Quantifying the risk of neurodegenerative disease in idiopathic REM sleep behavior disorder

Gait Analysis with Wearable Sensors in Isolated REM Sleep Behavior Disorder Associated with Phenoconversion: An Explorative Study

Background

Gait disturbance is a vital characteristic of motor manifestation in α- synucleinopathies, especially Parkinson's disease. Subtle gait alterations are present in isolated rapid eye movement sleep behavior disorder (iRBD) patients before phenoconversion; it is yet unclear, if gait analysis may predict phenoconversion.

Objective

To investigate subtle gait alterations and explore whether gait analysis using wearable sensors is associated with phenoconversion of iRBD to α-synucleinopathies.

Methods

Thirty-one polysomnography-confirmed iRBD patients and 33 healthy controls (HCs) were enrolled at baseline. All participants walked for a minute while wearing 6 inertial sensors on bilateral wrists, ankles, and the trunk (sternal and lumbar region). Three conditions were tested: (i) normal walking, (ii) fast walking, and (iii) dual-task walking.

Results

Decreased arm range of motion and increased gait variation (stride length, stride time and stride velocity) discriminate converters from HCs at baseline. After an average of 5.40 years of follow-up, 10 patients converted to neurodegenerative diseases (converters). Cox regression analysis showed higher value of stride length asymmetry under normal walking condition to be associated with an early conversion of iRBD to α- synucleinopathies (adjusted HR 4.468, 95% CI 1.088- 18.349, p = 0.038).

Conclusions

Stride length asymmetry is associated with progression to α- synucleinopathies in patients with iRBD. Gait analysis with wearable sensors may be useful for screening, monitoring, and risk stratification for disease-modifying therapy trials in patients with iRBD.

Sleep disorders as both risk factors for, and a consequence of, stroke: A narrative review

BACKGROUND AND PURPOSE

Sleep disorders are increasingly implicated as risk factors for stroke, as well as a determinant of stroke outcome. They can also occur secondary to the stroke itself. In this review, we describe the variety of different sleep disorders associated with stroke and analyze their effect on stroke risk and outcome.

METHODS

A search term-based literature review ("sleep," "insomnia," "narcolepsy," "restless legs syndrome," "periodic limb movements during sleep," "excessive daytime sleepiness" AND "stroke" OR "cerebrovascular" in PubMed; "stroke" and "sleep" in ClinicalTrials.gov) was performed. English articles from 1990 to March 2023 were considered.

RESULTS

Increasing evidence suggests that sleep disorders are risk factors for stroke. In addition, sleep disturbance has been reported in half of all stroke sufferers; specifically, an increase is not only sleep-related breathing disorders but also periodic limb movements during sleep, narcolepsy, rapid eye movement (REM) sleep behavior disorder, insomnia, sleep duration, and circadian rhythm sleep-wake disorders. Poststroke sleep disturbance has been associated with worse outcome.

CONCLUSION

Sleep disorders are risk factors for stroke and associated with worse stroke outcome. They are also a common consequence of stroke. Recent guidelines suggest screening for sleep disorders after stroke. It is possible that treatment of sleep disorders could both reduce stroke risk and improve stroke outcome, although further data from clinical trials are required.

Genetic associations between Rapid Eye Movement (REM) sleep behavior disorder and cardiovascular diseases

BACKGROUND

Previous studies revealed that sleep disorders are potential risk factors for cardiovascular diseases, such as obstructive sleep apnea and rapid eye movement (REM) sleep behavior disorder (RBD). However, the causal associations between RBD and cardiovascular diseases remained unknown.

MATERIALS AND METHODS

We used the latest and largest summary-level genome-wide association studies of RBD, stroke and its subtypes, coronary artery disease (CAD), myocardial infarction (MI), and heart failure (HF) to select genetic variants as the instrumental variables. Mendelian randomization (MR) analysis was performed to test the causal associations between RBD and the cardiovascular diseases above. Inverse variance weighted method was used as the main analysis.

RESULTS

After multiple comparisons, genetically predicted RBD was significantly associated with the risk of HF [odds ratio (OR) = 1.033, 95% CI 1.013-1.052, p = 0.001]. Leave-one-out analysis further supported the robustness of the causal association. Furthermore, we identified a suggestive association between genetically predicted MI and RBD (OR = 0.716, 95% CI 0.546-0.940, p = 0.016). However, in our study no associations were identified of RBD with CAD or stroke and its subtypes.

CONCLUSION

Our study highlighted the potential associations between RBD and cardiovascular diseases at genetic level, including HF and MI. More studies were required to clarify the biological mechanisms involved the associations.

Microglial Activation and Progression of Nigrostriatal Dysfunction in Isolated REM Sleep Behavior Disorder

BACKGROUND

Using 11 C-(R)-PK11195-PET, we found increased microglia activation in isolated REM sleep behavior disorder (iRBD) patients. Their role remains to be clarified.

OBJECTIVES

The objective is to assess relationships between activated microglia and progression of nigrostriatal dysfunction in iRBD.

METHODS

Fifteen iRBD patients previously scanned with 11 C-(R)-PK11195 and 18 F-DOPA-PET underwent repeat 18 F-DOPA-PET after 3 years. 18 F-DOPA Ki changes from baseline were evaluated with volumes-of-interest and voxel-based analyses.

RESULTS

Significant 18 F-DOPA Ki reductions were found in putamen and caudate. Reductions were larger and more widespread in patients with increased nigral microglia activation at baseline. Left nigral 11 C-(R)-PK11195 binding at baseline was a predictor of 18 F-DOPA Ki reduction in left caudate (coef = -0.0426, P = 0.016).

CONCLUSIONS

Subjects with increased baseline 11 C-(R)-PK11195 binding have greater changes in nigrostriatal function, suggesting a detrimental rather than protective effect of microglial activation. Alternatively, both phenomena occur in patients with prominent nigrostriatal dysfunction without a causative link. The clinical and therapeutic implications of these findings need further elucidation. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Spoken Language Alterations can Predict Phenoconversion in Isolated Rapid Eye Movement Sleep Behavior Disorder: A Multicenter Study

OBJECTIVE

This study assessed the relationship between speech and language impairment and outcome in a multicenter cohort of isolated/idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD).

METHODS

Patients with iRBD from 7 centers speaking Czech, English, German, French, and Italian languages underwent a detailed speech assessment at baseline. Story-tale narratives were transcribed and linguistically annotated using fully automated methods based on automatic speech recognition and natural language processing algorithms, leading to the 3 distinctive linguistic and 2 acoustic patterns of language deterioration and associated composite indexes of their overall severity. Patients were then prospectively followed and received assessments for parkinsonism or dementia during follow-up. The Cox proportional hazard was performed to evaluate the predictive value of language patterns for phenoconversion over a follow-up period of 5 years.

RESULTS

Of 180 patients free of parkinsonism or dementia, 156 provided follow-up information. After a mean follow-up of 2.7 years, 42 (26.9%) patients developed neurodegenerative disease. Patients with higher severity of linguistic abnormalities (hazard ratio [HR = 2.35]) and acoustic abnormalities (HR = 1.92) were more likely to develop a defined neurodegenerative disease, with converters having lower content richness (HR = 1.74), slower articulation rate (HR = 1.58), and prolonged pauses (HR = 1.46). Dementia-first (n = 16) and parkinsonism-first with mild cognitive impairment (n = 9) converters had higher severity of linguistic abnormalities than parkinsonism-first with normal cognition converters (n = 17).

