Biomarkers of conversion to α-synucleinopathy in isolated rapid-eye-movement sleep behaviour disorder

Association of Cardiovascular Autonomic Failure With Progression and Phenoconversion in Isolated REM Sleep Behavior Disorder

BACKGROUND AND OBJECTIVES

Isolated REM sleep behavior disorder (iRBD) is a prodromal state of α-synucleinopathies, presenting years before overt neurodegenerative disorders. Autonomic nervous system (ANS) involvement, particularly cardiovascular autonomic failure, may indicate progression. However, its role as a (multidimensional) marker for disease progression and phenoconversion remains unclear. This study aimed to investigate whether cardiovascular autonomic failure and symptoms of autonomic dysfunction serve as multidimensional markers in patients with iRBD.

METHODS

We conducted a prospective cohort study of patients with iRBD (iRBDs) and controls. Participants underwent cardiovascular reflex tests (CRTs) with beat-to-beat monitoring of blood pressure (BP) and ANS symptom assessments at baseline and annually. Primary outcomes were prevalence and progression of cardiovascular autonomic failure and the risk factors of phenoconversion. Longitudinal changes were evaluated through mixed-effects regression, predictors associated with conversion with Cox regression analysis.

RESULTS

Sixty-four iRBDs (mean age 68.89 ± 6.75 years, 75% male) and 67 controls (66.57 ± 7.91 years, 68% male) were recruited. At baseline, iRBDs exhibited a prevalent sympathetic cardiovascular dysfunction, with more frequent neurogenic orthostatic hypotension (nOH in 9 iRBDs) and abnormal BP responses to CRTs (pathologic Valsalva maneuver [VM] overshoot in 27 iRBDs). Longitudinal data demonstrated progressive deterioration of sympathetic baroreflex function, with increased prevalence of nOH (7 iRBDs with incident nOH; yearly odds ratio [OR] = 2.44) and deterioration of parasympathetic cardiovagal function. Thirteen patients (20.3%) phenoconverted to α-synucleinopathies. Neurogenic OH (hazard ratio [HR] = 5.05), altered sympathetic baroreflex function (pathologic VM HR = 3.49), and blunted parasympathetic cardiovagal responses (pathologic deep breathing heart rate ratio HR = 3.27) were significant risk factors for phenoconversion; their early appearance 5 years from iRBD onset increased the conversion risk, up to 4-fold. Symptoms of autonomic failure were more prevalent in iRBD and deteriorated over time but failed to predict conversion.

DISCUSSION

Progressive deterioration of cardiovascular autonomic function is a feature of iRBDs and affects the risk of phenoconversion. Limitations include the relatively short follow-up period and small number of converters. This study highlights the importance of objective cardiovascular autonomic testing as a multidimensional marker for risk stratification in iRBD.

Parkinson's disease with possible REM sleep behavior disorder correlated with more severe glymphatic system dysfunction

This study aimed to evaluate the glymphatic system activity in Parkinson's disease (PD) with and without rapid eye movement sleep behavior disorder (RBD) using the diffusion tensor image analysis along the perivascular space (DTI-ALPS) methods. Overall, 91 patients with PD and 33 healthy controls were recruited. PD patients were divided into PD-RBD (n = 55) and PD-nRBD (n = 36) groups according to RBD scales. The ALPS-index and enlarged perivascular spaces (EPVS) scores were calculated. PD-RBD group exhibited lower ALPS-index than PD-nRBD and controls after controlling for the effect of age (p = 0.018 and p = 0.001). PD-RBD group showed higher UPDRS part I and HAMD score than those in PD-nRBD group. RBD symptom was independently correlated with ALPS-index in PD (β = -0.259, p = 0.014). In conclusion, PD with possible RBD correlated with more severe glymphatic system dysfunction and non-motor symptoms than those in PD without RBD.

REM sleep and neurodegeneration

Several brainstem, subcortical and cortical areas are involved in the generation of rapid eye movement (REM) sleep. The alteration of these structures as a result of a neurodegenerative process may therefore lead to REM sleep anomalies. REM sleep behaviour disorder is associated with nightmares, dream-enacting behaviours and increased electromyographic activity in REM sleep. Its isolated form is a harbinger of synucleinopathies such as Parkinson's disease or dementia with Lewy bodies, and neuroprotective interventions are advocated. This link might also be present in patients taking antidepressants, with post-traumatic stress disorder, or with a history of repeated traumatic head injury. REM sleep likely contributes to normal memory processes. Its alteration has also been proposed to be part of the neuropathological changes occurring in Alzheimer's disease.

Differential striatal dopamine binding in Parkinson's Disease with and without REM sleep behavior disorder: A Tc-99 m TRODAT-1 SPECT study

BACKGROUND

Rapid eye movement (REM) sleep behavior disorder (RBD) is an early and significant prodromal marker for Parkinson's disease (PD). While the association between RBD and PD has been well-documented, the underlying pathophysiology differentiating PD patients with RBD (PD-RBD +) from those without RBD (PD-RBD-) remained unclear. This study aims to investigate the possible relationship between RBD and striatal dopamine depletion in de novo PD patients.

METHODS

A retrospective, cross-sectional study was conducted on 151 PD patients. We used standard questionnaires and measurements to assess motor and nonmotor symptoms. The dopaminergic function was assessed utilizing Tc-99 m TRODAT-1 SPECT imaging, and statistical analyses were performed to compare dopamine transporter (DAT) binding between patients with or without probable RBD (pRBD).

RESULTS

The PD-pRBD + group exhibited significantly lower DAT binding in the caudate nucleus (OR 0.618; 95% CI 0.392-0.618; p = 0.039) and putamen (OR 0.554; 95% CI 0.319-0.962; p = 0.036) compared to the PD-pRBD- group. The PD-pRBD + group also had a higher prevalence of non-motor symptoms, including depression (OR 7.499; 95% CI 2.770-20.299; p < 0.001) and constipation (OR 2.356; 95% CI 1.090-5.092; p = 0.029). Although trends toward increased dementia (12.3% in PD-pRBD + , 6.4% in PD-pRBD-, p = 0.266) and falls (16.4% in PD-pRBD + , 11.5% in PD-pRBD-, p = 0.482) were observed in the PD-pRBD + group, these did not reach statistical significance.

CONCLUSION

The presence of RBD in PD patients is associated with greater striatal dopaminergic dysfunction, suggesting a distinct subtype with potentially faster disease progression. These findings highlight the importance of early RBD identification in PD patients to guide more personalized interventions.

Frequency and Longitudinal Course of Autonomic Reflex Testing Abnormalities in Isolated REM Sleep Behavior Disorder

STUDY OBJECTIVES

Autonomic dysfunction is common across the α-synucleinopathies including isolated RBD (iRBD), however the presence, severity and distribution of autonomic dysfunction as a risk factor for phenoconversion in iRBD remains unclear. We aimed to characterize autonomic reflex testing (ART) abnormalities in a cohort of participants with iRBD and assess them as phenoconversion biomarkers.

METHODS

We performed ART on 45 individuals with iRBD and evaluated the ability of ART components (sympathetic cholinergic, cardiovagal, sympathetic adrenergic) to predict phenoconversion using univariate and multivariate models combined with measures of olfaction, cognition, motor function, and skin biopsy assessment of dermal synuclein.

RESULTS

Forty-one individuals with iRBD were enrolled (age 66.7 ± 7.4 yrs, 27% female), and followed annually for an average of 2.9 ± 2.4 yrs, with four participants lost to follow-up. Eight participants with iRBD phenoconverted during their follow-up period (3 Parkinson's disease, 4 dementia with Lewy bodies and 1 multiple system atrophy), yielding a phenoconversion rate of 6.6% per year. Eighty-seven percent of iRBD participants had an abnormal baseline ART, and 100% had an abnormal follow-up ART. A combination of MDS-UPDRS III score and cardiovagal dysfunction (abnormal HRVdb) best predicted phenoconversion (AUC = 0.77), especially when combined with iRBD disease duration (AUC = 0.89).

CONCLUSIONS

ANS dysfunction was common and spanned all domains of autonomic function. Cardiovagal function was the most common domain affected and most predictive of phenoconversion, especially if combined with motor examination and disease duration. Longitudinal studies with larger sample sizes are needed to confirm these findings.

