Effects of orexin receptor antagonism on human sleep architecture: A systematic review

The efficacy and safety of dual orexin receptor antagonists in obstructive sleep apnea: A systematic review and meta-analysis of randomised controlled trials

Dual orexin receptor antagonists (DORAs) are indicated for the treatment of insomnia disorder. However, DORAs may change sleep parameters, thus having adverse effects on patients with obstructive sleep apnea (OSA). This meta-analysis clarified the impact of DORAs in OSA treatment on sleep architecture and respiratory parameters. We systematically searched PubMed, Embase, and Cochrane Central databases for randomised control trials published up to May 2024. The search focussed on studies discussing the effects of DORAs on sleep architecture in patients with OSA. Nonrandomised studies were excluded. A meta-analysis using a random-effects model was performed. The patients were categorised into subgroups based on the treatment protocol (single or multiple dosages). The Cochrane risk of bias tool for randomised trials assessed the risk of bias. Our meta-analysis included four randomised placebo-controlled trials, encompassing 126 patients with a mean age of 49.1 years. The effects of DORAs on sleep architecture and respiratory parameters were examined. The main findings were as follows: DORAs significantly increased the total sleep time and improved sleep efficiency. However, they did not affect rapid eye movement sleep. DORAs also showed a trend towards decreased wake after sleep onset and did not increase the apnea-hypopnea index. DORAs did not increase the percentage of total sleep time with oxygen saturation lower than 90% and 85% compared with placebo, respectively. Furthermore, DORAs were not associated with significantly higher adverse effects compared with placebo. This meta-analysis demonstrated that DORAs improve sleep and do not impair nighttime respiratory function in patients with OSA.

Dimdazenil for the treatment of insomnia: a systematic review and narrative synthesis

BACKGROUND

Insomnia is a common sleep disorder affecting approximately 10-20% of adults worldwide. Despite various available treatment modalities, significant gaps remain in improving sleep maintenance and reducing functional impairments.

OBJECTIVE

To systematically review and synthesize studies on the efficacy and safety of Dimdazenil for the treatment of insomnia.

METHODS

A comprehensive search of multiple databases and websites was conducted to identify published and unpublished trials from inception to July 19, 2024. Due to the limited number of studies available, quantitative data were synthesized narratively.

RESULTS

This synthesis included four randomized controlled trials. The primary efficacy endpoints of these studies met the predetermined criteria for superiority. Dimdazenil significantly improved certain objective and subjective sleep measures in patients with insomnia, including reduced sleep latency and longer total sleep duration. Importantly, these outcomes were achieved without causing significant excessive daytime drowsiness or impairing daytime functionality. Furthermore, Dimdazenil demonstrated a generally acceptable safety profile and was well tolerated. Most evaluation indicators related to withdrawal symptoms, drug residues, and rebound effects did not show significant statistical differences.

LIMITATIONS

The number of included studies and sample sizes were small, and there is a lack of data on the long-term efficacy and safety of Dimdazenil.

CONCLUSIONS

Dimdazenil offers significant benefits in improving sleep onset and maintenance in patients with insomnia. It presents a favorable safety and tolerability profile while preserving daytime functioning. Future studies should extend the duration and scale to assess the long-term efficacy and safety of Dimdazenil across diverse populations.

Orexin Receptor Antagonists for the Prevention and Treatment of Alzheimer's Disease and Associated Sleep Disorders

Orexins/hypocretins are neuropeptides produced by the hypothalamic neurons, binding two G-protein coupled receptors (orexin 1 and orexin 2 receptors) and playing a critical role in regulating arousal, wakefulness, and various physiological functions. Given the high prevalence of sleep disturbances in Alzheimer's disease (AD) and their reported involvement in AD pathophysiology, the orexin system is hypothesized to contribute to the disease pathogenesis. Specifically, recent evidence suggests that orexin's influence may extend beyond sleep regulation, potentially affecting amyloid-β and tau pathologies. Dual orexin receptor antagonists (DORAs), namely suvorexant, lemborexant, and daridorexant, demonstrated efficacy in treating chronic insomnia disorder across diverse clinical populations. Considering their stabilizing effects on sleep parameters and emerging evidence of a possible neuroprotective role, these agents represent a promising strategy for AD management. This leading article reviews the potential use of orexin receptor antagonists in AD, particularly focusing on their effect in modulating disease-associated sleep disturbances and clinical outcomes. Overall, clinical studies support the use of DORAs to enhance sleep quality in patients with AD with comorbid sleep and circadian sleep-wake rhythm disorders. Preliminary results also suggest that these compounds might influence AD pathology, potentially affecting disease progression. Conversely, research on selective orexin receptor antagonists in AD is currently limited. Further investigation is needed to explore orexin antagonism not only as a symptomatic treatment for sleep disturbances, but also for its broader implications in modifying AD neurodegeneration, emphasizing mechanisms of action and long-term outcomes.

Melatonin, Melatonin Receptors and Sleep: Moving Beyond Traditional Views

Sleep, constituting approximately one-third of the human lifespan, is a crucial physiological process essential for physical and mental well-being. Normal sleep consists of an orderly progression through wakefulness, non-rapid eye movement (NREM) sleep, and rapid eye movement (REM) sleep, all of which are tightly regulated. Melatonin, often referred to as the "hormone of sleep," plays a pivotal role as a regulator of the sleep/wake cycle and exerts its effects through high-affinity G-protein coupled receptors known as MT1 and MT2. Selective modulation of these receptors presents a promising therapeutic avenue for sleep disorders. This review examines research on the multifaceted role of melatonin in sleep regulation, focusing on selective ligands targeting MT1 and MT2 receptors, as well as studies involving MT1 and MT2 knockout mice. Contrary to common beliefs, growing evidence suggests that melatonin, through MT1 and MT2 receptors, might not only influence circadian aspects of sleep but likely, also modulate the homeostatic process of sleep and sleep architecture, or could be the molecule linking the homeostatic and circadian regulation of sleep. Furthermore, the distinct brain localization of MT1 and MT2 receptors, with MT1 receptors primarily regulating REM sleep and MT2 receptors regulating NREM sleep, is discussed. Collectively, sleep regulation extends beyond the circulating levels and circadian peak of melatonin; it also critically involves the expression, molecular activation, and regulatory functions of MT1 and MT2 receptors across various brain regions and nuclei involved in the regulation of sleep. This research underscores the importance of ongoing investigation into the selective roles of MT1 and MT2 receptors in sleep. Such research efforts are expected to pave the way for the development of targeted MT1 or MT2 receptors ligands, thereby optimizing therapeutic interventions for sleep disorders.