INTERPRETATION

Automated language analysis might provide a predictor of phenoconversion from iRBD into synucleinopathy subtypes with cognitive impairment, and thus can be used to stratify patients for neuroprotective trials. ANN NEUROL 2024;95:530-543.

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.

Animal Approaches to Studying Risk Factors for Parkinson's Disease: A Narrative Review

Despite recent efforts to search for biomarkers for the pre-symptomatic diagnosis of Parkinson's disease (PD), the presence of risk factors, prodromal signs, and family history still support the classification of individuals at risk for this disease. Human epidemiological studies are useful in this search but fail to provide causality. The study of well-known risk factors for PD in animal models can help elucidate mechanisms related to the disease's etiology and contribute to future prevention or treatment approaches. This narrative review aims to discuss animal studies that investigated four of the main risk factors and/or prodromal signs related to PD: advanced age, male sex, sleep alterations, and depression. Different databases were used to search the studies, which were included based on their relevance to the topic. Although still in a reduced number, such studies are of great relevance in the search for evidence that leads to a possible early diagnosis and improvements in methods of prevention and treatment.

Knowledge mapping of prodromal Parkinson's disease: A bibliometric review and analysis (2000-2023)

The prodromal period of Parkinson's disease (PD) is currently a hot topic in PD research. However, no bibliometric analysis has been conducted in this research field. This study aimed to provide a comprehensive overview of the status, hotspots, and trends in the prodromal period of PD using bibliometrics. CiteSpace and visualization of similarities viewer were used to analyze articles and reviews on the prodromal period of PD in the Web of Science Core Collection (WoSCC) database. We analyzed the data on countries, institutions, journals, authors, keywords, and cited references. In total, 909 articles from 65 countries, including the United States (n = 265, 29.15%) and Germany (n = 174, 19.14%), were included. The number of articles and reviews related to the prodromal period of PD has increased yearly. The University of Tubingen (n = 45, 4.95%), McGill University (n = 33, 3.63%), and University of London (n = 33, 3.63%) were the research institutions with the most published studies. Movement Disorders is the journal with the largest number of published papers (n = 98, 10.8%) and the most cited publications (co-citation = 7035). These publications are from 4681 authors, with Berg (n = 49, 5.39%) and Postuma (n = 40, 4.40%) publishing the most publications, and Postuma's study (n = 1206) having the most citations. Studying the nonmotor symptoms of PD precursors is a major topic in this research field. This is the first bibliometric study to comprehensively summarize the research trends and developments in the prodromal period of PD. This information identifies recent research frontiers and hotspots and provides a reference for scholars studying the prodromal period of PD.

Characterization of de novo Dementia with Lewy Body with different duration of rapid eye movement sleep behavior disorder

BACKGROUND

Cognitive disorder, parkinsonism, autonomic dysfunction (AuD) and rapid eye movement sleep behavior disorder (RBD) can occur prior to or simultaneously with Dementia with Lewy Body (DLB) onset. RBD is generally linked with progressive neurodegenerative traits. However, associations between RBD with DLB, RBD without DLB, and RBD duration effects on DLB symptoms remain unclear.

OBJECTIVES

To examine DLB symptom frequency and subtypes in RBD, and explore the effects of different RBD onset times on symptoms in de novo DLB patients.

METHODS

In this multicenter investigation, we consecutively recruited 271 de novo DLB patients. All had standardized clinical and comprehensive neuropsychological evaluations. Subgroup analyses, performed based on the duration of RBD confirmed by polysomnography before the DLB diagnosis, we compared the proportion of patients with cognitive impairment, parkinsonism, and AuD features between groups.

RESULTS

Parkinsonism and AuD incidences were significantly elevated in DLB patients with RBD when compared with patients without RBD. Subgroup analyses indicated no significant differences in parkinsonism between DLB patients who developed RBD ≥10 years prior to the DLB diagnosis and DLB patients without RBD. The incidence of non-tremor-predominant parkinsonism and AuD was significantly higher in DLB patients whose RBD duration before the DLB diagnosis was <10 years when compared with DLB patients without RBD.

CONCLUSIONS

We identified significant symptom and phenotypic variability between DLB patients with and without RBD. Also, different RBD duration effects before the DLB diagnosis had a significant impact on symptomatic phenotypes, suggesting the existence of a slowly progressive DLB neurodegenerative subtype.

Cerebrospinal-fluid biomarkers for predicting phenoconversion in patients with isolated rapid-eye movement sleep behavior disorder

STUDY OBJECTIVES

Patients with isolated rapid-eye-movement sleep behavior disorder (iRBD) have an increased risk of developing neurodegenerative diseases. This study assessed cerebrospinal-fluid (CSF) biomarkers of neurodegeneration and blood-brain barrier (BBB) alteration in patients with iRBD compared to controls and ascertain whether these biomarkers may predict phenoconversion to alpha-synucleinopathies (Parkinson's Disease (PD), Dementia with Lewy bodies (DLB), Multiple System Atrophy (MSA)).

METHODS

Patients and controls underwent between 2012 and 2016 a neurological assessment, a lumbar puncture for CSF biomarker analysis (β-amyloid42 - Aβ42; total-tau, and phosphorylated tau), and BBB alteration (CSF/serum albumin ratio). All patients with iRBD were followed until 2021 and then classified into patients who converted to alpha-synucleinopathies (iRBD converters, cRBD) or not (iRBD non-converters, ncRBD).

RESULTS

Thirty-four patients with iRBD (mean age 67.12 ± 8.14) and 33 controls (mean age 64.97 ± 8.91) were included. At follow-up (7.63 ± 3.40 years), eight patients were ncRBD and 33 patients were cRBD: eleven converted to PD, 10 to DLB, and two to MSA. Patients with iRBD showed lower CSF Aβ42 levels and higher CSF/serum albumin ratio than controls. Cox regression analysis showed that the phenoconversion rate increases with higher motor impairment (hazard ratio [HR] = 1.23, p = 0.032). CSF Aβ42 levels predicted phenoconversion to DLB (HR = 0.67, p = 0.038) and BBB alteration predicted phenoconversion to PD (HR = 1.20, p = 0.038).

DISCUSSION

This study showed that low CSF Aβ42 levels and high BBB alteration may predict the phenoconversion to DLB and PD in patients with iRBD, respectively. These findings highlight the possibility to discriminate phenoconversion in iRBD patients through CSF biomarkers; however, further studies are needed.

Heart rate variability during sleep in synucleinopathies: a review

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

Which factors affect phenoconversion in isolated rapid eye movement sleep behavior disorder?

AIM

Isolated REM sleep behavior disorder (IRBD) is characterized by loss of the normal atonia of REM sleep. Patients with IRBD are at substantial risk of developing the synuclein-related neurodegenerative diseases (NDD). Few predictors of phenoconversion (from IRBD to NDD) have been identified such as age >65 years, hyposmia, constipation, elevated Epworth sleepiness scale (ESS). We aimed to detect rate and risk factors of phenoconversion.

METHOD

The study designed as retrospectively. NDD was developed in 18 (27.27%) patients while NDD wasn't developed in 48 (72.73%) patients after ten years. The data of the first visit (age, gender, hyposmia, constipation, ESS, comorbidities, physical/neurological examinations, laboratory, and polysomnography) were compared between NDD (n:18) and IRBD (46) groups. The statistical program IBM SPSS Statistics Version 20.0 was used for all analyzes. The threshold for statistical significance for each test was set at 0.05.

