Repeatability of heart rate variability measures

Cardiac vagal activity changes moderated the association of cognitive and cerebral hemodynamic variations in the prefrontal cortex

Phasic cardiac vagal activity (CVA), reflecting ongoing, moment-to-moment psychophysiological adaptations to environmental changes, can serve as a predictor of individual difference in executive function, particularly executive performance. However, the relationship between phasic CVA and executive function demands requires further validation because of previous inconsistent findings. Moreover, it remains unclear what types of phasic changes of CVA may be adaptive in response to heightened executive demands. This study used the standard N-back task to induce different levels of working memory (WM) load and combined functional Near-Infrared Spectroscopy (fNIRS) with a multipurpose polygraph to investigate the variations of CVA and its interactions with cognitive and prefrontal responses as executive demands increased in fifty-two healthy young subjects. Our results showed phasic decreases in CVA as WM load increased (t (51) = -3.758, p < 0.001, Cohen's d = 0.526). Furthermore, phasic changes of CVA elicited by increased executive demands moderated the association of cognitive and cerebral hemodynamic variations in the prefrontal cortex (B = 0.038, SE = 0.014, p < 0.05). Specifically, as executive demands increased, individuals with larger phasic CVA withdrawal showed a positive relationship between cognitive and hemodynamic variations in the prefrontal cortex (β = 0.281, p = 0.031). No such significant relationship was observed in individuals with smaller phasic CVA withdrawal. The current findings demonstrate a decrease in CVA with increasing executive demands and provide empirical support for the notion that a larger phasic CVA withdrawal can be considered adaptive in situations requiring high executive function demands.

Long-term association of ultra-short heart rate variability with cardiovascular events

Heart rate variability (HRV) is a cardiac autonomic marker with predictive value in cardiac patients. Ultra-short HRV (usHRV) can be measured at scale using standard and wearable ECGs, but its association with cardiovascular events in the general population is undetermined. We aimed to validate usHRV measured using ≤ 15-s ECGs (using RMSSD, SDSD and PHF indices) and investigate its association with atrial fibrillation, major adverse cardiac events, stroke and mortality in individuals without cardiovascular disease. In the National Survey for Health and Development (n = 1337 participants), agreement between 15-s and 6-min HRV, assessed with correlation analysis and Bland-Altman plots, was very good for RMSSD and SDSD and good for PHF. In the UK Biobank (n = 51,628 participants, 64% male, median age 58), after a median follow-up of 11.5 (11.4-11.7) years, incidence of outcomes ranged between 1.7% and 4.3%. Non-linear Cox regression analysis showed that reduced usHRV from 15-, 10- and 5-s ECGs was associated with all outcomes. Individuals with low usHRV (< 20th percentile) had hazard ratios for outcomes between 1.16 and 1.29, p < 0.05, with respect to the reference group. In conclusion, usHRV from ≤ 15-s ECGs correlates with standard short-term HRV and predicts increased risk of cardiovascular events in a large population-representative cohort.

Heart rate variability and risk of agitation in Alzheimer's disease: the Atherosclerosis Risk in Communities Study

Agitation in Alzheimer's disease is common and may be related to impaired emotion regulation capacity. Heart rate variability, a proposed index of autonomic and emotion regulation neural network integrity, could be associated with agitation propensity in Alzheimer's disease. We used the Atherosclerosis Risk in Communities Study cohort data, collected over seven visits spanning over two decades, to investigate whether heart rate variability (change) was associated with agitation risk in individuals clinically diagnosed with dementia due to Alzheimer's disease. Agitation (absence/presence) at Visit 5, the primary outcome, was based on the Neuropsychiatric Inventory agitation/aggression subscale, or a composite score comprising the total number of agitation/aggression, irritability, disinhibition and aberrant motor behaviour subscales present. Visit 1-5 heart rate variability measures were the log-transformed root mean square of successive differences in R-R intervals and standard deviation of normal-to-normal R-R intervals obtained from resting, supine, standard 12-lead ECGs. To aid interpretability, heart rate variability data were scaled such that model outputs were expressed for each 0.05 log-unit change in heart rate variability (which approximated to the observed difference in heart rate variability with every 5 years of age). Among 456 participants who had dementia, 120 were clinically classified to have dementia solely attributable to Alzheimer's disease. This group showed a positive relationship between heart rate variability and agitation risk in regression models, which was strongest for measures of (potentially vagally mediated) heart rate variability change over the preceding two decades. Here, a 0.05 log-unit of heart rate variability change was associated with an up to 10-fold increase in the odds of agitation and around a half-unit increase in the composite agitation score. Associations persisted after controlling for participants' cognitive status, heart rate (change), sociodemographic factors, co-morbidities and medications with autonomic effects. Further confirmatory studies, incorporating measures of emotion regulation, are needed to support heart rate variability indices as potential agitation propensity markers in Alzheimer's disease and to explore underlying mechanisms as targets for treatment development.

The autonomic and nociceptive response to acute experimental stress is impaired in people with knee osteoarthritis: A preliminary study

Objective

Alterations in autonomic function are evident in some chronic pain conditions but have not been thoroughly examined in people with osteoarthritis (OA). The study aimed to examine resting autonomic nervous system (ANS) function in people with knee OA, and the response of the autonomic and nociceptive systems to acute stress.

Methods

A preliminary cross-sectional study was undertaken involving people with knee OA (n = 14), fibromyalgia (n = 13), and pain-free controls (n = 15). The sympathetic and parasympathetic components of the ANS were assessed through measures of pre-ejection period (PEP), skin conductance level (SCL), and high frequency heart rate variability (HF HRV). The nociceptive system was assessed through pain ratings associated with a tonic heat pain stimulus. In separate sessions, ANS and heat pain measures were assessed at rest and in response to nociceptive and mental arithmetic stressors.

Results

The knee OA group showed reduced HF HRV at rest and reduced modulation in response to stress. Resting PEP and SCL were normal in the knee OA group but PEP modulation was impaired in both chronic pain groups during nociceptive stress. The expected reduction in tonic heat pain ratings in response to stress was lacking in the knee OA and FM groups.

Conclusion

Preliminary evidence shows impaired parasympathetic nervous system function at rest and in response to nociceptive and mental stress in people with knee OA, with some evidence of altered sympathetic nervous system function. Impaired ANS function could contribute to ongoing pain experienced, and interventions that target ANS function could be beneficial.

Clinical applications of contactless photoplethysmography for monitoring in adults: A systematic review and meta-analysis

Contactless photoplethysmography (cPPG) is a method of physiological monitoring. It differs from conventional monitoring methods (e.g., saturation probe) by ensuring no contact with the subject by use of a camera. The majority of research on cPPG is conducted in a laboratory setting or in healthy populations. This review aims to evaluate the current literature on monitoring using cPPG in adults within a clinical setting. Adhering to the Preferred Items for Systematic Reviews and Meta-analysis (PRISMA, 2020) guidelines, OVID, Webofscience, Cochrane library, and clinicaltrials.org were systematically searched by two researchers. Research articles using cPPG for monitoring purposes in adults within a clinical setting were selected. Twelve studies with a total of 654 individuals were included. Heart rate (HR) was the most investigated vital sign (n = 8) followed by respiratory rate ((n = 2), Sp02 (n = 2), and HR variability (n = 2). Four studies were included in a meta-analysis of HR compared to ECG data which demonstrated a mean bias of -0.13 (95% CI, -1.22-0.96). This study demonstrates cPPG can be a useful tool in the remote monitoring of patients and has demonstrated accuracy for HR. However, further research is needed into the clinical applications of this method.

Evaluating heart rate variability with 10 second multichannel electrocardiograms in a large population-based sample

Introduction

Heart rate variability (HRV), defined as the variability of consecutive heart beats, is an important biomarker for dysregulations of the autonomic nervous system (ANS) and is associated with the development, course, and outcome of a variety of mental and physical health problems. While guidelines recommend using 5 min electrocardiograms (ECG), recent studies showed that 10 s might be sufficient for deriving vagal-mediated HRV. However, the validity and applicability of this approach for risk prediction in epidemiological studies is currently unclear to be used.

Methods

This study evaluates vagal-mediated HRV with ultra-short HRV (usHRV) based on 10 s multichannel ECG recordings of N = 4,245 and N = 2,392 participants of the Study of Health in Pomerania (SHIP) from two waves of the SHIP-TREND cohort, additionally divided into a healthy and health-impaired subgroup. Association of usHRV with HRV derived from long-term ECG recordings (polysomnography: 5 min before falling asleep [N = 1,041]; orthostatic testing: 5 min of rest before probing an orthostatic reaction [N = 1,676]) and their validity with respect to demographic variables and depressive symptoms were investigated.

Results

High correlations (r = .52-.75) were revealed between usHRV and HRV. While controlling for covariates, usHRV was the strongest predictor for HRV. Furthermore, the associations of usHRV and HRV with age, sex, obesity, and depressive symptoms were similar.

Conclusion

This study provides evidence that usHRV derived from 10 s ECG might function as a proxy of vagal-mediated HRV with similar characteristics. This allows the investigation of ANS dysregulation with ECGs that are routinely performed in epidemiological studies to identify protective and risk factors for various mental and physical health problems.