Speech and language biomarkers for Parkinson's disease prediction, early diagnosis and progression

Parkinson's disease (PD), a multifaceted neurodegenerative disorder, can manifest as an array of motor and non-motor symptoms. Among these, speech and language impairments are particularly prevalent, often preceding motor dysfunctions. Emerging research indicates that these impairments may serve as early disease indicators. In this narrative review, we synthesised current findings on the potential of speech and language symptoms in PD identification and progression monitoring. Our review highlights convergent, albeit preliminary, lines of evidence supporting the value of speech-related features in detecting early or prodromal PD, even across language groups, especially with sophisticated analytical techniques. Distinct speech patterns in PD subtypes and other neurological disorders may assist in differential diagnosis and inform targeted management efforts. These features also evolve over the disease course and could effectively be utilised for disease tracking and guide management plan modifications. Advances in digital voice processing allow cost-effective, remote and scalable monitoring for larger populations.

Nigral volume loss in prodromal, early, and moderate Parkinson's disease

The loss of melanized neurons in the substantia nigra pars compacta (SNc) is a hallmark pathology in Parkinson's disease (PD). Melanized neurons in SNc can be visualized in vivo using magnetization transfer (MT) effects. Nigral volume was extracted in data acquired with a MT-prepared gradient echo sequence in 50 controls, 90 non-manifest carriers (46 LRRK2 and 44 GBA1 nonmanifest carriers), 217 prodromal hyposmic participants, 76 participants with rapid eye movement sleep behavior disorder (RBD), 194 de novo PD patients and 26 moderate PD patients from the Parkinson's Progressive Markers Initiative. No difference in nigral volume was seen between controls and LRRK2 and GBA1 non-manifest carriers ( F =0.732; P =0.483). A significant main effect in group was observed between controls, prodromal hyposmic participants, RBD participants, and overt PD patients ( F =9.882; P <10 -3 ). This study shows that nigral depigmentation can be robustly detected in prodromal and overt PD populations.

Saccade, pupil, and blink abnormalities in prodromal and manifest alpha-synucleinopathies

BackgroundSaccade, pupil, and blink control are impaired in patients with α-synucleinopathies (αSYN): Parkinson's disease (PD) and multiple system atrophy (MSA). Isolated REM (rapid eye movement) Sleep Behavior Disorder (iRBD) is a prodromal stage of PD and MSA and a prime candidate for investigating early oculo-pupillo-motor abnormalities that may precede or predict conversion to clinically manifest αSYN.ObjectiveDetermine whether saccade, pupil, and blink responses in iRBD are normal or similar to those identified in PD and MSA.MethodsVideo-based eye-tracking was conducted with 68 patients with iRBD, 49 with PD, 17 with MSA, and 95 healthy controls (CTRL) performing an interleaved pro-/anti-saccade task that probed sensory, motor, and cognitive processes involved in eye movement control.ResultsHorizontal saccade and blink behavior was intact in iRBD, but abnormal in PD and MSA. iRBD patients, however, demonstrated reduced pupil dilation size, which closely resembled the changes found in PD and MSA. In the iRBD group, the extent of these pupillary changes appeared to correlate with the degree of hyposmia and reduction in dopamine transporter imaging signal.ConclusionsPupil abnormalities were present in iRBD, but blink and horizontal saccade responses were intact. Future longitudinal studies are required to determine which prodromal pupil abnormalities predict conversion from iRBD to PD or MSA and to identify the time window, in relation to conversion, when horizontal saccade responses become abnormal.

Salivary biomarkers for the molecular diagnosis of dementia with Lewy bodies

BackgroundDespite dementia with Lewy bodies (DLB) being the second most common form of neurodegenerative dementia, more than 80% of DLB cases are initially misdiagnosed. Alpha-synuclein (a-syn) and tau species have been detected in peripheral tissues and biological fluids of DLB patients and among different biological fluids, saliva represent an easely accessible and non-invasive source for biomarker detection.ObjectiveThis study aimed to investigate salivary a-syn and tau species as molecular disease biomarkers, assessing their potential in the diagnosis of DLB and in the differential diagnosis on respect to Alzheimer's disease (AD) and Parkinson's disease (PD).MethodsWe measured total and oligomeric a-syn, total-tau, and S199-phosphorylated-tau (pS199-tau) in the saliva of 21 DLB, 20 AD, 20 PD patients, and 20 healthy subjects (HS) using quantitative enzyme-linked immunosorbent assay (ELISA) analyses.ResultsSalivary total a-syn was not significantly changed between the different groups, whereas all pathological groups had a higher oligomeric a-syn concentration than HS. Salivary total-tau concentration was higher in all the pathological groups than HS, whereas the concentrations did not differ among patients' groups. Conversely, salivary levels of pS199-tau was higher in DLB and AD patients than in HS and PD patients. Both correlation matrix and principal component analysis showed that core clinical DLB features were related to a-syn pathology, while cognitive decline was associated with salivary levels of pS199-tau in both DLB and AD patients. Receiver operating characteristic analysis reported high diagnostic accuracy for both a-syn oligomers and pS199-tau, between DLB and HS, and an adequate accuracy between DLB and PD. Conversely, the diagnostic accuracy was not optimal between DLB patients and AD patients.ConclusionsThese findings provide preliminary evidence that salivary a-syn and tau species might be promising in identifying DLB patients on respect to PD patients and HS, while the diagnostic potential is limited on respect to AD.

Transforming Sleep Monitoring: Review of Wearable and Remote Devices Advancing Home Polysomnography and Their Role in Predicting Neurological Disorders

This paper explores the progressive era of sleep monitoring, focusing on wearable and remote devices contributing to advances in the concept of home polysomnography. We begin by exploring the basic physiology of sleep, establishing a theoretical basis for understanding sleep stages and associated changes in physiological variables. The review then moves on to an analysis of specific cutting-edge devices and technologies, with an emphasis on their practical applications, user comfort, and accuracy. Attention is also given to the ability of these devices to predict neurological disorders, particularly Alzheimer's and Parkinson's disease. The paper highlights the integration of hardware innovations, targeted sleep parameters, and partially advanced algorithms, illustrating how these elements converge to provide reliable sleep health information. By bridging the gap between clinical diagnosis and real-world applicability, this review aims to elucidate the role of modern sleep monitoring tools in improving personalised healthcare and proactive disease management.

From Night to Light: A Bibliometric Analysis of the Global Research Trajectory of Sleep Disorders in Parkinson's Disease

Purpose

Sleep disorders are prevalent non-motor symptoms in patients with Parkinson's disease (PD), significantly diminishing the overall quality of life for patients and potentially accelerating the deterioration of motor and cognitive functions, accelerating disease progression. Despite increasing research on sleep disorders in PD, a comprehensive analysis of the knowledge structure and key issues in this field are still lacking. This study aims to identify research hotspots and emerging trends related to sleep disorders in PD through a detailed bibliometric analysis.

Patients and Methods

On October 1, 2024, an extensive search was conducted in the Web of Science Core Collection (WOSCC) database to gather relevant literature on sleep disorders in PD. Bibliometric and knowledge mapping analyses were performed using CiteSpace, VOSviewer, and bibliometrix.

Results

Between January 1, 2004, and October 1, 2024, a total of 3,655 publications on sleep disorders in PD were published by 3,387 institutions across 87 countries. The volume of publications has shown a steady increase, a trend projected to continue. Current research is primarily centered on Neurosciences, Pharmacology, and Clinical Neurology. Emerging trends involve comprehensive evaluations of sleep, early diagnosis and prevention of various sleep disorder subtypes in PD, and advancing research through animal models to develop effective therapies. Emerging keywords include machine learning, sleep quality, biomarkers, covid-19, and mouse model.

Conclusion

This bibliometric analysis sheds light on the global landscape of PD-related sleep disorder research over the past two decades, highlighting key countries, institutions, authors, and journals driving advancements in the field. Moreover, it uncovers pivotal research hotspots and emerging trends, offering valuable insights and guidance for scholars engaged in this area.

Mild behavioral impairment in idiopathic REM sleep behavior disorder and Lewy body disease continuum

To investigate the clinical impact of mild behavioral impairment (MBI) in a predefined cohort with Lewy body disease (LBD) continuum. Eighty-four patients in the LBD continuum participated in this study, including 35 patients with video-polysomnography-confirmed idiopathic REM sleep behavior disorder (iRBD) and 49 clinically established LBD. Evaluations included the Movement Disorder Society-Unified Parkinson's Disease Rating Scale (MDS-UPDRS), neuropsychological tests, and MBI Checklist (MBI-C). We examined the clinical associates of MBI-C and its diagnostic values in predicting disease severity and cognitive impairment across the LBD continuum. Participants were classified into 19 cognitively normal (CN), 45 mild cognitive impairment (MCI), and 20 dementia groups. Median MBI-C total scores were 1.0, 8.0, and 18.5 for CN, MCI, and dementia groups, respectively, with a significant increasing trend (p < 0.001). The MBI-C total score demonstrated significant correlations with the MDS-UPDRS part 1 (r = 0.504, p < 0.001) and total scores (r = 0.508, p < 0.001). Furthermore, significant correlations were observed between MBI-C and cognitive performances in frontal/executive (DSC: r = -0.314, p = 0.006; TMT-B: r = -0.338, p = 0.003) and attentional (TMT-A: r = -0.343, p = 0.002) domains. A cutoff 5.0 effectively differentiated the MCI from CN groups (area under the curve (AUC = 0.74). Furthermore, the MBI-C effectively discriminated the iRBD patients with high phenoconversion risk against those with low-risk (cut-off 4.0, AUC = 0.72). The MBI-C may be a useful screening questionnaire reflecting clinical severity across the LBD continuum. Longitudinal studies are needed to determine its value in monitoring disease progression in prodromal LBD.

