Rapid eye movement sleep behaviour disorder: demographic, clinical and laboratory findings in 93 cases

Periodic limb movements in REM sleep: A periodically concerning phenomenon

Periodic limb movements of sleep (PLMS) are involuntary, sleep-related phenomena characterized by periodic episodes of repetitive, stereotypical movements of the limbs. The presence PLMS increases with age but are frequently comorbid with other sleep disorders and other medical, neurologic, and psychiatric disorders, and can be triggered by medications and psychoactive substances. PLMS typically occur during non-rapid eye movement sleep and are generally absent during rapid eye movement (REM) sleep, with exception of patients with REM behavior disorder (RBD). However, even in the absence of RBD, PLMS are sometimes noted in REM sleep, without a clear explanation or etiology. This systematic review will focus on what is known about PLMS, as they relate to REM sleep phenomenon: PLMS in RBD, in REM sleep without atonia, and in various sleep and neurologic will be discussed.

A FAM8A1 frameshift variant is associated with REM sleep behavior disorder, urinary retention, and mydriasis in Russian Blue cats

REM sleep behavior disorder (RBD) is a disease characterized by the loss of lower motor neuron inhibition responsible for skeletal muscle atonia during REM sleep. It has been reported in humans, dogs and cats, and can be idiopathic or secondary to a neurodegenerative disease. Five young adult Russian Blue cats from two related families were presented for progressively worsening RBD episodes frequently associated with urinary loss. Three of these cats also suffered urinary retention with overflow incontinence between RBD episodes. Neurological examination revealed a large bladder in three cats and a bilateral mydriasis with absent pupillary light reflexes in two cats; further examinations were unremarkable. Treatment attempts were unsatisfactory, with four cats being euthanized. Histopathology of the brain did not reveal any abnormalities. A disease-associated 23-bp deletion in exon 1 of FAM8A1 (NC_058372.1:g.11622168_11622190del), introducing a frameshift at codon 162 and a premature stop codon at codon 276 (XM_019831563.3:c.485_507del p.(Gln162Profs*115)), was identified by whole genome sequencing. The variant segregated in the affected families with a recessive mode of inheritance, showed an allele frequency of 1.5% in West-European Russian Blue cats (N = 68) and was not present in 276 cats belonging to 32 other breeds (including the closely related Nebelung breed). The variant FAM8A1 isoform is predicted to affect the assembly and activity of the endoplasmic reticulum-associated protein degradation pathway, which plays an important role in cell homeostasis. RBD and urinary retention syndrome is a hereditary encephalopathy affecting Russian Blue cats. A genetic test now allows diagnosis and prevention of this debilitating disease.

Polysomnographic biomarkers for persisting (isolated) REM sleep without atonia in patients with obstructive sleep apnea

BACKGROUND

The relationship between obstructive sleep apnea (OSA) and REM sleep without atonia (RSWA) is complex and not fully understood. While RSWA may prevent upper airway collapse during REM sleep, it can also mimic REM sleep behavior disorder (RBD) and be a potential biomarker for neurodegeneration. This study aims to identify the prevalence, characteristics, and predictors of persistent isolated RSWA (iRSWA) following positive airway pressure (PAP) therapy in OSA patients.

METHODS

A retrospective analysis was conducted on 297 patients with both OSA and RSWA who underwent polysomnography (PSG) with PAP titration. RSWA was assessed using both visual and automated methods. Clinical and PSG parameters were compared between patients with and without persistent RSWA after PAP titration. Statistical analyses, including receiver operating characteristic (ROC) curve analysis, were performed to identify significant predictors of persistent RSWA.

RESULTS

Persistent RSWA was observed in 41.5 % of patients. Older age (p = 0.006), higher periodic limb movement index (PLMSI) (p = 0.034), and lower apnea-hypopnea index (AHI) (p = 0.048) were significantly associated with persistent RSWA. ROC analysis identified four key PSG biomarkers - RSWA duration/REM duration, RSWA duration/total apnea-hypopnea duration (tAHD) in REM sleep, tAHD in REM sleep/REM duration, and REM atonia index - that strongly predicted persistent RSWA (OR = 10.714, p = 0.024).

CONCLUSIONS

A substantial portion of RSWA observed in OSA patients (approximately 40 %) was not directly related to OSA and persisted despite PAP therapy. These findings suggest that persistent RSWA may indicate iRSWA, a potential prodromal biomarker for neurodegenerative disorders. The identified PSG biomarkers may improve differentiation between iRSWA and OSA-related RSWA, aiding in early diagnosis and prognostic evaluation.

Symptomatic treatment of REM sleep behavior disorder (RBD): A consensus from the international RBD study group - Treatment and trials working group

Rapid-eye-movement sleep behavior disorder (RBD) is a parasomnia causing motor behaviors and vocalizations during sleep, which can lead to injuries in patients and their bed partners. Adult-onset RBD generally precedes a neurodegenerative synucleinopathy, while other cases can be associated with antidepressant use, neurotrauma and narcolepsy. The management of RBD relies on the systematic identification of etiologic and contributing factors, implementation of safety measures, appropriate pharmacotherapy and counseling, which should be patient-centered. In this manuscript, we summarize the evidence on the management of RBD. We summarize the evidence supporting the use of clonazepam, melatonin, rivastigmine, and pramipexole, the four agents currently recommended by the American Academy of Sleep Medicine. For each agent and for alternative therapies, we discuss efficacy, dosing, adverse effects and indications. We integrate the current knowledge on therapies in RBD in treatment algorithms that can guide providers in choosing the most appropriate initial therapy, and alternative options based on the course of symptoms and comorbidities. There is a large need for additional, well tolerated therapies for reducing RBD symptoms. The last section of this manuscript discusses current challenges and unmet needs, as well as future directions in developing therapies and improving the care of patients with RBD.

REM sleep behaviour disorder (RBD): Personal perspectives and research priorities

The formal identification and naming of rapid eye movement (REM) sleep behaviour disorder (RBD) in 1985-1987 is described; the historical background of RBD from 1966 to 1985 is briefly discussed; and RBD milestones are presented. Current knowledge on RBD is identified with reference to recent comprehensive reviews, allowing for a focus on research priorities for RBD: factors and predictors of neurodegenerative phenoconversion from isolated RBD and patient enrolment in neuroprotective trials; isolated RBD clinical research cohorts; epidemiology of RBD; traumatic brain injury, post-traumatic stress disorder, RBD and neurodegeneration; depression, RBD and synucleinopathy; evolution of prodromal RBD to neurodegeneration; gut microbiome dysbiosis and colonic synuclein histopathology in isolated RBD; other alpha-synuclein research in isolated RBD; narcolepsy-RBD; dreams and nightmares in RBD; phasic REM sleep in isolated RBD; RBD, periodic limb movements, periodic limb movement disorder pseudo-RBD; other neurophysiology research in RBD; cardiac scintigraphy (123I-MIBG) in isolated RBD; brain magnetic resonance imaging biomarkers in isolated RBD; microRNAs as biomarkers in isolated RBD; actigraphic, other automated digital monitoring and machine learning research in RBD; prognostic counselling and ethical considerations in isolated RBD; and REM sleep basic science research. RBD research is flourishing, and is strategically situated at an ever-expanding crossroads of clinical (sleep) medicine, neurology, psychiatry and neuroscience.

Association of early-onset psychiatric disorders with REM sleep behavior disorder - A retrospective study

BACKGROUND

REM sleep behaviour disorder (RBD) is a known predictor of the subsequent development of neurodegenerative diseases, particularly Parkinson's disease and other alpha synucleinopathies. RBD has also been found to be common among children with other psychiatric disorders such as anxiety, depression, and ADHD.

OBJECTIVE

This retrospective study aims to analyze the prevalence of early-onset psychiatric disorders among patients referred for RBD to our sleep laboratory. Our hypothesis is that early-onset psychiatric disorders are more common in patients with polysomnographically confirmed RBD.

METHODS

A retrospective chart review was performed through the Kingston Health Sciences Centre (KHSC) Sleep Laboratory. Data collection involved gathering information regarding the patient's sleep study, psychiatric diagnoses and/or symptoms, mental health medication history and any neurodegenerative conditions noted in hospital clinical notes.

RESULTS

Patients referred for and polysomnographically confirmed RBD were more likely to have presented with symptoms, or received a clinical diagnosis, of an early-onset psychiatric disorder at 32 % compared to the obstructive sleep apnea (OSA) control group at 3 %.

CONCLUSIONS

History of early-onset psychiatric disorders is more common among patients referred as RBD compared to a control group of patients with OSA. Future studies are required to confirm the validity and replicability of this finding.

