Non–24-Hour Sleep–Wake Rhythm Disorder in Sighted and Blind Patients

Registry and survey of circadian rhythm sleep-wake disorder patients

Objective

Circadian Sleep Disorders Network has created a registry of circadian rhythm sleep-wake disorder (CRSWD) patients, and a survey of their experiences. The purpose of the registry is to provide volunteers willing to participate in research; the purpose of the survey is to fill some of the knowledge gaps on these disorders, including information on subjective patient experience and the efficacy and durability of treatments.Researchers are invited to contact Circadian Sleep Disorders Network for permission to use the registry to find potential research participants, and to further analyze the survey data.

Patients

Over 1627 patients have participated; 1298 have completed the entire survey. Here we present results based on the 479 clinically diagnosed CRSWD patients.

Methods

The survey covers a variety of topics relating to CRSWDs, including diagnosis, comorbidities, treatments, and work/educational accommodations.

Conclusions

Results of this survey diverged from much of the literature. More than half the participants reported tiredness even when sleeping on their preferred schedule. While depression may cause sleep problems, our data suggests that sleep/circadian problems often precede depression.There were more people suffering from sighted non-24-hour sleep-wake rhythm disorder than some of the literature would lead us to expect.Current treatments did not appear to be helpful to a large percentage of our participants. Most of them did not find light therapy helpful and nearly all participants who tried phase-delay chronotherapy reported at best only short-term improvement. A sizable proportion of people who tried phase-delay chronotherapy subsequently developed non-24-hour sleep-wake rhythm disorder.

ICNIRP Statement on Short Wavelength Light Exposure from Indoor Artificial Sources and Human Health

ABSTRACT

Concerns have been raised about the possibility of effects from exposure to short wavelength light (SWL), defined here as 380-550 nm, on human health. The spectral sensitivity of the human circadian timing system peaks at around 480 nm, much shorter than the peak sensitivity of daytime vision (i.e., 555 nm). Some experimental studies have demonstrated effects on the circadian timing system and on sleep from SWL exposure, especially when SWL exposure occurs in the evening or at night. The International Commission on Non-Ionizing Radiation Protection (ICNIRP) has identified a lack of consensus among public health officials regarding whether SWL from artificial sources disrupts circadian rhythm, and if so, whether SWL-disrupted circadian rhythm is associated with adverse health outcomes. Systematic reviews of studies designed to examine the effects of SWL on sleep and human health have shown conflicting results. There are many variables that can affect the outcome of these experimental studies. One of the main problems in earlier studies was the use of photometric quantities as a surrogate for SWL exposure. Additionally, the measurement of ambient light may not be an accurate measure of the amount of light impinging on the intrinsically photosensitive retinal ganglion cells, which are now known to play a major role in the human circadian timing system. Furthermore, epidemiological studies of long-term effects of chronic SWL exposure per se on human health are lacking. ICNIRP recommends that an analysis of data gaps be performed to delineate the types of studies needed, the parameters that should be addressed, and the methodology that should be applied in future studies so that a decision about the need for exposure guidelines can be made. In the meantime, ICNIRP supports some recommendations for how the quality of future studies might be improved.

Lighting the way: Exploring diurnal physical performance differences in school-aged visually impaired children and adolescents

Circadian rhythms play a pivotal role in governing various physiological processes, including physical performance. However, in individuals deprived of light perception, such as the blind, these circadian rhythms face disruption. This study aimed to explore the influence of disturbed circadian rhythms on short-term maximal physical performance in children and adolescents with visual impairment. Forty-five volunteers participated in this study, comprising 17 blind, 13 visually impaired, and 15 sighted participants. The participants underwent a series of tests assessing maximal isometric strength performance across two days. To mitigate the influence of morning session fatigue on the evening results, each participant group performed in two separate testing sessions (i.e. in the morning (7:00 h) and in the evening (17:00 h)) on non-consecutive days in a randomized and counterbalanced setting, with approximately 36 h of recovery time between sessions. To mitigate the impact of inter-individual differences on mean values and to account for the influence of age and sex on the studied variables, data were normalized. The outcomes revealed a significant diurnal variation in maximal isometric strength performance among sighted individuals, with peak performance observed in the evening. This pattern aligns with their well-entrained circadian rhythm. In contrast, blind and visually impaired individuals did not display significant diurnal variation, signaling disrupted circadian rhythms due to the absence of light perception. These findings emphasize the crucial consideration of circadian rhythms in assessments of physical performance, especially among participants with visual impairments.

Current Considerations in the Diagnosis and Treatment of Circadian Rhythm Sleep-Wake Disorders in Children

Circadian Rhythm Sleep-Wake Disorders (CRSWDs) are important sleep disorders whose unifying feature is a mismatch between the preferred or required times for sleep and wakefulness and the endogenous circadian drives for these. Their etiology, presentation, and treatment can be different in pediatric patients as compared to adults. Evaluation of these disorders must be performed while viewed through the lens of a patient's comorbid conditions. Newer methods of assessment promise to provide greater diagnostic clarity and critical insights into how circadian physiology affects overall health and disease states. Effective clinical management of CRSWDs is multimodal, requiring an integrated approach across disciplines. Therapeutic success depends upon appropriately timed nonpharmacologic and pharmacologic interventions. A better understanding of the genetic predispositions for and causes of CRSWDs has led to novel clinical opportunities for diagnosis and improved therapeutics.

