Melanopsin-dependent phototransduction is impaired in delayed sleep-wake phase disorder and sighted non-24-hour sleep-wake rhythm disorder

Circadian photoentrainment varies by season and depressed state: associations between light sensitivity and sleep and circadian timing

STUDY OBJECTIVES

Altered light sensitivity may be an underlying vulnerability for disrupted circadian photoentrainment. The photic information necessary for circadian photoentrainment is sent to the circadian clock from melanopsin-containing intrinsically photosensitive retinal ganglion cells (ipRGCs). The current study tested whether the responsivity of ipRGCs measured using the post-illumination pupil response (PIPR) was associated with circadian phase, sleep timing, and circadian alignment, and if these relationships varied by season or depression severity.

METHODS

Adult participants (N = 323, agem = 40.5, agesd = 13.5) with varying depression severity were recruited during the summer (n = 154) and winter (n = 169) months. Light sensitivity was measured using the PIPR. Circadian phase was assessed using Dim Light Melatonin Onset (DLMO) on Friday evenings. Midsleep was measured using actigraphy. Circadian alignment was calculated as the DLMO-midsleep phase angle. Multilevel regression models covaried for age, gender, and time since wake of PIPR assessment.

RESULTS

Greater light sensitivity was associated with later circadian phase in summer but not in winter (β = 0.23; p = 0.03). Greater light sensitivity was associated with shorter DLMO-midsleep phase angles (β = 0.20; p = 0.03) in minimal depression but not in moderate depression (SIGHSAD < 6.6; Johnson-Neyman region of significance).

CONCLUSIONS

Light sensitivity measured by the PIPR was associated with circadian phase during the summer but not in winter, suggesting ipRGC functioning in humans may affect circadian entrainment when external zeitgebers are robust. Light sensitivity was associated with circadian alignment only in participants with minimal depression, suggesting circadian photoentrainment, a possible driver of mood, may be decreased in depression year-round, similar to decreased photoentrainment in winter.

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.

Case report: A patient with Delayed Sleep-Wake Phase Disorder and Optic Nerve Hypoplasia treated with tasimelteon: a case study

We present a case of an adult female diagnosed with Delayed Sleep-Wake Phase Disorder (DSWPD) and Optic Nerve Hypoplasia (ONH), with a confirmed delayed Dim Light Melatonin Onset (DLMO), who reports the inability to fall asleep at their desired bedtime and obtain adequate sleep nightly, despite the ability to have a full night's sleep when not required to be up at a specific time for societal requirements. The participant was enrolled in an 11-month Open-Label Extension (OLE) following the randomized portion of a clinical study and was successfully treated with tasimelteon. DSWPD symptoms were resolved, and their previously delayed sleep-wake cycle was advanced.

Clinical trial registration

https://clinicaltrials.gov/ct2/show/NCT04652882, identifier NCT04652882.

Pupillometry to differentiate idiopathic hypersomnia from narcolepsy type 1

Idiopathic hypersomnia is poorly diagnosed in the absence of biomarkers to distinguish it from other central hypersomnia subtypes. Given that light plays a main role in the regulation of sleep and wake, we explored the retinal melanopsin-based pupil response in patients with idiopathic hypersomnia and narcolepsy type 1, and healthy subjects. Twenty-seven patients with narcolepsy type 1 (women 59%, 36 ± 11.5 years old), 36 patients with idiopathic hypersomnia (women 83%, 27.2 ± 7.2 years old) with long total sleep time (> 11/24 hr), and 43 controls (women 58%, 30.6 ± 9.3 years old) were included in this study. All underwent a pupillometry protocol to assess pupil diameter, and the relative post-illumination pupil response to assess melanopsin-driven pupil responses in the light non-visual input pathway. Differences between groups were assessed using logistic regressions adjusted on age and sex. We found that patients with narcolepsy type 1 had a smaller baseline pupil diameter as compared with idiopathic hypersomnia and controls (p < 0.05). In addition, both narcolepsy type 1 and idiopathic hypersomnia groups had a smaller relative post-illumination pupil response (respectively, 31.6 ± 13.9% and 33.2 ± 9.9%) as compared with controls (38.7 ± 9.7%), suggesting a reduced melanopsin-mediated pupil response in both types of central hypersomnia (p < 0.01). Both narcolepsy type 1 and idiopathic hypersomnia showed a smaller melanopsin-mediated pupil response, and narcolepsy type 1, unlike idiopathic hypersomnia, also displayed a smaller basal pupil diameter. Importantly, we found that the basal pupil size permitted to well discriminate idiopathic hypersomnia from narcolepsy type 1 with a specificity = 66.67% and a sensitivity = 72.22%. Pupillometry may aid to multi-feature differentiation of central hypersomnia subtypes.