Data mining and safety analysis of dual orexin receptor antagonists (DORAs): a real-world pharmacovigilance study based on the FAERS database

Objective

Using the Food and Drug Administration Adverse Event Reporting System (FAERS) database, four signal detection methods were applied to mine adverse drug events (ADEs) related to use of dual orexin receptor antagonists (DORAs) to provide reference for safe clinical use.

Research design and Methods

Data collected from Q3rd 2014 to Q4th 2023 were obtained from the FAERS database. According to the preferred terminology (PT) and systematic organ classification (SOC) of MedDRA v.26.0, the reporting odds ratio (ROR), proportional reporting ratio (PRR), multi-item gamma Poisson shrinker (MGPS), and Bayesian confidence propagation neural network (BCPNN) were used to detect ADE signals.

Results

A total of 11,857 DORAs-related adverse reactions were detected, reported with suvorexant, lemborexant, and daridorexant as the main suspected drugs was 8717584, and 2556, respectively. A higher proportion of females than males were reported (57.27% vs. 33.04%). The top 20 positive PT signals from three DORAs showed that "sleep paralysis" ranked first. "Brain fog" was stronger following daridorexant but was not detected for the other two drugs, and "sleep sex" and "dyssomnia" were stronger in suvorexant but not in the other two drugs. Additionally, some PTs occurred that were not included in drug instructions, such as "hangover" and "hypnagogic hallucination."

Conclusion

In this study, four algorithms (ROR, PRR, BCPNN, and MGPS) were used to mine the safety signals of DORAs. We identified some potential ADE signals that can promote the rational use of DORAs and improve their safety.

The Triad of Sleep, Immunity, and Cancer: A Mediating Perspective

The triadic interplay between sleep, immunity, and cancer represents a growing area of biomedical research with significant clinical implications. This review synthesizes the current knowledge on how sleep influences immune function, the immune system's role in cancer dynamics, and the direct connections between sleep patterns and cancer risk. After a comprehensive overview of the interrelationships among these three domains, the mechanisms of sleep in immune function are described, detailing how sleep regulates the immune system, the effects of sleep duration and quality on immune responses, and the underlying molecular and cellular mechanisms. Also, the complex relationship between immunity and cancer is explored, highlighting the immune system's role in cancer prevention and progression, immune surveillance, tumor microenvironment, and the implications of immunodeficiency and immune modulation on cancer risk. The direct connections between sleep and cancer are then described, presenting epidemiological evidence linking sleep patterns to cancer risk, biological mechanisms that influence cancer development, and the role of sleep disorders in cancer prognosis. The mediating role of sleep between immunity and cancer is highlighted, proposing hypothesized pathways, summarizing evidence from experimental and clinical studies, and evaluating the impact of sleep interventions on immune function and cancer outcomes. This review concludes by discussing the clinical implications and future directions, emphasizing the potential for sleep-based interventions in cancer prevention and treatment, the integration of sleep management in oncology and immunotherapy, and outlining a future research agenda. This agenda includes understanding the mechanisms of the sleep-immunity-cancer interplay, conducting epidemiological studies on sleep and cancer risk, assessing the impact of sleep management in cancer treatment protocols, exploring sleep and tumor microenvironment interactions, and considering policy and public health implications. Through a detailed examination of these interconnected pathways, this review underscores the critical importance of sleep in modulating immune function and cancer outcomes, advocating for interdisciplinary research and clinical strategies to harness this knowledge for improved health outcomes.

Daridorexant treatment for chronic insomnia: a real-world retrospective single-center study

INTRODUCTION

Chronic insomnia disorder (CID) significantly impacts well-being and daily functioning. Daridorexant, a double orexin receptor blocker, has shown efficacy in randomized clinical trials and has been recently approved for the treatment of CID in adult patients. This retrospective observational study aimed to describe real-world data on daridorexant effectiveness and safety in adult patients with CID.

METHODS

Consecutive patients initiating on-label daridorexant at the Sleep Medicine Centre, University Hospital of Rome Tor Vergata were enrolled. Baseline and 30-day follow-up (FU) evaluations included patients' and CID characteristics, comorbidities, and clinicians' and patients' subjective ratings of changes with the Clinical and Patient Global Impression-Improvement scores (CGI-Is and PGI-Is), as well as Insomnia Severity Index (ISI) scores in a subgroup of patients.

RESULTS

Sixty-nine patients initiated 50-mg daily dosage. At FU, 58% of both patients and clinicians rated CID as improved on CGI-Is and PGI-Is, with no differences based on comorbidities, sex, or number of previous medications. No significant predictors of CGI-Is and PGI-Is improvement were identified. At FU, ISI scores (n = 24) significantly decreased from 18.25 ± 3.21 to 12.08 ± 6.12 (Z = 8.000; p < 0.001). Of these, eight patients (33.3%) had absence of insomnia symptoms, and no patients reported a worsening in ISI score categories.

CONCLUSIONS

This study suggests daridorexant to be effective and safe in real-world CID treatment whether used as a first-ever treatment, switch, or add-on, as reflected by subjective and objective measures and the absence of serious treatment-related adverse events. Future research on larger cohorts should explore daridorexant potential across diverse patient characteristics.

Rapid eye movement sleep and epilepsy: exploring interactions and therapeutic prospects

While research interest in the relationship between sleep and epilepsy is growing, it primarily centres on the effects of non-rapid eye movement (NREM) sleep in favouring seizures. Nonetheless, a noteworthy aspect is the observation that, in the lives of patients with epilepsy, REM sleep represents the moment with the least epileptic activity and the lowest probability of having a seizure. Studies demonstrate a suppressive effect of phasic REM sleep on interictal epileptiform discharges, potentially offering insights into epilepsy localisation and management. Furthermore, epilepsy impacts REM sleep, with successful treatment correlating with improved REM sleep quality. Novel therapeutic strategies aim to harness REM's anti-epileptic effects, including pharmacological approaches targeting orexinergic systems and neuromodulation techniques promoting cortical desynchronisation. These findings underscore the intricate relationship between REM sleep and epilepsy, highlighting avenues for further research and therapeutic innovation in epilepsy management.

Association between dual orexin receptor antagonists (DORAs) and suicidality: reports to the United States Food and Drug Administration Adverse Event Reporting System (FAERS)

BACKGROUND

Package inserts for the FDA-approved dual orexin receptor antagonists (DORAs) suvorexant, lemborexant and daridorexant state that suicide risk should be monitored. It remains unknown whether suicidality is attributed to DORAs. We aim to evaluate suicidality associated with DORAs reported to the FDA Adverse Event Reporting System (FAERS).

METHODS

The reporting odds ratio (ROR) was determined with trazodone as the control. Significant disproportionate reporting was determined when 95% confidence intervals (CIs) did not encompass 1.0. We used information components (ICs) to calculate the lower limit of the 95% CI (IC025). IC was significantly increased when the IC025 ≥0.

