Parkinsonism with excessive daytime sleepiness

Exploring the role of Orexin-A neuropeptide in Parkinson's disease: A systematic review and meta-analysis

BACKGROUND

Parkinson's disease (PD) is a progressive neurological condition that affects movement and coordination. Orexin-A (OXA) is an excitatory neuropeptide that is found throughout the central nervous system. There is growing interest in investigating the potential diagnostic and therapeutic utility of OXA in PD. To date, studies have reported a wide range of OXA concentrations in patients with PD. In this review, we discuss the current understanding of the dysregulation of OXA in PD and analyze its levels in the CSF.

METHODS

We searched six databases (PubMed, Scopus, Web of Science, EMBASE, ProQuest, and EBSCOHost) and preprint servers using a predetermined search strategy through 4th March 4, 2023. The search keywords included "Parkinson's disease", "Orexin-A", "Hypocretin-1", "cerebrospinal fluid", and "CSF". Studies that reported OXA/Hypocretin-1 levels in the CSF of patients with PD were included. Two researchers independently reviewed the records and extracted data.

FINDINGS

Eighteen studies involving 244 patients were analyzed. CSF Orexin-A concentrations were lower in patients with Parkinson's disease than in controls, with a mean difference of -59.21 (95 % CI: -89.10 to -29.32). The mean OXA levels were 281.52 (95 % CI: 226.65-336.40).

CONCLUSION

Our analysis reveals lower concentrations of orexin-A in the cerebrospinal fluid of Parkinson's disease patients compared to controls, but within the normal range. These findings suggest a potential, but not significant, disruption in the orexinergic system associated with the disease.

The role of orexin in Parkinson's disease

Emerging evidence has implicated the orexin system in non-motor pathogenesis of Parkinson's disease. It has also been suggested the orexin system is involved in the modulation of motor control, further implicating the orexin system in Parkinson's disease. Parkinson's disease is the second most common neurodegenerative disease with millions of people suffering worldwide with motor and non-motor symptoms, significantly affecting their quality of life. Treatments are based solely on symptomatic management and no cure currently exists. The orexin system has the potential to be a treatment target in Parkinson's disease, particularly in the non-motor stage. In this review, the most current evidence on the orexin system in Parkinson's disease and its potential role in motor and non-motor symptoms of the disease is summarized. This review begins with a brief overview of Parkinson's disease, animal models of the disease, and the orexin system. This leads into discussion of the possible roles of orexin neurons in Parkinson's disease and levels of orexin in the cerebral spinal fluid and plasma in Parkinson's disease and animal models of the disease. The role of orexin is then discussed in relation to symptoms of the disease including motor control, sleep, cognitive impairment, psychological behaviors, and the gastrointestinal system. The neuroprotective effects of orexin are also summarized in preclinical models of the disease.

Targeting the orexin/hypocretin system for the treatment of neuropsychiatric and neurodegenerative diseases: from animal to clinical studies

Orexins (also known as hypocretins) are neuropeptides located exclusively in hypothalamic neurons that have extensive projections throughout the central nervous system and bind two different G protein-coupled receptors (OX1R and OX2R). Since its discovery in 1998, the orexin system has gained the interest of the scientific community as a potential therapeutic target for the treatment of different pathological conditions. Considering previous basic science research, a dual orexin receptor antagonist, suvorexant, was the first orexin agent to be approved by the US Food and Drug Administration to treat insomnia. In this review, we discuss and update the main preclinical and human studies involving the orexin system with several psychiatric and neurodegenerative diseases. This system constitutes a nice example of how basic scientific research driven by curiosity can be the best route to the generation of new and powerful pharmacological treatments.

Muscle atonia index during multiple sleep latency test: A possible marker to differentiate narcolepsy from other hypersomnias

OBJECTIVE

The complexity and delay of the diagnosis of narcolepsy require several diagnostic tests and invasive procedures such as lumbar puncture. Our study aimed to determine the changes in muscle tone (atonia index, AI) at different levels of vigilance during the entire multiple sleep latency test (MSLT) and each nap in people with narcolepsy type 1 (NT1) and 2 (NT2) compared with other hypersomnias and its potential diagnostic value.

METHODS

Twenty-nine patients with NT1 (11 M 18F, mean age 34.9 years, SD 16.8) and sixteen with NT2 (10 M 6F, mean age 39 years, SD 11.8) and 20 controls with other hypersomnias (10 M, 10F mean age 45.1 years, SD 15.1) were recruited. AI was evaluated at different levels of vigilance (Wake and REM sleep) in each nap and throughout the MSLT of each group. The validity of AI in identifying patients with narcolepsy (NT1 and NT2) was analyzed using receiver operating characteristic (ROC) curves.

RESULTS

AI during wakefulness (WAI) was significantly higher in the narcolepsy groups (NT1 and NT2 p < 0.001) compared to the hypersomniac group. AI during REM sleep (RAI) (p = 0.03) and WAI in nap with sudden onsets of REM sleep periods (SOREMP) (p = 0.001) were lower in NT1 than in NT2. The ROC curves showed high AUC values for WAI (NT1 0.88; Best Cut-off > 0.57, Sensitivity 79.3 % Specificity 90 %; NT2 0.89 Best Cut-off > 0.67 Sensitivity 87.5 % Specificity 95 %; NT1 and NT2 0.88 Best Cut-off > 0.57 Sensitivity 82.2 % Specificity 90 %) in discriminating subjects suffering from other hypersomnias. RAI and WAI in nap with SOREMP showed a poor AUC value (RAI AUC: 0.7 Best cutoff 0.7 Sensitivity 50 % Specificity 87.5 %; WAI in nap before SOREMP AUC: 0.66, Best cut-off < 0.82 sensitivity 61.9 % and specificity 67.35 %) differentiating NT1 and NT2.