Post-Illumination Pupil Response and Sleep Quality in Patients With Glaucoma: The LIGHT Study

Purpose

This study aimed to investigate whether intrinsically photosensitive retinal ganglion cell function evaluated using post-illumination pupil response (PIPR) in patients with glaucoma is associated with sleep quality.

Methods

This cross-sectional study measured the PIPR in 138 patients with glaucoma (mean age, 70.3 years) using pupil diameter after red and blue light exposure. The net PIPR change was classified into three groups according to tertiles (i.e., low, intermediate, and high groups), with lower net PIPR change indicating lower intrinsically photosensitive retinal ganglion cell (ipRGC) function. Subjective and objective sleep qualities were assessed using the Pittsburgh Sleep Quality Index (PSQI) questionnaire and actigraphy, respectively, with a total PSQI score of ≥6 indicating sleep disturbance.

Results

The prevalence of subjective sleep disturbance significantly increased with decreasing tertile groups of net PIPR change (P = 0.036). Subgroup analysis obtained the same results in the severe glaucoma group (P = 0.004) but not in the non-severe glaucoma group. In the severe glaucoma group, multivariable logistic regression analysis adjusted for potential confounders showed a higher odds ratio for subjective sleep disturbance in the low-tertile group of net PIPR compared with the high-tertile group (odds ratio = 6.22; 95% confidence interval, 1.76-21.90; P = 0.004). Significant associations between PIPR and objective sleep quality (total sleep time, sleep efficiency, and wake after sleep onset) were found in the severe glaucoma group (P = 0.015, P = 0.013, and P = 0.015, respectively).

Conclusions

The PIPR in patients with glaucoma was significantly associated with decreased sleep quality, independent of potential confounders.

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.

Disease associations of excessive daytime sleepiness in multiple sclerosis: A prospective study

Background

Excessive daytime sleepiness (EDS) in multiple sclerosis (MS) can be a significant source of disability. Despite this, its prevalence as a patient-reported outcome in this condition has not been well established, and its causes are not well understood.

Methods

We prospectively assessed EDS as part of an observational study for patients referred for diagnostic neuro-ophthalmological testing. EDS was evaluated by the Epworth Sleepiness Scale (ESS), and visual data were also collected as part of a research protocol. Analysis with patient data was performed following the exclusion of patients with known primary sleep disorders.

Results

A total of 69 patients with MS were included in the analysis. The mean ESS was 6.5 with a SD of 4.3. ESS ≥ 10 was present in 23% of the cohort even in the presence of minimal mean neurological disability (Patient Determined Disease Steps (PDDS) = 1.5). The ESS score was not associated with age, sex, disease-related disability, retinal nerve fiber layer (RNFL), or optic neuritis (ON), but displayed an association with visual dysfunction.

Conclusions

There is an increased prevalence of EDS in MS. The increased values of the ESS are not explained by other sleep disorders, suggesting separate mechanisms. Further study of the underlying mechanisms is warranted.

