Nocturnal Heart Rate Variability Research Articles

Analysis of Sleep, Nocturnal Physiology, and Physical Demands of NCAA Women's Ice Hockey Across a Championship Season.

Merrigan, JJ, Stone, JD, Kraemer, WJ, Friend, C, Lennon, K, Vatne, EA, and Hagen, JA. Analysis of sleep, nocturnal physiology, and physical demands of NCAA women's ice hockey across a championship season. J Strength Cond Res 38(4): 694-703, 2024-The aims of this study were to evaluate the (a) relationships between daily physical demands and nighttime sleep, heart rate (HR), and heart rate variability (HRV); (b) weekly changes in physical demands and sleep; and (c) differences among positions and between training and competition during a competitive season in National Collegiate Athletic Association (NCAA) women's ice hockey. Twenty-five NCAA Division I women's ice hockey athletes wore a sensor at night to monitor sleep quantity or quality (e.g., time asleep and sleep efficiency) and physiology (e.g., HR and HRV). During training and competitions (31 regular season and 7 postseason), athletes wore performance monitoring systems to assess workload demands (e.g., training impulse and TRIMP). As internal workload (TRIMP, Time >80% of HRmax, Average HR) during training or competition increased, nocturnal HRV decreased, HR increased, and Sleep Duration, Sleep Score, and Readiness Score decreased that night. Across the season, athletes experienced lower HRV, but exhibited longer sleep durations. Training Distance, Duration, Time >80% HRmax, Average HR, and TRIMP decreased, whereas competition Total Distance, Duration, and TRIMP increased across weeks throughout the season. There were differences across positions and season blocks when evaluating these data at the mesocycle level. Athletes slept longer before competition compared with training, but physiological data did not differ. Competitions had greater physiological demands than training. We speculate that the increased focus on sleep hygiene, as evidenced by the increase in sleep over the season, may have served as a recovery aid to combat physiological stress of accumulated demands of competitions that increased over time into postseason tournaments.

EFFECTS OF A SINGLE EVENING VINYASA YOGA SESSION ON SLEEP IN ADULTS WITH INSOMNIA SYMPTOMS

BACKGROUND Vinyasa yoga (VY), a form of yoga that links breath with movement and has higher energy expenditure perhaps than most other types of yoga, has been sparsely studied for its effects on sleep among adults with insomnia. It remains unknown whether and how an acute bout of VY performed in the evening impacts sleep and autonomic function. The purpose of this study it to examine the effects of an acute session of VY performed in the evening on sleep and nocturnal heart rate variability (HRV) in adults with insomnia symptoms. METHODS 33 insufficiently active adults (84.8% female; 78.8% White; age=34.9±10.6 y; body mass index=28.9 kg/m2) with at least mild insomnia symptoms (Insomnia Severity Index ≥ 10) were randomized to either a single 60-min session of VY (n=17) or a quiet rest control condition (CON: n=16) occurring between 15:00 and 20:00 h. VY followed a pre-recorded practice and CON watched a nature documentary. On one night before and after the experimental session, participants wore a wrist accelerometer and a chest heart rate (HR) monitor overnight and completed a sleep diary. HRV was derived from the entire HR recording across the nocturnal period and standardized for sleep duration, with root mean square of successive differences (RMSSD) as the primary outcome. Analyses compared the changes from pre- to post-session between groups using linear mixed models and Cohen’s d effect sizes. RESULTS The change in actigraphy-assessed sleep efficiency (SE) and total sleep time (TST) did not differ from pre- to post-session for VY (SE: 88.9±1.4 to 88.9±1.5%; TST: 454.7±15.8 to 445.8±17.4 min) or CON (SE: 89.4±1.4 to 88.7±1.6%; TST: 401.3±16.3 vs. 407.3±17.3 min); group x time interactions were not statistically significant (each p > 0.48). The change in nocturnal RMSSD did not differ from pre- to post-session for either VY (39.5±6.8 to 38.7±6.0 ms) or CON (37.6±7.0 to 35.8±6.2 ms) and the group x time interaction was not statistically significant (p=0.94). CONCLUSION An acute bout of VY performed in the early evening did not significantly change accelerometer- or diary-assessed sleep or impact parasympathetic tone during sleep. VY in the early evening is unlikely to benefit or impair sleep in adults with insomnia symptoms.