CONCLUSIONS

WAI may represent an encouraging electrophysiological marker of narcolepsy and suggests a vulnerable tendency to dissociative wake / sleep dysregulation lacking in other forms of hypersomnia.

SIGNIFICANCE

AI during wakefulness may help distinguish between narcolepsy and other hypersomnias.

The mobile sleep medicine model in neurologic practice: Rationale and application

Background

Undiagnosed obstructive sleep apnea (OSA) is prevalent in neurological practice and significantly contributes to morbidity and mortality. OSA is prevalent in US adults and causes poor quality sleep and significant neurocognitive, cardiovascular, and cerebrovascular impairments. Timely treatment of OSA reduces cardio-cerebrovascular risks and improves quality of life. However, most of the US population has limited systematic access to sleep medicine care despite its clinical significance.

Focus

We discuss the importance of systematic screening, testing, and best-practice management of OSA and hypoventilation/hypoxemia syndromes (HHS) in patients with stroke, neurocognitive impairment, and neuromuscular conditions. This review aims to introduce and describe a novel integrated Mobile Sleep Medicine (iMSM) care model and provide the rationale for using an iMSM in general neurological practice to assist with systematic screening, testing and best-practice management of OSA, HHS, and potentially other sleep conditions.

Key points

The iMSM is an innovative, patient-centered, clinical outcome-based program that uses a Mobile Sleep Medicine Unit—a “sleep lab on wheels”—designed to improve access to OSA management and sleep care at all levels of health care system. The protocol for the iMSM care model includes three levels of operations to provide effective and efficient OSA screening, timely testing/treatment plans, and coordination of further sleep medicine care follow-up. The iMSM care model prioritizes effective, efficient, and patient-centered sleep medicine care; therefore, all parties and segments of care that receive and provide clinical sleep medicine services may benefit from adopting this innovative approach.

Sleep spindle and slow wave activity in Parkinson disease with excessive daytime sleepiness

Study Objectives

Excessive daytime sleepiness (EDS) is a common and devastating symptom in Parkinson disease (PD), but surprisingly most studies showed that EDS is independent from nocturnal sleep disturbance measured with polysomnography. Quantitative electroencephalography (EEG) may reveal additional insights by measuring the EEG hallmarks of non-rapid eye movement (NREM) sleep, namely slow waves and spindles. Here, we tested the hypothesis that EDS in PD is associated with nocturnal sleep disturbance revealed by quantitative NREM sleep EEG markers.

Methods

Patients with PD (n = 130) underwent polysomnography followed by spectral analysis to calculate spindle frequency activity, slow-wave activity (SWA), and overnight SWA decline, which reflects the dissipation of homeostatic sleep pressure. We used the Epworth Sleepiness Scale (ESS) to assess subjective daytime sleepiness and define EDS (ESS &gt; 10). All examinations were part of an evaluation for deep brain stimulation.

Results

Patients with EDS (n = 46) showed reduced overnight decline of SWA (p = 0.036) and reduced spindle frequency activity (p = 0.032) compared with patients without EDS. Likewise, more severe daytime sleepiness was associated with reduced SWA decline (ß= −0.24 p = 0.008) and reduced spindle frequency activity (ß= −0.42, p &lt; 0.001) across all patients. Reduced SWA decline, but not daytime sleepiness, was associated with poor sleep quality and continuity at polysomnography.

Conclusions

Our data suggest that daytime sleepiness in PD patients is associated with sleep disturbance revealed by quantitative EEG, namely reduced overnight SWA decline and reduced spindle frequency activity. These findings could indicate that poor sleep quality, with incomplete dissipation of homeostatic sleep pressure, may contribute to EDS in PD.

Etiologies of insomnia in Parkinson's disease - Lessons from human studies and animal models

Sleep disorders are integral to Parkinson's disease (PD). Insomnia, an inability to maintain stable sleep, affects most patients and is widely rated as one of the most debilitating facets of this disease. PD insomnia is often perceived as a multifactorial entity - a consequence of several of the disease symptoms, comorbidities and therapeutic strategies. Yet, this view evolved against a backdrop of a relative scarcity of works trying to directly dissect the underlying neural correlates and mechanisms in animal models. The last years have seen the emergence of a wealth of new evidence regarding the neural underpinnings of insomnia in PD. Here, we review early and recent reports from patients and animal models evaluating the etiology of PD insomnia. We start by outlining the phenomenology of PD insomnia and continue to analyze the evidence supporting insomnia as emanating from four distinct subdivisions of etiologies - the symptoms and comorbidities of the disease, the medical therapy, the degeneration of non-dopaminergic cell groups and subsequent alterations in circadian rhythms, and the degeneration of dopaminergic neurons in the brainstem and its resulting effect on the basal ganglia. Finally, we review emerging neuromodulation-based therapeutic avenues for PD insomnia.

Orexin-A in Patients With Lewy Body Disease: A Systematic Review and Meta-Analysis

Background

Abnormal orexin-A levels in cerebrospinal fluid (CSF) have been identified in Alzheimer's disease (AD) and other neurodegenerative diseases. However, few studies have focused on Lewy body disease (LBD) and often with debatable outcomes. Thus, we performed this systematic review and meta-analysis to investigate orexin-A levels in LBD by incorporating data from different studies.

Methods

We gathered studies comparing orexin-A levels in patients with LBD and controls (including healthy controls and other dementia subtypes). In the initial search, 117 relevant articles were identified. After a selection process, seven studies, conducted in Japan, USA, Spain, Switzerland, France, Italy, and Netherlands, were chosen.