Brain MRI Detection of an Abnormal Peak Width of Skeletonized Mean Diffusivity in REM Sleep Behavior Disorder

BACKGROUND AND PURPOSE

Peak width of skeletonized mean diffusivity (PSMD) is a novel marker of white matter damage, which may be related to small vessel disease. This study aimed to investigate the presence of white matter damage in patients with isolated rapid eye movement sleep behavior disorder (RBD) using PSMD.

METHODS

We enrolled patients with newly diagnosed isolated RBD confirmed by polysomnography and age- and sex-matched healthy controls. Diffusion tensor imaging (DTI) was conducted using a 3-Tesla MRI scanner. We measured the PSMD based on DTI in several steps, including preprocessing, skeletonization, application of a custom mask, and histogram analysis, using the Functional Magnetic Resonance Imaging of the Brain Software Library program. We compared the incidence of PSMD between patients with RBD and healthy controls and performed a correlation analysis between PSMD and clinical factors in patients with RBD.

RESULTS

Thirty patients with isolated RBD and 41 healthy controls were enrolled. The PSMD was significantly higher in patients with RBD than that in the healthy controls (3.078 vs. 2.746 × 10-4 mm2/s, p = 0.001). In addition, PSMD positively correlated with age in patients with RBD (r = 0.477, p = 0.007). However, PSMD was not associated with other clinical or polysomnographic factors.

CONCLUSION

Patients with isolated RBD had a higher PSMD than healthy controls, indicating the evidence of white matter damage in patients with RBD. This finding highlights the potential of PSMD as a marker for detecting white matter damage, which may be related to small vessel diseases, in patients with sleep disorders.

Intersection of Sleep Disorders and Parkinson Disease: Unveiling the Bidirectional Relationship

BACKGROUND

Patients with Parkinson's Disease (PD) frequently exhibit non-motor symptoms, particularly sleep disturbances. Sleep disorders in PD patients are intricately linked to the pathogenesis and progression of PD itself, exacerbating neurodegenerative processes and worsening patient quality of life.

OBJECTIVES

This review underscores the significance of sleep disorders in PD, highlighting their prevalence, impact on disease progression, and the bidirectional relationship between sleep disruption and neurodegeneration. It aims to enhance clinician awareness for better diagnosis and management of sleep-related comorbidities in PD.

METHODS

A comprehensive literature search was conducted in PubMed and Scopus using key terms such as "sleep disorders", "Parkinson's disease", "REM sleep behavior disorder", "restless legs syndrome", "insomnia", "obstructive sleep apnea", "excessive daytime sleepiness", "circadian rhythm disorders", "sleep and neurodegeneration".

RESULTS

Sleep disorders are prevalent in PD affecting up to 90% of patients. Conditions such as insomnia, REM sleep behavior disorder, restless legs syndrome, obstructive sleep apnea, excessive daytime sleepiness, and circadian rhythm disorders are commonly reported. These disorders are linked to multifactorial biological mechanisms and are associated with more severe disease phenotypes. Of note, several evidence shows that sleep abnormalities may contribute to neuroinflammation and neurodegeneration, further accelerating the disease course.

CONCLUSIONS

Sleep disturbances are critical non-motor symptoms in PD. Early diagnosis and tailored management of sleep disorders are essential for improving clinical outcomes and potentially offering neuroprotective benefits.

Multiple system atrophy: advances in pathophysiology, diagnosis, and treatment

Multiple system atrophy is an adult-onset, sporadic, and progressive neurodegenerative disease. People with this disorder report a wide range of motor and non-motor symptoms. Overlap in the clinical presentation of multiple system atrophy with other movement disorders (eg, Parkinson's disease and progressive supranuclear palsy) is a concern for accurate and timely diagnosis. Over the past 5 years, progress has been made in understanding key pathophysiological events in multiple system atrophy, including the seeding of α-synuclein inclusions and the detection of disease-specific α-synuclein strains. Diagnostic criteria were revised in 2022 with the intention to improve the accuracy of a diagnosis of multiple system atrophy, particularly for early disease stages. Early signals of efficacy in clinical trials have indicated the potential for disease-modifying therapies for multiple system atrophy, although no trial has yet provided unequivocal evidence of neuroprotection in this rare disease. The advances in pathophysiology could play a part in biomarker discovery for early diagnosis as well as in the development of disease-modifying therapies.

Spatial-temporal dynamic evolution of lewy body dementia by metabolic PET imaging

PURPOSE

Lewy body dementia (LBD) is a neurodegenerative disease with high heterogeneity and complex pathogenesis. Our study aimed to use disease progression modeling to uncover spatial-temporal dynamic evolution of LBD in vivo, and to explore differential profiles of clinical features, glucose metabolism, and dopaminergic function among different evolution-related subtypes.

METHODS

A total of 123 participants (31 healthy controls and 92 LBD patients) who underwent 18F-FDG PET scans were retrospectively enrolled. 18F-FDG PET-based Subtype and Stage Inference (SuStaIn) model was established to illustrate spatial-temporal evolutionary patterns and categorize relevant subtypes. Then subtypes and stages were further related to clinical features, glucose metabolism, and dopaminergic function of LBD patients.

RESULTS

This 18F-FDG PET imaging-based approach illustrated two distinct patterns of neurodegenerative evolution originating from the neocortex and basal ganglia in LBD and defined them as subtype 1 and subtype 2, respectively. There were obvious differences between subtypes. Compared with subtype 1, subtype 2 exhibited a greater proportion of male patients (P = 0.045) and positive symptoms such as visual hallucinations (P = 0.033) and fluctuating cognitions (P = 0.033). Cognitive impairment, metabolic abnormalities, dopaminergic dysfunction and progression were all more severe in subtype 2 (all P < 0.05). In addition, a strong association was observed between SuStaIn subtypes and two clinical phenotypes (Parkinson's disease dementia and dementia with Lewy bodies) (P = 0.005).

CONCLUSIONS

Our findings based on 18F-FDG PET and data-driven model illustrated spatial-temporal dynamic evolution of LBD and categorized novel subtypes with different evolutionary patterns, clinical and imaging features in vivo. The evolution-related subtypes are associated with LBD clinical phenotypes, which supports the perspective of existence of distinct entities in LBD spectrum.

From prodromal stages to clinical trials: The promise of digital speech biomarkers in Parkinson's disease

Speech impairment is a common and disabling symptom in Parkinson's disease (PD), affecting communication and quality of life. Advances in digital speech processing and artificial intelligence have revolutionized objective speech analysis. Given the complex nature of speech impairment, acoustic speech analysis offers unique biomarkers for neuroprotective treatments from the prodromal stages of PD. Digital speech biomarkers can monitor levodopa-induced motor complications, detect the effects of deep brain stimulation, and provide feedback for behavioral speech therapy. This review updates the mechanisms underlying speech impairment, the impact of speech phenotypes, and the effects of interventions on speech. We evaluate the strengths, potential weaknesses, and suitability of promising digital speech biomarkers in PD for capturing disease progression and treatment efficacy. Additionally, we explore the translational potential of PD speech biomarkers to other neuropsychiatric diseases, offering insights into motion, cognition, and emotion. Finally, we highlight knowledge gaps and suggest directions for future research to enhance the use of quantitative speech measures in disease-modifying clinical trials. The findings demonstrate that one year is sufficient to detect disease progression in early PD through speech biomarkers. Voice quality, pitch, loudness, and articulation measures appear to capture the efficacy of treatment interventions most effectively. Certain speech features, such as loudness and articulation rate, behave oppositely in different neurological diseases, offering valuable insights for differential diagnosis. In conclusion, this review highlights speech as a biomarker in tracking disease progression, especially in the prodromal stages of PD, and calls for further longitudinal studies to establish its efficacy across diverse populations.

