REM sleep behaviour disorder: an early window for prevention in neurodegeneration?

Cognitive training and promoting a healthy lifestyle for individuals with isolated REM sleep behavior disorder: study protocol of the delayed-start randomized controlled trial CogTrAiL-RBD

BACKGROUND

Isolated REM sleep behavior disorder (iRBD) is an early α-synucleinopathy often accompanied by incipient cognitive impairment. As executive dysfunctions predict earlier phenotypic conversion from iRBD to Parkinson's disease and Lewy body dementia, cognitive training focusing on executive functions could have disease-modifying effects for individuals with iRBD.

METHODS

The study CogTrAiL-RBD investigates the short- and long-term effectiveness and the feasibility and underlying neural mechanisms of a cognitive training intervention for individuals with iRBD. The intervention consists of a 5-week digital cognitive training accompanied by a module promoting a healthy, active lifestyle. In this monocentric, single-blinded, delayed-start randomized controlled trial, the intervention's effectiveness will be evaluated compared to an initially passive control group that receives the intervention in the second, open-label phase of the study. Eighty individuals with iRBD confirmed by polysomnography will be consecutively recruited from the continuously expanding iRBD cohort at the University Hospital Cologne. The evaluation will focus on cognition and additional neuropsychological and motor variables. Furthermore, the study will examine the feasibility of the intervention, effects on physical activity assessed by accelerometry, and interrogate the intervention's neural effects using magnetic resonance imaging and polysomnography. Besides, a healthy, age-matched control group (HC) will be examined at the first assessment time point, enabling a cross-sectional comparison between individuals with iRBD and HC.

DISCUSSION

This study will provide insights into whether cognitive training and psychoeducation on a healthy, active lifestyle have short- and long-term (neuro-)protective effects for individuals with iRBD.

TRIAL REGISTRATION

The study was prospectively registered in the German Clinical Trial Register (DRKS00024898) on 2022-03-11, https://drks.de/search/de/trial/DRKS00024898 .

PROTOCOL VERSION

V5 2023-04-24.

Role of sleep in neurodegeneration: the consensus report of the 5th Think Tank World Sleep Forum

Sleep abnormalities may represent an independent risk factor for neurodegeneration. An international expert group convened in 2021 to discuss the state-of-the-science in this domain. The present article summarizes the presentations and discussions concerning the importance of a strategy for studying sleep- and circadian-related interventions for early detection and prevention of neurodegenerative diseases. An international expert group considered the current state of knowledge based on the most relevant publications in the previous 5 years; discussed the current challenges in the field of relationships among sleep, sleep disorders, and neurodegeneration; and identified future priorities. Sleep efficiency and slow wave activity during non-rapid eye movement (NREM) sleep are decreased in cognitively normal middle-aged and older adults with Alzheimer's disease (AD) pathology. Sleep deprivation increases amyloid-β (Aβ) concentrations in the interstitial fluid of experimental animal models and in cerebrospinal fluid in humans, while increased sleep decreases Aβ. Obstructive sleep apnea (OSA) is a risk factor for dementia. Studies indicate that positive airway pressure (PAP) treatment should be started in patients with mild cognitive impairment or AD and comorbid OSA. Identification of other measures of nocturnal hypoxia and sleep fragmentation could better clarify the role of OSA as a risk factor for neurodegeneration. Concerning REM sleep behavior disorder (RBD), it will be crucial to identify the subset of RBD patients who will convert to a specific neurodegenerative disorder. Circadian sleep-wake rhythm disorders (CSWRD) are strong predictors of caregiver stress and institutionalization, but the absence of recommendations or consensus statements must be considered. Future priorities include to develop and validate existing and novel comprehensive assessments of CSWRD in patients with/at risk for dementia. Strategies for studying sleep-circadian-related interventions for early detection/prevention of neurodegenerative diseases are required. CSWRD evaluation may help to identify additional biomarkers for phenotyping and personalizing treatment of neurodegeneration.