RESULTS

Although, most first-visit data (age, gender, hyposmia, constipation, ESS, laboratory, polysomnography) were not different between NDD (n:18) and IRBD (n:48) groups, diabetes mellitus (DM) frequency (p:0.021), mean duration of DM (0.027), chest circumference (p:0.017), and hip circumference (p:0.045) were found higher in NDD than IRBD. If the risk of phenoconversion calculated by logistic regression analysis was different only in terms of DM frequency (p:0.030) [odds ratio: 4.909 (1.17-20.19)].

CONCLUSION

The present study showed that the phenoconversion rate for ten years is 27.27%, and IRBD patients with diabetes mellitus increase the phenoconversion risk nearly five times.

Predicting neurodegeneration from sleep related biofluid changes

Sleep-wake disturbances are common in neurodegenerative diseases and may occur years before the clinical diagnosis, potentially either representing an early stage of the disease itself or acting as a pathophysiological driver. Therefore, discovering biomarkers that identify individuals with sleep-wake disturbances who are at risk of developing neurodegenerative diseases will allow early diagnosis and intervention. Given the association between sleep and neurodegeneration, the most frequently analyzed fluid biomarkers in people with sleep-wake disturbances to date include those directly associated with neurodegeneration itself, such as neurofilament light chain, phosphorylated tau, amyloid-beta and alpha-synuclein. Abnormalities in these biomarkers in patients with sleep-wake disturbances are considered as evidence of an underlying neurodegenerative process. Levels of hormonal sleep-related biomarkers such as melatonin, cortisol and orexin are often abnormal in patients with clinical neurodegenerative diseases, but their relationships with the more standard neurodegenerative biomarkers remain unclear. Similarly, it is unclear whether other chronobiological/circadian biomarkers, such as disrupted clock gene expression, are causal factors or a consequence of neurodegeneration. Current data would suggest that a combination of fluid biomarkers may identify sleep-wake disturbances that are most predictive for the risk of developing neurodegenerative disease with more optimal sensitivity and specificity.

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.

Peripheral α-synuclein isoforms are potential biomarkers for diagnosis and prognosis of isolated REM sleep behavior disorder

INTRODUCTION

Isolated REM sleep behavior disorder (IRBD) represents an early manifestation of the synucleinopathies Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Aggregation of abnormal α-synuclein and its increased expression in the brain is crucial in the development of the synucleinopathies. Whereas α-synuclein gene (SNCA) transcripts are overexpressed in brain, a concomitant reduction occurs in blood of DLB patients. We assessed whether this decrease is also detectable in IRBD.

METHODS

108 IRBD patients and 149 controls were included of which 29 IRBD and 32 control cases were available for expression studies. Expression of SNCAtv1, SNCAtv2, SNCAtv3 and SNCA126 isoforms, and GBA were determined by real-time PCR. Genotype distribution of SNCA SNPs, rs356219 and rs2736990, and correlation with SNCA expression was analyzed.

RESULTS

Expression of all SNCA transcripts was reduced in IRBD blood whereas GBA expression did not change. SNCAtv3 expression correlated inversely with IRBD duration, being lower in patients with longer follow-up. Rs356219-AA genotype frequency was increased in IRBD patients who later developed PD and DLB. Rs2736990-CC frequency was increased among IRBD cases who remained disease-free. No correlation was observed between rs356219 and rs2736990 genotypes and SNCA transcript levels.

CONCLUSION

SNCA transcript expression is decreased in blood in IRBD, and levels decrease with IRBD duration. Our findings indicate that changes in SNCA expression occur in the earliest stages of the synucleinopathies before motor and cognitive symptoms become apparent.

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.

Dynamic networks of cortico-muscular interactions in sleep and neurodegenerative disorders

The brain plays central role in regulating physiological systems, including the skeleto-muscular and locomotor system. Studies of cortico-muscular coordination have primarily focused on associations between movement tasks and dynamics of specific brain waves. However, the brain-muscle functional networks of synchronous coordination among brain waves and muscle activity rhythms that underlie locomotor control remain unknown. Here we address the following fundamental questions: what are the structure and dynamics of cortico-muscular networks; whether specific brain waves are main network mediators in locomotor control; how the hierarchical network organization relates to distinct physiological states under autonomic regulation such as wake, sleep, sleep stages; and how network dynamics are altered with neurodegenerative disorders. We study the interactions between all physiologically relevant brain waves across cortical locations with distinct rhythms in leg and chin muscle activity in healthy and Parkinson's disease (PD) subjects. Utilizing Network Physiology framework and time delay stability approach, we find that 1) each physiological state is characterized by a unique network of cortico-muscular interactions with specific hierarchical organization and profile of links strength; 2) particular brain waves play role as main mediators in cortico-muscular interactions during each state; 3) PD leads to muscle-specific breakdown of cortico-muscular networks, altering the sleep-stage stratification pattern in network connectivity and links strength. In healthy subjects cortico-muscular networks exhibit a pronounced stratification with stronger links during wake and light sleep, and weaker links during REM and deep sleep. In contrast, network interactions reorganize in PD with decline in connectivity and links strength during wake and non-REM sleep, and increase during REM, leading to markedly different stratification with gradual decline in network links strength from wake to REM, light and deep sleep. Further, we find that wake and sleep stages are characterized by specific links strength profiles, which are altered with PD, indicating disruption in the synchronous activity and network communication among brain waves and muscle rhythms. Our findings demonstrate the presence of previously unrecognized functional networks and basic principles of brain control of locomotion, with potential clinical implications for novel network-based biomarkers for early detection of Parkinson's and neurodegenerative disorders, movement, and sleep disorders.

Metagenomics of the Gut Microbiome in Parkinson's Disease: Prodromal Changes

OBJECTIVE

Prior studies on the gut microbiome in Parkinson's disease (PD) have yielded conflicting results, and few studies have focused on prodromal (premotor) PD or used shotgun metagenomic profiling to assess microbial functional potential. We conducted a nested case-control study within 2 large epidemiological cohorts to examine the role of the gut microbiome in PD.

METHODS

We profiled the fecal metagenomes of 420 participants in the Nurses' Health Study and the Health Professionals Follow-up Study with recent onset PD (N = 75), with features of prodromal PD (N = 101), controls with constipation (N = 113), and healthy controls (N = 131) to identify microbial taxonomic and functional features associated with PD and features suggestive of prodromal PD. Omnibus and feature-wise analyses identified bacterial species and pathways associated with prodromal and recently onset PD.

RESULTS

We observed depletion of several strict anaerobes associated with reduced inflammation among participants with PD or features of prodromal PD. A microbiome-based classifier had moderate accuracy (area under the curve [AUC] = 0.76 for species and 0.74 for pathways) to discriminate between recently onset PD cases and controls. These taxonomic shifts corresponded with functional shifts indicative of carbohydrate source preference. Similar, but less marked, changes were observed in participants with features of prodromal PD, in both microbial features and functions.

INTERPRETATION

PD and features of prodromal PD were associated with similar changes in the gut microbiome. These findings suggest that changes in the microbiome could represent novel biomarkers for the earliest phases of PD. ANN NEUROL 2023;94:486-501.

Pharmacological interventions targeting α-synuclein aggregation triggered REM sleep behavior disorder and early development of Parkinson's disease

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia characterized by elevated motor behaviors and dream enactments in REM sleep, often preceding the diagnosis of Parkinson's disease (PD). As RBD could serve as a biomarker for early PD developments, pharmacological interventions targeting α-synuclein aggregation triggered RBD could be applied toward early PD progression. However, robust therapeutic guidelines toward PD-induced RBD are lacking, owing in part to a historical paucity of effective treatments and trials. We reviewed the bidirectional links between α-synuclein neurodegeneration, progressive sleep disorders, and RBD. We highlighted the correlation between RBD development, α-synuclein aggregation, and neuronal apoptosis in key brainstem regions involved in REM sleep atonia maintenance. The current pharmacological intervention strategies targeting RBD and their effects on progressive PD are discussed, as well as current treatments for progressive neurodegeneration and their effects on RBD. We also evaluated emerging and potential pharmacological solutions to sleep disorders and developing synucleinopathies. This review provides insights into the mechanisms and therapeutic targets underlying RBD and PD, and explores bidirectional treatment effects for both diseases, underscoring the need for further research in this area.