Compression of the optic chiasm is associated with reduced photoentrainment of the central biological clock

OBJECTIVE

Pituitary tumours that compress the optic chiasm are associated with long-term alterations in sleep-wake rhythm. This may result from damage to intrinsically photosensitive retinal ganglion cells (ipRGCs) projecting from the retina to the hypothalamic suprachiasmatic nucleus via the optic chiasm to ensure photoentrainment (i.e. synchronisation to the 24-h solar cycle through light). To test this hypothesis, we compared the post-illumination pupil response (PIPR), a direct indicator of ipRGC function, between hypopituitarism patients with and without a history of optic chiasm compression.

DESIGN

Observational study, comparing two predefined groups.

METHODS

We studied 49 patients with adequately substituted hypopituitarism: 25 patients with previous optic chiasm compression causing visual disturbances (CC+ group) and 24 patients without (CC- group). The PIPR was assessed by chromatic pupillometry and expressed as the relative change between baseline and post-blue-light stimulus pupil diameter. Objective and subjective sleep parameters were obtained using polysomnography, actigraphy, and questionnaires.

RESULTS

Post-blue-light stimulus pupillary constriction was less sustained in CC+ patients compared with CC- patients, resulting in a significantly smaller extended PIPR (mean difference: 8.1%, 95% CI: 2.2-13.9%, P = 0.008, Cohen's d = 0.78). Sleep-wake timing was consistently later in CC+ patients, without differences in sleep duration, efficiency, or other rest-activity rhythm features. Subjective sleep did not differ between groups.

CONCLUSION

Previous optic chiasm compression due to a pituitary tumour in patients with hypopituitarism is associated with an attenuated PIPR and delayed sleep timing. Together, these data suggest that ipRGC function and consequently photoentrainment of the central biological clock is impaired in patients with a history of optic chiasm compression.

Case report: A novel missense variant in melanopsin associates with delayed sleep phenotype: Whole genome sequencing study

Melanopsin (OPN4) is a blue light-sensitive opsin-type G-protein coupled receptor. It is highly expressed in photosensitive retinal ganglion cells which mediate responses to light, including regulation of sleep, circadian photoentrainment, and pupillary light response. Mutations in OPN4 were shown to affect responses to light, ultimately affecting the regulation of circadian rhythms and sleep. In this study, we describe a male carrier of the OPN4 missense variant diagnosed with delayed sleep-wake phase disorder (DSWPD), with a consistent recurrent pattern of delayed sleep onset The rs143641898 [NM_033282.4:c.502C>T p.(Arg168Cys)] variant in the OPN4 gene was shown in a functional study to render the OPN4 protein non-functional. The variant is rare and likely increases the risk of DSWPD via its direct effect on the melanopsin pathway. This study offers useful insights for the differential diagnosis and ultimately treatment of DSWPD risk in which patients carry pathogenic variants in the OPN4 gene.

The melanopsin-mediated pupil response is reduced in idiopathic hypersomnia with long sleep time

Idiopathic hypersomnia (IH), characterized by an excessive day-time sleepiness, a prolonged total sleep time on 24 h and/or a reduced sleep latency, affects 1 in 2000 individuals from the general population. However, IH remains underdiagnosed and inaccurately treated despite colossal social, professional and personal impacts. The pathogenesis of IH is poorly known, but recent works have suggested possible alterations of phototransduction. In this context, to identify biomarkers of IH, we studied the Post-Illumination Pupil Response (PIPR) using a specific pupillometry protocol reflecting the melanopsin-mediated pupil response in IH patients with prolonged total sleep time (TST > 660 min) and in healthy subjects. Twenty-eight patients with IH (women 86%, 25.4 year-old ± 4.9) and 29 controls (women 52%, 27.1 year-old ± 3.9) were included. After correction on baseline pupil diameter, the PIPR was compared between groups and correlated to sociodemographic and sleep parameters. We found that patients with IH had a lower relative PIPR compared to controls (32.6 ± 9.9% vs 38.5 ± 10.2%, p = 0.037) suggesting a reduced melanopsin response. In addition, the PIPR was not correlated to age, chronotype, TST, nor depressive symptoms. The melanopsin-specific PIPR may be an innovative trait marker of IH and the pupillometry might be a promising tool to better characterize hypersomnia.

