Heart Rate Variability Outcomes Research Articles

Abstract P196: The Effects of Initiating a 24-hour Fast With a Low versus a High Carbohydrate Protein Shake on Heart Rate Variability in the Elderly

Introduction: While multiple studies demonstrate the potential cardiovascular benefits of fasting, the effects of the fast-initiating meal have not been evaluated. The aim of this secondary analysis was to examine the effects of the macronutrient composition of a fast-initiating meal on the autonomic nervous system through measurements of heart rate variability (HRV) in older, sedentary adults with abdominal obesity. Methods: Using a crossover design, each of the 24 participants (13 male, 11 female) completed two 24-hour fasts (8:00 am to 8:00 am) separated by 6-10 days. Participants were 59.54 ± 6.67 years old and had a body mass index of 31.59 ± 5.59 kg/m 2 . Each fast was initiated with either a low carbohydrate protein shake or an isocaloric and isovolumetric high carbohydrate protein shake (592.13 ± 104.57 kcal). Heart rate variability was measured for 10 minutes immediately prior to, one hour after, and then 24 hours after shake consumption. Results: A mixed effects model with repeated measures was used to assess the effects of the fasting conditions on various HRV outcomes. The sympathetic (SNS) index increased significantly over the time of each fast (p = 0.0033), but was not different between conditions (p = 0.7229). The parasympathetic PNS index experienced no change over time (p = 0.1521) and no change between conditions (p = 0.8961). The stress index increased over time (p = 0.0021), but was not different between conditions (p = 0.7308). There was no difference in standard deviation of the normal-to-normal interval (SDNN) or root mean square of successive difference (RMSSD) over time (p = 0.2022 and p = 0.2770, respectively) or between condition (p = 0.9054 and p = 0.9857, respectively). The High Frequency (HF) reading was elevated in the high-carbohydrate condition compared to the low-carbohydrate condition (p < 0.0001), and the low frequency to high frequency (LF/HF) ratio showed no difference between conditions (p = 0.3460), but increased over time (p = 0.0044) and demonstrated a time by condition interaction (p = 0.0089). Conclusions: Acute fasting places strain on the cardiometabolic systems as evident by the increased SNS index and stress index as well as the increase in LF/HF ratio over the course of both fasts. A low carbohydrate shake reduced HF readings, indicating more anxiety or panic in this condition. These results agree with previous works and are unique in demonstrating that most HRV parameters are neither strengthened nor weakened by the composition of the pre-fast meal.

Dose-dependent response of prefrontal transcranial direct current stimulation on the heart rate variability: An electric field modeling study.

Transcranial direct current stimulation (tDCS) of the prefrontal cortex (PFC) modulates the autonomic nervous system by activating deeper brain areas via top-down pathway. However, effects on the nervous system are heterogeneous and may depend on the amount of current that penetrates. Therefore, we aimed to investigate the variable effects of tDCS on heart rate variability (HRV), a measure of the functional state of the autonomic nervous system. Using three prefrontal tDCS protocols (1.5, 3 mA and sham), we associated the simulated individual electric field (E-field) magnitude in brain regions of interest with the HRV effects. This was a randomized, double-blinded, sham-controlled and within-subject trial, in which healthy young-adult participants received tDCS sessions separated by 2 weeks. The brain regions of interest were the dorsolateral PFC (DLPFC), anterior cingulate cortex, insula and amygdala. Overall, 37 participants were investigated, corresponding to a total of 111 tDCS sessions. The findings suggested that HRV, measured by root mean squared of successive differences (RMSSD) and high-frequency HRV (HF-HRV), were significantly increased by the 3.0 mA tDCS when compared to sham and 1.5 mA. No difference was found between sham and 1.5 mA. E-field analysis showed that all brain regions of interest were associated with the HRV outcomes. However, this significance was associated with the protocol intensity, rather than inter-individual brain structural variability. To conclude, our results suggest a dose-dependent effect of tDCS for HRV. Therefore, further research is warranted to investigate the optimal current dose to modulate HRV.

