REM sleep behavior disorder as a complex condition with heterogeneous underlying disorders: clinical management and prognostic implications [Commentary]

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

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

Sleep-Related Disorders in Parkinson's Disease: Mechanisms, Diagnosis, and Therapeutic Approaches

BACKGROUND

Parkinson's Disease (PD) is frequently associated with a spectrum of sleep-related disorders, including insomnia, Excessive Daytime Sleepiness (EDS), REM sleep Behaviour Disorder (RBD), Restless Legs Syndrome (RLS), and Sleep-related Breathing Disorders (SBDs). These disorders significantly impact PD patients' Quality of Life (QoL) and present unique diagnostic and therapeutic challenges.

METHODS

This review has explored the intricate relationship between PD and sleep-related disorders, emphasizing their distinctive features and underlying neurobiological mechanisms. It aimed to consolidate current knowledge to optimize clinical management and improve patient care. The profound impact of these disorders on QoL has been evaluated, along with precise diagnostic methodologies. Additionally, various therapeutic strategies, including pharmacological treatments, nonpharmacological interventions, and device-aided therapies, have been examined.

RESULTS

Sleep-related disorders are prevalent among PD patients. Specifically, RBD exhibits a prevalence of 40-50%, often preceding the onset of motor symptoms, indicating its potential as an early marker of PD. Despite their significant impact on QoL, these non-motor symptoms are frequently under-recognized and inadequately managed in clinical practice. Pharmacological treatments, along with nonpharmacological interventions, like cognitive-behavioral therapy for insomnia and lifestyle modifications, have shown varied efficacy. Device-aided therapies have also demonstrated the potential to improve sleep-related disorders and overall non-motor symptom burden.

CONCLUSION

Effective management of sleep-related disorders in PD calls for personalized, comprehensive, and multimodal therapeutic approaches. This requires the collaborative efforts of neurologists, sleep specialists, psychiatrists, and other healthcare professionals. Future research should focus on the intricate relationship between PD and sleep disorders, aiming to develop innovative treatments and significantly improve patient outcomes.

Network structure of REM sleep behavior disorder symptoms in iRBD patients

OBJECTIVE

Employing the REM Sleep Behavior Disorder Questionnaire-Hong Kong (RBDQ-HK) to investigate symptoms and their severity in rapid eye movement (REM) sleep behavior disorder (RBD) patients, this study delves into the construct of RBD through the RBDQ-HK and its links to depression and sleep quality.

METHODS

Data from the RBDQ-HK, the Geriatric Depression Scale (GDS), and the Pittsburgh Sleep Quality Index (PSQI) were compiled from individuals with isolated RBD (iRBD) confirmed by polysomnography. We constructed a network analysis of the RBDQ-HK, measured the centrality of each symptom (node), conducted Exploratory Graph Analysis (EGA) to unveil the dimension structure of the questionnaire, and calculated bridge expected influence (BEI) to identifying critical bridge. Multivariate linear regression was also employed to discover relationships between RBDQ-HK dimensions and variables such as PSQI and GDS.

RESULTS

In our cohort of 455 iRBD patients (299 males), the items in the RBDQ-HK were divided into three dimensions: dream, movement, and SRI/violence. The symptoms identified as most central to RBD were 'shouting or yelling in sleep', 'dream-enacting movements', and 'talking during sleep'. The highest (BEI) was 'violent and aggressive dreams', which has the potential to bridge three dimensions within the symptom network. Depression was significantly correlated with the movement and dream dimensions of RBD, and sleep quality was predominantly related to the dream dimension score.

CONCLUSION

Our findings verify that the principal symptoms of the RBDQ-HK align with the established diagnostic criteria and reveal a three-dimensional structure within RBD symptoms. The relationships between the RBD symptoms, depression, and sleep quality need to be identified for the effective management of RBD patients.

Prevalence and characteristics of rapid eye movement sleep behaviour disorder in adults with migraine: a cross-sectional screening study

BACKGROUND AND PURPOSE

Migraine and sleep disorders share a bidirectional relationship, but little is known about the specific association between migraine and rapid eye movement (REM) sleep behaviour disorder (RBD). The aim was to assess the prevalence of RBD and associated clinical characteristics in adults with migraine.

METHODS

This analysis is part of a cross-sectional survey study conducted at the Headache Centre of the Charité-Universitätsmedizin Berlin between August 2020 and March 2023. At the end of their regular medical consultation, patients with migraine filled out (1) the validated RBD Screening Questionnaire (RBDSQ), (2) a questionnaire on REM sleep intrusions and (3) the Depression, Anxiety and Stress Scale 21. The primary endpoint was the percentage of patients with a positive RBD screening. A multivariate analysis was performed to identify characteristics independently associated with features of RBD.

RESULTS

A total of 751 patients (44.1 ± 13.2 years; 87.4% female) with complete RBDSQ were included in this analysis, of which 443 (58.9%) screened positive for RBD. In multivariate analysis, a positive screening for RBD was associated with younger age (odds ratio [OR] 0.9, 95% confidence interval [CI] 0.8-0.9 per 10-year increase; p = 0.005) and with features suggestive of REM sleep intrusions (OR 4.3, 95% CI 1.8-10.4; p = 0.001). Migraine aura remained in the model without reaching statistical significance (OR 1.3, 95% CI 0.9-1.8; p = 0.079).

DISCUSSION

Symptoms of RBD are frequent in adults with migraine. Further studies including polysomnography are required to confirm this association, and to explore potential common pathophysiological mechanisms.