REM Sleep Behavior Disorder and Its Possible Prodromes in General Population: Prevalence, Polysomnography Findings, and Associated Factors

BACKGROUND AND OBJECTIVES

To evaluate the prevalence of REM sleep behavior disorder (RBD) and its possible prodromal conditions, isolated dream enactment behavior (DEB) and isolated REM without atonia (RWA), in a general population sample, and the factors associated with diagnosis and symptom frequency.

METHODS

From a population-based prospective cohort in Korea, 1,075 participants (age 60.1 ± 7.0 years; range 50-80 years; men 53.7%) completed the RBD screening questionnaire (RBDSQ), a structured telephone interview for the presence and characteristics of repeated DEB, and home polysomnography (PSG). RWA was measured on submentalis EMG, including 30-second epoch-based tonic and phasic activity as well as 3-second mini-epoch-based phasic and any EMG activities. Based on the presence of repeated DEB and any EMG activity of ≥22.3%, we categorized the participants into no RBD, isolated RWA, isolated DEB, and RBD groups.

RESULTS

RBD was diagnosed in 20 participants, isolated RWA in 133 participants, and isolated DEB in 48 participants. Sex and DEB frequency-adjusted prevalence of RBD was 1.4% (95% CI 1.0%-1.8%), isolated RWA was 12.5% (95% CI 11.3%-13.6%), and isolated DEB was 3.4% (95% CI 2.7%-4.1%). Total RBDSQ score was higher in the RBD and isolated DEB groups than in the isolated RWA and no RBD group (median 5 [interquartile range (IQR) 4-6] for RBD, median 4 [IQR 3-6] for isolated DEB, median 2 [IQR 1-3] for isolated RWA, and median 2 [IQR 1-4] for no RBD groups, p < 0.001). RBDSQ score of ≥5 had good specificity but poor positive predictive value (PPV) for RBD (specificity 84.1% and PPV 7.7%) and its prodromal conditions (specificity 85.2% and PPV 29.1%). Among the RWA parameters, any EMG activity showed the best association with the RBD and its possible prodromes (area under the curve, 0.917). Three-second mini-epoch-based EMG activity and phasic EMG activity were correlated with the frequency of DEB (standardized Jonckheere-Terpstra statistic [std. J-T static] for trend = 0.488, p < 0.001, and std. J-T static = 3.265, p = 0.001, respectively).

DISCUSSION

This study provides prevalence estimates of RBD and its possible prodromal conditions based on a structured telephone interview and RWA measurement on PSG from the general population.

Former participation in professional football as an occupation in patients with isolated REM sleep behavior disorder leading to a synucleinopathy: a case-control study

BACKGROUND

Contact sports such as football are associated with late development of neurodegenerative diseases, in part due to the deleterious effect of repetitive head impacts during participation. Isolated REM sleep behavior disorder (IRBD) represents an early manifestation of neurodegenerative diseases including Parkinson disease (RBD) and dementia with Lewy bodies (DLB). We hypothesized that former professional football participation would be overrepresented in IRBD.

OBJECTIVE

To assess former participation in professional football as an occupation in IRBD.

METHODS

In a case-control retrospective study, having played football as a professional occupation in the Spanish Football Professional Leagues was examined interviewing polysomnographically confirmed IRBD patients and matched controls without IRBD.

RESULTS

Among 228 Caucasian Spanish IRBD patients with 68.5 ± 7.2 years, six (2.63%) were retired professional footballers. Length professional football career ranged between 11 and 16 years. Interval between football retirement and IRBD diagnosis was 39.5 ± 6.4 years. At IRBD diagnosis, the six footballers had synucleinopathy biomarkers including pathologic synuclein in the CSF and tissues, nigrostriatal dopaminergic deficit and hyposmia. Follow-up showed that three footballers developed PD and two DLB. None of the controls was a professional footballer. The percentage of professional footballers was higher in IRBD patients than in controls (2.63% versus 0.00%; p = 0.030) and among the general Spanish population (2.63% versus 0.62%; p < 0.0001).