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

Short-term exposure particulate matter with a diameter of 10 µm or less (PM10) and fine particulate matter (PM2.5) has been associated with heart rate variability (HRV), but exposure to ultrafine particles (UFP) has been less well examined. We investigated the associations between the HRV outcomes and short-term exposure to UFP, PM10 and PM2.5 among school-aged children and seniors. CorPuScula (Coronary, Pulmonary and Sanguis) is a longitudinal, repeated-measure panel study conducted in 2000-2002 in Munich, Germany including 52 seniors (58-94 years old) with 899 observations and 50 children (6-10 years old) with 925 observations. A 10-min resting electrocardiogram was performed to assess resting HRV outcomes [Standard Deviation of Normal to Normal Intervals (SDNN), Root Mean Square of Successive Differences between Normal Heartbeats (RMSSD), Low Frequency power (LF), High Frequency power (HF), ration between low and high frequency (LF/HF)]. UFP and PM exposures were measured near the care home and school yard for seniors and children, respectively. Mean exposures during the day of examination (9-21 h) as well as 3-h, 12-h, 24-h, one-day, and two-day lags were assessed. Linear mixed-effect models were used to investigate the associations between short-term air pollution and HRV outcomes separately in children and seniors. The models were adjusted for sex, age, weather conditions (temperature, precipitation, and water vapor pressure), BMI, lifestyle and medical information. Two and multipollutant models adjusted for NO2 and O3 were performed. Among seniors, we observed increases in SDNN, LF, HF and LF/HF ratio after short-term exposure to UFP (hourly and daily lags) in contrast to decreases in SDNN and RMSSD after exposure to PM10. Associations were generally robust to two- and multipollutant adjustment. Among children, we observed increases of the LF/HF ratio after short-term exposures to UFP at lags 12 and 24 h. In contrast, we observed decreases of the ratio after exposure to PM2.5 and PM10. Results were largely unchanged for multipollutant modelling, however we found a more pronounced increase in SDNN and LF/HF (UFP lag 12 and 24 h) after adjusting for NO2. Overall, among seniors, we observed associations of UFP and PM10 exposure with sympathetic responses of the ANS, which play an important role in sudden heart attacks or arrhythmia. Among children we found more inconsistent associations between UFP and a delayed increase in HRV. Adjusting for co-pollutants including NO2 and O3 yielded robust results.

Higher Habitual Lying Time is Inversely Associated with Vagal-Related Heart Rate Variability Outcomes in Younger Adults.

Heart rate variability (HRV) is a well-established non-invasive marker of autonomic cardiac control. We test whether time spent sitting (negatively) versus lying (positively) influences vagal HRV outcomes. HRV (10-min supine electrocardiogram) and free-living postures (dual-accelerometer configuration, 7-d) were measured in 31 young healthy adults (15♀, age: 23±3). Habitual lying (66±61 mins/day), but not sitting time (558±109 mins/day), total sedentary time (623±132 mins/day), nor step counts (10752±3200 steps/day; all, p>0.090) was associated with root mean square of successive cardiac interval differences (ρ=-0.409,p=0.022) and normalized high-frequency HRV (ρ=-0.361,p=0.046). These findings document a paradoxical negative impact of waking lying time on cardioautonomic innervation.

Heart rate variability changes in patients with obstructive sleep apnea: A systematic review and meta-analysis.

Obstructive sleep apnea is a common sleep breathing disorder related to autonomic nervous function disturbances. Heart rate variability is an important non-invasive indicator of autonomic nervous system function. The PubMed, Embase, Medline and Web of Science databases were systematically searched for English literature comparing patients with obstructive sleep apnea with controls up to May 2021. Heart rate variability outcomes, including integrated indices (parasympathetic function and total variability), time domain indices (the standard deviation of NN intervals and the root mean square of the successive differences between normal heartbeats) and frequency domain indices (high-frequency, low-frequency, very-low-frequency and the ratio of low-frequency to high-frequency) were derived from the studies. Twenty-two studies that included 2565 patients with obstructive sleep apnea and 1089 healthy controls were included. Compared with controls, patients with obstructive sleep apnea exhibited significantly reduced parasympathetic function. For the obstructive sleep apnea severity subgroup meta-analysis, patients with severe obstructive sleep apnea had significantly lower parasympathetic function, high-frequency, root mean square of the successive differences between normal heartbeats and standard deviation of NN intervals, and higher low-frequency and ratios of low-frequency to high-frequency. However, only the ratio of low-frequency to high-frequency was significantly higher in patients with moderate obstructive sleep apnea than in controls. Finally, for the collection time analysis, patients with obstructive sleep apnea had significantly higher low-frequency and ratio of low-frequency to high-frequency at night, significantly lower parasympathetic function, high-frequency, root mean square of the successive differences between normal heartbeats and standard deviation of NN intervals, and a higher ratio of low-frequency to high-frequency during the day than controls. Autonomic function impairment was more serious in patients with severe obstructive sleep apnea. During sleep, low-frequency can well reflect the impairment of autonomic function in obstructive sleep apnea, and the ratio of low-frequency to high-frequency may play an important role in obstructive sleep apnea diagnosis.