Impact of Sleep Apnea on Nocturnal Parasympathetic Activity in Atrial Fibrillation Patients After Catheter Ablation - Implications for Heart Rate Variability Analysis.

The impact of sleep apnea (SA) on heart rate variability (HRV) in atrial fibrillation (AF) patients has not been investigated.Methods and Results: Of 94 patients who underwent AF ablation between January 2021 and September 2022, 76 patients who had a nocturnal Holter electrocardiography and polysomnography conducted simultaneously were included in the analysis. A 15-min duration of HRV, as determined by an electrocardiogram during apnea and non-apnea time, were compared between patients with and without AF recurrence at 12 months' postoperatively. Patients had a mean age of 63.4±11.6 years, 14 were female, and 20 had AF recurrence at 12 months' follow-up. The root mean square of the difference between consecutive normal-to-normal intervals (RMSSD, ms) an indicator of a parasympathetic nervous system, was more highly increased in patients with AF recurrence than those without, during both apnea and non-apnea time (apnea time: 16.7±4.5 vs. 13.5±3.3, P=0.03; non-apnea time: 20.9±9.5 vs. 15.5±5.9, P<0.01). However, RMSSD during an apneic state was decreased more than that in a non-apneic state in both groups of patients with and without AF recurrence (AF recurrence group: 16.7±4.5 vs. 20.9±9.5, P<0.01; non-AF recurrence group; 13.5±3.3 vs. 15.5±5.9, P=0.03). Consequently, the effect of AF recurrence on parasympathetic activity was offset by SA. Similar trends were observed for other parasympathetic activity indices; high frequency (HF), logarithm of HF (lnHF) and the percentage of normal-to-normal intervals >50 ms (pNN50). Without considering the influence of SA, the results of nocturnal HRV analysis might be misinterpreted. Caution should be taken when using nocturnal HRV as a predictor of AF recurrence.

Heart Rate Variability during Slow Wave Sleep is Linked to Resting‐state Functional Connectivity in the Central Autonomic Network among Older Adults ‘at‐risk’ of Dementia

AbstractBackgroundReduced heart rate variability (HRV) can be an early sign of autonomic dysfunction in neurodegenerative diseases, and may be related to brain dysfunction in the central autonomic network (CAN). As yet, such autonomic dysfunction has not been examined during sleep – which is an ideal physiological state to study brain‐heart interaction as both the central and peripheral nervous systems behave differently compared to during wakefulness. Therefore, we aimed to examine whether nocturnal HRV, especially slow wave sleep (SWS), is associated with CAN functional connectivity in older adults ‘at‐risk’ of dementia.MethodOlder adults (n = 78; age range = 50‐88 years; 64% female) attending a memory clinic for cognitive concerns underwent resting‐state functional magnetic resonance imaging and an overnight polysomnography. From these, CAN functional connectivity strength and HRV data during sleep were derived, respectively. High‐frequency heart rate variability (HF‐HRV) was extracted to index parasympathetic activity during distinct periods of sleep, including SWS as well as secondary outcomes of non‐rapid eye movement sleep, wake after sleep onset, and rapid eye movement sleep. General linear models were used to examine associations between CAN functional connectivity and HF‐HRV.ResultAnalyses revealed that increased HF‐HRV during SWS was associated with stronger functional connectivity (F = 3.98, p = 0.022) in two core brain regions within the CAN, the right anterior insular and posterior midcingulate cortex, as well as stronger functional connectivity (F = 6.21, p = 0.005) between broader CAN brain regions – the right amygdala with three sub‐nuclei of the thalamus. There were no significant associations between HF‐HRV and CAN functional connectivity during wake after sleep onset or rapid eye movement sleep.ConclusionThese findings show that in older adults ‘at‐risk’ of dementia, parasympathetic regulation during SWS is uniquely linked to differential functional connectivity within both core and broader CAN brain regions. It is possible that dysfunctional brain‐heart interactions manifest primarily during this specific period of sleep known for its role in memory and metabolic clearance. Further studies elucidating the pathophysiology and directionality of this relationship should be conducted to determine if HRV drives neurodegeneration, or if brain degeneration within the CAN promotes aberrant HRV.

Blood pressure variability, nocturnal heart rate variability and endothelial function predict recurrent cerebro-cardiovascular events following ischemic stroke.