CONCLUSION

We found an overrepresentation of former professional footballers in IRBD patients who later developed PD and DLB after four decades from professional retirement. In professional footballers the development of a neurodegenerative disease may be first manifested by IRBD. Screening for IRBD in former footballers might identify individuals with underlying synucleinopathies. Further studies with larger samples are needed to confirm our observations.

α-Synuclein Induced the Occurrence of RBD via Interaction with OX1R and Modulated Its Degradation

Rapid eye movement (REM) sleep behavior disorder (RBD) is a powerful early sign of Parkinson's disease (PD), but the pathogenetic mechanism involved in RBD remains largely unexplored. α-Synuclein has been verified to form Lewy bodies in the orexin neurons, whose activity and function rely on the orexin 1 receptor (OX1R). Dysfunction of the OX1R may induce the occurrence of RBD. Here, we determined the role of the interaction between α-Synuclein and OX1R in the pathogenesis of RBD, in vitro and in vivo. We found that injection of α-Synuclein into the lateral hypothalamus area (LHA) damaged orexin neurons and induced the RBD-like sleep pattern, to further damage dopaminergic neurons and result in locomotor dysfunction in mice. α-Synuclein interacted with OX1R, promoting the degradation of OX1R through proteasomal and lysosomal pathways. In addition, overexpression of α-Synuclein downregulated OX1R-mediated signaling, subsequently leading to orexin neuron damage. We conclude that α-Synuclein induced the occurrence of RBD via interaction with OX1R and modulated its degradation. These findings provide evidence for a novel mechanism by which the association of α-Synuclein with OX1R was attributed to α-Synuclein-induced orexin neuron damage, which may be a new molecular target for an effective therapeutic strategy for RBD pathology.

Prevalence of isolated RBD in the city of Catania, Italy: a population-based study

STUDY OBJECTIVES

Few studies have analyzed the prevalence of isolated REM sleep behavior disorder (RBD) giving different estimates. Aim of the study was to estimate the prevalence of isolated RBD in the city of Catania.

METHODS

A three-stage design was adopted. Participants attending the cabinets of General Practitioners in the city of Catania were screened with the RBD1Q questionnaire (Stage I). Positive participants were interviewed by phone and if suspected of RBD, were invited for clinical examination by a movement disorders specialist and a sleep specialist (Stage II). After the clinical examination, patients diagnosed as probable isolated RBD (pRBD) were invited to undergo a video polysomnography (VPSG) (Stage III) to confirm the diagnosis of definite RBD (dRBD).

RESULTS

A total of 1,524 participants have been screened. Of these, 220 (14.4%) screened positive. One-hundred-forty-three of them were further screened by phone, of whom 75 were suspected RBD. Thirty-six patients were diagnosed as pRBD giving a prevalence of 2.36% (95%CI 1.71-3.25). Twelve pRBD agreed to a VPSG and, of these, four were diagnosed as dRBD giving a prevalence of 0.26% (95%CI 0.07-0.67). Prevalence adjusted by non-participants was 3.48% (95%CI 2.67-4.52) and 1.18% (95%CI 0.45-1.37) for pRBD and dRBD respectively.

CONCLUSIONS

Prevalence of both pRBD and dRBD in Italy is comparable to the estimates reported in literature, confirming that isolated RBD has a low prevalence in the general population.

Sleep Disturbance, Sleep Disorders and Co-Morbidities in the Care of the Older Person

Sleep complaints can be both common and complex in the older patient. Their consideration is an important aspect of holistic care, and may have an impact on quality of life, mortality, falls and disease risk. Sleep assessment should form part of the comprehensive geriatric assessment. If sleep disturbance is brought to light, consideration of sleep disorders, co-morbidity and medication management should form part of a multifaceted approach. Appreciation of the bi-directional relationship and complex interplay between co-morbidity and sleep in older patients is an important element of patient care. This article provides a brief overview of sleep disturbance and sleep disorders in older patients, in addition to their association with specific co-morbidities including depression, heart failure, respiratory disorders, gastro-oesophageal reflux disease, nocturia, pain, Parkinson's disease, dementia, polypharmacy and falls. A potential systematic multidomain approach to assessment and management is outlined, with an emphasis on non-pharmacological treatment where possible.

