Altered phase relation between sleep timing and core body temperature rhythm in delayed sleep phase syndrome and non-24-hour sleep-wake syndrome in humans

Images: "Too much heat for my non-24-hour sleep-wake disorder!" A case report

The non-24-hour sleep-wake disorder (N24SWD) is a rare condition, sometimes associated with blindness or with suprachiasmatic nuclei lesions, resulting in a free-running rhythm or hypernycthemeral syndrome. Synchronizers, such as light, when light perception remains, melatonin, food intakes, physical activity, social interactions, and temperature, play a key role in the treatment of N24SWD. In this report, we describe a case illustrating the impact of outdoor temperature in a 34-year-old man with N24SWD effectively treated through a combination of chronotherapy interventions. During 3 consecutive heat waves, he experienced a recurrence of his natural 25.5-hour free-running rhythm, with a consistent bedtime phase delay caused by temperature, resulting in the discontinuation of chronotherapy. After these heat waves, he was able again to resynchronize his rhythms with the combination of chronotherapeutics. This case report highlights that patients with N24SWD may be particularly at risk of relapse during heat waves, with direct implications for monitoring and reinforcing chronotherapies.

CITATION

Garrivet J, d'Ortho M-P, Frija-Masson J, et al. "Too much heat for my non-24-hour sleep-wake disorder!" A case report. J Clin Sleep Med. 2024;20(2):329-333.

Non-Excitatory Amino Acids, Melatonin, and Free Radicals: Examining the Role in Stroke and Aging

The aim of this review is to explore the relationship between melatonin, free radicals, and non-excitatory amino acids, and their role in stroke and aging. Melatonin has garnered significant attention in recent years due to its diverse physiological functions and potential therapeutic benefits by reducing oxidative stress, inflammation, and apoptosis. Melatonin has been found to mitigate ischemic brain damage caused by stroke. By scavenging free radicals and reducing oxidative damage, melatonin may help slow down the aging process and protect against age-related cognitive decline. Additionally, non-excitatory amino acids have been shown to possess neuroprotective properties, including antioxidant and anti-inflammatory in stroke and aging-related conditions. They can attenuate oxidative stress, modulate calcium homeostasis, and inhibit apoptosis, thereby safeguarding neurons against damage induced by stroke and aging processes. The intracellular accumulation of certain non-excitatory amino acids could promote harmful effects during hypoxia-ischemia episodes and thus, the blockade of the amino acid transporters involved in the process could be an alternative therapeutic strategy to reduce ischemic damage. On the other hand, the accumulation of free radicals, specifically mitochondrial reactive oxygen and nitrogen species, accelerates cellular senescence and contributes to age-related decline. Recent research suggests a complex interplay between melatonin, free radicals, and non-excitatory amino acids in stroke and aging. The neuroprotective actions of melatonin and non-excitatory amino acids converge on multiple pathways, including the regulation of calcium homeostasis, modulation of apoptosis, and reduction of inflammation. These mechanisms collectively contribute to the preservation of neuronal integrity and functions, making them promising targets for therapeutic interventions in stroke and age-related disorders.

Updates and confounding factors in delayed sleep-wake phase disorder

Delayed sleep-wake phase disorder (DSWPD) is a circadian rhythm sleep disorder characterised by a delay in the main sleep period, with patients experiencing difficulty getting to sleep and waking up at socially appropriate times. This often causes insomnia and compromised sleep, results in impairment to daytime function and is associated with a range of comorbidities. Besides interventions aimed at ameliorating symptoms, there is good evidence supporting successful phase advancement with bright light therapy or melatonin administration. However, no treatment to date addresses the tendency to phase delay, which is a common factor amongst the various contributing causes of DSWPD. Circadian phase markers such as core body temperature and circulating melatonin typically correlate well with sleep timing in healthy patients, but numerous variations exist in DSWPD patients that can make these unpredictable for use in diagnostics. There is also increasing evidence that, on top of problems with the circadian cycle, sleep homeostatic processes actually differ in DSWPD patients compared to controls. This naturally has ramifications for management but also for the current approach to the pathogenesis itself in which DSWPD is considered a purely circadian disorder. This review collates what is known on the causes and treatments of DSWPD, addresses the pitfalls in diagnosis and discusses the implications of current data on modified sleep homeostasis, making clinical recommendations and directing future research.

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.

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.

The efficacy of add-on ramelteon and subsequent dose reduction in benzodiazepine derivatives/Z-drugs for the treatment of sleep-related eating disorder and night eating syndrome: a retrospective analysis of consecutive patients

STUDY OBJECTIVES

The objective of this study was to determine the efficacy of ramelteon in treating abnormal eating behavior in patients with sleep-related eating disorder and/or night eating syndrome.

METHODS

We retrospectively reviewed the medical records of patients with sleep-related eating disorder/night eating syndrome at the Yoyogi Sleep Disorder Center from November 2013 to November 2018. We categorized patients as ramelteon treatment responders when the frequency of nighttime eating per week decreased to less than half of that before treatment.

RESULTS

Forty-nine patients were included in the analysis. The mean frequency of eating behavior (per week) (standard deviation) at baseline and post-ramelteon treatment was significantly different, at 5.3 (2.2) and 3.2 (3.0), respectively (P < .001). Twenty-one patients (42.9%) were classified as responders. Adverse events, all of which were mild daytime somnolence, were observed in 5 patients. There were significantly more individuals using benzodiazepine derivatives and Z-drugs before treatment and those with coexisting delayed sleep-wake phase disorder in the responder group than in the nonresponder group (P < .001 and P < .05, respectively). The mean benzodiazepine derivatives and Z-drugs dose significantly decreased from baseline to post-ramelteon treatment within the responder group (P < .05). This trend was not observed in the nonresponder group. Meanwhile, the sleep midpoint of patients with sleep-related eating disorder/night eating syndrome and delayed sleep-wake phase disorder did not significantly change after treatment.