Results

In total, 179 patients with LBD and 253 controls were included. Patients with LBD had significantly lower mean orexin-A CSF levels when compared with patients with AD [standard mean difference (SMD): -0.35, 95% confidence interval (CI): -0.70 to -0.00, Z = 1.96, P = 0.05], whereas mean orexin-A levels were significantly higher when compared with patients with frontotemporal lobar degeneration (FTLD) (SMD: 0.61, 95% CI: 0.23-0.99, Z = 3.12, P = 0.002). Orexin-A CSF levels in LBD patients were approximately equal to levels in healthy elderly individuals, whereas they were significantly decreased in LBD patients with excessive daytime sleepiness (EDS) (SMD: -0.15, 95% CI: -0.59 to 0.29, Z = 0.67, P = 0.50).

Conclusions

We showed that orexin-A levels in patients with LBD were not very different from those in normal elderly individuals, whereas they were lower than those in AD patients and higher than those in FTLD patients. The influence of hypersomnia on orexin-A levels should be carefully interpreted.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42021265900.

Hypothalamic α-synuclein and its relation to autonomic symptoms and neuroendocrine abnormalities in Parkinson disease

Parkinson's disease (PD) is a complex neurodegenerative disorder presenting with defining motor features and a variable combination of nonmotor symptoms. There is growing evidence suggesting that hypothalamic involvement in PD may contribute to the pathogenesis of nonmotor symptoms. Initial neuropathologic studies demonstrated histologic involvement of hypothalamic nuclei by Lewy pathology, i.e., neuronal aggregates including Lewy bodies (round eosinophilic inclusions with a halo found in the neuronal perikarya) and other inclusions in neuronal processes such as Lewy neurites. Recent studies using more sensitive immunohistochemistry have shown that synuclein deposition is common in all hypothalamic nuclei and can happen at preclinical stages of the disease. Several neuropathologic changes, including synuclein deposition, neuronal loss, and adaptative morphologic changes, have been described in neurochemically defined specific hypothalamic cell populations with a potential role in the pathogenesis of nonmotor symptoms such as autonomic dysfunction, blood pressure control, circadian rhythms, sleep, and body weight regulation. The clinical implications of these hypothalamic neuropathologic changes are not fully understood and a direct clinical correlation may be challenging due to the multifactorial pathogenesis of the symptomatology and the additional involvement of other peripheral regulatory mechanisms. Future neuropathologic research using histological and functional assessments should establish the potential role of hypothalamic dysfunction on clinical burden, symptomatic therapies, and disease biomarkers in PD.

Sleep disorders in Wilson disease: a systematic review and meta-analysis

STUDY OBJECTIVES

Wilson disease (WD) is an autosomal recessive inherited disorder of copper metabolism resulting in pathologic accumulation of copper in many organs and tissues. Sleep disorders are highly prevalent in patients with WD. However, both prevalence rates and severity of different sleep disorders in patients with WD vary widely. The aims of the current study were to systematically review and perform a meta-analysis of the association between WD and prevalent sleep disorders, including insomnia, rapid eye movement (REM) sleep behavior disorder (RBD), excessive daytime sleepiness (EDS), sleep-disordered breathing (SDB), restless legs syndrome (RLS), periodic limb movement in sleep (PLM), cataplexy-like episodes (CLEs) and sleep paralysis, and objective sleep characteristics.

METHODS

We performed a systematic search of PubMed, EMBase, the Cochrane Library, PsycINFO and ISI Web of Science for case-control studies. A total of 7 studies with 501 participants were included.

RESULTS

We found that 54.1% of patients with WD experience sleep disorders and up to 7.65-fold higher odds compared to control patients. Specifically, patients with WD had higher rates of RBD, insomnia, and EDS based on self-reported questionnaires. No differences were observed in terms of RLS, PLM, or SDB between patients with WD and control patients. Furthermore, objective sleep disruptions based on polysomnographic studies included prolonged sleep onset latency and REM sleep onset latency, reduced total sleep time and sleep efficiency, higher percentage of stage N1 sleep and lower percentage of stage N2 sleep were observed in patients with WD.

CONCLUSIONS

Our study indicates that sleep disorders are frequent in patients with WD. Future studies should examine the longitudinal association of WD with sleep disturbances.

Daytime sleepiness may be an independent symptom unrelated to sleep quality in Parkinson's disease

Excessive daytime sleepiness (EDS) may represent a disabling non-motor symptom in patients affected by Parkinson's disease (PD). This is a secondary analysis of a previous study documenting the improvement of nocturnal sleep in PD patients treated by rotigotine vs placebo. Here we tested the supposition that EDS may represent a distinct PD non-motor symptom occurring independently of other sleep-wake disorders; moreover, we verified whether EDS can be influenced by the improvement of nocturnal sleep in PD. In the present study, we evaluated the daytime sleepiness of PD patients treated with nocturnal administration of rotigotine (PD-Rot) vs placebo (PD-Pla), as measured by both subjective (Epworth Sleepiness Scale-ESS) and objective (Multiple Sleep Latency Test-MSLT) tools. We included 21 PD-Rot compared to 21 PD-Pla patients and documented no significant changes of both ESS and MSLT data between baseline and follow-up visits in both groups. Moreover, we found no correlations between nocturnal sleep improvement and diurnal sleepiness. Therefore, these data suggest that the improvement of nocturnal sleep in PD patients does not modify the daytime sleepiness, thus suggesting that diurnal sleepiness may occur independently of nocturnal sleep disturbances in PD patients.