The neurons that drive infradian sleep-wake and mania-like behavioral rhythms

Infradian mood and sleep-wake rhythms with periods of 48 hr and beyond have been observed in bipolar disorder (BD) subjects that even persist in time isolation, indicating an endogenous origin. Here we show that mice exposed to methamphetamine (Meth) in drinking water develop infradian locomotor rhythms with periods of 48 hr and beyond which extend to sleep length and mania-like behaviors in support of a model for cycling in BD. This cycling capacity is abrogated upon genetic disruption of DA production in DA neurons of the ventral tegmental area (VTA) or ablation of nucleus accumbens (NAc) projecting, dopamine (DA) neurons. Chemogenetic activation of NAc-projecting DA neurons leads to locomotor period lengthening in clock deficient mice, while cytosolic calcium in DA processes of the NAc was found fluctuating synchronously with locomotor behavior. Together, our findings argue that BD cycling relies on infradian rhythm generation that depends on NAc-projecting DA neurons.

Temperature compensation and entrainment in cyanobacteria circadian rhythm

Circadian rhythm is an endogenous rhythmic behavior of organisms used to adapt to the external environment. Although most biochemical reactions accelerate with increasing temperature, the period of circadian rhythms remains relatively stable across a range of temperature, a phenomenon known as temperature compensation. Meanwhile, circadian rhythms can be reset by environmental signals, such as daily periodic light or temperature, a phenomenon known as entrainment. Cyanobacteria are the simplest organisms to have circadian rhythms. The effect of light on cyanobacteria circadian rhythm has been widely studied with mathematical models. However, the effect of temperature on cyanobacteria circadian rhythm and the mechanisms of temperature compensation and entrainment are far from clear. In this paper, we apply a recent model to incorporate temperature dependence by Van't Hoff rule. With numerical simulation, we study the temperature compensation and entrainment in detail. The results show that the system can exhibit temperature compensation when the post-transcription process is insensitive to temperature. The temperature compensation is caused by the cancellation of the increase of amplitude and the acceleration of speed, resulting in the stable period, when the temperature rises. The system can also exhibit temperature entrainment in constant light in a very limited temperature range. When the periodic light is added simultaneously to simulate more realistic environment, the temperature range of entrainment is greatly improved. The results also suggest that long-day condition is conducive to entrainment. The findings of this paper provide a theoretical reference for biological research and help us understand the dynamical mechanisms of cyanobacteria circadian rhythm.

Delayed sleep-wake phase disorder and its related sleep behaviors in the young generation

Delayed sleep-wake phase disorder (DSWPD) is a sleep disorder in which the habitual sleep-wake timing is delayed, resulting in difficulty in falling asleep and waking up at the desired time. Patients with DSWPD frequently experience fatigue, impaired concentration, sleep deprivation during weekdays, and problems of absenteeism, which may be further complicated by depressive symptoms. DSWPD is typically prevalent during adolescence and young adulthood. Although there are no studies comparing internationally, the prevalence of DSWPD is estimated to be approximately 3% with little racial differences between Caucasians and Asians. The presence of this disorder is associated with various physiological, genetic and psychological as well as behavioral factors. Furthermore, social factors are also involved in the mechanism of DSWPD. Recently, delayed sleep phase and prolonged sleep duration in the young generation have been reported during the period of COVID-19 pandemic-related behavioral restrictions. This phenomenon raises a concern about the risk of a mismatch between their sleep-wake phase and social life that may lead to the development of DSWPD after the removal of these restrictions. Although the typical feature of DSWPD is a delay in circadian rhythms, individuals with DSWPD without having misalignment of objectively measured circadian rhythm markers account for approximately 40% of the cases, wherein the psychological and behavioral characteristics of young people, such as truancy and academic or social troubles, are largely involved in the mechanism of this disorder. Recent studies have shown that DSWPD is frequently comorbid with psychiatric disorders, particularly mood and neurodevelopmental disorders, both of which have a bidirectional association with the pathophysiology of DSWPD. Additionally, patients with DSWPD have a strong tendency toward neuroticism and anxiety, which may result in the aggravation of insomnia symptoms. Therefore, future studies should address the effectiveness of cognitive-behavioral approaches in addition to chronobiological approaches in the treatment of DSWPD.

Continuous positive airway pressure as an accurate marker for non-24-hour sleep-wake rhythm disorder

Non-24-h sleep-wake rhythm disorder is quite rare in sighted patients and frequently associated with psychiatric disorders. We report the case of a 46-year-old man with autism spectrum disorder (ASD) and agoraphobia who had been referred for a suspicion of obstructive sleep apnea syndrome (OSAS). Polysomnography and arterial blood gas confirmed moderate OSAS associated with hypoventilation. Continuous positive airway pressure (CPAP) was started on fixed mode with excellent results. At follow-up, his CPAP report data revealed an irregular sleep-wake rhythm with a progressive offset of sleep schedule and wake time delayed from 1 h from day to day. Melatonin (or agonist) is efficacious and safe for long-term treatment in ASD and circadian rhythm sleep-wake disorder (CRSWD) with light therapy and wakefulness promoting medication. This case underlines the importance to sensitise psychiatrists to sleep and CRSWD, and also that CPAP data offer a possible objective alternative to sleep diary.

