Sleep Macrostructure Research Articles

Perioperative Pharmacological Sleep-Promotion and Pain Control: A Systematic Review.

Sleep macrostructure is commonly disturbed after surgery. Postoperative pain control remains challenging. Given the bidirectional interaction between sleep and pain, understanding the role of modulation of sleep during the perioperative period on postoperative pain is needed. This was a systematic review. Controlled trials examining the effects of perioperative sleep-promoting pharmacological agents on postoperative pain and analgesic consumption were identified through a systematic search strategy utilizing multiple electronic databases. Fourteen studies (9 melatonin, 5 zolpidem) involving 921 patients (melatonin n=586, zolpidem n=335) were included. Compared to placebo, melatonin reduced postoperative pain scoresby ≥30% and significantly decreased opioid consumption in 3 studies (postoperative day [POD] 1-2), whereas 4 studies reported no significant effect of melatonin on postoperative pain. Compared to placebo, zolpidem reduced postoperative pain scores during POD1-7/POD1-14 in 2 studies, but only 1 trial suggested clinically meaningful improvement (ie, relative reduction of pain score≥30%). Whereas 3 zolpidem trials showed no significant differences regarding postoperative pain ratings, zolpidem treatment was associated with decreased analgesic consumption in 4 out of 5 trials. Several limitations of the included studies were identified; only 1 study out of 14 was deemed to be at low risk of bias, and heterogeneity of the study design and outcome assessment precluded meta-analysis. Perioperative addition of a sleep-promoting pharmacological agent may improve pain control, but underlying evidence is weak and results are inconsistent. Only 5 of the 14 studies objectively evaluated changes in sleep (polysomnography, 2 zolpidem studies; actigraphy, 3 melatonin studies), which complicates conclusions regarding links between perioperative sleep and pain.

Obstructive sleep apnea may induce orexinergic system and cerebral β-amyloid metabolism dysregulation: is it a further proof for Alzheimer's disease risk?

BackgroundObstructive Sleep Apnea (OSA) is associated with pathological changes of cerebral β-amyloid dynamics. Orexin has been demonstrated interfering with β-amyloid metabolism in Alzheimer's Disease (AD) pathology. The present study investigated cerebrospinal-fluid (CSF) β-amyloid40 (Aβ40), β-amyloid42 (Aβ42) and orexin levels in OSA patients compared to AD patients and controls. MethodsOSA and AD patients were included in this study and compared to a group of controls. Patients and controls underwent lumbar puncture for the assessment of CSF Aβ40, Aβ42, tau proteins, orexin levels, and polysomnography to measure nocturnal sleep architecture. Results20 OSA patients, 20 AD patients, and 15 controls were included in our study. OSA patients showed higher CSF orexin levels than AD patients and controls, and AD patients showed higher CSF orexin levels than controls. Moreover, CSF Aβ40 and Aβ42 were lower in OSA patients than controls, but higher in OSA patients compared to AD patients. However, AD patients showed lower CSF Aβ42 levels but comparable CSF Aβ40 levels than controls. Sleep macrostructure was similarly altered in OSA and AD patients compared to controls. Finally, the apnea-hypopnea index (AHI) was related to the ratio Aβ42/Aβ40 and CSF orexin levels in OSA patients. ConclusionThis study proved the alteration of CSF orexin levels and β-amyloid isoforms 40 and 42 in OSA patients. We suppose that sleep disruption and intermittent hypoxia, the two core features of OSA, may induce orexinergic system and cerebral β-amyloid metabolism dysregulation. This evidence further supports the current hypothesis that OSA may possibly start AD neuropathological processes.

Analysis of Sleep Macrostructure in Patients Diagnosed with Parkinson's Disease.