The Validity of Ultra-Short-Term Heart Rate Variability during Cycling Exercise

Ultra-short-term heart rate variability (HRV) has been validated in the resting state, but its validity during exercise is unclear. This study aimed to examine the validity in ultra-short-term HRV during exercise considering the different exercise intensities. HRVs of twenty-nine healthy adults were measured during incremental cycle exercise tests. HRV parameters (Time-, frequency-domain and non-linear) corresponding to each of the 20% (low), 50% (moderate), and 80% (high) peak oxygen uptakes were compared between the different time segments of HRV analysis (180 s (sec) segment vs. 30, 60, 90, and 120-sec segments). Overall, the differences (bias) between ultra-short-term HRVs increased as the time segment became shorter. In moderate- and high-intensity exercises, the differences in ultra-short-term HRV were more significant than in low intensity exercise. Thus, we discovered that the validity of ultra-short-term HRV differed with the duration of the time segment and exercise intensities. However, the ultra-short-term HRV is feasible in the cycling exercise, and we determined some optimal time duration for HRV analysis for across exercise intensities during the incremental cycling exercise.

Feasibility of the virtual reality-based assessments in patients with panic disorder

Introduction

Recurrences and diagnostic instability of panic disorder (PD) are common and have a negative effect on its long-term course. Developing a novel assessment tool for anxiety that can be used in a multimodal approach may improve these problems in panic disorder patients. This study assessed the feasibility of virtual reality-based assessment in panic disorder (VRA-PD).

Methods

Twenty-five patients with PD (ANX group) and 28 healthy adults (CON group) participated in the study. VRA-PD consisted of four modules based on the key components of cognitive behavior therapy for an anxiety disorder: "Baseline evaluation module" (M0), "Daily environment exposure module" (M1), "Relaxation module" (M2), and "Interoceptive exposure module" (M3). Multiple evaluations, including self-rating anxiety scores (AS) and physiological responses [heart rate variability (HRV) index], were performed in three steps at M1, M2, and M3, and once at M0. Comparisons between patients with PD and healthy controls, factor analysis of variables in VRA-PD, changes in responses within modules, and correlation analysis between variables in VRA-PD and anxiety symptoms assessed by psychological scales were performed.

Results

All participants completed the VRA-PD without discontinuation. The ANX group reported significantly higher AS for all steps and a smaller HRV index in M1 (steps 1 and 2) and M2 (step 1). Repeated-measures analysis of covariance (ANCOVA) revealed significant interaction effects for AS in M1 (F = 4.09, p = 0.02) and M2 (F = 4.20, p = 0.02), and HRV index in M2 (F = 16.22, p < 0.001) and M3 (F = 21.22, p = 0.02). The HRV index only indicated a good model fit for the three-factor model, reflecting the construct of the VRA-PD. Both AS and HRV indexes were significantly correlated with anxiety and depression symptoms.

Discussion

The current study provides preliminary evidence that the VRA-PD could be a valid anxiety behavior assessment tool.

Decreased Heart Rate Variability in COVID-19

Purpose

Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), which primarily infects the lower airways and binds to angiotensin-converting enzyme 2 (ACE2) on alveolar epithelial cells. ACE2 is widely expressed not only in the lungs but also in the cardiovascular system. Therefore, SARS-CoV-2 can also damage the myocardium. This report aimed to highlight decreased heart rate variability (HRV) and cardiac injury caused by SARS-CoV-2.

Materials and Methods

We evaluated three COVID-19 patients who died. Patients' data were collected from electronic medical records. We collected patient's information, including baseline information, lab results, body temperature, heart rate (HR), clinical outcome and other related data. We calculated the HRV and the difference between the expected and actual heart rate changes as the body temperature increased.

Results

As of March 14, 2020, 3 (2.2%) of 136 patients with COVID-19 in Tianjin died in the early stage of the COVID-19 epidemic. The immediate cause of death for Case 1, Case 2, and Case 3 was cardiogenic shock, cardiac arrest and cardiac arrest, respectively. The HRV were substantially decreased in the whole course of all three cases. The actual increases in heart rate were 5 beats/min, 13 beats/min, and 4 beats/min, respectively, less than expected as their temperature increased. Troponin I and Creatine Kinase MB isoenzyme (CK-MB) were substantially increased only in Case 3, for whom the diagnosis of virus-related cardiac injury could not be made until day 7. In all three cases, decreased in HRV and HR changes occurred earlier than increases in cardiac biomarkers (e.g., troponin I and CK-MB).

Conclusions

In conclusion, COVID-19 could affect HRV and counteract tachycardia in response to increases in body temperature. The decreases of HRV and HR changes happened earlier than the increases of myocardial markers (troponin I and CK-MB). It suggested the decreases of HRV and HR changes might help predict cardiac injury earlier than myocardial markers in COVID-19, thus its early identification might help improve patient prognosis.

Supplementary Information

The online version contains supplementary material available at 10.1007/s44231-022-00024-1.

Heart rate variability and the risk of heart failure and its subtypes in post-menopausal women: The Women's Health Initiative study

Background

Low heart rate variability (HRV), a measure of autonomic imbalance, is associated with increased risk of coronary heart disease (CHD) and heart failure (HF). However, its relationship with HF subtypes; heart failure with preserved ejection fraction (HFpEF) and heart failure with reduced ejection fraction (HFrEF) has not been studied prior.

Methods and findings

We conducted a longitudinal study in Women’s Health Initiative study cohort to investigate the association of baseline quartiles of resting heart rate (rHR) and HRV measures; SDNN (SD of normal-to-normal RR interval) and RMSSD (root mean square of successive difference of RR interval) measured by twelve-lead electrocardiogram (ECG) on enrollment, with the risk of hospitalized HF and its subtypes. Total of 28,603 post-menopausal women, predominantly non-Hispanic whites (69%), with a mean (SD) age of 62.6 (7.1) years, free of baseline CHD and HF were included. In a fully adjusted cox-proportional hazards regression model which adjusted for age, race, BMI, alcohol intake, education, physical activity, hyperlipidemia, hypertension, left ventricular hypertrophy, use of beta-blocker, calcium-channel blocker, hormone therapy, and time-varying incident CHD, the hazard ratios of lowest quartile of HRV (Q1) with HF risk were significant (Q1 SDNN compared to Q4 SDNN: 1.22, 95% CI 1.07, 1.39; Q1 RMSSD compared to Q4 RMSSD: 1.17, 95% CI 1.02, 1.33). On subgroup analysis of HF subtypes, low HRV was associated with elevated HFpEF risk (Q1 vs Q4 SDNN: 1.22, 95% CI 1.02, 1.47) but not with HFrEF (Q1 vs Q4 SDNN: 1.19, 95% CI 0.95, 1.50; Q1 RMSSD: 1.13, 95% CI 0.90, 1.43).

Conclusion

Low HRV is associated with elevated overall hospitalized HF risk and HFpEF risk in post-menopausal women. Whether interventions to increase HRV through healthy lifestyle changes will decrease HF risk warrants further investigation.

Psychophysiological Stress Reactivity in Monozygotic Twins with and without Takotsubo Syndrome

Objective: Takotsubo syndrome (TTS) is characterized by transient left ventricular dysfunction, often elevated myocardial enzymes, and electrocardiographic changes. Previous studies suggested that an overstimulation of the sympathetic nervous system might cause TTS. However, the pathogenesis of TTS is largely unknown. Therefore, we investigated physiological stress reactivity with a standardized stress test in monozygotic twin sisters, only one of whom had experienced TTS. Methods: The 60-year-old Caucasian monozygotic twins, one with and one without a previous episode of TTS, were recruited in the Department of Cardiology at the University Hospital Zurich, Switzerland. We applied the Trier Social Stress Test (TSST) to investigate stress reactivity six weeks after the TTS. Hemodynamic measures (heart rate (HR), blood pressure (BP)), heart rate variability (HRV), plasma norepinephrine and epinephrine and salivary cortisol levels were collected immediately before and after the TSST, and 15, 45, and 90 min after TSST. The monozygotic twins differed in their hemodynamic stress response with the TTS twin showing blunted HR and BP reactivity and vagal withdrawal beyond the acute phase of stress. In contrast, the TTS twin showed a higher catecholamine and cortisol stress response with a steady increase in norepinephrine during the recovery period from stress compared to her non-TTS twin sister. Conclusion: Large studies applying a case-control design are needed to confirm blunted hemodynamic reactivity, increased catecholamine reactivity, vagal withdrawal, and increased cortisol reactivity to stress in TTS. This may advance the knowledge of psychophysiological mechanisms in TTS.

Different exercise training modalities similarly improve heart rate variability in sedentary middle-aged adults: the FIT-AGEING randomized controlled trial

PURPOSE

This study aimed to investigate the influence of different exercise training modalities on heart rate variability (HRV) in sedentary middle-aged adults; and to study whether changes in health-related outcomes (i.e., body composition and cardiometabolic risk) are associated with those hypothetical HRV changes in sedentary middle-aged adults.

METHODS

A total of 66 middle-aged adults (53.6 ± 4.4 years old; 50% women) were enrolled in the FIT-AGEING study. We conducted a 12-week randomized controlled trial. The participants were randomly assigned to 4 groups: (a) a control group (no exercise); (b) a physical activity recommendation from the World Health Organization group (PAR); (c) a high-intensity interval training group (HIIT); and (d) a high-intensity interval training group adding whole-body electromyostimulation (HIIT + EMS).

RESULTS

All exercise training modalities induced changes in HRV parameters (all P ≤ 0.001) without statistical differences between them (all P > 0.05). We found associations between changes in body composition and cardiometabolic risk and exercise-related changes in HRV.

CONCLUSION

Our results suggest that different exercise interventions (i.e., PAR, HIIT and HIIT + EMS) induced an enhancement of HRV in sedentary middle-aged adults. Our findings support the notion that exercise-related changes in HRV are associated with changes in body composition and cardiometabolic risk after the intervention program CLINICAL TRIAL REGISTRY: NCT03334357 (ClinicalTrials.gov). November 7, 2017 retrospectively registered.