Cardiovascular parameters characterizing blood pressure (BP), heart rate (HR), endothelial function and arterial stiffness predict cerebro-cardiovascular events (CCVE) in the general population. Considering the paucity of data in stroke patients, we assessed these parameters as potential predictors of recurrent CCVE at acute stroke stroke. This is a secondary outcome analysis of a prospective observational longitudinal Sleep Deficiency & Stroke Outcome Study (ClinicalTrials.gov Identifier: NCT02559739). The study consecutively recruited acute ischemic stroke patients. Cardiovascular parameters (blood pressure variability [BPV], heart rate variability [HRV], endothelial function, and arterial stiffness) were assessed within the first week post-stroke. Future CCVE were recorded over a 3-year follow-up. Multivariate Cox regression analysis was used to investigate the prognostic value of 48 cardiovascular parameters regarding CCVE risk. Out of 447 recruited patients, 359 were included in this analysis. 20% of patients developed a future CCVE. A high variability of systolic BP (n = 333) and nocturnal HR (non-linear parameters; n = 187) at acute stroke predicted CCVE risk after adjustment for demographic parameters, cardiovascular risk factors and mean BP or HR, respectively. Endothelial dysfunction (n = 105) at acute stroke predicted CCVE risk after adjustment for age and sex, but not after adjustment for cardiovascular risk factors. Diurnal HR and arterial stiffness at acute stroke were not associated with CCVE risk. High blood pressure variability, high nocturnal HRV and endothelial function contribute to the risk for future CCVE after stroke.

The effect of chronic exercise training and acute exercise on power spectral analysis of heart rate variability.

Moderate to vigorous physical activity performed regularly is cardioprotective and reduces all-cause mortality, concomitant with increased resting heart rate variability (HRV). However, there are contradictory reports regarding the effects of chronic and acute exercise on nocturnal HRV in those performing exercise well-beyond physical activity guidelines. Therefore, the purpose of this study was to compare the power spectral analysis components of HRV in middle-aged endurance athletes (EA) and recreationally active individuals (REC) and explore acute exercise effects in EA. A total of 119 EA (52, 49-57 years) and 32 REC (56, 52-60 years) were recruited to complete 24h Holter monitoring (GE SEER 1000) in the absence of exercise. Fifty one EA (52, 49-57 years) then underwent 24h Holter monitoring following an intense bout of endurance exercise. Power spectral HRV analysis was completed hourly and averaged to quantify morning (1000-1200h), evening (1900-2100h), and nocturnal (0200-0400h) HRV. EA had greater very low frequency (VLF) and low frequency (LF) (both p< 0.001) compared to REC. LF/high frequency (HF) was greater in EA at 0200-0400h (p=0.04). Among all participants, the change in HR and HF from 1000-1200 to 0200-0400h was negatively correlated (r=-0.47, p< 0.001). Following acute exercise in EA, only nocturnal HRV was assessed. VLF (p< 0.001) and HF (p=0.008) decreased, while LF/HF increased (p=0.02). These results suggest that in EA, both long-term and acute exercises increase nocturnal sympathovagal activity through an increase in LF and decrease in HF, respectively. Further work is required to understand the mechanism underlying reduced nocturnal HRV in middle-aged EA and the long-term health implications.

Brief Report: Changes in Nocturnal Heart Rate Variability in People Living With HIV During the First Year of Antiretroviral Therapy Compared With HIV-Uninfected Community Controls.

Higher nocturnal heart rate and lower nocturnal heart rate variability (HRV) is associated with increased cardiovascular disease mortality. Longitudinal studies on nocturnal HRV in people living with HIV (PLWH) are lacking. We conducted a 1-year prospective cohort study of adult PLWH and HIV-uninfected community controls in northwestern Tanzania. At enrollment, we collected data on cardiovascular risk factors and tested blood samples for hemoglobin, insulin, CD4 cell count, and C-reactive protein. We measured nocturnal HRV and heart rate at baseline and first-year follow-up. Mixed effect linear regression was used to determine predictors of lower HRV. Of the 111 enrolled participants (74 PLWH and 37 HIV-uninfected adults), 57.7% were female and the median age was 40 years. Over 1 year of follow-up, the average nocturnal heart rate was 4.5 beats/minute higher in PLWH ( P = 0.006). In the fully adjusted model (with age, sex, nocturnal heart rate, and diabetes), average nocturnal HRV was 10.5 milliseconds lower in PLWH compared with HIV-uninfected adults ( P = 0.03). Unlike with nocturnal heart rate, nocturnal HRV did not improve after 1 year of ART in PLWH or HIV-uninfected adults (fully adjusted change = -2.5 milliseconds, P = 0.45). Lower educational attainment, lesser pancreatic β-cell function, and anemia were associated with higher HRV. Nocturnal parasympathetic nervous system function was persistently lower in PLWH compared with HIV-uninfected adults even after antiretroviral therapy initiation. Improving nocturnal autonomic nervous system function could be a target for cardiovascular disease prevention in PLWH.