The Isolated Form of Rapid Eye Movement Sleep Behavior Disorder: The Upcoming Challenges

The diagnosis of rapid eye movement (REM) sleep behavior disorder (SBD) requires videopolysomnography detection of excessive electromyographic activity during REM sleep, which is time consuming and difficult. An easier, faster, reliable, and reproducible methodology is needed for its diagnosis. The isolated form of RBD represents an early manifestation of the synucleinopathies Parkinson disease and dementia with Lewy bodies. There is a need to find neuroprotective drugs capable of preventing parkinsonism and dementia onset in isolated RBD. Clonazepam and melatonin ameliorate the RBD symptoms, but therapeutic alternatives are needed when these medications fail or show produce side effects.

From sleep medicine to medicine during sleep-a clinical perspective

Objective. In this perspective paper, we aim to highlight the potential of sleep as an auspicious time for diagnosis, management and therapy of non-sleep-specific pathologies.Approach. Sleep has a profound influence on the physiology of body systems and biological processes. Molecular studies have shown circadian-regulated shifts in protein expression patterns across human tissues, further emphasizing the unique functional, behavioral and pharmacokinetic landscape of sleep. Thus, many pathological processes are also expected to exhibit sleep-specific manifestations. Modern advances in biosensor technologies have enabled remote, non-invasive recording of a growing number of physiologic parameters and biomarkers promoting the detection and study of such processes.Main results. Here, we introduce key clinical studies in selected medical fields, which leveraged novel technologies and the advantageous period of sleep to diagnose, monitor and treat pathologies. Studies demonstrate that sleep is an ideal time frame for the collection of long and clean physiological time series data which can then be analyzed using data-driven algorithms such as deep learning.Significance.This new paradigm proposes opportunities to further harness modern technologies to explore human health and disease during sleep and to advance the development of novel clinical applications - from sleep medicine to medicine during sleep.

Magnetic resonance imaging abnormalities as a marker of multiple system atrophy in isolated rapid eye movement sleep behavior disorder

STUDY OBJECTIVES

Patients with isolated rapid eye movement (REM) sleep behavior disorder (IRBD) develop Parkinson disease (PD), dementia with Lewy bodies (DLB), or multiple system atrophy (MSA). Magnetic resonance imaging (MRI) is abnormal in MSA showing abnormalities in the putamen, cerebellum, and brainstem. Our objective was to evaluate the usefulness of MRI to detect MRI abnormalities in IRBD and predict development of MSA and not PD and DLB.

METHODS

In IRBD patients that eventually developed PD, DLB, and MSA, we looked for the specific structural MRI abnormalities described in manifest MSA (e.g. hot cross-bun sign, putaminal rim, and cerebellar atrophy). We compared the frequency of these MRI changes among groups of converters (PD, DLB, and MSA) and analyzed their ability to predict development of MSA. The clinical and radiological features of the IRBD patients that eventually converted to MSA are described in detail.

RESULTS

A total of 61 IRBD patients who underwent MRI phenoconverted to PD (n = 30), DLB (n = 26), and MSA (n = 5) after a median follow-up of 2.4 years from neuroimaging. MRI changes typical of MSA were found in four of the five (80%) patients who converted to MSA and in three of the 56 (5.4%) patients who developed PD or DLB. MRI changes of MSA had sensitivity of 80.0%, specificity of 94.6%, positive likelihood ratio of 14.9 (95% CI 4.6-48.8), and negative likelihood ratio of 0.2 (95% CI 0.04-1.2) to predict MSA.

CONCLUSIONS

In IRBD, conventional brain MRI is helpful to predict conversion to MSA. The specific MRI abnormalities of manifest MSA may be detected in its premotor stage.