Polysomnographic features prior to dream enactment behaviors in isolated rapid eye movement sleep behavior disorder

OBJECTIVE

This study aimed to identify electroencephalogram correlates of dream enactment behaviors (DEBs) and elucidate their cortical dynamics in patients with isolated/idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD).

METHODS

This cross-sectional study included 15 patients with iRBD. Two REM sleep periods in routine polysomnography were compared: the 60 s preceding the DEBs ("pre-representative behavior" [preR]), and the 60 s with the least submental electromyogram activity ("background" [BG]). Six EEG frequency bands and electrooculogram were analyzed; power spectra, coherence and phase-locking values in four 15-s periods were examined to assess trends. These indices were also compared between preR and BG.

RESULTS

Compared with BG, significantly higher delta power in the F3 channel and gamma power in the F4 and O2 channels were observed during preR. For functional connectivity, the widespread beta-band connectivity was significantly increased during preR than BG.

CONCLUSION

Before notable REM sleep behaviors, uneven distributed higher EEG spectral power in both very low and high frequencies, and increased wide-range beta band functional connectivity, were observed over 60 s, suggesting cortical correlates to subsequent DEBs.

SIGNIFICANCE

This study may shed light on the pathological mechanisms underlies RBD through the routine vPSG analysis, leading to detection of DEBs.

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.

Secondary RBD: Not just neurodegeneration

Rapid eye movement sleep behavior disorder is a parasomnia characterized by excessive muscle activity during rapid eye movement sleep (rapid eye movement sleep without atonia), along with dream enactment behavior. Isolated rapid eye movement sleep behavior disorder tends to occur in older males and is of concern due to the known link to Parkinson's disease and other synucleinopathies. When rapid eye movement sleep behavior disorder occurs in association with other neurological or general medical conditions, or resulting from the use of various substances, it is called secondary rapid eye movement sleep behavior disorder; the most common cause is neurodegenerative illness, specifically the synucleinopathies. Here, the focus will be on the subset of secondary rapid eye movement sleep behavior disorder in which there is no neurodegenerative disease.

Parasomnias manifest different phenotypes of sleep-related behaviors in age and sex groups. A YouTube-based video research highlighting the age slope of sleepwalking

STUDY OBJECTIVE

Finding typical patterns - phenotypes - of sleep behaviors characterizing parasomnias in different age and sex groups.

METHODS

We analyzed YouTube videos on sleep-related behaviors likely representing parasomnias. We applied the search terms "sleepwalking", "somnambulism", "sleep eating", "sleep sex", "sleep talking", and "aggression in sleep" in six languages. We classified those persons shown on the videos into estimated biological sex and age (child, adult, elderly) groups. We scored the activity types by a self-made scale and applied binary logistic regression to analyze the association between sleep behaviors versus sex and age groups by the STATA package, providing a 95% confidence interval and the probability of statistical significance.

RESULTS

224 videos (102 women, 68 children, 16 adults, and 40 elderly people) were scored. Elderly people had significantly (P < 0.012) lower odds of sleepwalking compared to adults and children. Adult females performed complex manual activities during sleepwalking more often than males (P < 0.012). Elderly males had 40-fold odds compared to adults and children, to perform aggressive movements and 70-fold odds of complex movements in bed, compared to adults. Elderly people presented emotional behaviors less frequently than adults (P < 0.004), and females showed them twice as often as males. Adults sleep-talked full sentences more often than children and elderly people (P < 0.001).

CONCLUSION

Our results support the existence of age- and sex-specific parasomnia phenotypes, denoting possible safety measures. The remarkably low odds of sleepwalking in the elderly highlight the possibility of different pathomechanisms in higher age groups compared to children.

BRIEF SUMMARY AND STUDY IMPACT

Parasomnias present highly variable clinical forms and often cause injuries. Identifying typical phenotypes may help risk management and imply theoretical conclusions. Our study supports the existence of age-specific parasomnia phenotypes. We found that adult women have a high risk of performing dangerous activities during sleep, and elderly males often move violently in bed, likely representing dream enactment behaviors. Elderly people of both sexes have low odds of sleep ambulation- likely representing somnambulism; compared to adults and children, constituting a descending "age slope" of somnambulism that might reflect different underlying pathomechanisms in children versus adults and the elderly.

The Clinical Spectrum of the Parasomnias

Parasomnias are defined as abnormal movements or behaviors that occur in sleep or during arousals from sleep. Parasomnias vary in frequency from episodic events that arise from incomplete sleep state transition. The framework by which parasomnias are categorized and diagnosed is based on the International Classification of Sleep Disorders-Third Edition, Text Revision (ICSD-3-TR), published by the American Academy of Sleep Medicine. The recent Third Edition, Text Revision (ICSD-3-TR) of the ICSD provides an expert consensus of the diagnostic requirements for sleep disorders, including parasomnias, based on an extensive review of the current literature.

Diagnosis and Management of NREM Sleep Parasomnias in Children and Adults

Non-rapid eye movement (NREM) sleep parasomnias are recurrent abnormal behaviors emerging as incomplete arousals out of NREM sleep. Mounting evidence on NREM sleep parasomnias calls for an update of clinical and therapeutical strategies. In the current review, we summarize the state of the art and provide the necessary background to stimulate a critical revision of diagnostic criteria of disorders of arousal (DoA), the most common NREM sleep parasomnia. In particular, we highlight the poor sensitivity of the diagnostic items related to amnesia and absence of conscious experiences during DoA episodes, encourage the role of video-polysomnography and home-video recordings in the diagnostic and treatment work-up, and suggest three levels of diagnostic certainty based on clinical and objective findings. Furthermore, we highlight current gaps of knowledge that prevent the definition of standard guidelines and future research avenues.