Age Differences in Upper Gastrointestinal Symptoms and Vagal Modulation in Women With Irritable Bowel Syndrome.

Patients with irritable bowel syndrome (IBS) often report upper gastrointestinal (GI) (e.g., nausea and heartburn), somatic, and emotional symptoms. This study seeks to examine the relationships among younger and older women with IBS and indicators of autonomic nervous system (ANS) function and daily nausea and heartburn symptoms. Women were recruited through clinics and the community. Nocturnal heart rate variability (HRV) was obtained using ambulatory electrocardiogram Holter monitors. Individual symptom severity and frequency were collected using 28-day diaries. All variables were stratified by younger (<46years) and older (≥46years) age groups. Eighty-nine women with IBS were included in this descriptive correlation study (n = 57 younger; n = 32 older). Older women had reduced indices of vagal activity when compared to younger women. In older women, there was an inverse correlation between nausea and vagal measures (Ln RMSSD, r = -.41, p = .026; Ln pNN50, r = -.39, p = .034). Heartburn in older women was associated with sleepiness (r = .59, p < .001) and anger (r = .48, p = .006). Nausea was significantly correlated with anger in the younger group (r = .41, p = .001). There were no significant relationships between HRV indicators and nausea and heartburn in younger women. Age-related differences in ANS function that are associated with nausea may portend unique opportunities to better understand the vagal dysregulation in women with IBS.

Neuromuscular and autonomic function is fully recovered within 24 h following a sprint interval training session.

Recovery is a key factor to promote adaptations and enhance performance. Sprint Interval Training (SIT) is known to be an effective approach to improve overall physical function and health. Although a 2-day rest period is given between SIT sessions, the time-course of recovery after SIT is unknown. The aim of this study was to determine whether the neuromuscular and autonomic nervous systems would be impaired 24 and 48h after an SIT session. Twenty-five healthy subjects performed an 8 × 15s all-out session on a braked cycle ergometer with 2 min of rest between repetitions. Isometric maximal voluntary contraction (iMVC) and evoked forces to electrical nerve stimulation during iMVC and at rest were used to assess muscle contractile properties and voluntary activation before (Pre), 1 (Post24h), and 2 (Post48h) days after the session. Two maximal 7s sprints with two different loads were performed at those same time-points to evaluate the maximal theoretical force (F0), velocity (V0) and maximal power (Pmax) production during a dynamic exercise. Additionally, nocturnal heart rate variability (HRV) was assessed the previous and the three subsequent nights to the exercise bout. No significant impairments were observed for the iMVC or for the force evoked by electrical stimulation 1 day after the session. Similarly, F0, V0, and Pmax were unchanged at Post24h and Post48h. Furthermore, HRV did not reveal any temporal or frequential significant difference the nights following SIT compared to Pre. The results of this study show a full recovery of neuromuscular and autonomic functions a day after an all-out SIT session.

Core body temperature changes before sleep are associated with nocturnal heart rate variability.

