female) completed the study procedures. All participants were able to complete the chest strap placement and HR data capture independently. Participants with MS, compared to the HC participants, had a significantly lower parasympathetic activation as shown by lower values of the root mean square of successive differences between normal heartbeats (RMSSD: 21.86 ± 9.84 vs. 43.13 ± 20.98 ms, p = 0.002) and of high-frequency (HF) power band (HF-HRV: 32.69 ± 12.01 vs. 42.39 ± 7.96 nu, p = 0.016), indicating an overall lower HRV in the MS group. Among individuals with MS, HF-HRV was significantly correlated with the severity of self-reported MS symptoms (r = -0.548, p = 0.010). Participants with MS also reported higher levels of distress compared to HC participants (18.32 ± 6.05 vs. 15.00 ± 4.61, p = 0.050), and HRV correlated with the severity of distress in MS participants (r = -0.569, p = 0.007). A significant mediation effect was also observed, with emotional distress fully mediating the association between HRV and symptom burden. ConclusionsThese findings suggest the potential for ANS dysfunction, as measured by HRV (i.e., lower value of HF power), to be utilized as an objective marker of symptom burden in people living with MS. Moreover, it is apparent that the relationship between HRV and symptom burden is mediated by emotional distress.

A framework for the interpretation of heart rate variability applied to transcutaneous auricular vagus nerve stimulation and osteopathic manipulation.

Reports on autonomic responses to transcutaneous auricular vagus nerve stimulation (taVNS) and osteopathic manipulative techniques have been equivocal, partly due to inconsistent interpretation of heart rate variability (HRV). We developed a mechanistic framework for the interpretation of HRV based on a model of sinus node automaticity that considers autonomic effects on Phase 3 repolarization and Phase 4 depolarization of the sinoatrial action potential. The model was applied to HRV parameters calculated from ECG recordings (healthy adult humans, both genders) before (30 min), during (15 min), and after (30 min) a time control intervention (rest, n = 23), taVNS (10 Hz, 300 μs, 1-2 mA, cymba concha, left ear, n = 12), or occipitoatlantal decompression (OA-D, n = 14). The experimental protocol was repeated on 3 consecutive days. The model simulation revealed that low frequency (LF) HRV best predicts sympathetic tone when calculated from heart rate time series, while high frequency (HF) HRV best predicts parasympathetic tone when calculated from heart period time series. Applying our model to the HRV responses to taVNS and OA-D, revealed that taVNS increases cardiac parasympathetic tone, while OA-D elicits a mild decrease in cardiac sympathetic tone.

The effect of breathing hypoxic gas (15% FIO2 ) on physiological and behavioral outcomes during simulated driving in healthy subjects.

Hypoxia is mainly caused by cardiopulmonary disease or high-altitude exposure. We used a driving simulator to investigate whether breathing hypoxic gas influences driving behaviors in healthy subjects. Fifty-two healthy subjects were recruited in this study, approved by the Science and Engineering Ethical Committee. During simulated driving experiments, driving behaviors, breathing frequency, oxygen saturation (SpO2 ), and heart rate variability (HRV) were analyzed. Each subject had four driving sessions; a 10-min practice and three 20-min randomized interventions: normoxic room air (21% FIO2 ) and medical air (21% FIO2 ) and hypoxic air (equal to 15% FIO2 ), analyzed by repeated measures ANOVA. Driving behaviors and HRV frequency domains showed no significant change. Heart rate (HR; p < 0.0001), standard deviation of the RR interval (SDRR; p = 0.03), short-term HRV (SD1; p < 0.0001), breathing rate (p = 0.01), and SpO2 (p < 0.0001) were all significantly different over the three gas interventions. Pairwise comparisons showed HR increased during hypoxic gas exposure compared to both normoxic interventions, while SDRR, SD1, breathing rate, and SpO2 were lower. Breathing hypoxic gas (15% FiO2 , equivalent to 2710 m altitude) may not have a significant impact on driving behavior in healthy subjects. Furthermore, HRV was negatively affected by hypoxic gas exposure while driving suggesting further research to investigate the impact of breathing hypoxic gas on driving performance for patients with autonomic dysfunction.

Aberrant brain-heart coupling is associated with the severity of post cardiac arrest brain injury.