Magnetic susceptibility changes in the brainstem reflect REM sleep without atonia severity in isolated REM sleep behavior disorder

REM sleep without atonia (RWA) is the hallmark of isolated REM sleep behavior disorder (iRBD) and is caused by neurodegeneration of brainstem structures. Previously, quantitative susceptibility mapping (QSM) was shown to detect microstructural tissue changes in neurodegenerative diseases. The goal of the study was to compare brainstem magnetic susceptibility (MS) in iRBD and controls using the voxel-based QSM approach and to examine the association between brainstem MS and severity of RWA in iRBD. Sixty iRBD patients and 41 healthy controls were included in the study. Phasic, tonic, mixed RWA and SINBAR score was quantified. QSM maps were reconstructed with QSMbox software from a multi-gradient-echo sequence acquired at 3T MRI system and normalized using a custom T1 template. Voxel-based analysis with age and gender as covariates was performed using a two-sample t-test model for between-group comparison and using a linear regression model for association with the RWA parameters. Statistical maps were generated using threshold free cluster enhancement with p-value p < 0.05, corrected for family wise error. Compared to controls, the iRBD group had higher MS in bilateral substantia nigra (SN), red nucleus and the ventral tegmental area. MS positively correlated with iRBD duration in the right pedunculotegmental nucleus and white matter of caudal mesencephalic and pontine tegmentum and with phasic RWA in bilateral SN. QSM was able to detect MS abnormalities in several brainstem structures in iRBD. Association of MS levels in the brainstem with the intensity of RWA suggests that increased iron content in SN is related to RWA severity.

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.

Circadian disruption and sleep disorders in neurodegeneration

Disruptions of circadian rhythms and sleep cycles are common among neurodegenerative diseases and can occur at multiple levels. Accumulating evidence reveals a bidirectional relationship between disruptions of circadian rhythms and sleep cycles and neurodegenerative diseases. Circadian disruption and sleep disorders aggravate neurodegeneration and neurodegenerative diseases can in turn disrupt circadian rhythms and sleep. Importantly, circadian disruption and various sleep disorders can increase the risk of neurodegenerative diseases. Thus, harnessing the circadian biology findings from preclinical and translational research in neurodegenerative diseases is of importance for reducing risk of neurodegeneration and improving symptoms and quality of life of individuals with neurodegenerative disorders via approaches that normalize circadian in the context of precision medicine. In this review, we discuss the implications of circadian disruption and sleep disorders in neurodegenerative diseases by summarizing evidence from both human and animal studies, focusing on the bidirectional links of sleep and circadian rhythms with prevalent forms of neurodegeneration. These findings provide valuable insights into the pathogenesis of neurodegenerative diseases and suggest a promising role of circadian-based interventions.

How should future clinical trials be designed in the search for disease-modifying therapies for Parkinson's disease?

INTRODUCTION

Although there has been substantial progress in research and innovations in symptomatic treatments, similar success has not been achieved in disease-modifying therapy (DMT) for Parkinson's disease (PD). Considering the enormous motor, psychosocial and financial burden associated with PD, safe and effective DMT is of paramount importance.

AREAS COVERED

One of the reasons for the lack of progress in DMT for PD is poor or inappropriate design of clinical trials. In the first part of the article, the authors focus on the plausible reasons why the previous trials have failed and in the latter part, they provide their perspectives on future DMT trials.

EXPERT OPINION

There are several potential reasons why previous trials have failed, including broad clinical and etiopathogenic heterogeneity of PD, poor definition and documentation of target engagement, lack of appropriate biomarkers and outcome measures, and short duration of follow-up. To address these deficiencies, future trials may consider- (i) a more customized approach to select the most suitable participants and therapeutic approaches, (ii) explore combination therapies that would target multiple pathogenetic mechanisms, and (iii) moving beyond targeting only motor symptoms to also assessing non-motor features of PD in well-designed longitudinal studies.

[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.

Parkinson's Disease Case Ascertainment in the Sister Study: A Cohort for Environmental Health Research

BACKGROUND

Large prospective studies are essential for investigating the environmental causes of Parkinson's disease (PD), but PD diagnosis via clinical exams is often infeasible in such studies.

OBJECTIVE

To present case ascertainment strategy and data collection in a US cohort of women.

METHODS

In the Sister Study (n = 50,884, baseline ages 55.6±9.0), physician-made PD diagnoses were first reported by participants or their proxies. Cohort-wide follow-up surveys collected data on subsequent diagnoses, medication usage and PD-relevant motor and nonmotor symptoms. We contacted self-reported PD cases and their treating physicians to obtain relevant diagnostic and treatment history. Diagnostic adjudication was made via expert review of all available data, except nonmotor symptoms. We examined associations of nonmotor symptoms with incident PD, using multivariable logistic regression models and reported odds ratio (OR) and 95% confidence intervals (CI).

RESULTS

Of the 371 potential PD cases identified, 242 diagnoses were confirmed. Compared with unconfirmed cases, confirmed cases were more likely to report PD diagnosis from multiple sources, medication usage, and motor and nonmotor features consistently during the follow-up. PD polygenic risk score was associated with confirmed PD (ORinter-quartile range = 1.74, 95% CI: 1.45-2.10), but not with unconfirmed cases (corresponding OR = 1.05). Hyposmia, dream-enacting behaviors, constipation, depression, unexplained weight loss, dry eyes, dry mouth, and fatigue were significantly related to PD risk, with ORs from 1.71 to 4.88. Only one of the eight negative control symptoms was associated with incident PD.

CONCLUSION

Findings support our PD case ascertainment approach in this large cohort of women. PD prodromal presentation is likely beyond its well-documented profile.

Fatigue in Patients with Idiopathic/Isolated REM Sleep Behavior Disorder

Introduction: Fatigue is one of the most common and disabling symptoms of Parkinson’s Disease (PD). The occurrence and clinical features of fatigue in patients with prodromal PD remain largely elusive. This study aimed to investigate the prevalence and clinical characteristics of fatigue in patients with idiopathic/isolated REM sleep behavior disorders (iRBD). Methods: A total of 97 polysomnography-confirmed iRBD patients were enrolled in this study. A comprehensive neurological assessment (including motor and non-motor assessment) was performed. Fatigue was assessed using the Fatigue Severity Scale (FSS). Motor and non-motor characteristics were compared between iRBD patients with and without fatigue. Logistic regression was used to identify the factors associated with fatigue. Results: The prevalence of fatigue was 35.05%. Compared to the non-fatigue patients, patients with fatigue had higher non-motor symptom scale (NMSS) score (p = 0.009), higher Hamilton Depression Rating Scale (HAMD) score (p = 0.002), and a higher prevalence of orthostatic hypotension (p = 0.021). Multivariate regression analysis showed that depression (OR 4.17, 95% CI 1.13−15.49, p = 0.033) and orthostatic hypotension (OR 2.80, 95% CI 1.09−7.18, p = 0.032) were significantly associated with fatigue in iRBD patients. Additionally, both NMSS (rs = 0.310, p = 0.002) and HAMD (rs = 0.385, p < 0.001) scores were mildly correlated with fatigue severity. Conclusion: Our study showed that fatigue is common in patients with iRBD. In addition, depression and orthostatic hypotension were independently associated with fatigue in iRBD patients.

