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

Sex Differences in Time-Domain and Frequency-Domain Heart Rate Variability Measures of Fatigued Drivers

The effects of fatigue on a driver's autonomic nervous system (ANS) were investigated through heart rate variability (HRV) measures considering the difference of sex. Electrocardiogram (ECG) data from 18 drivers were recorded during a simulator-based driving experiment. Thirteen short-term HRV measures were extracted through time-domain and frequency-domain methods. First, differences in HRV measures related to mental state (alert or fatigued) were analyzed in all subjects. Then, sex-specific changes between alert and fatigued states were investigated. Finally, sex differences between alert and fatigued states were compared. For all subjects, ten measures showed significant differences (Mann-Whitney U test, p < 0.01) between different mental states. In male and female drivers, eight and four measures, respectively, showed significant differences between different mental states. Six measures showed significant differences between males and females in an alert state, while ten measures showed significant sex differences in a fatigued state. In conclusion, fatigue impacts drivers' ANS activity, and this impact differs by sex; more differences exist between male and female drivers' ANS activity in a fatigued state than in an alert state.

Relationships Between Heart Rate Variability, Occupational Performance, and Fitness for Tactical Personnel: A Systematic Review

Objectives: Heart Rate Variability has gained substantial interest in both clinical and athletic settings as a measurement tool for quantifying autonomic nervous system activity and psychophysiological stress. However, its uses in tactical work settings, such as military, police, and firefighting environments, remain controversial. Given the physical, mental, and emotional stress public safety personnel face both operationally and in training, heart rate variability measurement may be key in promoting their health, safety and operational effectiveness.

Methods: This study identified, critically appraised, and summarized primary studies investigating relationships between heart rate variability and outcomes of interest to tactical personnel. Key literature databases were searched, and quality assessment checklists were applied to analyze retained literature. The results of the screening and assessment processes, along with key data extracted from each study were summarized and tabulated. Research gaps were also identified to facilitate improvements to how tactical personnel and health or performance providers may best utilize heart rate variability to monitor or promote personnel health and performance, and thereby facilitate public safety.

Results: Twenty studies were included and were all of generally high quality. Cohort size, length of follow-up, measurement objectives, data acquisition, and data analysis all varied considerably across studies, precluding meta-analysis. However, study results correlating heart rate variability and relevant outcomes indicated that overall, heart rate variability is an effective indicator of key fitness and performance elements in the tactical work setting.

Conclusions: Heart rate variability can be an effective health and performance tool in tactical work environments. However, measurement methods must be carefully selected and applied. Further research is required to understand causal relationships. Specifically, larger cohort inclusion and the isolation and study of specific variables unique to public safety work and training may improve the effectiveness of heart rate variability measurement to provide meaningful information to end users and providers.

Early life maltreatment and resting-state heart rate variability: A systematic review and meta-analysis

Recent focus on the consequences of early life adversity (ELA) in neurobiological research led to a variety of findings suggesting alterations in several physiological systems, such as the cardiovascular system. In this systematic review and meta-analysis, we focused on the relationship between early life maltreatment (ELM), one form of ELA, and resting vagal activity indexed by resting-state heart rate variability (HRV). A systematic search of the literature yielded 1'264 hits, of which 32 studies reporting data for group comparisons or correlations were included. By quantitative synthesis of existing studies using random-effect models, we found no evidence for a relationship between ELM exposure and resting vagal activity in principal. Conducting meta-regression analyses, however, we found the relationship between ELM and resting vagal activity to significantly vary as a function of both age and the presence of psychopathology. In light of the current multitude of vastly unclear pathways linking ELM to the onset of disease, we emphasize the need for further research and outline several aspects to consider in future studies.

Can seizure-related heart rate differentiate epileptic from psychogenic nonepileptic seizures?

OBJECTIVES

We aimed to (1) determine if seizure-related heart rate (HR) differentiates epileptic seizures (ES) from psychogenic nonepileptic seizures (PNES); (2) define the most useful point of the following HR measurements: preictal, ictal-onset, maximal-ictal, or postictal; and (3) delineate the optimal HR cutoff points (absolute HR and relative HR increase) to differentiate ES from PNES.

METHODS

All video-electroencephalography (VEEG) recorded at an Australian tertiary hospital from May 2009 to November 2015 were retrospectively reviewed. Baseline (during rest and wakefulness), 1-min preictal, ictal-onset, maximal-ictal, and 1-min postictal HR were measured for each ES and PNES event. Events lasting <10 s or with uninterpretable electrocardiogram (ECG) due to artifacts were excluded. Receiver operating characteristic curve analysis was performed to assess the diagnostic accuracy of HR reflected by the area under the curve (AUC).

RESULTS

Video-electroencephalography of 341 ES and 265 PNES from 130 patients were analyzed. The AUC for preictal, ictal-onset, maximal-ictal, and postictal HR were found to have poor differentiation between all types of ES and PNES. However, comparing bilateral tonic-clonic ES and PNES, AUC for absolute maximal-ictal HR was 0.84 (95% confidence interval [CI]: 0.73-0.95) and for absolute postictal HR was 0.90 (95% CI: 0.81-1.00) indicating good diagnostic discrimination. Using Youden's index to diagnose tonic-clonic ES, the optimal cutoff point for absolute maximal-ictal HR was 114 bpm (sensitivity: 84%, specificity: 82%) and for absolute postictal HR was 90 bpm (sensitivity: 91%, specificity: 82%).

CONCLUSION

These findings suggest that seizure-related HR is useful in differentiating bilateral tonic-clonic ES from PNES. Based on the AUC, the best diagnostic measurements are maximal-ictal and postictal HR.

A Field Study to Capture Events of Interest (EoI) from Living Labs Using Wearables for Spatiotemporal Monitoring Towards a Framework of Smart Health (sHealth)

Everyday wearables such as smartwatches or smart bands can play a pivotal role in the field of fitness and wellness and hold the prospect to be used for early disease detection and monitoring towards Smart Health (sHealth). One of the challenges is the extraction of reliable biomarkers from data collected using these devices in the real world (Living Labs). In this yearlong field study, we collected the nocturnal instantaneous heart rate from 9 participants using wrist-worn commercial smart bands and extracted heart rate variability features (HRV). In addition, we measured core body temperature using our custom-designed flexible Inkjet-Printed (IJP) temperature sensor and SpO2 with a finger pulse oximeter. The core body temperature along with user-reported symptoms have been used for automated spatiotemporal monitoring of flu symptoms severity in real-time. The extracted HRV feature values are within the 95% confidence interval of normative values and shows an anticipated trend for gender and age. The resulting dataset from this study is a novel addition and may be used for future investigations.Clinical Relevance- The findings of this study shows usability of wearables in detection and monitoring of diseases such as obstructive sleep apnea reducing the prevalence of undiagnosed cases. This framework also has potentials to monitor outbreaks of flu and other diseases with spatiotemporal distribution.