Autonomic Nervous System Function After Dynamic Exertion Among Athletes At Medical Clearance Following Concussion

The autonomic nervous system (ANS) is commonly disrupted following sport-related concussion (SRC), and safe return to play/activity (RTP/A) is predicated on physiological recovery of ANS and other inter-related subsystems. Ultrashort (<5 min) heart rate variability (HRV) following exercise may be a proxy measure of ANS function but has predominately been measured following aerobic exertion without sport-specific movements. Dynamic exertion involves rapid change-of-direction tasks at varying intensities to perturb the vestibular and ocular subsystems in addition to the ANS. To date, researchers have yet to examine ultrashort HRV following dynamic exertion among athletes at medical clearance to RTP/A. PURPOSE: Compare age-estimated percentage of heart rate (HR %max) throughout a dynamic exertion assessment, in addition to post-exertion blood pressure and ultrashort HRV outcomes between athletes upon RTP/A from SRC with healthy athletes. METHODS: A sample of 23 (Female = 10, 43.5%) athletes at medical clearance to RTP/A (CONCUSS) and 23 sex-, age-, and sport-matched healthy athletes (CONTROL) completed a 5-min seated rest period prior to and following the dynamic exertion test. The dynamic exertion test is comprised of a12-min treadmill run and a series of functional movements and change-of-direction tasks. The root-mean-square of the successive differences (RMSSD) and standard deviation of successive heart beats (SDNN) were obtained from the final 3-min of pre- and post-EXiT rest periods. Between-group comparisons were conducted with a series of independent sample t-tests for HR %max and blood pressure, and 2X2 (GROUP X TIME) ANOVAs for RMSSD and SDNN. RESULTS: Main effects were observed for GROUP whereby CONCUSS had lower (less variable) RMSSD (p = .049, Ƞp2 = .209) and SDNN (p = .047, Ƞp2 = .212) than CONTROL, and for TIME as a reduction in RMSSD (p < .001, Ƞp2= .740) and SDNN (p < .001, Ƞp2= .760). HR %max and blood pressure were similar between groups (p > .05). CONCLUSION: ANS dysfunction may persist beyond clinical recovery in some athletes returning to sport after SRC. This is the first study to report differences in HRV between recently concussed and healthy athletes after dynamic exertion. Future work should consider the role of ANS function post-exertion to improve medical clearance decision making.

Effect of 4-day Online Breath Meditation Workshop on Ballistocardiography-based Sleep and Cardiac Health Assessments among Medical Professionals of a Tertiary Care Hospital in North India during COVID-19.

Medical professionals (MPs) are facing stress, sleep deprivation, and burnout due to pandemic-related high patient inflow and consistent work shifts. Yoga and meditation are feasible, cost-effective, evidence-based, and well-accepted tools having multifold mental and physical health benefits. In this ongoing open-label single-arm trial, we assessed changes in sleep, heart rate variability (HRV), and vitals before and after a 4-day online breath meditation workshop (OBMW) among 41 MPs at a tertiary care hospital in northern India during COVID-19 pandemic. Outcomes were assessed at baseline and after the 4-day workshop using a ballistocardiography-based contactless health monitoring device. The workshop was conducted online. Two participants were excluded due to a lack of adherence. A highly significant increase was seen in total sleep duration (p = 0.000) and duration of deep sleep (p = 0.001), rapid eye movement (REM) sleep (p = 0.000), and light sleep (p = 0.032). HRV outcomes of the standard deviation of normal-to-normal R-R intervals (SDNN) and root mean square of successive differences between adjacent normal heartbeat (RMSSD) also improved significantly (p = 0.000) while heart rate reduced significantly (p = 0.001). No significant change was observed in breath rate, total time awake, or in the low-frequency by high-frequency (LF/HF) spectrum of HRV. Four days of OBMW improved sleep and HRV among MPs, strengthening the fact that yoga and meditation can help induce psychophysical relaxation and prove to be an effective tool to combat stress and sleep deprivation. As the stakeholders in patient care, that is, MPs are healthy, it will further improve patient care and reduce the chance of medical errors.