Sleep related injury and its correlates in isolated rapid eye movement sleep behavior disorder

OBJECTIVES

To evaluate factors associated with sleep related injury (SRI) and persistent SRI (pSRI) in patients with isolated rapid eye movement sleep behavior disorder (iRBD).

METHODS

This is a retrospective cohort study. A total of 388 patients with iRBD were involved for a comprehensive review of sleep related injuries. SRI is defined as a lifetime history of injurious behaviors to self and/or bed partner, and pSRI is considered if injurious symptoms continued to occur frequently (≥1/month). Correlations of SRI/pSRI with clinical, lifestyle and polysomnographic characteristics were analyzed.

RESULTS

Lifetime SRI was reported in 322 (83 %) patients (66.3 ± 8.5 years old, male 77.0 %), with 19.3 % having severe injuries, including fractures (2.5 %) and subdural hemorrhage (1.2 %), while 7.5 % required medical attendance. SRI was related to more severe depressive features (Padj = 0.017), current alcohol drinking (Padj = 0.014) and higher mentalis phasic and tonic EMG activity (Padj = 0.042 and 0.048). After a mean follow-up of 5.1 years, 18.2 % of SRI patients (38/209) had pSRI despite intense treatment. Frequent nightmare at baseline (OR [95 % CI] = 1.43 [1.01, 2.03]), restless leg syndrome (OR [95 % CI] = 5.68 [1.42, 22.64]) and adult-onset sleepwalking (OR [95 % CI] = 2.52 [1.10, 5.76]) were associated with an increased risk of pSRI.

CONCLUSIONS

SRI is common in patients with iRBD and 18 % had pSRI despite intensive treatment, emphasizing the importance of bedside safety. The identification of risk factors for SRI and pSRI underscores the need for systematic clinical screening and targeted interventions for at-risk patients.

Parkinson's disease subtypes and their association with probable rapid eye movement sleep behavior disorder severity: a brainstem tractography and machine learning investigation

Rapid Eye Movement (REM) sleep behavior disorder (RBD) affects nearly half of Parkinson's disease (PD) patients. However, the structural heterogeneity within the brainstem, which regulates REM sleep, remains largely unexplored in PD. Our objective was to identify distinct PD subtypes based on microstructural characteristics in the brainstem and examine their associations with the severity of RBD. Data, including diffusion tensor imaging and REM sleep behavior disorder screening questionnaire (RBDSQ) responses, were obtained from 124 PD patients and 61 healthy controls through the Parkinson's Progression Marker Initiative database. Mean Quantitative Anisotropy (QA) values, representing axonal density, were extracted from 14 brainstem tracts and input into the semi-supervised machine learning algorithm, Heterogeneity through Discriminative Analysis (HYDRA), to cluster subtypes. Applying HYDRA, we identified two distinct PD subtypes (Subtype 1: n = 66, Subtype 2: n = 58). Subtype 2 exhibited reduced QA across assessed brainstem tracts and significantly higher RBDSQ scores than Subtype 1 and healthy controls (p < 0.001). Conversely, Subtype 1, characterized by lower RBDSQ scores, exhibited increased QA, notably in the right medial longitudinal fasciculus, when compared to Subtype 2 and controls (p < 0.001). These findings suggest that heterogeneous axonal damage in brainstem circuits correlates with variations in RBD severity, providing insights into the neurobiological underpinnings of early PD.

Audiovisual analysis of the diagnostic video polysomnography in patients with isolated REM sleep behavior disorder

BACKGROUND

The diagnosis of isolated REM sleep behavior disorder (IRBD) requires video polysomnography (V-PSG) showing increased muscle activity and abnormal behaviors in REM sleep.

OBJECTIVE

To describe in IRBD the behavioral manifestations occurring during REM sleep in the diagnostic V-PSG.

METHODS

This is a systematic audiovisual V-PSG analysis of consecutive IRBD patients. According to the International RBD Study Group recommendations, REM sleep movements and vocalizations were classified into categories and severity.

RESULTS

We analyzed the V-PSG of 62 IRBD patients with a mean age of 67.6 ± 8.1 years. Of 6,330 30-s epochs of REM sleep, 55.1% epochs exhibited motor events, 5.5% contained vocalizations and 39.4% were silent. Among the epochs with motor manifestations, 66.1% contained simple minor movements, 25.0% simple major and 8.9% complex movements. Motor severity of the epochs was mild in 82.2%, moderate in 13.2% and severe in 4.6%. Most movements were bilateral (62.4%) and located in the upper limbs (42.5%). Of the epochs with vocalizations, 61.5% were simple minor, 20.7% complex and 17.8% simple major of mild (72.7%), moderate (23.0%) and severe (4.3%) severity. Complex movements occurred in 87.1% of the patients and complex vocalizations in 38.7%.

CONCLUSIONS

In IRBD, the most common manifestations in REM sleep are simple minor movements and vocalizations of mild intensity. Complex movements are observed during REM sleep in most patients but are much less frequent than simple minor and major motor events. These findings should be considered for the routine diagnosis of IRBD when reviewing the V-PSG studies.

The clinical use of dream content in modern psychiatry

OBJECTIVE

Though there is a rich psychoanalytic tradition investigating the content and phenomenology of dreams, the clinical use of this has fallen into widespread disuse. We have undertaken a narrative review of the clinical significance and utility of dream content.

FINDINGS

Dream content may have useful clinical and prognostic value in a number of neurological and psychiatric conditions, including schizophrenia, borderline personality disorder, temporal lobe epilepsy, REM sleep behaviour disorder, dementia, the culture-bound syndrome of Latah, and substance use.

CONCLUSIONS

This review highlights the importance of dream phenomenology in clinical practice. Building on the psychoanalytic tradition, the findings of our review should motivate clinicians to regularly enquire about dream content, in order to enhance diagnostic insights and formulations of patient presentations.

Clinical characteristics and phenoconversion in isolated REM sleep behavior disorder: a prospective single-center study in Korea, compared with Montreal cohort

STUDY OBJECTIVES

Isolated rapid eye movement sleep behavior disorder is a prodromal synucleinopathy, but its conversion rate and subtypes can vary among different cohorts. We report the clinical characteristics and phenoconversion rate of the large single-center isolated rapid eye movement sleep behavior disorder cohort in Korea and compared it to the Montreal cohort.

METHODS

This prospective cohort study examined 238 patients with polysomnography confirmed isolated rapid eye movement sleep behavior disorder from Seoul National University Hospital (SNUH) who completed at least 1 follow-up evaluation. We compared the baseline and phenoconversion data of the SNUH cohort to those of 242 isolated rapid eye movement sleep behavior disorder patients in the Montreal cohort.

RESULTS

In the SNUH cohort, age at rapid eye movement sleep behavior disorder diagnosis was similar (66.4 ± 7.8 vs 65.6 ± 8.4, P = .265), but the proportion of men was lower (63.0% vs 74.0%, P = .01), and the duration of follow-up was shorter than that in the Montreal cohort (3.7 ± 2.0 vs 4.8 ± 3.6 years, P < .001). During follow-up, 34 (11.8%) patients in the SNUH cohort converted to neurodegenerative disease: 18 (52.9%) to Parkinson's disease, 9 (26.5%) to dementia with Lewy bodies, and 7 (20.6%) to multiple system atrophy. The conversion rate in the SNUH cohort was 15% after 3 years, 22% after 5 years, and 32% after 7 years, which was significantly lower than that of the Montreal cohort (log-rank test, P = .002). Among phenoconversion subtype, fewer patients in the SNUH group than in the Montreal group converted to dementia with Lewy bodies (Gray's test P = .001).

CONCLUSIONS

Through a comparative analysis between the SNUH and Montreal cohorts, we identified a significant difference in phenoconversion rates, particularly for dementia with Lewy bodies patients. These findings underscore the importance of further research into the underlying factors, such as racial and geographical factors contributing to such disparities.

CITATION

Byun J-I, Sunwoo J-S, Shin YW, et al. Clinical characteristics and phenoconversion in isolated REM sleep behavior disorder: a prospective single-center study in Korea, compared with Montreal cohort. J Clin Sleep Med. 2025;21(1):81-88.

Bibliometric and visual study of narcolepsy from 2000 to 2023

BACKGROUND

More studies explored the prevalence, causes, associated conditions, and therapeutic strategies of narcolepsy. With an increasing focus on understanding narcolepsy's prevalence, associated conditions, and therapeutic strategies, there's a notable absence of bibliometric analyses summarizing trends in research and identifying emerging areas of focus within this field.

