Sympathetic-nerve activity during sleep in normal subjects

Development of optic disc edema during 30 days of hypercapnic head-down tilt bed rest is associated with short sleep duration and blunted temperature amplitude

Sleep and circadian temperature disturbances occur with spaceflight and may, in part, result from the chronically elevated carbon dioxide (CO2) levels on the international space station. Impaired sleep may contribute to decreased glymphatic clearance and, when combined with the chronic headward fluid shift during actual spaceflight or the spaceflight analog head-down tilt bed rest (HDTBR), may contribute to the development of optic disc edema. We determined if strict HDTBR combined with mildly elevated CO2 levels influenced sleep and core temperature and was associated with the development of optic disc edema. Healthy participants (5 females) aged 25-50 yr, underwent 30 days of strict 6° HDTBR with ambient Pco2 = 4 mmHg. Measures of sleep, 24-h core temperature, overnight transcutaneous CO2, and Frisén grade edema were made pre-HDTBR, on HDTBR days 4, 17, 28, and post-HDTBR days 4 and 10. During all HDTBR time points, sleep, core temperature, and overnight transcutaneous CO2 were not different than the pre-HDTBR measurements. However, independent of the HDTBR intervention, the odds ratios {mean [95% confidence interval (CI)]} for developing Frisén grade optic disc edema were statistically significant for each hour below the mean total sleep time (2.2 [1.1-4.4]) and stage 2 nonrapid eye movement (NREM) sleep (4.8 [1.3-18.6]), and above the mean for wake after sleep onset (3.6 [1.2-10.6]) and for each 0.1°C decrease in core temperature amplitude below the mean (4.0 [1.4-11.7]). These data suggest that optic disc edema occurring during HDTBR was more likely to occur in those with short sleep duration and/or blunted temperature amplitude.NEW & NOTEWORTHY We determined that sleep and 24-h core body temperature were unaltered by 30 days exposure to the spaceflight analog strict 6° head-down tilt bed rest (HDTBR) in a 0.5% CO2 environment. However, shorter sleep duration, greater wake after sleep onset, and lower core temperature amplitude present throughout the study were associated with the development of optic disc edema, a key finding of spaceflight-associated neuro-ocular syndrome.

Objective sleep characteristics and hypertension: a community-based cohort study

Objective

The link between sleep quality and hypertension risk is well-established. However, research on the specific dose-relationship between objective sleep characteristics and hypertension incidence remains limited. This study aims to explore the dose-relationship association between objective sleep characteristics and hypertension incidence.

Methods

A community-based prospective cohort study design was employed using data from the Sleep Heart Health Study (SHHS). A total of 2,460 individuals were included in the study, of which 780 had hypertension. Baseline personal characteristics and medical history were collected. Objective sleep characteristics were obtained through polysomnography (PSG). Multivariate logistic regression models were utilized for analysis. Restricted cubic splines (RCS) were used to examine dose-relationship associations.

Results

After adjusting for covariates, the percentage of total sleep duration in stage 2 (N2%) was positively associated with hypertension incidence, while the N3% was negatively associated with hypertension incidence Odds ratio (OR) = 1.009, 95% confidence interval (CI) [1.001, 1.018], P = 0.037; OR = 0.987, 95% CI: [0.979, 0.995], P = 0.028, respectively. For every 10% increase in N2 sleep, the risk of developing hypertension increases by 9%, while a 3% decrease in N3 sleep corresponds to a 0.1% increase in the incidence of hypertension. In the subgroup of non-depression, a positive association between N2% and hypertension was significant statistically (OR = 1.012, 95%CI, 1.002, 1.021, P = 0.013, Pinteraction = 0.013). RCS demonstrated that the risk of developing hypertension was lower when N2% ranged from 38% to 58% and rapidly increased thereafter (P = 0.002, non-linear P = 0.040). The lowest risk for hypertension incidence risk of N3% occurring at 25%, and a significant increase below 15% or above 40% (P = 0.001, non-linear P = 0.008).

Conclusions

There's a negative association between N3% and the incidence of hypertension, and a positive association between N2% and the incidence of hypertension, particularly among non-depression individuals. These associations exhibit strong non-linear dose-response relationships.

Nighttime administration of antihypertensive medication: a review of chronotherapy in hypertension

Hypertension remains a global health concern because of suboptimal blood pressure control despite advancements in antihypertensive treatments. Chronotherapy, defined as evening or bedtime administration of medication based on biological rhythms, is emerging as a potential strategy to improve blood pressure control and treatment outcomes. Clinical trials have investigated the potential effects of nighttime administration of antihypertensive medication in the improvement of 24 hours blood pressure control and reduction of cardiovascular risk. Implementing chronotherapy in clinical practice could have significant implications in enhancing blood pressure control and improving clinical outcomes in patients with hypertension, particularly those with resistant hypertension. However, recent trials have reported contradictory results, causing confusion in real-world practice. Herein we review, analyze, and critique the current evidence and propose suggestions regarding the clinical application and future directions of chronotherapy.

Measurement of peripheral arterial tone to detect sleep-disordered breathing in patients with heart failure

PURPOSE

Sleep-disordered breathing is highly prevalent in patients with heart failure and is related to increased mortality and morbidity. The gold standard for sleep diagnostic is polysomnography in a sleep laboratory. Measurement of peripheral arterial tone with a wrist-worn diagnostic device is a promising method to detect sleep-disordered breathing without major technical effort.

METHODS

We prospectively enrolled patients with heart failure with reduced ejection fraction for measurement of the peripheral arterial tone and polysomnography simultaneously during one night in the sleep laboratory. Raw data of polysomnography was analyzed blindly by sleep core lab personnel and compared with automatic algorithm-based sleep results of measurement of the peripheral arterial tone.

RESULTS

A total of 25 patients provided comparable sleep results. All patients had sleep-disordered breathing and were identified by measurement of the peripheral arterial tone. The comparison of apnea-hypopnea index between peripheral arterial tone 38.8 ± 17.4/h and polysomnography 44.5 ± 17.9/h revealed a bias of - 5.7 ± 9.8/h with limits of agreement of ± 19.2/h in Bland-Altman analysis but showed high and significant Pearson correlation (r = 0.848, p < 0.001).

CONCLUSION

The findings suggest that measurement of the peripheral arterial tone may be useful to identify sleep-disordered breathing in patients with heart failure with reduced ejection fraction.

Cardiac autonomic profile, perceived stress and environmental comfort in healthy employees during remote and in-office work

Remote work (REMOTE) causes an overlap between working and domestic demands. The study of the cardiac autonomic profile (CAP) by means of heart rate variability (HRV) provides information about the impact of REMOTE on workers' health. The primary aim was to determine whether CAP, self-perceived stress, environmental and workstation comfort are modified during REMOTE. The secondary aim was to explore how these indices are influenced by individual and environmental work-related factors. Fifty healthy office employees alternating REMOTE and in-office (OFFICE) working were enrolled, rated self-perceived stress, environmental and workstation comfort using a visual analogue scale and performed a 24-h electrocardiogram during REMOTE and OFFICE. Stress was lower (5.6 ± 2.2 vs. 6.4 ± 1.8), environmental comfort higher (7.7 ± 1.9 vs. 7.0 ± 1.5), and the workstation comfort poorer (6.2 ± 1.8 vs. 7.5 ± 1.2) during REMOTE. CAP was similar during REMOTE and OFFICE. CAP was influenced by some work-related factors, including the presence of offspring, absence of a dedicated workspace during REMOTE and number of working hours. All these variables determined a decreased vagal modulation. The working setting seems to impact the levels of perceived stress and comfort, but not the CAP. However, individual and environmental work-related factors reduce cardiac vagal modulation during REMOTE, potentially increasing the risk of developing cardiovascular diseases.

Cerebrovascular pathology mediates associations between hypoxemia during rapid eye movement sleep and medial temporal lobe structure and function in older adults

Obstructive sleep apnea (OSA) is common in older adults and is associated with medial temporal lobe (MTL) degeneration and memory decline in aging and Alzheimer's disease (AD). However, the underlying mechanisms linking OSA to MTL degeneration and impaired memory remains unclear. By combining magnetic resonance imaging (MRI) assessments of cerebrovascular pathology and MTL structure with clinical polysomnography and assessment of overnight emotional memory retention in older adults at risk for AD, cerebrovascular pathology in fronto-parietal brain regions was shown to statistically mediate the relationship between OSA-related hypoxemia, particularly during rapid eye movement (REM) sleep, and entorhinal cortical thickness. Reduced entorhinal cortical thickness was, in turn, associated with impaired overnight retention in mnemonic discrimination ability across emotional valences for high similarity lures. These findings identify cerebrovascular pathology as a contributing mechanism linking hypoxemia to MTL degeneration and impaired sleep-dependent memory in older adults.

Revisiting the Role of Serotonin in Sleep-Disordered Breathing

Serotonin or 5-hydroxytryptamine (5-HT) is a ubiquitous neuro-modulator-transmitter that acts in the central nervous system, playing a major role in the control of breathing and other physiological functions. The midbrain, pons, and medulla regions contain several serotonergic nuclei with distinct physiological roles, including regulating the hypercapnic ventilatory response, upper airway patency, and sleep-wake states. Obesity is a major risk factor in the development of sleep-disordered breathing (SDB), such as obstructive sleep apnea (OSA), recurrent closure of the upper airway during sleep, and obesity hypoventilation syndrome (OHS), a condition characterized by daytime hypercapnia and hypoventilation during sleep. Approximately 936 million adults have OSA, and 32 million have OHS worldwide. 5-HT acts on 5-HT receptor subtypes that modulate neural control of breathing and upper airway patency. This article reviews the role of 5-HT in SDB and the current advances in 5-HT-targeted treatments for SDB.