CONCLUSIONS

Our results indicate that ramelteon is a candidate treatment for sleep-related eating disorder/night eating syndrome. The effects of ramelteon might have occurred primarily through the reduction in benzodiazepine derivatives and Z-drugs rather than through the improvement in sleep-wake rhythm dysregulation.

Circadian tau differences and rhythm associations in delayed sleep-wake phase disorder and sighted non-24-hour sleep-wake rhythm disorder

STUDY OBJECTIVES

We investigated biological and behavioral rhythm period lengths (i.e. taus) of delayed sleep-wake phase disorder (DSWPD) and non-24-hour sleep-wake rhythm disorder (N24SWD). Based on circadian phase timing (temperature and dim light melatonin onset), DSWPD participants were dichotomized into a circadian-delayed and a circadian non-delayed group to investigate etiological differences.

METHODS

Participants with DSWPD (n = 26, 17 m, age: 21.85 ± 4.97 years), full-sighted N24SWD (n = 4, 3 m, age: 25.75 ± 4.99 years) and 18 controls (10 m, age: 23.72 ± 5.10 years) participated in an 80-h modified constant routine. An ultradian protocol of 1-h "days" in dim light, controlled conditions alternated 20-min sleep/dark periods with 40-min enforced wakefulness/light. Subjective sleepiness ratings were recorded prior to every sleep/dark opportunity and median reaction time (vigilance) was measured hourly. Obtained sleep (sleep propensity) was derived from 20-min sleep/dark opportunities to quantify hourly objective sleepiness. Hourly core body temperature was recorded, and salivary melatonin assayed to measure endogenous circadian rhythms. Rhythm data were curved using the two-component cosine model.

RESULTS

Patients with DSWPD and N24SWD had significantly longer melatonin and temperature taus compared to controls. Circadian non-delayed DSWPD had normally timed temperature and melatonin rhythms but were typically sleeping at relatively late circadian phases compared to those with circadian-delayed DSWPD.

CONCLUSIONS

People with DSWPD and N24SWD exhibit significantly longer biological circadian rhythm period lengths compared to controls. Approximately half of those diagnosed with DSWPD do not have abnormally delayed circadian rhythm timings suggesting abnormal phase relationship between biological rhythms and behavioral sleep period or potentially conditioned sleep-onset insomnia.

Effect of a hand massage with a warm hand bath on sleep and relaxation in elderly women with disturbance of sleep: A crossover trial

Aim

The purpose of the present study was to clarify the effects of a hand massage with a warm hand bath on sleep, autonomic nervous activity, subjective sleep quality, and relaxation in elderly women with sleep disturbance.

Methods

A crossover design was used. Participants were assigned to two groups: a structured control first and intervention second condition, or an intervention first and control second condition. The sleep index as assessed by actigraphy, autonomic nervous activity, subjective sleep quality, and relaxation was then recorded.

Results

The mean age of the participants was 77.8 ± 6.8 years (n = 28). According to the actigraph, the intervention day showed significantly improved sleep efficiency (p = .048) and sleep onset latency (p = .015). Regarding autonomic nervous activity, heart rate decreased significantly after the intervention (p = .001), but no significant differences were seen in the other indexes. Subjective sleep quality, which was investigated using the middle‐age and aged version of the Oguri–Shirakawa–Azumi sleep questionnaire, was significantly higher after the intervention for four out of five factors. Subjective comfort and relaxation were significantly higher after the intervention for all items.

Conclusions

A hand massage with a warm hand bath in the evening improved sleep efficiency and sleep onset latency in elderly women with sleep disturbance. These results suggest that a hand bath and massage may improve subjective sleep quality and relaxation.

Non-24-hour Sleep-Wake Rhythm Disorder

Non-24-hour sleep-wake rhythm disorder is a circadian rhythm sleep-wake disorder characterized by an inability to entrain to the 24-hour environment. Patients present with complaints of insomnia or hypersomnia, with progressive daily shifts of sleep-wake activity on actigraphy or sleep logs. Although first recognized in blind individuals without light perception, it also can be seen in individuals with intact vision. Treatment focuses on timed melatonin in blind individuals, whereas it is more complex in sighted individuals, using multiple time cues, such as light, melatonin, social interactions, feeding, and activity.

Habitual light exposure relative to circadian timing in delayed sleep-wake phase disorder

Study Objectives

To compare melatonin timing, a well-validated marker for endogenous circadian phase, and habitual light-exposure patterns in adults with delayed sleep-wake phase disorder (DSWPD) and intermediate chronotype controls.

Methods

Twelve individuals with DSWPD (five females, mean age: 31.1) and 12 age-matched controls (six females, mean age: 33.6) underwent a minimum of 7 days of light and activity monitoring followed by an inpatient hospital stay, where blood was taken to assess melatonin timing (calculated as dim light melatonin onset-DLMO). Habitual light-exposure patterns were then compared with a human phase-response curve (PRC) to light.

Results

Relative to clock time, individuals with DSWPD had a later light-exposure pattern compared with controls, but their light-exposure pattern was earlier relative to DLMO. According to the human PRC to light, individuals with DSWPD had less daily advancing light exposure compared with controls. The primary difference was seen in the late portion of the advancing window, in which individuals with DSWPD were exposed to fewer pulses of light of equivalent duration and intensity compared with controls.

Conclusions

Diminished advancing light exposure may play a role in the development and perpetuation of delayed sleep-wake timing in individuals with DSWPD. Enhancing light exposure during the later portion of the advancing window represents an innovative and complementary strategy that has the potential to improve the effectiveness of bright light therapy in DSWPD.