RESULTS

Suvorexant (0.025 ROR), lemborexant (0.019 ROR) and daridorexant (0.002 ROR) were significantly associated with lower odds of reported completed suicides compared to trazodone (p < 0.05). There was no significantly increased RORs for the DORAs regarding suicidal ideation, depression suicidal, suicidal behavior and suicide attempts. Nonsignificant associations between all parameters of suicidality were observed for each DORA using IC025.

CONCLUSION

We did not find a significant association between any parameter of suicidality captured in the FAERS for each DORA. All persons treated for insomnia pharmacologically/non-pharmacologically should be evaluated for emergence/worsening of any suicidality aspect.

Assessing the Real-World, Long-Term Impact of Lemborexant on Sleep Quality in a Home-Based Clinical Study

Purpose

Both subjective and objective evaluations are essential for the treatment of insomnia. Lemborexant has been shown to be effective in the long-term based solely on a subjective basis, and no long-term objective measures have been evaluated under natural sleep conditions. Small, lightweight sleep electroencephalogram (EEG) monitor was used, instead of polysomnography, to objectively evaluate sleep at home 4 and 12 weeks after lemborexant treatment.

Patients and Methods

Adults and elderly subjects with insomnia disorder, per the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, were enrolled in this open-label, single-arm, single-center trial. Objective and subjective measures of sleep were prospectively assessed. Sleep disturbance, excessive sleepiness, and depressive symptoms were assessed using questionnaires.

Results

A total of 45 subjects were screened, of which 33 were enrolled. Paired t-tests were conducted to evaluate changes in sleep variables and compared with the baseline; subjects showed significant improvements in objective sleep efficiency (SE) and subjective sleep parameters at weeks 4 and 12 following treatment with lemborexant. When baseline values were taken into account, a repeated-multivariate analysis of variance (MANOVA) revealed statistically significant changes in the objective measures. Sleep disturbance, excessive sleepiness, and depressive symptoms improved after three months of lemborexant treatment.

Conclusion

Furthermore, lemborexant therapy improved nocturnal sleep, when measured objectively using sleep EEG monitoring at home, and improved daytime sleepiness and depressive symptoms in older adults with insomnia disorder.

Targeting sleep and the circadian system as a novel treatment strategy for Parkinson's disease

There is a growing appreciation of the wide range of sleep-wake disturbances that occur frequently in Parkinson's disease. These are known to be associated with a range of motor and non-motor symptoms and significantly impact not only on the quality of life of the patient, but also on their bed partner. The underlying causes for fragmented sleep and daytime somnolence are no doubt multifactorial but there is clear evidence for circadian disruption in Parkinson's disease. This appears to be occurring not only as a result of the neuropathological changes that occur across a distributed neural network, but even down to the cellular level. Such observations indicate that circadian changes may in fact be a driver of neurodegeneration, as well as a cause for some of the sleep-wake symptoms observed in Parkinson's disease. Thus, efforts are now required to evaluate approaches including the prescription of precision medicine to modulate photoreceptor activation ratios that reflect daylight inputs to the circadian pacemaker, the use of small molecules to target clock genes, the manipulation of orexin pathways that could help restore the circadian system, to offer novel symptomatic and novel disease modifying strategies.

Obstructive sleep apnea heterogeneity and autonomic function: a role for heart rate variability in therapy selection and efficacy monitoring

Obstructive sleep apnea is a highly prevalent sleep-related breathing disorder, resulting in a disturbed breathing pattern, changes in blood gases, abnormal autonomic regulation, metabolic fluctuation, poor neurocognitive performance, and increased cardiovascular risk. With broad inter-individual differences recognised in risk factors, clinical symptoms, gene expression, physiological characteristics, and health outcomes, various obstructive sleep apnea subtypes have been identified. Therapeutic efficacy and its impact on outcomes, particularly for cardiovascular consequences, may also vary depending on these features in obstructive sleep apnea. A number of interventions such as positive airway pressure therapies, oral appliance, surgical treatment, and pharmaceutical options are available in clinical practice. Selecting an effective obstructive sleep apnea treatment and therapy is a challenging medical decision due to obstructive sleep apnea heterogeneity and numerous treatment modalities. Thus, an objective marker for clinical evaluation is warranted to estimate the treatment response in patients with obstructive sleep apnea. Currently, while the Apnea-Hypopnea Index is used for severity assessment of obstructive sleep apnea and still considered a major guide to diagnosis and managements of obstructive sleep apnea, the Apnea-Hypopnea Index is not a robust marker of symptoms, function, or outcome improvement. Abnormal cardiac autonomic modulation can provide additional insight to better understand obstructive sleep apnea phenotyping. Heart rate variability is a reliable neurocardiac tool to assess altered autonomic function and can also provide cardiovascular information in obstructive sleep apnea. Beyond the Apnea-Hypopnea Index, this review aims to discuss the role of heart rate variability as an indicator and predictor of therapeutic efficacy to different modalities in order to optimise tailored treatment for obstructive sleep apnea.

Orexin Receptor Antagonism: Normalizing Sleep Architecture in Old Age and Disease

Sleep is essential for human well-being, yet the quality and quantity of sleep reduce as age advances. Older persons (>65 years old) are more at risk of disorders accompanied and/or exacerbated by poor sleep. Furthermore, evidence supports a bidirectional relationship between disrupted sleep and Alzheimer's disease (AD) or related dementias. Orexin/hypocretin neuropeptides stabilize wakefulness, and several orexin receptor antagonists (ORAs) are approved for the treatment of insomnia in adults. Dysregulation of the orexin system occurs in aging and AD, positioning ORAs as advantageous for these populations. Indeed, several clinical studies indicate that ORAs are efficacious hypnotics in older persons and dementia patients and, as in adults, are generally well tolerated. ORAs are likely to be more effective when administered early in sleep/wake dysregulation to reestablish good sleep/wake-related behaviors and reduce the accumulation of dementia-associated proteinopathic substrates. Improving sleep in aging and dementia represents a tremendous opportunity to benefit patients, caregivers, and health systems.