Circadian rhythms and disorders of the timing of sleep

The daily alternation between sleep and wakefulness is one of the most dominant features of our lives and is a manifestation of the intrinsic 24 h rhythmicity underlying almost every aspect of our physiology. Circadian rhythms are generated by networks of molecular oscillators in the brain and peripheral tissues that interact with environmental and behavioural cycles to promote the occurrence of sleep during the environmental night. This alignment is often disturbed, however, by contemporary changes to our living environments, work or social schedules, patterns of light exposure, and biological factors, with consequences not only for sleep timing but also for our physical and mental health. Characterised by undesirable or irregular timing of sleep and wakefulness, in this Series paper we critically examine the existing categories of circadian rhythm sleep-wake disorders and the role of the circadian system in their development. We emphasise how not all disruption to daily rhythms is driven solely by an underlying circadian disturbance, and take a broader, dimensional approach to explore how circadian rhythms and sleep homoeostasis interact with behavioural and environmental factors. Very few high-quality epidemiological and intervention studies exist, and wider recognition and treatment of sleep timing disorders are currently hindered by a scarcity of accessible and objective tools for quantifying sleep and circadian physiology and environmental variables. We therefore assess emerging wearable technology, transcriptomics, and mathematical modelling approaches that promise to accelerate the integration of our knowledge in sleep and circadian science into improved human health.

Cross talk mechanism of disturbed sleep patterns in neurological and psychological disorders

The incidence and prevalence of sleep disorders continue to increase in the elderly populace, particularly those suffering from neurodegenerative and neuropsychiatric disorders. This not only affects the quality of life but also accelerates the progression of the disease. There are many reasons behind sleep disturbances in such patients, for instance, medication use, nocturia, obesity, environmental factors, nocturnal motor disturbances and depressive symptoms. This review focuses on the mechanism and effects of sleep dysfunction in neurodegenerative and neuropsychiatric disorders. Wherein we discuss disturbed circadian rhythm, signaling cascade and regulation of genes during sleep deprivation. Moreover, we explain the perturbation in brainwaves during disturbed sleep and the ocular perspective of neurodegenerative and neuropsychiatric manifestations in sleep disorders. Further, as the pharmacological approach is often futile and carries side effects, therefore, the non-pharmacological approach opens newer possibilities to treat these disorders and widens the landscape of treatment options for patients.

Circadian Rhythm Sleep-Wake Disorders in Older Adults

The timing, duration, and consolidation of sleep result from the interaction of the circadian timing system with a sleep-wake homeostatic process. When aligned and functioning optimally, this allows for wakefulness throughout the day and a long consolidated sleep episode at night. Changes to either the sleep regulatory process or how they interact can result in an inability to fall asleep at the desired time, difficulty remaining asleep, waking too early, and/or difficulty remaining awake throughout the day. This mismatch between the desired timing of sleep and the ability to fall asleep and remain asleep is a hallmark of a class of sleep disorders called the circadian rhythm sleep-wake disorders. In this updated article, we discuss typical changes in the circadian regulation of sleep with aging; how age influences the prevalence, diagnosis, and treatment of circadian rhythm sleep disorders; and how neurologic diseases in older patient impact circadian rhythms and sleep.

The neurophysiologic basis of the human sleep–wake cycle and the physiopathology of the circadian clock: a narrative review

The objectives of this review were to explain the neurologic processes that control the human sleep–wake cycle as well as the pathophysiology of the human circadian clock. Non-rapid eye movement and rapid eye movement sleep are the two main phases of sleep. When triggered by circadian input from the anterior hypothalamus and sleep–wake homeostatic information from endogenous chemical signals (example, adenosine), the ventrolateral preoptic nucleus initiates the onset of sleep. Arousal in which there is a conscious monitoring of the surroundings and the ability to respond to external stimuli is known as wakefulness. It contrasts the state of sleep, in which receptivity to external stimuli is reduced. The higher the synchronous firing rates of cerebral cortex neurons, the longer the brain has been awake. Sleep–wake disturbances induced by endogenous circadian system disruptions or desynchronization between internal and external sleep–wake cycles are known as circadian rhythm sleep–wake disorder (CRSWD). Patients with CRSWD usually report chronic daytime drowsiness and/or insomnia, which interferes with their activities. CRSWD is diagnosed based on the results of some functional evaluations, which include measuring the circadian phase using core body temperature, melatonin secretion timing, sleep diaries, actigraphy, and subjective experiences (example, using the Morningness–Eveningness Questionnaire). CRSWD is classified as a dyssomnia in the second edition of the International Classification of Sleep Disorders, with six subtypes: advanced sleep phase, delayed sleep phase, irregular sleep–wake, free running, jet lag, and shift work types. CRSWD can be temporary (due to jet lag, shift work, or illness) or chronic (due to delayed sleep–wake phase disorder, advanced sleep–wake phase disorder, non-24-h sleep–wake disorder, or irregular sleep–wake rhythm disorder). The inability to fall asleep and wake up at the desired time is a common symptom of all CRSWDs.

Non-24-Hour Sleep–Wake Disorder and Tasimelteon: A Review for Practitioners Who Work with Blind People

Introduction

This narrative review summarizes the biology of human circadian rhythms; details the epidemiology, clinical manifestation, and diagnosis of non-24-hour sleep–wake disorder (N24SWD); and reviews the efficacy of possible treatments.

Methods

Searches of targeted phrases, such as “non-24-hour sleep–wake disorder” and “tasimelteon,” were conducted on PubMed between December 2016 and March 2020.