State anxiety biases estimates of uncertainty and impairs reward learning in volatile environments

Clinical and subclinical (trait) anxiety impairs decision making and interferes with learning. Less understood are the effects of temporary anxious states on learning and decision making in healthy populations, and whether these can serve as a model for clinical anxiety. Here we test whether anxious states in healthy individuals elicit a pattern of aberrant behavioural, neural, and physiological responses comparable with those found in anxiety disorders-particularly when processing uncertainty in unstable environments. In our study, both a state anxious and a control group learned probabilistic stimulus-outcome mappings in a volatile task environment while we recorded their electrophysiological (EEG) signals. By using a hierarchical Bayesian model of inference and learning, we assessed the effect of state anxiety on Bayesian belief updating with a focus on uncertainty estimates. State anxiety was associated with an underestimation of environmental uncertainty, and informational uncertainty about the reward tendency. Anxious individuals' beliefs about reward contingencies were more precise (had smaller uncertainty) and thus more resistant to updating, ultimately leading to impaired reward-based learning. State anxiety was also associated with greater uncertainty about volatility. We interpret this pattern as evidence that state anxious individuals are less tolerant to informational uncertainty about the contingencies governing their environment and more willing to be uncertain about the level of stability of the world itself. Further, we tracked the neural representation of belief update signals in the trial-by-trial EEG amplitudes. In control participants, lower-level precision-weighted prediction errors (pwPEs) about reward tendencies were represented in the ERP signals across central and parietal electrodes peaking at 496 ms, overlapping with the late P300 in classical ERP analysis. The state anxiety group did not exhibit a significant representation of low-level pwPEs, and there were no significant differences between the groups. Smaller variance in low-level pwPE about reward tendencies in state anxiety could partially account for the null results. Expanding previous computational work on trait anxiety, our findings establish that temporary anxious states in healthy individuals impair reward-based learning in volatile environments, primarily through changes in uncertainty estimates, which play a central role in current Bayesian accounts of perceptual inference and learning.

Heart Rate Variability and Exceptional Longevity

Centenarians are the paradigm of human extreme longevity and healthy aging, because they have postponed, if not avoided, mayor age-related diseases. The purpose of this study was to investigate potential differences in resting heart rate variability (HRV) between young adults, octogenarians, and centenarians and assess whether HRV variables are predictors of all-cause mortality in centenarians. To this end, three groups of participants: young adults (N = 20; 20.6 ± 2.3 years), octogenarians (N = 18; 84.1 ± 2.6 years), and centenarians (N = 17; 101.9 ± 1.9 years) were monitored for 15 min at rest (seated, without moving or talking) to measure RR intervals, from which HRV was evaluated. Our results showed a clear decrease with age in the main parasympathetic HRV variables, as well as in the standard deviation (SD) of the RR series [SD of normal-to-normal interval (SDNN)] and in low frequency (LF) heart rate (HR) oscillations, although differences between octogenarians and centenarians did not reach statistical significance. In 14 centenarians followed until death, only SDNN showed significant correlation (ρ = 0.536; p = 0.048) with survival prognosis. Additionally, SDNN <19 ms was associated with early mortality (≤1 year) in centenarians (Hazard Ratio = 5.72). In conclusion, HRV indices reflecting parasympathetic outflow as well as SDNN and LF all present an age-related reduction, which could be representative of a natural exhaustion of allostatic systems related to age. Moreover, low SDNN values (<19 ms) could be associated with early mortality in centenarians. HRV seems to play a role in exceptional longevity, which could be accounted for by centenarians' exposome.

Parsing inter- and intra-individual variability in key nervous system mechanisms of stress responsivity and across functional domains

Exposure to stressful events is omnipresent in modern human life, yet people show considerable heterogeneity in the impact of stress exposure(s) on their functionality and overall health. Encounter with stressor(s) is counteracted by an intricate repertoire of nervous-system responses. This narrative review starts with a brief summary of the vast evidence that supports heart rate variability, cortisol secretion, and large-scale cortical network interactions as kay physiological, endocrinological, and neural mechanisms of stress responsivity, respectively. The second section highlights potential sources for inter-individual variability in these mechanisms, by focusing on biological, environmental, social, habitual, and psychological factors that may influence stress responsivity patterns and thus contribute to heterogeneity in the impact of stress exposure on functionality and health. The third section introduces intra-individually variability in stress responsivity across functional domains as a novel putative source for heterogeneity in the impact of stress exposure. Challenges and future directions are further discussed. Parsing inter- and intra-individual variability in nervous-system mechanisms of stress responsivity and across functional domains is critical towards potential clinical translation.

Central serous chorioretinopathy and heart rate variability analysis with a smartphone application

The purpose of this study was to quantitatively analyze heart rate variability (HRV) in patients with central serous chorioretinopathy (CSC) by using a smartphone-based application (ANBAI: DUMSCO Inc.) for measurement, and to clarify its relationships with CSC. The subjects were 64 CSC patients (mean age 48.7 ± 7.6 years, 57 males and 7 females). After providing consent, the patients downloaded ANBAI apps to their smartphones. HRV was measured by photoelectric volume pulse wave measurement with a smartphone camera each morning for a minimum of 1 week. The primary outcome was to analyze HRV by calculating log LF/HF (Low Frequency/High Frequency components), an index of autonomic tone, which was then compared with a control group of 35,226 individuals from the application. Secondary outcome measures included disease duration, body mass index, exercise habits, smoking history, steroid use, occupation, lifestyle regularity, psychological fatigue, physical fatigue, and average sleep time. The log LF/HF was significantly higher in the patient group than in the control group (P < 0.001). Log LF/HF was significantly lower in patients with exercise habits as a factor contributing to log LF/HF in the patient group (P = 0.019). Analysis of HRV in CSC patients showed an impairment of the autonomic nervous system. Exercise habits may also be associated with CSC.

Influence of ageing on circadian rhythm of heart rate variability in healthy subjects

BACKGROUND

The analysis of the circadian rhythm of heart rate variability (HRV) represents a relevant physiological tool to assess the vagal system. However, the influence of age (mostly >75 years) on HRV is not widely known.

AIMS

The aim of this study was to evaluate the influence of age on HRV, particularly in the elderly and to identify a model of this relationship. The study was carried out by examining linear and nonlinear parameters extracted from HRV, including individuals over 75 years for which there is no research available.

METHODS

Data from 140 healthy subjects were sex matched and divided into young (young group: 15-39 years old), adult (adult group: 40-64 years old) and senior (senior group: 65-90 years old) groups. 24-h Holter monitoring was used and several HRV parameters were extracted from time, and spectral and nonlinear analyses were examined.

RESULTS

Time-domain parameters, mainly standard deviation of the NN interval (SDNN) and number of successive differences of intervals which differ by more than 50 ms, presented significant differences between the young group and the other two groups during the 24-h period, while normalized spectral parameters (LFn, HFn and low frequency/high frequency), as well as nonlinear parameters, mainly β exponent and fractal dimension, showed significant difference between the senior group and the other two groups. All these parameters showed a similar circadian rhythm with significant differences between the mean day and night values, especially in young and adult group cohorts. Moreover, a parabolic relationship between these parameters and age was highlighted with an opposite trend over about 60 years compared with younger people.

CONCLUSION

A progressive physiological autonomic imbalance is present in ageing. The inverse trend in the relation between HRV parameters and age found in the senior group could be mainly due to a faster fluctuation of RR. This should be considered when studying changes in the cardiac autonomic nervous control.

Resting Heart Rate and Heart Rate Variability in the Year Following Acute Coronary Syndrome: How Do Women Fare?

BACKGROUND

Women experience poorer health outcomes following acute coronary syndrome (ACS). Heart rate (HR) and heart rate variability (HRV) have emerged as sensitive and cost-effective markers of autonomic function and prognostic risk factors of poor cardiac outcomes. The aim of the current study was to investigate whether sex-specific differences existed across HR and five parameters of HRV, at 1 and 12 months following ACS diagnosis.

METHODS

Between January 2013 and June 2014, a sample of 416 ACS patients was enrolled in the Anxiety Depression & Heart Rate Variability in cardiac patients: Evaluating the impact of Negative emotions on functioning after Twenty four months (ADVENT) longitudinal cohort study. At 1 and 12 months following discharge, patient HR and HRV (root mean square of successive differences [RMSDD], standard deviation of RR intervals [SDRR], high frequency power [HF], low frequency power [LF], very low frequency power [VLF]) was measured via three-lead electrocardiogram.