Genome-wide association study of REM sleep behavior disorder identifies polygenic risk and brain expression effects

Rapid-eye movement (REM) sleep behavior disorder (RBD), enactment of dreams during REM sleep, is an early clinical symptom of alpha-synucleinopathies and defines a more severe subtype. The genetic background of RBD and its underlying mechanisms are not well understood. Here, we perform a genome-wide association study of RBD, identifying five RBD risk loci near SNCA, GBA, TMEM175, INPP5F, and SCARB2. Expression analyses highlight SNCA-AS1 and potentially SCARB2 differential expression in different brain regions in RBD, with SNCA-AS1 further supported by colocalization analyses. Polygenic risk score, pathway analysis, and genetic correlations provide further insights into RBD genetics, highlighting RBD as a unique alpha-synucleinopathy subpopulation that will allow future early intervention.

Insomnia and Other Sleep Disorders in Older Adults

Sleep disruption is common in older adults and is associated with many poor health outcomes. It is vital for providers to understand insomnia and other sleep disorders in this population. This article outlines age-related changes in sleep, and medical, psychiatric, environmental, and psychosocial factors that may impact sleep. It addresses the evaluation of sleep symptoms and diagnosis of sleep disorders. It aims to examine the evidence for non-pharmacological and pharmacologic treatment options for insomnia while weighing factors particularly germane to the aging adult..

Neuropsychiatric, neuropsychological, and neuroimaging features in isolated REM sleep behavior disorder: The importance of MCI

BACKGROUND

Mild cognitive impairment (MCI) is frequently diagnosed in patients with isolated rapid eye movement (REM) sleep behavior disorder (iRBD), although the extent of MCI-associated neuropathology has not yet been quantified. The present study compared the differences in neuropsychiatric, neuropsychological, and neuroimaging markers of neurodegeneration in MCI-iRBD and iRBD patients with normal cognition.

METHODS

Sixty-one patients with iRBD were included in the study: 30 patients were included in the MCI subgroup (RBD-MCI) and 31 in the normal cognition subgroup (RBD-NC). Both groups underwent neuropsychiatric and neuropsychological assessments to evaluate psychopathological symptoms and neuropsychological functions. Brain [18F]FDG PET and 123I-FP-CIT-SPECT were performed to evaluate brain glucose metabolism and nigrostriatal dopaminergic function in convenient subgroups of patients, respectively.

RESULTS

Neuropsychological measures generally confirmed overall cognitive decline in patients with iRBD-MCI. Immediate long-term verbal memory and visuospatial functions, as well as attentional-executive impairment were evident in the MCI group compared to the NC group. Neuroimaging results indicated reduced brain glucose uptake in the bilateral posterior cingulate cortex and more evident nigrostriatal deafferentation in the RBD-MCI group. There were no differences in psychopathological symptoms between the two groups.

CONCLUSIONS

This study confirmed that iRBD patients with MCI had a more impaired cognitive status that those with NC. Moreover, the MCI subgroup presented reduced cerebral glucose consumption in brain areas critical for cognition, and a more severe deafferentation of the nigro-striatal regions, highlighting the importance of identifying iRBD patients with MCI for urgent neuroprotective trials.

Cognitive Impairment in Older Adults: Epidemiology, Diagnosis, and Treatment

Cognitive impairment and dementia affect dozens of millions of people worldwide and cause significant distress to patients and caregivers and a financial burden to families and health care systems. Careful history-taking, cognitive and physical examination, and supplemental neuroimaging and fluid-based biomarkers can accurately diagnose neurocognitive disorders. Management includes non-pharmacological and pharmacological treatments tailored to the etiology and to the individual.

Correction of the wake-sleep cycle by intranasal administration of dopamine in modeling of the preclinical stage of Parkinson's disease in rats

Sleep disorders, which are among the earliest and most sensitive non-motor manifestations of Parkinson's disease (PD), are not diagnosed in 40–50 % of patients and are not subject to the necessary correction. In this regard, the ineffectiveness of a late start of treatment, when more than 50 % of dopamine-producing neurons are already affected, dictates the need to search for and develop approaches to the prevention and slowdown of neurodegenerative pathology at the preclinical stages of its development using adequate experimental models. Taking into account the low bioavailability of dopamine (DA) and data on the advantages of the intranasal route of administration in comparison with oral and parenteral methods of drug delivery to the CNS, the aim of the work was to study the neurophysiological features of the wake-sleep cycle as early manifestations of nigrostriatal insufficiency and the effect of intranasal administration of DA on the quality of sleep during the formation of the preclinical stage of PD in rats. It was shown that under the conditions of modeling PD, the cyclic organization of sleep with a predominance of incomplete cycles against the background of hyperproduction of slow-wave sleep and REM phases are early manifestations of nigrostriatal insufficiency. Course administration of DA at a dose of 3 mg/kg is accompanied by the normalization of sleep quality in the form of reduction (by 76 %) in the number of incomplete cycles. The preventive orientation of the obtained effects may indicate a certain therapeutic potential of intranasal delivery of DA to the brain, aimed at slowing down the processes of neurodegeneration and possibly delaying its clinical manifestation

Stereotyped Relationship Between Motor and Cognitive Metabolic Networks in Parkinson's Disease

BACKGROUND

Idiopathic Parkinson's disease (iPD) is associated with two distinct brain networks, PD-related pattern (PDRP) and PD-related cognitive pattern (PDCP), which correlate respectively with motor and cognitive symptoms. The relationship between the two networks in individual patients is unclear.

OBJECTIVE

To determine whether a consistent relationship exists between these networks, we measured the difference between PDRP and PDCP expression, termed delta, on an individual basis in independent populations of patients with iPD (n = 356), patients with idiopathic REM sleep behavioral disorder (iRBD) (n = 21), patients with genotypic PD (gPD) carrying GBA1 variants (n = 12) or the LRRK2-G2019S mutation (n = 14), patients with atypical parkinsonian syndromes (n = 238), and healthy control subjects (n = 95) from the United States, Slovenia, India, and South Korea.

METHODS

We used [18 F]-fluorodeoxyglucose positron emission tomography and resting-state fMRI to quantify delta and to compare the measure across samples; changes in delta over time were likewise assessed in longitudinal patient samples. Lastly, we evaluated delta in prodromal individuals with iRBD and subjects with gPD.

RESULTS

Delta was abnormally elevated in each of the four iPD samples (P < 0.05), as well as in the at-risk iRBD group (P < 0.05), with increasing values over time (P < 0.001). PDRP predominance was also present in gPD, with higher values in patients with GBA1 variants compared with the less aggressive LRRK2-G2019S mutation (P = 0.005). This trend was not observed in patients with atypical parkinsonian syndromes, who were accurately discriminated from iPD based on PDRP expression and delta (area under the curve = 0.85; P < 0.0001).

CONCLUSIONS

PDRP predominance, quantified by delta, assays the spread of dysfunction from motor to cognitive networks in patients with PD. Delta may therefore aid in differential diagnosis and in tracking disease progression in individual patients. © 2022 International Parkinson and Movement Disorder Society.

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.

Montreal Cognitive Assessment Predicts the Short-Term Risk of Lewy Body Disease in Isolated REM Sleep Behavior Disorder with Reduced MIBG Scintigraphy

Background

Long-term follow-up of isolated rapid eye movement (REM) sleep behavior disorder (IRBD) patients reveals a high risk of α-synucleinopathies.