AIM

To conduct a bibliometric analysis to investigate the current status and frontiers of narcolepsy.

METHODS

The documents related to narcolepsy are obtained from the Web of Science Core Collection database (WoSCC) from January 1, 2000, to December 31, 2023, and VOS viewer 1.6.16, and the WoSCC's literature analysis wire were used to conduct the bibliometric analysis.

RESULTS

A total of 4672 publications related to narcolepsy were included, and 16182 authors across 4397 institutions and 96 countries/regions contributed to these documents in 1131 different journals. The most productive author, institution, country and journal were Yves Dauvilliers, Stanford University, United States, and Sleep Medicine, respectively. The first high-cited document was published in Nature in 2005 by Saper et al, and this research underscores the role of certain neurons in ensuring the stability of sleep-wake transitions, offering insights into narcolepsy's pathophysiology.

CONCLUSION

In conclusion, the main research hotspots and frontiers in the field of narcolepsy are the diagnosis of narcolepsy, pathological mechanism of narcolepsy and the treatment of narcolepsy. More studies are needed to explore effective strategies for the diagnosis and treatment of narcolepsy.

A pontine-medullary loop crucial for REM sleep and its deficit in Parkinson's disease

Identifying the properties of the rapid eye movement (REM) sleep circuitry and its relation to diseases has been challenging due to the neuronal heterogeneity of the brainstem. Here, we show in mice that neurons in the pontine sublaterodorsal tegmentum (SubLDT) that express corticotropin-releasing hormone-binding protein (Crhbp+ neurons) and project to the medulla promote REM sleep. Within the medullary area receiving projections from Crhbp+ neurons, neurons expressing nitric oxide synthase 1 (Nos1+ neurons) project to the SubLDT and promote REM sleep, suggesting a positively interacting loop between the pons and the medulla operating as a core REM sleep circuit. Nos1+ neurons also project to areas that control wide forebrain activity. Ablating Crhbp+ neurons reduces sleep and impairs REM sleep atonia. In Parkinson's disease patients with REM sleep behavior disorders, CRHBP-immunoreactive neurons are largely reduced and contain pathologic α-synuclein, providing insight into the mechanisms underlying the sleep deficits characterizing this disease.

High bioavailable testosterone levels increase the incidence of isolated REM sleep behavior disorder: Results from multivariable and network Mendelian randomization analysis

OBJECTIVES

To explore the causal relationships between sex hormone levels and incidence of isolated REM sleep behavior disorder (iRBD).

METHODS

In our study, we utilized Genome-Wide Association Studies (GWAS) data for iRBD, including 9447 samples with 1061 cases of iRBD provided by the International RBD Study Group. Initially, we conducted a two-sample univariate MR analysis to explore the impact of sex hormone-related indicators on iRBD. This was followed by the application of multivariable MR methods to adjust for other hormone levels and potential confounders. Finally, we undertook a network MR analysis, employing brain structure Magnetic Resonance Imaging (MRI) characteristics as potential mediators, to examine whether sex hormones could indirectly influence the incidence of iRBD by affecting brain structure.

RESULTS

Bioavailable testosterone (BioT) is an independent risk factor for iRBD (Odds Ratio [95 % Confidence Interval] = 2.437 [1.308, 4.539], P = 0.005, corrected-P = 0.020), a finding that remained consistent even after adjusting for other sex hormone levels and potential confounders. Additionally, BioT appears to indirectly increase the risk of iRBD by reducing axial diffusivity and increasing the orientation dispersion index in the left cingulum and cingulate gyrus.

CONCLUSIONS

Our research reveals that elevated levels of BioT contribute to the development of iRBD. However, the specific impact of BioT on different sexes remains unclear. Furthermore, high BioT may indirectly lead to iRBD by impairing normal pathways in the left cingulum and cingulate gyrus and fostering abnormal pathway formation.

Comparison of number of people with freezing of gait in Parkinson's disease with and without sleep disturbances: A systematic review

Parkinson's disease (PD) is a progressive neurodegenerative disorder, involving motor and non-motor symptoms (NMS). Sleep disturbances (SD) are the second most common NMS in PD and include rapid eye movement (REM) sleep behavior disorder (RBD), excessive daytime sleepiness and insomnia. Freezing of gait (FOG) is a gait impairment frequently reported in people with PD greatly hampering functional independence and quality of life. Presence of FOG has been associated with increased frequency and severity of NMS, including SD. Thus, the aim of this study was to systematically review the literature comparing the number of people with FOG in PD with (PD + SD) and without SD (PD-SD). By systematically searching PubMed and Web of Science databases to identify original peer-reviewed articles, 8 studies including 5251 people with PD (2025 PD + SD and 3226 PD-SD) met eligibility criteria and were included in the review. In 6 studies (4 studies investigating RBD, 2 studies investigating overall sleep quality), the group of PD + SD had higher prevalence of FOG compared with PD-SD. Although a limited number of studies, our findings suggest that PD + SD present more frequently FOG than PD-SD. More studies are required to investigate the possible mechanism underlying this association between FOG and sleep.

A circadian clock regulates the blood-brain barrier across phylogeny

As the central regulatory system of an organism, the brain is responsible for overseeing a wide variety of physiological processes essential for an organism's survival. To maintain the environment necessary for neurons to function, the brain requires highly selective uptake and elimination of specific molecules through the blood-brain barrier (BBB). As an organism's activities vary throughout the day, how does the BBB adapt to meet the changing needs of the brain? A mechanism is through temporal regulation of BBB permeability via its circadian clock, which will be the focal point of this chapter. To comprehend the circadian clock's role within the BBB, we will first examine the anatomy of the BBB and the transport mechanisms enabling it to fulfill its role as a restrictive barrier. Next, we will define the circadian clock, and the discussion will encompass an introduction to circadian rhythms, the Transcription-Translation Feedback Loop (TTFL) as the mechanistic basis of circadian timekeeping, and the organization of tissue clocks found in organisms. Then, we will cover the role of the circadian rhythms in regulating the cellular mechanisms and functions of the BBB. We discuss the implications of this regulation in influencing sleep behavior, the progression of neurodegenerative diseases, and finally drug delivery for treatment of neurological diseases.

Static and dynamic brain morphological changes in isolated REM sleep behavior disorder compared to normal aging

Objective/background

To assess whether cerebral structural alterations in isolated rapid eye movement sleep behavior disorder (iRBD) are progressive and differ from those of normal aging and whether they are related to clinical symptoms.

Patients/methods

In a longitudinal study of 18 patients with iRBD (age, 66.1 ± 5.7 years; 13 males; follow-up, 1.6 ± 0.6 years) and 24 age-matched healthy controls (age, 67.0 ± 4.9 years; 12 males; follow-up, 2.0 ± 0.9 years), all participants underwent multiple extensive clinical examinations, neuropsychological tests, and magnetic resonance imaging at baseline and follow-up. Surface-based cortical reconstruction and automated subcortical structural segmentation were performed on T1-weighted images. We used mixed-effects models to examine the differences between the groups and the differences in anatomical changes over time.

Results

None of the patients with iRBD demonstrated phenoconversion during the follow-up. Patients with iRBD had thinner cortices in the frontal, occipital, and temporal regions, and more caudate atrophy, compared to that in controls. In similar regions, group-by-age interaction analysis revealed that patients with iRBD demonstrated significantly slower decreases in cortical thickness and caudate volume with aging than that observed in controls. Patients with iRBD had lower scores on the Korean version of the Mini-Mental Status Examination (p = 0.037) and frontal and executive functions (p = 0.049) at baseline than those in controls; however, no significant group-by-age interaction was identified.

Conclusion

Patients with iRBD show brain atrophy in the regions that are overlapped with the areas that have been documented to be affected in early stages of Parkinson's disease. Such atrophy in iRBD may not be progressive but may be slower than that in normal aging. Cognitive impairment in iRBD is not progressive.

Dreaming Characteristics in Non-Rapid Eye Movement Parasomnia and Idiopathic Rapid Eye Movement Sleep Behaviour Disorder: Similarities and Differences

Background

Speech graph analysis (SGA) of dreams has recently shown promise as an objective and language-invariant diagnostic tool that can aid neuropsychiatric diagnosis. Whilst the notion that dreaming mentations reflect distinct physiologic processes is not new, such studies in patients with sleep disorders remain exceptionally scarce. Here, using SGA and other dream content analyses, we set to investigate structural and thematic differences in morning dream recalls of patients diagnosed with Non-Rapid Eye Movement Parasomnia (NREMP) and Idiopathic REM Sleep Behavior Disorder (iRBD).