RESULTS

At 1 month post-ACS, sex was a significant predictor of HR and VLF power in fully- adjusted models. At 12 months post-ACS, sex was a predictor of HR, SDRR and VLF power in fully-adjusted models.

CONCLUSION

Sex-specific differences in resting HR and HRV were observed in the year following ACS, whereby women had higher HR and lower HRV, suggestive of poorer autonomic function. Further large-scale cohort studies examining autonomic function as a driver of sex-specific outcomes following ACS are required.

The effects of varying doses of caffeine on cardiac parasympathetic reactivation following an acute bout of anaerobic exercise in recreational athletes

BACKGROUND

To examine the effects of varying doses of caffeine on autonomic reactivation following anaerobic exercise.

METHODS

Recreationally active males (N = 20; 24 ± 2y) participated in a randomized, double-blind, placebo-controlled, crossover study where participants ingested: [1] Control (CON; no supplement), [2] a non-caffeinated placebo (PLA), [3] 3-mg∙kg- 1 of caffeine (CAF3) or [4] 6-mg∙kg- 1 of caffeine (CAF6) prior to Wingate testing. Parasympathetic (lnRMSSD, primary outcome) and global HRV (lnSDNN, secondary outcome) were assessed at rest (i.e., pre-ingestion), 45-min post-ingestion, and 5-min and 35-min post-exercise recovery. We used a GLM to assess mean (95% CI) changes from pre-ingestion baseline.

RESULTS

Overall, we observed a significant trend for lnRMSSD and lnSDNN (both, p = 0.001, ηp2 = 0.745). Forty-five minutes after treatment ingestion, we observed a significant increase in lnRMSSD for CAF3 (0.15 ms, 95%CI, 0.07,0.24) and CAF6 (0.16 ms, 95%CI, 0.06,0.25), both being significant (both, p <  0.004) vs. CON (- 0.02 ms, 95%CI, - 0.09,0.04). Five-minutes after exercise, all treatments demonstrated significant declines in lnRMSSD vs. baseline (all, p <  0.001). After 35-min of recovery, lnRMSSD returned to a level not significantly different than baseline for CAF3 (0.03 ms, 95%CI, - 0.05, 0.12) and CAF6 (- 0.03 ms, 95%CI, - 0.17, 0.10), while PLA (- 0.16 ms, 95%CI, - 0.25, - 0.06) and CON (- 0.17 ms, 95%CI, - 0.28, - 0.07) treatments remained significantly depressed. A similar pattern was also observed for SDNN.

CONCLUSION

Caffeine ingestion increases resting cardiac autonomic modulation and accelerates post-exercise autonomic recovery after a bout of anaerobic exercise in recreationally active young men. However, no differences between caffeine doses on cardiac autonomic reactivity were observed.

Entropy Analysis of RR-Time Series From Stress Tests

The RR-interval time series or tachograms obtained from electrocardiograms have been widely studied since they reflect the cardiac variability, and this is an indicative of the health status of a person. The tachogram can be seen as a highly non-linear and complex time series, and therefore, should be analyzed with non-linear techniques. In this work, several entropy measures, Sample Entropy (SampEn), Approximate Entropy (ApEn), and Fuzzy Entropy (FuzzyEn) are used as a measure of heart rate variability (HRV). Tachograms belonging to thirty-nine subjects were obtained from a cardiac stress test consisting of a rest period followed by a period of moderate physical activity. Subjects are grouped according to their physical activity using the IPAQ sedentary and active questionnaire, we work with youth and middle-aged adults. The entropy measures for each group show that for the sedentary subjects the values are high at rest and decrease appreciably with moderate physical activity, This happens for both young and middle-aged adults. These results are highly reproducible. In the case of the subjects that exercise regularly, an increase in entropy is observed or they tend to retain the entropy value that they had at rest. It seems that there is a possible correlation between the physical condition of a person with the increase or decrease in entropy during moderate physical activity with respect to the entropy at rest. It was also observed that entropy during longer physical activity tests tends to decrease as fatigue accumulates, but this decrease is small compared to the change that occurs when going from rest to physical activity.

Herzfrequenzvariabilitätsanalyse in der betriebsärztlichen Praxis

In dem vorliegenden Beitrag werden basierend auf einer selektiven Literaturrecherche und unter Berücksichtigung aktueller Leitlinien die Rahmenbedingungen der Herzfrequenzvariabilitätsanalyse (HRV-Analyse), die Auswahl der HRV-Parameter bei den verschiedenen Fragestellungen und die Möglichkeiten der Nutzbarkeit der HRV für die betriebsärztliche Praxis zusammengefasst. Inzwischen in der praktischen Anwendung gut etabliert, werden die HRV-Parameter als Beanspruchungsindikatoren für die Einschätzung der Regulationsmechanismen und funktionalen Reserven des Herz-Kreislauf-Systems eingesetzt.

Heart Rate Variability, Risk-Taking Behavior and Resilience in Firefighters During a Simulated Extinguish-Fire Task

Firefighters face a high-risk potential, thus their psychological ability to cope with critical or traumatic events is a crucial characteristic. This study examines correlations between cardiac autonomic modulation, risk-taking behavior, and resilience in professional firefighters. Twenty male professional firefighters underwent a 20 min beat-to-beat heart rate (HR) monitoring at baseline in the morning upon awakening, then before, during and after a realistic deployment in a container, systematically set on fire. Risk-taking behavior, resilience, and subjective stress were assessed by specific validated tools after deployment: the Risk-taking Scale (R-1), the Resilience Scale (RS-13), and the multi-dimensional NASA-Task Load Index. The cardiac autonomic modulation at rest and in response to stress was assessed by classic indexes of heart rate variability (HRV) as RMSSD and LF/HF ratio. Results showed that: (i) risk-taking behavior correlated with a withdrawal in vagal indices, shifted the baseline sympathovagal balance toward sympathetic predominance (LF/HF ratio r(8) = 0.522, p = 0.01), and increased mean HR both in baseline and during physical exercise (r(8) = 0.526, p = 0.01 and r(8) = 0.445, p = 0.05, respectively); (ii) resilience was associated with higher vagal indices (RMSSD r(18) = 0.288, p = 0.04), and with a baseline sympathovagal balance shifted toward parasympathetic predominance (LF/HF ratio r(18) = −0.289, p = 0.04). Associations of risk-taking behavior and resilience with cardiac autonomic modulation could be demonstrated, showing that HRV may be a valuable monitoring tool in this specific population; however further studies are warranted for validation.

Predictive values of heart rate variability, deceleration and acceleration capacity of heart rate in post-infarction patients with LVEF ≥35

Background and aims

The aim was to investigate the predictive values of heart rate variability, deceleration, and acceleration capacity of heart rate in sudden cardiac death in postinfarction patients with left ventricular ejection fraction (LVEF) ≥ 35%.

Methods

We enrolled 138 acute myocardial infarction patients (MI) randomly in sinus rhythm with LVEF ≥ 35% after myocardial infarction. Data on heart rate variability, deceleration runs, deceleration, and acceleration capacity were obtained from 24h‐dynamic electrocardiogram recordings. Clinical characteristics, medications, and echocardiography data were noted. The endpoints were sudden cardiac arrhythmias (SCA), including malignant arrhythmias in the hospital and viewed sudden death out of the hospital. Relationships between autonomic parameters and endpoints were evaluated.

Results

During follow‐up for over 24 months in MI patients, 10 patients occurred sudden cardiac arrhythmias. Subjects with SCA showed lower levels of SDNN (p = .018), TP (p = .007), VLF (p < .001), DC (p < .001), and low‐risk DRs (p < .001) than those without SCA. A low SDNN level (HR: 8.888, p = .006), low VLF level (HR: 14.699, p = .016), low DC level (HR: 4.430, p = .045), and higher risk DRs (HR: 3.81, p = .040) were identified as independent risk factors of SCA for postinfarction patients with LVEF ≥ 35%. The area under the ROC curve (AUC) of SDNN, VLF, and DC for identification of SCA were, respectively, 0.724 (p = .019), 0.807 (p < .001), and 0.804 (p = .002). SDNN, VLF, and DC combined assessment area under the ROC curve were 0.828 (p < .001).

