The two-process model of sleep regulation: a reappraisal

Acute hypoxia induces sleep disorders via sima/HIF-1α regulation of circadian rhythms in adult Drosophila

The atmospheric oxygen concentration is significantly reduced in highland regions compared to lowland areas. The first entering the plateau can induce sleep disorders in individuals, primarily attributed to insufficient oxygen supply. This study used Drosophila melanogaster as a model organism to better understand the molecular mechanism of acute hypoxia-induced sleep disorders. The Drosophila activity monitoring system (DAMS) was employed to observe the sleep-wake in adult (w1118, simaKG07607, and clockjrk) female flies. Quantifying the relative mRNA expression levels of sima and circadian clock genes in the head of flies was accomplished by utilizing qRT-PCR. Acute hypoxia caused sleep disorders in w1118 flies, such as shortened sleep duration and length, and prolonged sleep latency. PCR results showed that sima and clock genes were up-regulated in ZT6 and ZT12 and down-regulated in ZT0 and ZT18 in acute hypoxic w1118 flies compared to normoxic w1118 flies. Under normoxic conditions, sleep indexes in simaKG07607 flies were not substantially different from w1118 flies. However, clockjrk flies demonstrated a reduced sleep duration, decreased sleep bout length, and increased sleep latency and activities. Sleep and gene expression in simaKG07607 flies under acute hypoxic conditions were not significantly different from those under normoxic conditions. Surprisingly, sleep and gene expression in clockjrk flies showed opposite trends to w1118 flies. The present study indicates that acute hypoxia disrupt circadian rhythms through the activation of sima/HIF-1α, leading to the onset of sleep disorders, with Clock signaling potentially serving as a contributing factor.

Sleep deprivation in development of obesity, effects on appetite regulation, energy metabolism, and dietary choices

Sleep deprivation, which is a decrease in duration and quality of sleep, is a common problem in today's life. Epidemiological and interventional investigations have suggested a link between sleep deprivation and overweight/obesity. Sleep deprivation affects homeostatic and non-homoeostatic regulation of appetite, with the food reward system playing a dominant role. Factors such as sex and weight status affect this regulation; men and individuals with excess weight seem to be more sensitive to reward-driven and hedonistic regulation of food intake. Sleep deprivation may also affect weight through affecting physical activity and energy expenditure. In addition, sleep deprivation influences food selection and eating behaviours, which are mainly managed by the food reward system. Sleep-deprived individuals mostly crave for palatable energy-dense foods and have low desire for fruit and vegetables. Consumption of meals may not change but energy intake from snacks increases. The individuals have more desire for snacks with high sugar and saturated fat content. The relationship between sleep and the diet is mutual, implying that diet and eating behaviours also affect sleep duration and quality. Consuming healthy diets containing fruit and vegetables and food sources of protein and unsaturated fats and low quantities of saturated fat and sugar may be used as a diet strategy to improve sleep. Since the effects of sleep deficiency differ between animals and humans, only evidence from human subject studies has been included, controversies are discussed and the need for future investigations is highlighted.

Characterising the power spectrum dynamics of the non-REM to REM sleep transition

The transition from non-rapid eye movement (NREM) to rapid eye movement (REM) sleep is considered a transitional or intermediate stage (IS), characterised by high amplitude spindles in the frontal cortex and theta activity in the occipital cortex. Early reports in rats showed an IS lasting from 1 to 5 s, but recent studies suggested a longer duration of this stage of up to 20 s. To further characterise the IS, we analysed its spectral characteristics on electrocorticogram (ECoG) recordings of the olfactory bulb (OB), primary motor (M1), primary somatosensory (S1), and secondary visual cortex (V2) in 12 Wistar male adult rats. By comparing the IS with consolidated NREM/REM epochs, our results reveal that the IS has specific power spectral patterns that fall out of the NREM and REM sleep state power distribution. Specifically, the main findings were that sigma (11-16 Hz) power in OB, M1, S1, and V2 increased during the IS compared with NREM and REM sleep, which started first in the frontal part of the brain (OB -54 s, M1 -53 s) prior to the last spindle occurrence. The beta band (17-30 Hz) power showed a similar pattern to that of the sigma band, starting -54 s before the last spindle occurrence in the M1 cortex. Notably, sigma infraslow coupling (~0.02 Hz) increased during the IS but occurred at a slower frequency (~0.01 Hz) compared with NREM sleep. Thus, we argue that the NREM to REM transition contains its own local spectral profile, in accordance with previous reports, and is more extended than described previously.

Biological Fluid Flows: Signaling Mediums for Circadian Timing

While there is extensive literature on both the neuronal circuitry of rhythms and the intracellular molecular clock, there is a large component of signaling that has been understudied: interstitial fluid (ISF)-fluid that surrounds the cells in the extracellular space of tissue. In this review, we highlight evidence in the circadian literature supporting ISF signaling as key to circadian synchronization and entrainment and propose new mechanisms of how fluid movement between the brain and periphery may act as zeitgebers by examining the main ISF pathways of the body, focusing on circadian regulation of the glymphatic and lymphatic systems. We identify key pieces of circadian research that point to ISF as an important timing medium, expand on the basics of cerebrospinal fluid (CSF) and ISF production, and outline the basic structure and function of the glymphatic and lymphatic systems.