To investigate autonomic nervous system activity measured by brain-heart interactions in comatose patients after cardiac arrest in relation to the severity and prognosis of hypoxic-ischemic brain injury. Strength and complexity of bidirectional interactions between EEG frequency bands (delta, theta, and alpha) and ECG heart rate variability frequency bands (low frequency, LF and high frequency, HF) were computed using a synthetic data generation model. Primary outcome was the severity of brain injury, assessed by (i) standardized qualitative EEG classification, (ii) somatosensory evoked potentials (N20), and (iii) neuron-specific enolase levels. Secondary outcome was the 3-month neurological status, assessed by the Cerebral Performance Category score [good (1-2) vs. poor outcome (3-4-5)]. Between January 2007 and July 2021, 181 patients were admitted to ICU for a resuscitated cardiac arrest. Poor neurological outcome was observed in 134 patients (74%). Qualitative EEG patterns suggesting high severity were associated with decreased LF/HF. Severity of EEG changes were proportional to higher absolute values of brain-to-heart coupling strength (p < 0.02 for all brain-to-heart frequencies) and lower values of alpha-to-HF complexity (p = 0.049). Brain-to-heart coupling strength was significantly higher in patients with bilateral absent N20 and correlated with neuron-specific enolase levels at Day 3. This aberrant brain-to-heart coupling (increased strength and decreased complexity) was also associated with 3-month poor neurological outcome. Our results suggest that autonomic dysfunctions may well represent hypoxic-ischemic brain injury post cardiac arrest pathophysiology. These results open avenues for integrative monitoring of autonomic functioning in critical care patients.

Long term intraocular pressure fluctuation and epiretinal membrane in patients with glaucoma or glaucoma suspect

Aims/Purpose: The associations between ERM and glaucoma were suggested in several studies. In an animal model undergoing intermittent IOP elevations, a reactive gliosis, a phenotype of ERM, was found in the optic nerve head. We investigated the association between intraocular pressure (IOP) fluctuation and idiopathic ERM in patients with glaucoma or glaucoma suspect.Methods: In this retrospective study, a total of 84 patients with glaucoma or glaucoma suspect were included. Among them, forty one patients had no ERM and forty three patients had ERM. Long‐term fluctuation of IOP was defined as the standard deviation (SD) of IOP at all visits. Patients were divided into two groups according to the median value of SD of IOP: the low IOP fluctuation group and high IOP fluctuation group. Among patients with available heart rate variability (HRV) data, the relationship between the HRV parameter and IOP fluctuation was analysed.Results: Patients with ERM was older and had higher IOP fluctuation and higher proportion of having history of cataract surgery and greater macular thickness (p = 0.018, 0.049, 0.013, &lt; 0.001). The high IOP fluctuation group showed higher proportion of patients with ERM (62.5%) than the low IOP fluctuation group (36.4%, p = 0.028). In the multiple logistic analysis, higher IOP fluctuation group were associated with the presence of ERM (p = 0.047). Among patients with ERM, eyes with stage 3 or 4 ERM had worse visual field defects based on mean deviation than those with stage 1 or 2 ERM (p = 0.025). The high IOP fluctuation group showed higher level of low frequency HRV, an index of sympathetic cardiac control than the low IOP fluctuation group (p = 0.027). Intereye comparison in eyes with ERM and the fellow eyes without ERM, eyes with ERM (2.2 ± 0.9 mmHg) had higher fluctuation of IOP than those without ERM (2.0 ± 0.8 mmHg, p = 0.029).Conclusions: In conclusion, long‐term IOP fluctuation had the relevance to idiopathic ERM in patients with glaucoma or glaucoma suspect. In glaucoma patients with ERM, more advanced stage ERMs were associated with worse visual field damage. Further studies are needed to determine if long‐term IOP fluctuation affects the progression of glaucoma and ERM.

Unveiling the acute neurophysiological responses to strength training: An exploratory study on novices performing weightlifting bouts with different motor learning models.

