Heart Rate Variability in Healthy Non-Concussed Youth Athletes: Exploring the Effect of Age, Sex, and Concussion-Like Symptoms

Heart Rate Variability in Concussed College Athletes: Follow-Up Study and Biological Sex Differences

Finding reliable biomarkers to assess concussions could play a pivotal role in diagnosis, monitoring, and predicting associated risks. The present study aimed to explore the use of heart rate variability (HRV) in the follow-up of concussions among college athletes and to investigate the relationships between biological sex, symptomatology, and HRV values at baseline and after a concussion. Correlations between measures were also analyzed. A total of 169 (55 females) athletes aged 16 to 22 years old completed baseline testing, and 30 (8 females) concussion cases were followed. Baseline assessment (T1) included psychosocial and psychological questionnaires, symptoms report, and four minutes of HRV recording. In the event of a concussion, athletes underwent re-testing within 72 h (T2) and before returning to play (T3). Baseline findings revealed that girls had higher %VLF while sitting than boys, and a small negligible correlation was identified between %HF and total symptoms score as well as %HF and affective sx. Post-concussion analyses demonstrated a significant effect of time × position × biological sex for %HF, where girls exhibited higher %HF at T3. These findings suggest disruptions in HRV following a concussion and underscore biological sex as an important factor in the analysis of HRV variation in concussion recovery trajectory.

An Evaluation of the Emerging Techniques in Sports-Related Concussion

SUMMARY

Sports-related concussion is now in public awareness more than ever before. Investigations into underlying pathophysiology and methods of assessment have correspondingly increased at an exponential rate. In this review, we aim to highlight some of the evidence supporting emerging techniques in the fields of neurophysiology, neuroimaging, vestibular, oculomotor, autonomics, head sensor, and accelerometer technology in the setting of the current standard: clinical diagnosis and management. In summary, the evidence we reviewed suggests that (1) head impact sensors and accelerometers may detect possible concussions that would not otherwise receive evaluation; (2) clinical diagnosis may be aided by sideline vestibular, oculomotor, and portable EEG techniques; (3) clinical decisions on return-to-play eligibility are currently not sensitive at capturing the neurometabolic, cerebrovascular, neurophysiologic, and microstructural changes that biomarkers have consistently detected days and weeks after clinical clearance. Such biomarkers include heart rate variability, quantitative electroencephalography, as well as functional, metabolic, and microstructural neuroimaging. The current challenge is overcoming the lack of consistency and replicability of any one particular technique to reach consensus.

Heart Rate Variability as a Reliable Biomarker Following Concussion: A Critically Appraised Topic

CLINICAL SCENARIO

Recent systematic reviews show conflicting information regarding the effect of concussion on cardiac autonomic function. Controlled aerobic exercise is the most popular intervention for those recovering from a concussion. There is a gap in the literature supporting the utility of objective metrics during exertional return to play protocols and rehabilitation.

CLINICAL QUESTION

Can heart rate variability (HRV) during physical exertion be a reliable biomarker over time for those who suffered a sport-related concussion?

SUMMARY OF KEY FINDINGS

A literature search produced 3 studies relevant to the clinical question. One, a prospective-matched control group cohort study, reported disturbances in HRV during physical exertion in those with a history of concussion, and identified persistent HRV dysfunction after resolution of subjective complaints, return to play, and with multiple concussive events. Second, a cross-sectional cohort study found an HRV difference in those with and without a history of concussion and in HRV related to age and sex. Finally, the prospective longitudinal case-control cohort study did not find sex or age differences in HRV and concluded that, although postconcussion HRV improved as time passed, resting HRV was not as clinically meaningful as HRV during exertional activities.

CLINICAL BOTTOM LINE

There is emerging evidence to support the use of HRV as an observable biomarker, over time, of autonomic function during physical exertion following a sport-related concussion. However, the meaningfulness of HRV data is not fully understood and the utility seems individualized to the level of athlete, age, and sex and, therefore, cannot be generalizable. In order to be more clinically meaningful and to assist with current clinical decision making regarding RTP, a preinjury baseline assessment would be beneficial as an individualized reference for baseline comparison.

STRENGTH OF RECOMMENDATION

Although HRV is not fully understood, currently, there is grade B evidence to support the use of individualized baseline exertional HRV data as comparative objective metric to assess the autonomic nervous system function, over time, following a concussive event.

Unclear outcomes of heart rate variability following a concussion: a systematic review

PURPOSE

: To systematically regroup articles that were published since the latest systematic search, but with specific inclusion criteria to help comparison that will offer a focused presentation of methods and results. This will offer a full overview of HRV's behavior at rest and during exercise in adults post-concussion.

METHODS

: The systematic review was conducted using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) method. A computer-based systematic search was conducted in December 2019 through the Pubmed, Scopus and SPORTDiscus databases. A manual search was performed through the reference list of all articles retained. The reliability of the systematic search was assured by having the article selection process entirely repeated by a second author.

RESULTS

: The systematic search yielded a total of 15 articles to be further analyzed. Results show impairment of HRV during exercise for individuals with concussion, heterogenous studies with lack of control over confounding factors and only less than half of the results showing a significant difference between individuals with concussion and controls.