Sex differences in autonomic recovery following repeated sinusoidal resistance exercise

A simple bodyweight squat is sufficient to cause substantial stress on the autonomic nervous system (ANS) via ~30-50 mmHg blood pressure (BP) oscillations. However, it is unknown to the extent of the ANS is impacted during and immediately following bodyweight and resistance squat-stand maneuvers (SSM) while considering chromosomal sex. Thirteen females and twelve males performed four, 5-minute bouts of squat-stand maneuvers (SSM); two at 0.05 Hz (10-second squat/10-second stand) and two at 0.10 Hz (5-s squat/5-s stand). The SSM were performed using bodyweight resistance and additional external resistance (~20% of bodyweight). Five-minutes of quiet-sitting and quiet-standing were completed immediately following both bodyweight and resistance squats. Heart rate variability (HRV) and baroreceptor sensitivity metrics were extracted from beat-to-beat electrocardiography and systemic BP recordings. Repeated measure Analysis of Variance with generalized eta-squared effect sizes assessed differences between SSM task type and chromosomal sex on ANS metrics. Despite added resistance eliciting greater elevations in blood pressure, no differences in ANS function were noted during competition and recovery between SSM tasks (all p > 0.050; negligible/small effect sizes). During recovery, females had an elevated heart rate (p = 0.017; small effect size), greater time-domain HRV measures (p < 0.047; small effect size), greater high-frequency domain HRV measures (p = 0.002; moderate effect size), and reduced low-frequency domain HRV measures (p = 0.002; moderate effect size). A healthy ANS can modulate repetitive cardiovascular stressors via squat-stand maneuvers in a harmonious manner irrespective of added low-level resistance. Females were more parasympathetically driven following low-level resistance exercise/stress, which may be a cardioprotective trait.

Co-ordination of brain and heart oscillations during non-rapid eye movement sleep

Oscillatory activities of the brain and heart show a strong variation across wakefulness and sleep. Separate lines of research indicate that non‐rapid eye movement (NREM) sleep is characterised by electroencephalographic slow oscillations (SO), sleep spindles, and phase–amplitude coupling of these oscillations (SO–spindle coupling), as well as an increase in high‐frequency heart rate variability (HF‐HRV), reflecting enhanced parasympathetic activity. The present study aimed to investigate further the potential coordination between brain and heart oscillations during NREM sleep. Data were derived from one sleep laboratory night with polysomnographic monitoring in 45 healthy participants (22 male, 23 female; mean age 37 years). The associations between the strength (modulation index [MI]) and phase direction of SO–spindle coupling (circular measure) and HF‐HRV during NREM sleep were investigated using linear modelling. First, a significant SO–spindle coupling (MI) was observed for all participants during NREM sleep, with spindle peaks preferentially occurring during the SO upstate (phase direction). Second, linear model analyses of NREM sleep showed a significant relationship between the MI and HF‐HRV (F = 20.1, r² = 0.30, p < 0.001) and a tentative circular‐linear correlation between phase direction and HF‐HRV (F = 3.07, r² = 0.12, p = 0.056). We demonstrated a co‐ordination between SO–spindle phase–amplitude coupling and HF‐HRV during NREM sleep, presumably related to parallel central nervous and peripheral vegetative arousal systems regulation. Further investigating the fine‐graded co‐ordination of brain and heart oscillations might improve our understanding of the links between sleep and cardiovascular health.

Epigenetically mediated electrocardiographic manifestations of sub-chronic exposures to ambient particulate matter air pollution in the Women's Health Initiative and Atherosclerosis Risk in Communities Study

BACKGROUND

Short-duration exposure to ambient particulate matter (PM) air pollution is associated with cardiac autonomic dysfunction and prolonged ventricular repolarization. However, associations with sub-chronic exposures to coarser particulates are relatively poorly characterized as are molecular mechanisms underlying their potential relationships with cardiovascular disease.

MATERIALS AND METHODS

We estimated associations between monthly mean concentrations of PM < 10 μm and 2.5-10 μm in diameter (PM10; PM2.5-10) with time-domain measures of heart rate variability (HRV) and QT interval duration (QT) among U.S. women and men in the Women's Health Initiative and Atherosclerosis Risk in Communities Study (nHRV = 82,107; nQT = 76,711). Then we examined mediation of the PM-HRV and PM-QT associations by DNA methylation (DNAm) at three Cytosine-phosphate-Guanine (CpG) sites (cg19004594, cg24102420, cg12124767) with known sensitivity to monthly mean PM concentrations in a subset of the participants (nHRV = 7,169; nQT = 6,895). After multiply imputing missing PM, electrocardiographic and covariable data, we estimated associations using attrition-weighted, linear, mixed, longitudinal models adjusting for sociodemographic, behavioral, meteorological, and clinical characteristics. We assessed mediation by estimating the proportions of PM-HRV and PM-QT associations mediated by DNAm.

RESULTS

We found little evidence of PM-HRV association, PM-QT association, or mediation by DNAm.

CONCLUSIONS

The findings suggest that among racially/ethnically and environmentally diverse U.S. populations, sub-chronic exposures to coarser particulates may not exert appreciable, epigenetically mediated effects on cardiac autonomic function or ventricular repolarization. Further investigation in better-powered studies is warranted, with additional focus on shorter duration exposures to finer particulates and non-electrocardiographic outcomes among relatively susceptible populations.

Heart Rate Variability in Psychology: A Review of HRV Indices and an Analysis Tutorial

The use of heart rate variability (HRV) in research has been greatly popularized over the past decades due to the ease and affordability of HRV collection, coupled with its clinical relevance and significant relationships with psychophysiological constructs and psychopathological disorders. Despite the wide use of electrocardiograms (ECG) in research and advancements in sensor technology, the analytical approach and steps applied to obtain HRV measures can be seen as complex. Thus, this poses a challenge to users who may not have the adequate background knowledge to obtain the HRV indices reliably. To maximize the impact of HRV-related research and its reproducibility, parallel advances in users' understanding of the indices and the standardization of analysis pipelines in its utility will be crucial. This paper addresses this gap and aims to provide an overview of the most up-to-date and commonly used HRV indices, as well as common research areas in which these indices have proven to be very useful, particularly in psychology. In addition, we also provide a step-by-step guide on how to perform HRV analysis using an integrative neurophysiological toolkit, NeuroKit2.

The validity and reliability of ultra-short-term heart rate variability parameters and the influence of physiological covariates

Ultra-short-term (UST) heart rate variability (HRV) metrics have increasingly been proposed as surrogates for short-term HRV metrics. However, the concurrent validity, within-day reliability, and between-day reliability of UST HRV have yet to be comprehensively documented. Thirty-six adults (18 males, age: 26 ± 5 yr, BMI: 24 ± 3 kg/m²) were recruited. Measures of HRV were quantified in a quiet-stance upright orthostatic position via three-lead electrocardiogram (ADInstruments, FE232 BioAmp). All short-term data recordings were 300 s in length and five UST time points (i.e., 30 s, 60 s, 120 s, 180 s, and 240 s) were extracted from the original 300-s recording. Bland-Altman plots with 95% limits of agreement, repeated measures ANOVA and two-tailed paired t tests demarcated differences between UST and short-term recordings. Linear regressions, coefficient of variation, intraclass correlation coefficients, and other tests examined the validity and reliability in both time- and frequency domains. No group differences were noted between all short-term and UST measures, for either time- (all P > 0.202) or frequency-domain metrics (all P > 0.086). A longer recording duration was associated with augmented validity and reliability, which was less impacted by confounding influences from physiological variables (e.g., respiration rate, carbon dioxide end-tidals, and blood pressure). Conclusively, heart rate, time-domain, and relative frequency-domain HRV metrics were acceptable with recordings greater or equal to 60 s, 240 s, and 300 s, respectively. Future studies employing UST HRV metrics should thoroughly understand the methodological requirements to obtain accurate results. Moreover, a conservative approach should be utilized regarding the minimum acceptable recording duration, which ensures valid/reliable HRV estimates are obtained.NEW & NOTEWORTHY A one size fits all methodological approach to quantify HRV metrics appears to be inappropriate, where study design considerations need to be conducted upon a variable-by-variable basis. The present results found 60 s (heart rate), 240 s (time-domain parameters), and 300 s (relative frequency-domain parameters) were required to obtain accurate and reproducible metrics. The lower validity/reliability of the ultra-short-term metrics was attributable to measurement error and/or confounding from extraneous physiological influences (i.e., respiratory and hemodynamic variables).

Optimal Length of Heart Rate Variability Data and Forecasting Time for Ventricular Fibrillation Prediction Using Machine Learning

Ventricular fibrillation (VF) is a cardiovascular disease that is one of the major causes of mortality worldwide, according to the World Health Organization. Heart rate variability (HRV) is a biomarker that is used for detecting and predicting life-threatening arrhythmias. Predicting the occurrence of VF in advance is important for saving patients from sudden death. We extracted features from seven HRV data lengths to predict the onset of VF before nine different forecast times and observed the prediction accuracies. By using only five features, an artificial neural network classifier was trained and validated based on 10-fold cross-validation. Maximum prediction accuracies of 88.18% and 88.64% were observed at HRV data lengths of 10 and 20 s, respectively, at a forecast time of 0 s. The worst prediction accuracy was recorded at an HRV data length of 70 s and a forecast time of 80 s. Our results showed that features extracted from HRV signals near the VF onset could yield relatively high VF prediction accuracies.