Methods

A retrospective cross-sectional study of morning dream recalls of iRBD and NREMP patients was undertaken. Traditional dream content analyses, such as Orlinsky and Hall and Van de Castle analyses, were initially conducted. Subsequently, SGA was performed in order to objectively quantify structural speech differences between the dream recalls of the two patient groups.

Results

Comparable rate of morning recall of dreams in the sleep laboratory was recorded; 25% of iRBD and 18.35% of NREMP patients. Aggression in dreams was recorded by 28.57% iRBD versus 20.00% in NREMP group. iRBD patients were more likely to recall dreams (iRBD vs NREMP; P = 0.007), but they also had more white dreams, ie having a feeling of having dreamt, but with no memory of it. Visual and quantitative graph speech analyses of iRBD dreams suggested stable sequential structure, reflecting the linearity of the chronological narrative. Conversely, NREMP dream reports displayed more recursive, less stable systems, with significantly higher scores of graph connectivity measures.

Conclusion

The findings of our exploratory study suggest that iRBD and NREMP patients may not only differ on what is recalled in their dreams but also, perhaps more strikingly, on how dreams are recalled. It is hoped that future SGA-led dream investigations of larger groups of patients will help discern distinct mechanistic underpinnings and any associated clinical implications.

Rapid Eye Movement Sleep Behavior Disorder: Clinical Presentation and Diagnostic Criteria

Rapid eye movement (REM) sleep behavior disorder (RBD) classically presents with repetitive complex motor behavior during sleep with associated dream mentation. The diagnosis requires a history of repetitive complex motor behaviors and polysomnographic demonstration of REM sleep without atonia (RSWA) or capturing dream enactment behaviors. RSWA is best evaluated in the chin or flexor digitorum superficialis muscles. The anterior tibialis muscle is insufficiently accurate to be relied upon solely for RBD diagnosis. RBD may present with parkinsonism or cognitive impairment or may present in isolation. Patients should be monitored for parkinsonism, autonomic failure, or cognitive impairment.

Acute REM sleep behaviour disorder associated with alcohol withdrawal: A case report and literature review

INTRODUCTION

Rapid eye movement (REM) sleep behaviour disorder (RBD) is a parasomnia characterised by the loss of REM sleep muscle atonia and the enactment of dreams. Acute RBD associated with alcohol withdrawal syndrome is known, but the studies are limited, particularly on its neurobiological underpinnings and management alongside the withdrawal state. This work attempts to address this using a case study and relevant literature review.

CASE PRESENTATION

A 40-year-old male with alcohol dependence (for 20 years) reported new-onset terrifying nightmares and violent behaviours in his sleep precipitated by alcohol withdrawal states for the last 18 months. The polysomnographic finding of REM-without-atonia supported the diagnosis of RBD. He was treated with chlordiazepoxide 100 mg/day (gradually tapered and stopped) and thiamine supplements. Post-discharge, he remained abstinent and symptom-free during the three months of follow-up.

DISCUSSION

RBD related to alcohol withdrawal syndrome has been previously described in a few anecdotal reports. Sudden withdrawal from central nervous system suppressants like alcohol is hypothesised to cause a homeostatic imbalance in gamma-aminobutyric acid (GABA) pathways and 'REM rebound', resulting in the clinical and polysomnographic picture of RBD. Benzodiazepines have been found to be useful in both RBD and alcohol withdrawal.

CONCLUSIONS

Alcohol withdrawal syndrome may present with acute RBD, which can be treated with a short course of benzodiazepine. However, further studies are needed to explore the long-term course of RBD in these patients.

Causal associations between modifiable risk factors and isolated REM sleep behavior disorder: a mendelian randomization study

Objectives

This Mendelian randomization (MR) study identified modifiable risk factors for isolated rapid eye movement sleep behavior disorder (iRBD).

Methods

Genome-wide association study (GWAS) datasets for 29 modifiable risk factors for iRBD in discovery and replication stages were used. GWAS data for iRBD cases were obtained from the International RBD Study Group. The inverse variance weighted (IVW) method was primarily employed to explore causality, with supplementary analyses used to verify the robustness of IVW findings. Co-localization analysis further substantiated causal associations identified via MR. Genetic correlations between mental illness and iRBD were identified using trait covariance, linkage disequilibrium score regression, and co-localization analyses.

Results

Our study revealed causal associations between sun exposure-related factors and iRBD. Utilizing sun protection (odds ratio [OR] = 0.31 [0.14, 0.69], p = 0.004), ease of sunburn (OR = 0.70 [0.57, 0.87], p = 0.001), childhood sunburn occasions (OR = 0.58 [0.39, 0.87], p = 0.008), and phototoxic dermatitis (OR = 0.78 [0.66, 0.92], p = 0.003) decreased iRBD risk. Conversely, a deep skin color increased risk (OR = 1.42 [1.04, 1.93], p = 0.026). Smoking, alcohol consumption, low education levels, and mental illness were not risk factors for iRBD. Anxiety disorders and iRBD were genetically correlated.

Conclusion

Our study does not corroborate previous findings that identified smoking, alcohol use, low education, and mental illness as risk factors for iRBD. Moreover, we found that excessive sun exposure elevates iRBD risk. These findings offer new insights for screening high-risk populations and devising preventive measures.

Gender Difference in REM Sleep Behavior Disorder in Japanese Population: Polysomnography and Sleep Questionnaire Study

Rapid eye movement (REM) sleep behavior disorder (RBD) is generally common among males and is an established risk factor for neurodegenerative diseases. As the population ages, the prevalence of α-synucleinopathy (such as Parkinson's disease) is increasing. Additionally, the number of female patients is increasing in Japan. Therefore, we aimed to clarify the clinical characteristics of RBD from the perspective of gender differences in the Japanese population. The proportion of male RBD patients (65.2%) was significantly higher than that of female patients (34.8%). Additionally, female patients (70.5 ± 8.2 years) were significantly older than male patients (67.9 ± 8.0 years, p < 0.05). The mean score on the RBD Screening Questionnaire was significantly higher in male patients than in female (8.6 ± 2.9 vs. 7.7 ± 3.1, p < 0.05), while the mean score on the Pittsburgh Sleep Quality Index was significantly higher in males (5.9 ± 3.8 vs. 7.2 ± 3.600, p < 0.001). The Self-rating Depression Scale in females was 41.7 ± 8.5, and they were more likely to show depressive tendencies than males. In polysomnography, higher rates of obstructive sleep apnea and longer duration of stage N1 sleep were detected in males. After adjusting for age, BMI, and polysomnographic parameters, we found that female RBD patients had significantly worse sleep quality and rates of depression compared to male patients.

Sleep Disorders and Aging in Women

Women of advancing age can suffer from an array of sleep disorders. We review the changes in sleep architecture, the impact of hormonal changes on sleep, and the various sleep disorders in women of advancing age. A focused history in this population should include the temporal relation to menopause and comorbid conditions. Treatment options should involve patient preference and review of current medications and comorbid conditions to optimize sleep in this population.

REM sleep behavior disorder: update on diagnosis and management

REM sleep behavior disorder (RBD) is characterized by a loss of atonia of skeletal muscles during REM sleep, associated with acting out behaviors during dreams. Knowledge of this pathology is important to predict neurodegenerative diseases since there is a strong association of RBD with diseases caused by the deposition of alpha-synuclein in neurons (synucleinopathies), such as Parkinson's disease (PD), multiple system atrophy (MSA), and dementia with Lewy bodies (DLB). Proper diagnosis of this condition will enable the use of future neuroprotective strategies before motor and cognitive symptoms. Diagnostic assessment should begin with a detailed clinical history with the patient and bed partner or roommate and the examination of any recorded home videos. Polysomnography (PSG) is necessary to verify the loss of sleep atonia and, when documented, the behaviors during sleep. Technical recommendations for PSG acquisition and analysis are defined in the AASM Manual for the scoring of sleep and associated events, and the PSG report should describe the percentage of REM sleep epochs that meet the criteria for RWA (REM without atonia) to better distinguish patients with and without RBD. Additionally, PSG helps rule out conditions that may mimic RBD, such as obstructive sleep apnea, non-REM sleep parasomnias, nocturnal epileptic seizures, periodic limb movements, and psychiatric disorders. Treatment of RBD involves guidance on protecting the environment and avoiding injuries to the patient and bed partner/roommate. Use of medications are also reviewed in the article. The development of neuroprotective medications will be crucial for future RBD therapy.