An overview of sleep and circadian dysfunction in Parkinson's disease

Sleep and circadian alterations are amongst the very first symptoms experienced in Parkinson's disease, and sleep alterations are present in the majority of patients with overt clinical manifestation of Parkinson's disease. However, the magnitude of sleep and circadian dysfunction in Parkinson's disease, and its influence on the pathophysiology of Parkinson's disease remains often unclear and a matter of debate. In particular, the confounding influences of dopaminergic therapy on sleep and circadian dysfunction are a major challenge, and need to be more carefully addressed in clinical studies. The scope of this narrative review is to summarise the current knowledge around both sleep and circadian alterations in Parkinson's disease. We provide an overview on the frequency of excessive daytime sleepiness, insomnia, restless legs, obstructive apnea and nocturia in Parkinson's disease, as well as addressing sleep structure, rapid eye movement sleep behaviour disorder and circadian features in Parkinson's disease. Sleep and circadian disorders have been linked to pathological conditions that are often co-morbid in Parkinson's disease, including cognitive decline, memory impairment and neurodegeneration. Therefore, targeting sleep and circadian alterations could be one of the earliest and most promising opportunities to slow disease progression. We hope that this review will contribute to advance the discussion and inform new research efforts to progress our knowledge in this field.

Rapid Eye Movement sleep deprivation of rat generates ROS in the hepatocytes and makes them more susceptible to oxidative stress

Background

Rapid Eye Movement sleep deprivation (REMSD) of rats causes inflammation of the liver and apoptotic cell death of neurons and hepatocytes. Studies also suggest that REM sleep deprivation can cause muscle as well as cardiac injury and neurodegenerative diseases.

Objective and methods

The aim of this research was to determine whether REM sleep deprivation of rats would increase the levels of reactive oxygen species (ROS) in the hepatocytes and create oxidative stress in them. We selectively deprived the rats for REM sleep using the standard flower pot method.

Results

We observed that when rats were subjected to REM sleep deprivation, the levels of ROS in their hepatocytes increased ~184.33% compared to large platform control (LPC) group by day 9 of deprivation, but it returned towards normal level (~49.27%) after recovery sleep for 5 days. Nitric oxide synthase (iNOS) gene expression and protein levels as determined by real-time PCR and western blot analysis respectively were found to be elevated in hepatocytes of REM sleep deprived rats as compared to the LPC group. The level of nitric oxide (NO) in the hepatocytes of REMSD rats also increased by ~404.40% as compared to the LPC group but sleep recovery for 5 days normalized the effect (~135.35% compared to LPC group). We used a large platform control group as a reference group to compare with the REM sleep deprived group as the effect on the hepatocytes of both LPC group and cage control groups were not significantly different.

Discussion

We have analyzed the oxidative stress generated in the hepatocytes of rats due to REM sleep deprivation and further consequences of it. REMS deprivation not only increased the levels of ROS in the hepatocytes but also induced iNOS and NO in them. REM sleep deprived hepatocytes became more susceptible to oxidative stresses on further exposures. Furthermore, our study has great pathological and physiological.

The Discovery of Suvorexant, the First Orexin Receptor Drug for Insomnia

Historically, pharmacological therapies have used mechanisms such as γ-aminobutyric acid A (GABA_A) receptor potentiation to drive sleep through broad suppression of central nervous system activity. With the discovery of orexin signaling loss as the etiology underlying narcolepsy, a disorder associated with hypersomnolence, orexin antagonism emerged as an alternative approach to attenuate orexin-induced wakefulness more selectively. Dual orexin receptor antagonists (DORAs) block the activity of orexin 1 and 2 receptors to both reduce the threshold to transition into sleep and attenuate orexin-mediated arousal. Among DORAs evaluated clinically, suvorexant has pharmacokinetic properties engineered for a plasma half-life appropriate for rapid sleep onset and maintenance at low to moderate doses. Unlike GABA_A receptor modulators, DORAs promote both non-rapid eye movement (NREM) and REM sleep, do not disrupt sleep stage-specific quantitative electroencephalogram spectral profiles, and allow somnolence indistinct from normal sleep. The preservation of cognitive performance and the ability to arouse to salient stimuli after DORA administration suggest further advantages over historical therapies.

Nonmotor Subtyping in Parkinson's Disease

Nonmotor symptoms are integral to Parkinson's disease. Several subtypes dominated by specific nonmotor symptoms have emerged. In this chapter, the rationale behind nonmotor subtyping and currently proposed nonmotor subgroups within Parkinson's disease based on data-driven cluster analysis and clinical observations will be summarized. Furthermore, the concept of seven clinical nonmotor subtypes will be discussed in detail including the clinical presentation, potential biomarkers, and the clinical relevance. In future, nonmotor subtypes will possibly play a major role within the aim to achieve personalized medicine.

Chronic sleep disturbance and neural injury: links to neurodegenerative disease

Sleep-wake disruption is frequently observed and often one of the earliest reported symptoms of many neurodegenerative disorders. This provides insight into the underlying pathophysiology of these disorders, as sleep-wake abnormalities are often accompanied by neurodegenerative or neurotransmitter changes. However, in addition to being a symptom of the underlying neurodegenerative condition, there is also emerging evidence that sleep disturbance itself may contribute to the development and facilitate the progression of several of these disorders. Due to its impact both as an early symptom and as a potential factor contributing to ongoing neurodegeneration, the sleep-wake cycle is an ideal target for further study for potential interventions not only to lessen the burden of these diseases but also to slow their progression. In this review, we will highlight the sleep phenotypes associated with some of the major neurodegenerative disorders, focusing on the circadian disruption associated with Alzheimer's disease, the rapid eye movement behavior disorder and sleep fragmentation associated with Parkinson's disease, and the insomnia and circadian dysregulation associated with Huntington's disease.