Core body temperature (CBT) reductions occur before and during the sleep period, with the extent of presleep reductions corresponding to sleep onset and quality. Presleep reductions in CBT coincide with increased cardiac parasympathetic activity measured via heart rate variability (HRV), and while this appears to persist into the sleep period, individual differences in presleep CBT decline and nocturnal HRV remain unexplored. The purpose of the current study was to assess the relationship between individual differences in presleep CBT reductions and nocturnal heart rate (HR) and HRV in a population of 15 objectively poor sleeping adults [10 males, 5 females; age, 33 ± 4 yr; body mass index (BMI) 27 ± 1 kg/m2] with the hypothesis that blunted CBT rate of decline would be associated with elevated HR and reduced nocturnal HRV. Following an adaptation night, all participants underwent an overnight, in-laboratory sleep study with simultaneous recording of polysomnographic sleep including electrocardiography (ECG) and CBT recording. Correlations between CBT rate of change before sleep and nocturnal HRV were assessed. Blunted rate of CBT decline was significantly associated with increased heart rate (HR) in stage 2 (N2; R = 0.754, P = 0.001), stage 3 (N3; R = 0.748, P = 0.001), and rapid-eye movement (REM; R = 0.735, P = 0.002). Similarly, blunted rate of CBT decline before sleep was associated with reduced HRV across sleep stages. These findings indicate a relationship between individual differences in presleep thermoregulatory processes and nocturnal cardiac autonomic function in poor sleeping adults.NEW & NOTEWORTHY Core body temperature (CBT) reductions before sleep onset coincide with increases in heart rate variability (HRV) that persist throughout the sleep period. However, the relationship between individual differences in the efficiency of presleep core temperature regulation and nocturnal heart rate variability remains equivocal. The present study reports an association between the magnitude of presleep core body temperature changes and nocturnal parasympathetic activity, highlighting overlap between thermoregulatory processes before sleep and nocturnal cardiac autonomic function.

Cardiovascular remodeling in active and controlled acromegaly: association with sleep-disordered breathing.

We hypothesized that anunfavorable cardiovascular profile in acromegaly is associated with sleep-disordered breathing (SDB), while acromegaly control improves both respiratory sleep characteristics and thecardiovascular profile. The patients underwent the assessment of breathing during sleep and cardiovascular profileassessment atthe start of the studyincluding arterial stiffness, blood pressure, echocardiography, nocturnal heart rate variability (HRV). The assessment was repeated in patients withacromegaly at 1 year after transsphenoidal adenectomy (TSA). A total of 47 patients with acromegaly and 55 control subjects were enrolled. At one year after TSA, 22 patients with acromegaly were reassessed.Multiple linear regression analysis with adjustment for age, sex and body mass index (BMI) showed the associations of insulin growth-like factor 1 (IGF-1) with obstructive apnea index (OAI: β=0.035/h, p<0.001), but not with cardiovascular parameters, in patients withacromegaly. The analysis of combined acromegaly and control dataset with adjustment for age, sex and BMI showed the association the presence of acromegaly with diastolic blood pressure (DBP; β=17.99 mmHg, p<0.001), ejection fraction (EF; β=6.23%, p=0.009), left heart remodeling (left ventricle posterior wall: β=0.81 mm, p=0.045) and the association of the presence of SDB (apnea-hypopnea index≥15/h) with left ventricular function (EF: -4.12%, p=0.040; end systolic volume: 10.12 ml, p=0.004). Control of acromegaly was accompanied by the decrease in OAI (5.9 [0.8, 14.5]/h and 1.7 [0.2, 5.1]/h, p=0.004) and nocturnal heart rate (66.1 [59.2, 69.8] bpm and 61.7 [54.0, 67.2] bpm, p=0.025) and by the increase in blood pressure (DBP: 78.0 [70.3, 86.0] mm Hg and 80.0 [80.0, 90.0] mm Hg, p=0.012). The comorbidities of acromegaly, including sleep-disordered breathing, appear to have a long-term effect on cardiovascular remodeling in active acromegaly. Future studies should investigate the applicability of the treatment of SDBfor the reduction of cardiovascular risk in acromegaly.

Core temperature decline prior to sleep onset is associated with nocturnal heart rate variability