Altered connectivity in the cognitive control-related prefrontal cortex in Parkinson's disease with rapid eye movement sleep behavior disorder

Rapid eye movement sleep behavior disorder (RBD) frequently occurs in Parkinson's disease (PD), however, the exact pathophysiological mechanism is not clear. The prefrontal cortex (PFC), especially ventrolateral prefrontal cortex (VLPFC), dorsolateral prefrontal cortex (DLPFC), and inferior frontal gyrus (IFG) which may play roles by regulating cognitive control processes. The purpose of this study was to investigate whether there is abnormal functional connectivity (FC) maps and volume changes in PD with RBD(PD-RBD). We recruited 20 PD-RBD, 20 PD without RBD (PD-nRBD), and 20 normal controls (NC). We utilized resting-state functional Magnetic Resonance Imaging (rs-MRI) to explore FC changes based on regions of interest (VLPFC, DLPFC, and IFG), and used voxel-based morphology technology to analyze whole-brain volumes by 3D-T1 structural MRI. Except the REM sleep behavioral disorders questionnaire (RBDSQ), the PD-RBD showed lower visuospatial/executive and attention scores than the NC group. The RBDSQ scores were significantly positively correlated with zFC of right DLPFC to bilateral posterior cingulate cortex (PCC) (P = 0.0362, R = 0.4708, AlphaSim corrected) and also significantly positively correlated with zFC of left VLPFC to right inferior temporal (P = 0.0157, R = 0.5323, AlphaSim corrected) in PD-RBD group. Furthermore, abnormal correlations with zFC values were also found in some cognitive subdomains in PD-RBD group. The study may suggest that in PD-RBD patients, the presence of RBD may be related to the abnormal FC of VLPFC and DLPFC, meanwhile, the abnormal FC of DLPFC and IFG may be related to the mechanisms of cognitive impairment.

Neural Control of REM Sleep and Motor Atonia: Current Perspectives

PURPOSE OF REVIEW

Since the formal discovery of rapid eye movement (REM) sleep in 1953, we have gained a vast amount of knowledge regarding the specific populations of neurons, their connections, and synaptic mechanisms regulating this stage of sleep and its accompanying features. This article discusses REM sleep circuits and their dysfunction, specifically emphasizing recent studies using conditional genetic tools.

RECENT FINDINGS

Sublaterodorsal nucleus (SLD) in the dorsolateral pons, especially the glutamatergic subpopulation in this region (SLDGlut), are shown to be indispensable for REM sleep. These neurons appear to be single REM generators in the rodent brain and may initiate and orchestrate all REM sleep events, including cortical and hippocampal activation and muscle atonia through distinct pathways. However, several cell groups in the brainstem and hypothalamus may influence SLDGlut neuron activity, thereby modulating REM sleep timing, amounts, and architecture. Damage to SLDGlut neurons or their projections involved in muscle atonia leads to REM behavior disorder, whereas the abnormal activation of this pathway during wakefulness may underlie cataplexy in narcolepsy. Despite some opposing views, it has become evident that SLDGlut neurons are the sole generators of REM sleep and its associated characteristics. Further research should prioritize a deeper understanding of their cellular, synaptic, and molecular properties, as well as the mechanisms that trigger their activation during cataplexy and make them susceptible in RBD.

Sex differences in rapid eye movement sleep behavior disorder: A systematic review and meta-analysis

Although rapid eye movement (REM) sleep behavior disorder (RBD) has been widely considered as a male-predominant parasomnia, the existing evidence for the sex difference in the risk of RBD in the general population was conflicting. The present study conducted a systematic review to explore the sex differences in the prevalence, comorbidities, clinical characteristics, and phenoconversion of RBD. One hundred thirty-five eligible studies were identified for the systematic review, and 133 were finally included in the meta-analysis. Males in the general population showed a trend for a higher risk of probable/possible RBD (pRBD), especially among the male older adults (aged ≥60). In the clinical populations, males showed a significantly higher risk of confirmed RBD, but not of pRBD. Among idiopathic RBD (iRBD) patients, males had a significantly earlier age onset of RBD compared with females. Male patients with Parkinson's disease (PD) had a higher risk of comorbid RBD. There was no significant sex difference in the risk of developing neurodegenerative diseases in iRBD patients. Large scale and prospective studies utilizing stringent diagnostic criteria for RBD are recommended to further verify the sex differences in RBD and to investigate the mechanism underlying the sex difference.

Obstructive sleep apnea in Parkinson's disease: A prevalent, clinically relevant and treatable feature

Parkinson's disease (PD) is a chronic neurodegenerative disease characterized by motor and non-motor symptoms, including obstructive sleep apnea (OSA), a common comorbid sleep disorder. The prevalence of OSA in PD is high, and its impact on quality of life, accident risk, and limited treatment options underscores the need for vigilant monitoring and effective interventions. OSA is observed in 20-70% of PD patients, whereas the general population exhibits a lower prevalence ranging from 2 to 14%. These discrepancies in prevalence may be attributed to differences in demographic characteristics, sample sizes with selection bias, and variations in scoring systems for apnea and hypopnea events used across different studies. This review highlights the potential pathogenesis of comorbid OSA in PD and provides an overview of ongoing clinical trials investigating interventions for this condition. Several mechanisms have been implicated in the development of OSA in PD, including intermittent hypoxemia, sleep fragmentation, alterations in the glymphatic system homeostasis, upper airway obstruction, and inflammation. Given the adverse effects of PD comorbid OSA, early intervention measures are crucial. It is imperative to conduct longitudinal studies and clinical trials to elucidate the pathogenesis and develop novel and effective interventions for OSA in PD patients. These efforts aim to delay the progression of PD, enhance patients' quality of life, and alleviate the burden on society and families.

Video polysomnographic analysis of elevated EMG activity and rapid eye movements before abnormal behaviors in REM sleep behavior disorder

The pathogenesis of rapid eye movement (REM) sleep behavior disorder (RBD) is unclear. According to the cortical hypothesis, severe RBD episode (RBDE) occurs when spinal motoneurons are less inhibited and cortical and limbic systems are more active. We made this study to prove the hypothesis for the development of RBDE using video-polysomnography (VPSG). VPSG records of 35 patients with RBD were analyzed. According to severity, RBDEs were classified into three motor events (MEs): ME 1; small movements or jerks, ME 2; proximal movements including violent behavior, and ME 3; axial movements including bed falls. For each ME, we measured the number of MEs preceded or not preceded by both REM sleep without atonia (RWA) and REMs during the 10-s-period immediately before ME onset. In severe RBDE (ME 3), the number of MEs preceded by both RWA and REMs was significantly higher than that of MEs not preceded by both (0.8 vs. 0.2, P = 0.033). This was not the case for mild RBDE (ME 1) and moderate RBDE (ME 2). Our results suggest that both RWA and REMs are associated with the development of severe RBDE.

REM behavior disorder: When Parkinson's disease meets Morpheus

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia characterized by the absence of normal muscle atonia during REM sleep, resulting in excessive motor activity while dreaming. RBD can be classified as isolated which is the strongest clinical marker of prodromal synucleinopathy, or secondary, associated with other neurological diseases, mainly Parkinson's disease (PD) and dementia with Lewy bodies. The diagnosis of RBD must be systematically documented by a video polysomnography in the case of isolated RBD. PD associated with RBD may represent a distinct phenotype compared to PD without RBD, indicating a more severe and widespread synucleinopathy. Clinically, it is associated with poorer motor and cognitive performance, more severe non-motor symptoms, and faster disease progression. Imaging studies have revealed broader brain damage and significant alterations in cerebral metabolism and neurotransmission in PD patients with RBD. The management of RBD involves safety precautions and pharmacotherapy. Safety measures aim to minimize the risk of injury during RBD episodes and include creating a safe sleeping environment and separating the patient from their bed partner if necessary. Pharmacotherapy options include clonazepam and melatonin. Clonazepam must be cautiously prescribed in older patients due to potential side effects.

Probable Parasomnias and Mortality: A Prospective Study in US Men

OBJECTIVE

To examine the association between parasomnias, including rapid eye movement sleep behavior disorder (RBD) and sleep walking (SW), and mortality risk in a large-scale population-based cohort.

METHODS

This prospective cohort study was based on 25,695 participants from the Health Professionals Follow-up Study, a population-based cohort of male health professionals in the United States. Probable SW (pSW) and probable RBD (pRBD) were measured by questions adapted from the Mayo Sleep Questionnaire in 2012. All-cause mortality and cause-specific mortality were ascertained through the national registry, reports by the families, and the postal system from January 1, 2012, through June 30, 2018.