Currently, there is limited evidence regarding various neurophysiological responses to strength exercise and the influence of the adopted practice schedule. This study aimed to assess the acute systemic effects of snatch training bouts, employing different motor learning models, on skill efficiency, electric brain activity (EEG), heart rate variability (HRV), and perceived exertion as well as mental demand in novices. In a within-subject design, sixteen highly active males (mean age: 23.13 ± 2.09 years) randomly performed snatch learning bouts consisting of 36 trials using repetitive learning (RL), contextual interference (blocked, CIb; and serial, CIs), and differential learning (DL) models. Spontaneous resting EEG and HRV activities were recorded at PRE and POST training bouts while measuring heart rate. Perceived exertion and mental demand were assessed immediately after, and barbell kinematics were recorded during three power snatch trials performed following the POST measurement. The results showed increases in alpha, beta, and gamma frequencies from pre- to post-training bouts in the majority of the tested brain regions (p values ranging from < 0.0001 to 0.02). The CIb model exhibited increased frequencies in more regions. Resting time domain HRV parameters were altered following the snatch bouts, with increased HR (p < 0.001) and decreased RR interval (p < 0.001), SDNN, and RMSSD (p values ranging from < 0.0001 to 0.02). DL showed more pronounced pulse-related changes (p = 0.01). Significant changes in HRV frequency domain parameters were observed, with a significant increase in LFn (p = 0.03) and a decrease in HFn (p = 0.001) registered only in the DL model. Elevated HR zones (> HR zone 3) were more dominant in the DL model during the snatch bouts (effect size = 0.5). Similarly, the DL model tended to exhibit higher perceived physical (effect size = 0.5) and mental exertions (effect size = 0.6). Despite the highest psycho-physiological response, the DL group showed one of the fewest significant EEG changes. There was no significant advantage of one learning model over the other in terms of technical efficiency. These findings offer preliminary support for the acute neurophysiological benefits of coordination-strength-based exercise in novices, particularly when employing a DL model. The advantages of combining EEG and HRV measurements for comprehensive monitoring and understanding of potential adaptations are also highlighted. However, further studies encompassing a broader range of coordination-strength-based exercises are warranted to corroborate these observations.

A novel dynamic cardiorespiratory coupling quantification method reveals the effect of aging on the autonomic nervous system.

Traditional cardiopulmonary coupling (CPC) based on the Fourier transform shares an inherent trade-off between temporal and frequency resolutions with fixed window designs. Therefore, a cross-wavelet cardiorespiratory coupling (CRC) method was developed to highlight interwave cardiorespiratory dynamics and applied to evaluate the age effect on the autonomic regulation of cardiorespiratory function. The cross-wavelet CRC visualization successfully reflected dynamic alignments between R-wave interval signal (RR intervals) and respiration. Strong and continuous CRC was shown if there was perfect temporal coordination between consecutive R waves and respiration, while CRC becomes weaker and intermittent without such coordination. Using real data collected on electrocardiogram (ECG) and respiratory signals, the heart rate variability (HRV) and CRC were calculated. Subsequently, comparisons were conducted between young and elderly individuals. Young individuals had significantly higher partial time and frequency HRV indices than elderly individuals, indicating stronger control of parasympathetic regulation. The overall coupling strength of the CRC of young individuals was higher than that of elderly individuals, especially in high-frequency power, which was significantly lower in the elderly group than in the young group, achieving better results than the HRV indices in terms of statistical significance. Further analyses of the time-frequency dynamics of CRC indices revealed that the coupling strength was consistently higher in the high-frequency (HF) band (0.15-0.4 Hz) in young participants compared to elderly individuals. The dynamic CRC between respiration and HRV indices was accessible by integrating the cross-wavelet spectrum and coherence. Young participants had a significantly higher level of CRC in the HF band, indicating that aging reduces vagus nerve modulation.

Abstract 14007: Decreased Perceived Social Support and Heart Rate Variability Are Associated With Hopelessness in Patients With Ischemic Heart Disease