Mediation Analysis in Manual Therapy Research

ObjectiveThe purpose of this study was to illustrate the applicability of mediation analysis in the manual therapy field by assessing whether pain intensity, duration of pain, or the change in systolic blood pressure mediated the heart rate variability (HRV) of patients with musculoskeletal pain who received manual therapy. MethodsA secondary data analysis from a 3-arm, parallel, randomized, placebo-controlled, assessor-blinded, superiority trial was performed. Participants were randomized into spinal manipulation, myofascial manipulation, or placebo groups. Cardiovascular autonomic control was inferred from resting HRV variables (low-high frequency power ratio; LF/HF) and blood pressure responsiveness to a sympathoexcitatory stimulus (cold pressor test). Pain intensity and duration were assessed. Mediation models analyzed whether pain intensity, duration, or blood pressure independently affected the improvement of the cardiovascular autonomic control of patients with musculoskeletal pain after intervention. ResultsThe first assumption of mediation was met for LF/HF with statistical evidence of a total effect of spinal manipulation, as compared with placebo on HRV outcomes (β = 0.77 [0.17-1.30]); second and third assumptions showed no statistical evidence of a relationship between the intervention and pain intensity (β = –5.30 [–39.48 to 28.87]), pain intensity, and LF/HF (β = 0.00 [–0.01 to 0.01]). ConclusionIn this study of causal mediation analysis, the baseline pain intensity, duration of pain, and responsiveness of the systolic blood pressure to a sympathoexcitatory stimulus did not mediate the effects of the spinal manipulation on the cardiovascular autonomic control of patients with musculoskeletal pain. Accordingly, the immediate effect of spinal manipulation on the cardiac vagal modulation of patients with musculoskeletal pain may more likely be related to the intervention rather than the mediators investigated.

Geomagnetic disturbances reduce heart rate variability in the Normative Aging Study

BackgroundSolar and geomagnetic activity (GA) have been linked to increased cardiovascular (CVD) events. We hypothesize that heart rate variability (HRV) may be the biological mechanism between increased CVD risk and intense geomagnetic disturbances (GMD). MethodsTo evaluate the impact of GA and intense GMD on HRV in 809 elderly men [age mean 74.5 (SD = 6.8)] enrolled in the Normative Aging Study (Greater Boston Area), we performed repeated-measures using mixed-effects regression models. We evaluated two HRV outcomes: the square root of the mean squared differences of successive normal-to-normal intervals (r-MSSD) and the standard deviation of normal-to-normal heartbeat intervals (SDNN) in milliseconds (ms). We also compared the associations between Kp and HRV in patients with and without comorbidities such as diabetes and coronary heart diseases (CHD). We used data on global planetary K-Index (Kp) from middle latitudes as a GA and GMD (>75th Kp) parameters from the National Oceanic and Atmospheric Agency's Space Weather Prediction Center. ResultsWe found a near immediate effect of continuous and higher Kp on reduced HRV for exposures up to 24 h prior to electrocardiogram recording. A 75th percentile increase in 15-hour Kp prior the examination was associated with a −14.7 ms change in r-MSSD (95 CI: −23.1, −6.3, p-value = 0.0007) and a −8.2 ms change in SDNN (95 CI: −13.9, −2.5, p-value = 0.006). The associations remained similar after adjusting the models for air pollutants over the exposure window prior to the event. In periods of intense GMD, the associations were stronger in patients with CHD and non-diabetes. ConclusionsThis is the first study to demonstrate the potential adverse effects of geomagnetic activity on reduced heart rate variability in a large epidemiologic cohort over an extended period, which may have important clinical implications among different populations.

Longitudinal association of early childhood lead exposure and adolescent heart rate variability: influence of parental education

Lead exposure has been shown to dysregulate physiological stress responses. However, few studies have investigated the effect of lead exposure on later heart rate variability (HRV), an indicator of a stress response, in large samples of children. Furthermore, the interaction between social environmental factors and lead exposure in childhood, which commonly co-occur, remains understudied. This study examined relationships between childhood lead exposure and early adolescent physiological stress responses at different levels of parental education. Participants were 406 children from Jintan, China. Blood lead levels (BLLs) and parental education data were collected at 3–5 years of age, and HRV outcomes assessed at 12 years via frequency domain measures (LF/HF ratio) collected during an induced stress test. Results show a significant interaction between parental education and BLLs at 3–5 years. This relationship was found to be most consistent for the interaction between BLLs and mother’s years of education for both the planning (β = 0.12, p = 0.046) and speaking (β = 0.11, p = 0.043) phase of the stress task, suggesting that increasing years of mother’s education may enhance the deleterious influence of lead exposure on the HRV frequency measure, LF/HF ratio. This research highlights the complexity in lead exposure induced outcomes.