Results

As the world’s population ages, health practitioners frequently work with people who are blind. Damage to the retinal ganglion cells that signal environmental irradiance levels to the suprachiasmatic nucleus prevents many of these individuals from synchronizing their internal clocks to the 24-hour day. As a result, they experience a condition called N24SWD, where the body’s circadian rhythms fall in and out of phase with the solar cycle. The ability to fall asleep and remain asleep is a complex process that depends on many variables, including the release of the neurohormone melatonin. Melatonin is produced at night and is a key regulator of regular sleep cycles. Periods of interrupted sleep, increased sleep latency, and reduced total sleep time occur when melatonin production peaks during daytime. Thus, many persons with N24SWD have difficulty maintaining normal schedules due in part to the mistimed release of melatonin. Randomized clinical trials have shown that melatonin receptor agonist tasimelteon is an effective therapy for individuals with N24SWD. Other treatments have varying efficacy profiles.

Conclusions

Although rare, N24SWD is a serious condition that can impair quality of life for blind persons. Tasimelteon appears to be a safe and efficacious treatment option.

Implications for practitioners

Practitioners can use this information to better understand why blind persons often report difficulties sleeping and to realize that therapeutic options are available to these individuals.

Human circadian variations

Circadian rhythms, present in most phyla across life, are biological oscillations occurring on a daily cycle. Since the discovery of their molecular foundations in model organisms, many inputs that modify this tightly controlled system in humans have been identified. Polygenic variations and environmental factors influence each person's circadian rhythm, contributing to the trait known as chronotype, which manifests as the degree of morning or evening preference in an individual. Despite normal variation in chronotype, much of society operates on a "one size fits all" schedule that can be difficult to adjust to, especially for certain individuals whose endogenous circadian phase is extremely advanced or delayed. This is a public health concern, as phase misalignment in humans is associated with a number of adverse health outcomes. Additionally, modern technology (such as electric lights and computer, tablet, and phone screens that emit blue light) and lifestyles (such as shift or irregular work schedules) are disrupting circadian consistency in an increasing number of people. Though medical and lifestyle interventions can alleviate some of these issues, growing research on endogenous circadian variability and sensitivity suggests that broader social changes may be necessary to minimize the impact of circadian misalignment on health.

Workshop report. Circadian rhythm sleep-wake disorders: gaps and opportunities

This White Paper presents the results from a workshop cosponsored by the Sleep Research Society (SRS) and the Society for Research on Biological Rhythms (SRBR) whose goals were to bring together sleep clinicians and sleep and circadian rhythm researchers to identify existing gaps in diagnosis and treatment and areas of high-priority research in circadian rhythm sleep-wake disorders (CRSWD). CRSWD are a distinct class of sleep disorders caused by alterations of the circadian time-keeping system, its entrainment mechanisms, or a misalignment of the endogenous circadian rhythm and the external environment. In these disorders, the timing of the primary sleep episode is either earlier or later than desired, irregular from day-to-day, and/or sleep occurs at the wrong circadian time. While there are incomplete and insufficient prevalence data, CRSWD likely affect at least 800,000 and perhaps as many as 3 million individuals in the United States, and if Shift Work Disorder and Jet Lag are included, then many millions more are impacted. The SRS Advocacy Taskforce has identified CRSWD as a class of sleep disorders for which additional high-quality research could have a significant impact to improve patient care. Participants were selected for their expertise and were assigned to one of three working groups: Phase Disorders, Entrainment Disorders, and Other. Each working group presented a summary of the current state of the science for their specific CRSWD area, followed by discussion from all participants. The outcome of those presentations and discussions are presented here.

Advances in the pharmacological management of non-24-h sleep-wake disorder

Introduction: Melatonin, a hormone that regulates circadian rhythms and the sleep-wake cycle, is produced mainly during the dark period in the pineal gland and is suppressed by light exposure. Patients with non-24-h sleep-wake disorder (non-24) fail to entrain the master clock with the 24-h light-dark cycle due to the lack of light perception to the suprachiasmatic nucleus typically in totally blind individuals or other organic disorders in sighted individuals, causing a progressive delay in the sleep-wake cycle and periodic insomnia and daytime sleepiness.Areas covered: Herein, the authors review the pharmacological therapies including exogenous melatonin and melatonin receptor agonists for the management of non-24. They introduce a historical report about the effects of melatonin on the phase shift and entrainment for blind individuals with the free-running circadian rhythm.Expert opinion: Orally administered melatonin entrains the endogenous circadian rhythm and improves nighttime sleep and daytime alertness for non-24. Currently, tasimelteon is the only approved medication for non-24 by the US Food and Drug Administration and the European Medicines Agency. Treatments that focus only on sleep problems are insufficient for the treatment of non-24, and aids to entrain the free-running rhythm with the light-dark cycle are needed.

Sleep of Wheelchair Rugby Athletes: Training, Rest and Competition

The aim of this study was to evaluate the sleep-wake cycle of wheelchair rugby athletes during the pre-season compared to in-season. Wheelchair Rugby athletes wore an actigraph monitor during two respective 10-day periods: 1) pre-season and 2) in-season, each of which comprised three training days, three rest days, and four competition days, respectively. In addition, the players completed questionnaires regarding sleepiness, subjective quality of sleep, and chronotype, as well as the use of the sleep diary along with the actigraph measurements (20 days). The wheelchair rugby athletes had poor subjective sleep quality in both stages observed by sleep efficiency below 85% (ES 0.31) and high score in the Pittsburgh questionnaire (effect size-ES 0.55), the actigraphy results presented an increase of sleep latency (ES 0.47), and wake after sleep onset (ES 0.42). When comparing the athlete’s routine, the competition days, demonstrated a reduction in the total time of sleep and the sleep efficiency, in addition to an increase in wakefulness after sleep onset when compared with the training and rest periods. As a result, the wheelchair rugby players did not describe a pattern of sleep-wake cycle during different training phases, as well as poor sleep quality.