Short-term repeatability of the peguero-lo presti electrocardiographic left ventricular hypertrophy criteria

Background

Electrocardiographic left ventricular hypertrophy (ECG‐LVH) represents preclinical cardiovascular disease and predicts cardiovascular disease morbidity and mortality. While the newly developed Peguero‐Lo Presti ECG‐LVH criteria have greater sensitivity for LVH than the Cornell voltage and Sokolow–Lyon criteria, its short‐term repeatability is unknown. Therefore, we characterized the short‐term repeatability of Peguero‐Lo Presti ECG‐LVH criteria and evaluate its agreement with Cornell voltage and Sokolow–Lyon ECG‐LVH criteria.

Methods

Participants underwent two resting, standard, 12‐lead ECGs at each of two visits one week apart (n = 63). We defined a Peguero‐Lo Presti index as a sum of the deepest S wave amplitude in any single lead and lead V₄ (i.e., S_D + SV₄) and defined Peguero‐Lo Presti LVH index as ≥ 2,300 µV among women and ≥ 2,800 µV among men. We estimated repeatability as an intraclass correlation coefficient (ICC), agreement as a prevalence‐adjusted bias‐adjusted kappa coefficient (κ), and precision using 95% confidence intervals (CIs).

Results

The Peguero‐Lo Presti index was repeatable: ICC (95% CI) = 0.94 (0.91–0.97). Within‐visit agreement of Peguero‐Lo Presti LVH was high at the first and second visits: κ (95% CI) = 0.97 (0.91–1.00) and 1.00 (1.00–1.00). Between‐visit agreement of the first and second measurements at each visit was comparable: κ (95% CI) = 0.90 (0.80–1.00) and 0.93 (0.85–1.00). Agreement of Peguero‐Lo Presti and Cornell or Sokolow–Lyon LVH on any one of the four ECGs was slightly lower: κ (95% CI) = 0.71 (0.54–0.89).

Conclusion

The Peguero‐Lo Presti index and LVH have excellent repeatability and agreement, which support their use in clinical and epidemiological studies.

Paradoxical effect of cumulative stress exposure on information processing speed in Hispanics/Latinos with elevated heart rate variability

Chronic stress has a deleterious effect on prefrontal lobe functioning. Empirical evidence suggests elevated vagal tone, indexed by elevated heart rate variability (HRV), mitigates the effect of mental stress on frontal lobe function. Here, the mitigating effect of HRV on stress-related decrements in cognitive performance is assessed based on information processing speed (DSST), word fluency and verbal learning task performance. Artifact free electrocardiogram (ECG) data was analyzed from 1420 Hispanic/Latino adults from the Sociocultural Ancillary of the Hispanic Community Health Study/Study of Latinos (HCHS/SOL). A 12-lead ECG was used to collect short-term recordings of the root mean square of successive differences in all normal R-peak to R-peak intervals (RMSSD) and the change between adjacent beats and the standard deviation of those intervals (SDNN) as indices of total HRV. As predicted, an interaction emerged for HRV and stress on the task presumed to require the greatest prefrontal lobe involvement, i.e., the DSST. After accounting for sociodemographic factors, chronic stress was associated with better DSST performance amongst individuals at higher quartile of SDNN, but not RMSSD. The paradoxical effect for greater stress exposure on DSST performance may in part be explained by increased speed of information processing and decision making often reported in high-stress cohorts. The nature of this interaction highlights the importance of examining the relationship between stress and cognition across a spectrum of vagal tone.

Association of Psychosocial Factors With Short-Term Resting Heart Rate Variability: The Atherosclerosis Risk in Communities Study

Background Psychosocial factors predict heart disease risk, but our understanding of underlying mechanisms is limited. We sought to evaluate the physiologic correlates of psychosocial factors by measuring their relationships with heart rate variability (HRV), a measure of autonomic health, in the ARIC (Atherosclerosis Risk in Communities) study. We hypothesize that increased psychosocial stress associates with lower HRV. Methods and Results We studied 9331 participants in ARIC with short-term HRV data at visits 2 and 4. The mean (SD) age was 54.4 (5.7) years, 55% were women, and 25% were Black. Psychosocial factors included: (1) vital exhaustion (VE), (2) anger proneness, a personality trait, and (3) perceived social support. Linear models adjusted for sociodemographic and cardiovascular risk factors. Low frequency HRV (ln ms2) was significantly lower in the highest versus lowest quartiles of VE (B=-0.14, 95% CI, -0.24 to -0.05). When comparing this effect to age (B=-0.04, 95% CI, -0.05 to -0.04), the difference was equivalent to 3.8 years of accelerated aging. Perceived social support associated with lower time-domain HRV. High VE (versus low VE) also associated with greater decreases in low frequency over time, and both anger and VE associated with greater increases in resting heart rate over time. Survival analyses were performed with Cox models, and no evidence was found that HRV explains the excess risk found with high VE and low perceived social support. Conclusions Vital exhaustion, and to a lesser extent anger and social support, were associated with worse autonomic function and greater adverse changes over time.

A Critical Review of Ultra-Short-Term Heart Rate Variability Norms Research

Heart rate variability (HRV) is the fluctuation in time between successive heartbeats and is defined by interbeat intervals. Researchers have shown that short-term (∼5-min) and long-term (≥24-h) HRV measurements are associated with adaptability, health, mobilization, and use of limited regulatory resources, and performance. Long-term HRV recordings predict health outcomes heart attack, stroke, and all-cause mortality. Despite the prognostic value of long-term HRV assessment, it has not been broadly integrated into mainstream medical care or personal health monitoring. Although short-term HRV measurement does not require ambulatory monitoring and the cost of long-term assessment, it is underutilized in medical care. Among the diverse reasons for the slow adoption of short-term HRV measurement is its prohibitive time cost (∼5 min). Researchers have addressed this issue by investigating the criterion validity of ultra-short-term (UST) HRV measurements of less than 5-min duration compared with short-term recordings. The criterion validity of a method indicates that a novel measurement procedure produces comparable results to a currently validated measurement tool. We evaluated 28 studies that reported UST HRV features with a minimum of 20 participants; of these 17 did not investigate criterion validity and 8 primarily used correlational and/or group difference criteria. The correlational and group difference criteria were insufficient because they did not control for measurement bias. Only three studies used a limits of agreement (LOA) criterion that specified a priori an acceptable difference between novel and validated values in absolute units. Whereas the selection of rigorous criterion validity methods is essential, researchers also need to address such issues as acceptable measurement bias and control of artifacts. UST measurements are proxies of proxies. They seek to replace short-term values which, in turn, attempt to estimate long-term metrics. Further adoption of UST HRV measurements requires compelling evidence that these metrics can forecast real-world health or performance outcomes. Furthermore, a single false heartbeat can dramatically alter HRV metrics. UST measurement solutions must automatically edit artifactual interbeat interval values otherwise HRV measurements will be invalid. These are the formidable challenges that must be addressed before HRV monitoring can be accepted for widespread use in medicine and personal health care.

Descriptive epidemiology of high frequency component based on heart rate variability from 10-second ECG data and daily physical activity among community adult residents: the Nagahama Study

Characteristics of high frequency (HF) component based on heart rate variability (HRV) in a large general population remain unclear, particularly on the relationship with daily physical activity. We aimed to characterize the distribution of HF component and examine the association with daily physical activity among community residents. We performed spectral analysis of HRV from 10-second ECG recordings among 9135 residents aged 30 to 74 years in Nagahama City, Japan. HF components were log-transformed to consider the distribution. Simple correlations between HF and age were determined. Age-adjusted mean values of HF component were calculated for each questionnaire item related to daily physical activity. Multiple regression analysis was performed to examine the effect of daily physical activity on HF component value. Mean values of logarithmically-transformed HF component (lnHF) were higher in women than in men (p < 0.001). lnHF was inversely associated with age (r = -0.40, -0.49 for men, women, respectively). Adjusted mean lnHF for physically active people was significantly higher than that in inactive people (p < 0.001). HF components from 10-second ECG recordings were moderately and negatively correlated with age in both sexes, and positively correlated with daily physical activity in the general adult population. Maintaining the level of daily physical activity, especially to exercise regularly could keep the parasympathetic function high.

Reliability of ultra-short indices for autonomic dysfunction in dyslipidemia

Dyslipidemia is associated with autonomic nervous system (ANS) dysfunction. Heart rate variability (HRV) is a powerful tool for evaluating the ANS and for cardiovascular risk stratification. Yet, the methodologies used are impractical in most clinical settings and therefore, are usually not applied. The current study aimed to evaluate the reliability of ultra-short HRV parameters, which are easily calculated from any standard ECG, as a practical method for ANS study, with a focus on patients with dyslipidemia. Fifty-nine volunteers with dyslipidemia underwent HRV study of parametric and power spectral indices according to accepted methods. Correlations were calculated between ultra-short HRV indices (five 1-min and five 10-s segments) and standard 5-min recordings. Correlations were found between 10-s and 1-min RMSSD and 5-min recordings (mean Pearson ρ correlation coefficients of 0.913 and 0.944, respectively, and mean concordance correlation coefficients of 0.855 and 0.938, respectively). Associations were found between other ultra-short HRV parameters (SDNN, maximum RR, minimum RR, pNN50, ln(RMSSD) and 5-min recordings. In addition, average RR, HRV-TI, NN50, TP, LF/HF, ln(SDNN), ln(HRV-TI), ln(TP) and ln(LF/HF) from 1-min recordings were associated with 5-min values. In conclusion, some ultra-short HRV parameters can be used for ANS evaluation and presumably, for cardiovascular risk stratification among patients with dyslipidemia. These parameters seem to be of great practical value for both inpatient and outpatient settings, because most can be calculated from a standard 10-s ECG strip. The prognostic implications of ECG-derived, ultra-short HRV parameters in patients with dyslipidemia should be further evaluated in future studies.