Objective

We explored the early clinical predictive factors of phenoconversion from IRBD to Parkinson's disease (PD) or dementia with Lewy bodies (DLB).

Methods

We assessed baseline office-based cognitive test scores (Montreal Cognitive Assessment [MoCA-J], Mini-Mental State Examination [MMSE], and Frontal Assessment Battery [FAB]), motor function, and olfactory function in 36 consecutive polysomnography (PSG)-confirmed IRBD patients with reduced metaiodobenzylguanidine (MIBG) accumulation. PD or DLB was confirmed by medical chart review retrospectively.

Results

Of 36 IRBD patients, 19 (n = 19, 52.8%) with abnormal MoCA-J score (< 26) had significantly lower scores in trail making B, phonetic verbal fluency sub-items in the executive domain, and in delayed recall in the memory domain. In total, 12 (33.3%) patients developed PD or DLB; seven of 12 patients (58.3%) developed DLB at a mean follow-up period of 6.8 years. In the normal MoCA-J group (n = 17, 47.2%), two patients developed PD, but none developed dementia. Furthermore, in the abnormal MoCA-J group, seven patients developed DLB and three developed PD without dementia. The phenoconverter group had significantly lower scores in delayed recall in the memory domain compared to the disease-free group. Cox hazard analysis showed that MoCA-J was superior to MMSE.

Conclusions

Among IRBD patients with reduced cardiac MIBG accumulation, MoCA-J score of <26 (Mild Cognitive Impairment-Lewy body) and a low sub-item score for delayed recall predicted short-term progression to probable DLB.

Sleep disturbances in Lewy body dementia: A systematic review

BACKGROUND

Lewy body dementia (LBD) refers to both dementia with Lewy bodies (DLB) and Parkinson's disease with dementia (PDD). Sleep disturbances are common in LBD, and can include poor sleep quality, excessive daytime sleepiness (EDS), and rapid eye movement behaviour disorder (RBD). Despite the high clinical prevalence of sleep disturbances in LBD, they are under-studied relative to other dementias. The aim of the present systematic review was to examine the nature of sleep disturbances in LBD, summarise the effect of treatment studies upon sleep, and highlight specific and necessary directions for future research.

METHODS

Published studies in English were located by searching PubMED and PSYCArticles databases (until 10 June 2022). The search protocol was pre-registered in PROSPERO (CRD42021293490) and performed in accordance with PRISMA guidelines.

RESULTS

Following full-text review, a final total of 70 articles were included. These included 20 studies focussing on subjective sleep, 14 on RBD, 8 on EDS, 7 on objective sleep, and 1 on circadian rhythms. The majority of the 18 treatment studies used pharmacological interventions (n = 12), had an open-label design (n = 8), and were of low-to-moderate quality. Most studies (n = 55) included only patients with DLB. Due to the heterogeneity of the studies, we reported a narrative synthesis without meta-analysis.

CONCLUSIONS

At least one form of sleep disturbance may be present in as many as 90% of people with LBD. Subjectively poor sleep quality, excessive daytime sleepiness, and RBD are more common and severe in LBD relative to other dementias.

Who to Enroll in Parkinson Disease Prevention Trials? The Case for Composite Prodromal Cohorts

Significant progress has been made in expanding our understanding of prodromal Parkinson disease (PD), particularly for recognition of early motor and nonmotor signs and symptoms. Although identification of these prodromal features may improve our understanding of the earliest stages of PD, they are individually insufficient for early disease detection and enrollment of participants in prevention trials in most cases because of low sensitivity, specificity, and positive predictive value. Composite cohorts, composed of individuals with multiple co-occurring prodromal features, are an important resource for conducting prodromal PD research and eventual prevention trials because they are more representative of the population at risk for PD, allow investigators to evaluate the efficacy of an intervention across individuals with varying prodromal feature patterns, are able to produce larger sample sizes, and capture individuals at different stages of prodromal PD. A key challenge in identifying individuals with prodromal disease for composite cohorts and prevention trial participation is that we know little about the natural history of prodromal PD. To move toward prevention trials, it is critical that we better understand common prodromal feature patterns and be able to predict the probability of progression and phenoconversion. Ongoing research in cohort studies and administrative databases is beginning to address these questions, but further longitudinal analyses in a large population-based sample are necessary to provide a convincing and definitive strategy for identifying individuals to be enrolled in a prevention trial.

Imaging of sleep disorders in pre-Parkinsonian syndromes

PURPOSE OF REVIEW

Neuroimaging has been advanced in the last years and enabled clinicians to evaluate sleep disorders, especially isolated rapid eye movement sleep disorder (iRBD), which can be seen in alpha-synucleinopathies. iRBD is the best prodromal clinical marker for phenoconversion to these neurodegenerative diseases. This review aims to provide an update on advanced neuroimaging biomarkers in iRBD.

RECENT FINDINGS

Advanced structural MRI techniques, such as diffusion tensor imaging and functional MRI, neuromelanin-sensitive MRI, and scintigraphic neuroimaging such as cholinergic PET, dopamine transporter imaging - single-photon emission computerized tomography, perfusional single-photon emission computerized tomography, and cardiac metaiodobenzylguanidine can provide diagnostic and prognostic imaging biomarkers for iRBD, in isolation and more robustly when combined.

SUMMARY

New advanced neuroimaging can provide imaging biomarkers and aid in the appropriate clinical assessment and future therapeutic trials.

Sleep-controlling neurons are sensitive and vulnerable to multiple forms of α-synuclein: implications for the early appearance of sleeping disorders in α-synucleinopathies

Parkinson's disease, Multiple System Atrophy, and Lewy Body Dementia are incurable diseases called α-synucleinopathies as they are mechanistically linked to the protein, α-synuclein (α-syn). α-syn exists in different structural forms which have been linked to clinical disease distinctions. However, sleeping disorders (SDs) are common in the prodromal phase of all three α-synucleinopathies, which suggests that sleep-controlling neurons are affected by multiple forms of α-syn. To determine whether a structure-independent neuronal impact of α-syn exists, we compared and contrasted the cellular effect of three different α-syn forms on neurotransmitter-defined cells of two sleep-controlling nuclei located in the brainstem: the laterodorsal tegmental nucleus and the pedunculopontine tegmental nucleus. We utilized size exclusion chromatography, fluorescence spectroscopy, circular dichroism spectroscopy and transmission electron microscopy to precisely characterize ​​timepoints in the α-syn aggregation process with three different dominating forms of this protein (monomeric, oligomeric and fibril) and we conducted an in-depth investigation of the underlying neuronal mechanism behind cellular effects of the different forms of the protein using electrophysiology, multiple-cell calcium imaging, single-cell calcium imaging and live-location tracking with fluorescently-tagged α-syn. Interestingly, α-syn altered membrane currents, enhanced firing, increased intracellular calcium and facilitated cell death in a structure-independent manner in sleep-controlling nuclei, and postsynaptic actions involved a G-protein-mediated mechanism. These data are novel as the sleep-controlling nuclei are the first brain regions reported to be affected by α-syn in this structure-independent manner. These regions may represent highly important targets for future neuroprotective therapy to modify or delay disease progression in α-synucleinopathies.