Patients diagnosed with Parkinson’s disease present sleep disorders with a higher frequency than the general population. The sleep architecture in these patients shows variations with respect to the normal population, so in this work it was decided to investigate the characteristics of the macroarchitecture of sleep in patients diagnosed with Parkinson’s disease. A polysomnographic study was carried out on 77 patients diagnosed with Parkinson’s disease. All the studies were processed according to the AASM Manual for the Scoring of Sleep and Associated Events v.2.2, and to the criteria of the International Classification of Sleep Disorders 3rd ed. (2014). Processing was carried out using descriptive statistics, as well as non-parametric analysis for comparison between cases and controls. The group of patients showed significant reductions of the N2, N3, and REM sleep stages when compared with a control group, as well as a significant increase in intra-sleep wakefulness. The number of REM–NoREM sleep cycles and sleep efficiency showed marked reduction compared to the control group. There was a statistically significant difference in the macroarchitecture of sleep between patients diagnosed with Parkinson’s disease and healthy controls.

A Review of Approaches for Sleep Quality Analysis

Sleep quality is directly related to overall wellness and can reveal symptoms of several diseases. However, the term “sleep quality” still lacks a definitional consensus and is commonly assessed in sleep labs with polysomnography, comprising high costs, or through sleep questionnaires, a highly subjective technique. Multiple methods have been proposed to address the estimation of sleep quality, and devices were developed to conduct the examination in the subject’s home. The objective of this paper is to analyze the methods and the devices presented in the literature, assessing the development of objective markers that could lead to an improvement of the subjective sleep experience understanding, leading to developments in the treatment of sleep quality deficits. A systematic review was conducted, selecting research articles published from 2000 to 2018, and two research questions were formulated, specifically, “what methods for sleep quality assessment have been developed” and “what kind of measures are employed by the devices that have been developed to estimate sleep quality.” The research trend for the assessment of sleep quality is based on the sleep macrostructure, and it was verified that despite the convenience and considerable popularity among the consumers of home health monitoring of devices, such as actigraphs, the validity of these tools regarding the estimation of sleep quality still needs to be systematically examined. A detailed resume of the key findings and the identified challenges are presented, ascertaining the main gaps in the current state of the art.

Sleep efficiency and neurophysiological patterns in middle-aged men are associated with cognitive change over their adult life course.

Disrupted sleep is a contributing factor to cognitive ageing, while also being associated with neurodegenerative disorders. Little is known, however, about the relation of sleep and the gradual cognitive changes over the adult life course. Sleep electroencephalogram (EEG) patterns are potential markers of the cognitive progress. To test this hypothesis, we assessed sleep architecture and EEG of 167 men born in the Copenhagen Metropolitan Area in 1953, who, based on individual cognitive testing from early (~18years) to late adulthood (~58years), were divided into 85 subjects with negative and 82 with positive cognitive change over their adult life. Participants underwent standard polysomnography, including manual sleep scoring at age ~58years. Features of sleep macrostructure were combined with a number of EEG features to distinguish between the two groups. EEG rhythmicity was assessed by spectral power analysis in frontal, central and occipital sites. Functional connectivity was measured by inter-hemispheric EEG coherence. Group differences were assessed by analysis of covariance (p<0.05), including education and severity of depression as potential covariates. Subjects with cognitive decline exhibited lower sleep efficiency, reduced inter-hemispheric connectivity during rapid eye movement (REM) sleep, and slower EEG rhythms during stage 2 non-REM sleep. Individually, none of these tendencies remained significant after multiple test correction; however, by combining them in a machine learning approach, the groups were separated with 72% accuracy (75% sensitivity, 67% specificity). Ongoing medical screenings are required to confirm the potential of sleep efficiency and sleep EEG patterns as signs of individual cognitive progress.

Prevalence of Sleep Bruxism and Its Association with Obstructive Sleep Apnea in Adult Patients: A Retrospective Polysomnographic Investigation.