Circadian Rhythm Disturbances in the Blind

PURPOSE OF REVIEW

Sleep timing, quantity, and quality are controlled by homeostatic and circadian systems. Circadian clock systems are present in all cells and organs and their timing is determined by a transcriptional-translational feedback loop of circadian genes. Individual cellular clocks are synchronized by the central body clock, situated in the suprachiasmatic nucleus, which communicates with them through humoral and neural signals including melatonin. The circadian system controls both the circadian period: (i.e., the length of the intrinsic clock), but also the circadian phase (i.e., the clock timing). An important determinant of the circadian system is light exposure. In most humans, the circadian period is slightly longer than 24 h and without regular resetting it tends to drift, leading to progressively later bedtimes and wake times and a tendency to cycle though periods of normal and abnormal sleep. Blind patients are thus at an increased risk of abnormal circadian function. The purpose of this article is to review recent research and clinical management of circadian rhythm disorders in blind patients.

RECENT FINDINGS

Blind patients can present delayed and advanced sleep phase disorders but the most common abnormality in totally blind patients without light perception is non-24-hour sleep-wake disorder (N24SWD). This is rare in the general population but may affect up to 50% of blind patients without light perception. The diagnosis of a circadian rhythm disorder in the blind is complex. New screening tools have been developed but actigraphy and repeated melatonin profiles over 24 h remain essential. Circadian disorders in the blind are frequent, especially in the patients without light perception. They require accurate diagnosis in order to target treatment. Determining the precise nature of a sleep disorder in blind patients with a suspected circadian rhythm abnormality is complex and requires a detailed clinical history with sleep diaries and the use of actigraphy and melatonin profiles.

Diagnostic and Treatment Challenges of Sighted Non-24-Hour Sleep-Wake Disorder

STUDY OBJECTIVES

To report the diagnostic and treatment challenges of sighted non-24-hour sleep-wake disorder (N24SWD).

METHODS

We report a series of seven sighted patients with N24SWD clinically evaluated by history and sleep diaries, and when available wrist actigraphy and salivary melatonin levels, and treated with timed melatonin and bright light therapy.

RESULTS

Most patients had a history of a delayed sleep-wake pattern prior to developing N24SWD. The typical sleep-wake pattern of N24SWD was seen in the sleep diaries (and in actigraphy when available) in all patients with a daily delay in midpoint of sleep ranging 0.8 to 1.8 hours. Salivary dim light melatonin onset (DLMO) was evaluated in four patients but was missed in one. The estimated phase angle from DLMO to sleep onset ranged from 5.25 to 9 hours. All six patients who attempted timed melatonin and bright light therapy were able to entrain their sleep-wake schedules. Entrainment occurred at a late circadian phase, possibly related to the late timing of melatonin administration, though the patients often preferred late sleep times. Most did not continue treatment and continued to have a non-24-hour sleep-wake pattern.

CONCLUSIONS

N24SWD is a chronic debilitating disorder that is often overlooked in sighted people and can be challenging to diagnose and treat. Tools to assess circadian pattern and timing can be effectively applied to aid the diagnosis. The progressive delay of the circadian rhythm poses a challenge for determining the most effective timing for melatonin and bright light therapies. Furthermore, once the circadian sleep-wake rhythm is entrained, long-term effectiveness is limited because of the behavioral and environmental structure that is required to maintain stable entrainment.

Sleep-wake profiles and circadian rhythms of core temperature and melatonin in young people with affective disorders

While disturbances of the sleep-wake cycle are common in people with affective disorders, the characteristics of these disturbances differ greatly between individuals. This heterogeneity is likely to reflect multiple underlying pathophysiologies, with different perturbations in circadian systems contributing to the variation in sleep-wake cycle disturbances. Such disturbances may be particularly relevant in adolescents and young adults with affective disorders as circadian rhythms undergo considerable change during this key developmental period. This study aimed to identify profiles of sleep-wake disturbance in young people with affective disorders and investigate associations with biological circadian rhythms. Fifty young people with affective disorders and 19 control participants (aged 16-31 years) underwent actigraphy monitoring for approximately two weeks to derive sleep-wake cycle parameters, and completed an in-laboratory assessment including evening dim-light saliva collection for melatonin assay and overnight continuous core body temperature measurement. Cluster analysis based on sleep-wake cycle parameters identified three distinct patient groups, characterised by 'delayed sleep-wake', 'disrupted sleep', and 'long sleep' respectively. The 'delayed sleep-wake' group had both delayed melatonin onset and core temperature nadir; whereas the other two cluster groups did not differ from controls on these circadian markers. The three groups did not differ on clinical characteristics. These results provide evidence that only some types of sleep-wake disturbance in young people with affective disorders are associated with fundamental circadian perturbations. Consequently, interventions targeting endogenous circadian rhythms to promote a phase shift may be particularly relevant in youth with affective disorders presenting with delayed sleep-wake cycles.

Can the circadian phase be estimated from self-reported sleep timing in patients with Delayed Sleep Wake Phase Disorder to guide timing of chronobiologic treatment?

INTRODUCTION

The efficacy of bright light and/or melatonin treatment for Delayed Sleep Wake Phase Disorder (DSWPD) is contingent upon an accurate clinical assessment of the circadian phase. However, the process of determining this circadian phase can be costly and is not yet readily available in the clinical setting. The present study investigated whether more cost-effective and convenient estimates of the circadian phase, such as self-reported sleep timing, can be used to predict the circadian phase and guide the timing of light and/or melatonin treatment (i.e. dim-light melatonin onset, core body temperature minimum and melatonin secretion mid-point) in a sample of individuals with DSWPD.