The orexin neuropeptide system: physical activity and hypothalamic function throughout the aging process

There is a rising medical need for novel therapeutic targets of physical activity. Physical activity spans from spontaneous, low intensity movements to voluntary, high-intensity exercise. Regulation of spontaneous and voluntary movement is distributed over many brain areas and neural substrates, but the specific cellular and molecular mechanisms responsible for mediating overall activity levels are not well understood. The hypothalamus plays a central role in the control of physical activity, which is executed through coordination of multiple signaling systems, including the orexin neuropeptides. Orexin producing neurons integrate physiological and metabolic information to coordinate multiple behavioral states and modulate physical activity in response to the environment. This review is organized around three questions: (1) How do orexin peptides modulate physical activity? (2) What are the effects of aging and lifestyle choices on physical activity? (3) What are the effects of aging on hypothalamic function and the orexin peptides? Discussion of these questions will provide a summary of the current state of knowledge regarding hypothalamic orexin regulation of physical activity during aging and provide a platform on which to develop improved clinical outcomes in age-associated obesity and metabolic syndromes.

Sparing of orexin-A and orexin-B neurons in the hypothalamus and of orexin fibers in the substantia nigra of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-treated macaques

Several studies conducted in patients with Parkinson's disease have reported that the degeneration of substantia nigra dopaminergic neurons, which are essential for motor control, is associated with the loss of hypothalamic orexin neurons, which are involved in sleep regulation. In order to better explore the mutual interactions between these two systems, we wished to determine in macaques: (i) if the two orexin peptides, orexin-A and orexin-B, are distributed in the same hypothalamic cells and if they are localized in nerve terminals that project onto nigral dopaminergic neurons, and (ii) if there is a loss of orexin neurons in the hypothalamus and of orexin fibers innervating nigral dopaminergic neurons in macaques rendered parkinsonian by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) intoxication. We showed that virtually all cells stained for orexin-A in the hypothalamus co-expressed orexin-B. Numerous terminals stained for both orexin-A and orexin-B immunoreactivity that innervated the whole extent of the ventral tegmental area and substantia nigra pars compacta were found in close proximity to tyrosine hydroxylase-immunoreactive dendrites. These data indicate that orexin-A and orexin-B peptides are in a position to play a role in controlling the activity of nigral dopaminergic neurons. However, no loss of orexin-A or orexin-B neurons in the hypothalamus and no loss of orexin fibers in the substantia nigra pars compacta was found in MPTP-treated macaques when compared with control macaques. We conclude that a relatively selective dopaminergic lesion, such as that performed in MPTP-treated macaques, is not sufficient to induce a loss of hypothalamic orexin neurons.

Dysautonomia in narcolepsy: evidence by questionnaire assessment

Background and Purpose

Excessive daytime sleepiness and sudden sleep attacks are the main features of narcolepsy, but rapid-eye-movement sleep behavior disorder (RBD), hyposmia, and depression can also occur. The latter symptoms are nonmotor features in idiopathic Parkinson's disease (IPD). In the present study, IPD-proven diagnostic tools were tested to determine whether they are also applicable in the assessment of narcolepsy.

Methods

This was a case-control study comparing 15 patients with narcolepsy (PN) and 15 control subjects (CS) using the Scales for Outcomes in Parkinson's Autonomic Test (SCOPA-AUT), Parkinson's Disease Nonmotor Symptoms (PDNMS), University of Pennsylvania Smell Test, Farnsworth-Munsell 100 Hue test, Beck Depression Inventory, and the RBD screening questionnaire.

Results

Both the PN and CS exhibited mild hyposmia and no deficits in visual tests. Frequent dysautonomia in all domains except sexuality was found for the PN. The total SCOPA-AUT score was higher for the PN (18.47±10.08, mean±SD) than for the CS (4.40±3.09), as was the PDNMS score (10.53±4.78 and 1.80±2.31, respectively). RBD was present in 87% of the PN and 0% of the CS. The PN were more depressed than the CS. The differences between the PN and CS for all of these variables were statistically significant (all p<0.05).

Conclusions

The results of this study provide evidence for the presence of dysautonomia and confirm the comorbidities of depression and RBD in narcolepsy patients. The spectrum, which is comparable to the nonmotor complex in IPD, suggests wide-ranging, clinically detectable dysfunction beyond the narcoleptic core syndrome.

The hypocretin/orexin system: an increasingly important role in neuropsychiatry

Hypocretins, also named as orexins, are excitatory neuropeptides secreted by neurons specifically located in lateral hypothalamus and perifornical areas. Orexinergic fibers are extensively distributed in various brain regions and involved in a number of physiological functions, such as arousal, cognition, stress, appetite, and metabolism. Arousal is the most important function of orexin system as dysfunction of orexin signaling leads to narcolepsy. In addition to narcolepsy, orexin dysfunction is associated with serious neural disorders, including addiction, depression, and anxiety. However, some results linking orexin with these disorders are still contradictory, which may result from differences of detection methods or the precision of tools used in measurements; strategies targeted to orexin system (e.g., antagonists to orexin receptors, gene delivery, and cell transplantation) are promising new tools for treatment of neuropsychiatric disorders, though studies are still in a stage of preclinical or clinical research.