To determine the prevalence of sleep bruxism (SB) in adult obstructive sleep apnea (OSA) patients, to assess the association between SB and OSA in terms of sleep macrostructure and respiratory parameters, and to determine possible OSA risk factors for SB. Type I polysomnographic data of 147 adult OSA patients (mean age 44.6 ± 12.8 years) were evaluated for SB. SB episodes were scored when masseter rhythmic masticatory muscle activity (RMMA) was twice the background electromyography amplitude, and SB was established when patients had more than four SB episodes per hour of sleep. Demographic characteristics, sleep macrostructure, and respiratory parameters, including respiratory-related arousal index (RAI), spontaneous arousal index (SAI), oxygen desaturation index (ODI), and Apnea-Hypopnea Index (AHI), were analyzed for differences between patients with and without SB using independent samples t test and Mann-Whitney U test. Multivariate logistic regression analysis was performed to determine the odds of OSA risk factors for SB. Approximately one-third (33.3%) of the adult OSA patients had concomitant SB. Most of the RMMA observed in OSA-SB patients was phasic in nature. OSA patients with SB demonstrated significantly greater RAI (P = .001) and ODI (P = .005). RAI (odds ratio = 1.05, 95% confidence interval = 1.00 to 1.10) and SAI (odds ratio = 0.89, 95% confidence interval = 0.80 to 0.96) demonstrated marginal effects on the odds of experiencing SB. About one-third of adult OSA patients had SB, and these patients demonstrated significantly more respiratory-related arousals and oxygen desaturations. These findings suggest that a phenotypic subtype of OSA patients with predominantly phasic SB exists and allude to a possible protective role of RMMA in respiratory-related arousals.

Sleep, Circadian Rhythms, and Epilepsy.

There is a known interrelationship between sleep and epilepsy. This review highlights the recent findings regarding interactions between sleep and circadian rhythms and the manifestations of epilepsy and surgical treatments for refractory epilepsy. CLOCK gene expression may be reduced within the epileptogenic focus in patients with refractory epilepsy. Interictal epileptiform discharges during NREM and especially REM sleep may lateralize to the epileptogenic hemisphere. Intracranial video EEG monitoring and EEG from implanted responsive neurostimulator devices confirm scalp video EEG findings of a nocturnal peak for interictal epileptiform discharges. Successful epilepsy surgery may improve sleep macrostructure and quality. Sleep outcomes in people with epilepsy undergoing epilepsy surgery and neurostimulator implantation may provide innovative understandings into the associations between sleep and epilepsy. These associations may then provide novel therapeutic options targeting sleep and circadian pathways to improve seizure control and improve the quality of life for patients with this debilitating disorder.

Home Polysomnography Reveals a First-Night Effect in Patients With Low Sleep Bruxism Activity.

To examine the presence of a first-night effect (FNE) and the level of internight variability in sleep bruxism (SB) activity when a self-applicable electrode set is used in home polysomnography (PSG) in a sample of subjects with possible SB. Fourteen females and two males aged 38.3 ± 9.1 years (mean ± standard deviation) with self-reported SB underwent home-PSG on three consecutive nights. The subjects applied PSG sensors themselves, including self-applicable electrode sets used to record sleep and masseter muscle activity. Repeated-measures analysis of variance was used to compare SB and sleep variables between the nights. Surprisingly, there were statistically significant elevations in the rhythmic masticatory muscle activity (RMMA) episode index (P = .009), burst index (P = .016), and bruxism time index (P = .049) throughout the course of 3 nights. More bruxers were diagnosed on the second (6 bruxers, ≥ 2 episodes/h) and third night (7 bruxers) compared to the first night (2 bruxers). Most subjects (14/16) had their highest RMMA index on the second or third night. The mean coefficient of variation for RMMA episode index was 50.7%. No statistically significant differences were detected in other sleep variables. The results indicate that a FNE may be present in SB activity, possibly lasting several nights in some subjects. Furthermore, FNE appears to be combined with high internight variability of SB activity without indications of internight changes in sleep macrostructure. To confirm the level of ongoing SB activity, several nights of PSG may be required, especially in subjects with low first-night SB activity. A commentary on this article appears in this issue on page 1281.

Effects of night-time on-call work on heart rate variability before bed and sleep quality in visiting nurses.