Impaired thermoregulation is associated with poor sleep and autonomic dysfunction. Previous studies demonstrate an association between core body temperature (CBT) dipping and an increase in heart rate variability (HRV) prior to sleep onset. However, the relationship between the rate of CBT decline prior to sleep onset and nocturnal HRV has not been established. The purpose of this study was to investigate the relationship between the rate of CBT decline prior to sleep onset and nocturnal HRV in objectively poor sleepers. We hypothesized a blunted pre-sleep CBT decline would correspond to reduced nocturnal HRV. Fifteen participants (9 males, 6 females; age, 33±4 years; BMI 27±1 kg/m 2 ) underwent an 8-hour overnight sleep opportunity with continuous polysomnography (PSG) and 2-lead electrocardiogram monitoring. A temperature monitoring pill (CoreTempTM, HQ Inc., Palmetto, FL) was ingested with a standardized dinner to record CBT every 10 seconds throughout the sleep period. Core temperature was sampled every 5 minutes from the core temperature tracing one hour prior to sleep onset until final awakening. The rate of CBT decline prior to sleep onset was measured as the slope of CBT values from 1 hour prior to lights out until PSG sleep onset. Nocturnal HRV measures including the root mean squared of successive differences (RMSSD), percentage of R-R intervals (RRI) varying by greater than 50 ms (pNN50), and the high frequency (HF) power of the RRI were determined across the night in stage 2 (N2), stage 3 (SWS), and rapid eye movement (REM) sleep stages. Bivariate correlations were performed to assess the association between CBT rate of decline and nocturnal HRV measures. An inverse correlation was observed between the rate of CBT prior to sleep onset and the RRI in N2 (R= -0.743, p=0.002), SWS (R = -0.730, P = 0.002), and REM (R = -0.708, P = 0.003). Additionally, the rate of pre-sleep CBT decline was inversely correlated with time domain HRV measures in N2 (pNN50: R= -0.598, p= 0.019; RMSSD: R = -0.557, P = 0.031) and SWS (pNN50: R = -0.542, P = 0.037; RMSSD: R = -0.591, P = 0.020). A blunted rate of CBT was further correlated to decreased HF log10 in N2 (R= -0.592, p= 0.020) and REM (R= -0.602, p= 0.018). Our results indicate an association between blunted core temperature decline prior to sleep onset and reduced nocturnal HRV. These findings suggest that adequate thermoregulation prior to sleep onset may have lasting associations with nocturnal cardiac autonomic function. Support is provided by the National Institutes of Health (AA-024892, U54GM115371; P20GM103474). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Beta intrusion during N2 sleep is negatively associated with nocturnal heart rate variability in healthy adults

Increased cognitive hyperarousal is a proposed mechanism associated with clinical poor sleep including insomnia. An objective marker of nocturnal hyperarousal is high frequency electroencephalography during sleep, including increased beta frequency during stage two (N2) sleep. Acute and chronic poor sleep quality are associated with autonomic dysfunction, but little is known regarding the relationship between nocturnal beta frequency intrusion and nocturnal autonomic function. The purpose of this study was to explore the association between beta spectral power during stage two (N2) sleep and nocturnal heart rate variability (HRV) in healthy female and male adults. We hypothesized that heightened beta spectral power during N2 sleep would be associated with reduced nocturnal HRV. Twenty-four participants (12 males, 12 females; age, 25 ± 1 years; BMI 27 ± 1 kg/m2) underwent an 8-hour overnight sleep opportunity with continuous polysomnography and 5-lead electrocardiogram monitoring. Periods of 5 – 10 minutes of stable N2 sleep absent of cortical arousals, respiratory events, and limb movement-associated arousals were identified (one per cycle) for analysis. Periods from the first two cycles of N2 sleep from the full night were selected for analysis. Beta spectral power from the central and frontal regions and nocturnal HRV data were analyzed and averaged across each hemisphere. Time-domain HRV was quantified as the root mean squared of successive differences (RMSSD) and proportion of R-R intervals (RRI) varying by greater than 50 ms (pNN50). An inverse correlation was observed between central beta power and RRI (R= -0.473, p=0.019), pNN50 (R= -0.450, p=0.028), and RMSSD (R= -0.406, p=0.049). This was paralleled by a similar relationship between frontal beta and RRI (R= -0.487, p=0.016) and pNN50 (R= -0.423, p=0.039). Our results indicate a negative association between N2 beta power and nocturnal HRV measures. These findings suggest that nocturnal hyperarousal may be associated with poor cardiac autonomic function and has implications for individuals with insomnia in whom cognitive hyperarousal is frequently reported. Support is provided by the National Institutes of Health (AA-024892, U54GM115371; P20GM103474, 2TL1 TR002318). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Home-Based Measurements of Nocturnal Cardiac Parasympathetic Activity in Athletes during Return to Sport after Sport-Related Concussion.