Daytime sleepiness and Parkinson's disease: the contribution of the multiple sleep latency test

Background. Sleep disorders are major nonmotor manifestations of patients with Parkinson's disease (PD), and excessive daytime sleepiness (EDS) is one of the most common symptoms. Objective. We reviewed a current literature concerning major factors that influence EDS in PD patients, using Multiple Sleep Latency Test (MSLT). Methods. A Medline search found 23 studies. Results. The presence of EDS was observed in 12.7% to 47% in patients without complaints of daytime sleepiness and 47% to 66.7% with complaints of daytime sleepiness. Despite being recognized by several authors, major factors that influence EDS, such as severity of motor symptoms, use of dopaminergic medications, and associated sleep disturbances, presented contradictory data. Conclusions. Available data suggest that the variability of the results may be related to the fact that it was conducted with a small sample size, not counting the neuropathological heterogeneity of the disease. Thus, before carrying out longitudinal studies with significant samples, careful analysis should be done by assigning a specific agent on the responsibility of EDS in PD patients.

Risk of obstructive sleep apnea in Parkinson's disease: a meta-analysis

STUDY OBJECTIVES

Sleep disorders are a common symptom of Parkinson's disease (PD) and they significantly impair the sleep quality of the PD patients. However, there is no conclusive evidence to support the relation between PD and the prevalence of obstructive sleep apnea (OSA). The purpose of this meta-analysis review is to evaluate the association between PD and the prevalence of OSA.

METHODS

A comprehensive literature search was conducted on PubMed and Embase through July 2013. Only studies that referred to PD and the prevalence of OSA and that met the selection criteria were included in the analysis. The odds ratios (ORs) were used to evaluate the relationship of PD and the prevalence of OSA by the fixed-effect model.

RESULTS

Five eligible studies were analyzed in this study including 322 cases and 6,361 controls. The pooled-analysis showed the OR to be 0.60 (95% confidence interval (CI): 0.44 to 0.81, P = 0.001) and I(2) = 0.0% (χ(2) = 3.90, P = 0.420) in the fixed-effect model.

CONCLUSIONS

Although we only included five small sample studies that indicated high homogeneity in the heterogeneity test, the results suggest that there is a significant negative association between PD and the prevalence of OSA; PD patients generally have a reduced prevalence of OSA. According to our analysis, these results are primarily due to the lower BMI of PD patients when compared with the general population controls.

Reduced orexin-A levels in frontotemporal dementia: possible association with sleep disturbance

Sleep disturbances including excessive daytime sleepiness (EDS) are encountered in frontotemporal dementia (FTD). To investigate the relationship between the plasma orexin-A levels and sleep disturbance patterns, we measured the plasma orexin-A levels and performed sleep studies in patients with FTD. The orexin-A levels were measured in 10 consecutive patients with FTD and controls by enzyme-linked immunosorbent assay. Nocturnal polysomnography (PSG) and Multiple Sleep Latency Test (MSLT) were performed in 2 patients with FTD. The orexin-A levels were significantly lower in patients with FTD compared to controls. The PSG revealed increased rapid eye movement (REM) latency in patients, whether or not they reported EDS. Mean sleep latency in MSLT was less than 10 minutes in both the patients, being shorter in patient without EDS, but none of them had REM sleep onset. Some patients with FTD may develop narcolepsy-like involuntary sleep attacks, even without complaining of EDS. Involvement of hypothalamus and a subsequent alteration in the orexin levels might be one of the determining factors in this sleep disturbance.

Comorbidity and mortality of narcolepsy: a controlled retro- and prospective national study

STUDY OBJECTIVES

To identify the factual morbidity and mortality of narcolepsy in a controlled design.

SETTING

National Patient Registry.

PATIENTS

All national diagnosed patients (757) with health information at least 3 years prior to and after diagnose of narcolepsy.

CONTROLS

Randomly selected four citizens (3,013) matched for age, sex, and socioeconomic status from the Danish Civil Registration System Statistics.

RESULTS

Increased morbidity prior to narcolepsy diagnosis included (odds ratio, 95% confidence interval):- diseases of the endocrine, nutritional, and metabolic systems (2.10, 1.32-3.33); nervous system (5.27, 3.65-7.60); musculoskeletal system (1.59, 1.23-2.05); and other abnormal symptoms and laboratory findings (1.66, 1.25-2.22). After the diagnosis, narcolepsy patients experienced diseases of the endocrine, nutritional, and metabolic (2.31, 1.51-3.54), nervous (9.19, 6.80-12.41), musculoskeletal (1.70, 1.28-2.26), eye (1.67, 1.03-2.71), and respiratory systems (1.84, 1.21-2.81). Specific diagnoses were diabetes (2.4, 1,2-4.7, P < 0.01), obesity (13.4, 3.1-57.6, P < 0.001), sleep apnea (19.2, 7.7-48.3, P < 0.001), other sleep disorders (78.5, 11.8-523.3, P < 0.001), chronic obstructive pulmonary disease (2.8, 1.4-5.8, P < 0.01), lower back pain (2.5, 1.4-4.2, P < 0.001), arthrosis/arthritis (2.5, 1.3-4.8, P < 0.01), observation of neurological diseases (3.5, 1.9-6.5, P < 0.001), observation of other diseases (1.7, 1.2-2.5, P < 0.01), and rehabilitation (5.0, 1.5-16.5, P < 0.005). There was a trend towards greater mortality in narcolepsy (P = 0.07).

CONCLUSIONS

Patients with narcolepsy present higher morbidity several years prior to diagnose and even higher thereafter. The mortality rate due to narcolepsy was slightly but not significantly higher.

Ventricular orexin-A (hypocretin-1) levels correlate with rapid-eye-movement sleep without atonia in Parkinson's disease

OBJECTIVE

Patients with Parkinson's disease frequently complain of sleep disturbances and loss of muscle atonia during rapid-eye-movement (REM) sleep is not rare. The orexin-A (hypocretin-1) hypothalamic system plays a central role in controlling REM sleep. Loss of orexin neurons results in narcolepsy-cataplexy, a condition characterized by diurnal sleepiness and REM sleep without atonia. Alterations in the orexin-A system have been also documented in Parkinson's disease, but whether these alterations have clinical consequences remains unknown.