Shorter total sleep time is associated with lower CD4+/CD8+ T cell ratios in virally suppressed men with HIV

Study Objectives

Although poor sleep quality is associated with lower CD4+ T cell counts among people living with HIV (PLWH), the association between objective sleep metrics and T lymphocyte subset counts is unknown. We evaluated the association between polysomnography (PSG) derived sleep metrics and T lymphocyte subpopulations in a cohort of men living with HIV.

Methods

Virally suppressed men living with HIV participating in the Multicenter AIDS Cohort Study underwent home overnight PSG. We assessed the association of PSG parameters with CD4+ and CD8+ T cell counts and the CD4+/CD8+ T cell ratio.

Results

Overall, 289 men with mean (±SD) age 55.3 ± 11.3 years and mean CD4+ T cell count 730 ± 308 cells/mm3 were evaluated. Total sleep time (TST) was significantly associated with CD8+ but not CD4+ T cell counts. After adjusting for age, race, depressive symptoms, antidepressant use, and non-nucleoside reverse transcriptase inhibitors use, every hour of shorter TST was associated with an additional 33 circulating CD8+ T cells/mm3 (p = 0.05) and a 5.6% (p = 0.0007) decline in CD4+/CD8+ T cell ratio. In adjusted models, every hour of shorter rapid eye movement (REM) sleep was associated with an additional 113 CD8+ T cells/mm3 (p = 0.02) and a 15.1% lower CD4+/CD8+ T cell ratio (p = 0.006). In contrast, measures of sleep efficiency and sleep-disordered breathing were not associated with differences in T lymphocyte subpopulations.

Conclusions

Our findings suggest that shorter TST and REM sleep durations are associated with differences in T lymphocyte subpopulations among men living with HIV. Addressing sleep may reflect a novel opportunity to improve immune function in PLWH.

Heart rate variability during sleep in synucleinopathies: a review

Synucleinopathies are a group of neurodegenerative diseases characterized by abnormal accumulations of insoluble alpha-synuclein in neurons or glial cells. These consist of Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). Moreover, idiopathic REM sleep behavior disorder (iRBD) is often the first manifestation of synucleinopathies, demonstrating a pathophysiological continuum. While these disorders vary in prevalence, symptom patterns, and severity, they can all include autonomic nervous system (ANS) dysfunction, which significantly reduces quality of life and worsens prognosis. Consequently, identifying abnormalities of the ANS can provide opportunities for improving quality of life through symptomatic treatments that are tailored to the individual's symptoms. An exciting development is using heart rate variability (HRV) as a non-invasive research tool for analyzing how the ANS regulates physiological processes. HRV during sleep, however, may provide a more accurate and reliable measure of ANS activity than during wakefulness, as during awake time, ANS activity is influenced by a variety of factors, including physical activity, stress, and emotions, which may mask or confound the underlying patterns of ANS activity. This review aims to provide an overview of the current knowledge regarding sleep-related HRV in synucleinopathies and to discuss contributing mechanisms. Evidence suggests that iRBD, PD, and MSA are associated with nocturnal ANS dysfunction. Further, comparative studies indicate that the presence of RBD could exacerbate this abnormality. In contrast, no studies have been conducted in patients with DLB. Overall, this review provides new insight into the complex interplay between the ANS and synucleinopathies and underscores the need for further research in this area to develop effective therapies to improve sleep and overall quality of life in patients with synucleinopathies.

Preceding Night Sleep Quality and Atrial Fibrillation Episodes in the I-STOP-AFIB Randomized Trial

BACKGROUND

Chronic sleep disruption is associated with incident atrial fibrillation (AF), but it is unclear whether poor sleep quality acutely triggers AF.

OBJECTIVES

The aim of this study was to characterize the relationship between a given night's sleep quality and the risk of a discrete AF episode.

METHODS

Patients with symptomatic paroxysmal AF in the I-STOP-AFIB (Individualized Studies of Triggers of Paroxysmal Atrial Fibrillation) trial reported sleep quality on a daily basis. Participants were also queried daily regarding AF episodes and were provided smartphone-based mobile electrocardiograms (ECGs) (KardiaMobile, AliveCor).

RESULTS

Using 15,755 days of data from 419 patients, worse sleep quality on any given night was associated with a 15% greater odds of a self-reported AF episode the next day (OR: 1.15; 95% CI: 1.10-1.20; P < 0.0001) after adjustment for the day of the week. No statistically significant associations between worsening sleep quality and mobile ECG-confirmed AF events were observed (OR: 1.04; 95% CI: 0.95-1.13; P = 0.43), although substantially fewer of these mobile ECG-confirmed events may have limited statistical power. Poor sleep was also associated with longer self-reported AF episodes, with each progressive category of worsening sleep associated with 16 (95% CI: 12-21; P < 0.001) more minutes of AF the next day.

CONCLUSIONS

Poor sleep was associated with an immediately heightened risk for self-reported AF episodes, and a dose-response relationship existed such that progressively worse sleep was associated with longer episodes of AF the next day. These data suggest that sleep quality may be a potentially modifiable trigger relevant to the near-term risk of a discrete AF episode.

Imaging biomarkers of sleep-related hypermotor epilepsy and sudden unexpected death in epilepsy: a review

In recent years, imaging has emerged as a promising source of several intriguing biomarkers in epilepsy, due to the impressive growth of imaging technology, supported by methodological advances and integrations of post-processing techniques. Bearing in mind the mutually influencing connection between sleep and epilepsy, we focused on sleep-related hypermotor epilepsy (SHE) and sudden unexpected death in epilepsy (SUDEP), aiming to make order and clarify possible clinical utility of emerging multimodal imaging biomarkers of these two epilepsy-related entities commonly occurring during sleep. Regarding SHE, advanced structural techniques might soon emerge as a promising source of diagnostic and predictive biomarkers, tailoring a targeted therapeutic (surgical) approach for MRI-negative subjects. Functional and metabolic imaging may instead unveil SHE's extensive and night-related altered brain networks, providing insights into distinctions and similarities with non-epileptic sleep phenomena, such as parasomnias. SUDEP is considered a storm that strikes without warning signals, but objective subtle structural and functional alterations in autonomic, cardiorespiratory, and arousal centers are present in patients eventually experiencing SUDEP. These alterations could be seen both as susceptibility and diagnostic biomarkers of the underlying pathological ongoing loop ultimately ending in death. Finally, given that SHE and SUDEP are rare phenomena, most evidence on the topic is derived from small single-center experiences with scarcely comparable results, hampering the possibility of performing any meta-analytic approach. Multicenter, longitudinal, well-designed studies are strongly encouraged.

[Effects of slow-wave sleep fragmentation and rapid eye movement sleep fragmentation on melatonin secretion]

OBJECTIVE

To compare the effect of stage 3 fragmentation and the paradoxical phase of night sleep on melatonin (MT) secretion, and to evaluate the effects of changes in autonomic balance and activation reactions that occur in the orthodox and paradoxical phases of sleep.

MATERIAL AND METHODS

Fifteen healthy men participated in three sessions: with stage 3 fragmentation, with fragmentation of paradoxical sleep, and in a control experiment in which sleep was not disturbed. In each experiment, 7 saliva samples were collected in the evening, at night and in the morning and the MT content was determined. Heart rate variability was analyzed using an electrocardiogram and autonomic balance was assessed.

RESULTS

Sleep fragmentation was accompanied by activation reactions and reduced the duration of stage 3 and paradoxical phase sleep by 50% and 51% in the corresponding sessions. Fragmentation of paradoxical sleep also led to an increase in the duration of night wakefulness. Sleep disturbances caused an increase in MT secretion in the second half of the night and in the morning, especially pronounced in sessions with fragmentation of paradoxical sleep, in which upon awakening MT was 1.8 times higher than in the control. Stage 3 fragmentation was accompanied by increased sympathetic activation, while fragmentation of paradoxical sleep did not cause autonomic shifts. The subjects were divided into 2 clusters: with high and low MT in night and morning saliva samples. In all sessions, subjects with high MT had 1.7-2 times longer duration of night wakefulness; in sessions with fragmentation, they had significantly more activations in the paradoxical phase of sleep.

CONCLUSION

Night sleep disturbances cause an increase in MT secretion, especially pronounced during the fragmentation of the paradoxical phase. An increase in MT levels does not depend on changes in autonomic balance and is apparently associated with activation of the serotonergic system, which accompanies disturbances in the depth and continuity of sleep.

Association of sleep duration with atrial fibrillation/flutter mortality in the United States: a cross-sectional analysis

BACKGROUND

The association between sleep duration and atrial fibrillation risk is poorly understood, with inconsistent findings reported by several studies. We sought to assess the association between long sleep duration and mortality due to atrial fibrillation/atrial flutter (AF/AFL).