Insomnia and related mental health conditions: Essential neurobiological underpinnings towards reduced polypharmacy utilization rates

Insomnia represents a significant public health burden, with a 10% prevalence in the general population. Reduced sleep affects social and working functioning, productivity, and patient's quality of life, leading to a total of $100 billion per year in direct and indirect healthcare costs. Primary insomnia is unrelated to any other mental or medical illness; secondary insomnia co-occurs with other underlying medical, iatrogenic, or mental conditions. Epidemiological studies found a 40-50% comorbidity prevalence between insomnia and psychiatric disorders, suggesting a high relevance of mental health in insomniacs. Sleep disturbances also worsen the outcomes of several psychiatric disorders, leading to more severe psychopathology and incomplete remission, plausibly contributing to treatment-resistant conditions. Insomnia and psychiatric disorder coexistence can lead to polypharmacy, namely, the concurrent use of two or more medications in the same patient, regardless of their purpose or rationale. Polypharmacy increases the risk of using unnecessary drugs, the likelihood of drug interactions and adverse events, and reduces the patient's compliance due to regimen complexity. The workup of insomnia must consider the patient's sleep habits and inquire about any medical and mental concurrent conditions that must be handled to allow insomnia to be remitted adequately. Monotherapy or limited polypharmacy should be preferred, especially in case of multiple comorbidities, promoting multipurpose molecules with sedative properties and with bedtime administration. Also, non-pharmacological interventions for insomnia, such as sleep hygiene, relaxation training and Cognitive Behavioral Therapy may be useful in secondary insomnia to confront behaviors and thoughts contributing to insomnia and help optimizing the pharmacotherapy. However, insomnia therapy should always be patient-tailored, considering drug indications, contraindications, and pharmacokinetics, besides insomnia phenotype, clinical picture, patient preferences, and side effect profile.

Orexin 2 receptor antagonism sex-dependently improves sleep/wakefulness and cognitive performance in tau transgenic mice

BACKGROUND AND PURPOSE

Tau pathology contributes to a bidirectional relationship between sleep disruption and neurodegenerative disease. Tau transgenic rTg4510 mice model tauopathy symptoms, including sleep/wake disturbances, which manifest as marked hyperarousal. This phenotype can be prevented by early transgene suppression; however, whether hyperarousal can be rescued after onset is unknown.

EXPERIMENTAL APPROACH

Three 8-week experiments were conducted with wild-type and rTg4510 mice after age of onset of hyperarousal (4.5 months): (1) Tau transgene suppression with doxycycline (200 ppm); (2) inactive phase rapid eye movement (REM) sleep enhancement with the dual orexin receptor antagonist suvorexant (50 mg·kg-1 ·day-1 ); or (3) Active phase non-NREM (NREM) and REM sleep enhancement using the selective orexin 2 (OX2 ) receptor antagonist MK-1064 (40 mg·kg-1 ·day-1 ). Sleep was assessed using polysomnography, cognition using the Barnes maze, and tau pathology using immunoblotting and/or immunohistochemistry.

KEY RESULTS

Tau transgene suppression improved tauopathy and hippocampal-dependent spatial memory, but did not modify hyperarousal. Pharmacological rescue of REM sleep deficits did not improve spatial memory or tau pathology. In contrast, normalising hyperarousal by increasing both NREM and REM sleep via OX2 receptor antagonism restored spatial memory, independently of tauopathy, but only in male rTg4510 mice. OX2 receptor antagonism induced only short-lived hypnotic responses in female rTg4510 mice and did not improve spatial memory, indicating a tau- and sex-dependent disruption of OX2 receptor signalling.

CONCLUSIONS AND IMPLICATIONS

Pharmacologically reducing hyperarousal corrects tau-induced sleep/wake and cognitive deficits. Tauopathy causes sex-dependent disruptions of OX2 receptor signalling/function, which may have implications for choice of hypnotic therapeutics in tauopathies.

Daily treatment with the dual orexin receptor antagonist DORA-12 during oxycodone abstinence decreases oxycodone conditioned reinstatement

Chronic opioid use disturbs circadian rhythm and sleep, encouraging opioid use and relapse. The orexin (OX) system is recruited by opioids and regulates physiological processes including sleep. Dual OX receptor antagonists (DORAs), developed for insomnia treatment, may relieve withdrawal-associated sleep disturbances. This study investigated whether DORA-12, a recently developed DORA, reduces physiological activity disturbances during oxycodone abstinence and consequently prevents oxycodone-seeking behavior. Male and female Wistar rats were trained to intravenously self-administer oxycodone (0.15 mg/kg, 21 sessions; 8 h/session) in the presence of a contextual/discriminative stimulus (SD). The rats were subsequently housed individually (22 h/day) to monitor activity, food and water intake. They received DORA-12 (0-30 mg/kg, p.o.) after undergoing daily 1-h extinction training (14 days). After extinction, the rats were tested for oxycodone-seeking behavior elicited by the SD. Hypothalamus sections were processed to assess oxycodone- or DORA-12-associated changes to the OX cell number. In males, oxycodone-associated increases in activity during the light-phase, reinstatement, and decreases in the number of OX cells observed in the vehicle-treated group were not observed with DORA-12-treatment. Oxycodone-associated increases in light-phase food and water intake were not observed by day 14 of 3 mg/kg DORA-12-treatment and dark-phase water intake was increased across treatment days. In females, OX cell number was unaffected by oxycodone or DORA-12. Three and 30 mg/kg DORA-12 increased females' day 7 dark-phase activity and decreased reinstatement. Thirty mg/kg DORA-12 reduced oxycodone-associated increases in light-phase food and water intake. The results suggest that DORA-12 improves oxycodone-induced disruptions to physiological activities and reduces relapse.

Pharmacological interventions targeting α-synuclein aggregation triggered REM sleep behavior disorder and early development of Parkinson's disease

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia characterized by elevated motor behaviors and dream enactments in REM sleep, often preceding the diagnosis of Parkinson's disease (PD). As RBD could serve as a biomarker for early PD developments, pharmacological interventions targeting α-synuclein aggregation triggered RBD could be applied toward early PD progression. However, robust therapeutic guidelines toward PD-induced RBD are lacking, owing in part to a historical paucity of effective treatments and trials. We reviewed the bidirectional links between α-synuclein neurodegeneration, progressive sleep disorders, and RBD. We highlighted the correlation between RBD development, α-synuclein aggregation, and neuronal apoptosis in key brainstem regions involved in REM sleep atonia maintenance. The current pharmacological intervention strategies targeting RBD and their effects on progressive PD are discussed, as well as current treatments for progressive neurodegeneration and their effects on RBD. We also evaluated emerging and potential pharmacological solutions to sleep disorders and developing synucleinopathies. This review provides insights into the mechanisms and therapeutic targets underlying RBD and PD, and explores bidirectional treatment effects for both diseases, underscoring the need for further research in this area.

