Effects of NREM sleep instability on cognitive processing

Sleep and Epilepsy

The relationship between sleep and epilepsy is both intimate and bidirectional. The molecular mechanisms which control circadian rhythm and the sleep/wake cycle are dysregulated in epileptogenic tissue and are themselves effected by molecular pathways for epilepsy. Sleep affects the frequency of interictal epileptiform discharges and recent research has raised new questions regarding the impact of discharges on sleep function and cognition. Epileptiform discharges themselves affect sleep architecture and increase the risk of sleep disorders. Several sleep-related epilepsy syndromes have undergone changes in their classification which highlights their intimate relationship to sleep and novel screening tools have been developed to help clinicians better differentiate epileptic seizures from sleep-related paroxysmal events. Improving sleep and addressing sleep disorders has been associated with improved seizure control and increased well-being in people with epilepsy. These interactions are discussed in detail in this review.

Sleep electroencephalography biomarkers of cognition in obstructive sleep apnea

Obstructive sleep apnea has been associated with cognitive impairment and may be linked to disorders of cognitive function. These associations may be a result of intermittent hypoxaemia, sleep fragmentation and changes in sleep microstructure in obstructive sleep apnea. Current clinical metrics of obstructive sleep apnea, such as the apnea-hypopnea index, are poor predictors of cognitive outcomes in obstructive sleep apnea. Sleep microstructure features, which can be identified on sleep electroencephalography of traditional overnight polysomnography, are increasingly being characterized in obstructive sleep apnea and may better predict cognitive outcomes. Here, we summarize the literature on several major sleep electroencephalography features (slow-wave activity, sleep spindles, K-complexes, cyclic alternating patterns, rapid eye movement sleep quantitative electroencephalography, odds ratio product) identified in obstructive sleep apnea. We will review the associations between these sleep electroencephalography features and cognition in obstructive sleep apnea, and examine how treatment of obstructive sleep apnea affects these associations. Lastly, evolving technologies in sleep electroencephalography analyses will also be discussed (e.g. high-density electroencephalography, machine learning) as potential predictors of cognitive function in obstructive sleep apnea.

Sleep Structure in Untreated Adults With ADHD: A Retrospective Study

OBJECTIVE

Polysomnographic findings in neurodevelopmental disorders have been reported, but previous studies have had several limitations. The purpose of this study was to characterize sleep structure in untreated adults diagnosed with ADHD, excluding ADHD-related sleep disorders as determined by polysomnography and multiple sleep latency testing.

METHODS

This study included 55 patients aged 18 years or older who visited the Kurume University Hospital Sleep Clinic between April 2015 and March 2020. The diagnosis of ADHD was determined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (ADHD group, n = 28; non-ADHD, n = 27).

RESULTS

The ADHD group had significantly longer slow wave sleep (SWS) duration than the non-ADHD group (ADHD: 68.3 ± 31.0 minutes vs. non-ADHD: 43.4 ± 36.6 minutes; p = .0127).

CONCLUSIONS

The increased SWS volume observed in drug-naïve adult patients with ADHD may be related to the pathogenesis of this disorder.

Neuropsychological and Behavioral Profile in Sleep-Related Hypermotor Epilepsy (SHE) and Disorders of Arousal (DOA): A Multimodal Analysis

STUDY OBJECTIVES

Disorder of arousal (DOA) and sleep-related hypermotor epilepsy (SHE) are complex, often bizarre, involuntary sleep behaviors, whose differential diagnosis may be challenging because they share some clinical features, such as sleep fragmentation. Mounting evidence highlights the critical role of sleep in cognitive functions. Controversial findings are raised about the cognitive profile in SHE; however, no studies have investigated the cognitive profile in DOA. This study aimed to assess whether sleep instability affects cognitive functions in patients with SHE or DOA.

METHODS

This study analyzed 11 patients with DOA, 11 patients with SHE, and 22 healthy controls (HC). They underwent full-night video polysomnography (vPSG) and comprehensive neuropsychological and behavioral evaluation. Differences in the variables of interest among the SHE group, DOA group, and their respective control groups were evaluated. The auto-contractive map (auto-CM) system was used to evaluate the strength of association across the collected data.

RESULTS

The SHE group had reduced sleep efficiency and increased wake after sleep onset (WASO); both the SHE and DOA groups showed increased % of N2 and REM sleep compared to the HC group. Neuropsychological and behavioral evaluations showed a different cognitive profile in the SHE group with respect to the HC group. The auto-CM showed that Pittsburgh Sleep Quality Index (PSQI), Beck depression inventory (BDI), MWCST_PE, Epworth sleepiness scale (ESS), WASO, N1, and % REM were strictly correlated with SHE, whereas the SE and arousal index (AI) were strictly related to DOA.