CONCLUSION

: Further research should try standardizing HRV measurement protocols that control confounding factors to allow easier comparison between studies and allows the possibility for an eventual meta-analysis.

Nutritional Neuroscience as Mainstream of Psychiatry: The Evidence- Based Treatment Guidelines for Using Omega-3 Fatty Acids as a New Treatment for Psychiatric Disorders in Children and Adolescents

Omega-3 polyunsaturated fatty acids (or omega-3 PUFAs, n-3 PUFAs) are essential nutrients throughout the life span. Recent studies have shown the importance of n-3 PUFAs supplementation during prenatal and perinatal period as a potential protective factor of neurodevelopmental disorders. N-3 PUFAs have been reported to be lower in youth with attention deficit hyperactivity disorder (ADHD), autism spectrum disorder (ASD) and major depressive disorder (MDD). N-3 PUFAs supplementation has shown potential effects in the improvement of clinical symptoms in youth with ADHD, ASD, and MDD, especially those with high inflammation or a low baseline n-3 index. Moreover, it has been suggested that n-3 PUFAs had positive effects on lethargy and hyperactivity symptoms in ASD. For clinical application, the following dosage and duration are recommended in youth according to available randomized controlled trials and systemic literature review: (1) ADHD: a combination of eicosapentaenoic acid (EPA) + docosahexaenoic acid (DHA) ≥ 750 mg/d, and a higher dose of EPA (1,200 mg/d) for those with inflammation or allergic diseases for duration of 16−24 weeks; (2) MDD: a combination of a EPA + DHA of 1,000−2,000 mg/d, with EPA:DHA ratio of 2 to 1, for 12−16 weeks; (3) ASD: a combination of EPA + DHA of 1,300−1,500 mg/d for 16−24 weeks as add-on therapy to target lethargy and hyperactivity symptoms. The current review also suggested that n-3 index and inflammation may be potential treatment response markers for youth, especially in ADHD and MDD, receiving n-3 PUFA.

Self-efficacy in non-concussed youth: a normative study

OBJECTIVE

In pediatric concussion, there has been a shift to consider how pre-injury profiles, such as self-efficacy, affect the recovery trajectory. The aim of this study was to investigate normal ranges of self-efficacy (overall, academic, social, emotional) in youth and to explore its relationship with the effects of daily stressors, operationalized as concussion-like symptoms, demographic factors, pre-injury/learning related factors, and concussion history.

METHODS

A cross-sectional study of 1300 uninjured youth 13-18 years old (1111 males, 189 females) was conducted by secondary analysis of clinical pre-injury/baseline concussion data. Demographic information, concussion-like symptoms (Post-concussion Symptom Inventory), and self-efficacy (Self-efficacy Questionnaire for Children) were self-reported.

RESULTS

The most reported concussion-like symptoms were common stress symptoms and there was a strong negative relationship with self-efficacy. Males reported higher self-efficacy than females, but no age effects were observed. Pre-injury factors including learning disability, ADHD, special education, IEP, mental health challenges, history of headaches/migraines, and concussion history were associated with significantly lower overall self-efficacy.

CONCLUSIONS

These normative ranges and predictive model can be used to provide a benchmark of self-efficacy to indicate how youth may respond to a concussion, and to inform clinical care during recovery.

The association between cardiac autonomic neuropathy and diabetes control

Introduction: Cardiac autonomic neuropathy (CAN) is one of major complications of diabetes mellitus (DM) that increases the risk of cardiovascular disorders, abnormal ventricular depolarization with poor prognosis as well as increased mortality and morbidity. Indeed, CAN has close relation with blood glucose level in diabetic patients. We investigated the relation of CAN with diabetes control. Materials and methods: Totally, 115 diabetic patients (mean age 50.87±13.90 years old; 78 females) underwent study. All patients had DM and cardiac sinus rhythm. Nobody had sickness affecting cardiac rhythm and blood pressure. In addition, they did not take drugs that had effect on blood pressure, cardiac rhythm, and QT interval. Forty-six patients had tight and 69 patients had uncontrolled DM according to American Diabetes Association (ADA) criteria. The CAN was assessed based on heart rate variation during physical examination (at rest tachycardia and orthostatic hypotension) and standard Ewing's tests (deep-breathing and laying-to-standing tests) with bedside continuous ECG recording. The P-value <0.05 is considered significant. Results: Seventy-five patients (65.2%) had CAN. In patients with CAN, 13.9% were symptomatic and 51.3% were asymptomatic. Resting tachycardia and hypotension were found in 5.2%, 8.7% of patients, respectively. Abnormal deep-breathing and laying-to-standing tests were found in 73% and 71.3% of asymptomatic patients, respectively. CAN was more prevalence at uncontrolled DM (67.3% vs 63.7%) but the difference was not significant. The prevalence of CAN had direct association with duration of DM in both tight and uncontrolled groups (P<0.05). The mean of age, sex, and type of treatment had no association with CAN prevalence. Conclusion: The prevalence of CAN, especially asymptomatic type, was high. Its prevalence was increased with prolonged duration of DM. But we did not find any relationship between CAN and glycemic control level.