[Diagnostic Value of Speech Acoustic Analysis in Parkinson's Disease]

Screening for and identifying patients with Parkinson's disease (PD) at an early stage and forming accurate diagnosis of PD during the course of the progression of the disease are of essential importance but still remain challenging for the clinical diagnosis and treatment of PD. One of the common clinical manifestations of PD is speech impairment, or voice impairment. Thanks to the recent advances in the field of acoustic analysis, a large number of acoustic parameters have been proposed for evaluating speech impairment quantitatively. Early identification and accurate diagnosis of PD was henceforth made possible through the application of speech acoustic analysis. Herein, we summarized the latest research findings on the application of acoustic analysis in PD diagnosis. We reported some acoustic parameters commonly used in the evaluation of voice impairment in PD patients. Then, we presented the diagnostic value of acoustic analysis in developing accurate diagnosis, early screening and differential diagnosis. Furthermore, we discussed the drawbacks and prospects of current studies, intending to enhance understanding of acoustic analysis of PD patients and its potential diagnostic values.

Development and Validation of a Predictive Nomogram for Possible REM Sleep Behavior Disorders

Objectives

To develop and validate a predictive nomogram for idiopathic rapid eye movement (REM) sleep behavior disorder (RBD) in a community population in Beijing, China.

Methods

Based on the validated RBD questionnaire-Hong Kong (RBDQ-HK), we identified 78 individuals with possible RBD (pRBD) in 1,030 community residents from two communities in Beijing. The least absolute shrinkage and selection operator (LASSO) regression was applied to identify candidate features and develop the nomogram. Internal validation was performed using bootstrap resampling. The discrimination of the nomogram was evaluated using the area under the curve (AUC) of the receiver operating characteristic (ROC) curve, and the predictive accuracy was assessed via a calibration curve. Decision curve analysis (DCA) was performed to evaluate the clinical value of the model.

Results

From 31 potential predictors, 7 variables were identified as the independent predictive factors and assembled into the nomogram: family history of Parkinson's disease (PD) or dementia [odds ratio (OR), 4.59; 95% confidence interval (CI), 1.35–14.45; p = 0.011], smoking (OR, 3.24; 95% CI, 1.84–5.81; p < 0.001), physical activity (≥4 times/week) (OR, 0.23; 95% CI, 0.12–0.42; p < 0.001), exposure to pesticides (OR, 3.73; 95%CI, 2.08–6.65; p < 0.001), constipation (OR, 6.25; 95% CI, 3.58–11.07; p < 0.001), depression (OR, 3.66; 95% CI, 1.96–6.75; p < 0.001), and daytime somnolence (OR, 3.28; 95% CI, 1.65–6.38; p = 0.001). The nomogram displayed good discrimination, with original AUC of 0.885 (95% CI, 0.845–0.925), while the bias-corrected concordance index (C-index) with 1,000 bootstraps was 0.876. The calibration curve and DCA indicated the high accuracy and clinical usefulness of the nomogram.

Conclusions

This study proposed an effective nomogram with potential application in the individualized prediction for pRBD.

Current Therapies and Drug Development Pipeline in Lewy Body Dementia: An Update

The term Lewy body dementia refers to either of two related diagnoses: dementia with Lewy bodies (DLB) and Parkinson's disease dementia (PDD). Clinical management of Lewy body dementia is challenging. The current treatment options focus on relieving symptoms; no disease-modifying therapies are available. There are currently no US Food and Drug Administration (FDA) approved drugs for the treatment of DLB, and there are only a few for PDD. Cholinesterase inhibitors are shown to be beneficial in improving cognitive symptoms in Lewy body dementia. Rivastigmine was approved by the FDA to treat PDD. Donepezil was approved in Japan as a treatment for DLB. Levodopa may provide modest benefit in treating motor symptoms and zonisamide in adjunct to low-dose levodopa helps with parkinsonism. Treatment of autonomic symptoms are based on symptomatic treatment with off-label agents. Our main objective in this article is to present an overview of the current pharmacological options available to treat the clinical features of DLB and PDD. When evaluating the existing management options for Lewy body dementia, it is difficult to fully separate PDD from DLB. However, we have attempted to identify whether the cited studies include patients with PDD and/or DLB. Moreover, we have provided an overview of the current drug pipeline in Lewy body dementia. All currently active trials are in phase I or II and most are focused on disease modification rather than symptomatic treatment. Phase II trial results for neflamapimod show promising results. Due to heterogeneity of symptoms and underlying pathophysiology, there is a need for new biomarker strategies and improved definitions of outcome measures for Lewy body dementia drug trials.

Glymphatic dysfunction in isolated REM sleep behavior disorder

OBJECTIVES

This study aimed to evaluate glymphatic-system function in patients with isolated rapid eye movement sleep behavior disorder (iRBD) in comparison with healthy controls by using diffusion tensor imaging (DTI) along the perivascular space (DTI-ALPS) method. We hypothesized that patients with iRBD may show glymphatic-system dysfunction.

METHODS

We retrospectively enrolled 18 patients with iRBD and 18 age- and sex-matched healthy controls. All participants underwent DTI magnetic resonance imaging (MRI) using the same 3T MRI scanner, and the DTI-ALPS index was calculated using DTI data. We evaluated the differences in the DTI-ALPS index between patients with iRBD and healthy controls. In addition, we evaluated the correlation between the DTI-ALPS index and demographic and polysomnographic characteristics.

RESULTS

The DTI-ALPS index was significantly different between the groups; it was significantly lower in patients with iRBD than in healthy controls (1.5647 vs. 1.7612, p = .0157). The index did not correlate with demographic and polysomnographic characteristics, including age, Epworth Sleepiness Scale score, total sleep time, sleep efficiency, sleep stage N1 ratio, stage N2 ratio, stage N3 ratio, stage R ratio, and total apnea-hypopnea index.

CONCLUSION

The DTI-ALPS index was significantly lower in patients with iRBD than in healthy controls, indicating the presence of glymphatic-system dysfunction in patients with iRBD. Our study also suggests that the DTI-ALPS index could serve as a biomarker for evaluating glymphatic-system function in neurological disorders.

Motor and non-motor circuit disturbances in early Parkinson disease: which happens first?

For the last two decades, pathogenic concepts in Parkinson disease (PD) have revolved around the toxicity and spread of α-synuclein. Thus, α-synuclein would follow caudo-rostral propagation from the periphery to the central nervous system, first producing non-motor manifestations (such as constipation, sleep disorders and hyposmia), and subsequently impinging upon the mesencephalon to account for the cardinal motor features before reaching the neocortex as the disease evolves towards dementia. This model is the prevailing theory of the principal neurobiological mechanism of disease. Here, we scrutinize the temporal evolution of motor and non-motor manifestations in PD and suggest that, even though the postulated bottom-up mechanisms are likely to be involved, early involvement of the nigrostriatal system is a key and prominent pathophysiological mechanism. Upcoming studies of detailed clinical manifestations with newer neuroimaging techniques will allow us to more closely define, in vivo, the role of α-synuclein aggregates with respect to neuronal loss during the onset and progression of PD.

Alzheimer's disease and sleep disorders: Insights into the possible disease connections and the potential therapeutic targets

One of the comorbid conditions in an individual with Alzheimer's disease is a sleep disorder. Clinical features of sleep disorders involve various sleep disturbances such as Obstructive Sleep Apnea (OSAS), Excessive Daytime Sleepiness (EDS), Rapid Eye Movement (REM), Breathing Disorders, Periodic limb movements in sleep (PLMS), etc. The primary tools used for the identification of such disturbances are Polysomnography (PSG) and Wrist actigraphy. This review will highlight and explains the different approaches used in the treatment of sleep disorders. Non-pharmacological treatments include Peter Hauri rules, sleep education program, and light therapy which play a key role in the regulation of sleep-wake cycles. Pharmacological therapy described in this article may be useful in treating sleep destruction in patients with Alzheimer's disease. Along with the Non-pharmacological and pharmacological treatment, here we discuss five commonly recognized plant-based nutraceuticals with hypothesized impact on sleep disorders: caffeine, chamomile, cherries, L-tryptophan, and valerian by the proper emphasis on the known mechanism of their action.