Insular monoaminergic deficits in prodromal α-synucleinopathies

METHODS

This study assessed data from two cohorts of patients with alpha-synucleinopathies (University of Brescia and University of Rome Tor-Vergata cohorts). Consecutive participants with video-polysomnography-confirmed iRBD, Parkinson's disease (PD), dementia with Lewy bodies (DLB) and controls underwent neurological, clinical and 123I-FP-CIT SPECT imaging assessments. Individuals with iRBD were longitudinally monitored to collect clinical phenoconversion to PD or DLB. The main outcome was to identify whole brain 123 I-FP-CIT SPECT measures reflecting monoaminergic deficits in each clinical group as compared to controls.

RESULTS

The cohort (n = 184) included 45 patients with iRBD, 47 PD, 42 DLB and 50 age-matched controls. Individuals with iRBD were categorized as RBD-DAT- (n = 32) and RBD-DAT+ (n = 13), according to nigrostriatal assessment used in clinical practice. Compared to controls, RBD-DAT- showed an early involvement of the left insula, which increased in RBD-DAT+, and was present in patients with Parkinson's disease and dementia with Lewy bodies. Longitudinal cox regression analyses revealed a higher risk of phenoconversion in individuals with iRBD and insular monoaminergic deficits [HR = 3.387; CI 95%: 1.18-10.27].

INTERPRETATION

In this study, altered insular monoaminergic binding in iRBD was associated with phenoconversion to DLB or PD. These findings may provide a helpful stratification approach for future pharmacological or non-pharmacological interventions.

Progression trajectories from prodromal to overt synucleinopathies: a longitudinal, multicentric brain [18F]FDG-PET study

The phenoconversion trajectory from idiopathic/isolated Rapid eye movement (REM) sleep behavior disorder (iRBD) towards either Parkinson's Disease (PD) or Dementia with Lewy Bodies (DLB) is currently uncertain. We investigated the capability of baseline brain [18F]FDG-PET in differentiating between iRBD patients eventually phenoconverting to PD or DLB, by deriving the denovoPDRBD-related pattern (denovoPDRBD-RP) from 32 de novo PD patients; and the denovoDLBRBD-RP from 30 de novo DLB patients, both with evidence of RBD at diagnosis. To explore [18F]FDG-PET phenoconversion trajectories prediction power, we applied these two patterns on a group of 115 iRBD patients followed longitudinally. At follow-up (25.6 ± 17.2 months), 42 iRBD patients progressed through overt alpha-synucleinopathy (21 iRBD-PD and 21 iRBD-DLB converters), while 73 patients remained stable at the last follow-up visit (43.2 ± 27.6 months). At survival analysis, both patterns were significantly associated with the phenoconversion trajectories. Brain [18F]FDG-PET is a promising biomarker to study progression trajectories in the alpha-synucleinopathy continuum.

Sleep disorders and Parkinson's disease: is there a right direction?

In the last years, the hypothesis of a close relationship between sleep disorders (SDs) and Parkinson's disease (PD) has significantly strengthened. Whether this association is causal has been also highlighted by recent evidence demonstrating a neurobiological link between SDs and PD. Thus, the question is not whether these two chronic conditions are mutually connected, but rather how and when this relationship is expressed. Supporting this, not all SDs manifest with the same temporal sequence in PD patients. Indeed, SDs can precede or occur concomitantly with the onset of the clinical manifestation of PD. This review discusses the existing literature, putting under a magnifying glass the timing of occurrence of SDs in PD-neurodegeneration. Based on this, here, we propose two possible directions for studying the SDs-PD relationship: the first direction, from SDs to PD, considers SDs as potential biomarker/precursor of future PD-neurodegeneration; the second direction, from PD to SDs, considers SDs as concomitant symptoms in manifest PD, mainly related to primary PD-neuropathology and/or parkinsonian drugs. Furthermore, for each direction, we questioned SDs-PD relationship in terms of risk factors, neuronal circuits/mechanisms, and impact on the clinical phenotype and disease progression. Future research is needed to investigate whether targeting sleep may be the winning strategy to treat PD, in the context of a personalized precision medicine.

Automatic quantification of REM sleep without atonia reliably identifies patients with REM sleep behavior disorder: a possible screening tool?

BACKGROUND

REM Sleep Behavior Disorder (RBD) is characterized by absence of physiological muscle atonia during REM sleep (REM sleep without atonia, RWA). Nigro-striatal dopaminergic impairment is a feature of Parkinson disease (PD) and can be identified in prodromal stages as well, such as idiopathic RBD (iRBD). Aims of this study are to explore the efficacy of an automatic RWA quantification in identifying RBD patients and the correlation between RWA and nigro-striatal dopaminergic function.

METHODS

Forty-five iRBD, 46 PD with RBD, 24 PD without RBD patients and 11 healthy controls were enrolled in the Genoa Center (group A) and 25 patients with iRBD (group B) were enrolled in the Danish Center. Group A underwent brain [123I]FP-CIT-SPECT and group B underwent brain [18F]PE2I-PET as measures of nigro-striatal dopaminergic function. Chin muscle activity was recorded in all subjects and analyzed by applying a published automatic algorithm. Correlations between RWA and nigro-striatal dopaminergic function were explored.

RESULTS

The automatic quantification of RWA significantly differentiated RBD from non-RBD subjects (AUC = 0.86), although with lower accuracy compared with conventional visual scoring (AUC = 0.99). No significant correlation was found between RWA and nigro-striatal dopaminergic function.

CONCLUSION

The automatic quantification of RWA is a reliable tool to identify subjects with RBD and may be used as a first-line screening tool, but without correlations with nigro-striatal dopaminergic functioning.

Smartphone Voice Calls Provide Early Biomarkers of Parkinsonism in Rapid Eye Movement Sleep Behavior Disorder

BACKGROUND

Speech dysfunction represents one of the initial motor manifestations to develop in Parkinson's disease (PD) and is measurable through smartphone.

OBJECTIVE

The aim was to develop a fully automated and noise-resistant smartphone-based system that can unobtrusively screen for prodromal parkinsonian speech disorder in subjects with isolated rapid eye movement sleep behavior disorder (iRBD) in a real-world scenario.

METHODS

This cross-sectional study assessed regular, everyday voice call data from individuals with iRBD compared to early PD patients and healthy controls via a developed smartphone application. The participants also performed an active, regular reading of a short passage on their smartphone. Smartphone data were continuously collected for up to 3 months after the standard in-person assessments at the clinic.

RESULTS

A total of 3525 calls that led to 5990 minutes of preprocessed speech were extracted from 72 participants, comprising 21 iRBD patients, 26 PD patients, and 25 controls. With a high area under the curve of 0.85 between iRBD patients and controls, the combination of passive and active smartphone data provided a comparable or even more sensitive evaluation than laboratory examination using a high-quality microphone. The most sensitive features to induce prodromal neurodegeneration in iRBD included imprecise vowel articulation during phone calls (P = 0.03) and monopitch in reading (P = 0.05). Eighteen minutes of speech corresponding to approximately nine calls was sufficient to obtain the best sensitivity for the screening.

CONCLUSION

We consider the developed tool widely applicable to deep longitudinal digital phenotyping data with future applications in neuroprotective trials, deep brain stimulation optimization, neuropsychiatry, speech therapy, population screening, and beyond. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Single-Molecule Fingerprinting Reveals Different Growth Mechanisms in Seed Amplification Assays for Different Polymorphs of α-Synuclein Fibrils

α-Synuclein (αSyn) aggregates, detected in the biofluids of patients with Parkinson's disease (PD), have the ability to catalyze their own aggregation, leading to an increase in the number and size of aggregates. This self-templated amplification is used by newly developed assays to diagnose Parkinson's disease and turns the presence of αSyn aggregates into a biomarker of the disease. It has become evident that αSyn can form fibrils with slightly different structures, called "strains" or polymorphs, but little is known about their differential reactivity in diagnostic assays. Here, we compared the properties of two well-described αSyn polymorphs. Using single-molecule techniques, we observed that one of the polymorphs had an increased tendency to undergo secondary nucleation and we showed that this could explain the differences in reactivity observed in in vitro seed amplification assay and cellular assays. Simulations and high-resolution microscopy suggest that a 100-fold difference in the apparent rate of growth can be generated by a surprisingly low number of secondary nucleation "points" (1 every 2000 monomers added by elongation). When both strains are present in the same seeded reaction, secondary nucleation displaces proportions dramatically and causes a single strain to dominate the reaction as the major end product.