In Japan, many visiting nurses work carrying cell phones to respond to calls from users even at night (on-call work). The purpose of this study was to investigate whether on-call work affected heart rate variability (HRV) before bed and decreased sleep quality in visiting nurses even if their sleep was not interrupted due to actual calls. Thirty-one visiting nurses (mean age, 49.8 years; standard deviation, 6.3years) were asked to record their 2.5-min resting HRV before bed, and to undergo one-channel sleep electroencephalography (EEG) and subjective sleep evaluations upon waking (Oguri, Shirakawa, and Azumi Sleep Inventory) at home for 4-5 consecutive days, including both on-call and non-on-call days. Paired data sets of outcome measures, including HRV parameters, sleep macrostructure variables, and subjective sleep quality scores between on-call and non-on-call days were compared; the most recent measurements for each category were used for each subject. There were no differences in HRV measures and objective sleep EEG variables. A significant increase in "sleepiness on rising" and a decrease in "feeling refreshed" were observed on on-call days (P = 0.019 and 0.021, respectively), and younger subjects (≤ 51years old) demonstrated a significant reduction in "sleepiness on rising" (significant interaction effect, P = 0.029). Adverse effects of on-call work on sleep quality in most visiting nurses are thought to be subjective, and relatively young nurses tend to notice a decrease in sleep quality. On-call work itself does not appear to be a substantial stressor that could affect HRV and sleep structure.

Differences in pre-sleep activity and sleep location are associated with variability in daytime/nighttime sleep electrophysiology in the domestic dog

The domestic dog (Canis familiaris) is a promising animal model. Yet, the canine neuroscience literature is predominantly comprised of studies wherein (semi-)invasive methods and intensive training are used to study awake dog behavior. Given prior findings with humans and/or dogs, our goal was to assess, in 16 family dogs (1.5–7 years old; 10 males; 10 different breeds) the effects of pre-sleep activity and timing and location of sleep on sleep electrophysiology. All three factors had a main and/or interactive effect on sleep macrostructure. Following an active day, dogs slept more, were more likely to have an earlier drowsiness and NREM, and spent less time in drowsiness and more time in NREM and REM. Activity also had location- and time of day-specific effects. Time of day had main effects; at nighttime, dogs slept more and spent less time in drowsiness and awake after first drowsiness, and more time in NREM and in REM. Location had a main effect; when not at home, REM sleep following a first NREM was less likely. Findings are consistent with and extend prior human and dog data and have implications for the dog as an animal model and for informing future comparative research on sleep.

Disruption of sleep-wake continuum in myotonic dystrophy type 1: Beyond conventional sleep staging

Sleep disruption and excessive daytime sleepiness are well recognised symptoms in myotonic dystrophy type 1 (DM1), where a central dysfunction of sleep-wake regulation may play a pivotal role. Few studies evaluated sleep macrostructure in DM1, but none investigated more refined sleep variables. Eight DM1 patients (6 male, aged 20-50 years) and 10 healthy controls (7 male, aged 22-67 years) underwent nocturnal polysomnography and multiple sleep latency test. Sleep stages and events were scored according to standard criteria; sleep microstructure was analyzed through cyclic alternating pattern. Relative and absolute delta powers were computed for whole non REM and each non REM period. DM1 patients showed increased REM sleep and decreased N2. N3, although not significantly, was increased. Three patients, but no controls, had sleep-onset REM period in nocturnal sleep. DM1 patients showed slower delta power dissipation across the night, and increased sleep instability (CAP rate). Multiple sleep latency tests showed shorter sleep latencies, five patients presenting at least one sleep-onset REM period and, when including also night sleep, two sleep-onset REM periods. Our data confirm a narcoleptic-like phenotype in DM1 with a prominent REM sleep dysregulation, that may account for daytime sleepiness, together with increased sleep instability and impaired delta power dissipation that seem peculiar of the disease.