Conclusion

Decreased SDNN, VLF, DC, and abnormal DRs are independently associated with increased risks of sudden cardiac arrhythmias in post‐MI patients with LVEF ≥ 35%. Combined SDNN, VLF, and DC may help identify a high‐risk group of malignant arrhythmias in postinfarction patients.

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.

Factors associated with musculoskeletal symptoms and heart rate variability among cleaners - cross-sectional study

BACKGROUND

The professionals who perform cleaning activity constitute a major economic sector in Brazil. Cleaners may develop health problems related to the musculoskeletal and cardiovascular systems. It is necessary to understand the working and health conditions of cleaners in Brazil. Thus, the aim of this study was to identify factors associated with musculoskeletal symptoms and heart rate variability (HRV) among cleaners.

METHODS

A cross-sectional study conducted at a public higher education institution with 45 outsourced cleaners following approval from the institutional ethics committee. The participants answered a questionnaire addressing sociodemographic, occupational and health data, the Nordic Musculoskeletal Questionnaire, the Physical Activity Questionnaire (work and leisure) and the short version of the Copenhagen Psychosocial Questionnaire. Clinical data (height, body mass, waist-to-hip ratio and blood pressure) and heart rate variability (HRV) were also collected. Logistic and linear regression models were created to identify factors associated with symptoms and HRV.

RESULTS

The sample consisted of women (100%) predominantly older than 50 years of age (44%), without a conjugal life (64%), with three or more children (59%), low educational level (58%) and who worked less than 12 months at the company (87%). Systemic arterial hypertension (23%) was the most reported health problem. The highest frequency of musculoskeletal symptoms was identified in the lower limbs (ankles/feet: 31% in the previous 12 months and 24% in the previous 7 days; knees: 31% in the previous 12 months and 20% in the previous 7 days). Moreover, the workers reported not practicing physical activity during leisure time (84%). Psychosocial aspects indicated health risks for the dimensions "influence at work" (74%), "burnout" (59%) and "stress" (52%). Associations were found between ankle/foot symptoms and body mass index, shoulder symptoms and predictability, and knee symptoms and self-rated health and burnout. HRV indices were associated with age.

CONCLUSIONS

This study outlined the profile of female cleaners and identified risk factors. The workers exhibited musculoskeletal symptoms, which were associated with the body mass index and some psychosocial factors. HRV indices were associated with age. Thus, health promotion and prevention measures should be taken to benefit this population of workers.

Stress-reducing effects of a brief mindfulness intervention in palliative care: Results from a randomised, crossover study

OBJECTIVE

Mindfulness-based interventions are a widely used and highly accepted adjunct treatment in oncology. Due to a paucity of research in advanced cancer and other terminal illnesses, we aimed to evaluate the stress-reducing effects of a brief, standardised mindfulness intervention for use in palliative care.

METHODS

This study was a randomised, crossover trial where patients participated in both a single mindfulness intervention and a resting state control condition. The order of the conditions was randomised. Study outcomes encompassed self-report data on stress and well-being and measures of heart rate variability. All outcome data were measured at four times per day.

RESULTS

Forty-two patients participated in this study. We found significantly stronger reductions in self-rated stress and mean heart rate as well as an increase in heart rate variability after the mindfulness intervention. Psychophysiological effects were strongest in the immediate pre- to post-intervention comparison, while the effect on subjective stress persisted after 20 to 40 min. No significant differences were found for self-rated well-being.

CONCLUSIONS

Despite the rather small magnitude of effects, the brief mindfulness intervention showed to be effective and accepted by patients in very advanced stages of a disease and could be offered by trained healthcare professionals in palliative care.

Heart Rate Variability is Associated with Memory in Females

Research into the association between heart rate variability (HRV) and cognitive function is scarce, particularly with regard to gender differences. HRV in 182 healthy volunteers was assessed by the root mean square of the successive difference (RMSSD) and spectrum analysis, while the Wechsler Memory Scale-Revised (WMS-R) was used to determine memory function. Robust and significant associations were found to exist between HRV (RMSSD and high-frequency HRV) and domains of the WMS-R in females. Caution should therefore be taken to control for gender when conducting studies on the relationships between HRV and cognitive variables.

Gender-Based Vegetarian and Nonvegetarian Dietary Impact on Cardiac Autonomic Function of Heart Rate Variability

Objective: Cardiovascular disease is one among the major mortality threats throughout the world. Autonomic activity of the nervous system can be examined by heart rate variability (HRV) analysis. Association of sympathetic and parasympathetic activities is directly related to HRV modulation. The aim of the study is to determine variations in HRV parameters among adult/adolescent male and female subjects due to vegetarian and nonvegetarian diet.Method: Ninety undergraduate students in each male and female group (N = 180) volunteered for the study. Based upon food habits, male and female subjects were categorized into four groups. Short-term (5-minute) heart rate recordings were measured from the subjects in a seated position before breakfast with minimum of 12 hours' fasting. Two-way analysis of variance was performed among the time and frequency domain variables.Results: Time domain variables are observed as significant (p < 0.05) between vegetarian males and females and also (p < 0.05) between male vegetarian and female nonvegetarians for standard deviation of NN intervals. Frequency domain HRV indices such as low frequency (LF; p = 0.01), high frequency (HF; p = 0.0001), and LF/HF (p < 0.001) resulted between male and female vegetarians. Significance of LF (p = 0.02), HF (p < 0.0001), and LF/HF (p < 0.01) was measured between male vegetarians and female nonvegetarians. LF (p = 0.02), HF (p = 0.04), and LF/HF (p = 0.002) resulted between nonvegetarian males and females. HF (p = 0.05) was enumerated between male vegetarians and nonvegetarians.Conclusions: Significant predominance of sympathetic cardiac activity was observed among male nonvegetarian consumers more than female vegetarians. Analysis demonstrates that the gender-based influence of vegetarian and nonvegetarian diet has significant correlation under HRV measurements.

Heart rate variability changes in patients with panic disorder

BACKGROUND

This review aimed to evaluate whether patients with panic disorder (PD) exhibit different heart rate variability (HRV) compared to healthy controls and to determine whether HRV is different in patients with PD after treatment.

METHODS

Literature databases were searched for studies comparing resting-state HRV between drug-naïve patients with PD and healthy controls. Parameters from the short-term frequency-domain and long-term time domain were included.

RESULTS

In the low frequency (LF) analysis, no significant association was found between LF and PD (standardised mean difference [SMD] = -0.0443, 95% confidence interval [CI]: -0.1765 to 0.0879). In the high frequency (HF) analysis, no significant association was found between HF and PD (SMD = -0.1269, 95% CI: -0.2598 to 0.0059). In the LF/HF analysis, a significantly higher LF/HF ratio was found in cases than in controls, but the effect was moderate (SMD = 0.1390, 95% CI: 0.0180 to 0.2600). For the standard deviation of normal-to-normal intervals, a significantly lower value was observed in cases than in controls (SMD = -0.3133, 95% CI: -0.5459 to -0.0808).

LIMITATIONS

Limited sample size in the time-domain and treatment effect analyses.

CONCLUSIONS

Patients with PD had a higher short-term LF/HF ratio, indicating impaired sympathovagal balance. The LF/HF ratio findings were more consistent compared with LF and HF alone, making it a better parameter to interpret the LF and HF in conjunction. HRV may be a promising biomarker for predicting antidepressant response.