Increased sighing during sleep as a marker of multiple system atrophy

Parkinson's disease (PD) and multiple system atrophy (MSA) can be preceded by isolated REM sleep behavior disorder (iRBD). As excessive sighing during wakefulness is a red flag for MSA in individuals with parkinsonism, we measured sighing during slow wave sleep (N3) and REM sleep as potential biomarkers in 73 participants with MSA, 111 with iRBD, 257 with PD, and 115 controls. The number of sighs/hour of N3 (index) was higher in the MSA group than in the other groups. Sighs were rarer in REM sleep than in N3 sleep. A sigh index greater than 3.4/h of N3 was 95% sensitive in discriminating participants with MSA from controls, and a sigh index greater than 0.8 sigh/h of REM sleep was 87% specific in discriminating participants with MSA from controls. MSA participants with (vs. without) sigh were younger, had a lower apnea-hypopnea index (but no more stridor), and had no other difference in motor, autonomic, cognitive, and sensory symptoms. The sigh index could be used for screening for MSA in the millions of middle-aged persons who receive polysomnography for other purposes. Whether sighing in iRBD predicts preferential conversion towards MSA should be measured in a longitudinal study.

Blunted tachycardia and cardiac sympathetic denervation in isolated rapid eye movement sleep behavior disorder

BACKGROUND

Isolated rapid eye movement sleep behavior disorder (iRBD) serves as a prodromal phase of Parkinson's disease (PD) and dementia with Lewy bodies (DLB). Blunted tachycardia (BT) during postural changes indicates neurogenic orthostatic hypotension, a marker of autonomic dysfunction. We aimed to investigate whether BT is associated with cardiac sympathetic neurogenic denervation. Additionally, we conducted a preliminary short-term follow-up to examine the potential prognostic significance of BT regarding phenoconversion and mortality.

METHODS

Forty-three patients with iRBD at Shiga University of Medical Science Hospital underwent active standing tests to identify BT, defined by a specific ratio of decrease in systolic blood pressure to inadequate increase in heart rate after standing, and orthostatic hypotension. 123I-metaiodobenzylguanidine myocardial scintigraphy (123I-MIBG) and dopamine transporter single-photon emission computed tomography (DAT-SPECT) were performed. Participants were followed up for 3.4 ± 2.4 years for phenoconversion and 4.0 ± 2.3 years for mortality assessment, and the risk of events was analyzed using log-rank tests.

RESULTS

Among the 43 participants (mean age, 72.3 ± 7.9 years; 8 female), 17 met the BT criteria. We found no significant comorbidity-related differences in hypertension or diabetes between the BT(+) and BT(-) groups. Orthostatic hypotension was more prevalent in the BT(+) group than in the BT(-) group (47.1% vs 7.7%, p = 0.003). BT(+) patients were older with a lower early and delayed MIBG uptake; however, no significant differences were observed in DAT accumulation. Phenoconversion was observed in seven (41.2%) BT(+) and seven (26.9%) BT(-) patients. Three deaths were recorded in the BT(+) group (17.6%) and three in the BT(-) group (11.5%). No significant differences were observed in the risk of phenoconversion or mortality between the groups.

CONCLUSIONS

We have identified the possibility that BT reflects cardiac sympathetic neurogenic denervation in patients with iRBD. Future research is needed to elucidate the potential prognostic value of BT.

Acetyl-DL-leucine in two individuals with REM sleep behavior disorder improves symptoms, reverses loss of striatal dopamine-transporter binding and stabilizes pathological metabolic brain pattern-case reports

Isolated REM Sleep Behavior Disorder (iRBD) is considered a prodrome of Parkinson's disease (PD). We investigate whether the potentially disease-modifying compound acetyl-DL-leucine (ADLL; 5 g/d) has an effect on prodromal PD progression in 2 iRBD-patients. Outcome parameters are RBD-severity sum-score (RBD-SS-3), dopamine-transporter single-photon emission computerized tomography (DAT-SPECT) and metabolic "Parkinson-Disease-related-Pattern (PDRP)"-z-score in 18F-fluorodeoxyglucose positron emission tomography (FDG-PET). After 3 weeks ADLL-treatment, the RBD-SS-3 drops markedly in both patients and remains reduced for >18 months of ADLL-treatment. In patient 1 (female), the DAT-SPECT putaminal binding ratio (PBR) decreases in the 5 years pretreatment from normal (1.88) to pathological (1.22) and the patient's FDG-PET-PDRP-z-score rises from 1.72 to 3.28 (pathological). After 22 months of ADLL-treatment, the DAT-SPECT-PBR increases to 1.67 and the FDG-PET-PDRP-z-score stabilizes at 3.18. Similar results are seen in patient 2 (male): his DAT-SPECT-PBR rises from a pretreatment value of 1.42 to 1.72 (close to normal) and the FDG-PET-PDRP-z-score decreases from 1.02 to 0.30 after 18 months of ADLL-treatment. These results support exploration of whether ADLL may have disease-modifying properties in prodromal PD.

Sleep and sleep disorders in people with Parkinson's disease

Sleep disorders are common in people with Parkinson's disease. These disorders, which increase in frequency throughout the course of the neurodegenerative disease and impair quality of life, include insomnia, excessive daytime sleepiness, circadian disorders, obstructive sleep apnoea, restless legs syndrome, and rapid eye movement (REM) sleep behaviour disorder. The causes of these sleep disorders are complex and multifactorial, including the degeneration of the neural structures that modulate sleep, the detrimental effect of some medications on sleep, the parkinsonian symptoms that interfere with mobility and comfort in bed, and comorbidities that disrupt sleep quality and quantity. The clinical evaluation of sleep disorders include both subjective (eg, questionnaires or diaries) and objective (eg, actigraphy or video polysomnography) assessments. The management of patients with Parkinson's disease and a sleep disorder is challenging and should be individualised. Treatment can include education aiming at changes in behaviour (ie, sleep hygiene), cognitive behavioural therapy, continuous dopaminergic stimulation at night, and specific medications. REM sleep behaviour disorder can occur several years before the onset of parkinsonism, suggesting that the implementation of trials of neuroprotective therapies should focus on people with this sleep disorder.

α-Synuclein in speculative neuronal extracellular vesicles: A marker for Parkinson's disease risk?

This opinion piece describes major limitations of using α-synuclein in speculative neuronally enriched for diagnosing or predicting Parkinson's disease risk from prodromal conditions such as REM behaviour disorder. It concludes that such an approach is unreliable and recommends that future researchers divert away to more widely accepted approaches such as seed amplification assays.

Machine Learning Predicts Phenoconversion from Polysomnography in Isolated REM Sleep Behavior Disorder

Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) is a prodromal stage of alpha-synucleinopathies. This study aimed at developing a fully-automated machine learning framework for the prediction of phenoconversion in patients with iRBD by using data recorded during polysomnography (PSG). A total of 66 patients with iRBD were included, of whom 18 converted to an overt alpha-synucleinopathy within 2.7 ± 1.0 years. For each patient, a baseline PSG was available. Sleep stages were scored automatically, and time and frequency domain features were derived from electromyography (EMG) and electroencephalography (EEG) signals in REM and non-REM sleep. Random survival forest was employed to predict the time to phenoconversion, using a four-fold cross-validation scheme and by testing several combinations of features. The best test performances were obtained when considering EEG features in REM sleep only (Harrel's C-index: 0.723 ± 0.113; Uno's C-index: 0.741 ± 0.11; integrated Brier score: 0.174 ± 0.06). Features describing EEG slowing had high importance for the machine learning model. This is the first study employing machine learning applied to PSG to predict phenoconversion in patients with iRBD. If confirmed in larger cohorts, these findings might contribute to improving the design of clinical trials for neuroprotective treatments.

Plasma level of alpha-synuclein oligomers as a biomarker for isolated rapid eye movement sleep behavior disorder diagnosis and progression: a prospective cohort study

Background

Alpha-synuclein oligomers (o-α-syn) are pivotal in the pathogenesis of α-synucleinopathy. Isolated rapid eye movement (REM) sleep behavior disorder (iRBD) serves as an early indicator of the disease, offering insights into disease mechanisms and early intervention. Nevertheless, the diagnostic and predictive potential of o-α-syn in iRBD remains largely unexplored. This study aimed to evaluate the plasma levels of o-α-syn in patients and investigate their utility as biomarkers for diagnosis of and predicting phenoconversion in iRBD.