METHODS

Here, we measured orexin-A levels in ventricular cerebrospinal fluid from eight patients with Parkinson's disease (four males and four females) who underwent ventriculography during deep brain-stimulation surgery and performed full-night polysomnography before surgery.

RESULTS

Our results showed a positive correlation between orexin-A levels and REM sleep without muscle atonia.

CONCLUSION

Our results suggest that high levels of orexin-A in Parkinson's disease may be associated with loss of REM muscle atonia.

Parkinson's disease and sleep/wake disturbances

Parkinson's disease (PD) has traditionally been characterized by its cardinal motor symptoms of bradykinesia, rigidity, resting tremor, and postural instability. However, PD is increasingly being recognized as a multidimensional disease associated with myriad nonmotor symptoms including autonomic dysfunction, mood disorders, cognitive impairment, pain, gastrointestinal disturbance, impaired olfaction, psychosis, and sleep disorders. Sleep disturbances, which include sleep fragmentation, daytime somnolence, sleep-disordered breathing, restless legs syndrome (RLS), nightmares, and rapid eye movement (REM) sleep behavior disorder (RBD), are estimated to occur in 60% to 98% of patients with PD. For years nonmotor symptoms received little attention from clinicians and researchers, but now these symptoms are known to be significant predictors of morbidity in determining quality of life, costs of disease, and rates of institutionalization. A discussion of the clinical aspects, pathophysiology, evaluation techniques, and treatment options for the sleep disorders that are encountered with PD is presented.

Daytime REM sleep in Parkinson's disease

BACKGROUND

Previous studies have demonstrated both clinical and neurochemical similarities between Parkinson's disease (PD) and narcolepsy. The intrusion of REM sleep into the daytime remains a cardinal feature of narcolepsy, but the importance of these intrusions in PD remains unclear. In this study we examined REM sleep during daytime Maintenance of Wakefulness Testing (MWT) in PD patients.

METHODS

Patients spent 2 consecutive nights and days in the sleep laboratory. During the daytime, we employed a modified MWT procedure in which each daytime nap opportunity (4 per day) was extended to 40 min, regardless of whether the patient was able to sleep or how much the patient slept. We examined each nap opportunity for the presence of REM sleep and time to fall asleep.

RESULTS

Eleven of 63 PD patients studied showed 2 or more REM episodes and 10 showed 1 REM episode on their daytime MWTs. Nocturnal sleep characteristics and sleep disorders were unrelated to the presence of daytime REM sleep, however, patients with daytime REM were significantly sleepier during the daytime than those patients without REM. Demographic and clinical variables, including Unified Parkinson's Disease Rating Scale motor scores and levodopa dose equivalents, were unrelated to the presence of REM sleep.

CONCLUSIONS

A sizeable proportion of PD patients demonstrated REM sleep and daytime sleep tendency during daytime nap testing. These data confirm similarities in REM intrusions between narcolepsy and PD, perhaps suggesting parallel neurodegenerative conditions of hypocretin deficiency.

Daytime alertness in Parkinson's disease: potentially dose-dependent, divergent effects by drug class

Many patients with idiopathic Parkinson's disease experience difficulties maintaining daytime alertness. Controversy exists regarding whether this reflects effects of antiparkinsonian medications, the disease itself, or other factors such as nocturnal sleep disturbances. In this study we examined the phenomenon by evaluating medicated and unmedicated Parkinson's patients with objective polysomnographic measurements of nocturnal sleep and daytime alertness. Patients (n = 63) underwent a 48-hour laboratory-based study incorporating 2 consecutive nights of overnight polysomnography and 2 days of Maintenance of Wakefulness Testing. We examined correlates of individual differences in alertness, including demographics, clinical features, nocturnal sleep variables, and class and dosage of anti-Parkinson's medications. Results indicated that, first, relative to unmediated patients, all classes of dopaminergic medications were associated with reduced daytime alertness, and this effect was not mediated by disease duration or disease severity. Second, the results showed that increasing dosages of dopamine agonists were associated with less daytime alertness, whereas higher levels of levodopa were associated with higher levels of alertness. Variables unrelated to the Maintenance of Wakefulness Test defined daytime alertness including age, sex, years with diagnosis, motor impairment score, and most nocturnal sleep variables. Deficits in objectively assessed daytime alertness in Parkinson's disease appear to be a function of both the disease and the medications and their doses used. The apparent divergent dose-dependent effects of drug class in Parkinson's disease are anticipated by basic science studies of the sleep/wake cycle under different pharmacological agents.

Recognition and diagnosis of sleep disorders in Parkinson's disease

Sleep disturbances are among the most frequent and incapacitating non-motor symptoms of Parkinson’s disease (PD), and are increasingly recognized as an important determinant of impaired quality of life. Here we review several recent developments regarding the recognition and diagnosis of sleep disorders in PD. In addition, we provide a practical and easily applicable approach to the diagnostic process as a basis for tailored therapeutic interventions. This includes a stepwise scheme that guides the clinical interview and subsequent ancillary investigations. In this scheme, the various possible sleep disorders are arranged not in order of prevalence, but in a ‘differential diagnostic’ order. We also provide recommendations for the use of sleep registrations such as polysomnography. Furthermore, we point out when a sleep specialist could be consulted to provide additional diagnostic and therapeutic input. This structured approach facilitates early detection of sleep disturbances in PD, so treatment can be initiated promptly.