Yoga in school sports improves functioning of autonomic nervous system in young adults: A non-randomized controlled pilot study

Background

Yoga in school is a beneficial tool to promote the good health and well-being of students by changing the way they react to stress. The positive effects of yoga—taught in schools—on children, youth and young adults have been demonstrated in former studies using mostly subjective psychometric data.

Aim

The present trial aims to evaluate the potential effects of yoga on autonomic regulation in young adults by analyzing heart rate variability (HRV).

Methods

This study is a non-randomized, explorative, two-arm-pilot study with an active control group. Fourteen healthy young adults took part in a 10-week yoga program (90 min once a week) in school and were compared to a control group of 11 students who participated in conventional school sports (90 min once a week over 10 weeks). 24-hour electrocardiograms (ECGs) were recorded at baseline and following the 10-week intervention. From 20-minute of nocturnal sleep phases, HRV parameters were calculated from linear (time and frequency domain) and nonlinear dynamics (such as symbolic dynamics and Poincaré plot analysis). Analyses of variance (ANOVA) followed by t-tests as post-hoc tests estimating both statistical significance and effect size were used to compare pre-post-intervention for the two groups.

Results

The statistical analysis of the interaction effects did not reveal a significant group and time interaction for the individual nocturnal HRV indices. Almost all indices revealed medium and large effects regarding the time main effects. The changes in the HRV indices following the intervention were more dramatic for the yoga group than for the control group which is reflected in predominantly higher significances and stronger effect sizes in the yoga group.

Conclusion

In this explorative pilot trial, an increase of HRV (more parasympathetic dominance and overall higher HRV) after ten weeks of yoga in school in comparison to regular school sports was demonstrated, showing an improved self-regulation of the autonomic nervous system.

Effects of working memory training on cognitive, affective, and biological responses to stress in major depression: A novel cognitive bias modification protocol

BACKGROUND

Over 320 million individuals are living with Major Depressive Disorder (MDD), a leading cause of disability worldwide. Thus, there is a crucial need to identify processes that contribute to the maintenance of depressive episodes. Difficulty removing negative information from working memory (WM) is posited to exacerbate affective, cognitive, and biological dysregulation in Major Depressive Disorder (MDD), but this has not yet been tested empirically.

METHODS

In this study we examined whether training depressed individuals to remove negative information from WM (RNI training) would reduce symptoms of depression and levels of rumination, and would be associated with attenuated biological responsivity to stress. Individuals diagnosed with MDD were randomly assigned to complete Real-RNI training or Sham-RNI training for six days.

RESULTS

Across conditions, participants exhibited significant improvements from pre- to post-training in removing negative information from WM, symptoms of depression, and rumination. Furthermore, participants in the Real-RNI condition showed a more attenuated pattern of cortisol and respiratory sinus arrhythmia (RSA) responses to stress than did participants in the Sham-RNI training condition.

LIMITATIONS

We did not assess the long-term effects of training. It will be important for future research to examine whether the documented training-related effects persist across time.

CONCLUSIONS

This study is the first to examine the effects of RNI training on clinical symptoms and biological responses to stress in MDD, and it provides experimental evidence that training individuals with depression to remove negative information from WM can help to modulate the heightened biological responses to stress seen in depression.

Streamlining Analysis of RR Interval Variability in Elite Soccer Players: Preliminary Experience with a Composite Indicator of Cardiac Autonomic Regulation

It is well recognized that regular physical activity may improve cardiac autonomic regulation preventing chronic non-communicable diseases. Accordingly, the assessment of cardiac autonomic regulation (CAR) with non-invasive techniques, such as RR interval Variability (V) might be of practical interest. We studied 56 soccer players (21.2 ± 4.2 years.) and 56 controls (22.2 ± 1.5 years.) and used a ranked Autonomic Nervous System Index (ANSI), resulting from the combination of multivariate statistical methodologies applied to spectral analysis derived indices from RRV. We hypothesized that ANSI would be higher in soccer players as compared to controls (p < 0.001) and that values would be greatest in defenders and midfielders, who are known to run longer distances during competitions. Conversely in the intrinsically stationary goalkeepers ANSI would be similar to controls. Our data show that it is possible to assess the overall level of autonomic performance in soccer players as compared to the general population, using a ranked composite autonomic proxy (ANSI). This approach suggests as well that CAR is better in those players who during competitions run for a greater distance. We conclude that it is possible to highlight the differences in autonomic profile due to distinct exercise routines, using ANSI, a simple ranked, composite autonomic proxy.

Autonomic Nervous System and Cognitive Impairment in Older Patients: Evidence From Long-Term Heart Rate Variability in Real-Life Setting

Background: In geriatric age, cognitive impairment and cardiovascular disorders are frequent comorbidities. Age-related anatomical and functional cardiac changes, including the autonomic system, could interfere with the control of different cognitive domains. Therefore, we assess the relationship between long-term heart rate variability (HRV), as a measure of autonomic nervous system (ANS) functioning, and cognitive performance in elderly patients representative of outpatients in a real-life setting.

Methods: Of 155 elderly outpatients (aged >65 years) screened, 117 enrolled patients underwent anthropometric evaluation, cardiac assessment by 12-lead electrocardiogram, 24-h ECG recording, and blood pressure (BP) measurement, as well as global cognitive evaluation by a standardized multidimensional assessment, including the Mini-Mental State Examination (MMSE) and Montreal Cognitive Assessment test (MoCA). HRV analysis was performed on 24-h ECG recordings focusing on time-domain indices [Standard deviation of the NN intervals (SDNN), standard deviations of 5-min mean values of the NN intervals for each 5-min interval (SDANN), and root mean squares of successive differences of the NN intervals (RMSSD)] and on frequency-domain measurements [heart rate (HR), low frequency (LF), high frequency (HF), and LF/HF]. Multivariate linear analysis was used to explore the influence of the HRV significant variables on MMSE and MoCA test values.

Results: The MMSE and MoCA scores were both significantly and positively correlated with the sympathetic system parameters (SDNN, SDANN, LF, and LF/HF ratio), but not with the parasympathetic system parameters (RMSSD and HF). Multivariate analysis confirms this relationship.

Conclusions: Our results show that, in a representative real-life community elderly population, an increased sympathetic activity, but not decreased vagal activity, is associated with better cognitive performances. These results support the sympathetic autonomic function, in that the relationship between better cognitive performances and a moderate prevalence of autonomic function appears dependent on long-term changes in heart rate, mediated by sympathetic activation.

Nonlinear Methods Most Applied to Heart-Rate Time Series: A Review

The heart-rate dynamics are one of the most analyzed physiological interactions. Many mathematical methods were proposed to evaluate heart-rate variability. These methods have been successfully applied in research to expand knowledge concerning the cardiovascular dynamics in healthy as well as in pathological conditions. Notwithstanding, they are still far from clinical practice. In this paper, we aim to review the nonlinear methods most used to assess heart-rate dynamics. We focused on methods based on concepts of chaos, fractality, and complexity: Poincaré plot, recurrence plot analysis, fractal dimension (and the correlation dimension), detrended fluctuation analysis, Hurst exponent, Lyapunov exponent entropies (Shannon, conditional, approximate, sample entropy, and multiscale entropy), and symbolic dynamics. We present the description of the methods along with their most notable applications.