Applications in sleep: How light affects sleep

Sleep is an active physiological state that plays a critical role in our physical and mental health and well-being. It is generated by a complex interplay between two oscillators, namely, the circadian oscillator and the sleep-wake homeostat. Sleep propensity is a function of wakefulness, that is, the longer one is awake the greater the homeostatic sleep pressure. Sleep onset occurs as a wake promoting circadian signal subsides, coinciding with an evening rise in melatonin and drop in core temperature. Light is one of the strongest time signals for the circadian oscillator. Poor sleep is a prevalent complaint today, attributable, in part, to our easy access to artificial light, especially after dusk. This non-visual effect of light is mediated by a multi-component photoreceptive system, consisting of rods, cones and melanopsin-expressing intrinsically-photosensitive retinal ganglion cells (ipRGC). Perhaps, with this available biological knowledge we can engineer artificial light to minimize its disruptive effect on sleep. We will highlight this by discussing circadian photoreception and its effect on sleep, in the blind population.

Sleep-Wake Disturbances After Acquired Brain Injury in Children Surviving Critical Care

BACKGROUND

Sleep-wake disturbances are underevaluated among children with acquired brain injury surviving critical care. We aimed to quantify severity, phenotypes, and risk factors for sleep-wake disturbances.

METHODS

We performed a prospective cohort study of 78 children aged ≥3 years with acquired brain injury within three months of critical care hospitalization. Diagnoses included traumatic brain injury (n = 40), stroke (n = 11), infectious or inflammatory disease (n = 10), hypoxic-ischemic injury (n = 9), and other (n = 8). Sleep Disturbances Scale for Children standardized T scores measured sleep-wake disturbances. Overall sleep-wake disturbances were dichotomized as any total or subscale T score ≥60. Any T score ≥70 defined severe sleep-wake disturbances. Subscale T scores ≥60 identified sleep-wake disturbance phenotypes.

RESULTS

Sleep-wake disturbances were identified in 44 (56%) children and were classified as severe in 36 (46%). Sleep-wake disturbances affected ≥33% of patients within each diagnosis and were not associated with severity of illness measures. The most common phenotype was disturbance in initiation and maintenance of sleep (47%), although 68% had multiple concurrent sleep-wake disturbance phenotypes. One third of all patients had preadmission chronic conditions, and this increased risk for sleep-wake disturbances overall (43% vs 21%, P = 0.04) and in the traumatic brain injury subgroup (52% vs 5%, P = 0.001).

CONCLUSIONS

Over half of children surviving critical care with acquired brain injury have sleep-wake disturbances. Most of these children have severe sleep-wake disturbances independent of severity of illness measures. Many sleep-wake disturbances phenotypes were identified, but most children had disturbance in initiation and maintenance of sleep. Our study underscores the importance of evaluating sleep-wake disturbances after acquired brain injury.

Perspectives in affective disorders: Clocks and sleep

Mood disorders are often characterised by alterations in circadian rhythms, sleep disturbances and seasonal exacerbation. Conversely, chronobiological treatments utilise zeitgebers for circadian rhythms such as light to improve mood and stabilise sleep, and manipulations of sleep timing and duration as rapid antidepressant modalities. Although sleep deprivation ("wake therapy") can act within hours, and its mood-elevating effects be maintained by regular morning light administration/medication/earlier sleep, it has not entered the regular guidelines for treating affective disorders as a first-line treatment. The hindrances to using chronotherapeutics may lie in their lack of patentability, few sponsors to carry out large multi-centre trials, non-reimbursement by medical insurance and their perceived difficulty or exotic "alternative" nature. Future use can be promoted by new technology (single-sample phase measurements, phone apps, movement and sleep trackers) that provides ambulatory documentation over long periods and feedback to therapist and patient. Light combinations with cognitive behavioural therapy and sleep hygiene practice may speed up and also maintain response. The urgent need for new antidepressants should hopefully lead to reconsideration and implementation of these non-pharmacological methods, as well as further clinical trials. We review the putative neurochemical mechanisms underlying the antidepressant effect of sleep deprivation and light therapy, and current knowledge linking clocks and sleep with affective disorders: neurotransmitter switching, stress and cortico-limbic reactivity, clock genes, cortical neuroplasticity, connectomics and neuroinflammation. Despite the complexity of multi-system mechanisms, more insight will lead to fine tuning and better application of circadian and sleep-related treatments of depression.