Sympathovagal Balance Is a Strong Predictor of Post High-Volume Endurance Exercise Cardiac Arrhythmia.

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

Estimating Resting HRV during fMRI: A Comparison between Laboratory and Scanner Environment.

Heart rate variability (HRV) is regularly assessed in neuroimaging studies as an indicator of autonomic, emotional or cognitive processes. In this study, we investigated the influence of a loud and cramped environment during magnetic resonance imaging (MRI) on resting HRV measures. We compared recordings during functional MRI sessions with recordings in our autonomic laboratory (LAB) in 101 healthy subjects. In the LAB, we recorded an electrocardiogram (ECG) and a photoplethysmogram (PPG) over 15 min. During resting state functional MRI, we acquired a PPG for 15 min. We assessed anxiety levels before the scanning in each subject. In 27 participants, we performed follow-up sessions to investigate a possible effect of habituation. We found a high intra-class correlation ranging between 0.775 and 0.996, indicating high consistency across conditions. We observed no systematic influence of the MRI environment on any HRV index when PPG signals were analyzed. However, SDNN and RMSSD were significantly higher when extracted from the PPG compared to the ECG. Although we found a significant correlation of anxiety and the decrease in HRV from LAB to MRI, a familiarization session did not change the HRV outcome. Our results suggest that psychological factors are less influential on the HRV outcome during MRI than the methodological choice of the cardiac signal to analyze.

The Acute Effects of Aerobic Exercise on Nocturnal and Pre-Sleep Arousal in Patients with Unipolar Depression: Preplanned Secondary Analysis of a Randomized Controlled Trial.

Unipolar depression is associated with insomnia and autonomic arousal. The aim of this study was to quantify the effect of a single bout of aerobic exercise on nocturnal heart rate variability and pre-sleep arousal in patients with depression. This study was designed as a two-arm, parallel-group, randomized, outcome assessor-blinded, controlled, superiority trial. Patients with a primary diagnosis of unipolar depression aged 18–65 years were included. The intervention consisted of a single 30 min moderate-intensity aerobic exercise bout. The control group sat and read for 30 min. The primary outcome of interest was RMSSD during the sleep period assessed with polysomnography. Secondary outcomes were additional heart rate variability outcomes during the sleep and pre-sleep period as well as subjective pre-sleep arousal. A total of 92 patients were randomized to either the exercise (N = 46) or the control (N = 46) group. Intent-to-treat analysis ANCOVA of follow-up sleep period RMSSD, adjusted for baseline levels and minimization factors, did not detect a significant effect of the allocation (β = 0.12, p = 0.94). There was no evidence for significant differences between both groups in any other heart rate variability measure nor in measures of cognitive or somatic pre-sleep arousal. As this is the first trial of its kind in this population, the findings need to be confirmed in further studies. Patients with depression should be encouraged to exercise regularly in order to profit from the known benefits on sleep and depressive symptoms, which are supported by extensive literature.

Assessment of autonomous nerve system through non-linear heart rate variability outcomes in sedentary healthy adults.