Geometric indexes of heart rate variability in healthy individuals exposed to long-term air pollution

The aim of this study was to investigate the autonomic modulation of heart rate in healthy individuals exposed to long-term air pollution through geometric methods. We analyzed data from 109 healthy adults aged 18 to 49, divided into three groups according to the exposure time: period 0 to 15 years of exposure (n = 29), more than 15 years of exposure (n = 31), and control group (n = 49). For the analysis of heart rate variability (HRV), heart rate was recorded beat-to-beat for 20 min in the sitting position. The RR intervals were transformed into geometric indexes, and from them, we calculated the RRTri (triangular index), TINN (triangle interpolation of histogram of intervals NN), and Poincaré plot (SD1, SD2, and SD1/SD2). Significantly lower values were observed in the group of individuals exposed to air pollution for more than 15 years compared with the group of individuals exposed to air pollution for a period of 0-15 years and those not exposed for the RRTri (11.5 vs 13.8 vs 14.0), SD1 (16.4 vs 20.5 vs 20.6), SD2 (60.5 vs 68.1 vs 72.5), and SD1/SD2 (0.27 vs 0.34 vs 0.31), with the effect of this difference being considered large (RRTri), medium (SD1, SD1/SD2), and small (SD2). TINN was not significantly different among groups (198.2 vs 223.1 vs 233.6). Healthy individuals exposed to air pollution for more than 15 years present an autonomic imbalance, characterized by lower parasympathetic modulation and overall HRV.

Reduced heart rate variability predicts fatigue severity in individuals with chronic fatigue syndrome/myalgic encephalomyelitis

Background

Heart rate variability (HRV) is an objective, non-invasive tool to assessing autonomic dysfunction in chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME). People with CFS/ME tend to have lower HRV; however, in the literature there are only a few previous studies (most of them inconclusive) on their association with illness-related complaints. To address this issue, we assessed the value of different diurnal HRV parameters as potential biomarker in CFS/ME and also investigated the relationship between these HRV indices and self-reported symptoms in individuals with CFS/ME.

Methods

In this case–control study, 45 female patients who met the 1994 CDC/Fukuda definition for CFS/ME and 25 age- and gender-matched healthy controls underwent HRV recording-resting state tests. The intervals between consecutive heartbeats (RR) were continuously recorded over three 5-min periods. Time- and frequency-domain analyses were applied to estimate HRV variables. Demographic and clinical features, and self-reported symptom measures were also recorded.

Results

CFS/ME patients showed significantly higher scores in all symptom questionnaires (p < 0.001), decreased RR intervals (p < 0.01), and decreased HRV time- and frequency-domain parameters (p < 0.005), except for the LF/HF ratio than in the healthy controls. Overall, the correlation analysis reached significant associations between the questionnaires scores and HRV time- and frequency-domain measurements (p < 0.05). Furthermore, separate linear regression analyses showed significant relationships between self-reported fatigue symptoms and mean RR (p = 0.005), RMSSD (p = 0.0268) and HFnu indices (p = 0.0067) in CFS/ME patients, but not in healthy controls.

Conclusions

Our findings suggest that ANS dysfunction presenting as increased sympathetic hyperactivity may contribute to fatigue severity in individuals with ME/CFS. Further studies comparing short- and long-term HRV recording and self-reported outcome measures with previous studies in larger CFS/ME cohorts are urgently warranted.

Melatonin Therapy Improves Cardiac Autonomic Modulation in Pinealectomized Patients

The purpose of this investigational study was to assess the effects of melatonin replacement therapy on cardiac autonomic modulation in pinealectomized patients. This was an open-label, single-arm, single-center, proof-of-concept study consisting of a screening period, a 3-month treatment period with melatonin (3 mg/day), and a 6-month washout period. The cardiac autonomic function was determined through heart rate variability (HRV) measures during polysomnography. Pinealectomized patients (n = 5) with confirmed absence of melatonin were included in this study. Melatonin treatment increased vagal-dominated HRV indices including root mean square of the successive R-R interval differences (RMSSD) (39.7 ms, 95% CI 2.0-77.4, p = 0.04), percentage of successive R-R intervals that differ by more than 50 ms (pNN50) (17.1%, 95% CI 9.1-25.1, p = 0.003), absolute power of the high-frequency band (HF power) (1,390 ms², 95% CI 511.9-2,267, p = 0.01), and sympathetic HRV indices like standard deviation of normal R-R wave interval (SDNN) (57.6 ms, 95% CI 15.2-100.0, p = 0.02), and absolute power of the low-frequency band (LF power) (4,592 ms², 95% CI 895.6-8,288, p = 0.03). These HRV indices returned to pretreatment values when melatonin treatment was discontinued. The HRV entropy-based regularity parameters were not altered in this study, suggesting that there were no significant alterations of the REM-NREM ratios between the time stages of the study. These data show that 3 months of melatonin treatment may induce an improvement in cardiac autonomic modulation in melatonin-non-proficient patients. ClinicalTrials.gov Identifier: NCT03885258.

The Effect of the Menstrual Cycle on Daily Measures of Heart Rate Variability in Athletic Women

Abstract. Heart rate variability (HRV) is a biomarker used to reflect both healthy and pathological state(s). The effect of the menstrual cycle and menstrual cycle phases (follicular, luteal) on HRV remains unclear. Active eumenorrheic women free from exogenous hormones completed five consecutive weeks of daily, oral basal body temperature (BBT) and HRV measurements upon waking. Descriptive statistics were used to characterize shifts in the HRV measures: standard deviation of NN intervals (SDNN), root mean square of successive difference (rMSSD), high (HF) and low frequency (LF) across the menstrual cycle and between phases. All HRV measures were assessed by medians ( Mdn), median difference of consecutive days ( Mdn∆) and variance. Seven participants ( M ±  SD; age: 28.60 ± 8.40 year) completed the study with regular menstrual cycles (28.40 ± 2.30 days; ovulation day 14.57 ± 0.98 day). Median rMSSD displayed a nonlinear decrease across the menstrual cycle and plateau around the day of ovulation. A negative shift before ovulation in Mdn∆, rMSSD, SDNN, and LF as well as peak on luteal phase Day 4 in rMSSD and SDNN was observed. Median variance increased in rMSSD (150.06 ms2) SDNN (271.12 ms2), and LF variance (0.001 sec2/Hz) from follicular to luteal phase. Daily HRV associated with the parasympathetic nervous system was observed to decrease nonlinearly across the menstrual cycle.

Stress and Depressive Symptoms Among Demographically Diverse American Pregnant Women

Pregnancy is a sensitive period of life where mental health is of utmost importance to the mother's and child's well-being peripartum and beyond. To better prevent and treat common mental health conditions such as depressive symptoms and perceived stress (defined in this study to encompass psychological and physiological (heart rate variability (HRV)) dimensions), it is crucial to examine and report differences in mental health outcomes among demographically diverse pregnant women. Therefore, the purpose of this secondary analysis (N = 79) was to determine if there are differences in mental health outcomes between pregnant women who differ across demographic factors, as well as to determine if demographic factors predict mental health outcomes when controlling for other demographic variables. Findings indicate that there were significant differences in depressive symptoms and perceived stress by all demographic factors except age. Marital status and total household income were the only significant predictors of depressive symptoms and perceived stress, respectively, when all other factors were controlled. There were no significant differences or correlations between demographic variables and HRV. Pregnant women may be predisposed to adverse mental health outcomes, illustrating the need for more refined interventions that are sensitive to pre-existing factors.