Melatonin as a Hormone: New Physiological and Clinical Insights

Melatonin is a ubiquitous molecule present in almost every live being from bacteria to humans. In vertebrates, besides being produced in peripheral tissues and acting as an autocrine and paracrine signal, melatonin is centrally synthetized by a neuroendocrine organ, the pineal gland. Independently of the considered species, pineal hormone melatonin is always produced during the night and its production and secretory episode duration are directly dependent on the length of the night. As its production is tightly linked to the light/dark cycle, melatonin main hormonal systemic integrative action is to coordinate behavioral and physiological adaptations to the environmental geophysical day and season. The circadian signal is dependent on its daily production regularity, on the contrast between day and night concentrations, and on specially developed ways of action. During its daily secretory episode, melatonin coordinates the night adaptive physiology through immediate effects and primes the day adaptive responses through prospective effects that will only appear at daytime, when melatonin is absent. Similarly, the annual history of the daily melatonin secretory episode duration primes the central nervous/endocrine system to the seasons to come. Remarkably, maternal melatonin programs the fetuses' behavior and physiology to cope with the environmental light/dark cycle and season after birth. These unique ways of action turn melatonin into a biological time-domain-acting molecule. The present review focuses on the above considerations, proposes a putative classification of clinical melatonin dysfunctions, and discusses general guidelines to the therapeutic use of melatonin.

Sleep and circadian rhythm function and trait impulsivity: An actigraphy study

We report the relationship between daily rest-activity patterns and trait impulsivity in healthy young adults. The Barratt Impulsiveness Scale was used to identify high and low impulsive individuals among a group of 51 volunteers. Participants' sleep behaviour and circadian rhythm function was assessed using week-long actigraphy. High impulsive individuals displayed phase-delayed patterns of sleep, a decreased total sleep time and sleep efficiency, and disrupted circadian function. Such outcomes were also associated with greater self-reported attention deficit hyperactivity disorder symptoms. The results highlight that sleep and circadian rhythm disturbances may be associated with impulsive traits replicating relationships described in psychiatric illnesses in which impulsivity is a core feature.

A Case of Non-24-Hour Sleep-Wake Rhythm Disorder Treated With a Low Dose of Ramelteon and Behavioral Education

ABSTRACT

Non-24-hour sleep-wake rhythm disorder (N24SWD) occurs when the intrinsic circadian pacemaker does not entrain (synchronize) to the 24-hour light/dark cycle. There is currently no established treatment for sighted patients with N24SWD. To the best of our knowledge, there have been very few reports on the efficacy of ramelteon administered to sighted patients with N24SWD. We report the case of a sighted patient with N24SWD whose free-running sleep-wake pattern recorded by actigraphy was stopped after the administration of a low dose of ramelteon combined with behavioral education.

Idiopathic Hypersomnia Patients Revealed Longer Circadian Period Length in Peripheral Skin Fibroblasts

The vast majority of living organisms have evolved a circadian rhythm of roughly 24 h in adaptation to ever-changing environmental conditions, such as the cycle of light and darkness. In some sleep disorders like idiopathic hypersomnia (IH) this adaptation is defective. As the etiology of this disease is largely unknown, we examined the in vitro circadian period length of patients suffering from IH. The patients were diagnosed according to the ICSD3-criteria by clinical history, polysomnography (PSG), and multiple sleep latency testing (MSLT). In order to gain insight into the molecular mechanism of this sleep disorder we collected fibroblasts from skin biopsies of IH patients and healthy subjects. We determined the circadian period length of the primary fibroblast cells by lentiviral infection with a construct expressing a luciferase gene under the control of a BMAL1 promoter. The group of IH patients revealed on average a prolonged circadian period length. In comparison to the group of healthy controls (HC) the mean period length was estimated to be 0.82 h (95%-CI 0.44–1.20 h) longer in the patient group. This finding further stresses a disturbed regulation of the circadian rhythm in IH patients as part of the pathophysiology of this complex and poorly understood primary sleep disorder.

Sleep in Children with Congenital Malformations of the Central Nervous System

PURPOSE OF REVIEW

Congenital malformations of the central nervous system may be seen in isolation or in association with syndromes that have multiorgan involvement. Among the potential health challenges these children may face, sleep concerns are frequent and may include chronic insomnia, sleep-related breathing disorders, and circadian rhythm disorders.

RECENT FINDINGS

In this review, we describe recent research into sleep disorders affecting children with congenital malformations of the CNS including visual impairment, septo-optic dysplasia, agenesis of the corpus callosum, Aicardi syndrome, Chiari malformation, spina bifida, achondroplasia, Joubert syndrome, fetal alcohol spectrum disorders, and congenital Zika syndrome. In many cases, the sleep disturbance can be directly related to observed anatomical differences in the brain (such as in apnea due to Chiari malformation), but in most syndromes, a complete understanding of the underlying pathophysiology connecting the malformation with sleep problem is still being elucidated. Our review provides a synthesis of available evidence for clinicians who treat this patient population, in whom appropriate diagnosis and management of sleep problems may improve the quality of life for both patient and caregiver.

Validity and Reliability of the Major Depression Inventory for Persons With Dual Sensory Loss

Background and Objectives

Research has shown that dual sensory loss is a risk factor for depression in older adults. However, validated measures of depression for people with dual sensory loss are lacking. The purpose of the present study was to investigate the construct validity and reliability of the Major Depression Inventory for use among elderly persons with acquired dual sensory loss.

Research Design and Methods

A cross-sectional questionnaire survey was conducted in a national sample of people ≥50 years of age with functional acquired dual sensory loss. Of the invited participants, 302 (66%) returned the questionnaire and 207 complete cases were included for analysis. Rasch models and graphical log-linear Rasch models were used for item analysis. Lack of differential item functioning was tested relative to severity of vision and hearing impairment, mode of questionnaire completion, age, sex, comorbidity, instrumental activities of daily living, social position, and cohabitation status.