METHODS

The 2016-2020 Centers for Disease Control and Prevention (CDC) Wide-Ranging Online Data for Epidemiologic Research dataset was used to identify death records secondary to AF/AFL in the United States population. We used the 2018 Behavioral Risk Factor Surveillance System (BRFSS) dataset of sleep duration at the county level. All counties were grouped into quartiles based on the percentage of their population with long sleep duration (i.e., ≥ 7 h), Q1 being the lowest and Q4 the highest quartile. Age-adjusted mortality rates (AAMR) were calculated for each quartile. County Health Rankings for Texas were used to adjust the AAMR for comorbidities using linear regression.

RESULTS

Overall, the AAMR for AF/AFL were highest in Q4 (65.9 [95% CI, 65.5-66.2] per 100,000 person-years) and lowest in Q1 (52.3 [95% CI, 52.1-52.5] per 100,000 person-years). The AAMR for AF/AFL increased stepwise from the lowest to highest quartiles of the percentage population with long sleep duration. After adjustment for the county health ranks of Texas, long sleep duration remained associated with a significantly higher AAMR (coefficient 220.6 (95% CI, 21.53-419.72, p-value = 0.03).

CONCLUSIONS

Long sleep duration was associated with higher AF/AFL mortality. Increased focus on risk reduction for AF, public awareness about the importance of optimal sleep duration, and further research to elucidate a potential causal relationship between sleep duration and AF are warranted.

Role of the autonomic nervous system in young, middle-aged, and older individuals with essential hypertension and sleep-related changes in neurocardiac regulation

Essential hypertension involves complex cardiovascular regulation. The autonomic nervous system function fluctuates throughout the sleep-wake cycle and changes with advancing age. However, the precise role of the autonomic nervous system in the development of hypertension during aging remains unclear. In this study, we characterized autonomic function during the sleep-wake cycle in different age groups with essential hypertension. This study included 97 men (53 with and 44 without hypertension) aged 30-79 years. They were stratified by age into young (< 40 years), middle-aged (40-59 years), and older (60-79 years) groups. Polysomnography and blood pressure data were recorded for 2 min before and during an hour-long nap. Autonomic function was assessed by measuring heart rate variability and blood pressure variability. Data were analyzed using t tests, correlation analyses, and two-way analysis of variance. During nonrapid eye movement (nREM), a main effect of age was observed on cardiac parasympathetic measures and baroreflex sensitivity (BRS), with the highest and lowest levels noted in the younger and older groups, respectively. The coefficients of the correlations between these measures and age were lower in patients with hypertension than in normotensive controls. The BRS of young patients with hypertension was similar to that of their middle-aged and older counterparts. However, cardiac sympathetic activity was significantly higher (p = 0.023) and BRS was significantly lower (p = 0.022) in the hypertension group than in the control group. During wakefulness, the results were similar although some of the above findings were absent. Autonomic imbalance, particularly impaired baroreflex, plays a more significant role in younger patients with hypertension. The nREM stage may be suitable for gaining insights into the relevant mechanisms.

Effect of sleep deprivation and NREM sleep stage on physiological brain pulsations

Introduction

Sleep increases brain fluid transport and the power of pulsations driving the fluids. We investigated how sleep deprivation or electrophysiologically different stages of non-rapid-eye-movement (NREM) sleep affect the human brain pulsations.

Methods

Fast functional magnetic resonance imaging (fMRI) was performed in healthy subjects (n = 23) with synchronous electroencephalography (EEG), that was used to verify arousal states (awake, N1 and N2 sleep). Cardiorespiratory rates were verified with physiological monitoring. Spectral power analysis assessed the strength, and spectral entropy assessed the stability of the pulsations.

Results

In N1 sleep, the power of vasomotor (VLF < 0.1 Hz), but not cardiorespiratory pulsations, intensified after sleep deprived vs. non-sleep deprived subjects. The power of all three pulsations increased as a function of arousal state (N2 > N1 > awake) encompassing brain tissue in both sleep stages, but extra-axial CSF spaces only in N2 sleep. Spectral entropy of full band and respiratory pulsations decreased most in N2 sleep stage, while cardiac spectral entropy increased in ventricles.

Discussion

In summary, the sleep deprivation and sleep depth, both increase the power and harmonize the spectral content of human brain pulsations.

Association between REM-related mild obstructive sleep apnea and common cardiometabolic diseases

PURPOSE

To explore the association between rapid eye movement-related obstructive sleep apnea (REM-OSA) and common cardiometabolic diseases (CMDs) in patients with mild OSA.

METHODS

This retrospective study was conducted by reviewing the medical records and polysomnograms (PSGs) of patients at Siriraj Hospital. The PSGs of patients diagnosed with mild OSA who had ≥ 15 min of REM sleep were included. REM-OSA was defined if the apnea-hypopnea index (AHI) in REM was ≥ 2 times that of non-REM. Common CMDs included coronary artery disease, stroke, heart failure, diabetes mellitus, and hypertension.

RESULTS

The data of 518 patients with a mean age of 48.3 years, 198 males, and mean AHI of 9.8 events/h were analyzed in this study. When compared with the control group, the REM-OSA group (308 patients) were predominantly female (72%), overweight (62%), and had more severe oxygen desaturation, p-value < 0.001. CMDs were significantly more common in the REM-OSA group than in the controls [odds ratio (OR) 1.52, 95% confidence interval 1.04-2.21, p-value = 0.029]. Patients with a REM AHI of ≥ 20 events/h were significantly associated with hypertension compared to those with a REM AHI of < 20 events/h, p-value = 0.001. However, these associations were found not to be statistically significant after controlling for age, sex, BMI, and prevalent coexisting CMD (OR = 1.13, 95% CI: 0.72-1.76, p-value = 0.605).

CONCLUSION

Common CMDs, particularly HT, tend to show an association with REM-OSA in patients with mild OSA, but this association did not reach statistically significant levels.

Autonomic dysregulation during sleep in Parkinsonian spectrum disorders - A proof of concept

INTRODUCTION

Autonomic dysfunction is common in α-synucleinopathies such as Lewy Body dementias (LBD), Parkinson's disease (PD), and isolated REM Sleep Behavior Disorder (iRBD). We analyzed pulse-rate changes during sleep to index autonomic nervous system (ANS) dysfunction in patients with α-synucleinopathies vs. non-synucleinopathy groups expected to have normal ANS function.

METHODS

Patients with LBD (n = 16), PD (PD, n = 14) or iRBD (n = 12) were compared to the non-synucleinopathy groups Alzheimers disease dementia (ADem, n = 26), mild cognitive impairment (MCI, n = 34) or controls (CG, n = 54). Sleep Profiler was used to derive a sleep autonomic activation index (AAI), i.e., ≥6 beat-per-minute increase/decrease, pulse rate coefficient of variation (PR-CV), and automated sleep staging with sleep-spindles and non-REM hypertonia (NRH). Analysis included statistical group comparisons and receiver operating characteristics curves to determine optimal classification of groups.

RESULTS

AAI and PR-CV were moderately correlated across all recordings (rs = 0.58, P < 0.0001), except in the LBD and PD groups. AAI but not PR-CV differentiated the LBD, PD and iRBD from non-Parkinsonian groups. AAI was decreased in LBD and PD patients compared to the CG (p < 0.003) and MCI (p < 0.03). AAI decreased based on age and its receiver operating characteristic area under the curve ranged from 0.63 to 0.75. AAI had a weak negative correlation to NRH (rs ≤ -0.26) but not sleep-spindles.

CONCLUSION

Synucleinopathy-related ANS dysfunction can reasonably discriminate prodromal and manifest PD/LBD diseased groups from non-synucleinopathies. Further studies incorporating AAI into a multivariate classifier of neurodegenerative disorders based on sleep characteristics acquired in the patient's home are planned.

The 24-h activity cycle and cardiovascular outcomes: establishing biological plausibility using arterial stiffness as an intermediate outcome

This review proposes a biologically plausible working model for the relationship between the 24-h activity cycle (24-HAC) and cardiovascular disease. The 24-HAC encompasses moderate-to-vigorous physical activity (MVPA), light physical activity, sedentary behavior (SB), and sleep. MVPA confers the greatest relative cardioprotective effect, when considering MVPA represents just 2% of the day if physical activity guidelines (30 min/day) are met. While we have well-established guidelines for MVPA, those for the remaining activity behaviors are vague. The vague guidelines are attributable to our limited mechanistic understanding of the independent and additive effects of these behaviors on the cardiovascular system. Our proposed biological model places arterial stiffness, a measure of vascular aging, as the key intermediate outcome. Starting with prolonged exposure to SB or static standing, we propose that the reported transient increases in arterial stiffness are driven by a cascade of negative hemodynamic effects following venous pooling. The subsequent autonomic, metabolic, and hormonal changes further impair vascular function. Vascular dysfunction can be offset by using mechanistic-informed interruption strategies and by engaging in protective behaviors throughout the day. Physical activity, especially MVPA, can confer protection by chronically improving endothelial function and associated protective mechanisms. Conversely, poor sleep, especially in duration and quality, negatively affects hormonal, metabolic, autonomic, and hemodynamic variables that can confound the physiological responses to next-day activity behaviors. Our hope is that the proposed biologically plausible working model will assist in furthering our understanding of the effects of these complex, interrelated activity behaviors on the cardiovascular system.

