Sleep-Disordered Breathing in Neurodegenerative Diseases

Therapeutic options for nocturnal problems in Parkinson's disease and atypical parkinsonian disorders

Sleep disturbances in Parkinson's disease and parkinsonism (such as atypical parkinsonian disorders like multiple system atrophy, progressive supranuclear palsy, dementia with Lewy bodies and corticobasal degeneration) are multifactorial and as such treatment needs to be tailored to the specific patient case and sleep dysfunction. One also has to consider drug-related effects on sleep architecture. This article provides an overview of the therapeutic options for nocturnal problems in Parkinson`s disease and atypical parkinsonian disorders.

Sleep and movement disorders

PURPOSE OF REVIEW

The aim is to review sleep disturbances in different movement disorders, mainly Parkinson's disease, and highlight current concepts on merging the boundaries between movement disorders and dissociative states of being.

RECENT FINDINGS

Since the observation that rapid eye movement sleep behavior disorder (RBD) may be an early marker of neurodegeneration, many studies focused on this disorder for the opportunity to explore the pathogenetic mechanisms underlying movement disorder and future neuroprotective therapies. It is also increasingly evident that this disorder is a possible marker for incoming dementia and for a general worst prognosis. Mechanisms of excessive daytime sleepiness in Parkinson's disease are still to be clarified and, if the role of hypocretin neuron loss is still doubtful, attention is moving to the role of monoaminergic system disruption. The role of dopamine in circadian rhythm regulation is opening new scenarios, namely the disruption of clock genes expression. Finally, the close relationship between sleep and movement disorder is emerging also in primarly sleep disorders.

SUMMARY

Recent studies provided new insights into the links between sleep and movement disorder that may simplify the diagnostic process and shed light on the underlying pathophysiological mechanisms.

Breathing and the nervous system

Breathing requires complex interactions of the central and peripheral nervous systems with the respiratory system. It involves cortical (volitional) as well as subcortical (automatic) output. Cortical output is mainly through the corticospinal tract, whereas the brainstem sends signals via the reticulospinal tract. Groups of nuclei in the brainstem (pneumotaxic center, dorsal and ventral respiratory group), situated in the pons and medulla, function as rhythm generators. Some of these nuclei have intrinsic pacemaker activity; however, their output is affected extensively by various chemical (through aortic and carotid bodies), mechanical (stretch reflexes), and neural feedbacks from the peripheral nervous system involving cranial nerves V, VII, IX, X, and XI. Brainstem nuclei also have central chemoreceptors that detect changes in serum carbon dioxide and pH. Various neurologic disorders such as stroke or neurodegenerative diseases (Parkinson's disease, multiple system atrophy) can adversely affect respiration and may even be the first sign of disease onset. Clinicians should have a better understanding of this complex but important physiological process to better appreciate pathologies affecting it. Future research is needed to enhance our understanding of this intricate process.

Automated sleep apnea quantification based on respiratory movement

Obstructive sleep apnea (OSA) is a prevalent and treatable disorder of neurological and medical importance that is traditionally diagnosed through multi-channel laboratory polysomnography(PSG). However, OSA testing is increasingly performed with portable home devices using limited physiological channels. We tested the hypothesis that single channel respiratory effort alone could support automated quantification of apnea and hypopnea events. We developed a respiratory event detection algorithm applied to thoracic strain-belt data from patients with variable degrees of sleep apnea. We optimized parameters on a training set (n=57) and then tested performance on a validation set (n=59). The optimized algorithm correlated significantly with manual scoring in the validation set (R2=0.73 for training set, R2=0.55 for validation set; p<0.05). For dichotomous classification, the AUC was >0.92 and >0.85 using apnea-hypopnea index cutoff values of 5 and 15, respectively. Our findings demonstrate that manually scored AHI values can be approximated from thoracic movements alone. This finding has potential applications for automating laboratory PSG analysis as well as improving the performance of limited channel home monitors.

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.

Sleep and comorbid neurologic disorders

PURPOSE OF REVIEW

An understanding of the impact of sleep on neurologic disorders, and the impact of neurologic disorders on sleep, provides fresh opportunities for neurologists to improve the quality of life and functioning of their patients.