Sport-related concussions (SRC) are characterized by impaired autonomic control. Heart rate variability (HRV) offers easily obtainable diagnostic approaches to SRC-associated dysautonomia, but studies investigating HRV during sleep, a crucial time for post-traumatic cerebral regeneration, are relatively sparse. The aim of this study was to assess nocturnal HRV in athletes during their return to sports (RTS) after SRC in their home environment using wireless wrist sensors (E4, Empatica, Milan, Italy) and to explore possible relations with clinical concussion-associated sleep symptoms. Eighteen SRC athletes wore a wrist sensor obtaining photoplethysmographic data at night during RTS as well as one night after full clinical recovery post RTS (>3 weeks). Nocturnal heart rate and parasympathetic activity of HRV (RMSSD) were calculated and compared using the Mann-Whitney U Test to values of eighteen; matched by sex, age, sport, and expertise, control athletes underwent the identical protocol. During RTS, nocturnal RMSSD of SRC athletes (Mdn = 77.74 ms) showed a trend compared to controls (Mdn = 95.68 ms, p = 0.021, r = -0.382, p adjusted using false discovery rate = 0.126) and positively correlated to "drowsiness" (r = 0.523, p = 0.023, p adjusted = 0.046). Post RTS, no differences in RMSSD between groups were detected. The presented findings in nocturnal cardiac parasympathetic activity during nights of RTS in SRC athletes might be a result of concussion, although its relation to recovery still needs to be elucidated. Utilization of wireless sensors and wearable technologies in home-based settings offer a possibility to obtain helpful objective data in the management of SRC.

Nocturnal Heart Rate Variability Might Help in Predicting Severe Obstructive Sleep-Disordered Breathing.

Obstructive sleep apnea (OSA) can have long-term cardiovascular and metabolic effects. The identification of OSA-related impairments would provide diagnostic and prognostic value. Heart rate variability (HRV) as a measure of cardiac autonomic regulation is a promising candidate marker of OSA and OSA-related conditions. We took advantage of the Physionet Apnea-ECG database for two purposes. First, we performed time- and frequency-domain analysis of nocturnal HRV on each recording of this database to evaluate the cardiac autonomic regulation in patients with nighttime sleep breathing disorders. Second, we conducted a logistic regression analysis (backward stepwise) to identify the HRV indices able to predict the apnea-hypopnea index (AHI) categories (i.e., "Severe OSA", AHI ≥ 30; "Moderate-Mild OSA", 5 ≥ AHI < 30; and "Normal", AHI < 5). Compared to the "Normal", the "Severe OSA" group showed lower high-frequency power in normalized units (HFnu) and higher low-frequency power in normalized units (LFnu). The standard deviation of normal R-R intervals (SDNN) and the root mean square of successive R-R interval differences (RMSSD) were independently associated with sleep-disordered breathing. Our findings suggest altered cardiac autonomic regulation with a reduced parasympathetic component in OSA patients and suggest a role of nighttime HRV in the characterization and identification of sleep breathing disorders.

Association of Heart Rate Variability with Obstructive Sleep Apnea in Adults.

Background and Objectives: Heart rate variability (HRV) analysis is a noninvasive method used to examine autonomic system function, and the clinical applications of HRV analysis have been well documented. The aim of this study is to investigate the association between HRV and the apnea-hypopnea index (AHI) in patients referred for polysomnography (PSG) for obstructive sleep apnea (OSA) diagnosis. Materials and Methods: Patients underwent whole-night PSG. Data on nocturnal HRV and AHI were analyzed. We determined the correlation of time- and frequency-domain parameters of HRV with the AHI. Results: A total of 62 participants (50 men and 12 women) were enrolled. The mean age, body mass index (BMI), neck circumference, and AHI score of the patients were 44.4 ± 11.5 years, 28.7 ± 5.2, 40.2 ± 4.8 cm, and 32.1 ± 27.0, respectively. The log root mean square of successive differences between normal heartbeats (RMSSD) were negatively correlated with BMI (p = 0.034) and neck circumference (p = 0.003). The log absolute power of the low-frequency band over high-frequency band (LF/HF) ratio was positively correlated with the AHI (p = 0.006). A higher log LF/HF power ratio (β = 5.01, p = 0.029) and BMI (β = 2.20, p < 0.001) were associated with a higher AHI value in multiple linear regression analysis. Conclusions: A higher log LF/HF power ratio and BMI were positively and significantly associated with the AHI during whole-night PSG in adult patients.

Nocturnal Heart Rate Variability in Women Discordant for Hormonal Contraceptive Use.