Chronological distribution of readings in ambulatory blood pressure monitoring exams affects the nighttime average and the magnitude of blood pressure dipping

STUDY OBJECTIVES

Averaged nighttime blood pressure (BP) is superior to daytime BP for cardiovascular risk stratification, and the relative change between daytime/nighttime BP (dipping%) significantly predicts cardiovascular risk. Newer reports suggest that 4 measurements at night may be enough for cardiovascular risk stratification. Since BP oscillates across the night, the temporal distribution of measurements across the night may impact nighttime BP and dipping%. Therefore, we compared average nighttime BP and dipping% when using measurements in the first half (1st-half), second (2nd-half), and a combination of both (combined).

METHODS

Forty-three (17 females and twenty-six males) midlife adults aged 50±10 years old wore an ambulatory BP monitor for 24 hours at home, programmed to measure BP every 20 minutes when scheduled for daytime and every 30 minutes during a self-selected 8-hour nighttime for time-in-bed. We compared the nighttime BP averages and dipping% when using either the first four measurements from the 1st-half or 2nd-half of the nighttime and combined.

RESULTS

Nighttime Systolic BP was significantly different across 1st-half, 2nd-half, and combined (111±9 vs.107±11 vs. 109±9 mmHg, p<0.01), respectively, with significant pairwise differences across all categories (p<0.01 for each). Systolic BP dipping% was significantly different across 1st-half, 2nd-half, and combined (9.9±5.5 vs.13.5±6.4 vs. 11.7±5.0 %, p<0.01), respectively, with significant pairwise differences across all categories (p<0.01 for each. Diastolic BP and diastolic dipping% were similar across the three different bins.

CONCLUSION

In midlife adults, systolic nighttime BP and dipping% may depend upon when BP measurements are taken during the night.

Oscillation of Sympathetic Activity in Patients with Obstructive Sleep Apnea during the First Hour of Sleep

(1) Background: Snoring is a cardinal symptom of obstructive sleep apnea (OSA) and has been suggested to potentially increase sympathetic activity. On the other hand, sleep itself usually leads to a decrease in sympathetic activity. Heart rate variability (HRV) analysis is a non-invasive technique used to assess autonomic nervous system function. However, there is limited research on the combined impact of sleep and snoring on sympathetic activity in individuals with OSA, particularly during the first hour of sleep (non-rapid eye movement sleep). The current study aims to investigate the net effect of sleep and snoring on sympathetic activity and explore factors that might contribute to increased sympathetic activity in individuals with OSA during the first hour of sleep. (2) Methods: The participants were referred from the outpatient department for OSA diagnosis and underwent whole-night polysomnography (PSG). Electrocardiogram (EKG) data from the PSG were downloaded for HRV analysis. HRV measurements were conducted in both the time and frequency domain, including the root mean square of successive differences between normal heartbeats (RMSSD) and the ratio of the absolute power of the low-frequency (LF) band (0.04-0.15 Hz) to the absolute power of the high-frequency (HF) band (0.15-0.4 Hz) (LF/HF ratio), respectively. (3) Results: A total of 45 participants (38 men and 7 women) were included in the analysis. The RMSSD gradually increased from 0-5 min to 50-60 min (p = 0.024), while the LF/HF ratio decreased (p < 0.001) during the first hour of sleep (non-rapid eye movement sleep). The LF/HF ratios of the "S" (snoring) episodes were compared with those of the pre-S episodes. An elevated LF/HF ratio during the S episode was associated with the first snoring episode occurring more than 20 min after lying down to sleep (Odds ratio, OR = 10.9, p = 0.004) and with patients diagnosed with severe OSA (OR = 5.01, p = 0.045), as determined by logistic regression. (4) Conclusions: The study observed an increase in the value of RMSSD and a decrease in the value of the LF/HF ratio during the first hour of sleep for patients with OSA. Higher LF/HF ratios were associated with the first occurrence of snoring while lying down for more than 20 min and with patients with severe OSA.

Relationship between slow-wave sleep and serum γ-glutamine transaminase in non-obese men with obstructive sleep apnea-hypopnea syndrome

BACKGROUND

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is a disease characterized with intermittent hypoxia and sleep fragmentation. Obesity and gender are major risk factors for the onset of OSAHS. Previous studies on obese men with OSAHS have been performed, while few studies on non-obese men with OSAHS have been carried out. The purpose of this study was to explore the clinical characteristics of polysomnography and blood biochemical indexes in non-obese men with OSAHS and to identify the possible influencing factors.

METHODS

This retrospective study included patients with OSAHS who underwent polysomnography in our hospital. General clinical data such as overnight polysomnography and biochemical indicators were recorded. The patients were divided into two groups according to the apnea-hypopnea index (AHI): mild to moderate OSAHS and severe OSAHS. The differences in biochemical parameters such as the levels of γ-glutamine transaminase (GGT), triglyceride (TG), glucose (GLU), and sleep structure parameters such as N1, N2, slow-wave sleep (SWS), and rapid eye movement (REM) sleep were compared and analyzed. Spearman correlation analysis and logistic regression were used to identify the risk factors of non-obese men with OSAHS. ROC curves were used to evaluate the predictive ability of SWS and GGT on disease severity.

RESULTS

Of 94 non-obese men with OSAHS, 49 had mild to moderate OSAHS and 45 had severe OSAHS. Our data suggested that the levels of low oxygen saturation (L-SaO2), mean oxygen saturation (M-SaO2), SWS, and GGT were significantly changed in the mild to moderate OSAHS group compared with the severe group (p < 0.05). For patients with OSAHS, the proportion of SWS in the group with severe OSAHS was higher than that in the mild to moderate group (p < 0.05), and the serum GGT enzyme levels were significantly elevated in the severe group compared to the mild to moderate group (p < 0.05). Using logistic regression analyses, our data revealed that both SWS and GGT enzyme levels were independent risk factors for AHI (p < 0.05). In addition, the results of correlation analysis indicated that SWS was related to triglyceride (TG), total cholesterol (TC), apolipoprotein E (APOE), and triglyceride glucose (TyG) index (p < 0.05); GGT was related to TG, TC, APOE, and TyG index (p < 0.05). Furthermore, SWS was independently associated with GGT (p < 0.05). The area under the ROC curve plotted with the combined coefficient of SWS and serum GGT was 0.728, which was predictive of the disease severity.

CONCLUSIONS

These results suggest that SWS and GGT are independent associated factors of the severity of the disease. However, TyG index was not an independent associated factor of the severity of disease in non-obese men with OSAHS. In addition, SWS and GGT were negatively correlated. SWS combined with serum GGT may be predictive of the severity of the disease. This study may have added to our understanding of the pathogenesis of OSAHS in non-obese men.

Sleep disturbance, but not depression severity, is associated with inflammation in children and adolescents

STUDY OBJECTIVES

We aimed to examine the association between self-rated and clinician-rated sleep disturbances and C-reactive protein (CRP), an objective marker of inflammation, in pediatric depression.

METHODS

Two hundred fifty-six children and adolescents (15.2 ± 1.6 y, 72.3% female) with moderate to severe symptoms of depression participated in the study. Sleep disturbances were assessed by self-reports (Insomnia Severity Index) and clinician ratings (Kiddie-Schedule for Affective Disorder and Schizophrenia), inflammation by plasma CRP levels.

RESULTS

Higher levels of CRP correlated positively with clinician-rated middle insomnia and hypersomnia. After adjusting for control variables (body mass index, tobacco, alcohol, stress, age, sex, antidepressants, sleep medication, depression severity), regression models confirmed the significant association of clinician-rated hypersomnia and middle insomnia symptoms with elevated CRP levels. In the adjusted regression models, other clinician-rated manifestations of sleep disturbance (eg, initial insomnia) and insomnia self-ratings were not significantly associated with CRP. Body mass index correlated positively with CRP, but body mass index had no mediating effect on the associations between sleep disturbances and CRP. We did not find an association between depression severity, assessed by the Children's Depression Rating Scale-Revised, and CRP.

CONCLUSIONS

Results of the present study indicate a significant association of hypersomnia and middle insomnia symptoms with CRP in pediatric depression, not linked to alterations in the body mass index.

CITATION

Strumberger MA, Häberling I, Emery S, et al. Sleep disturbance, but not depression severity, is associated with inflammation in children and adolescents. J Clin Sleep Med. 2023;19(10):1775-1784.

Neurofluid coupling during sleep and wake states

BACKGROUND

In clinical populations, the movement of cerebrospinal fluid (CSF) during sleep is a growing area of research with potential mechanistic connections in both neurodegenerative (e.g., Alzheimer's Disease) and neurodevelopmental disorders. However, we know relatively little about the processes that influence CSF movement. To inform clinical intervention targets this study assesses the coupling between (a) real-time CSF movement, (b) neuronal-driven movement, and (c) non-neuronal systemic physiology driven movement.

METHODS

This study included eight young, healthy volunteers, with concurrently acquired neurofluid dynamics using functional Magnetic Resonance Imaging (MRI), neural activity using Electroencephalography (EEG), and non-neuronal systemic physiology with peripheral functional Near-Infrared Spectroscopy (fNIRS). Neuronal and non-neuronal drivers were assessed temporally; wherein, EEG measured slow wave activity that preceded CSF movement was considered neuronally driven. Similarly, slow wave oscillations (assessed via fNIRS) that coupled with CSF movement were considered non-neuronal systemic physiology driven.