RESULTS

Of the studied population, 223 reported pSW and 2720 reported pRBD. During 6 years of follow-up (2012 to 2018), 4743 mortality cases were documented. The co-occurrence of both probable parasomnias was associated with higher all-cause mortality risk (Ptrend=.008), and the adjusted hazard ratio (HR) of mortality was 1.65 (95% CI, 1.20 to 2.28) compared with participants without either probable parasomnia after adjustment for major lifestyle, sleep, and metabolic risk factors, and chronic diseases. Significant associations were found for mortality attributed to neurodegenerative diseases (adjusted HR for both parasomnias vs none, 4.57; 95% CI, 2.62 to 7.97) and accidents (adjusted HR for both parasomnias vs none, 7.36; 95% CI, 2.95 to 18.4). Having pSW alone was associated with all-cause mortality, and pSW and pRBD were individually associated with mortality attributed to neurodegenerative diseases and accidents too (P<.05 for all).

CONCLUSION

Probable parasomnia was associated with a higher risk of all-cause mortality and mortality attributed to neurodegenerative diseases and accidents.

Sex-dependent neuronal effects of α-synuclein reveal that GABAergic transmission is neuroprotective of sleep-controlling neurons

BACKGROUND

Sleep disorders (SDs) are a symptom of the prodromal phase of neurodegenerative disorders that are mechanistically linked to the protein α-synuclein (α-syn) including Parkinson's disease (PD). SDs during the prodromal phase could result from neurodegeneration induced in state-controlling neurons by accumulation of α-syn predominant early in the disease, and consistent with this, we reported the monomeric form of α-syn (monomeric α-syn; α-synM) caused cell death in the laterodorsal tegmental nucleus (LDT), which controls arousal as well as the sleep and wakefulness state. However, we only examined the male LDT, and since sex is considered a risk factor for the development of α-syn-related diseases including prodromal SDs, the possibility exists of sex-based differences in α-synM effects. Accordingly, we examined the hypothesis that α-synM exerts differential effects on membrane excitability, intracellular calcium, and cell viability in the LDT of females compared to males.

METHODS

Patch clamp electrophysiology, bulk load calcium imaging, and cell death histochemistry were used in LDT brain slices to monitor responses to α-synM and effects of GABA receptor acting agents.

RESULTS

Consistent with our hypothesis, we found differing effects of α-synM on female LDT neurons when compared to male. In females, α-synM induced a decrease in membrane excitability and heightened reductions in intracellular calcium, which were reliant on functional inhibitory acid transmission, as well as decreased the amplitude and frequency of spontaneous excitatory postsynaptic currents (sEPSCs) with a concurrent reduction in action potential firing rate. Cell viability studies showed higher α-synM-mediated neurodegeneration in males compared to females that depended on inhibitory amino acid transmission. Further, presence of GABA receptor agonists was associated with reduced cell death in males.

CONCLUSIONS

When taken together, we conclude that α-synM induces a sex-dependent effect on LDT neurons involving a GABA receptor-mediated mechanism that is neuroprotective. Understanding the potential sex differences in neurodegenerative processes, especially those occurring early in the disease, could enable implementation of sex-based strategies to identify prodromal PD cases, and promote efforts to illuminate new directions for tailored treatment and management of PD.

Sex differences in alpha-synucleinopathies: a systematic review

Background

Past research indicates a higher prevalence, incidence, and severe clinical manifestations of alpha-synucleinopathies in men, leading to a suggestion of neuroprotective properties of female sex hormones (especially estrogen). The potential pathomechanisms of any such effect on alpha-synucleinopathies, however, are far from understood. With that aim, we undertook to systematically review, and to critically assess, contemporary evidence on sex and gender differences in alpha-synucleinopathies using a bench-to-bedside approach.

Methods

In this systematic review, studies investigating sex and gender differences in alpha-synucleinopathies (Rapid Eye Movement (REM) Behavior Disorder (RBD), Parkinson's Disease (PD), Dementia with Lewy Bodies (DLB), Multiple System Atrophy (MSA)) from 2012 to 2022 were identified using electronic database searches of PubMed, Embase and Ovid.

Results

One hundred sixty-two studies were included; 5 RBD, 6 MSA, 20 DLB and 131 PD studies. Overall, there is conclusive evidence to suggest sex-and gender-specific manifestation in demographics, biomarkers, genetics, clinical features, interventions, and quality of life in alpha-synucleinopathies. Only limited data exists on the effects of distinct sex hormones, with majority of studies concentrating on estrogen and its speculated neuroprotective effects.

Conclusion

Future studies disentangling the underlying sex-specific mechanisms of alpha-synucleinopathies are urgently needed in order to enable novel sex-specific therapeutics.

Parkinson's Disease: A Narrative Review on Potential Molecular Mechanisms of Sleep Disturbances, REM Behavior Disorder, and Melatonin

Parkinson's disease (PD) is one of the most common neurodegenerative diseases. There is a wide range of sleep disturbances in patients with PD, such as insomnia and rapid eye movement (REM) sleep behavior disorder (or REM behavior disorder (RBD)). RBD is a sleep disorder in which a patient acts out his/her dreams and includes abnormal behaviors during the REM phase of sleep. On the other hand, melatonin is the principal hormone that is secreted by the pineal gland and significantly modulates the circadian clock and mood state. Furthermore, melatonin has a wide range of regulatory effects and is a safe treatment for sleep disturbances such as RBD in PD. However, the molecular mechanisms of melatonin involved in the treatment or control of RBD are unknown. In this study, we reviewed the pathophysiology of PD and sleep disturbances, including RBD. We also discussed the potential molecular mechanisms of melatonin involved in its therapeutic effect. It was concluded that disruption of crucial neurotransmitter systems that mediate sleep, including norepinephrine, serotonin, dopamine, and GABA, and important neurotransmitter systems that mediate the REM phase, including acetylcholine, serotonin, and norepinephrine, are significantly involved in the induction of sleep disturbances, including RBD in PD. It was also concluded that accumulation of α-synuclein in sleep-related brain regions can disrupt sleep processes and the circadian rhythm. We suggested that new treatment strategies for sleep disturbances in PD may focus on the modulation of α-synuclein aggregation or expression.

A systematic review of dreams and nightmares recall in patients with rapid eye movement sleep behaviour disorder

Rapid eye movement (REM) sleep behaviour disorder is a REM sleep parasomnia characterised by the loss of the physiological muscle atonia during REM sleep, resulting in dream enactment behaviours that may cause injuries to patients or their bed partners. The nocturnal motor episodes seem to respond to the dream contents, which are often vivid and violent. These behavioural and oneiric features make the REM sleep behaviour disorder a potential model to study dreams. This review aims to unify the literature about dream recall in REM sleep behaviour disorder as a privileged approach to study dreams, systematically reviewing studies that applied retrospective and prospective experimental designs to provide a comprehensive overview of qualitative and quantitative aspects of dream recall in this REM sleep parasomnia. The present work highlights that the study of dreaming in REM sleep behaviour disorder is useful to understand unique aspects of this pathology and to explore neurobiological, electrophysiological, and cognitive mechanisms of REM sleep and dreaming.

The Accuracy and Reliability of Sleep Staging and Sleep Biomarkers in Patients with Isolated Rapid Eye Movement Sleep Behavior Disorder

Purpose

This study aimed to establish the diagnostic accuracy of a previously validated sleep staging system in patients with probable isolated REM sleep behavior disorder (iRBD), and to compare physicians' diagnoses of iRBD based on REM sleep without atonia (RSWA) to non-REM hypertonia (NRH), a sleep measure independently associated with Parkinsonian spectrum disorders.

Patients and Methods

Twenty-six patients with a history of dream enactment behavior underwent a diagnostic PSG with simultaneous Sleep Profiler (SP) acquisition at two sites. PSG and SP records were sleep staged, and two sleep neurologists independently diagnosed iRBD based on the presence or absence of polysomnographic identified RSWA. Comparisons for PSG vs SP sleep staging and the qualitative presence or absence of PSG-based RSWA vs automated SP-detected NRH was performed using kappa coefficients (k), positive and negative percent agreements (PPA and NPA), and chi-square tests.