Methods

A total of 143 participants, including 77 polysomnography-confirmed iRBD patients and 66 normal controls (NC), were recruited for this longitudinal observational study. Baseline clinical assessments and plasma collection were conducted for all iRBD patients, with 72 of them undergoing regularly prospective follow-up assessments for parkinsonism or dementia. Plasma levels of o-α-syn were quantified using enzyme-linked immunosorbent assay, and were compared between groups using a general linear model adjusted for age and sex. The diagnostic performance of plasma o-α-syn in iRBD was evaluated by area under the receiver operating characteristic curve (AUC) with 95% CI. Cox regression analysis and Kaplan-Meier survival curves were employed to assess the predictive value of plasma o-α-syn for phenoconversion in iRBD.

Results

Plasma o-α-syn levels did not exhibit statistically significant differences among iRBD converter patients, iRBD nonconverter patients, and NC. The AUC for distinguishing NC from iRBD was 0.52 (95% CI: 0.42-0.62, p = 0.682). Spearman correlation analysis revealed a significant positive correlation between plasma o-α-syn levels and MOCA scores in the iRBD group (p < 0.001). Subgroup analyses indicated that iRBD patients with cognitive decline (p = 0.058) and depressive symptoms (p = 0.017) had notably lower o-α-syn levels compared to those without such symptoms. Over a median follow-up period of 5.83 years, 26 iRBD patients developed neurodegenerative synucleinopathies. Cox regression and Kaplan-Meier survival curve analyses indicated that plasma level of o-α-syn lacked a predictive value for disease conversion in iRBD patients.

Conclusion

Despite a potential role in the pathophysiology of iRBD, o-α-syn are not appropriate biomarkers for diagnosing or predicting disease progression. While this study offers insights into the pathogenesis of iRBD and neurodegenerative synucleinopathies, further large-scale longitudinal studies are warranted to validate these findings.

Network disruption based on multi-modal EEG-MRI in α-synucleinopathies

Background

Brain network dysfunction has been characterized by resting-state electroencephalography (EEG) and magnetic resonance imaging (MRI) in the prodromal stage. This study aimed to identify multi-modal electrophysiological and neuroimaging biomarkers for differential diagnosis in synucleinopathies and phenoconversion in isolated rapid eye movement sleep behavior disorder (iRBD).

Methods

We enrolled 35 patients with multiple system atrophy (MSA), 32 with Parkinson's disease (PD), 30 with iRBD and 30 matched healthy controls (HC). Power spectral density (PSD) was calculated in different frequency bands. EEG functional connectivity (FC) was calculated using the weighted Phase Lag Index (wPLI) after source localization. Significant network disruptions were further confirmed by MRI FC analysis.

Results

Quantitative EEG analysis demonstrated that delta and theta power spectral density significantly differed among MSA, PD and HC. The increased PSD was correlated with cognitive decline and olfactory dysfunction in PD. Band-specific FC profiles were observed in theta, alpha, and gamma bands. The hypoconnected alpha network significantly correlated with motor dysfunction, while the gamma FC distinguished PD from MSA. By integrating EEG and MRI network analyses, we found that FC between the olfactory cortex and dorsolateral prefrontal cortex was significantly different between MSA and PD. A multimodal discriminative model for MSA and PD, integrating spectral and FC attributes of EEG and MRI, yielded an area under the receiver operating characteristic curve of 0.900. Simultaneously, we found the FC abnormalities were more prominent than spectral features in iRBD indicating prodromal dysfunction. The decreased FC between the angular gyrus and striatum was identified in α-synucleinopathies. This hypoconnectivity was associated with dopaminergic degeneration in iRBD examined by dopamine transporter imaging.

Discussion

Our study demonstrated EEG spectral and functional profiles in prodromal and clinical-defined synucleinopathies. Multimodal EEG and MRI provided a novel approach to discriminate MSA and PD, and monitor neurodegenerative progression in the preclinical phase.

Developing disease-modifying interventions in idiopathic REM sleep behavior disorder and early synucleinopathy

Alpha-synucleinopathies are prevalent neurological disorders that cause significant disability, leading to progressive clinical deterioration that is currently managed solely through symptomatic treatment. Efforts to evaluate disease-modifying therapies during the established stage of the disease have not yielded positive outcomes in terms of clinical or imaging efficacy endpoints. However, alpha-synucleinopathies have a long prodromal phase that presents a promising opportunity for intervention with disease-modifying therapies. The presence of polysomnography-confirmed REM sleep behavior disorder (RBD) is the most reliable risk factor for identifying individuals in the prodromal stage of alpha-synucleinopathy. This paper discusses the rationale behind targeting idiopathic/isolated RBD in disease-modifying trials and outlines possible study designs, including strategies for patient stratification, selection of biomarkers to assess disease progression and patient eligibility, as well as the identification of suitable endpoints. Additionally, the potential targets for disease-modifying treatment in alpha-synucleinopathies are summarized.

Detection of α-Synuclein in Oral Mucosa by Seed Amplification Assay in Synucleinopathies and Isolated REM Sleep Behavior Disorder

OBJECTIVE

Evidence of abnormal α-synuclein (α-Syn) deposition in the brain is required for definitive diagnosis of synucleinopathies, which remains challenging. The seed amplification assay (SAA) is an innovative technique that can detect the seeding activity of misfolded α-Syn, enabling the amplification and detection of minute quantities of pathogenic α-Syn aggregates. This study aimed to evaluate oral mucosa α-Syn SAA as possible diagnostic and prodromal biomarkers for synucleinopathies.

METHODS

A total of 107 Parkinson's disease (PD) patients, 99 multiple system atrophy (MSA) patients, 33 patients with isolated rapid eye movement sleep behavior disorder (iRBD) and 103 healthy controls (HC) were included. The SAA was applied to detect the seeding activity of α-Syn from oral mucosa. A combination of morphological, biochemical, and biophysical methods was also used to analyze the fibrils generated from the oral mucosa α-Syn SAA.

RESULTS

Structured illumination microscopy images revealed the increased α-Syn species in oral mucosa of PD, MSA, and iRBD patients than in HCs. Oral mucosa α-Syn SAA distinguished patients with PD from HC with 67.3% sensitivity and 90.3% specificity. Oral mucosa was α-Syn SAA positive in 53.5% MSA patients and 63.6% iRBD patients. Furthermore, the α-Syn fibrils generated from MSA demonstrated greater resistance to proteinase K digestion and exhibited stronger cytotoxicity compared to those from PD patients.

CONCLUSION

Oral mucosa α-Syn seeding activity may serve as novel non-invasive diagnostic and prodromal biomarkers for synucleinopathies. The α-Syn aggregates amplified from the oral mucosa of PD and MSA exhibited distinct biochemical and biophysical properties. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Idiopathic Rapid Eye Movement Sleep Behavior Disorder (iRBD) Shares Similar Fecal Short-Chain Fatty Acid Alterations with Multiple System Atrophy (MSA) and Parkinson's Disease (PD)

BACKGROUND

Idiopathic rapid eye movement sleep behavior disorder (iRBD) is considered as a prodromal stage of synucleinopathies. Fecal short-chain fatty acid (SCFA) changes in iRBD and the relationships with synucleinopathies have never been investigated.

OBJECTIVES

To investigate fecal SCFA changes among iRBD, multiple system atrophy (MSA), and Parkinson's disease (PD), and evaluate their relationships.

METHODS

Fecal SCFAs and gut microbiota were measured in 29 iRBD, 42 MSA, 40 PD, and 35 normal controls (NC) using gas chromatography-mass spectrometry and 16S rRNA gene sequencing.

RESULTS

Compared with NC, fecal SCFA levels (propionic, acetic, and butyric acid) were lower in iRBD, MSA, and PD. Combinations of these SCFAs could differentiate NC from iRBD (AUC 0.809), MSA (AUC 0.794), and PD (AUC 0.701). Decreased fecal SCFAs were associated with the common reducing SCFA-producing gut microbiota in iRBD, MSA, and PD.

CONCLUSIONS

iRBD shares similar fecal SCFA alterations with MSA and PD, and the combination of these SCFAs might be a potential synucleinopathies-related biomarker. © 2024 International Parkinson and Movement Disorder Society.

Autonomic Dysfunction in REM Sleep Disorder: The Role of Respiration in HRV Analysis. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2024;2024:1-4. [PMID: 40039146 DOI: 10.1109/embc53108.2024.10781943] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Autonomic nervous system (ANS) has been suggested often associated with the isolated rapid eye movement (REM) sleep behavior disorder (iRBD), with iRBD, and heart rate variability (HRV) is a commonly used tool to assess it. However, the accuracy of HRV is heavily influenced by respiratory rate (RespR), potentially causing misinterpretation of frequency domain HRV indices. This study compares sleep-related ANS function between iRBD patients and a control group (CG) using respiratory-adjusted HRV spectral analysis. It involves 20 iRBD and 20 CG participants in each group, from which five-minute ECG signal epochs during N2, N3, and REM sleep phases are analyzed. RespR were estimated from ECG-derived respiratory signals. Both low and high frequency bands definition for HRV analysis were redefined using the RespR. The results indicate significant differences in HRV parameters between iRBD and CG subjects during REM sleep, highlighting disrupted autonomic regulation in iRBD. This finding is also evident in non-REM phases, thus emphasizing the need to incorporate RespR in HRV analysis, especially in sleep-related studies, for a comprehensive understanding of autonomic dysfunction.