Comparison of methods for the assessment of nonlinearity in short-term heart rate variability under different physiopathological states

Despite the widespread diffusion of nonlinear methods for heart rate variability (HRV) analysis, the presence and the extent to which nonlinear dynamics contribute to short-term HRV are still controversial. This work aims at testing the hypothesis that different types of nonlinearity can be observed in HRV depending on the method adopted and on the physiopathological state. Two entropy-based measures of time series complexity (normalized complexity index, NCI) and regularity (information storage, IS), and a measure quantifying deviations from linear correlations in a time series (Gaussian linear contrast, GLC), are applied to short HRV recordings obtained in young (Y) and old (O) healthy subjects and in myocardial infarction (MI) patients monitored in the resting supine position and in the upright position reached through head-up tilt. The method of surrogate data is employed to detect the presence and quantify the contribution of nonlinear dynamics to HRV. We find that the three measures differ both in their variations across groups and conditions and in the percentage and strength of nonlinear HRV dynamics. NCI and IS displayed opposite variations, suggesting more complex dynamics in O and MI compared to Y and less complex dynamics during tilt. The strength of nonlinear dynamics is reduced by tilt using all measures in Y, while only GLC detects a significant strengthening of such dynamics in MI. A large percentage of detected nonlinear dynamics is revealed only by the IS measure in the Y group at rest, with a decrease in O and MI and during T, while NCI and GLC detect lower percentages in all groups and conditions. While these results suggest that distinct dynamic structures may lie beneath short-term HRV in different physiological states and pathological conditions, the strong dependence on the measure adopted and on their implementation suggests that physiological interpretations should be provided with caution.

Sex differences in neuropathy & neuropathic pain: A brief report from the Phase 2 Canadian Study of Longevity in Type 1 Diabetes

To evaluate previous results from a questionnaire-based study, we studied objective neuropathy measures to determine sex differences in the prevalence of neuropathy and neuropathic pain in longstanding type 1 diabetes. Despite better neuropathy measures in females compared to males, we confirmed a trend towards higher neuropathic pain in females.

Cardioprotective effect of transcutaneous electrical acupuncture point stimulation on perioperative elderly patients with coronary heart disease: a prospective, randomized, controlled clinical trial

Purpose

The purpose of this study was to evaluate the effects of transcutaneous electrical acupoint stimulation (TEAS) on postoperative autonomic nervous system function and serum biomarkers in the elderly.

Patients and methods

A total of 122 American Society of Anesthesiologists class II or III patients with coronary heart disease undergoing spinal surgery were randomly divided into two groups: TEAS (received TEAS at Neiguan [PC6] and Ximen [PC4] for 30 minutes before anesthesia induction until the end of surgery) and control (received electrode plate at the same acupuncture points without any electrical stimulation). Serum was isolated for the measurement of concentration of high-sensitive troponin T (hs-cTnT), CRP, and CK. Heart rate (HR) and heart rate variability (HRV) including: total power (TP), low-frequency (LF) power, high-frequency (HF) power, and LF/HF ratio were used to assess autonomic nervous system function. The primary outcome was to evaluate whether TEAS changed the postoperative serum hs-cTnT. The secondary outcomes were to observe the effects of TEAS on HRV, circulating CK and CRP after surgery.

Results

Hs-cTnT, CRP, and CK concentrations were significantly higher on first, third and fifth day after surgery than those before anesthesia induction in both groups. Hs-cTnT concentration was significantly lower on the first and third day after surgery in TEAS group than in control group. Compared with 1 day before surgery, TP, LF, and HF decreased significantly and HR, LF/HF increased significantly on first, third, and fifth day after surgery in control group. Compared with control group, HR was significantly lower on the first, third, and fifth day after surgery, LF/HF decreased and TP, LF, HF were significantly higher on the first day after surgery in TEAS group.

Conclusion

TEAS at PC6 and PC4 could reduce postoperative serum hs-cTnT concentration and change HRV index to improve autonomic nervous system activity.

Presence of age- and sex-related differences in heart rate variability despite the maintenance of a suitable level of accelerometer-based physical activity

There is currently a lack of information adjacent on the influence of sex and age in heart rate variability (HRV), adjusted according to accelerometer-based physical activity (PADL). We hypothesized that the effect of sex and age on the HRV should be reduced or absent in individuals with a suitable PADL level. We aim to evaluate the influence of sex and age on HRV, adjusted for the confounding effects of the PADL level. A total of 485 age-stratified subjects (18–39, 40–59, and ≥60 years) underwent HRV analyses at rest and 7-day assessments of accelerometer-based PADL. Multivariate analyses of covariance were done using log-transformed HRV indices as outcomes, age and sex as fixed factors, and PADL, cardiovascular risk, fat body mass, and heart rate (HR) at rest as covariates. Despite the adjustment for directly measured PADL, women had better indices of vagal tone, whereas men had higher sympathetic influence. Also, compared to middle-aged and older adults, younger individuals (ages 18–39 years) presented better HRV. Multiple regression analyses confirmed that age and sex were the main predictors of HRV indices, even after adjusting for PADL directly assessed by triaxial accelerometer and HR. We also observed that the correlation between some HRV indexes and the different indexes of physical activity directly evaluated was significant, but not very consistent. Thus, HRV indices are influenced by age and sex, regardless of accelerometer-based physical activity. Interventions with physical activity and exercise aimed at improving the autonomic modulation of asymptomatic adults should take such differences into account.

Resting Cardiac Vagal Tone is Associated with Long-Term Frustration Level of Mental Workload: Ultra-short Term Recording Reliability

Excessive mental workload represent a critical risk factor for workplace accidents. Heart rate variability (HRV) is a non-invasive low cost electrophysiological autonomic biomarker related to emotional and cognitive regulation. Several studies report that mental overload impairs parasympathetic-mediated HRV indices (e.g. rMSSD). However, the influence of resting state HRV as a predictor of long-term mental workload impairments remains unknown. Thirty participants (22 males; 8 females) had their HRV measured (5-min period) before performing the number search task. After the task, the mental load was accessed by the NASA-TLX questionnaire. A simple linear regression model between HRV and NASA-TLX dimensions showed that resting state rMSSD is associated to physical demand (ND-2, R² = 0.143, p = 0.03) and frustration level (ND-6, R² = 0.175, p = 0.02) dimensions of mental workload. The comparison between 1 and 5-min epochs suggests that regression models remain reliable even using the ultra-short term HRV (< 1 min) recording values (R² values from 0.11 to 0.15 for ND-2 and R² values from 0.16 to 0.19 for ND-6). These results suggest that resting state HRV is associated to long-term effects of mental workload on physical and emotional demands. In addition, the ultra-short term HRV indices remains reliable to assess ND-2 and ND-6 dimensions of mental workload when compared to gold-standard time interval (> 5 min). The resting state cardiac autonomic tone assessment optimizes the physiological approach with a quick, non-invasive and low-cost assessment that can provide insights about mental load adjustments to prevent work-related accidents.

Risk Stratification in Idiopathic Dilated Cardiomyopathy Patients Using Cardiovascular Coupling Analysis

Cardiovascular diseases are one of the most common causes of death; however, the early detection of patients at high risk of sudden cardiac death (SCD) remains an issue. The aim of this study was to analyze the cardio-vascular couplings based on heart rate variability (HRV) and blood pressure variability (BPV) analyses in order to introduce new indices for noninvasive risk stratification in idiopathic dilated cardiomyopathy patients (IDC). High-resolution electrocardiogram (ECG) and continuous noninvasive blood pressure (BP) signals were recorded in 91 IDC patients and 49 healthy subjects (CON). The patients were stratified by their SCD risk as high risk (IDC_HR) when after two years the subject either died or suffered life-threatening complications, and as low risk (IDC_LR) when the subject remained stable during this period. Values were extracted from ECG and BP signals, the beat-to-beat interval, and systolic and diastolic blood pressure, and analyzed using the segmented Poincaré plot analysis (SPPA), the high-resolution joint symbolic dynamics (HRJSD) and the normalized short time partial directed coherence methods. Support vector machine (SVM) models were built to classify these patients according to SCD risk. IDC_HR patients presented lowered HRV and increased BPV compared to both IDC_LR patients and the control subjects, suggesting a decrease in their vagal activity and a compensation of sympathetic activity. Both, the cardio -systolic and -diastolic coupling strength was stronger in high-risk patients when comparing with low-risk patients. The cardio-systolic coupling analysis revealed that the systolic influence on heart rate gets weaker as the risk increases. The SVM IDC_LR vs. IDC_HR model achieved 98.9% accuracy with an area under the curve (AUC) of 0.96. The IDC and the CON groups obtained 93.6% and 0.94 accuracy and AUC, respectively. To simulate a circumstance in which the original status of the subject is unknown, a cascade model was built fusing the aforementioned models, and achieved 94.4% accuracy. In conclusion, this study introduced a novel method for SCD risk stratification for IDC patients based on new indices from coupling analysis and non-linear HRV and BPV. We have uncovered some of the complex interactions within the autonomic regulation in this type of patient.