CONCLUSIONS

Patients with SHE and DOA present different cognitive and psychiatric profiles, with subtle and selective cognitive impairments only in those with SHE, supporting the discriminative power of cognitive and psychiatric assessment in these two conditions.

Effects of CPAP Treatment on Electroencephalographic Activity in Patients with Obstructive Sleep Apnea Syndrome During Deep Sleep with Consideration of Cyclic Alternating Pattern

Objective

To investigate whether continuous positive airway pressure (CPAP) treatment would change EEG activities associated with cyclic alternating pattern (CAP subtype A1, A2, and A3) and non-CAP (NCAP) during non-rapid eye movement sleep stage 3 (N3) in patients with obstructive sleep apnea (OSA).

Methods

The effects of CPAP treatment on the percentages of sleep stage N3 occupied by the CAP and NCAP, power of EEG waves in the CAP and NCAP were examined in 18 patients with moderate-to-severe OSA undergoing polysomnographic recordings.

Results

Apnea and hypopnea index during sleep stage N3 was positively correlated with ratios of phases A2 and A3 duration to total phase A duration [Phase (A2+A3) /Phase A] and negatively correlated with phase A1/phase A. With CPAP treatment, percentages of sleep stage N3 occupied by total CAPs and subtypes A2 and A3, as well as CAP A2 and CAP A3 indexes were significantly decreased while percentages of sleep stage N3 occupied by NCAP (NCAP/N3) and CAP A1 index were significantly increased. In addition, CPAP treatment significantly decreased percentage of respiratory events associated CAPs and increased percentage of non-respiratory related CAPs. Moreover, absolute and relative delta power was significantly increased during phase A1, unchanged during phase A2 and phase B2, and significantly decreased during phases B1, A3 and B3. The absolute power of faster frequency EEG waves in CAPs showed a general trend of decrease. The absolute and relative power of delta waves with amplitudes ≥75 μV, but not <75 μV, was significantly increased.

Conclusion

CPAP treatment improves the sleep quality in OSA patients mainly by increasing delta power and decreasing power of higher frequency waves during phase A1, and decreasing CAP A2 and A3 indexes as well as increasing NCAP/N3 and power of delta waves with amplitudes ≥75 μV during NCAP.

Infectious Causes of Neoplasia in the Domestic Cat

In recent years, growing attention has been paid to the influence/role of infectious diseases in tumour development and progression. Investigations have demonstrated that some infectious organisms can have a direct role in the development of neoplasia, whereas others can predispose to neoplasia by alterations in the immune response, or by creating a pro-inflammatory environment. Feline leukaemia virus was one of the first infectious agents recognised as an oncogenic organism, and along with feline immunodeficiency virus has received the most attention. Since the discovery of this retrovirus, several other organisms have been associated with neoplastic processes in cats, these include gammaherpes virus, mouse mammary tumour virus, papillomaviruses, hepadnavirus, Helicobacter species, and the parasitic infections Platynosomum fastosum and Opisthorchis viverrini. This review summarises the findings to date.

Neuropsychological Profile in Pediatric Migraine without Aura: A Pilot Study

Despite the high prevalence of headache in developmental age, current reports about its neuropsychological effects are still lacking. The aim of the present pilot study is to assess the neuropsychological skills among children affected by migraine without aura (MwoA). Fifteen children (7M/8F) (mean age 10.73 ± 2.13) with MwoA, consecutively referred to the Center for Childhood Headache at Università degli Studi della Campania “Luigi Vanvitelli”, underwent the Italian version of the NEPSY-2 after cognitive evaluation. Moreover, to assess the pain level and disability grade during daily activity, the VAS and PedMIDAS scales were used. MwoA children were comparable with the control group of 38 children with respect to age, gender, language, and education level. Written informed consent was obtained from all parents and from children directly, when appropriate. MwoA children differed from controls significantly among the NEPSY-2 subscales, with a relevant relationship between the frequency and intensity of the attacks. In conclusion, the results of the present pilot study may suggest that MwoA could impact significantly neuropsychological functioning in children.

A systematic review and meta-analysis of the cyclic alternating pattern across the lifespan

BACKGROUND

Cyclic alternating pattern (CAP) is the electroencephalogram (EEG) pattern described as a marker of sleep instability and assessed by NREM transient episodes in sleep EEG. It has been associated with brain maturation. The aim of this review was to evaluate the normative data of CAP parameters according to the aging process in healthy subjects through a systematic review and meta-analysis.

METHODS

Two authors independently searched databases using PRISMA guidelines. Discrepancies were reconciled by a third reviewer. Subgroup analysis and tests for heterogeneity were conducted.