Classifying Idiopathic Rapid Eye Movement Sleep Behavior Disorder, Controls, and Mild Parkinson's Disease Using Gait Parameters

BACKGROUND

Subtle gait changes associated with idiopathic rapid eye movement sleep behavior disorder (iRBD) could allow early detection of subjects with future synucleinopathies.

OBJECTIVE

The aim of this study was to create a multiclass model, using statistical learning from probability distribution of gait parameters, to distinguish between patients with iRBD, healthy control subjects (HCs), and patients with Parkinson's disease (PD).

METHODS

Gait parameters were collected in 21 participants with iRBD, 21 with PD, and 21 HCs, matched for age, sex, and education level. Lasso sparse linear regression explored gait features able to classify the three groups.

RESULTS

The final model classified iRBD from HCs and from patients with PD equally well, with 95% accuracy, 100% sensitivity, and 90% specificity.

CONCLUSIONS

Gait parameters and a pretrained statistical model can robustly distinguish participants with iRBD from HCs and patients with PD. This could be used to screen subjects with future synucleinopathies in the general population and to identify a conversion threshold to PD. © 2022 International Parkinson and Movement Disorder Society.

The Gut-Brain Axis and Its Relation to Parkinson's Disease: A Review

Parkinson's disease is a chronic neurodegenerative disease characterized by the accumulation of misfolded alpha-synuclein protein (Lewy bodies) in dopaminergic neurons of the substantia nigra and other related circuitry, which contribute to the development of both motor (bradykinesia, tremors, stiffness, abnormal gait) and non-motor symptoms (gastrointestinal issues, urinogenital complications, olfaction dysfunction, cognitive impairment). Despite tremendous progress in the field, the exact pathways and mechanisms responsible for the initiation and progression of this disease remain unclear. However, recent research suggests a potential relationship between the commensal gut bacteria and the brain capable of influencing neurodevelopment, brain function and health. This bidirectional communication is often referred to as the microbiome-gut-brain axis. Accumulating evidence suggests that the onset of non-motor symptoms, such as gastrointestinal manifestations, often precede the onset of motor symptoms and disease diagnosis, lending support to the potential role that the microbiome-gut-brain axis might play in the underlying pathological mechanisms of Parkinson's disease. This review will provide an overview of and critically discuss the current knowledge of the relationship between the gut microbiota and Parkinson's disease. We will discuss the role of α-synuclein in non-motor disease pathology, proposed pathways constituting the connection between the gut microbiome and the brain, existing evidence related to pre- and probiotic interventions. Finally, we will highlight the potential opportunity for the development of novel preventative measures and therapeutic options that could target the microbiome-gut-brain axis in the context of Parkinson's disease.

Generalized EEG Slowing Across Phasic REM Sleep, Not Subjective RBD Severity, Predicts Neurodegeneration in Idiopathic RBD

PURPOSE

Idiopathic rapid eye movement sleep behavior disorder (iRBD) is the prodromal marker of α-synuclein degeneration with markedly high predictive value. We aim to evaluate the value of electroencephalography (EEG) data during rapid eye movement (REM) sleep and subjective RBD severity in predicting the conversion to neurodegenerative diseases in iRBD patients.

METHODS

At the baseline, iRBD patients underwent clinical assessment and video-polysomnography (PSG). Relative spectral power for nine frequency bands during phasic and tonic REM sleep in three regions of interest, slow-to-fast ratios, clinical and PSG variables were estimated and compared between iRBD patients who converted to neurodegenerative diseases (iRBD-C) and iRBD patients who remained disease-free (iRBD-NC). Receiver operating characteristic (ROC) curves evaluated the predictive performance of slow-to-fast ratios, and subjective RBD severity as assessed with RBD Questionnaire-Hong Kong.

RESULTS

Twenty-two (33.8%) patients eventually developed neurodegenerative diseases. The iRBD-C group showed shorter total sleep time (p < 0.001), lower stage 2 sleep percentage (p = 0.044), more periodic leg-movement-related arousal index (p = 0.004), increased tonic chin electromyelographic activity (p = 0.040) and higher REM density in the third REM episode (p = 0.034) than the iRBD-NC group. EEG spectral power analyses revealed that iRBD phenoconverters showed significantly higher delta and lower alpha power, especially in central and occipital regions during the phasic REM state compared to the iRBD-NC group. Significantly higher slow-to-fast ratios were observed in a more generalized way during the phasic state in the iRBD-C group compared to the iRBD-NC group. ROC analyses of the slowing ratio in occipital areas during phasic REM sleep yielded an area under the curve of 0.749 (p = 0.001), while no significant predictive value of subjective RBD severity was observed.

CONCLUSION

Our study shows that EEG slowing, especially in a more generalized manner during the phasic period, may be a promising marker in predicting phenoconversion in iRBD, rather than subjective RBD severity.

Multiple Sclerosis and related disorders

Multiple Sclerosis (MS) is a common neuroinflammatory disorder which is associated with disabling clinical consequences. The MS disease process may involve neural centers implicated in the control of breathing, leading to ventilatory disturbances during both wakefulness and sleep. In this chapter, a brief overview of MS disease mechanisms and clinical sequelae including sleep disorders is provided. The chapter then focuses on obstructive sleep apnea-hypopnea (OSAH) which is the most prevalent respiratory control abnormality encountered in ambulatory MS patients. The diagnosis, prevalence, and clinical consequences as well as data on effects of OSAH treatment in MS patients are discussed, including the impact on the disabling symptom of fatigue and other clinical sequelae. We also review pathophysiologic mechanisms contributing to OSAH in MS, and in turn mechanisms by which OSAH may impact on the MS disease process, resulting in a bidirectional relationship between these two conditions. We then discuss central sleep apnea, other respiratory control disturbances, and the pathogenesis and management of respiratory muscle weakness and chronic hypoventilation in MS. We also provide a brief overview of Neuromyelitis Optica Spectrum Disorders and review current data on respiratory control disturbances and sleep-disordered breathing in that condition.

Longitudinal Studies of Sleep Disturbances in Parkinson's Disease

PURPOSE OF REVIEW

Sleep disorders are among the most common non-motor symptoms in Parkinson's disease (PD). Recent longitudinal studies of sleep in PD have utilized validated sleep questionnaires and video-polysomnography performed over multiple time points. This review summarizes existing longitudinal studies focusing on the prevalence, associations, and changes of sleep disorders in PD over time, as well as the methodologies used in these studies.

RECENT FINDINGS

Fifty-three longitudinal studies of sleep in PD were identified: excessive daytime sleepiness, insomnia, obstructive sleep apnea, rapid eye movement sleep behavior disorder (RBD), restless legs syndrome, and shift work disorder were studied in addition to other studies that had focused on either multiple sleep disorders or broadly on sleep disorders as a whole. The prevalence of sleep disorders increases over time and are associated particularly with non-motor features of disease. RBD is now considered an established prodromal feature of PD, but other sleep disorders do not clearly increase risk of subsequent PD. Further work is necessary to determine if treatment of sleep disorders in PD alters disease symptom and their progression or reduces PD risk. Longitudinal studies of sleep in PD have demonstrated a high prevalence of sleep disorders that are associated with non-motor features of PD which can increase over time. More work is necessary to determine if treatment of sleep disorders can alter the course of PD.