Sleep problems in Parkinson’s disease patients

SUMMARY Parkinson’s disease (PD) patients demonstrate a variety of sleep/wake complaints. Some of these are associated with dopaminergic dysfunction, some presumed to arise from nondopaminergic PD pathology, some from PD treatments and, in some, the etiologies are multifactorial or unknown. Optimal management of sleep/wake problems requires a good understanding of sleep/wake principals in the PD population, as there are few controlled trials to dictate therapy. In this article, we review the main causes of sleep/wake disorders in PD patients, namely sleep fragmentation, excessive daytime sleepiness, restless legs syndrome, periodic limb movement of sleep, rapid eye movement sleep behavioral disorder and sleep apnea. Available therapies and management recommendations for each disorder are given particular emphasis.

Excessive daytime sleepiness in patients with Parkinson's disease

Excessive daytime sleepiness (EDS) is described as inappropriate and undesirable sleepiness during waking hours and is a common non-motor symptom in Parkinson's disease, affecting up to 50% of patients. EDS has a large impact on the quality of life of Parkinson's disease patients as well as of their caregivers, in some cases even more than the motor symptoms of the disease. Drug-induced EDS is a particular problem as many dopamine agonists used for the treatment of Parkinson's disease have EDS as an adverse effect. Dopaminergic treatment may also render a subset of Parkinson's disease patients at risk for sudden-onset sleep attacks that occur without warning and can be particularly hazardous if the patient is driving. This demonstrates the need for early recognition and management not only to increase health-related quality of life but also to ensure patient safety. There are many assessment tools for EDS, including the Epworth Sleepiness Scale (ESS) and the Multiple Sleep Latency Test (MSLT), although only the Parkinson's Disease Sleep Scale (PDSS) and the SCales for Outcomes in PArkinson's Disease-Sleep (SCOPA-S) are specifically validated for Parkinson's disease. Polysomnography can be used when necessary. Management comprises non-pharmacological and pharmacological approaches. Non-pharmacological approaches can be the mainstay of treatment for mild to moderate EDS. Advice on good sleep hygiene is instrumental, as pharmacological approaches have yet to provide consistent and reliable results without significant adverse effects. The efficacy of pharmacological treatment of EDS in Parkinson's disease using wakefulness-promoting drugs such as modafinil remains controversial. Further areas of research are now also focusing on adenosine A(2A) receptor antagonists, sodium oxybate and caffeine to promote wakefulness. A definitive treatment for the highly prevalent drug-induced EDS has not yet been found.

Problems associated with fluid biomarkers for Parkinson's disease

This article focuses on biochemical markers that may be used in the diagnostics of Parkinson's disease and associated disorders, and to identify early cases and stratify patients into subgroups. We present an updated account of some currently available candidate fluid biomarkers, and discuss their diagnostic performance and limitations. We also discuss some of the general problems with Parkinson's disease biomarkers and possible ways of moving forward. It may be concluded that a diagnostically useful fluid biomarker for Parkinson's disease is yet to be identified. However, some interesting candidates exist and may prove useful in the future, alone or when analyzed together in patterns.

No increased risk of obstructive sleep apnea in Parkinson's disease

Pulmonary function abnormalities in Parkinson's disease (PD) might predispose patients to obstructive sleep apnea (OSA) and daytime sleepiness. Fifty-five idiopathic PD patients (mean age = 63.9) underwent three consecutive nights of in-laboratory polysomnography on their usual dopaminergic medications. Sleep apnea severity was compared to published, normative, population-based data from the Sleep Heart Health Study. Demographic and clinical data were compared in patients with and without OSA. The apnea-hyponea index (AHI) was stable across nights in PD patients, and was not different between PD patients and normative controls. Epworth Sleepiness Scale scores, Body Mass Index, and snoring did not correlate with AHI. Severity of OSA is stable across multiple nights in PD patients. Rates of OSA in PD are similar to those seen in the general population. Daytime sleepiness, snoring, and obesity may not be helpful in identifying OSA in PD.

Comparative levels of excessive daytime sleepiness in common medical disorders

INTRODUCTION

Sleep restriction and sleep disorders are common causes of excessive daytime sleepiness (EDS). Medical disorders (MD) can also cause EDS, but previous studies have used non-standardized measures, selected samples, or have examined EDS in singular disorders. This study describes the relative degree of EDS associated with medical disorders to provide comparative data across a range of common medical conditions in a large unselected community-based sample.

METHODS

Responses of 2612 individuals (aged 18-65) were assessed after excluding those with suspected sleep disordered breathing, narcolepsy, and shift workers. Participants across a range of medical disorders were evaluated using the Epworth Sleepiness Scale (ESS) and patient reports of nocturnal sleep.

RESULTS

Sixty-seven percent of the sample reported a MD. The prevalence of EDS (ESS>or=10) was 31.4% in individuals with MD and increased as a function of a number of MD (0 MD=29.4%, 1 MD=28.4%, 2 MD=31.0%, 3 MD=35.3%, 4 MD=38.4%). Disorders which were independent predictors of EDS were ulcers OR=2.21 (95% CI=1.35-3.61), migraines OR=1.36 (95% CI=1.08-1.72), and depression OR=1.46 (95% CI=1.16-1.83) after controlling for other conditions, age, gender, time in bed, caffeine, smoking and alcohol use. Participants with ulcers had the highest prevalence of sleepiness, 50.0%, as well as the highest level of problems falling asleep (40.8%) and awakenings during the night (62.5%).

CONCLUSIONS

Individuals with ulcers, migraines, and depression have independent and clinically significant levels of EDS relative to other common MD.