Detection of α-synuclein in CSF by RT-QuIC in patients with isolated rapid-eye-movement sleep behaviour disorder: a longitudinal observational study

BACKGROUND

Isolated rapid-eye-movement (REM) sleep behaviour disorder (IRBD) can be part of the prodromal stage of the α-synucleinopathies Parkinson's disease and dementia with Lewy bodies. Real-time quaking-induced conversion (RT-QuIC) analysis of CSF has high sensitivity and specificity for the detection of misfolded α-synuclein in patients with Parkinson's disease and dementia with Lewy bodies. We investigated whether RT-QuIC could detect α-synuclein in the CSF of patients with IRBD and be used as a biomarker of prodromal α-synucleinopathy.

METHODS

In this longitudinal observational study, CSF samples were obtained by lumbar puncture from patients with video polysomnography-confirmed IRBD recruited at a specialised sleep disorders centre in Barcelona, Spain, and from controls free of neurological disease. CSF samples were stored until analysed using RT-QuIC. After lumbar puncture, participants were assessed clinically for neurological status every 3-12 months. Rates of neurological disease-free survival were estimated using the Kaplan-Meier method. Disease-free survival rates were assessed from the date of lumbar puncture to the date of diagnosis of any neurodegenerative disease, or to the last follow-up visit for censored observations.

FINDINGS

52 patients with IRBD and 40 healthy controls matched for age (p=0·20), sex (p=0·15), and duration of follow-up (p=0·27) underwent lumbar puncture between March 23, 2008, and July 16, 2017. The CSF α-synuclein RT-QuIC assay was positive in 47 (90%) patients with IRBD and in four (10%) controls, resulting in a sensitivity of 90·4% (95% CI 79·4-95·8) and a specificity of 90·0% (95% CI 76·9-96·0). Mean follow-up from lumbar puncture until the end of the study (July 31, 2020) was 7·1 years (SD 2·8) in patients with IRBD and 7·7 years (2·9) in controls. During follow-up, 32 (62%) patients were diagnosed with Parkinson's disease or dementia with Lewy bodies a mean 3·4 years (SD 2·6) after lumbar puncture, of whom 31 (97%) were α-synuclein positive at baseline. Kaplan-Meier analysis showed that patients with IRBD who were α-synuclein negative had lower risk for developing Parkinson's disease or dementia with Lewy bodies at 2, 4, 6, 8, and 10 years of follow-up than patients with IRBD who were α-synuclein positive (log-rank test p=0·028; hazard ratio 0·143, 95% CI 0·019-1·063). During follow-up, none of the controls developed an α-synucleinopathy. Kaplan-Meier analysis showed that participants who were α-synuclein negative (ie, five patients with IRBD plus 36 controls) had lower risk of developing Parkinson's disease or dementia with Lewy bodies at 2, 4, 6, 8 and 10 years after lumbar puncture than participants who were α-synuclein positive (ie, 47 patients with IRBD plus four controls; log-rank test p<0·0001; hazard ratio 0·024, 95% CI 0·003-0·177).

INTERPRETATION

In patients with IRBD, RT-QuIC detects misfolded α-synuclein in the CSF with both sensitivity and specificity of 90%, and α-synuclein positivity was associated with increased risk of subsequent diagnosis of Parkinson's disease or dementia with Lewy bodies. Detection of α-synuclein in the CSF represents a potential prodromal marker of Parkinson's disease and dementia with Lewy bodies. If these findings are replicated in additional cohorts, detection of CSF α-synuclein by RT-QuIC could be used to enrich IRBD cohorts in neuroprotective trials, particularly when assessing interventions that target α-synuclein.

FUNDING

Department of Health and Social Care Policy Research Programme, the Scottish Government, and the Weston Brain Institute.