Publication guidelines and recommendations for pupillary measurement in psychophysiological studies

A variety of psychological and physical phenomena elicit variations in the diameter of pupil of the eye. Changes in pupil size are mediated by the relative activation of the sphincter pupillae muscle (decrease pupil diameter) and the dilator pupillae muscle (increase pupil diameter), innervated by the parasympathetic and sympathetic branches, respectively, of the autonomic nervous system. The current guidelines are intended to inform and guide psychophysiological research involving pupil measurement by (1) summarizing important aspects concerning the physiology of the pupil, (2) providing methodological and data-analytic guidelines and recommendations, and (3) briefly reviewing psychological phenomena that modulate pupillary reactivity. Because of the increased ease and tractability of pupil measurement, the goal of these guidelines is to promote accurate recording, analysis, and reporting of pupillary data in psychophysiological research.

Behaviorally and environmentally induced non-24-hour sleep-wake rhythm disorder in sighted patients

STUDY OBJECTIVES

To determine whether there was evidence of circadian or sleep-regulatory dysfunction in sighted individuals with non-24-hour sleep-wake rhythm disorder.

METHODS

Three sighted individuals with signs and/or symptoms of non-24-hour sleep-wake rhythm disorder were studied. Thirty-five- to 332-day laboratory and home-based assessments of sleep-wake and circadian timing, endogenous circadian period, photic input to the circadian pacemaker, and/or circadian and sleep-wake-dependent regulation of sleep were conducted.

RESULTS

No evidence of circadian dysfunction was found in these individuals. Instead, sleep-wake timing appeared to dissociate from the circadian timing system, and/or self-selected sleep-wake and associated light/dark timing shifted the circadian pacemaker later, rather than the circadian pacemaker determining sleep-wake timing.

CONCLUSIONS

These findings suggest that the etiology of this disorder may be light- and/or behaviorally induced in some sighted people, which has implications for the successful treatment of this disorder.

CITATION

Emens JS, St Hilaire MA, Klerman EB, et al. Behaviorally and environmentally induced non-24-hour sleep-wake rhythm disorder in sighted patients. J Clin Sleep Med. 2022;18(2):453-459.

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.

A classification approach to estimating human circadian phase under circadian alignment from actigraphy and photometry data

The time of dim light melatonin onset (DLMO) is the gold standard for circadian phase assessment in humans, but collection of samples for DLMO is time and resource-intensive. Numerous studies have attempted to estimate circadian phase from actigraphy data, but most of these studies have involved individuals on controlled and stable sleep-wake schedules, with mean errors reported between 0.5 and 1 hour. We found that such algorithms are less successful in estimating DLMO in a population of college students with more irregular schedules: Mean errors in estimating the time of DLMO are approximately 1.5-1.6 hours. We reframed the problem as a classification problem and estimated whether an individual's current phase was before or after DLMO. Using a neural network, we found high classification accuracy of about 90%, which decreased the mean error in DLMO estimation-identifying the time at which the switch in classification occurs-to approximately 1.3 hours. To test whether this classification approach was valid when activity and circadian rhythms are decoupled, we applied the same neural network to data from inpatient forced desynchrony studies in which participants are scheduled to sleep and wake at all circadian phases (rather than their habitual schedules). In participants on forced desynchrony protocols, overall classification accuracy dropped to 55%-65% with a range of 20%-80% for a given day; this accuracy was highly dependent upon the phase angle (ie, time) between DLMO and sleep onset, with the highest accuracy at phase angles associated with nighttime sleep. Circadian patterns in activity, therefore, should be included when developing and testing actigraphy-based approaches to circadian phase estimation. Our novel algorithm may be a promising approach for estimating the onset of melatonin in some conditions and could be generalized to other hormones.

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.