Reproducibility of 24-h heart rate variability measures in preterm infants born at 28-32 weeks of gestation

AIMS

To determine the reproducibility and minimum detectable change (MDC) of heart rate variability (HRV) measures during two sequential 24-h periods, at week 32 of gestation, in preterm infants born between 28 and 32 weeks, hospitalized in the neonatal intensive care unit (NICU). The second aim is to assess postnatal changes in HRV measures between 32 and 35 weeks.

STUDY DESIGN

32 preterm infants born between 28 and 32 weeks of gestation were recruited. For each infant 48 h of recordings of RR interval were performed at week 32 and week 35. HRV parameters included time and frequency parameters.

RESULTS

At week 32, the intra-class correlation coefficient (ICC) of all HRV values was statistically significant with high correlation coefficients (ICC = 0.83-0.97). At week 35, a significant increase was noted in the HRV parameters, characterize mainly the sympathetic tone, with over half the infants showing an increase greater than the MDC for these parameters.

CONCLUSIONS

Using 24-h recording at week 32 of gestation during NICU routine is reliable, feasible, not costly and may have important implications for an early identification of premature in a state of stress such as sepsis, or as a follow-up measure.

Reliability of short-term measurements of heart rate variability: Findings from a longitudinal study

Research on heart rate variability (HRV) received increasing attention. This study analysed the reliability of the most common HRV parameters for baseline measurements. 103 healthy students (83 women, M = 21.72 ± 3.31 years) participated in five short-term HRV sessions, each including supine, sitting, and standing positions, respectively, spanning a time interval of eleven months. Relative reliability was evaluated by intraclass correlation coefficients, and absolute reliability by standard errors of measurement, smallest real differences, and 95 % limits of random variation. No systematic mean differences between measurements emerged. Intraclass correlation coefficients were quite low (supine: .49-.64, sitting: .40-.57, standing: .35-.56). Absolute reliability indicators revealed pronounced variations between test and retest. Influences of posture and time between measurements on reliability were small and unsystematic. We conclude that such high levels of within-subjects variability in HRV measurements (a) hamper the detection of changes over time, and (b) should be considered carefully in future analyses.

Association of Heart Rate Variability With Cognitive Performance: The Multi-Ethnic Study of Atherosclerosis

Background Heart rate variability (HRV) is associated with vascular risk factors for dementia, but whether HRV is associated with specific domains of cognitive performance is unclear. Methods and Results In the Multi-Ethnic Study of Atherosclerosis (N=3018; mean age 59.3±9.2 years), we assessed the relationship of 10-second HRV to scores on tests of global cognitive performance (Cognitive Abilities Screening Instrument), processing speed (Digit Symbol Coding), and working memory (Digit Span). HRV was computed as the SD of normal-normal intervals (SDNN) and root mean square of successive differences (RMSSD) at Exam 1 (2000-2002) and Exam 5 (2010-2012). Cognitive tests were administered at Exam 5. We report regression coefficients (β [95% CI]) representing cognitive test score change per 2-fold increase in HRV. After adjustment for age, race/ethnicity, sex, education, apolipoprotein E genotype, and cardiovascular risk factors and incident disease, higher Exam 1 (β=0.37 [0.06, 0.67]) and Exam 5 (β=0.31 [0.04, 0.59]) SDNN were associated with better Cognitive Abilities Screening Instrument performance. Higher Exam 1 (β=0.80 [0.17, 1.43]) and Exam 5 (β=0.63 [0.06, 1.20]) SDNN, and Exam 5 RMSSD (β=0.54 [0.01, 1.08]) were associated with better Digit Symbol Coding performance. Finally, higher Exam 5 SDNN was associated with better Digit Span performance (β=0.17 [0.01, 0.33]). Associations were attenuated after adjustment for resting heart rate. Conclusions Higher HRV is generally associated with better cognitive performance in this multi-ethnic cohort of aging adults, and further study of the relationship of autonomic function to cognition is warranted.

Resting heart rate and incidence of venous thromboembolism

BACKGROUND/OBJECTIVES

Higher resting heart rate is a risk factor for arterial cardiovascular diseases. We assessed whether higher heart rate is a risk factor for venous thromboembolism (VTE).

METHODS

In a prospective epidemiologic cohort, the Atherosclerosis Risk in Communities (ARIC) Study, we associated resting heart rate by electrocardiogram with physician-validated incident hospitalized VTE through 2015. We also examined whether lower heart rate variability (HRV), a marker of cardiac autonomic imbalance, might be a risk factor for VTE.

RESULTS

Resting heart rate at Visit 1 (1987-1989), when participants were 45 to 64 years old (mean, 54 years), was not associated with incidence of VTE (n = 882 cases). However, heart rate at Visit 4 (1996-1998; mean age, 63 years) was associated positively with VTE (n = 557 cases). The adjusted hazard ratios (95% confidence intervals) of VTE across Visit 4 heart rate categories of <60, 60 to 69, 70 to 79, and ≥80 bpm were 1 (reference), 1.22 (1.01-1.49), 1.39 (1.09-1.78), and 1.44 (1.01-2.06), respectively, and when evaluated continuously 1.11 (1.02-1.21) per 10 bpm greater heart rate. For the most part, HRV indices were not associated with VTE or associations were explained by inverse correlations of HRV indices with heart rate.

CONCLUSION

We found a significant positive and independent association of resting heart rate at ARIC Visit 4 with incidence of VTE. The reason why high heart rate is a risk marker for VTE warrants further exploration.

Resting Heart Rate, Short-Term Heart Rate Variability and Incident Atrial Fibrillation (from the Multi-Ethnic Study of Atherosclerosis (MESA))

Evidence suggests an association between autonomical nervous system (ANS) function and atrial fibrillation (AF) development. We sought to examine the association of baseline resting heart rate (RHR) and short-term heart rate variability (HRV) as surrogates of (ANS) with incident AF in individuals without previous cardiovascular disease. A total of 6,261 participants of the Multi-Ethnic Study of Atherosclerosis who were free of AF and diagnosed cardiovascular disease were enrolled. Three standard 10-second, 12-lead electrocardiograms (ECG) were used to measure RHR, the standard deviation of normal-to-normal intervals (SDNN) and the root mean square of successive differences in RR intervals (RMSSD). Cox proportional hazards models adjusted for demographics, atrioventricular nodal agents, and known cardiovascular risk factors were used to examine the association of baseline RHR, and log transformed SDNN and RMSDD with incident AF. Over a mean follow-up of 11.3 ± 3.7 years, 754 (12%) participants developed AF. Spline curve analysis revealed a nonlinear association between RHR, HRV, and incident AF. In fully adjusted models higher (but not lower) baseline RHR (RHR >76 beats/min) was associated with incident AF (hazard ratio 1.48 95% confidence interval 1.18 to 1.86). Additionally, lower values of RMSDD and SDNN and higher values of RMSDD were independently associated with incident AF. In conclusion, cardiac ANS dysregulation indicated as higher RHR and lower HRV is associated with incident AF independent of known cardiovascular risk factors.

Short-term repeatability of electrocardiographic criteria of left ventricular hypertrophy

BACKGROUND

Left ventricular hypertrophy (LVH) is a marker of cardiac end-organ damage and a risk factor for cardiovascular morbidity and mortality. Although clinical trials and cohort studies commonly use the electrocardiogram (ECG) for LVH assessment, the repeatability of ECG-LVH criteria has not been sufficiently examined. Therefore, we evaluated the repeatability of ECG-LVH criteria.

METHODS

Participants (n = 63) underwent two standard ECGs at each of two visits, two weeks apart. The ECGs were processed centrally to calculate Cornell voltage (CV) LVH, Cornell voltage product (CVP) LVH, Sokolow-Lyon (SL) LVH, and Sokolow-Lyon product (SLP) LVH. We also used the waveforms measurements contributing to these LVH criteria as continuous variables, referred to here as CV-index, CVP-index, and SL-index. We calculated the intraclass correlation coefficient (ICC), minimal detectable change (95% confidence), and the prevalence-adjusted bias-adjusted kappa (PABAK).

RESULTS

ICCs (95% confidence intervals (CI)) were 0.97 (0.96, 0.98) for CV-index, 0.97 (0.95, 0.98) for CVP-index, and 0.93 (0.90, 0.96) for log of SL-index. Minimal detectable change between repeat measures of CV-index, CVP-index, and log of SL-index were ≥236.7 mV, ≥26.7 mV, and ≥0.09 mV, respectively. The within-visit PABAK was 1 for all ECG-LVH criteria, except for the first visit SLP-LVH (PABAK = 0.93). Between-visit PABAK ranged from 0.83 to 0.97 across LVH criteria.

CONCLUSIONS

CV, CVP, and SL ECG-LVH as continuous variables have excellent repeatability, and as binary variables have excellent within-visit agreement and good between-visit agreement. These results alleviate concerns about the repeatability the ECG-LVH use in clinical trials and epidemiologic studies.