Propagated α-synucleinopathy recapitulates REM sleep behaviour disorder followed by parkinsonian phenotypes in mice

Idiopathic rapid eye movement sleep behaviour disorder (RBD) is now recognized as an early manifestation of α-synucleinopathies. Increasing experimental studies demonstrate that manipulative lesion or inactivation of the neurons within the sublaterodorsal tegmental nucleus (also known as the subcoeruleus nucleus in humans) can induce RBD-like behaviours in animals. As current RBD animal models are not established on the basis of α-synucleinopathy, they do not represent the pathological substrate of idiopathic RBD and thus cannot model the phenoconversion to Parkinson's disease. The purpose of this study was therefore to establish an α-synucleinopathy-based RBD animal model with the potential to convert to parkinsonian disorder. To this end, we first determined the functional neuroanatomical location of the sublaterodorsal tegmental nucleus in wild-type C57BL/6J mice and then validated its function by recapitulating RBD-like behaviours based on this determined nucleus. Next, we injected preformed α-synuclein fibrils into the sublaterodorsal tegmental nucleus and performed regular polysomnographic recordings and parkinsonian behavioural and histopathological studies in these mice. As a result, we recapitulated RBD-like behaviours in the mice and further showed that the α-synucleinopathy and neuron degeneration identified within the sublaterodorsal tegmental nucleus acted as the neuropathological substrates. Subsequent parkinsonian behavioural studies indicated that the α-synucleinopathy-based RBD mouse model were not stationary, but could further progress to display parkinsonian locomotor dysfunction, depression-like disorder, olfactory dysfunction and gastrointestinal dysmotility. Corresponding to that, we determined α-synuclein pathology in the substantia nigra pars compacta, olfactory bulb, enteral neuroplexus and dorsal motor nucleus of vagus nerve, which could underlie the parkinsonian manifestations in mice. In conclusion, we established a novel α-synucleinopathy-based RBD mouse model and further demonstrated the phenoconversion of RBD to Parkinson's disease in this animal model.

The connectivity between the olfactory and auditory cortex predicts an individual's sleep quality

Sleep disorders and multiple sensory impairments have been noticed as the potential first sign of neurodegenerative diseases such as the Parkinson disease. The relationship between sleep quality and the sensory neural basis would help us consider their combination in early diagnosis. In the present study, 32 out of 45 healthy subjects' resting-state functional magnetic resonance imaging data survived from motion correction and entered into the connectivity analysis. We found that the connectivity between two regions of interest (the left olfactory gyrus and the left superior temporal pole) and the regional homogeneity in the left middle temporal gyrus were negatively correlated with their Pittsburgh sleep quality index. These results suggest that these sensory-related brain regions are related to sleep quality and they may together predict the diseases.

Significance of hyposmia in isolated REM sleep behavior disorder

OBJECTIVE

To determine if hyposmia in isolated REM sleep behavior disorder (IRBD) predicts short-term conversion to any α-synucleinopathy and declines with time.

METHODS

Olfaction was tested using the University of Pennsylvania Smell Identification Test (UPSIT-40) in 140 consecutive patients with polysomnography-confirmed IRBD and in 77 matched controls. Patients were followed-up during 5.6 ± 3.9 (range 0.2-13) years. Twenty-one patients underwent serial UPSIT-40 evaluations at 1-3 and 4-6 years after baseline.

RESULTS

UPSIT-40 score was lower in patients than in controls (20.2 ± 6.5 vs. 28.6 ± 5.0; p < 0.001). Hyposmia (UPSIT-40 score < 19 points) occurred in 42.9% patients. Forty-three (30.7%) patients developed Parkinson disease (PD = 27), dementia with Lewy bodies (DLB = 13) and multiple system atrophy (MSA = 3). Kaplan-Meier analysis showed that hyposmics had higher risk than normosmics to develop a synucleinopathy at the short term (p = 0.030). UPSIT-40 score was similar between patients who developed PD and DLB (p = 0.136). Normal smell occurred in all three (100%) IRBD patients who developed MSA, 12 of 27 (44%) who developed PD, and 4 of 13 (31%) that developed DLB. Serial UPSIT-40 evaluations showed no changes with time (p = 0.518).

CONCLUSION

In IRBD, hyposmia is a short-term risk for synucleinopathies but cannot distinguish underlying PD from DLB. Normosmia not only occurs in latent MSA but also in latent PD and DLB. In future IRBD neuroprotective trails, individuals at entry could be enriched for hyposmia, whereas serial evaluation of smell would not be useful to monitor the efficacy of a therapeutic intervention.