Maturation of integrative sleep apparatus in children in normal and pathological condition

To study and compare clinical characteristics of sleep macrostructure and sleep cycle organization during the night polysomnographic study in children with attention deficit hyperactivity disorder (ADHD) and obstructive sleep apnea syndrome (OSAS) aged from 6 to 9 years. Polysomnography was performed in 40 children with ADHD and 20 children with OSAS. The control group included 20 healthy children. The changes in sleep architectonics were unidirectional. Typical for the two groups of children was an increase in the latency of REM sleep and a reduction of its duration in total time of sleep. In children with ADHD, there was a significant decrease in the total number of sleep cycles, with a significant increase in the duration of the first sleep cycle. For an objective assessment of the rhythmic organization of ultradian rhythms, the authors propose a formula to calculate the maturity index of sleep in children older than 6 years. From the standpoint of evolutionary neuroscience, results should be considered as manifestations of dysontogenesis.

Bedtime to morning variation of mobility after nocturnal sleep in Parkinson's disease

Up to 50% of the patients with Parkinson´s disease experience a transient but clinically relevant improvement in mobility on morning awakening, even before taking their habitual antiparkinsonian medications. This phenomenon has been described as Sleep Benefit” (SB). We aimed to evaluate the effect of nocturnal sleep on mobility on morning awakening, compared to the effect of habitual morning dopaminergic medications. Moreover, we explored if this effect varied differently among patients experiencing or not SB and if it was influenced by overall quality of nocturnal sleep macrostructure.

Evolution of macrosleep in the acute and subacute phase after stroke

Introduction: A restorative sleep is essential for physical and psychological health. Even though literature is highly heterogeneous, stroke patients mostly tend to have a lower sleep efficiency, reduced N2, N3 and REM sleep, and generally a more fragmented sleep, especially in the acute phase. Crucially, there might be an association between an impaired sleep architecture and impaired cognitive outcome. As such, a poor sleep efficiency, a low amount of N2 and N3 and enhanced wakefulness after sleep onset have been linked to an acute impaired outcome. However, the specific role of macrosleep variations for the long-term recovery is still unknown. Therefore, we aim at observing the evolution of sleep macrostructure at several time points after stroke and relating them to the long-term clinical outcome. We will further apply transitional sleep scoring which might allow a more profound insight into sleep stability. Materials and methods: We have measured so far 8 adult stroke patients (6 m, 2f; age±SEM 50.7±4.0 years; range: 27–60; 5 hemispheric, 2 bithalamic, 1 cerebellar) in the acute (day range: 3–17) and 4 of those patients in the subacute phase (day range: 72–120). We applied high-density EEG during a full night of sleep, and investigated the cognitive outcome by neuropsychological examination. We relate our data also to 2 healthy not-yet age-matched controls (31±2.1 years), having spent one night at the hospital. The transitional sleep scoring method classifies the sleep recording epoch- and time-independently, thereby allowing for a detailed and continuous scoring of sleep stages and transitions throughout the night. Results: Our very preliminary analysis shows that in the acute phase, stroke patients, as compared to controls, descriptively tend to sleep less (values expressed as means±SEM; 64.3%3.9 vs. 75.3%±6.5), to be more awake (35.7%±3.9 vs. 24.7%±6.5), to have less N3 (10.6%±1.8 vs. 23.4%±0.5) and presumably less REM sleep (12.1%±2.2 vs. 16.6%±3.8). Patients might exhibit more sleep transitions than controls (211.6±20.7 vs. 157±38.2). In the subacute phase, patients sleep shows non-significant improvements (70.2%±35.1 sleep efficiency, 19.1%±9.5 of N3, 13.9%±6.9 of REM sleep). The classical sleep scoring captured less transitions (211.6±20.7) as compared to the transitional scoring (338.4±42.4) in the acute phase, while the percentage of sleep stayed almost similar (64.3%3.9 vs. 69.8%±3.6). Conclusions: In line with current literature, our preliminary results seem to support the evidence that stroke patients may display variations in macrosleep, especially in the acute phase, having a lower sleep efficiency, less N3 and less REM sleep. Our data also show that all-night high-density EEG recordings are feasible in this hospital setting. Furthermore, transitional scoring may provide a more profound insight into sleep stability. Acknowledgements: This study was funded by the SNF Sinergia Grant (Project number: 160803).