METHOD

Twenty-four individuals (male = 17; mean age = 21.96, SD = 5.11) with DSWPD were selected on the basis of ICSD-3 criteria from a community-based sample. The first 24-hours of a longer 80-hour constant laboratory ultradian routine were used to determine core body temperature minimum (cBT^min), dim-light melatonin onset (DLMO) and the midpoint of the melatonin secretion period (DLM^mid = [DLM°^ff-DLMO]/2). Prior to the laboratory session subjective sleep timing was assessed using a 7-day sleep/wake diary, the Pittsburgh Sleep Quality Index (PSQI), and the Delayed Sleep Phase Disorder Sleep Timing Questionnaire (DSPD-STQ).

RESULTS

Significant moderate to strong positive correlations were observed between self-reported sleep timing variables and DLMO, cBT^min and DLM^mid. Regression equations revealed that the circadian phase (DLMO, cBT^min and DLM^mid) was estimated within ±1.5 hours of the measured circadian phase most accurately by the combination of sleep timing measures (88% of the sample) followed by sleep diary reported midsleep (83% of the sample) and sleep onset time (79% of the sample).

DISCUSSION

These findings suggest that self-reported sleep timing may be useful clinically to predict a therapeutically relevant circadian phase in DSWPD.

Diagnosis, Cause, and Treatment Approaches for Delayed Sleep-Wake Phase Disorder

Delayed sleep-wake phase disorder (DSWPD) is commonly defined as an inability to fall asleep and wake at societal times resulting in excessive daytime sleepiness. Although the cause is multifaceted, delays in sleep time are largely driven by misalignment between the circadian pacemaker and the desired sleep-wake timing schedule. Current treatment approaches focus on correcting the circadian delay; however, there is a lack of data investigating combined therapies for treatment of DSWPD.

Circadian Melatonin and Temperature Taus in Delayed Sleep-wake Phase Disorder and Non-24-hour Sleep-wake Rhythm Disorder Patients: An Ultradian Constant Routine Study

Our objectives were to investigate the period lengths (i.e., taus) of the endogenous core body temperature rhythm and melatonin rhythm in delayed sleep-wake phase disorder patients (DSWPD) and non-24-h sleep-wake rhythm disorder patients (N24SWD) compared with normally entrained individuals. Circadian rhythms were measured during an 80-h ultradian modified constant routine consisting of 80 ultrashort 1-h "days" in which participants had 20-min sleep opportunities alternating with 40 min of enforced wakefulness. We recruited a community-based sample of 26 DSWPD patients who met diagnostic criteria (17 males, 9 females; age, 21.85 ± 4.97 years) and 18 healthy controls (10 males, 8 females; age, 23.72 ± 5.10 years). Additionally, 4 full-sighted patients (3 males, 1 female; age, 25.75 ± 4.99 years) were diagnosed with N24SWD and included as a discrete study group. Ingestible core temperature capsules were used to record minute temperatures that were averaged to obtain 80 hourly data points. Salivary melatonin concentration was assessed every half-hour to determine time of dim light melatonin onset at the beginning and end of the 80-h protocol. DSWPD patients had significantly longer melatonin rhythm taus (24 h 34 min ± 17 min) than controls (24 h 22 min ± 15 min, p = 0.03, d = 0.70). These results were further supported by longer temperature rhythm taus in DSWPD patients (24 h 34 min ± 26 min) relative to controls (24 h 13 min ± 15 min, p = 0.01, d = 0.80). N24SWD patients had even longer melatonin (25 h ± 19 min) and temperature (24 h 52 min ± 17 min) taus than both DSWPD (p = 0.007, p = 0.06) and control participants (p < 0.001, p = 0.02, respectively). Between 12% and 19% of the variance in DSWPD patients' sleep timing could be explained by longer taus. This indicates that longer taus of circadian rhythms may contribute to the DSWPD patients' persistent tendency to delay, their frequent failure to respond to treatment, and their relapse following treatment. Additionally, other factors can contribute to misalignments in DSWPD and N24SWD disorders.

Clinical Practice Guideline for the Treatment of Intrinsic Circadian Rhythm Sleep-Wake Disorders: Advanced Sleep-Wake Phase Disorder (ASWPD), Delayed Sleep-Wake Phase Disorder (DSWPD), Non-24-Hour Sleep-Wake Rhythm Disorder (N24SWD), and Irregular Sleep-Wake Rhythm Disorder (ISWRD). An Update for 2015: An American Academy of Sleep Medicine Clinical Practice Guideline

A systematic literature review and meta-analyses (where appropriate) were performed and the GRADE approach was used to update the previous American Academy of Sleep Medicine Practice Parameters on the treatment of intrinsic circadian rhythm sleep-wake disorders. Available data allowed for positive endorsement (at a second-tier degree of confidence) of strategically timed melatonin (for the treatment of DSWPD, blind adults with N24SWD, and children/ adolescents with ISWRD and comorbid neurological disorders), and light therapy with or without accompanying behavioral interventions (adults with ASWPD, children/adolescents with DSWPD, and elderly with dementia). Recommendations against the use of melatonin and discrete sleep-promoting medications are provided for demented elderly patients, at a second- and first-tier degree of confidence, respectively. No recommendations were provided for remaining treatments/ populations, due to either insufficient or absent data. Areas where further research is needed are discussed.