Reliability of ultrashort electrocardiographic indices in hypertension: the quest for a clinically applicable prognostic marker

Heart rate variability (HRV) is an accepted clinical tool for evaluating autonomic nervous system function and a marker of adverse cardiac outcome. Although 5 min long HRV recordings are considered methodologically acceptable, it remains impractical in most clinical settings. Also, while some ultrashort HRV (usHRV) parameters were found useful in healthy individuals, their applicability to patients with cardiovascular risk factors is largely unknown. Therefore, our goal was to evaluate the reliability of ultrashort ECG (usECG) indices for HRV among patients with hypertension. One-hundred and two patients with essential hypertension were included. HRV was recorded for 5 min in strictly monitored settings. HRV parameters from randomly chosen 1 min and 10 s series were analyzed. Excellent correlations were found between 1 min SD of RR interval (SDNN) (intraclass correlation coefficient (ICC) 0.973), 10 s SDNN (ICC 0.92) and 5 min SDNN results. An excellent correlation was also found between 1 min root  mean square of successive differences in RR intervals (RMSSD) (ICC 0.992), 10 s RMSSD (ICC 0.982) and 5 min RMSSD. Logarithmic transformation of ultrashort 1 min HRV-triangular index using the natural logarithm (Ln) also had excellent correlation with 5 min measurements (ICC 0.9). Also, excellent correlations were found between 10 s and 1 min Ln(RMSSD), 10 s Ln(RMSSD) and 5 min measurements. Other HRV parameters measured from 1 min and 10 s periods showed lower correlations. In conclusion, evaluation of SDNN, RMSSD or Ln(RMSSD) from 10 s ECG recordings can be used to estimate autonomic nervous system function in patients with hypertension. These appealing markers can be readily calculated from any standard ECG tracing. The prognostic significance of ultrashort SDNN and ultrashort RMSSD in patients with cardiovascular risk factors needs to be determined in future prospective cohort studies.

Examining reactivity patterns in burnout and other indicators of chronic stress

INTRODUCTION

Burnout symptomatology is associated with various negative health consequences; however, the mechanisms underlying these associations remain unclear. One potential pathway involves alterations in the acute stress response. The aims of the present study were to examine burnout-associated alterations in stress-reactivity patterns, during a standardized social stressor compared to a control condition, as well as to examine whether effects associated with greater burnout symptomatology were distinct from other, conceptually overlapping indicators of chronic stress (i.e. depressive symptomatology and elevated hair cortisol concentration [HCC]).

MATERIALS AND METHODS

In a randomized two-factor design a total of 70 employed males with varying burnout symptoms but without evidence of physical or psychiatric disease were exposed to the Trier Social Stress Test for Groups (TSST-G) or a non-stressful control condition. Acute stress reactivity was assessed using self-report stress measures and non-invasive biomarkers. Associations among acute stress reactivity, burnout and depressive symptoms (assessed with self-report measures), as well as HCC were analysed using repeated measure ANCOVAs and moderation analysis.

RESULTS

Burnout symptomatology was associated with elevated stress perception independent of the experimental condition. In addition, depressive symptomatology was associated with enhanced anticipatory appraisal, whereas HCC was not related to any subjective stress measure. On a physiological level, burnout and depressive symptomatology, as well as HCC were associated with a pattern of blunted cardiovascular reactivity, however the timing of this effect varied.

CONCLUSION

Our results indicate burnout-associated modulations in stress reactivity, which diverge, at least partly, from other indicators of chronic stress.

Effect of asthma and six-months high-intensity interval training on heart rate variability during exercise in adolescents

Little is known regarding the influence of asthma and exercise, and their interaction, on heart rate variability (HRV) in adolescents. Thirty-one adolescents with asthma (13.7±0.9 years; 21.9±3.9 kg·m^-2; 19 boys, 12 girls) and thirty-three healthy adolescents (13.8±0.9 years; 20.3±3.2 kg·m^-2; 16 boys, 17 girls) completed an incremental ramp test and three heavy-intensity constant-work-rate cycle tests. Thirteen adolescents (7 boys, 6 girls; 6 asthma, 7 control) completed six-months high-intensity interval training (HIIT) and were compared to age- and sex-matched controls. Standard time-domain, frequency-domain and non-linear indices of HRV were derived at baseline, three- and six-months. Asthma did not influence HRV at baseline or following HIIT. Total power, low frequency and normalised low frequency power, and sympathovagal balance increased at three-months in HIIT, subsequently declining towards baseline at six-months. Normalised high frequency power was reduced at three-months in both groups, which was sustained at six-months. No effects of HIIT were observed in the time-domain nor in the non-linear indices. HRV was not influenced by asthma, potentially because such derangements are a function of disease progression, severity or duration. HIIT may be associated with a short-term shift towards greater sympathetic predominance during exercise, perhaps caused by physiological overload and fatigue.

Cultural Differences in Interpersonal Emotion Regulation

Cultural differences exist in the use of emotion regulation (ER) strategies, but the focus to date has been on intrapersonal ER strategies such as cognitive reappraisal. An emerging literature highlights the importance of interpersonal ER, which utilizes social cues to facilitate the regulation of emotional states. In cultures that place high value on social interconnectedness as integral to their collectivistic self-construal, including East Asian cultures, interpersonal ER strategies may be particularly effective in reducing negative affect but this has not been previously tested. In this study, two groups comprising East Asian (n = 48) and Western European (n = 38) participants were randomly assigned to receive a priming narration depicting the use of either interpersonal (e.g., social modeling, perspective taking) or intrapersonal (e.g., cognitive reappraisal) ER strategies during a stressful experience. They were then instructed to utilize similar ER strategies in an emotion reactivity task during which they viewed high arousing negative pictorial stimuli while their heart rate (HR), heart rate variability (high frequency power - HF-HRV) and subjective affective states were measured. First we found that the East Asian group reported higher use of interpersonal ER strategies of social modeling and perspective taking in daily life. During the experimental interpersonal prime exposure, the East Asian group showed elevated HF-HRV (relative to baseline) compared to the Western European group, indicating more adaptive ER, but this pattern was not sustained during the reactivity or recovery phases. Instead, the East Asian group demonstrated increased HF-HRV and decreased HR across both prime conditions. The East Asian group also showed greater decreases in positive affect across the course of the experiment. Furthermore, individual differences in social modeling and individualistic self-construal moderated the effect of the ER prime in the East Asian group at trend levels, and main effects for perspective taking and reappraisal were observed in the Western European group. The findings support the notion that engaging in interpersonal ER strategies may be more beneficial for East Asian groups when immediately exposed to a stressful situation, as these strategies are congruent with cultural context and preferences, but our priming methodology may have limited the longer-term benefits.

Cardiorespiratory Fitness, Adiposity, and Heart Rate Variability: The Coronary Artery Risk Development in Young Adults Study

PURPOSE

The importance of cardiorespiratory fitness versus adiposity in determining heart rate variability (HRV) is unclear.

METHODS

From the Coronary Artery Risk Development in Young Adults study, an observational cohort study, we included 2316 participants (mean age = 45.2 ± 3.6 yr at year 20, 57% female, 43% Black) with HRV measured in 2005-2006 (year 20) and graded exercise test duration (GXTd) and adiposity measures (body mass index and waist circumference) obtained in 1985-1986 (baseline) and 2005-2006. HRV measures (SD of all normal RR intervals [SDNN] and square root of the mean value of the squares of differences between all successive RR intervals [RMSSD]) were obtained from resting 30-s 12-lead ECG. Cross-sectional associations between GXTd, adiposity, and HRV were assessed at year 20. Longitudinal changes in GXTd and adiposity measures were categorized as ≥10% increase, <10% change (no change), or ≥10% decrease. We used multivariable logistic regression to assess associations of GXTd and adiposity measures with unfavorable versus more favorable HRV (lower 25th percentile vs upper 75th percentile).

RESULTS

A 1-SD increment in GXTd was associated with 22% and 32% lower odds of unfavorable SDNN and RMSSD, respectively; associations remained significant after adjustment for adiposity. A 1-SD increment in adiposity measures was associated with 16%-28% higher odds of unfavorable RMSSD; associations were not significant after adjustment for GXTd. Compared with no change/increase in GXTd, longitudinal decrease in GXTd was significantly associated with 55% and 94% higher odds of unfavorable SDNN and RMSSD, respectively, at year 20. These associations remained significant after adjusting for adiposity.

CONCLUSION

Cardiorespiratory fitness may be a stronger determinant of HRV than adiposity. Intervention studies are needed to better determine the differential effects of improved cardiorespiratory fitness versus weight loss on HRV.

Ultra-short term HRV features as surrogates of short term HRV: a case study on mental stress detection in real life

Background

This paper suggests a method to assess the extent to which ultra-short Heart Rate Variability (HRV) features (less than 5 min) can be considered as valid surrogates of short HRV features (nominally 5 min). Short term HRV analysis has been widely investigated for mental stress assessment, whereas the validity of ultra-short HRV features remains unclear. Therefore, this study proposes a method to explore the extent to which HRV excerpts can be shortened without losing their ability to automatically detect mental stress.

Methods

ECGs were acquired from 42 healthy subjects during a university examination and resting condition. 23 features were extracted from HRV excerpts of different lengths (i.e., 30 s, 1 min, 2 min, 3 min, and 5 min). Significant differences between rest and stress phases were investigated using non-parametric statistical tests at different time-scales. Features extracted from each ultra-short length were compared with the standard short HRV features, assumed as the benchmark, via Spearman’s rank correlation analysis and Bland-Altman plots during rest and stress phases. Using data-driven machine learning approaches, a model aiming to detect mental stress was trained, validated and tested using short HRV features, and assessed on the ultra-short HRV features.

Results

Six out of 23 ultra-short HRV features (MeanNN, StdNN, MeanHR, StdHR, HF, and SD2) displayed consistency across all of the excerpt lengths (i.e., from 5 to 1 min) and 3 out of those 6 ultra-short HRV features (MeanNN, StdHR, and HF) achieved good performance (accuracy above 88%) when employed in a well-dimensioned automatic classifier.

Conclusion

This study concluded that 6 ultra-short HRV features are valid surrogates of short HRV features for mental stress investigation.