RECENT FINDINGS

Sleep-disordered breathing (SDB) is a risk factor for cerebrovascular disease and should be considered in all TIA and stroke patients. Sleep disorders can amplify nociception and worsen headache disorders; and some headaches, including those related to SDB and hypnic headache, are sleep specific. REM sleep behavior disorder may be an early sign of neurodegenerative disease. Focal lesions of almost any etiology (eg, multiple sclerosis and CNS malignancies) in the hypothalamus, basal forebrain, or brainstem may result in sleep disturbance, sleepiness, and insomnia. Sleep-related hypoventilation and fatigue are common in neuromuscular disease. SDB and epilepsy are mutually facilitatory, and poor sleep can exacerbate epilepsy.

SUMMARY

Continued surveillance for sleep disorders by neurologists is rewarded by new treatment avenues in their patients with the possibility of improved clinical outcomes.

Sleep-disordered breathing

PURPOSE OF REVIEW

This article introduces readers to the clinical presentation, diagnosis, and treatment of sleep-disordered breathing and reviews the associated risk factors and health consequences.

RECENT FINDINGS

Sleep-disordered breathing is associated with significant impairments in daytime alertness and cognitive function as well as adverse health outcomes. The initial treatment of choice is positive airway pressure. Improvements in technology and mask delivery systems have helped to make this treatment more comfortable and convenient for many patients.

SUMMARY

Sleep-disordered breathing, particularly in the form of obstructive sleep apnea, is highly prevalent in the general population and has important implications for neurology patients. Sleep-disordered breathing is characterized by repetitive periods of cessation in breathing, termed apneas, or reductions in the amplitude of a breath, known as hypopneas, that occur during sleep. These events are frequently associated with fragmentation of sleep, declines in oxygen saturation, and sympathetic nervous system activation with heart rate and blood pressure elevation. Obstructive sleep apnea, which represents cessation of airflow, develops because of factors such as anatomic obstruction of the upper airway related to obesity, excess tissue bulk in the pharynx, and changes in muscle tone and nerve activity during sleep. Central sleep apnea represents cessation of airflow along with absence or significant reduction in respiratory effort during sleep and is more commonly found in the setting of congestive heart failure, neurologic disorders, or cardiopulmonary disease.

Inactivity-induced respiratory plasticity: protecting the drive to breathe in disorders that reduce respiratory neural activity

Multiple forms of plasticity are activated following reduced respiratory neural activity. For example, in ventilated rats, a central neural apnea elicits a rebound increase in phrenic and hypoglossal burst amplitude upon resumption of respiratory neural activity, forms of plasticity called inactivity-induced phrenic and hypoglossal motor facilitation (iPMF and iHMF), respectively. Here, we provide a conceptual framework for plasticity following reduced respiratory neural activity to guide future investigations. We review mechanisms giving rise to iPMF and iHMF, present new data suggesting that inactivity-induced plasticity is observed in inspiratory intercostals (iIMF) and point out gaps in our knowledge. We then survey conditions relevant to human health characterized by reduced respiratory neural activity and discuss evidence that inactivity-induced plasticity is elicited during these conditions. Understanding the physiological impact and circumstances in which inactivity-induced respiratory plasticity is elicited may yield novel insights into the treatment of disorders characterized by reductions in respiratory neural activity.

Ask the experts: Managing sleep disorders in neurodegenerative diseases

Alex Iranzo graduated in medicine (1991) and neurology (1997) and completed his PhD thesis (2002) entitled ‘Sleep disorders in the parkinsonian syndrome’ at the Universidad de Barcelona, Spain. Presently, he is a neurologist consultant at the neurology service and at the multidisciplinary sleep unit of the Hospital Clinic of Barcelona (Barcelona, Spain). He is an investigator at Institut d’Investigacions Biomèdiques August Pi iSunyer and Centro de Investigación Biomédica en Red Enfermedades Neurodegenerativas (Barcelona, Spain). He is a member of numerous national and international neurology, sleep, rapid eye movement sleep behavior disorder and restless legs societies, and is currently spokesperson of the Sleep Disorders Group of the Spanish Society of Neurology, secretary of the International REM Sleep Behavior Disorder Group, treasurer of the Sleep Spanish Society and assistant treasurer of the World Association of Sleep Medicine. Iranzo has widely published as first and corresponding author in peer-reviewed journals such as The Lancet, The Lancet Neurology, Annals of Neurology, Neurology, Journal of Neurology, Neurosurgery and Psychiatry, Movement Disorders, Sleep, and Sleep Medicine. Iranzo’s research has focused on sleep in neurological diseases, rapid eye movement sleep behavior disorder, narcolepsy and restless legs syndrome.