Rethinking the Role of Orexin in the Regulation of REM Sleep and Appetite

Orexin plays a significant role in the modulation of REM sleep, as well as in the regulation of appetite and feeding. This review explores, first, the current evidence on the role of orexin in the modulation of sleep and wakefulness and highlights that orexin should be considered essentially as a neurotransmitter inhibiting REM sleep and, to a much lesser extent, a wake promoting agent. Subsequently, the relationship between orexin, REM sleep, and appetite regulation is examined in detail, shedding light on their interconnected nature in both physiological conditions and diseases (such as narcolepsy, sleep-related eating disorder, idiopathic hypersomnia, and night eating syndrome). Understanding the intricate relationship between orexin, REM sleep, and appetite regulation is vital for unraveling the complex mechanisms underlying sleep-wake patterns and metabolic control. Further research in this field is encouraged in order to pave the way for novel therapeutic approaches to sleep disorders and metabolic conditions associated with orexin dysregulation.

Protocol for a randomized controlled study examining the role of rapid eye movement sleep in fear-related mechanisms: rapid eye movement fragmentation and fear inhibition in adults with insomnia disorders before and after cognitive behavioral therapy for insomnia

Insomnia confers a 2.5-to-3-fold risk of developing posttraumatic stress disorder (PTSD) after a traumatic event. The mechanism underlying this increased risk, however, remains unknown. We postulate insomnia may contribute to PTSD by disrupting rapid eye movement (REM) sleep, as REM sleep disruption has been shown to impair fear inhibitory processes, which are central to the natural recovery from trauma. To test this hypothesis, the following protocol aims to: (1) examine the relationship between REM sleep and fear inhibition in insomnia, and (2) examine whether reducing REM fragmentation by treating insomnia, in turn, improves fear inhibition. Ninety-two adults with Insomnia Disorder will be block randomized (1:1; stratified by sex) to an active treatment (7 weekly sessions of Cognitive Behavioral Therapy for Insomnia (CBT-I) via telehealth) or waitlist control condition. REM sleep (latent variable derived from REM %, REM efficiency, and REM latency) and fear inhibition (i.e. safety signal and extinction recall) will be assessed pre- and post-treatment in a 4 night/3 day testing protocol via at-home polysomnography and the fear-potentiated startle paradigm, respectively. Fear extinction recall will serve as the primary outcome, while safety signal recall will serve as the secondary outcome. In summary, this study aims to test an underlying mechanism potentially explaining why insomnia greatly increases PTSD risk, while demonstrating an existing clinical intervention (CBT-I) can be used to improve this mechanism. Findings will have potential clinical implications for novel approaches in the prevention, early intervention, and treatment of PTSD.

Clinical Spectrum and Trajectory of Innovative Therapeutic Interventions for Insomnia: A Perspective

Increasing incidences of insomnia in adults, as well as the aging population, have been reported for their negative impact on the quality of life. Insomnia episodes may be associated with neurocognitive, musculoskeletal, cardiovascular, gastrointestinal, renal, hepatic, and metabolic disorders. Epidemiological evidence also revealed the association of insomnia with oncologic and asthmatic complications, which has been indicated as bidirectional. Two therapeutic approaches including cognitive behavioral therapy (CBT) and drugs-based therapies are being practiced for a long time. However, the adverse events associated with drugs limit their wide and long-term application. Further, Traditional Chinese medicine, acupressure, and pulsed magnetic field therapy may also provide therapeutic relief. Notably, the recently introduced cryotherapy has been demonstrated as a potential candidate for insomnia which could reduce pain, by suppressing oxidative stress and inflammation. It seems that the synergistic therapeutic approach of cryotherapy and the above-mentioned approaches might offer promising prospects to further improve efficacy and safety. Considering these facts, this perspective presents a comprehensive summary of recent advances in pathological aetiologies of insomnia including COVID-19, and its therapeutic management with a greater emphasis on cryotherapy.

Daridorexant, a Recently Approved Dual Orexin Receptor Antagonists (DORA) in Treatment of Insomnia

Insomnia is one of the major challenges in medical science nowadays as it leads to great socio-economic burden by impairing daytime function as well as the development of exhaustion, depression, and memory disturbance in affected individuals. Several important classes of drugs have been tried, including the BZDs and non-BZD hypnotics. Available drugs to combat this disease have the limitations of abuse potential, tolerance, and cognitive impairment. In some instances, withdrawal symptoms have been observed upon the abrupt cessation of those drugs. The Orexin system has been very recently targeted as a therapeutic option to overcome those limitations. Treatment of insomnia with Daridorexant as a Dual Orexin Receptor Antagonist (DORA) has been evaluated in several preclinical and clinical studies. Available information obtained from those studies has shown a promising future for this drug in the management of insomnia. Beyond its effectiveness in insomnia, it has been successfully used in patients suffering from obstructive sleep apnoea, chronic obstructed airway disease (COAD), Alzheimer's disease (AD), hypertension, and cardiovascular disorders. Larger studies need to address the safety issues as well as obtain robust pharmacovigilance information to safeguard the risk-benefit aspect of this drug in insomniac adults.

Daridorexant in Insomnia Disorder: A Profile of Its Use

Daridorexant (Quviviq™) is a useful option for the treatment of insomnia disorder, which has shown efficacy in younger and older adults. It antagonises the orexin receptors, thereby reducing the wake drive. Daridorexant is the first dual orexin receptor antagonist to be approved for the treatment of chronic insomnia in the EU and has been approved for insomnia in the USA. In phase 3 clinical trials, daridorexant dose-dependently improved objective latency to persistent sleep, objective wake time after sleep onset, subjective total sleep time and, at the 50 mg dose, subjective daytime functioning compared with placebo. Daridorexant was generally well tolerated. Adverse events (AEs) commonly associated with insomnia drugs, such as somnolence, fatigue and dizziness, occurred at a similar or slightly greater frequency with daridorexant than with placebo. Falls occurred at a similar or lower frequency with daridorexant than with placebo. Most AEs were mild in severity and the incidence was not dose-dependent. The efficacy of daridorexant was maintained during a 12-month extension trial, with no new safety or tolerability concerns.

Dual orexin receptor antagonists for insomnia in youth with neurodevelopmental disorders: a case series and review

Insomnia is a common, impairing, and difficult-to-treat comorbidity in children with neurodevelopmental disorders (NDDs). Behavioral interventions can be challenging because of developmental and behavioral features that interfere with treatment. Medication management also can be difficult due to a high burden of side effects, a high rate of paradoxical responses, and frequent treatment resistance. Therefore, new treatment options for insomnia in children with NDDs are needed. Dual orexin receptor antagonists (DORAs) are a relatively new class of pharmacotherapeutics that induce sleep by inhibiting the orexin signaling pathway. To date, there is little safety or efficacy data on the use of DORAs in children with NDDs. We present four patients with NDDs and insomnia that we treated with the DORA, suvorexant. We found that patients had a wide range of responses, with one patient displaying a robust improvement in sleep onset and maintenance, while another had significant improvement in insomnia symptoms on combination therapy with trazodone. Our final two patients had mild or no benefit from suvorexant therapy. Further research is necessary to establish the safety and efficacy of DORAs in this population and to identify predictive factors, such as specific neurogenetic diagnoses or clinical features, of a positive treatment response.