Electronic supplementary material

The online version of this article (10.1186/s12911-019-0742-y) contains supplementary material, which is available to authorized users.

Impact of supportive therapy modalities on heart rate variability in cancer patients - a systematic review

Purpose: To systematically review literature for interventional studies and their impact on autonomic dysfunction assessed by heart rate variability in cancer patients.Methods: Research was conducted using the databases Medline/Pubmed, Scopus, and Web of science from their inception to October 2017. Original articles with an interventional design that reported changes in at least one heart rate variability parameter as outcome parameter were included and described.Results: Ten studies were identified as eligible for subsequent analysis. The main application field in oncological therapy setting was music therapy intervention, Traditional Chinese Medicine related treatments, exercise interventions, relaxation, and myofascial release techniques. Breast cancer was the most frequently described single cancer entity. Heart rate variability recording was performed with standard electrocardiography devices or wearable heart rate monitors, within a time range between 5 and 20 min and a sampling rate varying from 200 to 1000 Hz. No adverse events were reported in all studies.Conclusions: Supportive therapy modalities may have the potential to enhance vegetative functioning. In this context, heart rate variability analysis appears to be an easily applicable and safe method to evaluate cancer related autonomic dysfunction. More large prospective multicentre randomised controlled trials are needed.Implication for rehabilitationMost cancer patients face autonomic dysfunction due to the disease itself the applied treatments or combination of both.HRV measurement is an easy and safe method to asses autonomic dysfunction.Supportive treatments targeting on an elevation of the vagal tone and autonomic balance in general might have beneficial effects for cancer patients.

Effects of Cold Stimulation on Cardiac-Vagal Activation in Healthy Participants: Randomized Controlled Trial

Background

The experience of psychological stress has not yet been adequately tackled with digital technology by catering to healthy individuals who wish to reduce their acute stress levels. For the design of digitally mediated solutions, physiological mechanisms need to be investigated that have the potential to induce relaxation with the help of technology. Research has shown that physiological mechanisms embodied in the face and neck regions are effective for diminishing stress-related symptoms. Our study expands on these areas with the design for a wearable in mind. As this study charts new territory in research, it also is a first evaluation of the viability for a wearables concept to reduce stress.

Objective

The objectives of this study were to assess whether (1) heart rate variability would increase and (2) heart rate would decrease during cold stimulation using a thermode device compared with a (nonstimulated) control condition. We expected effects in particular in the neck and cheek regions and less in the forearm area.

Methods

The study was a fully randomized, within-participant design. Volunteer participants were seated in a laboratory chair and tested with cold stimulation on the right side of the body. A thermode was placed on the neck, cheek, and forearm. We recorded and subsequently analyzed participants’ electrocardiogram. The cold stimulation was applied in 16-second intervals over 4 trials per testing location. The control condition proceeded exactly like the cold condition, except we manipulated the temperature variable to remain at the baseline temperature. We measured heart rate as interbeat intervals in milliseconds and analyzed root mean square of successive differences to index heart rate variability. We analyzed data using a repeated-measures ANOVA (analysis of variance) approach with 2 repeated-measures factors: body location (neck, cheek, forearm) and condition (cold, control).

Results

Data analysis of 61 participants (after exclusion of outliers) showed a main effect and an interaction effect for body location and for condition, for both heart rate and heart rate variability. The results demonstrate a pattern of cardiovascular reactivity to cold stimulation, suggesting an increase in cardiac-vagal activation. The effect was significant for cold stimulation in the lateral neck area.

Conclusions

The results confirmed our main hypothesis that cold stimulation at the lateral neck region would result in higher heart rate variability and lower heart rate than in the control condition. This sets the stage for further investigations of stress reduction potential in the neck region by developing a wearable prototype that can be used for cold application. Future studies should include a stress condition, test for a range of temperatures and durations, and collect self-report data on perceived stress levels to advance findings.

Investigation of Lagged Poincaré Plot reliability in ultra-short synthetic and experimental Heart Rate Variability series

This study reports on the reliability of Lagged Poincaré Plot (LPP) parameters calculated from ultra-short cardiovascular time series (from 30 to 180 seconds). ity (HRV) signals, whereas a few studies have studied nonlinear approaches. Particularly, methods derived from the phase-space theory, especially the ones employing multi-lag analyses, are usually considered to be inaccurate with a low number of samples. Here we propose a comprehensive study about LPP, using both synthetic and real RR series. Specifically, we considered 109 5-minutes HRV series: 60 synthetic series generated through the Integral Pulse Frequency Modulation (IPFM) model and 49 experimental series acquired from healthy subjects during resting-state. Three parameters have been extracted through the ellipse-fitting method, SD1, SD2 and S, using ten values of lag. All LPP parameters were estimated by averaging estimates gathered from segments of 30, 120 and 180 seconds, and compared with the once from 5-minute series. Results showed Spearman's correlation coefficients higher than 0.9 in both synthetic and real series. In conclusion, SD1 gave promising results in terms of percentage absolute error, when it was extracted from series with a duration less than three minutes.

Validity of spectral analysis based on heart rate variability from 1-minute or less ECG recordings

BACKGROUND

To broaden the utility of heart rate variability (HRV) in clinical medicine and mass screening, results based on shorter electrocardiogram (ECG) recordings require validation with those based on standard 5-minute recordings. We investigated the association between HRV variables obtained from 5-minute ECGs with those obtained from ECGs shorter than 5 minutes.

METHODS

Twenty-two participants aged 20-69 years underwent 5-minute resting ECG recordings in the supine position with natural breathing. Spectral analysis using MemCalc method was performed to calculate high-frequency (HF, which required at least 10 seconds) and low-frequency (LF, which required at least 30 seconds) components. Participants were not strictly preconditioned as in previous experimental studies in order to simulate a setting similar to that of a general health checkup. Associations of each variable between the 5-minute ECG recordings and those for shorter recordings were examined by Pearson's correlation coefficients and Bland-Altman plots.

RESULTS

HF and LF components were log-transformed based on their distributions. Correlation coefficients between 5-minute data and shorter recordings in the supine position with natural breathing ranged from 0.80 to 0.91 (HF by 10-second recording, 0.80; LF by 30-second recording, 0.83, respectively). Bland-Altman plots showed that gaps between the values from both methods slightly increased as the HF and LF component values increased.

CONCLUSIONS

Although slight proportional errors were possible, values from standard 5-minute and shorter recordings in the supine position were strongly correlated. Our findings suggest that shorter ECG data without strict preconditioning can be reliably used for spectral analysis.

Short-Term Test-Retest Reliability of Respiratory Sinus Arrhythmia (RSA) in Young Adults

Abstract. Despite the burgeoning use of respiratory sinus arrhythmia (RSA), heart period (HP), and blood pressure (BP) to study individual differences in autonomic regulatory processes in young adults, few studies have examined the short-term reliability of such autonomic measures in emerging adulthood. If resting autonomic measures indeed reflect “trait-like” individual differences, they should have acceptable levels of test-retest reliability. We examined the 1-month test-retest reliability of resting measures of RSA as well as HP, systolic (SBP) and diastolic blood pressure (DBP) in a sample of 41 healthy young adults. Test-retest reliability of all four measures was good-to-excellent across the 1-month period. However, uncontrolled mean RSA declined from Time 1 to Time 2, suggesting that while individual differences in RSA were stable, mean RSA appeared to be sensitive to condition effects. Even with random variation, all of these measures were stable across one month, demonstrating acceptable short-term test-retest reliability in emerging adulthood.

Are ultra-short heart rate variability features good surrogates of short-term ones? State-of-the-art review and recommendations

Ultra-short heart rate variability (HRV) analysis refers to the study of HRV features in excerpts of length <5 min. Ultra-short HRV is widely growing in many healthcare applications for monitoring individual's health and well-being status, especially in combination with wearable sensors, mobile phones, and smart-watches. Long-term (nominally 24 h) and short-term (nominally 5 min) HRV features have been widely investigated, physiologically justified and clear guidelines for analysing HRV in 5 min or 24 h are available. Conversely, the reliability of ultra-short HRV features remains unclear and many investigations have adopted ultra-short HRV analysis without questioning its validity. This is partially due to the lack of accepted algorithms guiding investigators to systematically assess ultra-short HRV reliability. This Letter critically reviewed the existing literature, aiming to identify the most suitable algorithms, and harmonise them to suggest a standard protocol that scholars may use as a reference in future studies. The results of the literature review were surprising, because, among the 29 reviewed papers, only one paper used a rigorous method, whereas the others employed methods that were partially or completely unreliable due to the incorrect use of statistical tests. This Letter provides recommendations on how to assess ultra-short HRV features reliably and proposes an inclusive algorithm that summarises the state-of-the-art knowledge in this area.

Reproducibility of Heart Rate Variability Is Parameter and Sleep Stage Dependent

Objective: Measurements of heart rate variability (HRV) during sleep have become increasingly popular as sleep could provide an optimal state for HRV assessments. While sleep stages have been reported to affect HRV, the effect of sleep stages on the variance of HRV parameters were hardly investigated. We aimed to assess the variance of HRV parameters during the different sleep stages. Further, we tested the accuracy of an algorithm using HRV to identify a 5-min segment within an episode of slow wave sleep (SWS, deep sleep).