RESULTS AND CONCLUSIONS

Our results document neural contributions to CSF movement were only present during light NREM sleep but low-frequency non-neuronal oscillations were strongly coupled with CSF movement in all assessed states - awake, NREM-1, NREM-2. The clinical/research implications of these findings are two-fold. First, neuronal-driven oscillations contribute to CSF movement outside of deep sleep (NREM-3); therefore, interventions aimed at increasing CSF movement may yield meaningful increases with the promotion of NREM sleep more generally - a focus on NREM S3 may not be needed. Second, non-neuronal systemic oscillations contribute across wake and sleep stages; therefore, interventions may increase CSF movement by manipulating systemic physiology.

REM-OSA as a Tool to Understand Both the Architecture of Sleep and Pathogenesis of Sleep Apnea-Literature Review

Sleep is a complex physiological state, which can be divided into the non-rapid eye movement (NREM) phase and the REM phase. Both have some unique features and functions. This difference is best visible in electroencephalography recordings, respiratory system activity, arousals, autonomic nervous system activity, or metabolism. Obstructive sleep apnea (OSA) is a common condition characterized by recurrent episodes of pauses in breathing during sleep caused by blockage of the upper airways. This common condition has multifactorial ethiopathogenesis (e.g., anatomical predisposition, sex, obesity, and age). Within this heterogenous syndrome, some distinctive phenotypes sharing similar clinical features can be recognized, one of them being REM sleep predominant OSA (REM-OSA). The aim of this review was to describe the pathomechanism of REM-OSA phenotype, its specific clinical presentation, and its consequences. Available data suggest that in this group of patients, the severity of specific cardiovascular and metabolic complications is increased. Due to the impact of apneas and hypopneas predominance during REM sleep, patients are more prone to develop hypertension or glucose metabolism impairment. Additionally, due to the specific function of REM sleep, which is predominantly fragmented in the REM-OSA, this group presents with decreased neurocognitive performance, reflected in memory deterioration, and mood changes including depression. REM-OSA clinical diagnosis and treatment can alleviate these outcomes, surpassing the traditional treatment and focusing on a more personalized approach, such as using longer therapy of continuous positive airway pressure or oral appliance use.

Heat of the night: sleep disturbance activates inflammatory mechanisms and induces pain in rheumatoid arthritis

Sleep has a homeostatic role in the regulation of the immune system and serves to constrain activation of inflammatory signalling and expression of cellular inflammation. In patients with rheumatoid arthritis (RA), a misaligned inflammatory profile induces a dysregulation of sleep-wake activity, which leads to excessive inflammation and the induction of increased sensitivity to pain. Given that multiple biological mechanisms contribute to sleep disturbances (such as insomnia), and that the central nervous system communicates with the innate immune system via neuroendocrine and neural effector pathways, potential exists to develop prevention opportunities to mitigate the risk of insomnia in RA. Furthermore, understanding these risk mechanisms might inform additional insomnia treatment strategies directed towards steering and reducing the magnitude of the inflammatory response, which together could influence outcomes of pain and disease activity in RA.

Sex Differences in Neurovascular Control: Implications for Obstructive Sleep Apnea

Patients with obstructive sleep apnea (OSA) have a heightened risk of developing cardiovascular diseases, namely hypertension. While seminal evidence indicates a causal role for sympathetic nerve activity in the hypertensive phenotype commonly observed in patients with OSA, no studies have investigated potential sex differences in the sympathetic regulation of blood pressure in this population. Supporting this exploration are large-scale observational data, as well as controlled interventional studies in healthy adults, indicating that sleep disruption increases blood pressure to a greater extent in females relative to males. Furthermore, females with severe OSA demonstrate a more pronounced hypoxic burden (i.e., disease severity) during rapid eye movement sleep when sympathetic nerve activity is greatest. These findings would suggest that females are at greater risk for the hemodynamic consequences of OSA and related sleep disruption. Accordingly, the purpose of this review is three-fold: (1) to review the literature linking sympathetic nerve activity to hypertension in OSA, (2) to highlight recent experimental data supporting the hypothesis of sex differences in the regulation of sympathetic nerve activity in OSA, and (3) to discuss the potential sex differences in peripheral adrenergic signaling that may contribute to, or offset, cardiovascular risk in patients with OSA.

Short-term blood pressure variability as a potential therapeutic target for kidney disease

Short-term blood pressure variability (BPV) measured with ambulatory blood pressure (BP) monitoring has been demonstrated to be significant in predicting various clinical outcomes. Short-term BPV is distinguished from long-term BPV based on the time interval in which BP fluctuations are measured. Increased short-term BPV has been linked to detrimental effects on the microvascular structure and contributes to subclinical organ damage in the heart, blood vessels, and kidneys, regardless of the average 24-h BP levels. Short-term BPV can be defined by various measures, including calculated metrics (standard deviation, coefficient of variation, average real variability, weighted standard deviation, variability independent of the mean) or dipping patterns. Nevertheless, the additional role of short-term BPV beyond the predictive value of average 24-h BPs or established risk factors for cardiovascular disease and kidney disease remains unclear. In particular, longitudinal studies that evaluate the association between short-term BPV and kidney function impairment are limited and no conclusive data exist regarding which short-term BPV indicators most accurately reflect the prognosis of kidney disease. The issue of how to treat BPV in clinical practice is another concern that is frequently raised. This paper presents a review of the evidence for the prognostic role of short-term BPV in kidney outcomes. Additionally, this review discusses the remaining concerns about short-term BPV that need to be further investigated as an independent risk modifier.

Sleep duration and cognitive function among older adults with chronic kidney disease: results from the National Health and Nutrition Examination Survey (2011-2014)

BACKGROUND

Short and long sleep durations are associated with cognitive dysfunction. Given the increased prevalence of sleep abnormalities in the chronic kidney disease (CKD) population, we tested whether the association between sleep duration and cognitive function differed between older adults with and without CKD.

METHODS

This was a study of 3215 older adults (age ≥60 years) enrolled in the National Health and Nutrition Examination Survey (2011-14) evaluating sleep duration, cognitive function (immediate recall, delayed recall, verbal fluency, executive function and processing speed and global cognition) and kidney function. We quantified the association between sleep duration and cognitive function using linear regression and tested whether the associations differed among those with CKD and without using a Wald test for interaction.

RESULTS

Among 3215 participants, 13.3% reported 2-5 hours of sleep/day, 75.2% reported 6-8 hours, and 11.5% reported ≥9 hours. Persons with CKD were more likely to sleep ≥9 hours [odds ratio 1.73 (95% confidence interval 1.22-2.46)]. Among participants with CKD, those with a sleep duration ≥9 hours demonstrated worse global cognitive function (P for interaction = .01), immediate recall (P for interaction = .01) and verbal fluency (P for interaction = .004) than those with a sleep duration of 6-8 h; no differences were observed for participants with CKD who slept 2-5 hours. Among participants without CKD, sleep was not associated with any measures of cognitive function.

CONCLUSIONS

Longer sleep duration is associated with worse cognitive function only among persons with CKD, and global cognition, delayed recall and verbal fluency are particularly affected. Studies should identify interventions to improve sleep patterns and quality in this population.

From MEG to clinical EEG: evaluating a promising non-invasive estimator of defense-related muscle sympathetic nerve inhibition

Sudden, unexpected stimuli can induce a transient inhibition of sympathetic vasoconstriction to skeletal muscle, indicating a link to defense reactions. This phenomenon is relatively stable within, but differs between, individuals. It correlates with blood pressure reactivity which is associated with cardiovascular risk. Inhibition of muscle sympathetic nerve activity (MSNA) is currently characterized through invasive microneurography in peripheral nerves. We recently reported that brain neural oscillatory power in the beta spectrum (beta rebound) recorded with magnetoencephalography (MEG) correlated closely with stimulus-induced MSNA inhibition. Aiming for a clinically more available surrogate variable reflecting MSNA inhibition, we investigated whether a similar approach with electroencephalography (EEG) can accurately gauge stimulus-induced beta rebound. We found that beta rebound shows similar tendencies to correlate with MSNA inhibition, but these EEG data lack the robustness of previous MEG results, although a correlation in the low beta band (13-20 Hz) to MSNA inhibition was found (p = 0.021). The predictive power is summarized in a receiver-operating-characteristics curve. The optimum threshold yielded sensitivity and false-positive rate of 0.74 and 0.33 respectively. A plausible confounder is myogenic noise. A more complicated experimental and/or analysis approach is required for differentiating MSNA-inhibitors from non-inhibitors based on EEG, as compared to MEG.