RESULTS

Of 286 studies, 10 submitted a total of 168 healthy individuals to CAP analysis. Scoring of CAP can begin at 3 months of life, when K-complexes, delta bursts, or spindles can be recognized. Rate of CAP increased with age, mainly during the first 2 years of life, then decreased in adolescence, and increased in the elderly. The A1 CAP subtype and CAP rate were high in school-aged children during slow-wave sleep (SWS). A1 CAP subtypes were significantly more numerous in adolescents compared with other groups, while the elderly showed the highest amounts of A2 and A3 CAP subtypes. Our meta-analysis registered the lowest CAP rate in infants younger than 2 years old and the highest in the elderly.

CONCLUSIONS

This review summarized the normative data of CAP in NREM sleep during the aging process. The CAP rate increased with age and sleep depth, especially during SWS. Parameters of CAP may reflect gender hormonal effects and neuroplasticity. More reports on CAP subtypes are needed for their reference values establishment.

Sleep spindles in children with restless sleep disorder, restless legs syndrome and normal controls

OBJECTIVE

To analyze and identify differences in sleep spindles in children with restless sleep disorder (RSD), restless legs syndrome (RLS) and normal controls.

METHODS

PSG (polysomnography) from children with RSD, RLS and normal controls were analyzed. Sleep spindle activity was detected on one frontal and one central electrode, for each epoch of N2 and N3 sleep. Sleep spindle density, duration and intensity (density × duration) were then obtained and used for analysis.

RESULTS

Thirty-eight children with RSD, twenty-three children with RLS and twenty-nine controls were included. The duration of frontal spindles in sleep stage N2 was longer in children with RSD than in controls. Frontal spindle density and intensity tended to be increased in RSD children. No significant differences were found for central spindles.

CONCLUSION

Children with RSD had longer frontal spindles. This finding may contribute to explain the occurrence of excessive movement activity during sleep and the presence of daytime symptoms.

SIGNIFICANCE

Recent research has demonstrated that children with RSD have increased NREM instability and sympathetic activation during sleep. Analyzing sleep spindles in children with RSD in comparison with children with RLS and controls adds to our understanding of the pathophysiology or RSD and its effects on daytime impairment.

Characteristics of Sleep Structure Assessed by Objective Measurements in Patients With Amnestic Mild Cognitive Impairment: A Meta-Analysis

Objectives: This study aims to explore the differences of sleep structure between patients with amnestic mild cognitive impairment (aMCI) and elderly people with normal cognition, which will help to provide evidence for the relationship between sleep disturbances and cognitive impairment.

Methods: A systematic review and meta-analysis were conducted on the literature on sleep parameters obtained by polysomnography or actigraphy in patients with aMCI. The PubMed and EMBASE databases were searched up to April 2020. Inclusion and exclusion criteria were established according to evidence-based medicine methods, and data of all eligible studies were meta-analyzed using the Review Manager 5.3 software.

Results: Among the 1,171 literature articles on sleep structure of patients with MCI, eight case-control studies met the inclusion criteria and were included in this meta-analysis. A total of 278 subjects were included, of which 103 were patients with aMCI and 175 were elderly people with normal cognition. The results showed that sleep efficiency (SE) and slow wave sleep (SWS) of patients with aMCI were significantly lower than those of healthy elderly people. Compared with the control group, the percentage of stage 1 of non-rapid eye movement (N1%) in the aMCI patients group increased, and the percentage of stage 2 of non-rapid eye movement (N2%) decreased.

Conclusions: Patients with aMCI may experience more severe sleep disturbances than normal cognitive elderly people. There were specific changes, especially in SE and SWS, in the sleep structure of patients with aMCI when compared to those with normal cognition.

Sleep continuity, stability and organization in good and bad sleepers

The relationship between objective and subjective sleep quality is still debated. Here, we investigate differences in objective sleep parameters in habitual subjective good sleepers and bad sleepers with the aim of evaluating sleep continuity, stability and organization as possible determinants of subjective sleep quality. In total, 38 subjects (good sleepers, N = 18; bad sleepers, N = 20) underwent two nights of sleep recording. Traditional sleep parameters displayed no between-groups differences. Conversely, bad sleepers showed lower sleep continuity (awakenings frequency), stability (e.g. arousals and state transitions frequency) and organization (e.g. number of sleep cycles and time spent in cycles). Our findings point to the involvement of these measures in determining habitual sleep quality perception and suggest the possibility to include them in standard sleep assessments.