Results

The 10-item Major Depression Inventory did not fit the Rasch model. An 8-item version, excluding the items “feeling sad” and “sleep problems,” fit a graphical log-linear Rasch model. No evidence of differential item functioning was discovered, thus the 8-item Major Depression Inventory was measurement invariant across severity of impairments and mode of completing the questionnaire. The overall reliability was 0.81 and ranged from acceptable to good for all subgroups of participants, except males with severe hearing impairment and low functional status. Consequently, the 8-item version of the Major Depression Inventory was considered construct valid and reliable within the frame of reference.

Discussion and Implications

An 8-item version of the Major Depression Inventory can be used to screen for depressive symptoms in elderly persons with acquired dual sensory loss.

The Circadian Clock and Human Health

Epidemiological studies provided the first evidence suggesting a connection between the circadian clock and human health. Mutant mice convincingly demonstrate the principle that dysregulation of the circadian system leads to a multitude of pathologies. Chrono-medicine is one of the most important upcoming themes in the field of circadian biology. Although treatments counteracting circadian dysregulation are already being applied (e.g., prescribing strong and regular zeitgebers), we need to comprehend entrainment throughout the body's entire circadian network before understanding the mechanisms that tie circadian dysregulation to pathology. Here, we attempt to provide a systematic approach to understanding the connection between the circadian clock and health. This taxonomy of (mis)alignments on one hand exposes how little we know about entrainment within any organism and which 'eigen-zeitgeber' signals are used for entrainment by the different cells and tissues. On the other hand, it provides focus for experimental approaches and tools that will logically map out how circadian systems contribute to disease as well as how we can treat and prevent them.

Non-24-Hour Sleep-Wake Rhythm Disorder in the Totally Blind: Diagnosis and Management

Several aspects of human physiology and behavior are dominated by 24-h circadian rhythms with key impacts on health and well-being. These include mainly the sleep–wake cycle, vigilance and performance patterns, and some hormone secretions. The rhythms are generated spontaneously by an internal “pacemaker,” the suprachiasmatic nuclei within the anterior hypothalamus. This master clock has, for most humans, an intrinsic rhythm slightly longer than 24 h. Daily retinal light exposure is necessary for the synchronization of the circadian rhythms with the external 24-h solar environment. This daily synchronization process generally poses no problems for sighted individuals except in the context of jetlag or working night shifts being conditions of circadian desynchrony. However, many blind subjects with no light perception had periodical circadian desynchrony, in the absence of light information to the master clock leading to poor circadian rhythm synchronization. Affected patients experience cyclical or periodic episodes of poor sleep and daytime dysfunction, severely interfering with social, academic, and professional life. The diagnosis of Non-24 Sleep–Wake Rhythm Disorder, also named free-running disorder, non-entrained disorder, or hypernycthemeral syndrome, remains challenging from a clinical point of view due to the cyclical symptoms and should be confirmed by measurements of circadian biomarkers such as urinary melatonin to demonstrate a circadian period outside the normal range. Management includes behavioral modification and melatonin. Tasimelteon, a novel melatonin receptor 1 and 2 agonist, has demonstrated its effectiveness and safety with an evening dose of 20 mg and is currently the only treatment approved by the FDA and the European Medicines Agency.

Preserved sleep microstructure in blind individuals

The loss of vision, particularly when it occurs early in life, is associated with compensatory cortical plasticity not only in the visual cortical areas, but throughout the entire brain. The absence of visual input to the retina can also induce changes in entrainment of the circadian rhythm, as light is the primary zeitgeber of the master biological clock found in the suprachiasmatic nucleus of the hypothalamus. In addition, a greater number of sleep disturbances is often reported in blind individuals. Here, we examined various electroencephalographic microstructural components of sleep, both during rapid-eye-movement (REM) sleep and non-REM (NREM) sleep, between blind individuals, including both of early and late onset, and normal-sighted controls. During wakefulness, occipital alpha oscillations were lower, or absent in blind individuals. During sleep, differences were observed across electrode derivations between the early and late blind samples, which may reflect altered cortical networking in early blindness. Despite these differences in power spectra density, the electroencephalography microstructure of sleep, including sleep spindles, slow wave activity, and sawtooth waves, remained present in the absence of vision.

Sleep structure in blindness is influenced by circadian desynchrony

We examined the structure, duration and quality of sleep, including non-rapid eye movement sleep and rapid eye movement sleep, in 11 blind individuals without conscious light perception and 11 age- and sex-matched sighted controls. Because blindness is associated with a greater incidence of free-running circadian rhythms, we controlled for circadian phase by a measure of melatonin onset timing. When circadian rhythm was entrained and melatonin onset occurred at normal times, sleep structure did not differ between blind and sighted individuals. On the other hand, an abnormal timing of the circadian phase, including delayed, shifted and unclassifiable melatonin onsets, led to larger rapid eye movement sleep latencies and increased wake times. No differences were observed for stages of non-rapid eye movement sleep, either between congenital and late blind and sighted individuals, or across the different circadian phases. Moreover, abnormal circadian phases were more common in the blind (n = 5) than the sighted (n = 2) sample. Our findings suggest that the sleep structure of blind individuals depends on entrainment of circadian phase, rather than on the absence of vision.