Low levels of dehydroepiandrosterone sulfate are associated with the risk of developing cardiac autonomic dysfunction in elderly subjects

OBJECTIVE

To assess the relationships between serum dehydroepiandrosterone sulfate (DHEA-S) levels and heart rate variability (HRV) among different age groups.

SUBJECTS AND METHODS

Forty-five healthy men were divided into 3 groups: young age (YA; 20-39 yrs; n = 15), middle age (MA; 40-59 yrs; n = 15) and old age (OA; ≥ 60 yrs; n = 15). Hemodynamic parameters, linear analyses of HRV and concentrations of cortisol and DHEA-S were measured at rest.

RESULTS

The OA group presented a higher resting heart rate (84.3 ± 4.6 bpm) than the YA group (72.0 ± 4.4 bpm; p < 0.05). The YA group showed an attenuated variance of HRV (2235.1 ± 417.9 ms2) compared to the MA (1014.3 ± 265.2 ms2; p < 0.05) and OA (896.3 ± 274.1 ms2; p < 0.05) groups, respectively. The parasympathetic modulation of HRV was lower in both the MA (244.2 ± 58.0 ms2) and OA (172.8 ± 37.9 ms2) groups in comparison with the YA group (996.0 ± 255.4 ms2; p < 0.05), while serum DHEA-S levels were significantly lower in both the MA (91.2 ± 19.6 mg/dL) and OA (54.2 ± 17.7 mg/dL) groups compared to the YA group (240.0 ± 50.8 mg/dL; p < 0.05). A positive correlation between lower serum concentrations of DHEA-S and attenuated variance of HRV (r = 0.47, p = 0.031), as well as lower serum concentrations of DHEA-S and decreased parasympathetic modulation of HRV (r = 0.54, p = 0.010), were found.

CONCLUSION

The present study demonstrated that the decline of plasma DHEA-S is associated with reduced cardiac autonomic modulation during the aging process.

Spectral Analysis of Heart Rate Variability: Time Window Matters

Spectral analysis of heart rate variability (HRV) is a valuable tool for the assessment of cardiovascular autonomic function. Fast Fourier transform and autoregressive based spectral analysis are two most commonly used approaches for HRV analysis, while new techniques such as trigonometric regressive spectral (TRS) and wavelet transform have been developed. Short-term (on ECG of several minutes) and long-term (typically on ECG of 1–24 h) HRV analyses have different advantages and disadvantages. This article reviews the characteristics of spectral HRV studies using different lengths of time windows. Short-term HRV analysis is a convenient method for the estimation of autonomic status, and can track dynamic changes of cardiac autonomic function within minutes. Long-term HRV analysis is a stable tool for assessing autonomic function, describe the autonomic function change over hours or even longer time spans, and can reliably predict prognosis. The choice of appropriate time window is essential for research of autonomic function using spectral HRV analysis.

Differentiation of Heart Failure Patients by the Ratio of the Scaling Exponents of Cardiac Interbeat Intervals

Heart failure (HF) is one of the most frequent heart diseases. It is usually characterized with structural and functional cardiac abnormalities followed by dysfunction of autonomic cardiac control. Current methods of heartbeat interval analysis are not capable to differentiate HF patients and some new differentiation of HF patients could be useful in the determination of the direction of their treatment. In this study, we examined potential of the ratio of the short-term and long-term scaling exponents (α 1 and α 2) to separate HF patients with similar level of reduced cardiac autonomic nervous system control and with no significant difference in age, left ventricular ejection fraction (LVEF) and NYHA class. Thirty-five healthy control subjects and 46 HF patients underwent 20 min of continuous supine resting ECG recording. The interbeat interval time series were analyzed using standardized power spectrum analysis, detrended fluctuation analysis method and standard Poincaré plot (PP) analysis with measures of asymmetry of the PP. Compared with healthy control group, in HF patients linear measures of autonomic cardiac control were statistically significantly reduced (p < 0.05), heart rate asymmetry was preserved (C up > C down, p < 0.01), and long-term scaling exponent α 2 was significantly higher. Cluster analysis of the ratio of short- and long-term scaling exponents showed capability of this parameter to separate four clusters of HF patients. Clusters were determined by interplay of presence of short-term and long-term correlations in interbeat intervals. Complementary measure, commonly accepted ratio of the PP descriptors, SD2/SD1, showed tendency toward statistical significance to separate HF patients in obtained clusters. Also, heart rate asymmetry was preserved only in two clusters. Finally, a multiple regression analysis showed that the ratio α 1/α 2 could be used as an integrated measure of cardiac dynamic with complex physiological background which, besides spectral components as measures of autonomic cardiac control, also involves breathing frequency and mechanical cardiac parameter, left ventricular ejection fraction.

The Pulse-Respiration Quotient: A Powerful but Untapped Parameter for Modern Studies About Human Physiology and Pathophysiology

A specific and unique aspect of cardiorespiratory activity can be captured by dividing the heart rate (HR) by the respiration rate (RR), giving the pulse-respiration quotient (PRQ = HR/RR). In this review article, we summarize the main findings of studies using and investigating the PRQ. We describe why the PRQ is a powerful parameter that captures complex regulatory states of the cardiorespiratory system, and we highlight the need to re-introduce the use of this parameter into modern studies about human physiology and pathophysiology. In particular, we show that the PRQ (i) changes during human development, (ii) is time-dependent (ultradian, circadian, and infradian rhythms), (iii) shows specific patterns during sleep, (iv) changes with physical activity and body posture, (v) is linked with psychophysical and cognitive activity, (vi) is sex-dependent, and (vii) is determined by the individual physiological constitution. Furthermore, we discuss the medical aspects of the PRQ in terms of applications for disease classification and monitoring. Finally, we explain why there should be a revival in the use of the PRQ for basic research about human physiology and for applications in medicine, and we give recommendations for the use of the PRQ in studies and medical applications.

Early Detection of Hypoglycemia in Type 1 Diabetes Using Heart Rate Variability Measured by a Wearable Device

OBJECTIVE

Changes in heart rate variability (HRV) occur at the initiation of hypoglycemia due to sympathetic nervous system activity. We investigated the use of HRV detection by a wearable device as an early alert for hypoglycemia.

RESEARCH DESIGN AND METHODS

This proof-of-principle study included 23 patients with type 1 diabetes (14 women, mean age 42 ± 11 years). Patients wore a VitalConnect HealthPatch for 5 days. Hypoglycemia was defined as glucose ≤70 mg/dL (≤3.9 mmol/L) by fingerstick measurement. HRV was analyzed in standardized periods before the hypoglycemic event.

RESULTS

Sixty-six hypoglycemic events were recorded. Hypoglycemia caused a typical HRV pattern in 36 (55%) of the hypoglycemic events. Eighteen events (27%) showed an atypical pattern. Ten events were unclassified (15%), and two did not display a change in HRV (3%).

CONCLUSIONS

Hypoglycemia causes early changes in HRV that can be detected by a wearable device. Measuring real-time HRV seems promising for early hypoglycemia detection.