Sleep disruption and the sequelae associated with traumatic brain injury

Sleep disruption, which includes a loss of sleep as well as poor quality fragmented sleep, frequently follows traumatic brain injury (TBI) impacting a large number of patients each year in the United States. Fragmented and/or disrupted sleep can worsen neuropsychiatric, behavioral, and physical symptoms of TBI. Additionally, sleep disruption impairs recovery and can lead to cognitive decline. The most common sleep disruption following TBI is insomnia, which is difficulty staying asleep. The consequences of disrupted sleep following injury range from deranged metabolomics and blood brain barrier compromise to altered neuroplasticity and degeneration. There are several theories for why sleep is necessary (e.g., glymphatic clearance and metabolic regulation) and these may help explain how sleep disruption contributes to degeneration within the brain. Experimental data indicate disrupted sleep allows hyperphosphorylated tau and amyloid β plaques to accumulate. As sleep disruption may act as a cellular stressor, target areas warranting further scientific investigation include the increase in endoplasmic reticulum and oxidative stress following acute periods of sleep deprivation. Potential treatment options for restoring the normal sleep cycle include melatonin derivatives and cognitive behavioral therapy.

Nocturnal Melatonin Profiles in Patients with Delayed Sleep-Wake Phase Disorder and Control Sleepers

A significant delay in the timing of endogenous circadian rhythms has been associated with delayed sleep phase disorder (DSPD). More recently, other mechanisms have also been proposed to account for this disorder. To further explore the etiology of DSPD, the present study compared nocturnal melatonin profiles of 26 DSPD patients (18 males, 8 females; age, 21.73 ± 4.98 years) and 17 normally timed good sleepers (10 males, 7 females; age, 23.82 ± 5.23 years) in a time-free, dim-light (<10 lux) laboratory environment. A 30-h modified constant routine with alternating 20-min sleep opportunities and 40 min of enforced wakefulness was used to measure the endogenous melatonin circadian rhythm. Salivary melatonin was sampled half-hourly from 1820 h to 0020 h and then hourly from 0120 h to 1620 h. DSPD patients had significantly later timed melatonin profiles that were delayed by approximately 3 h compared to normal sleepers, and there were no notable differences in the relative duration of secretion between groups. However, melatonin secretion between dim-light melatonin onset (DLMO) and acrophase was less prominent in DSPD patients compared to good sleepers, who showed a more acute initial surge of melatonin following the DLMO. Although the regulatory role of melatonin is unknown, abnormal melatonin profiles have been linked to psychiatric and neurological disorders (e.g., major depression, obsessive compulsive disorder, Parkinson disease). These results therefore suggest that in addition to a delayed endogenous circadian rhythm, a diminished initial surge of melatonin secretion following DLMO may contribute to the etiology of DSPD.

The etiology of delayed sleep phase disorder

According to classification manuals for sleep disorders, nine disorders are directly related to biological clock timing misalignments. Of all, delayed sleep phase disorder (DSPD) is the most commonly diagnosed, predominantly affecting adolescents, young adults, and insomnia patients. It is a persistent inability to fall asleep at earlier, more desirable and socially conventional times, coupled with extreme difficulty awakening in the morning. Considerable evidence shows a delay in the circadian clock to be associated with DSPD. Therefore, treatments have mainly focused on advancing the biological clock and sleep timing through pharmacotherapy, phototherapy and behavioral therapies. The clinical evidence indicates that these treatments are efficacious, at least in the short term. However, follow up studies show frequent patient relapse, leading researchers to speculate that alternative etiologies may be contributing to sleep and circadian clock delays in DSPD. The aim of the present paper is to review and collate current literature related to DSPD etiology in order to outline gaps in current knowledge and suggest future research.

Circadian misalignment and health

Circadian rhythms are near 24-h patterns of physiology and behaviour that are present independent of external cues including hormones, body temperature, mood, and sleep propensity. The term 'circadian misalignment' describes a variety of circumstances, such as inappropriately timed sleep and wake, misalignment of sleep/wake with feeding rhythms, or misaligned central and peripheral rhythms. The predominance of early research focused on misalignment of sleep to the biological night. However, discovery of clock genes and the presence of peripheral circadian oscillators have expanded the definitions of misalignment. Experimental studies conducted in animal models and humans have provided evidence of potential mechanisms that link misalignment to negative outcomes. These include dysregulation of feeding behaviours, changes in appetite stimulating hormones, glucose metabolism and mood. This review has two foci: (1) to describe how circadian misalignment has been defined and evaluated in laboratory and field experiments, and (2) to describe evidence linking different types of circadian misalignment to increased risk for physical (cardiovascular disease, diabetes, obesity, cancer) and psychiatric (depression, bipolar, schizophrenia, attention deficit) disorders. This review will describe the role of circadian misalignment as a risk factor for disease in the general population and in clinical populations, including circadian rhythm sleep disorders and psychiatric disorders.

Circadian rhythm sleep disorders

There have been remarkable advances in our understanding of the molecular, cellular, and physiologic mechanisms underlying the regulation of circadian rhythms, and of the impact of circadian dysfunction on health and disease. This information has transformed our understanding of the effect of circadian rhythm sleep disorders (CRSD) on health, performance, and safety. CRSDs are caused by alterations of the central circadian timekeeping system, or a misalignment of the endogenous circadian rhythm and the external environment. This article reviews circadian biology and discusses the pathophysiology, clinical features, diagnosis, and treatment of the most commonly encountered CRSDs in clinical practice.