Cross-sectional interrelationships between chronotype, obstructive sleep apnea and blood pressure in a middle-aged community cohort

Chronotype is linked to adverse health measures and may have important associations with obstructive sleep apnea and blood pressure, but data are limited. This study aimed to determine the separate and combined associations of chronotype with obstructive sleep apnea and blood pressure in a middle-aged community population. Adults (n = 811) from the Raine Study (female = 59.2%; age mean [range] = 56.6 [42.1-76.6] years) were assessed for chronotype (Morningness-Eveningness Questionnaire), blood pressure and hypertension (doctor diagnosed or systolic blood pressure ≥ 140 mmHg and/or diastolic ≥ 90 mmHg), and obstructive sleep apnea at different in-laboratory apnea-hypopnea index thresholds (5, 10, 15 events per hr). Linear and logistic regression models examined relationships between chronotype and the presence and severity of obstructive sleep apnea, blood pressure, hypertension, and blood pressure stratified by obstructive sleep apnea severity at above-mentioned apnea-hypopnea index thresholds. Covariates included age, sex, body mass index, alcohol consumption, smoking, physical activity, sleep duration, anti-hypertensive medication, insomnia, and depressive symptoms. Most participants were categorised as morning (40%) or intermediate (43%), with 17% meeting criteria for evening chronotypes. Participants with apnea-hypopnea index ≥ 15 events per hr and morning chronotype had higher systolic (9.9 mmHg, p < 0.001) and a trend for higher diastolic blood pressure (3.4 mmHg, p = 0.07) compared with those with an evening chronotype, and higher systolic blood pressure compared with those with an intermediate chronotype (4.8 mmHg, p = 0.03). Across chronotype categories, no differences in systolic or diastolic blood pressure or odds of hypertension were found at apnea-hypopnea index thresholds of ≥ 5 or ≥ 10 events per hr. Among participants with apnea-hypopnea index ≥ 15 events per hr, systolic blood pressure is higher in those with a morning chronotype than evening and intermediate chronotypes. Assessment for morning chronotype may improve risk stratification for hypertension in patients with obstructive sleep apnea.

The stress of losing sleep: Sex-specific neurobiological outcomes

Sleep is a vital and evolutionarily conserved process, critical to daily functioning and homeostatic balance. Losing sleep is inherently stressful and leads to numerous detrimental physiological outcomes. Despite sleep disturbances affecting everyone, women and female rodents are often excluded or underrepresented in clinical and pre-clinical studies. Advancing our understanding of the role of biological sex in the responses to sleep loss stands to greatly improve our ability to understand and treat health consequences of insufficient sleep. As such, this review discusses sex differences in response to sleep deprivation, with a focus on the sympathetic nervous system stress response and activation of the hypothalamic-pituitary-adrenal (HPA) axis. We review sex differences in several stress-related consequences of sleep loss, including inflammation, learning and memory deficits, and mood related changes. Focusing on women's health, we discuss the effects of sleep deprivation during the peripartum period. In closing, we present neurobiological mechanisms, including the contribution of sex hormones, orexins, circadian timing systems, and astrocytic neuromodulation, that may underlie potential sex differences in sleep deprivation responses.

Effect of Aerobic Exercise Training on Sleep and Core Temperature in Middle-Aged Women with Chronic Insomnia: A Randomized Controlled Trial

BACKGROUND

Exercise represents a viable non-pharmacological intervention to help treating insomnia but the interaction mechanisms between sleep and physical activity still remain poorly understood. The aim of this study was to investigate the effect of a aerobic exercise training intervention on sleep and core temperature.

METHODS

Twenty-four adult women suffering from insomnia participated in this study. They were randomized into an exercise group and a control group. Aerobic exercise training consisted in moderate to vigorous aerobic exercise training for 12 weeks. Outcome measures included both subjective (Insomnia Severity Index, ISI) and objective (actigraphy recordings) sleep quality assessments, and core body temperature continuously recorded for a minimum 24 h.

RESULTS

The exercise group showed a decrease in ISI (p < 0.001) and in various objective sleep parameters. The core temperature batyphase value was lowered (p = 0.037) whereas its amplitude was larger (p = 0.002). We also found a tight correlation between the evolution of insomnia and the evolution of mean night-time core temperature and batyphase values.

CONCLUSIONS

A moderate to vigorous aerobic exercise program appears to be an effective non-drug therapy for improving sleep in women with insomnia. In addition, exercise programs should aim to increase core body temperature during practice to induce sleep-promoting adaptations and rebound.

Pathophysiology of the Nondipping Blood Pressure Pattern

The nondipping blood pressure (BP) pattern corresponds to a disruption in the circadian BP rhythm with an insufficient decrease in BP levels during nighttime sleep as observed using 24-hour ambulatory BP monitoring. Patients with nondipping BP pattern have poorer renal and cardiovascular outcomes, independent of their average 24-hour BP levels. The pathophysiology of nondipping BP is complex and involves numerous mechanisms: perturbations of (1) the circadian rhythm, (2) the autonomic nervous system, and (3) water and sodium regulation. This review provides an outline of the pathways potentially involved in the nondipping BP profile in different conditions. A recent hypothesis is also discussed involving the role of gut microbiota in the dipping/nondipping patterns, via the fecal diet-derived short chain fatty acids.

Mammalian NREM and REM sleep: Why, when and how

This report proposes that fish use the spinal-rhombencephalic regions of their brain to support their activities while awake. Instead, the brainstem-diencephalic regions support the wakefulness in amphibians and reptiles. Lastly, mammals developed the telencephalic cortex to attain the highest degree of wakefulness, the cortical wakefulness. However, a paralyzed form of spinal-rhombencephalic wakefulness remains in mammals in the form of REMS, whose phasic signs are highly efficient in promoting maternal care to mammalian litter. Therefore, the phasic REMS is highly adaptive. However, their importance is low for singletons, in which it is a neutral trait, devoid of adaptive value for adults, and is mal-adaptive for marine mammals. Therefore, they lost it. The spinal-rhombencephalic and cortical wakeful states disregard the homeostasis: animals only attend their most immediate needs: foraging defense and reproduction. However, these activities generate allostatic loads that must be recovered during NREMS, that is a paralyzed form of the amphibian-reptilian subcortical wakefulness. Regarding the regulation of tonic REMS, it depends on a hypothalamic switch. Instead, the phasic REMS depends on an independent proportional pontine control.

Sleep staging in the ICU with heart rate variability and breathing signals. An exploratory cross-sectional study using deep neural networks

Introduction: To measure sleep in the intensive care unit (ICU), full polysomnography is impractical, while activity monitoring and subjective assessments are severely confounded. However, sleep is an intensely networked state, and reflected in numerous signals. Here, we explore the feasibility of estimating conventional sleep indices in the ICU with heart rate variability (HRV) and respiration signals using artificial intelligence methods Methods: We used deep learning models to stage sleep with HRV (through electrocardiogram) and respiratory effort (through a wearable belt) signals in critically ill adult patients admitted to surgical and medical ICUs, and in age and sex-matched sleep laboratory patients Results: We studied 102 adult patients in the ICU across multiple days and nights, and 220 patients in a clinical sleep laboratory. We found that sleep stages predicted by HRV- and breathing-based models showed agreement in 60% of the ICU data and in 81% of the sleep laboratory data. In the ICU, deep NREM (N2 + N3) proportion of total sleep duration was reduced (ICU 39%, sleep laboratory 57%, p < 0.01), REM proportion showed heavy-tailed distribution, and the number of wake transitions per hour of sleep (median 3.6) was comparable to sleep laboratory patients with sleep-disordered breathing (median 3.9). Sleep in the ICU was also fragmented, with 38% of sleep occurring during daytime hours. Finally, patients in the ICU showed faster and less variable breathing patterns compared to sleep laboratory patients Conclusion: The cardiovascular and respiratory networks encode sleep state information, which, together with artificial intelligence methods, can be utilized to measure sleep state in the ICU.

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.

Sleep fragmentation during rapid eye movement sleep and hypertension in obstructive sleep apnea

OBJECTIVE

Sleep fragmentation determined by repetitive arousals from sleep in obstructive sleep apnea (OSA) is associated with hypertension. We aimed to quantify the independent association of arousals during rapid eye movement (REM)/non-rapid eye movement (NREM) sleep with prevalent hypertension.

METHODS

We included adults with 4 h of total sleep time and at least 30 min of REM sleep obtained from overnight in-laboratory polysomnography. Logistic regression models were fitted to explore the association between arousals during REM/NREM sleep and prevalent hypertension. All models controlled for OSA metrics and arousals during NREM/REM sleep, either by statistical adjustment or by stratification.

RESULTS

The sample comprised of 11 643 patients, of which 10 055 were OSA patients. Fully adjusted models demonstrated significant dose-relationships between arousal index during REM sleep (AI-REM) and prevalent hypertension (P trend = 0.002). The higher relative odds of prevalent hypertension were most evident with AI-REM > 40 events/h. In OSA patients with arousal index during NREM sleep (AI-NREM) <15 events/h, every10-unit increase in the AI-REM was associated with 18% higher odds of hypertension (odds ratio, 1.18; 95% confidence interval, 1.11-1.27) in OSA. On the contrary, AI-NREM was not a significant predictor of hypertension in any of the models.

CONCLUSIONS

Our findings indicate that arousals during REM sleep are associated with prevalent hypertension. This is clinically relevant because treatment of OSA is often limited to the first half of the sleep period leaving most of sleep fragmentation during REM sleep untreated.

Sleep Arousal-Related Ventricular Repolarization Lability Is Associated With Cardiovascular Mortality in Older Community-Dwelling Men

BACKGROUND

Sleep is fragmented by brief arousals, and excessive arousal burden has been linked to increased cardiovascular (CV) risk, but mechanisms are poorly understood.