Methods: Polysomnographic (PSG) sleep recordings of 3 nights of 15 healthy young males were analyzed. Sleep was scored according to conventional criteria. HRV parameters of consecutive 5-min segments were analyzed within the different sleep stages. The total variance of HRV parameters was partitioned into between-subjects variance, between-nights variance, and between-segments variance and compared between the different sleep stages. Intra-class correlation coefficients of all HRV parameters were calculated for all sleep stages. To identify an SWS segment based on HRV, Pearson correlation coefficients of consecutive R-R intervals (rRR) of moving 5-min windows (20-s steps). The linear trend was removed from the rRR time series and the first segment with rRR values 0.1 units below the mean rRR for at least 10 min was identified. A 5-min segment was placed in the middle of such an identified segment and the corresponding sleep stage was used to assess the accuracy of the algorithm.

Results: Good reproducibility within and across nights was found for heart rate in all sleep stages and for high frequency (HF) power in SWS. Reproducibility of low frequency (LF) power and of LF/HF was poor in all sleep stages. Of all the 5-min segments selected based on HRV data, 87% were accurately located within SWS.

Conclusions: SWS, a stable state that, in contrast to waking, is unaffected by internal and external factors, is a reproducible state that allows reliable determination of heart rate, and HF power, and can satisfactorily be detected based on R-R intervals, without the need of full PSG. Sleep may not be an optimal condition to assess LF power and LF/HF power ratio.

Heart Rate Variability and Cognitive Function In Middle-Age Adults: The Coronary Artery Risk Development in Young Adults

BACKGROUND

Low heart rate variability (HRV), a marker of cardiac autonomic dysfunction, has been associated with major risk factors of cognitive impairment. Yet, the direct association of HRV with cognitive function remains relatively unexplored, particularly in midlife.

METHODS

In 2005, 2 measures of short-term HRV, the SD of normal-to-normal intervals (SDNN) and the root mean square of successive differences (RMSSD), were calculated for participants of the Coronary Artery Risk Development in Young Adults study, and then categorized into quartiles. Five years later, 3 cognitive tests were administered for verbal memory ("Rey Auditory-Verbal Learning Test", RAVLT, range 0-15), processing speed ("Digit Symbol Substitution Test", DSST, range 0-133), and executive function ("Stroop interference").

RESULTS

Two thousand one hundred and eighteen participants (57.7% female, 42.2% Black) with a mean baseline age of 45.3 years were included in this analysis. In demographic-adjusted models, compared to participants with quartile 1 SDNN (lowest quartile), participants in the upper quartiles of SDNN scored better on the DSST (quartile 4: β = 1.83 points better, P = 0.03; and quartile 3: β = 1.95 points better, P = 0.03) and on the stroop (quartile 3: β = 1.19 points better, P < 0.05; and quartile2: β = 1.44 points better, P = 0.02). After adjusting for behavioral and cardiovascular risk factors, higher quartile SDNN remained significantly associated with better stroop score (quartile 3: β = 1.21 points better, P = 0.04; and quartile 2: β = 1.72 points better, P < 0.01) but not with DSST. There was no association between quartile of RMSSD and cognitive function, from fully adjusted models.

CONCLUSIONS

Our findings suggest that higher quartile SDDN is associated with better executive function in midlife, above, and beyond cardiovascular risk factors.

Relations of Demographic and Clinical Factors With Cardiovascular Autonomic Function in a Population-Based Study: An Assessment By Quantile Regression

BACKGROUND

The relationships of many factors with cardiovascular autonomic function (CVAF) outcome parameters may not be uniform across the entire distribution of the outcome. We examined how demographic and clinical factors varied with different subgroups of CVAF parameters.

METHODS

Quantile regression was applied to a cross-sectional analysis of 4,167 adults (56% male; age range, 50-84 years) from 4 ethnic groups (3,419 New Zealand European, 303 Pacific, 227 Maori, and 218 South Asian) and without diagnosed cardiac arrhythmia. Pulse rate variability (root mean square of successive differences (RMSSD) and SD of pulse intervals) and baroreflex sensitivity were response variables. Independent variables were age, sex, ethnicity, brachial and aortic blood pressure (BP) variables, body mass index (BMI), and diabetes.

RESULTS

Ordinary linear regression showed that age, sex, Pacific and Maori ethnicity, BP variables, BMI, and diabetes were associated with CVAF parameters. But quantile regression revealed that, across CVAF percentiles, the slopes for these relationships: (i) varied by more than 10-fold in several cases and sometimes changed direction and (ii) noticeably differed in magnitude often (by >3-fold in several cases) compared to ordinary linear regression coefficients. For instance, age was inversely associated with RMSSD at the 10th percentile of this parameter (β = -0.12 ms/year, 95% confidence interval = -0.18 to -0.09 ms/year) but had a positive relationship at the 90th percentile (β = 3.17 ms/year, 95% confidence interval = 2.50 to 4.04 ms/year).

CONCLUSIONS

The relationships of demographic and clinical factors with CVAF parameters are, in many cases, not uniform. Quantile regression provides an improved assessment of these associations.

Longitudinal association of short-term, metronome-paced heart rate variability and echocardiographically assessed cardiac structure at a 4-year follow-up: results from the prospective, population-based CARLA cohort

Aims

To assess the value of cardiac structure/function in predicting heart rate variability (HRV) and the possibly predictive value of HRV on cardiac parameters.

Methods and results

Baseline and 4-year follow-up data from the population-based CARLA cohort were used (790 men, 646 women, aged 45-83 years at baseline and 50-87 years at follow-up). Echocardiographic and HRV recordings were performed at baseline and at follow-up. Linear regression models with a quadratic term were used. Crude and covariate adjusted estimates were calculated. Missing values were imputed by means of multiple imputation. Heart rate variability measures taken into account consisted of linear time and frequency domain [standard deviation of normal-to-normal intervals (SDNN), high-frequency power (HF), low-frequency power (LF), LF/HF ratio] and non-linear measures [detrended fluctuation analysis (DFA1), SD1, SD2, SD1/SD2 ratio]. Echocardiographic parameters considered were ventricular mass index, diastolic interventricular septum thickness, left ventricular diastolic dimension, left atrial dimension systolic (LADS), and ejection fraction (Teichholz). A negative quadratic relation between baseline LADS and change in SDNN and HF was observed. The maximum HF and SDNN change (an increase of roughly 0.02%) was predicted at LADS of 3.72 and 3.57 cm, respectively, while the majority of subjects experienced a decrease in HRV. There was no association between further echocardiographic parameters and change in HRV, and there was no evidence of a predictive value of HRV in the prediction of changes in cardiac structure.

Conclusion

In the general population, LADS predicts 4-year alteration in SDNN and HF non-linearly. Because of the novelty of the result, analyses should be replicated in other populations.

Estimation of confidence limits for descriptive indexes derived from autoregressive analysis of time series: Methods and application to heart rate variability

The growing interest in personalized medicine requires making inferences from descriptive indexes estimated from individual recordings of physiological signals, with statistical analyses focused on individual differences between/within subjects, rather than comparing supposedly homogeneous cohorts. To this end, methods to compute confidence limits of individual estimates of descriptive indexes are needed. This study introduces numerical methods to compute such confidence limits and perform statistical comparisons between indexes derived from autoregressive (AR) modeling of individual time series. Analytical approaches are generally not viable, because the indexes are usually nonlinear functions of the AR parameters. We exploit Monte Carlo (MC) and Bootstrap (BS) methods to reproduce the sampling distribution of the AR parameters and indexes computed from them. Here, these methods are implemented for spectral and information-theoretic indexes of heart-rate variability (HRV) estimated from AR models of heart-period time series. First, the MS and BC methods are tested in a wide range of synthetic HRV time series, showing good agreement with a gold-standard approach (i.e. multiple realizations of the "true" process driving the simulation). Then, real HRV time series measured from volunteers performing cognitive tasks are considered, documenting (i) the strong variability of confidence limits' width across recordings, (ii) the diversity of individual responses to the same task, and (iii) frequent disagreement between the cohort-average response and that of many individuals. We conclude that MC and BS methods are robust in estimating confidence limits of these AR-based indexes and thus recommended for short-term HRV analysis. Moreover, the strong inter-individual differences in the response to tasks shown by AR-based indexes evidence the need of individual-by-individual assessments of HRV features. Given their generality, MC and BS methods are promising for applications in biomedical signal processing and beyond, providing a powerful new tool for assessing the confidence limits of indexes estimated from individual recordings.

Heart rate variability and lifetime risk of cardiovascular disease: the Atherosclerosis Risk in Communities Study

PURPOSE

The purpose of this study was to estimate the heart rate variability (HRV)-related lifetime cardiovascular disease (CVD) risk.

METHODS

We followed 9744 participants without baseline CVD and used a life-table approach to estimate lifetime CVD risk (coronary heart disease, heart failure, and stroke) from 45 through 85 years according to several HRV measures (the SD of RR intervals [SD_NN], the root mean square of successive differences of successive RR intervals, the mean of all normal RR intervals [mean_NN], low-frequency [LF] and high-frequency [HF] power, and the LF/HF ratio).

RESULTS

During 192,110 person-years of follow-up, we documented 2856 CVD events. Cox regression analyses with the false discovery rate method correction showed independent associations of SD_NN, mean_NN, LF, and LF/HF in women with CVD. Lifetime CVD risks in the lowest compared with the highest tertile were significantly increased in men for LF/HF (51.3% [95% confidence interval, 47.3-54.7] vs. 43.9% [40.1-47.2]), and in women for SD_NN (39.4% [36.0-43.0] vs. 29.9% [26.3-33.0]), mean_NN (39.3% [35.7-42.7] vs. 28.9% [25.7-31.7]), LF (39.4% [35.9-43.0] vs. 30.0% [26.2-33.2]), and LF/HF (37.6% [33.9-40.9] vs. 30.0% [26.8-32.7]).

CONCLUSIONS

Greater HRV was modestly associated with lower lifetime CVD risk.