The spectral composition of evening light and individual differences in the suppression of melatonin and delay of sleep in humans

The effect of light on circadian rhythms and sleep is mediated by a multi-component photoreceptive system of rods, cones and melanopsin-expressing intrinsically photosensitive retinal ganglion cells. The intensity and spectral sensitivity characteristics of this system are to be fully determined. Whether the intensity and spectral composition of light exposure at home in the evening is such that it delays circadian rhythms and sleep also remains to be established. We monitored light exposure at home during 6-8wk and assessed light effects on sleep and circadian rhythms in the laboratory. Twenty-two women and men (23.1±4.7yr) participated in a six-way, cross-over design using polychromatic light conditions relevant to the light exposure at home, but with reduced, intermediate or enhanced efficacy with respect to the photopic and melanopsin systems. The evening rise of melatonin, sleepiness and EEG-assessed sleep onset varied significantly (P<0.01) across the light conditions, and these effects appeared to be largely mediated by the melanopsin, rather than the photopic system. Moreover, there were individual differences in the sensitivity to the disruptive effect of light on melatonin, which were robust against experimental manipulations (intra-class correlation=0.44). The data show that light at home in the evening affects circadian physiology and imply that the spectral composition of artificial light can be modified to minimize this disruptive effect on sleep and circadian rhythms. These findings have implications for our understanding of the contribution of artificial light exposure to sleep and circadian rhythm disorders such as delayed sleep phase disorder.

Light exposure among adolescents with delayed sleep phase disorder: a prospective cohort study

The objective of this study was to compare light exposure and sleep parameters between adolescents with delayed sleep phase disorder (DSPD; n=16, 15.3±1.8 yrs) and unaffected controls (n=22, 13.7±2.4 yrs) using a prospective cohort design. Participants wore wrist actigraphs with photosensors for 14 days. Mean hourly lux levels from 20:00 to 05:00 h and 05:00 to 14:00 h were examined, in addition to the 9-h intervals prior to sleep onset and after sleep offset. Sleep parameters were compared separately, and were also included as covariates within models that analyzed associations with specified light intervals. Additional covariates included group and school night status. Adolescent delayed sleep phase subjects received more evening (p< .02, 22:00-02:00 h) and less morning (p .05, 08:00-09:00 h and 10:00-12:00 h) light than controls, but had less pre-sleep exposure with adjustments for the time of sleep onset (p< .03, 5-7 h prior to onset hour). No differences were identified with respect to the sleep offset interval. Increased total sleep time and later sleep offset times were associated with decreased evening (p< .001 and p= .02, respectively) and morning (p= .01 and p< .001, respectively) light exposure, and later sleep onset times were associated with increased evening exposure (p< .001). Increased total sleep time also correlated with increased exposure during the 9 h before sleep onset (p= .01), and a later sleep onset time corresponded with decreased light exposure during the same interval (p< .001). Outcomes persisted regardless of school night status. In conclusion, light exposure interpretation requires adjustments for sleep timing among adolescents with DSPD. Pre- and post-sleep light exposures do not appear to contribute directly to phase delays. Sensitivity to morning light may be reduced among adolescents with DSPD.

Circadian rhythm sleep disorders

This article begins with a review of the major central nervous system functional systems that allow for optimal alertness during the waking day, and the rapid initiation and good maintenance of sleep at night. Subsequent sections discuss each of the 6 primary circadian rhythm sleep disorders. Attention is paid to known or suspected pathophysiology, diagnostic criteria and assessment methodology, and treatment options. The article concludes with a discussion of challenges that must be met to improve the recognition and treatment of these quite impactful sleep disorders.

Timing of sleep and its relationship with the endogenous melatonin rhythm

While much research has investigated the effects of exogenous melatonin on sleep, less is known about the relationship between the timing of the endogenous melatonin rhythm and the sleep-wake cycle. Significant inter-individual variability in the phase relationship between sleep and melatonin rhythms has been reported although the extent to which the variability reflects intrinsic and/or environmental differences is unknown. We examined the effects of different sleeping schedules on the time of dim light melatonin onset (DLMO) in 28 young, healthy adults. Participants chose to maintain either an early (22:30-06:30 h) or a late (00:30-08:30 h) sleep schedule for at least 3 weeks prior to an overnight laboratory visit. Saliva samples were collected under dim light (<2 lux) and controlled posture conditions to determine salivary DLMO. The 2-h difference between groups in the enforced sleep-wake schedule was associated with a concomitant 1.75-h delay in DLMO. The mean phase relationship between sleep onset and DLMO remained constant (~2 h). The variance in DLMO time, however, was greater in the late group (range 4.5 h) compared to the early group (range 2.4 h) perhaps due to greater effect of environmental influences in delayed sleep types or greater intrinsic instability in their circadian system. The findings contribute to our understanding of individual differences in the human circadian clock and have important implications for the diagnosis and treatment of circadian rhythm sleep disorders, in particular if a greater normative range for phase angle of entrainment occurs in individuals with later sleep-wake schedules.

Sleep timing and circadian phase in delayed sleep phase syndrome

Delayed sleep phase syndrome (DSPS) is a circadian rhythm sleep disorder in which the timing of the sleep episode occurs later than desired and is associated with difficulty falling asleep, problems awakening on time (e.g., to meet work or school obligations), and daytime sleepiness. The phase relationship between the timing of sleep and endogenous circadian rhythms is critical to the initiation and maintenance of sleep, and significant alteration leads to impairment of sleep quality and duration. The aim of this retrospective study was to determine the phase relationship between sleep-wake times and physiological markers of circadian timing in clinic patients with DSPS. Objective and subjective measures of sleep timing and circadian phase markers (core body temperature and melatonin) were measured in patients with DSPS and compared with age-matched controls. As expected, significant delays in the timing of the major sleep episode and circadian phase of body temperature and melatonin rhythms were seen in the DSPS group when allowed to sleep at their own habitual schedules, but the phase relationship between sleep-wake times and circadian phase was similar between the 2 groups. These results suggest that the symptoms of insomnia and excessive daytime sleepiness in DSPS patients living under entrained real-life conditions cannot be explained by an alteration in the phase relationship between sleep-wake patterns and other physiological circadian rhythms.