The Complex Relationship between Sleep and Cognitive Reserve: A Narrative Review Based on Human Studies

Sleep and brain/cognitive/neural reserve significantly impact well-being and cognition throughout life. This review aims to explore the intricate relationship between such factors, with reference to their effects on human cognitive functions. The specific goal is to understand the bidirectional influence that sleep and reserve exert on each other. Up to 6 February 2024, a methodical search of the literature was conducted using the PubMed database with terms related to brain, cognitive or neural reserve, and healthy or disturbed sleep. Based on the inclusion criteria, 11 articles were selected and analyzed for this review. The articles focus almost exclusively on cognitive reserve, with no explicit connection between sleep and brain or neural reserve. The results evidence sleep's role as a builder of cognitive reserve and cognitive reserve's role as a moderator in the effects of physiological and pathological sleep on cognitive functions. In conclusion, the findings of the present review support the notion that both sleep and cognitive reserve are critical factors in cognitive functioning. Deepening comprehension of the interactions between them is essential for devising strategies to enhance brain health and resilience against age- and pathology-related conditions.

Presynaptic Dopaminergic Imaging Characterizes Patients with REM Sleep Behavior Disorder Due to Synucleinopathy

OBJECTIVE

To apply a machine learning analysis to clinical and presynaptic dopaminergic imaging data of patients with rapid eye movement (REM) sleep behavior disorder (RBD) to predict the development of Parkinson disease (PD) and dementia with Lewy bodies (DLB).

METHODS

In this multicenter study of the International RBD study group, 173 patients (mean age 70.5 ± 6.3 years, 70.5% males) with polysomnography-confirmed RBD who eventually phenoconverted to overt alpha-synucleinopathy (RBD due to synucleinopathy) were enrolled, and underwent baseline presynaptic dopaminergic imaging and clinical assessment, including motor, cognitive, olfaction, and constipation evaluation. For comparison, 232 RBD non-phenoconvertor patients (67.6 ± 7.1 years, 78.4% males) and 160 controls (68.2 ± 7.2 years, 53.1% males) were enrolled. Imaging and clinical features were analyzed by machine learning to determine predictors of phenoconversion.

RESULTS

Machine learning analysis showed that clinical data alone poorly predicted phenoconversion. Presynaptic dopaminergic imaging significantly improved the prediction, especially in combination with clinical data, with 77% sensitivity and 85% specificity in differentiating RBD due to synucleinopathy from non phenoconverted RBD patients, and 85% sensitivity and 86% specificity in discriminating PD-converters from DLB-converters. Quantification of presynaptic dopaminergic imaging showed that an empirical z-score cutoff of -1.0 at the most affected hemisphere putamen characterized RBD due to synucleinopathy patients, while a cutoff of -1.0 at the most affected hemisphere putamen/caudate ratio characterized PD-converters.

INTERPRETATION

Clinical data alone poorly predicted phenoconversion in RBD due to synucleinopathy patients. Conversely, presynaptic dopaminergic imaging allows a good prediction of forthcoming phenoconversion diagnosis. This finding may be used in designing future disease-modifying trials. ANN NEUROL 2024;95:1178-1192.

Biomarkers of neurodegeneration in isolated and antidepressant-related rapid eye movement sleep behavior disorder

BACKGROUND AND PURPOSE

This study compared the features of isolated rapid eye movement (REM) sleep behavior disorder (iRBD) and antidepressant-related REM sleep behaviour disorder (RBD) with the aim of highlighting markers that might distinguish the two entities.

METHODS

The observational cohort study included RBD patients with and without antidepressant use (antiD+ and antiD- patients, respectively), without cognitive impairment and parkinsonism. Clinical features of RBD, subtle motor and non-motor symptoms of parkinsonism, sleep architecture, REM atonia index, dopamine transporter-single photon emission computed tomography (DAT-SPECT) and skin biopsies for the intraneuronal alpha-synuclein (α-syn), were evaluated in the baseline work-up.

RESULTS

Thirty-nine patients, 10 antiD+ and 29 antiD-, were included. AntiD+ patients (more frequently female) reported more psychiatric symptoms, less violent dream enactment, and less frequent hyposmia. Dermal α-syn was detected in 93.1% of antiD- versus 30% of antiD+ patients (p = 0.00024). No differences appeared in other motor and non-motor symptoms, Movement Disorder Society-Unified Parkinson's Disease Rating Scale part III score, DAT-SPECT, or polysomnographic features.

CONCLUSIONS

Patients with antidepressant-related RBD have clinical and neuropathological features suggesting a lower risk of evolution than those with iRBD.

EEG-based machine learning models for the prediction of phenoconversion time and subtype in isolated rapid eye movement sleep behavior disorder

STUDY OBJECTIVES

Isolated rapid eye movement sleep behavior disorder (iRBD) is a prodromal stage of α-synucleinopathies and eventually phenoconverts to overt neurodegenerative diseases including Parkinson's disease (PD), dementia with Lewy bodies (DLB), and multiple system atrophy (MSA). Associations of baseline resting-state electroencephalography (EEG) with phenoconversion have been reported. In this study, we aimed to develop machine learning models to predict phenoconversion time and subtype using baseline EEG features in patients with iRBD.

METHODS

At baseline, resting-state EEG and neurological assessments were performed on patients with iRBD. Calculated EEG features included spectral power, weighted phase lag index, and Shannon entropy. Three models were used for survival prediction, and four models were used for α-synucleinopathy subtype prediction. The models were externally validated using data from a different institution.

RESULTS

A total of 236 iRBD patients were followed up for up to 8 years (mean 3.5 years), and 31 patients converted to α-synucleinopathies (16 PD, 9 DLB, 6 MSA). The best model for survival prediction was the random survival forest model with an integrated Brier score of 0.114 and a concordance index of 0.775. The K-nearest neighbor model was the best model for subtype prediction with an area under the receiver operating characteristic curve of 0.901. Slowing of the EEG was an important feature for both models.

CONCLUSIONS

Machine learning models using baseline EEG features can be used to predict phenoconversion time and its subtype in patients with iRBD. Further research including large sample data from many countries is needed to make a more robust model.

Disclosing the Risk Associated with Isolated REM Behavior Disorder: The Sleep Experts' Perspective

BACKGROUND

Isolated rapid-eye-movement sleep behavior disorder (iRBD) is associated with a high risk for phenoconversion to a neurodegenerative disorder, but the optimal approach for disclosure of this risk to patients is still debated.

OBJECTIVES

The aim of this study was to explore views and experiences of iRBD experts regarding risk disclosure.

METHODS

In this qualitative study, semi-structured interviews with sleep experts caring for patients with iRBD were analyzed through a conventional content analysis approach.

RESULTS

We interviewed 22 iRBD experts (eight female, average age of 51.8 years) from 18 Italian sleep centers; 21/22 regularly disclosed the risks associated with iRBD, usually after the video-polysomnography, and 8/22 regularly mentioned phenoconversion rates. Content analysis allowed us to identify three main themes. First, sleep experts reported several points in favor of risk disclosure, especially related to the principle of beneficence, but some highlighted the need for specific learning on the topic. Second, experts favored a patient-tailored disclosure that should not upset the patient unnecessarily, since phenoconversion is uncertain. Third, risk disclosure was seen by participants as a relational task that should be carried out in person in the context of a trusting patient-physician relationship, while they had contrasting views regarding patients' previous knowledge.

CONCLUSIONS

Sleep experts generally preferred a tailored and reassuring approach to risk disclosure within a framework of relational autonomy. The results of this study indicate the need for specific education, training, and recommendations concerning risk disclosure that should also include patients' and families' preferences.

Associations of sleep disorders with serum neurofilament light chain levels in Parkinson's disease

BACKGROUND

Sleep disorders are a prevalent non-motor symptom of Parkinson's disease (PD), although reliable biological markers are presently lacking.

OBJECTIVES

To explore the associations between sleep disorders and serum neurofilament light chain (NfL) levels in individuals with prodromal and early PD.