Detection of the Sleep Stages Throughout Non-Obtrusive Measures of Inter-Beat Fluctuations and Motion: Night and Day Sleep of Female Shift Workers

Automatic sleep staging based on inter-beat fluctuations and motion signals recorded through a pressure bed sensor during sleep is presented. The analysis of the sleep was based on the three major divisions of the sleep time: Wake, non-rapid eye movement (nREM) and rapid eye movement (REM) sleep stages. Twelve sleep recordings, from six females working alternate shift, with their respective annotations were used in the study. Six recordings were acquired during the night and six during the day after a night shift. A Time-Variant Autoregressive Model was used to extract features from inter-beat fluctuations which later were fed to a Support Vector Machine classifier. Accuracy, Kappa index, and percentage in wake, REM and nREM were used as performance measures. Comparison between the automatic sleep staging detection and the standard clinical annotations, shows mean values of [Formula: see text]% for accuracy [Formula: see text] for kappa index, and mean errors of 5% for sleep stages. The performance measures were similar for night and day sleep recordings. In this sample of recordings, the results suggest that inter-beat fluctuations and motions acquired in non-obtrusive way carried valuable information related to the sleep macrostructure and could be used to support to the experts in extensive evaluation and monitoring of sleep.

Sleep macrostructure is modulated by positive and negative social experience in adult pet dogs.

The effects of emotionally valenced events on sleep physiology are well studied in humans and laboratory rodents. However, little is known about these effects in other species, despite the fact that several sleep characteristics differ across species and thus limit the generalizability of such findings. Here we studied the effect of positive and negative social experiences on sleep macrostructure in dogs, a species proven to be a good model of human social cognition. A non-invasive polysomnography method was used to collect data from pet dogs (n = 16) participating in 3-hour-long sleep occasions. Before sleep, dogs were exposed to emotionally positive or negative social interactions (PSI or NSI) in a within-subject design. PSI consisted of petting and ball play, while NSI was a mixture of separation, threatening approach and still face test. Sleep macrostructure was markedly different between pre-treatment conditions, with a shorter sleep latency after NSI and a redistribution of the time spent in the different sleep stages. Dogs' behaviour during pre-treatments was related to the macrostructural difference between the two occasions, and was further modulated by individual variability in personality. This result provides the first direct evidence that emotional stimuli affect subsequent sleep physiology in dogs.

P 110 Manual sleep staging and coupling analysis in combined EEG and MEG sleep recordings

The study of sleep disorders is best done in a clinical sleep laboratory by polysomnography (PSG), which allows to record all physiological signals necessary to determine sleep macrostructure (sleep stages), sleep microstructure (arousal), as well as related behavior of cardio-respiratory parameters. PSG was extended by 125-channel-magnetoencephalography (MEG) running at the same time. A MEG laboratory consists of a magnetically shielded room (MSR) as MEG requires very low ambient magnetic fields in the range of pT and subjects slept for 3–4 h starting around midnight in the MEG laboratory. The PSG recordings were first analyzed manually to identify sleep stages. In a second step, common spectral properties of EEG and MEG were investigated using measures such as the time-frequency evolution across the scalp. Manual sleep staging served as input to the spectral analysis. Results show both combined and independent patterns in EEG and MEG demonstrating the potential of combined recordings in researching local brain activity during sleep.

Cyclic alternating pattern and interictal epileptiform discharges during morning sleep after sleep deprivation in temporal lobe epilepsy.