RESEARCH QUESTION

Do arousals trigger cardiac ventricular repolarization lability that may predispose people to long-term cardiovascular mortality?

STUDY DESIGN AND METHODS

This study analyzed 407,541 arousals in the overnight polysomnograms of 2,558 older men in the Osteoporotic Fractures in Men sleep study. QT and RR intervals were measured beat-to-beat starting 15 s prior to arousal onset until 15 s past onset. Ventricular repolarization lability was quantified by using the QT variability index (QTVi).

RESULTS

During 10.1 ± 2.5 years of follow-up, 1,000 men died of any cause, including 348 CV deaths. During arousals, QT and RR variability increased on average by 5 and 55 ms, respectively, resulting in a paradoxical transient decrease in QTVi from 0.07 ± 1.68 to -1.00 ± 1.68. Multivariable Cox proportional hazards analysis adjusted for age, BMI, cardiovascular and respiratory risk factors, sleep-disordered breathing and arousal, diabetes, and Parkinson disease indicated that excessive QTVi during arousal was independently associated with all-cause and CV mortality (all-cause hazard ratio, 1.20 [95% CI, 1.04-1.38; P = .012]; CV hazard ratio, 1.29 [95% CI, 1.01 -1.65; P = .043]).

INTERPRETATION

Arousals affect ventricular repolarization. A disproportionate increase in QT variability during arousal is associated with an increased all-cause and CV mortality and may reflect ventricular repolarization maladaptation to the arousal stimulus. Whether arousal-related QTVi can be used for more tailored risk stratification warrants further study, including evaluating whether arousal suppression attenuates ventricular repolarization lability and reduces subsequent mortality.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov; No.: NCT00070681; URL: www.

CLINICALTRIALS

gov.

Peripheral blood flow estimated by laser doppler flowmetry provides additional information about sleep state beyond that provided by pulse rate variability

Pulse rate variability (PRV), derived from Laser Doppler flowmetry (LDF) or photoplethysmography, has recently become widely used for sleep state assessment, although it cannot identify all the sleep stages. Peripheral blood flow (BF), also estimated by LDF, may be modulated by sleep stages; however, few studies have explored its potential for assessing sleep state. Thus, we aimed to investigate whether peripheral BF could provide information about sleep stages, and thus improve sleep state assessment. We performed electrocardiography and simultaneously recorded BF signals by LDF from the right-index finger and ear concha of 45 healthy participants (13 women; mean age, 22.5 ± 3.4 years) during one night of polysomnographic recording. Time- and frequency-domain parameters of peripheral BF, and time-domain, frequency-domain, and non-linear indices of PRV and heart rate variability (HRV) were calculated. Finger-BF parameters in the time and frequency domains provided information about different sleep stages, some of which (such as the difference between N1 and rapid eye movement sleep) were not revealed by finger-PRV. In addition, finger-PRV patterns and HRV patterns were similar for most parameters. Further, both finger- and ear-BF results showed 0.2-0.3 Hz oscillations that varied with sleep stages, with a significant increase in N3, suggesting a modulation of respiration within this frequency band. These results showed that peripheral BF could provide information for different sleep stages, some of which was complementary to the information provided by PRV. Furthermore, the combination of peripheral BF and PRV may be more advantageous than HRV alone in assessing sleep states and related autonomic nervous activity.

Heart rate variability in different sleep stages is associated with metabolic function and glycemic control in type 2 diabetes mellitus

Introduction: Autonomic nervous system (ANS) plays an important role in the exchange of metabolic information between organs and regulation on peripheral metabolism with obvious circadian rhythm in a healthy state. Sleep, a vital brain phenomenon, significantly affects both ANS and metabolic function. Objectives: This study investigated the relationships among sleep, ANS and metabolic function in type 2 diabetes mellitus (T2DM), to support the evaluation of ANS function through heart rate variability (HRV) metrics, and the determination of the correlated underlying autonomic pathways, and help optimize the early prevention, post-diagnosis and management of T2DM and its complications. Materials and methods: A total of 64 volunteered inpatients with T2DM took part in this study. 24-h electrocardiogram (ECG), clinical indicators of metabolic function, sleep quality and sleep staging results of T2DM patients were monitored. Results: The associations between sleep quality, 24-h/awake/sleep/sleep staging HRV and clinical indicators of metabolic function were analyzed. Significant correlations were found between sleep quality and metabolic function (|r| = 0.386 ± 0.062, p < 0.05); HRV derived ANS function showed strengthened correlations with metabolic function during sleep period (|r| = 0.474 ± 0.100, p < 0.05); HRV metrics during sleep stages coupled more tightly with clinical indicators of metabolic function [in unstable sleep: |r| = 0.453 ± 0.095, p < 0.05; in stable sleep: |r| = 0.463 ± 0.100, p < 0.05; in rapid eye movement (REM) sleep: |r| = 0.453 ± 0.082, p < 0.05], and showed significant associations with glycemic control in non-linear analysis [fasting blood glucose within 24 h of admission (admission FBG), |r| = 0.420 ± 0.064, p < 0.05; glycated hemoglobin (HbA1c), |r| = 0.417 ± 0.016, p < 0.05]. Conclusions: HRV metrics during sleep period play more distinct role than during awake period in investigating ANS dysfunction and metabolism in T2DM patients, and sleep rhythm based HRV analysis should perform better in ANS and metabolic function assessment, especially for glycemic control in non-linear analysis among T2DM patients.

Disturbed Sleep is Not Good for the Heart: A Narrative Review

Sleep-related breathing disorders, including obstructive sleep apnea (OSA) and central sleep apnea (CSA), have a major impact on cardiovascular function. It has shown an association with hypertension, coronary artery disease, cardiac arrhythmias, sudden cardiac death, and congestive heart failure (CHF). This review focuses on highlighting the relationship between sleep apnea and CHF. We discuss the underlying pathophysiology, which involves the mechanical, neurohormonal, and inflammatory mechanisms; in addition, the similarities and differentiating clinical features of OSA in patients with CHF and without CHF. We have also discussed several treatment strategies, including weight loss, continuous positive airway pressure (CPAP), supplemental oxygen therapy, theophylline, acetazolamide, mandibular advancement device, and hypoglossal nerve stimulation (HGNS). We conclude that since there are several overlapping clinical features in patients with OSA with Heart Failure (HF) and without HF, early detection and treatment are crucial to decrease the risk of HF, coronary artery disease, and stroke.

Postmorterm Computed Tomography and Autopsy to Confirm Sudden Death Due to Tracheal Compression by Mediastinal Fat Tissue in a Young Man With Obesity

A man in his early twenties with obesity was found dead in his apartment. The deceased was found naked and surrounded by empty bottles of electrolytes. An autopsy performed approximately 6 days postmortem and gross inspection revealed the absence of injury and no apparent extrinsic cause of death. It was decided to dissect to investigate the cause of death. The deceased had become morbidly obese (weight, 98 kg; height, 160 cm; body mass index, 38.3). Shortly before his death, he presented at a clinic complaining of gastric discomfort and heartburn, but other than hypertension (155/91 mmHg) no specific abnormality was found. He was normothermic (36.6℃), and his blood oxygen saturation was normal (97%). Postmortem computed tomography of the thorax revealed a mediastinal mass obstructing the trachea, an upper-airway obstruction, and a narrowed thoracic cavity due to upward compression by an enlarged fatty liver. Autopsy confirmed that the tracheal mass was fatty tissue within the thymus and that upward pressure from an enlarged fatty liver had compressed the thoracic cavity. The deceased likely developed nocturnal chronic hypoxia because of compression by the mediastinal fat mass as well as intermittent hypoxia because of obstructive sleep apnea when lying supine. Chronic and intermittent hypoxia, diabetes, and obesity activate the sympathetic nervous system, increasing the risk of hypertension, heart failure, and arrhythmias. Histological findings showed pulmonary congestion and edema, reflecting heart failure as well as myocardial fragmentation and waving, showing hyper-contraction and hyper-relaxation, respectively. Hypertension, feeling overheated, and myocardial hyper-contraction can be explained as sympathetic nerve over-activation. Intra-cardiac coagulation and a renal cortical pallor suggested subacute death from cardiogenic shock due to heart failure. Postmortem computed tomography before autopsy detected airway obstruction and revealed the cause and pathophysiology of unexpected death in a young man with morbid obesity. Therefore, this could be a potentially useful clinical practice for determining the cause of death postmortem.

Circadian Variations in Sympathetic Vasoconstriction in Older Adults with and Without Type 2 Diabetes

INTRODUCTION

An impact of the sympathetic nervous system in the higher rate of cardiovascular events in the early morning compared to the evening has been claimed. Augmented sympathetic vasoconstriction increases cardiovascular risk by augmenting pulse pressure and cardiac afterload. Type 2 diabetes (T2DM) further increases sympathetic neurovascular transduction and cardiovascular risk.

AIM

We assessed whether peripheral vasoconstriction triggered by a standardized sympathetic stressor is augmented at 6am vs 9pm in adults between 50-80 years with type 2 diabetes (T2DM50-80) vs healthy ones (H50-80).

METHODS

Mean values of sympathetic vasoconstrictor responsiveness (SVR), vascular conductance (VC), brachial artery blood flow, and mean arterial pressure were measured on the contralateral forearm over two 5-minute bouts of rest and handgrip-mediated sympathetic stimulation, respectively.