Targeting Orexin Receptors for the Treatment of Insomnia: From Physiological Mechanisms to Current Clinical Evidence and Recommendations

After a detailed description of orexins and their roles in sleep and other medical disorders, we discuss here the current clinical evidence on the effects of dual (DORAs) or selective (SORAs) orexin receptor antagonists on insomnia with the aim to provide recommendations for their further assessment in a context of personalized and precision medicine. In the last decade, many trials have been conducted with orexin receptor antagonists, which represent an innovative and valid therapeutic option based on the multiple mechanisms of action of orexins on different biological circuits, both centrally and peripherally, and their role in a wide range of medical conditions which are often associated with insomnia. A very interesting aspect of this new category of drugs is that they have limited abuse liability and their discontinuation does not seem associated with significant rebound effects. Further studies on the efficacy of DORAs are required, especially on children and adolescents and in particular conditions, such as menopause. Which DORA is most suitable for each patient, based on comorbidities and/or concomitant treatments, should be the focus of further careful research. On the contrary, studies on SORAs, some of which seem to be appropriate also in insomnia in patients with psychiatric diseases, are still at an early stage and, therefore, do not allow to draw definite conclusions.

Suvorexant ameliorated sleep disturbance, opioid withdrawal, and craving during a buprenorphine taper

Increased orexin/hypocretin signaling is implicated in opioid withdrawal, sleep disturbances, and drug-seeking behaviors. This study examined whether a dual-orexin receptor antagonist would improve sleep and withdrawal outcomes when compared with placebo during a buprenorphine/naloxone taper. Thirty-eight participants with opioid use disorder were recruited to a clinical research unit and maintained on 8/2 to 16/4 mg of buprenorphine/naloxone treatment for 3 days before being randomized to 20 mg of suvorexant (n = 14), 40 mg of suvorexant (n = 12), or placebo (n = 12); 26 individuals completed the study. After randomization, participants underwent a 4-day buprenorphine/naloxone taper and 4-day post-taper observation period. Total sleep time (TST) was collected nightly with a wireless electroencephalography device and wrist-worn actigraphy; opioid withdrawal symptoms were assessed via the Subjective Opiate Withdrawal Scale (SOWS); and abuse potential was assessed on a 0- to 100-point visual analog scale of "High" every morning. A priori outcomes included two-group (collapsing suvorexant doses versus placebo) and three-group comparisons of area-under-the-curve (AUC) scores for TST, SOWS, and High. In two-group comparisons, participants receiving suvorexant displayed increased TST during the buprenorphine/naloxone taper and decreased SOWS during the post-taper period. In three-group comparisons, participants receiving 20 mg of suvorexant versus placebo displayed increased AUC for TST during the buprenorphine/naloxone taper, but there was no difference in SOWS among groups. There was no evidence of abuse potential in two- or three-group analyses. The results suggest that suvorexant might be a promising treatment for sleep and opioid withdrawal in individuals undergoing a buprenorphine/naloxone taper.

The orexin story, sleep and sleep disturbances

The orexins, also known as hypocretins, are two neuropeptides (orexin A and B or hypocretin 1 and 2) produced by a few thousand neurons located in the lateral hypothalamus that were independently discovered by two research groups in 1998. Those two peptides bind two receptors (orexin/hypocretin receptor 1 and receptor 2) that are widely distributed in the brain and involved in the central physiological regulation of sleep and wakefulness, orexin receptor 2 having the major role in the maintenance of arousal. They are also implicated in a multiplicity of other functions, such as reward seeking, energy balance, autonomic regulation and emotional behaviours. The destruction of orexin neurons is responsible for the sleep disorder narcolepsy with cataplexy (type 1) in humans, and a defect of orexin signalling also causes a narcoleptic phenotype in several animal species. Orexin discovery is unprecedented in the history of sleep research, and pharmacological manipulations of orexin may have multiple therapeutic applications. Several orexin receptor antagonists were recently developed as new drugs for insomnia, and orexin agonists may be the next-generation drugs for narcolepsy. Given the broad range of functions of the orexin system, these drugs might also be beneficial for treating various conditions other than sleep disorders in the near future.

Hypocretins (orexins): The ultimate translational neuropeptides

The hypocretins (Hcrts), also known as orexins, are two neuropeptides produced exclusively in the lateral hypothalamus. They act on two specific receptors that are widely distributed across the brain and involved in a myriad of neurophysiological functions that include sleep, arousal, feeding, reward, fear, anxiety and cognition. Hcrt cell loss in humans leads to narcolepsy with cataplexy (narcolepsy type 1), a disorder characterized by intrusions of sleep into wakefulness, demonstrating that the Hcrt system is nonredundant and essential for sleep/wake stability. The causal link between Hcrts and arousal/wakefulness stabilisation has led to the development of a new class of drugs, Hcrt receptor antagonists to treat insomnia, based on the assumption that blocking orexin-induced arousal will facilitate sleep. This has been clinically validated: currently, two Hcrt receptor antagonists are approved to treat insomnia (suvorexant and lemborexant), with a New Drug Application recently submitted to the US Food and Drug Administration for a third drug (daridorexant). Other therapeutic applications under investigation include reduction of cravings in substance-use disorders and prevention of neurodegenerative disorders such as Alzheimer's disease, given the apparent bidirectional relationship between poor sleep and worsening of the disease. Circuit neuroscience findings suggest that the Hcrt system is a hub that integrates diverse inputs modulating arousal (e.g., circadian rhythms, metabolic status, positive and negative emotions) and conveys this information to multiple output regions. This neuronal architecture explains the wealth of physiological functions associated with Hcrts and highlights the potential of the Hcrt system as a therapeutic target for a number of disorders. We discuss present and future possible applications of drugs targeting the Hcrt system for the treatment of circuit-related neuropsychiatric and neurodegenerative conditions.

Orexin Signaling: A Complex, Multifaceted Process

The orexin system comprises two G protein-coupled receptors, OX1 and OX2 receptors (OX1R and OX2R, respectively), along with two endogenous agonists cleaved from a common precursor (prepro-orexin), orexin-A (OX-A) and orexin-B (OX-B). For the receptors, a complex array of signaling behaviors has been reported. In particular, it becomes obvious that orexin receptor coupling is very diverse and can be tissue-, cell- and context-dependent. Here, the early signal transduction interactions of the orexin receptors will be discussed in depth, with particular emphasis on the direct G protein interactions of each receptor. In doing so, it is evident that ligands, additional receptor-protein interactions and cellular environment all play important roles in the G protein coupling profiles of the orexin receptors. This has potential implications for our understanding of the orexin system's function in vivo in both central and peripheral environments, as well as the development of novel agonists, antagonists and possibly allosteric modulators targeting the orexin system.