METHODS

The study contained 1113 participants, including 585 early PD individuals, 353 prodromal PD individuals, and 175 healthy controls (HCs). The correlations between sleep disorders (including rapid eye movement sleep behavior disorder (RBD) and excessive daytime sleepiness (EDS)) and serum NfL levels were researched using multiple linear regression models and linear mixed-effects models. We further investigated the correlations between the rates of changes in daytime sleepiness and serum NfL levels using multiple linear regression models.

RESULTS

In baseline analysis, early and prodromal PD individuals who manifested specific behaviors of RBD showed significantly higher levels of serum NfL. Specifically, early PD individuals who experienced nocturnal dream behaviors (β = 0.033; P = 0.042) and movements of arms or legs during sleep (β = 0.027; P = 0.049) showed significantly higher serum NfL levels. For prodromal PD individuals, serum NfL levels were significantly higher in individuals suffering from disturbed sleep (β = 0.038; P = 0.026). Our longitudinal findings support these baseline associations. Serum NfL levels showed an upward trend in early PD individuals who had a higher total RBDSQ score (β = 0.002; P = 0.011) or who were considered as probable RBD (β = 0.012; P = 0.009) or who exhibited behaviors on several sub-items of the RBDSQ. In addition, early PD individuals who had a high total ESS score (β = 0.001; P = 0.012) or who were regarded to have EDS (β = 0.013; P = 0.007) or who exhibited daytime sleepiness in several conditions had a trend toward higher serum NfL levels.

CONCLUSION

Sleep disorders correlate with higher serum NfL, suggesting a link to PD neuronal damage. Early identification of sleep disorders and NfL monitoring are pivotal in detecting at-risk PD patients promptly, allowing for timely intervention. Regular monitoring of NfL levels holds promise for tracking both sleep disorders and disease progression, potentially emerging as a biomarker for evaluating treatment outcomes.

Free-Water Imaging of the Nucleus Basalis of Meynert in Patients With Idiopathic REM Sleep Behavior Disorder and Parkinson Disease

BACKGROUND AND OBJECTIVES

Cognitive impairments are common in idiopathic REM sleep behavior disorder (iRBD), in which the cholinergic degeneration of nucleus basalis of Meynert (NBM) may play an important role. However, the progressive changes of NBM, the relationship between progressive NBM degeneration and progression of cognitive impairments, and whether degeneration of the NBM can predict cognitive decline in patients with iRBD remain unclear. This study aimed to investigate the cross-sectional and longitudinal microstructural alterations in the NBM of patients with iRBD using free-water imaging and whether free water in the NBM is related to cognitive, mood, and autonomic function.

METHODS

We compared the baseline free-water values in the NBM between 59 healthy controls (HCs), 57 patients with iRBD, 57 patients with Parkinson disease (PD) with normal cognition (PD-NC), and 64 patients with PD with cognitive impairment (PD-CI). Thirty patients with iRBD and 40 HCs had one longitudinal data. In patients with iRBD, we explored the associations between baseline and longitudinal changes of free-water values in the NBM and clinical characteristics and whether baseline free-water values in the NBM could predict cognitive decline.

RESULTS

IRBD, PD-NC, and PD-CI groups had significantly increased free-water values in the NBM compared with HCs, whereas PD-CI had higher free-water values compared with iRBD and PD-NC. In patients with iRBD, free-water values in the NBM were progressively elevated over follow-up and correlated with the progression of cognitive impairment and depression. Free-water values in the NBM could predict cognitive decline in the iRBD group. Furthermore, we found that patients with iRBD with cognitive impairment had higher relative change of free-water value in the NBM compared with patients with iRBD with normal cognition over follow-up.

DISCUSSION

This study proves that free-water values in the NBM are elevated cross-sectionally and longitudinally and are associated with the progression of cognitive impairment and depression in patients with iRBD. Moreover, the free-water value in the NBM can predict cognitive decline in patients with iRBD. Whether free-water imaging of the NBM has the potential to be a marker for monitoring progressive cognitive impairment and predicting the conversion to dementia in synucleinopathies needs further investigation.

Relationship of Sleep Disorder with Neurodegenerative and Psychiatric Diseases: An Updated Review

Sleep disorders affect many people worldwide and can accompany neurodegenerative and psychiatric diseases. Sleep may be altered before the clinical manifestations of some of these diseases appear. Moreover, some sleep disorders affect the physiological organization and function of the brain by influencing gene expression, accelerating the accumulation of abnormal proteins, interfering with the clearance of abnormal proteins, or altering the levels of related hormones and neurotransmitters, which can cause or may be associated with the development of neurodegenerative and psychiatric diseases. However, the detailed mechanisms of these effects are unclear. This review mainly focuses on the relationship between and mechanisms of action of sleep in Alzheimer's disease, depression, and anxiety, as well as the relationships between sleep and Parkinson's disease, Huntington's disease, and amyotrophic lateral sclerosis. This summary of current research hotspots may provide researchers with better clues and ideas to develop treatment solutions for neurodegenerative and psychiatric diseases associated with sleep disorders.

Neuropsychological Changes in Isolated REM Sleep Behavior Disorder: A Systematic Review and Meta-analysis of Cross-sectional and Longitudinal Studies

The aim of this meta-analysis is twofold: (a) to assess cognitive impairments in isolated rapid eye movement (REM) sleep behavior disorder (iRBD) patients compared to healthy controls (HC); (b) to quantitatively estimate the risk of developing a neurodegenerative disease in iRBD patients according to baseline cognitive assessment. To address the first aim, cross-sectional studies including polysomnography-confirmed iRBD patients, HC, and reporting neuropsychological testing were included. To address the second aim, longitudinal studies including polysomnography-confirmed iRBD patients, reporting baseline neuropsychological testing for converted and still isolated patients separately were included. The literature search was conducted based on PRISMA guidelines and the protocol was registered at PROSPERO (CRD42021253427). Cross-sectional and longitudinal studies were searched from PubMed, Web of Science, Scopus, and Embase databases. Publication bias and statistical heterogeneity were assessed respectively by funnel plot asymmetry and using I2. Finally, a random-effect model was performed to pool the included studies. 75 cross-sectional (2,398 HC and 2,460 iRBD patients) and 11 longitudinal (495 iRBD patients) studies were selected. Cross-sectional studies showed that iRBD patients performed significantly worse in cognitive screening scores (random-effects (RE) model = -0.69), memory (RE model = -0.64), and executive function (RE model = -0.50) domains compared to HC. The survival analyses conducted for longitudinal studies revealed that lower executive function and language performance, as well as the presence of mild cognitive impairment (MCI), at baseline were associated with an increased risk of conversion at follow-up. Our study underlines the importance of a comprehensive neuropsychological assessment in the context of iRBD.

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.

Altered Impulsivity Across Drug-Naïve Parkinsonism, Isolated Rapid Eye Movement Sleep Behavior Disorder, and Their High-Risk Relatives

OBJECTIVE

To determine multidimensional impulsivity levels across different early stages of α-synucleinopathy.

METHODS

This cross-sectional study investigated motor and decisional impulsivity levels using a panel of computerized tasks among drug-naïve parkinsonism patients, isolated/idiopathic rapid eye movement sleep behavior disorder (iRBD) patients and their first-degree relatives (iRBD-FDRs), and control participants. Trait impulsivity and impulse control behaviors were assessed by self-reported questionnaires.

RESULTS

A total of 27 drug-naïve parkinsonism patients, 157 iRBD patients, 66 iRBD-FDRs, and 82 control participants were recruited. Parkinsonism and iRBD patients had fewer numbers of extracted beads in beads task 1 and 2 (both p < 0.001), and a higher rate of irrational choice in task 1 (p = 0.046) before making decisions, and fewer numbers of pumps of unexploded blue balloons in the balloon analog risk task (p = 0.004) than control participants, indicating a higher level of reflection impulsivity and a lower level of risk taking, respectively. iRBD patients had more no-go errors in the go/no-go task than control participants (padjusted  = 0.036), suggesting a higher level of motor impulsivity. iRBD-FDRs with dream-enactment behaviors had fewer numbers of extracted beads (p = 0.047) in beads task 2 than FDRs without dream-enactment behaviors, suggesting a possible higher level of reflection impulsivity.

INTERPRETATION

A complex construct of altered impulsivity with decreased risk taking, but increased reflection and motor impulsivity, has already occurred at the prodromal and early stages of α-synucleinopathy, which have implications for underlying pathophysiology and clinical management of α-synucleinopathy, especially for impulse control behaviors upon dopaminergic drug treatment. ANN NEUROL 2024;95:544-557.

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.