The suitability of actigraphy, diary data, and urinary melatonin profiles for quantitative assessment of sleep disturbances in schizophrenia: A case report

Sleep disruption is a commonly encountered clinical feature in schizophrenic patients, and one important concern is to determine the extent of this disruption under "real" life situations. Simultaneous wrist actigraphy, diary records, and repeated urine collection for urinary 6-sulphatoxymelatonin (aMT6s) profiles are appropriate tools to assess circadian rhythms and sleep patterns in field studies. Their suitability for long-term recordings of schizophrenic patients living in the community has not been evaluated. In this case report, we document long-term simultaneous wrist actigraphy, light detection, repeated urine collection, and diary records as a suitable combination of non-invasive techniques to quantify and assess changes in sleep-wake cycles, light exposure, and melatonin profiles in a schizophrenic patient. The actigraph was well-tolerated by the patient, and compliance to diary records and 48 h urine collection was particularly good with assistance from family members. The data obtained by these techniques are illustrated, and the results reveal remarkable abnormal patterns of rest-activity patterns, light exposure, and melatonin production. We observed various rest-activity patterns, including phase-shifts, highly delayed sleep on- and offsets, and irregular rest-activity phases. The period of the rest-activity rhythm, light-dark cycle, and melatonin rhythm was longer than 24 h. These circadian abnormalities may reinforce the altered sleep patterns and the problems of cognitive function and social engagement associated with schizophrenic.

Idiopathic Chronic Sleep Onset Insomnia in Attention‐Deficit/Hyperactivity Disorder: A Circadian Rhythm Sleep Disorder

To investigate whether ADHD-related sleep-onset insomnia (SOI) is a circadian rhythm disorder, we compared actigraphic sleep estimates, the circadian rest-activity rhythm, and dim light melatonin onset (DLMO) in ADHD children having chronic idiopathic SOI with that in ADHD children without sleep problems. Participants were 87 psychotropic-medication-naïve children, aged 6 to 12 yrs, with rigorously diagnosed ADHD and SOI (ADHD-SOI) and 33 children with ADHD without SOI (ADHD-noSOI) referred from community mental health institutions and pediatric departments of non-academic hospitals in The Netherlands. Measurements were 1 wk, 24 h actigraphy recordings and salivary DLMO. The mean (+/-SD) sleep onset time was 21:38 +/- 0:54 h in ADHD-SOI, which was significantly (p < 0.001) later than that of 20:49 +/- 0:49 h in ADHD-noSOI. DLMO was significantly later in ADHD-SOI (20:32 +/- 0:55 h), compared with ADHD-noSOI (19:47 +/- 0:49 h; p < 0.001). Wake-up time in ADHD-SOI was later than in ADHD-noSOI (p = 0.002). There were no significant between-group differences in sleep maintenance, as estimated by number of wake bouts and activity level in the least active 5 h period, or inter- and intradaily rhythm variability. We conclude that children with ADHD and chronic idiopathic sleep-onset insomnia show a delayed sleep phase and delayed DLMO, compared with ADHD children without SOI.

Phenotypic effects of genetic variability in human clock genes on circadian and sleep parameters

Circadian rhythms and sleep are two separate but intimately related processes. Circadian rhythms are generated through the precisely controlled, cyclic expression of a number of genes designated clock genes. Genetic variability in these genes has been associated with a number of phenotypic differences in circadian as well as sleep parameters, both in mouse models and in humans. Diurnal preferences as determined by the selfreported Horne-Ostberg (HO) questionnaire, has been associated with polymorphisms in the human genes CLOCK, PER1, PER2 and PER3. Circadian rhythm-related sleep disorders have also been associated with mutations and polymorphisms in clock genes, with the advanced type cosegrating in an autosomal dominant inheritance pattern with mutations in the genes PER2 and CSNK1D, and the delayed type associating without discernible Mendelian inheritance with polymorphisms in CLOCK and PER3. Several mouse models of clock gene null alleles have been demonstrated to have affected sleep homeostasis. Recent findings have shown that the variable number tandem polymorphism in PER3, previously linked to diurnal preference, has profound effects on sleep homeostasis and cognitive performance following sleep loss, confirming the close association between the processes of circadian rhythms and sleep at the genetic level.

Circadian rhythm sleep disorders: characteristics and entrainment pathology in delayed sleep phase and non-24-h sleep-wake syndrome

This paper presents a clinical review of delayed sleep phase syndrome (DSPS) and non-24-h sleep-wake syndrome (non-24). These syndromes seem to be common and under-recognized in society, not only in the blind, but also typically emerging during adolescence. Both types of syndrome can appear alternatively or intermittently in an individual patient. Psychiatric problems are also common in both syndromes. DSPS and non-24 could share a common circadian rhythm pathology in terms of clinical process and biological evidence. The biological basis is characterized by a longer sleep period, a prolonged interval from the body temperature nadir-to-sleep offset, a relatively advanced temperature rhythm, lower sleep propensity after total sleep deprivation, and higher sensitivity to light than in normal controls. There are multiple lines of evidence suggesting dysfunctions at the behavioral, physiological and genetic levels. Treatment procedures and prevention of the syndromes require further attention using behavioral, environmental, and psychiatric approaches, since an increasing number of patients in modern society suffer from these disorders.

Delayed sleep phase disorder in temporal isolation

STUDY OBJECTIVES

This study sought to characterize sleep and the circadian rhythm of body core temperature of an individual with delayed sleep phase disorder (DSPD) in the absence of temporal cues and social entrainment and to compare those measures to age-matched normal control subjects studied under identical conditions.

DESIGN

Polysomnography and body temperature were recorded continuously for 4 days in entrained conditions, followed immediately by 17 days in a "free-running" environment.

SETTING

Temporal isolation facility in the Laboratory of Human Chronobiology, Weill Cornell Medical College.