BackgroundHeart rate variability (HRV) is a psycho-physiological phenomenon with broad health implications. Different data analysis methods have been used to assess the autonomic nervous system activity, but the validation of new indexes that accurately describe its balance through non-invasive methods (i.e., HRV analysis) is of clinical interest. This study aimed: (i) to evaluate the association of the Stress Score (SS) and the Sympathetic/Parasympathetic Ratio (S/PS) with time domain and frequency domain analysis of HRV, and (ii) to set reference values of SS and S/PS in sedentary healthy adults.MethodsA total of 156 sedentary healthy adults (38.4 ± 15.57 years old, 81 women), aged were involved in this study. HRV was measured for 15 min in a supine position at rest. SS and S/PS were calculated from the non-linear HRV analyses based on Poincare Plot.ResultsStress Score showed a non-linear negative power-law relationship with SDNN (β = −0.969; R2 = 0.963; P < 0.001), RMSSD (β = −0.867; R2 = 0.722; P < 0.001), high frequency (β = −0.834; R2 = 0.752; P =< 0.001), low frequency (β = −0.627; R2 = 0.330; P < 0.001), SD1 (β = −0.867; R2 = 0.722; P < 0.001) and SD2 (β = −1.000; R2 > 0.999; P < 0.001). There was observed a negative cubic relationship between SS with PNN50 (β = −1.972; R2 = 0.644; P < 0.001). A linear regression model was conducted between SS with Ratio Low/High Frequency (β = 0.026; R2 < 0.001; P = 0.750). Non-linear power-law regression models were built between S/PS and SDNN (β = −0.990; R2 = 0.981; P < 0.001), RMSSD (β = −0.973; R2 = 0.939; P < 0.001), high frequency (β = −0.928; R2 = 0.970; P < 0.001), low frequency (β = −2.344; R2 = 0.557; P < 0.001), SD1 (β = −0.973; R2 = 0.939; P < 0.001) and SD2 (β = −0.611; R2 = 0.908; P < 0.001). A non-linear negative regression model was built between S/PS and PNN50 (β = −3.412; R2 = 0.868; P < 0.001). A linear regression model was conducted between S/PS and SD2/SD1 (β = 0.075; R2 = 0.006; P < 0.001).ConclusionOur results support the use of SS as a sympathetic activity marker, and S/PS as an indicator of the sympathetic and parasympathetic activity of the autonomic nervous system in sedentary healthy adults.

Association Between Heart Rate Variability and Parkinson's Disease: A Meta-analysis.

A systematic review which aims to assess the evidence regarding the function of the autonomic heart rate regulation system among Parkinson's disease (PD) patients. The main objective of the study is to compare heart rate variability (HRV) between those with and without PD from published studies. The subgroup analyses aimed to investigate the impact of treatment and disease duration on heart rate variability (HRV), assessed by measuring sympathetic and parasympathetic activity via low-frequency (LF) and high-frequency (HF) power spectrum scores, in patients with Parkinson's disease (PD). PubMed, Cochrane Library, Embase and Web of Science were searched using the keywords "Parkinson's disease" and "heart rate variability". Studies that reported at least one HRV variable were included. The quality of the included studies was evaluated, and the relevant information was extracted. A meta-analysis was carried out with Stata software. We followed the PRISMA guidelines for all stages of the meta-analysis. PROSPERO registration number: CRD42021242766. Thirteen references (16 studies) were included in our analysis. The LF values (g -0.27; 95% confidence interval (CI) -0.53 to -0.01) of the patients with PD were lower than the controls. No significant differences in HF values (g -0.11; 95% CI -0.28 to 0.06) were observed between groups. Subgroup analyses of HRV outcomes in patients stratified by treatment status and disease duration were performed. For LF, patients with a disease duration of less than 5 years presented lower HF (g -0.25; 95% CI -0.44 to -0.06) values than controls. Regarding HF, patients receiving treatment presented lower HF (g -0.22; 95% CI -0.40 to 0.05) values than controls, and patients with a disease duration greater than 5 years also presented lower HF (g -0.29; 95% CI -0.56 to -0.03) values than controls. We have confirmed and elaborated on the hypothesis of sympathovagal imbalance in PD. Knowledge of the effect of sympathovagal balance on HRV may inform the design of therapeutic regimens for PD. However, between-study heterogeneity and methodological issues limit the generalizability of the evidence; thus, future studies employing strict methodologies are warranted. Our meta-analysis found that PD is associated with reduced HRV values, which indicates that both sympathetic and vagal activities are decreased. Patients in the early stage of PD have sympathetic autonomic nerve dysfunction, with only minor damage to sympathetic activity.