Results

The kappa scores from Sites-1 and -2 for PSG vs SP staging were different for Wake (k=0.82 vs 0.65), N2 (k=0.63 vs 0.72) and REM (k=0.83 vs.0.72). The by-site kappa values for stage N3 increased from 0.72 and 0.37 to 0.88 and 0.74 after PSG records were reedited. The kappa values for between-physician agreement in iRBD diagnoses were fair (k = 0.22). The agreement between each physician's iRBD diagnoses and NRH were also fair (k=0.29 and 0.22). Abnormal NRH agreed with at least one physician's iRBD diagnosis in 83% of the records. The PPA resulting from between-physician iRBD agreement was stronger and the NPA weaker than the values obtained from comparison of each physician's iRBD diagnosis and abnormal NRH.

Conclusion

The potential utility of RSWA and stage N3 as neurodegenerative disorder biomarkers was influenced by between-site variability in visual scoring. The degree to which NRH was associated with iRBD was similar to the between-physician agreement in their diagnosis of iRBD using RSWA.

Management of REM sleep behavior disorder: an American Academy of Sleep Medicine systematic review, meta-analysis, and GRADE assessment

This systematic review provides supporting evidence for a clinical practice guideline for the management of rapid eye movement (REM) sleep behavior disorder in adults and children. The American Academy of Sleep Medicine commissioned a task force of 7 experts in sleep medicine. A systematic review was conducted to identify randomized controlled trials and observational studies that addressed interventions for the management of REM sleep behavior disorder in adults and children. Statistical analyses were performed to determine the clinical significance of critical and important outcomes. Finally, the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) process was used to assess the evidence for making recommendations. The literature search identified 4,690 studies; 148 studies provided data suitable for statistical analyses; evidence for 45 interventions is presented. The task force provided a detailed summary of the evidence assessing the certainty of evidence, the balance of benefits and harms, patient values and preferences, and resource use considerations.

CITATION

Howell M, Avidan AY, Foldvary-Schaefer N, et al. Management of REM sleep behavior disorder: an American Academy of Sleep Medicine systematic review, meta-analysis, and GRADE assessment. J Clin Sleep Med. 2023;19(4):769-810.

A data-driven approach to neuropsychological features in isolated REM behaviour disorder: A latent class analysis

Recent evidence demonstrated that neuropsychological assessment may be considered a valid marker of neurodegeneration in idiopathic REM sleep behaviour disorder (iRBD). However, little is known about the possible neuropsychological heterogeneity within the iRBD population. This retrospective study aimed to identify and describe different neuropsychological phenotypes in iRBD patients by means of a data-driven approach using latent class analysis. A total of 289 iRBD patients underwent a neuropsychological assessment evaluating cognitive domains: global cognition, language, short- and long-term memory, executive functions and visuospatial abilities. The presence of mild cognitive impairment (MCI) was also assessed. Latent class analysis was carried out to identify iRBD subtypes according to neuropsychological scores. The most parsimonious model identified three latent classes. Groups were labelled as follows: Class 2 "severely impaired" (n = 83/289): mean pathological scores in different tests, a high percentage of MCI multiple-domain and impairment in all neuropsychological domains. Class 1 "moderately impaired" (n = 44/289): mean neuropsychological score within the normal value, a high percentage of MCI (high risk to phenoconversion) and great impairment in the visuospatial domain. Class 3 "slightly impaired" (n = 162/289): no deficit worthy of attention except for short- and long-term memory. Our results suggest three different clinical phenotypes within the iRBD population. These findings may be relevant in the future for predicting the clinical trajectories of phenoconversion in iRBD.

[Alternative methods of therapy for comorbid sleep disorders as a method of choice in adult patients with epilepsy]

OBJECTIVE

Systematization and generalization of data from domestic and foreign literature on alternative methods of treatment of sleep disorders in epilepsy.

MATERIAL AND METHODS

The search for data from domestic and foreign literary sources was carried out in the electronic databases Medline (PubMed), Scopus, Web of Science, eLibrary, CyberLeninka, Google Scholar.

RESULTS

The data of modern randomized trials, meta-analyzes on the effectiveness of various non-traditional methods as a method of choice for epilepsy with comorbid sleep disorders have been analyzed.

CONCLUSIONS

Complementary (alternative) treatments have many advantages over the classical pharmacotherapy of sleep disorders in epilepsy, in the form of non-invasiveness, low incidence of side-effects, ease of use, and lack of a dose-dependent effect. Of course, the targets of most of the above methods are not focused and not very specific, and the sample size is too small to obtain impartial and meaningful clinical conclusions, but this once again emphasizes the urgent need for large-scale clinical trials, which is necessary to develop evidence-based treatments for comorbid sleep disorders in epilepsy.

The Association Between Somatic Symptom Disorders and Neurocognitive Disorders: A Systematic Review

OBJECTIVE

Onset of neuropsychiatric symptoms in older adults may represent prodromal manifestations of neurodegenerative disorders. The association between the onset of somatic symptom and related disorders (SSRD) and the subsequent development of neurodegenerative disorders remains unclear. A critical review of studies describing the association between SSRD and neurodegenerative disorders, such as Alzheimer's disease, Parkinson's disease, Frontotemporal dementia, and Lewy body dementia was performed.

OBJECTIVE

To critically review studies describing the association between SSRD and neurodegenerative disorders, such as Alzheimer's disease, Parkinson's disease, Frontotemporal dementia, and Lewy body dementia.

METHODS

A systematic review of Web of Science Core databases was carried out from inception of databases up to May 2021 to identify observational studies pertaining to both SSRD and neurodegenerative disorders. Data was extracted and compiled regarding subjects enrolled, age at onset of the SSRD and at onset of the neurodegenerative disorders, and specific SSRD manifestations and underlying neuropathologies reported.

RESULTS

Thirteen articles were included. Of the 123 identified subjects with SSRD at baseline, 34.1% developed a neurodegenerative disorder, with 80.9% of these being a Lewy body spectrum disorder. The interval between onset of SSRD manifestations and subsequent development of a neurodegenerative disorder was less than 3 years for half of the cases. Of the 1,494 subjects with a neurodegenerative disorder at baseline retrieved, SSRD manifestations were reported in 33.4% of Lewy body spectrum disorders cases. Onset of SSRD manifestations antedated or was concomitant to the diagnosis of the Lewy body spectrum disorder in 65.6% of cases.

CONCLUSION

While limited, current evidence suggests a possible association between late-onset SSRD and the subsequent development of neurodegenerative disorders, notably Lewy body spectrum disorders.

Obstructive sleep apnea may reduce a diagnostic accuracy of video-polysomnography for idiopathic REM sleep behavior disorder

BACKGROUND

Severe obstructive sleep apnea (OSA) in patients with rapid eye movement (REM) sleep behavior disorder (RBD) may result in frequent fragmentation of REM sleep and consequently lead to a false negative diagnosis of RBD on a video-polysomnography (video-PSG). Thus, we determined whether OSA has the negative impact on video-PSG diagnostic accuracy for RBD.

METHODS

Patients with clinically diagnosed idiopathic RBD were included. RBD was confirmed if a video-PSG demonstrated complex motor behavior during REM sleep or REM sleep without atonia (RWA). Motor behavior was measured using the RBD Severity Scale. Cohen's kappa coefficient was calculated for qualitative assessment of RWA. A stepwise logistic regression analysis was performed.

RESULTS

Of a total 254 patients included, a diagnosis of RBD was confirmed by a video-PSG in 221 patients (87.0%). RWA, vocalization, and axial or proximal muscle movements in REM sleep were noted in 86.6%, 58.3%, and 35.9%, respectively. A video-PSG diagnosis of RBD was less likely associated with severe OSA (odds ratio [OR] 0.284, p = 0.010) and moderate OSA (OR 0.404, p = 0.071) whereas was more likely associated with longer REM sleep time (OR 1.036, p < 0.001). In 43 patients who underwent a continuous positive airway pressure (CPAP) titration study, a diagnosis of RBD was more common on a CPAP titration study (88.4%) than on a first video-PSG (65.1%) (p = 0.013). Twelve (27.9%) of 43 CPAP patients were diagnosed with RBD according only to CPAP titration study.

CONCLUSIONS

OSA that requires CPAP may reduce a diagnostic accuracy for RBD by a video-PSG. False negative results were probably due to frequent electromyographic artifacts and/or severe sleep disruption from apneic events during REM sleep.

Treatment with the novel TAAR1 agonist ulotaront is associated with reductions in quantitative polysomnographic REM sleep without atonia in healthy human subjects: Results of a post-hoc analysis

BACKGROUND

Isolated REM sleep behavior disorder (RBD) is a potentially injurious parasomnia lacking an established treatment. Ulotaront is a trace amine-associated receptor 1 (TAAR1) agonist with 5-HT_1A receptor agonist activity that has demonstrated efficacy in patients with schizophrenia. In a single dose challenge study in humans, ulotaront 50 mg demonstrated significant REM suppressant effects. We now report post-hoc exploratory analyses designed to evaluate the effect of ulotaront on quantitative REM sleep without atonia (RSWA).