Differential sleep/wake response and sex effects following acute suvorexant, MK-1064 and zolpidem administration in the rTg4510 mouse model of tauopathy

Background and Purpose

Transgenic mouse models of tauopathy display prominent sleep/wake disturbances which manifest primarily as a hyperarousal phenotype during the active phase, suggesting that tau pathology contributes to sleep/wake changes. However, no study has yet investigated the effect of sleep‐promoting compounds in these models. Such information has implications for the use of hypnotics as potential therapeutic tools in tauopathy‐related disorders.

Experimental Approach

This study examined polysomnographic recordings in 6‐6.5‐month‐old male and female rTg4510 mice following acute administration of suvorexant (50 mg·kg⁻¹), MK‐1064 (30 mg·kg⁻¹) or zolpidem (10 mg·kg⁻¹), administered at the commencement of the active phase.

Key Results

Suvorexant, a dual OX receptor antagonist, promoted REM sleep in rTg4510 mice, without affecting wake or NREM sleep. MK‐1064, a selective OX₂ receptor antagonist, reduced wake and increased NREM and total sleep time. MK‐1064 normalised the hyperarousal phenotype of male rTg4510 mice, whereas female rTg4510 mice exhibited a more transient response. Zolpidem, a GABA_A receptor positive allosteric modulator, decreased wake and increased NREM sleep in both male and female rTg4510 mice. Of the three compounds, the OX₂ receptor antagonist MK‐1064 promoted and normalised physiologically normal sleep, especially in male rTg4510 mice.

Conclusions and Implications

Our findings indicate that hyperphosphorylated tau accumulation and associated hyperarousal does not significantly alter the responses of tauopathy mouse models to hypnotics. However, the sex differences observed in the sleep/wake response of rTg4510 mice to MK‐1064, but not suvorexant or zolpidem, raise questions about therapeutic implications for the use of OX₂ receptor antagonists in human neurodegenerative disorders.

Orexin receptors in GtoPdb v.2021.3

Orexin receptors (nomenclature as agreed by the NC-IUPHAR Subcommittee on Orexin receptors [42]) are activated by the endogenous polypeptides orexin-A and orexin-B (also known as hypocretin-1 and -2; 33 and 28 aa) derived from a common precursor, preproorexin or orexin precursor, by proteolytic cleavage and some typical peptide modifications [109]. Currently the only orexin receptor ligands in clinical use are suvorexant and lemborexant, which are used as hypnotics. Orexin receptor crystal structures have been solved [134, 133, 54, 117, 46].

Hypocretin/Orexin Receptor Pharmacology and Sleep Phases

The hypocretins/orexins are two excitatory neuropeptides, alternately called HCRT1 or orexin-A and HCRT2 or orexin-B, that are the endogenous ligands for two G-protein-coupled receptors, HCRTR1/OX1R and HCRTR2/OX2R. Shortly after the discovery of this system, degeneration of hypocretin/orexin-producing neurons was implicated in the etiology of the sleep disorder narcolepsy. The involvement of this system in a disorder characterized by the loss of control over arousal state boundaries also suggested its role as a critical component of endogenous sleep-wake regulatory circuitry. The broad projections of the hypocretin/orexin-producing neurons, along with differential expression of the two receptors in the projection fields of these neurons, suggest distinct roles for these receptors. While HCRTR1/OX1R is associated with regulation of motivation, reward, and autonomic functions, HCRTR2/OX2R is strongly linked to sleep-wake control. The association of hypocretin/orexin with these physiological processes has led to intense interest in the therapeutic potential of compounds targeting these receptors. Agonists and antagonists for the hypocretin/orexin receptors have shown potential for the treatment of disorders of excessive daytime somnolence and nocturnal hyperarousal, respectively, with the first antagonists approved by the US Food and Drug Administration (FDA) in 2014 and 2019 for the treatment of insomnia. These and related compounds have also been useful tools to advance hypocretin/orexin neurobiology.

Manipulation of REM sleep via orexin and GABAA receptor modulators differentially affects fear extinction in mice: effect of stable versus disrupted circadian rhythm

Sleep disruption, and especially REM sleep disruption, is associated with fear inhibition impairment in animals and humans. The REM sleep-fear inhibition relationship raises concern for individuals with PTSD, whose sleep disturbance is commonly treated with hypnotics which disrupt and/or decrease REM sleep, such as benzodiazepines or 'Z-drugs'. Here, we examined the effects of the Z-drug zolpidem, a GABAA receptor positive allosteric modulator, as well as suvorexant, an orexin receptor antagonist (hypnotics which decrease and increase REM sleep, respectively) in the context of circadian disruption in murine models of fear inhibition-related processes (i.e., fear extinction and safety learning). Adult male C57Bl/6J mice completed fear and safety conditioning before undergoing shifts in the light-dark (LD) cycle or maintaining a consistent LD schedule. Fear extinction and recall of conditioned safety were thereafter tested daily. Immediately prior to onset of the light phase between testing sessions, mice were treated with zolpidem, suvorexant, or vehicle (methylcellulose). EEG/EMG analysis showed temporal distribution of REM sleep was misaligned during LD cycle-shifts, while REM sleep duration was preserved. Suvorexant increased REM sleep and improved fear extinction rate, relative to zolpidem, which decreased REM sleep. Survival analysis demonstrated LD shifted mice treated with suvorexant were faster to achieve complete extinction than vehicle and zolpidem-treated mice in the LD shifted condition. By contrast, retention of conditioned safety memory was not influenced by either treatment. This study thus provides preclinical evidence for the potential clinical utility of hypnotics which increase REM sleep for fear extinction after PTSD-relevant sleep disturbance.