Sleep Quality Is Associated With Nighttime Heart Rate Variability In Young Adults

Heart rate variability (HRV) reflects autonomic nervous system function, and low nighttime HRV is linked to reduced parasympathetic control. Optimal parasympathetic function is important for the induction and maintenance of sleep, overall wellbeing, and is inversely associated with chronic disease. In young adults, 60% of whom report poor sleep quality, disrupted parasympathetic function may reflect suboptimal health and lifestyle behaviors. While there is an established relationship between physical activity (PA), stress, and nighttime HRV, the associations between HRV and other lifestyle-related factors such as sleep quality and social jet lag (SJL) in young adult populations are yet to be determined. PURPOSE: The purpose of this study was to determine the relationship between nighttime HRV and sleep characteristics in young adults. METHODS: Healthy young adults (n=33, 18.6 ± 0.7 years, 69.6% female) wore a chest-strap heart rate monitor for 24 hours and a triaxial accelerometer on the non-dominant wrist for 7 days during free-living PA and sleep. Average sleep duration and SJL were determined from objective sleep data, with SJL calculated as the difference in hours between the midpoint of sleep on weeknights (school) and weekend (free) nights. The Pittsburgh Sleep Quality Index (PSQI) and Perceived Stress Scale were used as subjective measures of sleep quality and stress. Nighttime HRV outcomes were calculated using R-R intervals between the hours of 1:00 AM - 5:00 AM. Linear regression assessed multivariate relationships among sleep duration, quality, SJL, and HRV while controlling for moderate-to-vigorous PA and perceived stress. RESULTS: Independent of average sleep duration and SJL, perceived sleep quality was associated with the HRV outcomes low frequency (LF; B= -10.62 ± 4.85, 95% CI: -20.56, -.67) and high frequency power (HF; B= 10.55 ± 4.84, 95% CI: .61, 20.49). Following control for PA and stress, these relationships remained significant and the association between SJL and LF/HF ratio approached significance (B= -.33 ± .18, 95% CI: -.69, .04). CONCLUSIONS: Our findings suggest that both LF and HF HRV components are related to sleep quality in young adults, highlighting a potential relationship between sleep quality and nighttime autonomic nervous system function.

0542 Exploratory Use of Artificial Intelligence Driven Acoustic Neuromodulation Improved Sleep, Depression, Anxiety, and Stress in Adults with Persisting Post-Concussion Symptoms

Abstract Introduction In prior studies, High-resolution, relational, resonance-based, electroencephalic mirroring (HIRREM®) reduced persisting post-concussion symptoms (PPCS) of insomnia and depression and improved heart rate variability (HRV), but is operator dependent, with difficulty scaling. Cereset Research™ (CR), a noninvasive, closed-loop, artificial intelligence (AI) driven, acoustic neuromodulation technology uses the same core technology, echoing tones linked to brainwaves, but includes updated components, standardized AI driven protocols, software management of designs, and shorter sessions to improve scalability. This open label trial explores use of CR for PPCS. Methods 5 adults (1 female, median age = 48, 31-64) with PPCS received a median of 8 CR sessions (range 7-9, 60 minutes each) over 11 (5-18) days as part of an open label IRB-approved exploratory study of CR for diverse health conditions. Data is collected at baseline (V1), 0-21 days (V2), 4-7 weeks later (V3), and 4-7 weeks thereafter (V4). Pre- and post-CR symptom inventories included concussion (RPQ), insomnia (ISI), depression (CES-D), anxiety (GAD-7), PTSD (PCL-C), and stress (PSS). Primary outcome is change in autonomics at V3 via HRV (SDNN and rMSSD) based on 10-minute BP and HR recordings using a BIOPAC device. Formal analysis of HRV outcome is pending, but we report preliminary changes in symptom outcomes. Results 6 subjects have enrolled for sleep trouble related to PCCS, with 1 lost to follow-up after receiving intervention. For V1-V2 (n=5), median change in RPQ score is -23, ISI -10, CES-D -16, GAD-7 -7, PCL-C -16, and PSS -7. For V1-V3 (n=4), median change in RPQ -19, ISI -10.5, CES-D -6, GAD-7 -4.5, PCL-C -14.5, and PSS -3. No serious adverse events reported. Conclusion Preliminary results suggest similar, clinically meaningful reductions in ISI score, and concussion symptoms, as seen with HIRREM, suggesting promise as a scalable, non-drug intervention for insomnia with PPCS. Updated results will be presented. Support: Support Research grant received from, The Susanne Marcus Collins Foundation, Inc.