Introduction: Hopelessness is present in up to 52% of patients with ischemic heart disease (IHD) and associated with a 3.4 times increased risk of death and adverse outcomes. Decreased perceived social support (PSS) has been associated with hopelessness in patients with IHD reporting moderate-severe hopelessness but has not been examined in a well-powered sample with varying levels of hopelessness. Increased PSS is associated with increased high frequency (HF) heart rate variability (HRV) in adults following a stressful event, but the relationship between HRV and hopelessness has not been examined in patients with IHD. Hypothesis: The purpose of this research was to test the hypotheses that 1) lower PSS would be associated with higher hopelessness, and 2) lower HF HRV would be associated with higher hopelessness. Methods: Utilizing a cross-sectional design, 178 participants were enrolled while hospitalized for an IHD event at one large hospital in the Midwestern United States. Data collection occurred two weeks after hospital discharge using the State-Trait Hopelessness Scale, ENRICHD Social Support Inventory, Patient Health Questionnaire-9, a demographic form, and a short-term HRV measurement at rest. Linear models were used to assess association between variables in unadjusted models and models adjusted for demographic and medical history. Results: Majority of participants were male (67%), married (67%), non-Hispanic white (92%), and underwent coronary artery bypass surgery (61%). There was a moderate inverse correlation between PSS and state ( r = -0.31, p &lt; 0.001) and trait ( r = -0.28, p &lt; 0.001) hopelessness in unadjusted models. The relationships remained significant in adjusted models and did not differ between groups comparing sex, type of IHD event, and marital status. There was a moderate inverse correlation between HF HRV and state hopelessness ( r = -0.24, p = 0.023). Results remained significant in adjusted models and did not differ between groups comparing sex, type of IHD event, and beta-blocker prescription. Conclusions: There were significant inverse associations between PSS and hopelessness and HF HRV and hopelessness. Persons with low PSS and/or HF HRV may be at greater risk for experiencing hopelessness following an IHD event.

Abstract 18481: Paroxysmal Atrial Fibrillation and Sleep Apnea: Diurnal Patterning of Autonomic Function and Influence of CPAP Therapy

Introduction: Autonomic nervous system (ANS) dysfunction is implicated in sleep-disordered breathing (SDB) and atrial fibrillation (AF). Hypothesis: We hypothesize that ANS measures of heart rate variability (HRV) exhibit diurnal differences in paroxysmal AF(PAF) relative to SDB severity and is impacted by continuous positive airway pressure (CPAP). Methods: Data from the Sleep Apnea and Atrial Fibrillation Biomarkers and Electrophysiologic Atrial Triggers (SAFEBEAT) study including PAF (7-24 day ECG monitoring), concomitant actigraphy and SDB from polysomnography at baseline and 3-months post-CPAP were analyzed. Linear mixed-effects models were used to assess SDB (apnea hypopnea index (AHI), hypoxia (%sleep time with SaO2&lt;90% and nadir SaO2) and diurnal average HRV (frequency domain (sympathovagal)): low-frequency range (LF), high-frequency range (HF), LF/HF; time domain: mean of normal RR interval (MNN), standard deviation of NN intervals (SDNN), SD1(Poincare plot standard deviation) and effect of 3-month CPAP. Results: In 44869 five-minute epochs from 109 participants with SDB and PAF, during wakefulness, associations of AHI and LFP, nadir SaO2 with sympathovagal measures (LFP, LHR) and time domain measures (SDNN, SD2) were observed. A sleep-wake significant interaction was observed with all HRV measures and stronger associations in wake than sleep. Baseline to follow-up CPAP time domain measures were increased during wakefulness (MNN, SDNN, RMSSD, CV, SD1, and SD2) and increased during sleep (MNN, SD2, LHR). Conclusions: Diurnal variation of autonomic measures in moderate to severe SDB was observed and association with SDB severity was more pronounced during wakefulness; CPAP influenced autonomic function. These findings in earlier onset AF may contribute to electrophysiological remodeling with implications for ANS-specific chronobiology in SDB.