Heart rate variability following youth concussion: how do autonomic regulation and concussion symptoms differ over time postinjury?

OBJECTIVES

Following youth concussion, objective physiological indicators are needed to corroborate changes in subjective clinical measures. The objectives of the current study were to: (1) explore the effect of concussion on heart rate variability (HRV) across days postinjury in youth athletes aged 13-18 years old, compared with healthy age-matched and sex-matched controls and (2) examine the relationship between postconcussion symptom domains (physical, cognitive, fatigue and emotional) and HRV.

METHODS

Prospective, longitudinal, case-control study (N=44). This study comprised 29 concussed athletes between the ages of 13 and 18 years old (21 females, 8 males) and 15 age-matched and sex-matched controls). All participants completed baseline testing, which included demographic information (age, sex, concussion history), self-reported concussion symptoms (Post-Concussion Symptom Inventory [PCSI]) and a 24-hour heart rate recording via the Polar RS800CX system. The PCSI and HRV were collected weekly while the participant was symptomatic and then 1, 3 and 6 months following symptom resolution. HRV variables included time and frequency domain measures. Data visualisations and mixed effects modelling were used to derive parsimonious models.

RESULTS

HRV increased across days postinjury. Concussion symptom domains (physical, cognitive, fatigue and emotional) all had a significant main effect on HRV; concussed participants who reported more symptoms had higher HRV compared with those who reported fewer symptoms. Visualisations of HRV depict the recovery trajectory as non-linear across time. No significant differences on HRV measures were found between concussed and control participants.

CONCLUSION

These preliminary findings provide the foundation to understand the varied trajectory and relationship between objective physiological measures and subjective symptom reporting.

Autonomic Function Following Concussion in Youth Athletes: An Exploration of Heart Rate Variability Using 24-hour Recording Methodology

Participation in organized sports makes a significant contribution to youth development, but places youth at a higher risk for sustaining a concussion. To date, return-to-activity decision-making has been anchored in the monitoring of self-reported concussion symptoms and neurocognitive testing. However, multi-modal assessments that corroborate objective physiological measures with traditional subjective symptom reporting are needed and can be valuable. Heart rate variability (HRV) is a non-invasive physiological indicator of the autonomic nervous system, capturing the reciprocal interplay between the sympathetic and parasympathetic nervous systems. There is a dearth of literature exploring the effect of concussion on HRV in youth athletes, and developmental differences preclude the application of adult findings to a pediatric population. Further, the current state of HRV methodology has primarily included short-term (5-15 min) recordings, by using resting state or short-term physical exertion testing to elucidate changes following concussion. The novelty in utilizing a 24 h recording methodology is that it has the potential to capture natural variation in autonomic function, directly related to the activities a youth athlete performs on a regular basis. Within a prospective, longitudinal research setting, this novel approach to quantifying autonomic function can provide important information regarding the recovery trajectory, alongside traditional self-report symptom measures. Our objectives regarding a 24 h recording methodology were to (1) evaluate the physiological effects of a concussion in youth athletes, and (2) describe the trajectory of physiological change, while considering the resolution of self-reported post-concussion symptoms. To achieve these objectives, non-invasive sensor technology was implemented. The raw beat-to-beat time intervals captured can be transformed to derive time domain and frequency domain measures, which reflect an individual's ability to adapt and be flexible to their ever-changing environment. By using non-invasive heart rate technology, autonomic function can be quantified outside of a traditional controlled research setting.

Highly sensitive index of cardiac autonomic control based on time-varying respiration derived from ECG

Frequency-domain indices of heart rate variability (HRV) have been used as markers of sympathovagal balance. However, they have been shown to be degraded by interindividual or task-dependent variability, and especially variations in breathing frequency. The study introduces a method to analyze respiration-(vagally) mediated HRV, to better assess subtle variations in sympathovagal balance using ECG recordings. The method enhances HRV analysis by focusing the quantification of respiratory sinus arrhythmia (RSA) gain on the respiratory frequency. To this end, instantaneous respiratory frequency was obtained with ECG-derived respiration (EDR) and was used for variable frequency complex demodulation (VFCDM) of R-R intervals to extract RSA. The ability to detect cognitive stress in 27 subjects (athletes and nonathletes) was taken as a quality criterion to compare our method to other HRV analyses: Root mean square of successive differences, Fourier transform, wavelet transform, and scaling exponent. Three computer-based tasks from MATB-II were used to induce cognitive stress. Sympathovagal index (HF_nu) computed with our method better discriminates cognitive tasks from baseline, as indicated by P values and receiver operating characteristic curves. Here, transient decreases in respiratory frequency have shown to bias classical HRV indices, while only EDR-VFCDM consistently exhibits the expected decrease in the HF_nu index with cognitive stress in both groups and all cognitive tasks. We conclude that EDR-VFCDM is robust against atypical respiratory profiles, which seems relevant to assess variations in mental demand. Given the variety of individual respiratory profiles reported especially in highly trained athletes and patients with chronic respiratory conditions, EDR-VFCDM could better perform in a wide range of applications.