Investigating high- and low-frequency neuro-cardiac-guided TMS for probing the frontal vagal pathway

BackgroundInvestigating approaches for determining a functionally meaningful dorsolateral prefrontal cortex (DLPFC) stimulation site is imperative for optimising repetitive transcranial magnetic stimulation (rTMS) response rates for treatment-resistant depression. One proposed approach is neuro-cardiac-guided rTMS (NCG-TMS) in which high frequency rTMS is applied to the DLPFC to determine the site of greatest heart rate deceleration. This site is thought to index a frontal-vagal autonomic pathway that intersects a key pathway believed to underlie rTMS response. ObjectiveWe aimed to independently replicate previous findings of high-frequency NCG-TMS and extend it to evaluate the use of low-frequency rTMS for NCG-TMS. MethodsTwenty healthy participants (13 female; aged 38.6 ± 13.9) underwent NCG-TMS on frontal, fronto-central (active) and central (control) sites. For high-frequency NCG-TMS, three 5 s trains of 10 Hz were provided at each left hemisphere site. For low-frequency NCG-TMS, 60 s trains of 1 Hz were applied to left and right hemispheres and heart rate and heart rate variability outcome measures were analysed. ResultsFor high-frequency NCG-TMS, heart rate deceleration was observed at the left frontal compared with the central site. For low-frequency NCG-TMS, accelerated heart rate was found at the right frontal compared with central sites. No other site differences were observed. ConclusionOpposite patterns of heart rate activity were found for high- and low-frequency NCG-TMS. The high-frequency NCG-TMS data replicate previous findings and support further investigations on the clinical utility of NCG-TMS for optimising rTMS site localisation. Further work assessing the value of low-frequency NCG-TMS for rTMS site localisation is warranted.

Recovery of Heart Rate Variability After Exercise Under Hot Conditions: The Effect of Relative Humidity

The aim of this study was to analyze changes in heart rate variability (HRV) during exercise in hot environments and recovery to baseline values depending on relative humidity. Ten recreational runners participated in this study. Each participant performed 2 trials consisting of 30 min of continuous running under hot and dry (HD) (38°C and 28% relative humidity) and hot and humid (HH) conditions (38°C and 64% relative humidity) at their common 10 km race-running rhythm. HRV and body mass were assessed pre- and post-trial; the rating of perceived exertion and HRV were assessed during the trial; and HRV measurements were repeated 2, 4, 8, and 24 h postexercise. Primary HRV outcomes were root mean square of the successive differences, high frequency power, stress score, and sympathetic/parasympathetic ratio. One-way analysis of variance testing was used to analyze differences. No significant difference in body mass occurred across the different conditions or distances covered (P>0.05). Rating of perceived exertion presented the highest correlation values with stress score (r=0.729 for HD; r=0.568 for HH) and sympathetic/parasympathetic ratio (r=0.621 for HD; r=0.519 for HH) during exercise. HRV recovered to baseline values more quickly after exercising under dry conditions (4 h) than under humid conditions (between 8 and 24 h). Stress score and sympathetic/parasympathetic ratio seem to be the best HRV predictors of internal load. Although there are no differences in HRV during recovery at the same time points in both conditions, the recovery is slower after exercise in HH than in HD.

Associations of depression severity with heart rate and heart rate variability in young adults across normative and clinical populations

Limitations of current depression treatments may arise from a lack of knowledge about unique psychophysiological processes that contribute to depression across the full range of presentations. This study examined how individual variations in heart rate (HR) and heart rate variability (HRV) are related to depressive symptoms across normative and clinical populations in 152 young adults (aged 18–35 years). Moderating effects of sex and antidepressant medication status were considered. Electrocardiogram data were collected during “vanilla” baseline and in response to positive and negative emotional cues. Linear regressions and repeated-measures mixed models were used to assess the relationships between Beck Depression Inventory-II (BDI-II) scores, sex, antidepressant use, and cardiovascular outcomes. Baseline models yielded significant main effects of BDI-II and sex on HR and significant interactions between antidepressant medication status and BDI-II on HRV outcomes. The main effects of BDI-II and sex on HR were no longer significant after controlling for cardiorespiratory fitness. Participants who denied current antidepressant use (n = 137) exhibited a negative association and participants who endorsed current antidepressant (n = 15) use exhibited a positive association between BDI-II scores and HRV. Emotional reactivity models were largely non-significant with the exception of a significant main effect of antidepressant medication status on high-frequency HRV reactivity. Results indicated antidepressant medication use may moderate the relationship between depression severity and cardiovascular functioning, but this requires replication given the modest proportion of medicated individuals in this study. Overall, findings suggest cardiovascular processes and cardiorespiratory fitness are linked to depression symptomatology and may be important to consider in depression treatment.