Associations Between the Apnea-Hypopnea Index During REM and NREM Sleep and Cognitive Functioning in a Cohort of Middle-Aged Adults

STUDY OBJECTIVES

Prior research has linked obstructive sleep apnea (OSA) to varied cognitive deficits. Additionally, OSA in rapid eye movement (REM) versus non-rapid eye movement (NREM) sleep has been shown to be a stronger predictor of outcomes such as hypertension. The present study aimed to investigate whether OSA-as characterized by the apnea-hypopnea index (AHI)-during REM and NREM sleep is associated with performance on a range of cognitive tasks. We also investigated whether the presence/absence of the apolipoprotein E4 allele (APOE4) modifies the associations between AHI during REM and NREM sleep and cognitive performance.

METHODS

A cross-sectional sample of 1,250 observations from 755 community-dwelling adults (mean [standard deviation] age, 62.3 [8.2] years) participating in the Wisconsin Sleep Cohort study was carried out by means of overnight polysomnography, paper-and-pencil cognitive tasks, and genetic data. Linear mixed effects models with repeated measures estimated associations of AHI during REM and NREM sleep with cognitive outcomes, stratified by APOE4 status (carrier versus noncarrier).

RESULTS

No significant associations were found between REM AHI and cognitive outcomes for either APOE4 carriers and non-carriers. Higher NREM AHI was associated with worse memory retention among APOE4 carriers; among noncarriers of APOE4, higher NREM AHI was associated with worse performance on a test of psychomotor speed, but better performance on two tests of executive function.

CONCLUSIONS

Sleep state-specific (REM, NREM) OSA may be differentially associated with varying dimensions of cognitive deficits in middle-aged to older adults, and such associations are likely to be modified by genetic factors, include APOE polymorphisms.

Increased cortical involvement and synchronization during CAP A1 slow waves

Slow waves recorded with EEG in NREM sleep are indicative of the strength and spatial extent of synchronized firing in neuronal assemblies of the cerebral cortex. Slow waves often appear in the A1 part of the cyclic alternating patterns (CAP), which correlate with a number of behavioral and biological parameters, but their physiological significance is not adequately known. We automatically detected slow waves from the scalp recordings of 37 healthy patients, visually identified CAP A1 events and compared slow waves during CAP A1 with those during NCAP. For each slow wave, we computed the amplitude, slopes, frequency, synchronization (synchronization likelihood) between specific cortical areas, as well as the location of origin and scalp propagation of individual waves. CAP A1 slow waves were characterized by greater spatial extent and amplitude, steeper slopes and greater cortical synchronization, but a similar prominence in frontal areas and similar propagation patterns to other areas on the scalp. Our results indicate that CAP A1 represents a period of highly synchronous neuronal firing over large areas of the cortical mantle. This feature may contribute to the role CAP A1 plays in both normal synaptic homeostasis and in the generation of epileptiform phenomena in epileptic patients.

Sleep Health Promotion: Practical Information for Physical Therapists

Sleep disturbances occur in one third of the US population, and the Centers for Disease Control and Prevention's National Center for Injury Prevention and Control has deemed insufficient sleep to be a public health problem. Knowledge about sleep and skills to screen sleep disorders and to promote sleep health have been recommended for physical therapists. Furthermore, in survey studies, physical therapists overwhelmingly agree that sleep is important for health and poor sleep impairs function. Sleep is critical for the proper functioning of the body, including immune function, tissue healing, pain modulation, cardiovascular health, cognitive function, and learning and memory. Sleep disruptions occur across the life span and in individuals with various conditions that are typically treated by physical therapists. Therefore, the purpose of this perspective paper is to (1) discuss the relevance of sleep to physical therapist practice, (2) recommend tools to screen for the 3 most common sleep disorders, and (3) provide suggestions for how therapists can integrate sleep health in prevention, health promotion, and wellness interventions.

The relationship between sleep-wake cycle and cognitive functioning in young people with affective disorders

Although early-stage affective disorders are associated with both cognitive dysfunction and sleep-wake disruptions, relationships between these factors have not been specifically examined in young adults. Sleep and circadian rhythm disturbances in those with affective disorders are considerably heterogeneous, and may not relate to cognitive dysfunction in a simple linear fashion. This study aimed to characterise profiles of sleep and circadian disturbance in young people with affective disorders and examine associations between these profiles and cognitive performance. Actigraphy monitoring was completed in 152 young people (16–30 years; 66% female) with primary diagnoses of affective disorders, and 69 healthy controls (18–30 years; 57% female). Patients also underwent detailed neuropsychological assessment. Actigraphy data were processed to estimate both sleep and circadian parameters. Overall neuropsychological performance in patients was poor on tasks relating to mental flexibility and visual memory. Two hierarchical cluster analyses identified three distinct patient groups based on sleep variables and three based on circadian variables. Sleep clusters included a ‘long sleep’ cluster, a ‘disrupted sleep’ cluster, and a ‘delayed and disrupted sleep’ cluster. Circadian clusters included a ‘strong circadian’ cluster, a ‘weak circadian’ cluster, and a ‘delayed circadian’ cluster. Medication use differed between clusters. The ‘long sleep’ cluster displayed significantly worse visual memory performance compared to the ‘disrupted sleep’ cluster. No other cognitive functions differed between clusters. These results highlight the heterogeneity of sleep and circadian profiles in young people with affective disorders, and provide preliminary evidence in support of a relationship between sleep and visual memory, which may be mediated by use of antipsychotic medication. These findings have implications for the personalisation of treatments and improvement of functioning in young adults early in the course of affective illness.