Sleep deprivation (SD) increases the occurrence of interictal epileptiform discharges (IED) compared to basal EEG in temporal lobe epilepsy (TLE). In adults, EEG after SD is usually performed in the morning after SD. We aimed to evaluate whether morning sleep after SD bears additional IED-inducing effects compared with nocturnal physiological sleep, and whether changes in sleep stability (described by the cyclic alternating pattern-CAP) play a significant role. Adult patients with TLE underwent in-lab night polysomnography (n-PSG) and, within 7days from n-PSG, they underwent also a morning EEG after night SD (SD-EEG). We included only TLE patients in which both recordings showed IED. SD-EEG consisted of waking up patients at 2:00 AM and performing video EEG at 8:00 AM. For both recordings, we obtained the following markers for the first sleep cycle: IED/h (Spike Index, SI), sleep macrostructure, microstructure (NREM CAP rate; A1, A2 and A3 Indices), and SI association with CAP variables. The macrostructure of the first sleep cycle was similar in n-PSG and morning SD-EEG, whereas CAP rate and SI were significantly higher in SD-EEG. SI increase was selectively associated with CAP phases. SD increases the instability of morning recovery sleep compared with n-PSG, and particularly enhances CAP A1 phases, which are associated with the majority of IED. Thus, higher instability of morning recovery sleep may account at least in part for the increased IED yield in SD-EEG in TLE patients.

Bed Rest and Hypoxic Exposure Affect Sleep Architecture and Breathing Stability.

Objective: Despite over 50 years of research on the physiological effects of sustained bed rest, data characterizing its effects on sleep macrostructure and breathing stability in humans are scarce. This study was conducted to determine the effects of continuous exposure to hypoxia and sustained best rest, both individually and combined, on nocturnal sleep and breathing stability.Methods: Eleven participants completed three randomized, counter-balanced, 21-days trials of: (1) normoxic bed rest (NBR, PIO2 = 133.1 ± 0.3), (2) hypoxic ambulatory confinement (HAMB, PIO2 = 90.0 ± 0.4) and (3) hypoxic bed rest (HBR, PIO2 = 90.0 ± 0.4; ~4,000 m equivalent altitude). Full objective polysomnography was performed at baseline, on Night 1 and Night 21 in each condition.Results: In NBR Night 1, more time was spent in light sleep (10 ± 2%) compared to baseline (8 ± 2%; p = 0.028); Slow-wave sleep (SWS) was reduced from baseline in the hypoxic-only trial by 18% (HAMB Night 21, p = 0.028) and further reduced by 33% (HBR Night 1, p = 0.010), and 36% (HBR Night 21, p = 0.008) when combined with bed rest. The apnea-hypopnea index doubled from Night 1 to Night 21 in HBR (32–62 events·h−1) and HAMB (31–59 events·h−1; p = 0.002). Those who experienced greatest breathing instability from Night 1 to Night 21 (NBR) were correlated to unchanged or higher (+1%) night SpO2 concentrations (R2 = 0.471, p = 0.020).Conclusion: Bed rest negatively affects sleep macrostructure, increases the apnea-hypopnea index, and worsens breathing stability, each independently exacerbated by continuous exposure to hypoxia.

Association of symptoms of insomnia and sleep parameters among kidney transplant recipients

ObjectiveInsomnia complaints are frequent among kidney transplant (kTx) recipients and are associated with fatigue, depression, lower quality of life and increased morbidity. However, it is not known if subjective insomnia symptoms are associated with objective parameters of sleep architecture. Thus, we analyze the association between sleep macrostructure and EEG activity versus insomnia symptoms among kTx recipients. MethodsParticipants (n1=100) were selected from prevalent adult transplant recipients (n0=1214) followed at a single institution. Insomnia symptoms were assessed by the Athens Insomnia Scale (AIS) and standard overnight polysomnography was performed. In a subgroup of patients (n2=56) sleep microstructure was also analyzed with power spectral analysis. ResultsIn univariable analysis AIS score was not associated with sleep macrostructure parameters (sleep latency, total sleep time, slow wave sleep, wake after sleep onset), nor with NREM and REM beta or delta activity in sleep microstructure. In multivariable analysis after controlling for covariables AIS score was independently associated with the proportion of slow wave sleep (β=0.263; CI: 0.026–0.500) and REM beta activity (β=0.323; CI=0.041–0.606) (p<0.05 for both associations). ConclusionsAmong kTx recipients the severity of insomnia symptoms is independently associated with higher proportion of slow wave sleep and increased beta activity during REM sleep but not with other parameters sleep architecture. The results suggest a potential compensatory sleep protective mechanism and a sign of REM sleep instability associated with insomnia symptoms among this population.