The aim of this study was to investigate within-cycle differences in nocturnal heart rate (HR) and heart rate variability (HRV) in naturally menstruating women (NM) and women using combined hormonal contraceptives (CU) or progestin-only hormonal contraceptives (PU). Physically active participants were recruited into three groups: NM ( n = 19), CU ( n = 11), and PU ( n = 12). Participants' HR and HRV (with Bodyguard 2 HRV monitor) and blood hormones were monitored during one menstrual cycle (MC) (NM group) or for 4 wk (CU and PU groups). Estradiol, progesterone, and luteinizing hormone were analyzed from fasting blood samples collected four times in the NM (M1 = bleeding, M2 = follicular phase, M3 = ovulation, and M4 = luteal phase) and PU groups (M1 = lowest E 2 , M2 = M1 + 7 d, M3 = M1 + 14 d, and M4 = M1 + 21 d) and twice in the CU group (active and inactive pill phases). After every blood sample, nightly HR and HRV were recorded and examined as an average from two nights. Hormonal concentrations differed ( P < 0.05) between MC phases in the NM and PU groups, but not ( P ≥ 0.116) between the active and the inactive phases in the CU group. In the NM and PU groups, some of the HRV values were higher, whereas in the NM group, HR was lower during M2 compared with M3 ( P < 0.049) and M4 ( P < 0.035). In the CU group, HRV values ( P = 0.014-0.038) were higher, and HR was lower ( P = 0.038) in the inactive phase compared with the first week of the active phase. The MC and the hormonal cycle phases influence autonomic nervous system balance, which is reflected in measurements of nocturnal HR and HRV. This should be considered when monitoring recovery in physically active individuals.

Overnight heart rate variability responses to military combat engineer training

The study aimed to determine if overnight heart rate variability (HRV) is reflective of workload and stress during military training. Measures of cognitive load, perceived exertion, physical activity, nocturnal HRV, cognitive performance and sleep were recorded for a 15-day assessment period in 32 combat engineers. The assessment period consisted of 4 phases, PRE, FIELD, BASE and RECOVERY that exposed trainees to periods of sleep deprivation and restriction. The FIELD phase was characterised by an increase in mood disturbance, perceived exertion, physical activity, HRV and a reduction in sleep quantity (p < 0.05). Measures of HRV returned to PRE-values quicker than subjective wellbeing responses. The combination of sleep duration (β = −0.002, F = 13.42, p < 0.001) and physical activity (metabolic equivalents, β = −0.483, F = 5.95, p = 0.017), the main stressors of the exercise, provided a significant effect in the best predictive model of HRV. The different recovery rates of HRV and subjective wellbeing suggest a different physiological and psychological response.

Monitoring Heart Rate Variability and Its Association with High-Intensity Running, Psychometric Status, and Training Load in Elite Female Soccer Players during Match Weeks

In order to maximize adaptations to reach high performance, sports coaches must regularly monitor the healing process following competitions or important training sessions and maintain psychometric status. As a result, the objective of this study was to track heart rate variability (HRV) in elite Spanish female soccer players during match weeks and examine its connection to high-intensity running, psychometric status, and training load. Changes in the nocturnal HRV measured along the square root of differences between adjacent RR intervals of 4 h (rMSSD 4 h) during the first phase of slow wave sleep (rMSSD 5 min), resting heart rate (RHR 4 h and RHR 5 min) were recorded with Firstbeat Bodyguard 2 (Firstbeat Technologies, Jyvaskyla, Finland). Training and match loads were recorded with rating perceived exertion and high-intensity running data by using a global positioning system (GPS) device (SPI-Pro X, GPSports). Ultimately, the psychometric test was recorded by a 5-item questionnaire, and all data were analyzed across three weeks of a competitive season. The day of the match found the lowest HRV, while the day following the match found a substantial (p &lt; 0.01) rise in rMSSD 4 h and rMSSD 5 min. Similarly, these variables showed significant differences two days after the match. Similarly, these variables showed significant differences two days after the match. Furthermore, significant differences were found between the RHR 4 h and RHR 5 min (p &lt; 0.01) and rMSSD 4 h and rMSSD 5 min (p &lt; 0.05) and variables after two days with a higher training load. The results gathered from the psychometric tests, and the various HR markers showed significant associations. As a result, HRV, RHR, and psychometric assessments are probably sensitive to changes in load within a microcycle, providing a straightforward and non-invasive technique to assess changes in the recovery/fatigue status of top-level female soccer players.

Nocturnal heart rate variability indices as markers of obstructive sleep- disordered breathing

Nocturnal heart rate variability indices as markers of obstructive sleep- disordered breathing