Maladaptive autonomic regulation in PTSD accelerates physiological aging

A core manifestation of post-traumatic stress disorder (PTSD) is a disconnection between physiological state and psychological or behavioral processes necessary to adequately respond to environmental demands. Patients with PTSD experience abnormal oscillations in autonomic states supporting either fight and flight behaviors or withdrawal, immobilization, and dissociation without an intervening “calm” state that would provide opportunities for positive social interactions. This defensive autonomic disposition is adaptive in dangerous and life threatening situations, but in the context of every-day life may lead to significant psychosocial distress and deteriorating social relationships. The perpetuation of these maladaptive autonomic responses may contribute to the development of comorbid mental health issues such as depression, loneliness, and hostility that further modify the nature of cardiovascular behavior in the context of internal and external stressors. Over time, changes in autonomic, endocrine, and immune function contribute to deteriorating health, which is potently expressed in brain dysfunction and cardiovascular disease. In this theoretical review paper, we present an overview of the literature on the chronic health effects of PTSD. We discuss the brain networks underlying PTSD in the context of autonomic efferent and afferent contributions and how disruption of these networks leads to poor health outcomes. Finally, we discuss treatment approaches based on our theoretical model of PTSD.

Intellectual disabilities and power spectra analysis during sleep: a new perspective on borderline intellectual functioning

BACKGROUND

The role of sleep in cognitive processes has been confirmed by a growing number of reports for all ages of life. Analysing sleep electroencephalogram (EEG) spectra may be useful to study cortical organisation in individuals with Borderline Intellectual Functioning (BIF), as seen in other disturbances even if it is not considered a disease. The aim of this study was to determine if the sleep EEG power spectra in children with BIF could be different from typically developing children.

METHODS

Eighteen BIF (12 males) (mean age 11.04; SD ± 1.07) and 24 typical developing children (14 men) (mean age 10.98; SD ± 1.76; P = 0.899) underwent an overnight polysomnography (PSG) recording in the Sleep Laboratory of the Clinic of Child and Adolescent Neuropsychiatry, after one adaptation night. Sleep was subdivided into 30-s epochs and sleep stages were scored according to the standard criteria and the power spectra were calculated for the Cz-A2 channel using the sleep analysis software Hypnolab 1.2 (SWS Soft, Italy) by means of the Fast Fourier Transform and the power spectrum was calculated for frequencies between 0.5 and 60 Hz with a frequency step of 1 Hz and then averaged across the following bands delta (0.5-4 Hz), theta (5-7 Hz), alpha (8-11 Hz), sigma (11-15 Hz), and beta (16-30 Hz), gamma (30-60 Hz) for S2, SWS and REM (Rapid Eye Movement) sleep stages.

RESULTS

BIF have a reduced sleep duration (total sleep time; P < 0.001), and an increased rate of stage shifts (P < 0.001) and awakenings (P < 0.001) and WASO (wakefulness after sleep onset) % (P < 0.001); the stage 2% (P < 0.001), and REM% (P < 0.001) were lower and slow-wave sleep percentage was slightly higher (P < 0.001). All children with BIF had an AHI (apnoea-hypopnea index) less than 1 (mean AHI = 0.691 ± 0.236) with a mean oxygen saturation of 97.6% and a periodic leg movement index (PLMI) less than 5 (mean PLMI = 2.94 ± 1.56). All sleep stages had a significant reduction in gamma frequency (30-60 Hz) (P < 0.001) and an increased delta frequency (0.5-4.0 Hz) (P < 0.001) power in BIF subjects compared with typically developing children.

CONCLUSION

Our findings shed light on the importance of sleep for cognition processes particularly in cognitive borderline dysfunction and the role of EEG spectral power analysis to recognize sleep characteristics in BIF children.