Introducing outdoor office work to reduce stress among office workers in Sweden

Abstract Background Office workplace stress is concerning as it leads to adverse and chronic health outcomes. Outdoor office work (OOW), an innovative practice may address these challenges as being outdoors has potential benefits. This study aims to assess stress among office workers that are working in their normal indoor office compared to practicing OOW and identifying facilitators and barriers for doing OOW. Methods In a feasibility study, 9 office workers were asked to work indoors the 1st week and OOW for at least 30 minutes per day during the 2nd week. They wore a heart rate variability (HRV) monitor (FirstBeat BG3) for 2 weeks while at work to assess objective stress. Subjective stress was assessed via daily surveys using a scale of 1 to 10 from “not stressed at all” to “very stressed”. They were instructed to use the app “Our Voice Discovery Tool” to take photos of facilitators or barriers to practicing OOW. Subjective stress data was analysed using paired sample t-test in SPSS 28. Photos were categorised into themes. Analysis of HRV time and frequency parameters is underway. Results Preliminary findings show statistically significant decrease in stress scores between week 1 (M = 4.42, SD = 1.43) and week 2 (M = 3.74, SD = 1.31) t(7)=1.91, p=.049 (one-tailed), mean decrease in self-rated stress was .68 with a 95% confidence interval ranging from -.12 to 1.43. The Cohen's d (.67) indicated a medium effect size. Picture analysis revealed themes related to “convenience/comfort”, equipment/facilities”, and “weather” as barriers. Out of 76 pictures, most themed “nature”, both indoor and outdoor, were marked as positive experiences. Conclusions Reduction in subjective stress from week 1 to week 2 suggests OOW's potential as useful method to reduce work-related stress. Picture analysis suggests, to ensure a healthier milieu for office workers, conditions conducive to OOW such as outdoor work facilities and green spaces in offices’ vicinity may need to be facilitated by employers. Key messages • Outdoor office work (OOW) may reduce workplace stress, potentially improving employee health, well-being, and productivity. • Employers should facilitate outdoor workspaces and green areas to promote healthier office environments.

Wrist-Worn Sensor Validation for Heart Rate Variability and Electrodermal Activity Detection in a Stressful Driving Environment.

Wearable sensors are widely used to gather psychophysiological data in the laboratory and real-world applications. However, the accuracy of these devices should be carefully assessed. The study focused on testing the accuracy of the Empatica 4 (E4) wristband for the detection of heart rate variability (HRV) and electrodermal activity (EDA) metrics in stress-inducing conditions and growing-risk driving scenarios. Fourteen healthy subjects were recruited for the experimental campaign, where HRV and EDA were recorded over six experimental conditions (Baseline, Video Clip, Scream, No-Risk Driving, Low-Risk Driving, and High-Risk Driving) and by means of two measurement systems: the E4 device and a gold standard system. The overall quality of the E4 data was investigated; agreement and reliability were assessed by performing a Bland-Altman analysis and by computing the Spearman's correlation coefficient. HRV time-domain parameters reported high reliability levels in Baseline (r > 0.72), Video Clip (r > 0.71), and No-Risk Driving (r > 0.67), while HRV frequency domain parameters were sufficient in Baseline (r > 0.58), Video Clip (r > 0.59), No-Risk (r > 0.51), and Low-Risk Driving (r > 0.52). As for the EDA parameters, no correlation was found. Further studies could enhance the HRV and EDA quality through further optimizations of the acquisition protocol and improvement of the processing algorithms.

Test-retest reliability of short- and long-term heart rate variability in individuals with spinal cord injury

Study designCross-sectional.ObjectivesTo investigate test-retest reliability of heart rate variability (HRV) metrics in SCI without restriction of activity over long (24-h) and shorter durations (5-min, 10-min, 1-h, 3-h and 6-h).SettingsUniversity hospital in Khon Kaen, Thailand.MethodsForty-five participants (11 with tetraplegia and 34 with paraplegia) underwent two 24-h recordings of RR-intervals to derive time and frequency HRV metrics. Relative reliability was assessed by intraclass correlation coefficient (ICC) and absolute reliability by coefficient of variation (CV) and Bland–Altman limits of agreement (LoA).ResultsFor 5- and 10-min durations, eight of eleven HRV metrics had moderate to excellent reliability (ICC 0.40–0.76); the remaining three were poor (ICC < 0.4). HRV values from 1-h and 3-h durations showed moderate to excellent reliability (ICC of 0.46–0.81), except for 1-h reliability of ULF and TP (ICC of 0.06 and 0.30, respectively). Relative reliability was excellent (ICC of 0.77–0.92) for 6-h and 24-h durations in all HRV metrics. Absolute reliability improved as recording duration increased (lower CVs and narrower LoAs). Participants with high AD risk (SCI level at or above T6) showed lower test-retest reliability of HF and LF values than participants with low AD risk.ConclusionRelative reliability of HRV was excellent for 6-h and 24-h. The best absolute reliability values were for 24-h duration. Time-domain outcomes were more reliable than frequency domain outcomes. Participants with high risk of AD, particularly those with tetraplegia, showed lower reliability, especially for HF and LF.