Circadian and sleep disorder in Huntington's disease

Huntington's disease is a progressive neurological disorder that starts insidiously with motor, cognitive or psychiatric disturbance, and progresses through a distressing range of symptoms to end with a devastating loss of function, both motor and executive. There is a growing awareness that, in addition to cognitive and psychiatric symptoms, there are other important non-motor symptoms in HD, including sleep and circadian abnormalities. It is not clear if sleep-wake changes are caused directly by HD gene-related pathology, or if they are simply a consequence of having a neurodegenerative disease. From a patient point of view, the answer is irrelevant, since sleep and circadian disturbances are deleterious to good daily living, even in neurologically normal people. The assumption should be that, at the very least, sleep and/or circadian disturbance in HD patients will contribute to their symptoms. At worst, they may contribute to the progressive decline in HD. Here I review the state of our understanding of sleep and circadian abnormalities in HD. I also outline a set of simple rules that can be followed to improve the chances of a good night's sleep, since preventing any 'preventable' symptoms is the a logical first step in treating disease. The long-term impact of sleep disruption in HD is unknown. There have been no large-scale systematic studies of in sleep in HD. Furthermore, there has never been a study of the efficacy of pharmaceuticals that are typically used to treat sleep deficits in HD patients. Thus treatment of sleep disturbance in HD is necessarily empirical. A better understanding of the relationship between sleep/circadian abnormalities and HD pathology is needed, if treatment of this aspect of HD is to be optimized.

Sleep–wake problems in patients with amyotrophic lateral sclerosis: implications for patient management

SUMMARY Sleep–wake problems are frequent, although unrecognized, complications of amyotrophic lateral sclerosis (ALS). Sleep disorders such as insomnia, sleep-disordered breathing and restless legs syndrome have all been reported in patients with ALS, despite the limited number of studies and the small populations investigated so far. Sleep disturbances gradually worsen with disease progression, suggesting a relationship between the severity of disease and the neurodegenerative process. However, poor sleep can also be a consequence of several disturbances such as anxiety, depression, pain, choking, sialorrhea, fasciculations, cramps, nocturia and the inability to get comfortable and move freely in bed. Sleep disorders may have many reflections on patients with ALS, including excessive daytime somnolence, fatigue, impaired cognition, reduced quality of life and survival. This article reviews the recent literature on sleep–wake problems in patients with ALS, focusing on the implications for patient management.

Human apolipoprotein E4 targeted replacement in mice reveals increased susceptibility to sleep disruption and intermittent hypoxia

Intermittent hypoxia (IH) and sleep fragmentation (SF) are major manifestations of sleep apnea, a frequent condition in aging humans. Sleep perturbations are frequent in Alzheimer's disease (AD) and may underlie the progression of disease. We hypothesized that acute short-term IH, SF, and their combination (IH+SF) may reveal unique susceptibility in sleep integrity in a murine model of AD. The effects of acute IH, SF, and IH+SF on sleep architecture, delta power, sleep latency, and core body temperature were assessed in adult male human ApoE4-targeted replacement mice (hApoE4) and wild-type (WT) controls. Slow wave sleep (SWS) was significantly reduced, and rapid eye movement (REM) sleep was almost abolished during acute exposure to IH alone and IH+SF for 6 h in hApoE4, with milder effects in WT controls. Decreased delta power during SWS did not show postexposure rebound in hApoE4 unlike WT controls. IH and IH+SF induced hypothermia, which was more prominent in hApoE4 than WT controls. Mice subjected to SF also showed sleep deficits but without hypothermia. hApoE4 mice, unlike WT controls, exhibited increased sleep propensity, especially following IH and IH+SF, suggesting limited ability for sleep recovery in hApoE4 mice. These findings substantiate the potential impact of IH and SF in modulating sleep architecture and sleep homeostasis including maintenance of body temperature. Furthermore, the increased susceptibility and limited recovery ability of hApoE4 mice to sleep apnea suggests that early recognition and treatment of the latter in AD patients may restrict the progression and clinical manifestations of this frequent neurodegenerative disorder.