The complexities of defining optimal sleep: empirical and theoretical considerations with a special emphasis on children

The main aim of this paper is to consider relevant theoretical and empirical factors defining optimal sleep, and assess the relative importance of each in developing a working definition for, or guidelines about, optimal sleep, particularly in children. We consider whether optimal sleep is an issue of sleep quantity or of sleep quality. Sleep quantity is discussed in terms of duration, timing, variability and dose-response relationships. Sleep quality is explored in relation to continuity, sleepiness, sleep architecture and daytime behaviour. Potential limitations of sleep research in children are discussed, specifically the loss of research precision inherent in sleep deprivation protocols involving children. We discuss which outcomes are the most important to measure. We consider the notion that insufficient sleep may be a totally subjective finding, is impacted by the age of the reporter, driven by socio-cultural patterns and sleep-wake habits, and that, in some individuals, the driver for insufficient sleep can be viewed in terms of a cost-benefit relationship, curtailing sleep in order to perform better while awake. We conclude that defining optimal sleep is complex. The only method of capturing this elusive concept may be by somnotypology, taking into account duration, quality, age, gender, race, culture, the task at hand, and an individual's position in both sleep-alert and morningness-eveningness continuums. At the experimental level, a unified approach by researchers to establish standardized protocols to evaluate optimal sleep across paediatric age groups is required.

Sleep cyclic alternating pattern and cognition in children: a review

Several studies have been recently focused on the relationship between sleep cyclic alternating pattern (CAP) and daytime cognitive performance, supporting the idea that the CAP slow components may play a role in sleep-related cognitive processes. Based on the results of these reports, it can be hypothesized that the analysis of CAP might be helpful in characterizing sleep microstructure patterns of different phenotypes of intellectual disability and a series of studies has been carried out that are reviewed in this paper. First the studies exploring the correlations between CAP and cognitive performance in normal adults and children are described; then, those analyzing the correlation between CAP and cognitive patterns of several developmental conditions with neurocognitive dysfunction (with or without mental retardation) are reported in detail in order to achieve a unitary view of the role of CAP in these conditions that allows to detect a particular "sleep microstructure phenotype" of children with neurologic/neuropsychiatric disorders.

Disturbed dreaming and the instability of sleep: altered nonrapid eye movement sleep microstructure in individuals with frequent nightmares as revealed by the cyclic alternating pattern

STUDY OBJECTIVES

Nightmares are disturbing mental experiences during sleep that usually result in abrupt awakenings. Frequent nightmares are associated with poor subjective sleep quality, and recent polysomnographic data suggest that nightmare sufferers exhibit impaired sleep continuity during nonrapid eye movement (NREM) sleep. Because disrupted sleep might be related to abnormal arousal processes, the goal of this study was to examine polysomnographic arousal-related activities in a group of nightmare sufferers and a healthy control group.

DESIGN

Sleep microstructure analysis was carried out by scoring the cyclic alternating pattern (CAP) in NREM sleep and the arousal index in rapid eye movement (REM) sleep on the second night of the polysomnographic examination.

SETTING

Hospital-based sleep research laboratory.

PARTICIPANTS

There were 17 in the nightmare (NMs) group and 23 in the healthy control (CTLs) group.

INTERVENTIONS

N/A.

MEASUREMENTS AND RESULTS

The NMs group exhibited reduced amounts of CAP A1 subtype and increased CAP A2 and A3 subtypes, as well as longer duration of CAP A phases in comparison with CTLs. Moreover, these differences remained significant after controlling for the confounding factors of anxious and depressive symptoms. The absolute number and frequency of REM arousals did not differ significantly between the two groups.

CONCLUSIONS

The results of our study indicate that NREM sleep microstructure is altered during nonsymptomatic nights of nightmares. Disrupted sleep in the NMs group seems to be related to abnormal arousal processes, specifically an imbalance in sleep-promoting and arousing mechanisms during sleep.

CITATION

Simor P; Bódizs R; Horváth K; Ferri R. Disturbed dreaming and the instability of sleep: altered nonrapid eye movement sleep microstructure in individuals with frequent nightmares as revealed by the cyclic alternating pattern. SLEEP 2013;36(3):413-419.