METHODS

Young healthy adult men (ages 19-35) were randomized to double-blind, cross-over treatment (after 7-day wash-out) with single doses of ulotaront (50 mg or 10 mg) versus placebo followed by polysomnography (PSG) on each of the nights following treatment. Quantitative RSWA was analyzed in a blinded fashion using established visual and automated methods.

RESULTS

Subjects received 50 mg (n = 11) or 10 mg (n = 9) of ulotaront. Treatment with ulotaront 50 mg was associated with lower RSWA (p < 0.05), with greatest RSWA reduction (vs. placebo) observed in subjects with RSWA levels above the mean on the baseline night. RSWA levels were similar between treatment with ulotaront 10 mg and placebo.

CONCLUSION

Treatment with ulotaront 50 mg (but not 10 mg) was associated with reductions in RSWA levels in healthy subjects, especially in subjects with higher baseline RSWA levels, providing proof-of-concept for ulotaront efficacy in reducing RSWA levels. However, whether ulotaront might have efficacy as a treatment for human RBD awaits double-blind trials with ulotaront in clinical RBD populations.

Parasomnias during trans-meridian and long-distance travel: Critical literature review and clinical practice recommendations

Parasomnias are undesirable events that occur during sleep. They can be classified into rapid eye movement parasomnias and non-rapid eye movement parasomnias. Those who experience parasomnias may be anxious about travel for many reasons, including the occurrence of unwanted events during the trip, increased exposure to environmental trigger factors, and the propensity for harm to occur due to unfamiliar surroundings while travelling. There is a paucity of literature examining this area. This review summarizes the relevant literature and the clinical experience of the authors to compile clinical practice recommendations. The clinical features of parasomnias and how they relate to trans-meridian and long-distance travel are described. Triggers for non-rapid eye movement parasomnias, particularly the use of sedative hypnotic drugs, alcohol, drug withdrawal, sleep deprivation, emotional stress and environmental stimulations, are described. Management of parasomnias whilst travelling is reviewed, with a particular focus on trigger minimalization. The role for clonazepam and melatonin is outlined. At the pre-travel health consultation, the physician is strongly advised to screen the traveller for co-morbid sleep conditions, which exacerbate parasomnias. Areas for further research are explored, including the extent to which these sleep disorders impact on the travel experience.

Isolated dream‐enactment behaviours as a prodromal hallmark of rapid eye movement sleep behaviour disorder

Recurrent dream-enactment behaviours (DEB) and rapid eye movement (REM) sleep without atonia (RSWA) are two diagnostic hallmarks of REM sleep behaviour disorder (RBD), a specific prodrome of α-synucleinopathy. Whilst isolated RSWA (without DEB) was suggested as a prodrome of RBD, the implication of 'isolated' recurrent DEB remains under-investigated. In this cross-sectional study, we sought to investigate neurodegenerative markers amongst the first-degree relatives (FDRs, aged >40 years) of patients with RBD who underwent clinical assessment for DEB, neurodegenerative markers, and video-polysomnography assessment. Isolated recurrent DEB was defined as: (i) three or more episodes of DEB, (ii) had a DEB episode in the past 1 year, and (iii) subthreshold RSWA. We identified 29 FDRs (mean [SD] age 53.4 [8.3] years, 55.2% male) with isolated recurrent DEB and 98 age and sex-matched FDRs as controls. Isolated DEB was associated with nightmare (27.6% versus 11.2%, p = 0.02), and the DEB group had a higher rate of current smoking (27.6% versus 3.1%, p = 0.006), type 2 diabetes mellitus (24.1% versus 10.2%, p = 0.003), anxiety disorder (24.1% versus 11.2%, p = 0.02), and constipation (hard lump of stool, 31.0% versus 7.1%, p < 0.001) than the control group. The present findings revealed that family relatives of patients with RBD with isolated recurrent DEB have increased risk of RBD and neurodegenerative features, which adds to the emerging data that isolated DEB is a prodromal feature of RBD and α-synucleinopathy neurodegeneration.

A review of automated sleep disorder detection

Automated sleep disorder detection is challenging because physiological symptoms can vary widely. These variations make it difficult to create effective sleep disorder detection models which support hu-man experts during diagnosis and treatment monitoring. From 2010 to 2021, authors of 95 scientific papers have taken up the challenge of automating sleep disorder detection. This paper provides an expert review of this work. We investigated whether digital technology and Artificial Intelligence (AI) can provide automated diagnosis support for sleep disorders. We followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines during the content discovery phase. We compared the performance of proposed sleep disorder detection methods, involving differ-ent datasets or signals. During the review, we found eight sleep disorders, of which sleep apnea and insomnia were the most studied. These disorders can be diagnosed using several kinds of biomedical signals, such as Electrocardiogram (ECG), Polysomnography (PSG), Electroencephalogram (EEG), Electromyogram (EMG), and snore sound. Subsequently, we established areas of commonality and distinctiveness. Common to all reviewed papers was that AI models were trained and tested with labelled physiological signals. Looking deeper, we discovered that 24 distinct algorithms were used for the detection task. The nature of these algorithms evolved, before 2017 only traditional Machine Learning (ML) was used. From 2018 onward, both ML and Deep Learning (DL) methods were used for sleep disorder detection. The strong emergence of DL algorithms has considerable implications for future detection systems because these algorithms demand significantly more data for training and testing when compared with ML. Based on our review results, we suggest that both type and amount of labelled data is crucial for the design of future sleep disorder detection systems because this will steer the choice of AI algorithm which establishes the desired decision support. As a guiding principle, more labelled data will help to represent the variations in symptoms. DL algorithms can extract information from these larger data quantities more effectively, therefore; we predict that the role of these algorithms will continue to expand.

Dreaming in Parasomnias: REM Sleep Behavior Disorder as a Model

Sleep parasomnias have drawn the interest of sleep experts because they represent a valuable window to directly monitor dream activity and sleep mentation associated with nocturnal events. Indeed, parasomnias and their manifestations are helpful in investigating dream activity and features, overcoming methodological limits that affect dream study. Specifically, REM sleep Behavior Disorder (RBD) is a parasomnia characterized by enacted dream episodes during Rapid Eye Movements (REM) sleep, caused by the loss of physiological atonia. Patients suffering from RBD report a peculiar oneiric activity associated with motor episodes characterized by high Dream Recall Frequency (DRF) and vivid dreams. Additionally, isolated RBD (iRBD) represents a prodromal stage of neurodegeneration preceding the development of α-synucleinopathies. This narrative review aims to combine evidence describing dream activity in RBD and similarities and differences with other NREM parasomnias. Moreover, a special focus has been reserved for those conditions in which RBD is associated with α-synucleinopathies to clarify the potential role of dreams in neurodegenerative processes.

Drugs Used in Parasomnia

Parasomnias, especially disorders of arousal during childhood, are often relatively benign and transitory and do not usually require a pharmacologic therapy. A relevant aspect in both nonrapid eye movement and rapid eye movement parasomnia treatment is to prevent sleep-related injuries by maintaining a safe environment. Physicians should always evaluate the possible presence of favoring and precipitating factors (sleep disorders and drugs). A pharmacologic treatment may be indicated in case of frequent, troublesome, or particularly dangerous events. The aim of this article is to review current available evidence on pharmacologic treatment of different forms of parasomnia.

Sleep Dysfunction in Movement Disorders: a Window to the Disease Biology

PURPOSE OF REVIEW

To comprehensively summarize the sleep pathologies associated with movement disorders, focusing on neurodegenerative diseases.

RECENT FINDINGS

Mounting evidence has further implicated both sleep and circadian disruption in the pathophysiology of many movement disorders. In particular, recent data illuminate the mechanisms by which poor sleep quality and circadian dysfunction can exacerbate neurodegeneration. In addition, anti-IgLON5 disease is a recently described autoimmune disease with various symptoms that can feature prominent sleep disruption and parasomnia. Many movement disorders are associated with sleep and circadian rhythm disruption. Motor symptoms can cause sleep fragmentation, resulting in insomnia and excessive daytime sleepiness. Many neurodegenerative movement disorders involve brainstem pathology in regions close to or affecting nuclei that regulate sleep and wake. Further, commonly used movement medications may exacerbate sleep concerns. Providers should screen for and address these sleep symptoms to improve function and quality of life for patients and caregivers.