RESULTS

Although baseline VC values were lower (p < 0.01) in the morning vs evening in both groups, SVR values in response to sympathoexcitation were similar in H50-80 (- 0.43 ± 12.44 vs - 2.57 ± 11.63 %, p = 0.73) and T2DM50-80 (+6.64 ± 10.67 vs +5.21 ± 7.64 %, p = 0.90), but higher (p < 0.01) in T2DM50-80 vs H50-80 at both day hours. Individuals with T2DM reported positive SVR values and VC change-scores, while healthy individuals reported statistically different (p < 0.02) negative SVR values and VC change-scores.

CONCLUSION

Peripheral vasoconstriction triggered by a standardized sympathetic stressor is similar between morning and evening, regardless of T2DM and different baseline VC values. However, peripheral vasoconstriction responsiveness is blunted in individuals with T2DM as handgrip-mediated sympathoexcitation induces vasodilation in the contralateral forearm in adults with T2DM and vasoconstriction in healthy age-matched controls, highlighting a neurovascular response altered by T2DM.

[The phenomenon of awakening from sleep and underlying neurophysiological and autonomic mechanisms]

Current research has shown that sleep is not a global process evenly covering the entire brain. The heterogeneity of wakefulness levels in different parts of the brain and differences in their activation thresholds are especially pronounced during the transitions between sleep and wakefulness. During awakening, subcortical brain structures activate first, followed by sensory and motor cortical regions, whereas the associative cortex wakes up much later. Awakening, unlike falling asleep, is not a smooth process. It begins with a short-term sharp activation of the autonomic nervous system and some wake-promoting brain regions. The amplitude of this activity burst is out of proportion to obvious physiological needs and exceeds that observed in later periods of quiet wakefulness. The review discusses the similarities and differences between awakening from sleep and hibernation in hibernating rodents. Data on some clinical consequences of impaired awakening mechanisms are also provided.

Effects of Spinal Cord Injury Site on Cardiac Autonomic Regulation: Insight from Analysis of Cardiovascular Beat by Beat Variability during Sleep and Orthostatic Challenge

The goal of this study on Spinal Cord Injury (SCI) patients with cervical or thoracic lesion was to assess whether disturbances of ANS control, according to location, might differently affect vagal and sympatho-vagal markers during sleep and orthostatic challenge. We analyzed with linear and nonlinear techniques beat-by-beat RR and arterial pressure (and respiration) variability signals, extracted from a polysomnographic study and a rest-tilt test. We considered spontaneous or induced sympathetic excitation, as obtained shifting from non-REM to REM sleep or from rest to passive tilt. We obtained evidence of ANS cardiac (dys)regulation, of greater importance for gradually proximal location (i.e., cervical) SCI, compatible with a progressive loss of modulatory role of sympathetic afferents to the spinal cord. Furthermore, in accordance with the dual, vagal and sympathetic bidirectional innervation, the results suggest that vagally mediated negative feedback baroreflexes were substantially maintained in all cases. Conversely, the LF and HF balance (expressed specifically by normalized units) appeared to be negatively affected by SCI, particularly in the case of cervical lesion (group p = 0.006, interaction p = 0.011). Multivariate analysis of cardiovascular variability may be a convenient technique to assess autonomic responsiveness and alteration of functionality in patients with SCI addressing selectively vagal or sympathetic alterations and injury location. This contention requires confirmatory studies with a larger population.

Cardiovascular baroreflex circuit moonlights in sleep control

Sleep disturbances are strongly associated with cardiovascular diseases. Baroreflex, a basic cardiovascular regulation mechanism, is modulated by sleep-wake states. Here, we show that neurons at key stages of baroreflex pathways also promote sleep. Using activity-dependent genetic labeling, we tagged neurons in the nucleus of the solitary tract (NST) activated by blood pressure elevation and confirmed their barosensitivity with optrode recording and calcium imaging. Chemogenetic or optogenetic activation of these neurons promoted non-REM sleep in addition to decreasing blood pressure and heart rate. GABAergic neurons in the caudal ventrolateral medulla (CVLM)-a downstream target of the NST for vasomotor baroreflex-also promote non-REM sleep, partly by inhibiting the sympathoexcitatory and wake-promoting adrenergic neurons in the rostral ventrolateral medulla (RVLM). Cholinergic neurons in the nucleus ambiguous-a target of the NST for cardiac baroreflex-promoted non-REM sleep as well. Thus, key components of the cardiovascular baroreflex circuit are also integral to sleep-wake brain-state regulation.

Sleep characteristics associated with nocturnal blood pressure nondipping in healthy individuals: a systematic review

OBJECTIVE

The current literature investigating nocturnal blood pressure (BP) nondipping has largely focused on clinical populations, however, conditions such as hypertension, obstructive sleep apnoea and insomnia are recognized confounding factors for BP dipping. The exact mechanisms responsible for BP nondipping remain unclear, therefore, there is a need to investigate BP nondipping in healthy individuals to better understand the underlying mechanisms. This review identifies sleep characteristics that may contribute to BP nondipping in healthy individuals. It is anticipated that an understanding of the sleep characteristics that contribute to BP nondipping may inform future sleep-related behavioral interventions to ultimately reducing the burden of cardiovascular disease.

METHODS

The PubMed, Scopus and Web of Science databases were searched for relevant, English language, peer-reviewed publications (from inception to March 2022). The search identified 550 studies. After duplicates were removed, the titles and abstracts of the remaining 306 studies were screened. Of these, 250 studies were excluded leaving 56 studies to test for eligibility. Thirty-nine studies were excluded such that 17 studies fully met the inclusion criteria for the review.

RESULTS

Findings from this review indicate that short sleep duration, more sleep fragmentation, less sleep depth and increased variability in sleep timing may be associated with BP nondipping in healthy individuals.

CONCLUSION

While there is no evidence-based approach for the treatment of nocturnal BP nondipping, it seems promising that addressing one's sleep health may be an important starting point to reduce the prevalence of BP nondipping and perhaps the progression to cardiovascular disease.

Orexin, Sleep, Sympathetic Neural Activity, and Cardiovascular Function

Inadequate sleep duration and quality are associated with reduced cardiovascular health and increased mortality. Experimental evidence points to the sympathetic nervous system as a key mediator in the observed relationship between poor sleep and cardiovascular dysfunction. However, brain mechanisms underpinning the impaired sympathetic function associated with poor sleep remain unclear. Recent evidence suggests the central orexin system, particularly orexins A and B and their receptors, have a key regulatory role for sleep in animal and human models. While orexin system activity has been observed to significantly impact sympathetic regulation in animals, the extension of these findings to humans has been difficult due to an inability to directly assess orexin system activity in humans. However, direct measures of sympathetic activity in populations with narcolepsy and chronic insomnia, 2 sleep disorders associated with deficient and excessive orexin neural activity, have allowed indirect assessment of the relationships between orexin, sleep, and sympathetic regulation. Further, the recent pharmaceutical development of dual orexin receptor antagonists for use in clinical insomnia populations offers an unprecedented opportunity to examine the mechanistic role of orexin in sleep and cardiovascular health in humans. The current review assesses the role of orexin in both sleep and sympathetic regulation from a translational perspective, spanning animal and human studies. The review concludes with future research directions necessary to fully elucidate the mechanistic role for orexin in sleep and sympathetic regulation in humans.

The association between sleep deprivation and arterial pressure variations: a systematic literature review

Objectives

Arterial hypertension is a cardiovascular disease defined as a sustained high blood pressure, constituting an important risk factor for the development of heart diseases, such as coronary heart disease and heart failure. At the same time, pathophysiological pathways underlying sleeping deprivation provides biological plausibility for a causation connection between sleep deprivation and acute or chronic blood pressure elevation, such as the mechanism behind blood pressure dipping at night, which strongly relies on reduced sympathetic activity provided by sleep, besides empirical and clinical evidence suggesting that sleep disorders incidence is correlate with posterior development of arterial hypertension. The aim of this study was to systematically review published studies analyzing the possible relationship between sleep deprivation and variations in blood pressure during nighttime and daytime.

Methods

The research was carried out in the second semester of 2020 following the PRISMA model and using the LILACS, MEDLINE and COCHRANE (CENTRAL) databases. The keywords used were associated using the Boolean method. Only trials and studies in humans unrelated to sleep apnea were included, in an attempt to answer the question proposed. Duplications and articles outside the topic were excluded.

Results

After the selection processes, fourteen studies were left, which were classified, depending on the findings, in four categories: 1) blood pressure differences only in sleep deprivation's night; 2) blood pressure differences only in the following day after sleep deprivation's night; 3) blood pressure differences in both nights and 4) those that found no blood pressure differences.

Conclusion

It was found an increase in blood pressure on the night of sleep deprivation, suggesting a possible causality with an acute increase in blood pressure depending on the population studied. In general, sleep deprivation is acutely associated with blood pressure elevation or acute elevation of markers that suggest the role of compensatory mechanisms, such as increased natriuresis and increased parasympathetic activity.

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Sleep deprivation results in increased simpathetic activity.

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Chronic sleep deprivation might lead to systemic arterial hypertension.

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Increased parasympathetic activity in acute sleep deprivation play a role as compensatory mechanism.