Cyclic alternating pattern is associated with cerebral hemodynamic variation: a near-infrared spectroscopy study of sleep in healthy humans

The cyclic alternating pattern (CAP), that is, cyclic variation of brain activity within non-REM sleep stages, is related to sleep instability and preservation, as well as consolidation of learning. Unlike the well-known electrical activity of CAP, its cerebral hemodynamic counterpart has not been assessed in healthy subjects so far. We recorded scalp and cortical hemodynamics with near-infrared spectroscopy on the forehead and systemic hemodynamics (heart rate and amplitude of the photoplethysmograph) with a finger pulse oximeter during 23 nights in 11 subjects. Electrical CAP activity was recorded with a polysomnogram. CAP was related to changes in scalp, cortical, and systemic hemodynamic signals that resembled the ones seen in arousal. Due to their repetitive nature, CAP sequences manifested as low- and very-low-frequency oscillations in the hemodynamic signals. The subtype A3+B showed the strongest hemodynamic changes. A transient hypoxia occurred during CAP cycles, suggesting that an increased CAP rate, especially with the subtype A3+B, which may result from diseases or fragmented sleep, might have an adverse effect on the cerebral vasculature.

The effects of pre-sleep learning on sleep continuity, stability, and organization in elderly individuals

Several studies have consistently shown that pre-sleep learning is associated to changes of sleep structure. Whereas previous research has mainly focused on sleep states, namely REM and NREM amount, very little attention has been paid to the hypothesis that pre-sleep learning might improve sleep continuity, stability, and cyclic organization, which are often impaired in aging. Thus, aim of this research was to assess, in a sample of 18 healthy elderly subjects, whether a memory task administered at bedtime would determine changes in any sleep parameter, with special regard to sleep continuity, stability, and organization. To this purpose, a baseline sleep (BL), i.e., a normal sleep with 9-h time in bed (TIB), was compared to a post-training sleep (TR), with the same TIB but preceded by an intensive training session. For the latter, a verbal declarative task was used, consisting in learning paired-word lists, rehearsed, and recalled for three times in a row. To control for individual learning abilities, subjects were administered several sets of lists with increasing difficulty, until they reached an error rate ≥20% at third recall. Relative to BL, TR shows a significant reduction in the frequency of brief awakenings, arousals, state transitions, "functional uncertainty" (FU) periods, and in the percentage of time in FU over total sleep time (TST). A significant increase in the number of complete cycles, total cycle time (TCT), and TCT/TST proportion was also found. All these changes are evenly distributed over the sleep episode. No sleep stage measure display significant changes, apart from a slight reduction in the percentage of Stage 1. Scores at retest are negatively correlated with both the frequency of arousals and of state transitions. Our data suggest that pre-sleep learning can yield a beneficial re-organizing effect on elderlies' sleep quality. The inverse correlation between recall scores and the measures of sleep continuity and stability provides further support to the role of these features in memory processes.

The role of NREM sleep instability in child cognitive performance

STUDY OBJECTIVES

Based on recent reports of the involvement of cyclic alternating pattern (CAP) in cognitive functioning in adults, we investigated the association between CAP parameters and cognitive performance in healthy children.

DESIGN

Polysomnographic assessment and standardized neurocognitive testing in healthy children.

SETTINGS

Sleep laboratory.

PARTICIPANTS

Forty-two children aged 7.6 ± 2.7 years, with an even distribution of body mass percentile (58.5 ± 25.5) and SES reflective of national norms.

MEASUREMENTS

Analysis of sleep macrostructure following the R&K criteria and of cyclic alternating pattern (CAP). The neurocognitive tests were the Stanford Binet Intelligence Scale (5(th) edition) and a Neuropsychological Developmental Assessment (NEPSY) RESULTS: Fluid reasoning ability was positively associated with CAP rate, particularly during SWS and with A1 total index and A1 index in SWS. Regression analysis, controlling for age and SES, showed that CAP rate in SWS and A1 index in SWS were significant predictors of nonverbal fluid reasoning, explaining 24% and 22% of the variance in test scores, respectively.

CONCLUSION

This study shows that CAP analysis provides important insights on the role of EEG slow oscillations (CAP A1) in cognitive performance. Children with higher cognitive efficiency showed an increase of phase A1 in total sleep and in SWS.

Effects of replacement therapy on sleep architecture in children with growth hormone deficiency

OBJECTIVE

Children with GH deficiency (GHD) show a general decrease in electroencephalographic (EEG) arousability represented by a significant global decrease in Cyclic Alternating Pattern (CAP). The aim of the present study was to evaluate if sleep structure is influenced by GH substitutive therapy by analyzing the classical sleep architecture parameters and sleep microstructure by means of CAP.

SUBJECTS AND METHODS

Laboratory polysomnographic sleep recordings were obtained from five children affected by GHD (two girls and three boys; mean age: 4.6 ± 3.1 years), at baseline and after GH therapy, and from 10 normal healthy children (four girls and six boys, mean age: 5.6 ± 2.2 years).