PARTICIPANTS

One individual who met criteria for delayed sleep phase disorder according to the International Classification of Sleep Disorders Diagnostic and Coding Manual (ICSD-2) and 3 age-matched control subjects.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

The DSPD subject had a spontaneous period length (tau) of 25.38 hours compared to an average tau of 24.44 hours for the healthy controls. The DSPD subject also showed an altered phase relationship between sleep/wake and body temperature rhythms, as well as longer sleep latency, poorer sleep efficiency, and altered distribution of slow wave sleep (SWS) within sleep episodes, compared to control subjects.

CONCLUSIONS

Delayed sleep phase disorder may be the reflection of an abnormal circadian timing system characterized not only by a long tau, but also by an altered internal phase relationship between the sleep/wake system and the circadian rhythm of body temperature. The latter results in significantly disturbed sleep, even when DSPD patients are permitted to sleep and wake at their preferred times.

Constant light housing during nursing causes human DSPS (delayed sleep phase syndrome) behaviour in Clock-mutant mice

Delayed sleep phase syndrome (DSPS) is very often seen among patients with sleep-wake rhythm disorders. Humans with the 3111C allele of the human Clock gene tend to demonstrate a higher evening preference on the morningness-eveningness (ME) preference test. DSPS is thought to be an extreme form of this evening preference. Clock-mutant mice have been proposed as an animal model of evening preference. In this study, we looked at whether constant light (LL) housing of Clock-mutant mice during lactation would result in evening preference and/or DSPS. Housed under light-dark (LD) or constant dark (DD) conditions during the lactation period, both wild-type and Clock-mutant mice did not show a phase-delay in the locomotor activity measured under light-dark conditions, whereas constant light housing during lactation significantly caused a delayed onset. The magnitude of the delay during the light-dark cycle was positively associated with free-running period measured during constant darkness. Among wild, heterozygote, and homozygote pups born from heterozygous dams, only homozygote pups showed a delayed onset. Constant light-housed Clock-mutant mice exhibited a lower number and delayed peak of phospho-MAPK-immunoreactive cells in core regions of the suprachiasmatic nucleus (SCN) compared to light-dark housed wild-type or Clock-mutant mice. Activity onset returned to normal with daily melatonin injection at the lights-off time for 5 days. The present results demonstrate that Clock-mutant mice exposed to constant light during lactation can function as an animal model of DSPS and can be used to gain an understanding of the ethological aspects of DSPS as well as to find medication for its treatment.

Sleep, circadian rhythms, and delayed phase in adolescence

Sleep/wake timing shifts later in young humans during the second decade of life. In this review we describe sleep/wake patterns, changes in these patterns across adolescence, and evidence for the role of environmental, psychosocial, and biological factors underlying these changes. A two-process model incorporating circadian (Process C) and sleep/wake homeostatic (Process S) components is outlined. This model may help us to understand how developmental changes translate to shifted sleep/wake patterns. Delayed sleep phase syndrome (DSPS), which has a typical onset during the second decade of life, may be an extreme manifestation of homeostatic and circadian changes in adolescence. We describe symptoms, prevalence, and possible etiology of DSPS, as well as treatment approaches in adolescents.

Behavioral and psychiatric consequences of sleep-wake schedule disorders

Circadian rhythm sleep disorders (CRSDs) arise when an individual's sleep-wake rhythm mismatches the environmental 24-h schedule. Physiological data and genetic studies in patients with CRSDs suggest that these disorders result from abnormal functioning of the circadian timing system. Diagnosis involves recognition of the characteristics of CRSDs, which can be achieved by clinical interview and actigraphic monitoring of rest-activity patterns. Bright-light therapy and melatonin administration have proved to be the most effective treatment modalities of CRSDs. In psychiatric practice, CRSDs can be encountered on various occasions. Some evidence indicates that a deviant sleep-wake schedule might be a predisposing factor to personality disorders. CRSDs can emerge as an iatrogenic effect of certain psychoactive drugs, such as haloperidol and fluvoxamine. It is not uncommon that the daytime functional difficulties that accompany CRSDs are misinterpreted as symptoms of psychopathology. Recognition and awareness of these disorders should prevent years of erroneous diagnosis and treatment in these patients.

Intrinsic period and light intensity determine the phase relationship between melatonin and sleep in humans

The internal circadian clock and sleep-wake homeostasis regulate the timing of human brain function, physiology, and behavior so that wakefulness and its associated functions are optimal during the solar day and that sleep and its related functions are optimal at night. The maintenance of a normal phase relationship between the internal circadian clock, sleep-wake homeostasis, and the light-dark cycle is crucial for optimal neurobehavioral and physiological function. Here, the authors show that the phase relationship between these factors-the phase angle of entrainment (psi)-is strongly determined by the intrinsic period (tau) of the master circadian clock and the strength of the circadian synchronizer. Melatonin was used as a marker of internal biological time, and circadian period was estimated during a forced desynchrony protocol. The authors observed relationships between the phase angle of entrainment and intrinsic period after exposure to scheduled habitual wakefulness-sleep light-dark cycle conditions inside and outside of the laboratory. Individuals with shorter circadian periods initiated sleep and awakened at a later biological time than did individuals with longer circadian periods. The authors also observed that light exposure history influenced the phase angle of entrainment such that phase angle was shorter following exposure to a moderate bright light (approximately 450 lux)-dark/wakefulness-sleep schedule for 5 days than exposure to the equivalent of an indoor daytime light (approximately 150 lux)-dark/wakefulness-sleep schedule for 2 days. These findings demonstrate that neurobiological and environmental factors interact to regulate the phase angle of entrainment in humans. This finding has important implications for understanding physiological organization by the brain's master circadian clock and may have implications for understanding mechanisms underlying circadian sleep disorders.