The effects of self-selected light-dark cycles and social constraints on human sleep and circadian timing: a modeling approach

Why do we go to sleep late and struggle to wake up on time? Historically, light-dark cycles were dictated by the solar day, but now humans can extend light exposure by switching on artificial lights. We use a mathematical model incorporating effects of light, circadian rhythmicity and sleep homeostasis to provide a quantitative theoretical framework to understand effects of modern patterns of light consumption on the human circadian system. The model shows that without artificial light humans wakeup at dawn. Artificial light delays circadian rhythmicity and preferred sleep timing and compromises synchronisation to the solar day when wake-times are not enforced. When wake-times are enforced by social constraints, such as work or school, artificial light induces a mismatch between sleep timing and circadian rhythmicity ('social jet-lag'). The model implies that developmental changes in sleep homeostasis and circadian amplitude make adolescents particularly sensitive to effects of light consumption. The model predicts that ameliorating social jet-lag is more effectively achieved by reducing evening light consumption than by delaying social constraints, particularly in individuals with slow circadian clocks or when imposed wake-times occur after sunrise. These theory-informed predictions may aid design of interventions to prevent and treat circadian rhythm-sleep disorders and social jet-lag.

Circadian disruption: New clinical perspective of disease pathology and basis for chronotherapeutic intervention

Biological processes are organized in time as innate rhythms defined by the period (τ), phase (peak [Φ] and trough time), amplitude (A, peak-trough difference) and mean level. The human time structure in its entirety is comprised of ultradian (τ < 20 h), circadian (20 h > τ < 28 h) and infradian (τ > 28 h) bioperiodicities. The circadian time structure (CTS) of human beings, which is more complicated than in lower animals, is orchestrated and staged by a brain central multioscillator system that includes a prominent pacemaker - the suprachiasmatic nuclei of the hypothalamus. Additional pacemaker activities are provided by the pineal hormone melatonin, which circulates during the nighttime, and the left and right cerebral cortices. Under ordinary circumstances this system coordinates the τ and Φ of rhythms driven by subservient peripheral cell, tissue and organ clock networks. Cyclic environmental, feeding and social time cues synchronize the endogenous 24 h clocks and rhythms. Accordingly, processes and functions of the internal environment are integrated in time for maximum biological efficiency, and they are also organized and synchronized in time to the external environment to ensure optimal performance and response to challenge. Artificial light at night (ALAN) exposure can alter the CTS as can night work, which, like rapid transmeridian displacement by air travel, necessitates realignment of the Φ of the multitude of 24 h rhythms. In 2001, Stevens and Rea coined the phrase "circadian disruption" (CD) to label the CTS misalignment induced by ALAN and shift work (SW) as a potential pathologic mechanism of the increased risk for cancer and other medical conditions. Current concerns relating to the effects of ALAN exposure on the CTS motivated us to renew our long-standing interest in the possible role of CD in the etiopathology of common human diseases and patient care. A surprisingly large number of medical conditions involve CD: adrenal insufficiency; nocturia; sleep-time non-dipping and rising blood pressure 24 h patterns (nocturnal hypertension); delayed sleep phase syndrome, non-24 h sleep/wake disorder; recurrent hypersomnia; SW intolerance; delirium; peptic ulcer disease; kidney failure; depression; mania; bipolar disorder; Parkinson's disease; Smith-Magenis syndrome; fatal familial insomnia syndrome; autism spectrum disorder; asthma; byssinosis; cancers; hand, foot and mouth disease; post-operative state; and ICU outcome. Poorly conceived medical interventions, for example nighttime dosing of synthetic corticosteroids and certain β-antagonists and cyclic nocturnal enteral or parenteral nutrition, plus lifestyle habits, including atypical eating times and chronic alcohol consumption, also can be causal of CD. Just as surprisingly are the many proven chronotherapeutic strategies available today to manage the CD of several of these medical conditions. In clinical medicine, CD seems to be a common, yet mostly unrecognized, pathologic mechanism of human disease as are the many effective chronotherapeutic interventions to remedy it.

Tasimelteon: A Review in Non-24-Hour Sleep-Wake Disorder in Totally Blind Individuals

Tasimelteon (Hetlioz(®)) is a dual melatonin receptor agonist indicated for the treatment of Non-24-Hour Sleep-Wake Disorder (Non-24) (free-running disorder). In two randomized, double-masked, multicentre, phase III trials, totally blind individuals with Non-24 who received oral tasimelteon 20 mg once nightly were significantly more likely than those receiving placebo to entrain the circadian pacemaker (the SET trial) and maintain entrainment (the RESET trial). Sleep/wake parameters and functioning were also improved with tasimelteon. Oral tasimelteon was generally well tolerated in totally blind patients with Non-24. In conclusion, tasimelteon is a useful drug for the treatment of Non-24 in totally blind individuals.

Non-24-hour sleep-wake syndrome improved by low-dose valproic acid: a case report

A woman was diagnosed with non-24-hour sleep-wake syndrome and depressive symptoms. Her depressive symptoms did not respond to standard doses of several antidepressants or mood stabilizers. Furthermore, her sleep-wake cycle remained non-entrained despite treatment with a melatonin-related drug, vitamin B12, and phototherapy. Ultimately, her sleep-wake rhythm was restored to a 24-hour pattern with a low dose of valproic acid, and her depressive symptoms tended to improve as a result of synchronization without antidepressants. Low-dose valproic acid appears to be one of the effective means of entraining circadian rhythms in patients with non-24-hour sleep-wake syndrome, which in turn likely improves associated depressive symptoms.