RESULTS

Compared to controls, GHD subjects showed a reduced total sleep time with increased wakefulness and a consequent decrease in sleep efficiency; GH therapy was associated with an increase of the awakenings/hour and a large effect size was evident for sleep latency, sleep efficiency, and stage N3, which were decreased, and for stage W, which was increased. CAP appeared to be globally reduced and all phase A subtypes and CAP cycle showed a longer duration in GHD children vs. controls. GH substitutive treatment was followed by an increase in CAP rate (total, in N2, and in N3); additionally, A1 index was also significantly increased, especially during stage N3, with a very large effect size. On the other hand, A2 and A3 index and CAP cycle mean duration were reduced.

CONCLUSION

Sleep stage architecture seems to be influenced by the GH status, but the analysis of sleep microstructure by means of CAP reveals an enhancement of EEG slow oscillations in GHD patients (demonstrated by an increase in CAP rate and A1 index during N3) after the start of GH replacement therapy. These findings deserve to be verified in a larger trial.

Cyclic alternating pattern (CAP): the marker of sleep instability

Cyclic alternating pattern CAP is the EEG marker of unstable sleep, a concept which is poorly appreciated among the metrics of sleep physiology. Besides, duration, depth and continuity, sleep restorative properties depend on the capacity of the brain to create periods of sustained stable sleep. This issue is not confined only to the EEG activities but reverberates upon the ongoing autonomic activity and behavioral functions, which are mutually entrained in a synchronized oscillation. CAP can be identified both in adult and children sleep and therefore represents a sensitive tool for the investigation of sleep disorders across the lifespan. The present review illustrates the story of CAP in the last 25 years, the standardized scoring criteria, the basic physiological properties and how the dimension of sleep instability has provided new insight into pathophysiolology and management of sleep disorders.

Sleep characteristics in children with growth hormone deficiency

BACKGROUND/AIMS

Growth hormone (GH) is preferentially secreted during slow wave sleep and the interactions between human sleep and the somatotropic system are well documented, although only few studies have investigated the sleep EEG in children with GH deficiency (GHD). The aim of this study was to evaluate the sleep structure of children with dysregulation of the GH/insulin-like growth factor axis.

METHODS

Laboratory polysomnographic sleep recordings were obtained from 10 GHD children and 20 normal healthy age-matched children. The classical sleep parameters were evaluated together with sleep microstructure, by means of the cyclic alternating pattern (CAP), in GHD patients and compared to the control group.

RESULTS

GHD children showed a significant decrease in total sleep time, sleep efficiency, movement time and in non-rapid eye movement sleep stage 2. Although some indicators of sleep fragmentation were increased in GHD children, we found a general decrease in EEG arousability represented by a significant global decrease in the CAP rate, involving all CAP A phase subtypes.

CONCLUSIONS

The analysis of sleep microstructure by means of CAP, in children with GHD, showed a reduction of transient EEG amplitude oscillations. Further studies are needed in order to better clarify whether GH therapy is able to modify sleep microstructure in GHD children, and the relationships between sleep microstructure, hormonal secretion and neurocognitive function in these patients.

The effects of experimental sleep fragmentation on cognitive processing

OBJECTIVE

The primary objective of this study was to characterize the association between cyclic alternating pattern (CAP) and neurocognitive performance in a group of normal subjects before and after two nights of experimentally-induced sleep fragmentation.

SUBJECTS AND METHODS

Fifteen healthy subjects underwent one night of uninterrupted and two sequential nights of experimental sleep fragmentation achieved by auditory and mechanical stimuli. Eight subjects were re-examined using a similar paradigm with three nights of uninterrupted sleep. Sleep was polygraphically recorded and CAP analysis was performed for all recordings. A battery of neurocognitive tests was performed for spatial attention, inhibition of return, mental rotation, and Stroop color word test in the afternoon following the first and third night of sleep under fragmented and non-fragmented conditions.

RESULTS

With sleep fragmentation, the percentage of slow-wave sleep was dramatically reduced and there was a twofold increase in total CAP rate across all NREM sleep stages. Moreover, the number of all CAP A subtypes/hour of sleep (index) was significantly increased. Total CAP rate during the non-fragmented night correlated with reaction times. Similarly, the percentages of A1 and A3 subtypes were negatively and positively correlated with reaction times, respectively. Of the neurocognitive test battery, however, only values obtained from some subtests of the mental rotation test showed a significant improvement after sleep fragmentation.

CONCLUSIONS

The results of this study suggest that CAP A1 subtypes are associated with higher cognitive functioning, whereas CAP A3 subtypes are associated with lower cognitive functioning in young healthy subjects. The lack of cognitive functioning impairment after sleep fragmentation may be due to persistence and even enhancement of transient slow-wave activity contained in CAP A1 subtypes which also caused a significant enhancement of the EEG power spectrum in the lower frequencies.