The Dual Orexin Receptor Antagonist DORA-22 Improves Mild Stress-induced Sleep Disruption During the Natural Sleep Phase of Nocturnal Rats

Dual orexinergic antagonists (DORAs) have been recently developed as a pharmacotherapy alternative to established hypnotics. Hypnotics are largely evaluated in preclinical rodent models in the dark/active period yet should be ideally evaluated in the light/inactive period, analogous to when sleep disruption occurs in humans. We describe here the hypnotic efficacy of DORA-22 in rodent models of sleep disturbance produced by cage changes in the light/inactive period. Rats were administered DORA-22 or the GABA receptor-targeting hypnotic eszopiclone early in the light period, then exposed to six hourly clean cage changes with measurements of NREM sleep onset latency. Both compounds initially promoted sleep (hours 1 and 2), with DORA-22 exhibiting a more rapid hypnotic onset; and exhibited extended efficacy, evident six hours after administration in a sleep latencies test. A common complaint concerning hypnotic use is lingering hypersomnolence, and this is a concern in pharmacotherapy of the elderly. A second study was designed to determine a minimal dose of DORA-22 which would initially promote sleep but exhibit minimal extended hypnotic effect.Animals were administered DORA-22, then exposed for six hours to a single cage previously dirtied by a conspecific, followed by return to home cage. EEG measures indicated that all DORA-22 doses largely promoted sleep in the first hour. The lowest dose (1 mg/kg) did not decrease sleep onset latency at the six-hour timepoint, suggesting no residual hypersomnolence. We described here DORA-22 hypnotic efficacy during the normal sleep period of nocturnal rats, and demonstrate that well-chosen (low) hypnotic doses of DORA-22 may be hypnotically effective yet have minimal lingering effects.

Pharmacological Management of Insomnia

Insomnia is a highly prevalent condition associated with significant morbidity, reduction in quality of life, and increase in healthcare costs, and is a risk factor for multiple physical and mental disorders. The primary treatment modality is cognitive behavioral therapy for insomnia (CBT-I) but this is associated with difficulties with access and higher cost as well as poor response in some patients. Therefore, pharmacotherapy for insomnia is common and hypnotic agents are among the most frequently prescribed medications in the United States. Older medications for insomnia are limited by their side effect burden and narrow therapeutic window. Newer hypnotics, on the other hand, have been shown to have a better safety profile and longer term efficacy. While some studies have shown that long-term hypnotic use is associated with adverse outcomes, the current evidence is equivocal. The decision to treat chronic insomnia disorder with long-term hypnotics should be individualized and balance the potential risks of continuing hypnotic medication use with the risks of untreated persistent insomnia and associated functional limitations. This clinical review discusses the currently available medication options to treat insomnia, their mechanisms of action, dosing, and side effect profiles. This review also provides guidance on long-term management of hypnotics and the use of these medications in the elderly, those with medical comorbidities, and other special populations.

Advances in the Treatment of Chronic Insomnia: A Narrative Review of New Nonpharmacologic and Pharmacologic Therapies

Chronic insomnia disorder, which affects 6-10% of the population, is diagnostically characterized by ongoing difficulties with initiating or maintaining sleep occurring at least three times per week, persisting for at least 3 months, and associated with daytime impairment. While chronic insomnia is often considered a condition primarily related to impaired sleep, the disorder can also adversely affect domains of physical and mental health, quality of life, and daytime function, which highlights the importance of treating the multidimensional sleep disorder. Owing to misperceptions about the safety and effectiveness of treatment options, many individuals with insomnia may not seek professional treatment, and alternatively use ineffective home remedies or over-the-counter medications to improve sleep. Some physicians may even believe that insomnia is remediated by simply having the patient "get more sleep". Unfortunately, treatment of insomnia is not always that simple. The disorder's complex underlying pathophysiology warrants consideration of different nonpharmacologic and pharmacologic treatment options. Indeed, recent insights gained from research into the pathophysiology of insomnia have facilitated development of newer treatment approaches with more efficacious outcomes. This narrative review provides a summary of the diagnostic criteria and pathophysiology of insomnia and its subtypes. Further, this review emphasizes new and emerging nonpharmacologic and pharmacologic treatments for chronic insomnia, including recent enhancements in approaches to cognitive behavioral therapy for insomnia (CBT-I) and the new dual orexin receptor antagonist (DORA) pharmacologics. These advances in treatment have expanded the treatment options and are likely to result in improved outcomes in patients with chronic insomnia.

Sleep disorders and the hypothalamus

As early as the 1920s, pathological studies of encephalitis lethargica allowed Von Economo to correctly identify hypothalamic damage as crucial for the profound associated sleep-related symptoms that helped define the condition. Only over the last 3 decades, however, has the key role of the hypothalamus in sleep-wake regulation become increasingly recognized. As a consequence, a close relation between abnormal sleep symptomatology and hypothalamic pathology is now widely accepted for a variety of medical disorders. Narcolepsy is discussed in some detail as the cardinal primary sleep disorder that is caused directly and specifically by hypothalamic pathology, most notably destruction of hypocretin (orexin)-containing neurons. Thereafter, various conditions are described that most likely result from hypothalamic damage, in part at least, producing a clinical picture resembling (symptomatic) narcolepsy. Kleine-Levin syndrome is a rare primary sleep disorder with intermittent symptoms, highly suggestive of hypothalamic involvement but probably reflecting a wider pathophysiology. ROHHAD (rapid-onset obesity with hypothalamic dysfunction, hypoventilation, and autonomic dysregulation) and Prader-Willi syndrome are also covered as hypothalamic syndromes with prominent sleep-related symptoms. Finally, sleep issues in several endocrine disorders are briefly discussed.

Sleep disturbances and the speed of multimorbidity development in old age: results from a longitudinal population-based study

BACKGROUND

Sleep disturbances are prevalent among older adults and are associated with various individual diseases. The aim of this study was to investigate whether sleep disturbances are associated with the speed of multimorbidity development among older adults.

METHODS

Data were gathered from the Swedish National study of Aging and Care in Kungsholmen (SNAC-K), an ongoing population-based study of subjects aged 60+ (N = 3363). The study included a subsample (n = 1189) without multimorbidity at baseline (< 2 chronic diseases). Baseline sleep disturbances were derived from the Comprehensive Psychiatric Rating Scale and categorized as none, mild, and moderate-severe. The number of chronic conditions throughout the 9-year follow-up was obtained from clinical examinations. Linear mixed models were used to study the association between sleep disturbances and the speed of chronic disease accumulation, adjusting for sex, age, education, physical activity, smoking, alcohol consumption, depression, pain, and psychotropic drug use. We repeated the analyses including only cardiovascular, neuropsychiatric, or musculoskeletal diseases as the outcome.

RESULTS

Moderate-severe sleep disturbances were associated with a higher speed of chronic disease accumulation (ß/year = 0.142, p = 0.008), regardless of potential confounders. Significant positive associations were also found between moderate-severe sleep disturbances and neuropsychiatric (ß/year = 0.041, p = 0.016) and musculoskeletal (ß/year = 0.038, p = 0.025) disease accumulation, but not with cardiovascular diseases. Results remained stable when participants with baseline dementia, cognitive impairment, or depression were excluded.

CONCLUSION

The finding that sleep disturbances are associated with faster chronic disease accumulation points towards the importance of early detection and treatment of sleep disturbances as a possible strategy to reduce chronic multimorbidity among older adults.