The Attitudes, Beliefs and Perspectives of Registered Nurses on Sleep Health Management in Residential Aged Care Facilities: A Qualitative Study

AIM

To explore the attitudes, beliefs and perspectives of registered nurses (RNs) regarding sleep health and sleep health management of residents living in aged care settings in Australia.

DESIGN

Qualitative inductive thematic analysis of semi-structured interviews.

METHODS

Semi-structured interviews were conducted with RNs working in residential aged care facilities using a topic guide between August 2021 and April 2022. Participants were recruited using a convenience-based and snowball sampling approach. Interviews were audio-recorded, transcribed verbatim and inductively analysed for emergent themes.

RESULTS

Eighteen interviews were conducted with RNs working in aged care. Thematic analysis of the data derived three main themes: (i) Awareness and observations of sleep health, (ii) assessment and management of sleep disturbances and (iii) barriers to implementing evidence-based sleep health management. It was found that the most common barrier to providing evidence-based sleep health practices was related to workplace constraints. Participants detailed the limitations of the RN's professional role and ability to work autonomously in sleep health practices.

CONCLUSION

Despite the intentions of RNs to implement evidence-based non-pharmacological strategies for sleep health management, pharmacological interventions prevail. Systemic efforts to address organisational constraints in aged care may improve sleep disturbance management and assist with shifting the current attitudes around sleep health in aged care facilities.

IMPLICATIONS FOR THE PROFESSION AND PATIENT CARE

This study highlights that current sleep health management of residents in residential aged care is inadequate. Upskilling nurses in sleep health care techniques and improving organisational commitment to such care provision are issues urgently required to enhance the sleep health of residents.

IMPACT

Current sleep health practices are not evidence-based in residential aged care. Optimising sleep practices in residential aged care that are person-centred is likely to improve quality of life and healthy ageing.

PATIENT OR PUBLIC CONTRIBUTION

No patient or public contribution.

The effects of daylight saving time clock changes on accelerometer-measured sleep duration in the UK Biobank

We explored the effects of daylight saving time clock changes on sleep duration in a large accelerometer dataset. Our sample included UK Biobank participants (n = 11,780; aged 43-78 years) with accelerometer data for one or more days during the 2 weeks surrounding the Spring and Autumn daylight saving time transitions from October 2013 and November 2015. Between-individual t-tests compared sleep duration on the Sunday (midnight to midnight) of the clock changes with the Sunday before and the Sunday after. We also compared sleep duration on all other days (Monday-Saturday) before and after the clock changes. In Spring, mean sleep duration was 65 min lower on the Sunday of the clock changes than the Sunday before (95% confidence interval -72 to -58 min), and 61 min lower than the Sunday after (95% confidence interval -69 to -53). In Autumn, the mean sleep duration on the Sunday of the clock changes was 33 min higher than the Sunday before (95% confidence interval 27-39 min), and 38 min higher than the Sunday after (95% confidence interval 32-43 min). There was some evidence of catch-up sleep after both transitions, with sleep duration a little higher on the Monday-Friday than before, although this was less pronounced in Autumn. Future research should use large datasets with longer periods of accelerometer wear to capture sleep duration before and after the transition in the same individuals, and examine other aspects of sleep such as circadian misalignment, sleep fragmentation or daytime napping.

Within-subjects ultra-short sleep-wake protocol for characterising circadian variations in retinal function

Prior studies suggest that visual functions undergo time-of-day variations. Under naturalistic entrainment, diurnal changes in physiology may be driven by circadian and/or homeostatic processes, and repeated measurements at different times of day are thus not suitable to draw unambiguous conclusions about circadian effects on visual function. In this study, we disentangle circadian and homeostatic effects on variations of retinal function. We examine the earliest stages of image-forming (temporal contrast sensitivity of the post-receptoral channels) and non-image forming visual functions (pupillary light response) by employing a short forced-desynchrony multiple-naps protocol lasting 40 hours. Participants (n = 12, 50% female) will stay in a controlled time-isolating environment under dim-light conditions and adhere to an ultra-short sleep-wake cycle, alternating between 2h30m of wake time in dim light and hour of sleep in no light. During eleven intervals of wakefulness, participants will undergo psychophysical and pupillometric assessments with silent-substitution stimuli. We hypothesize that the sensitivity of retinal mechanisms undergoes circadian variations. This hypothesis will be investigated by separately determining psychophysical contrast thresholds to silent-substitution stimuli targeting the post-receptoral (consistency) pathways (isoluminant red-green, L-M; isoluminant blue-yellow, S; luminance, L+M+S). We will furthermore measure the pupillary light response to peripheral stimuli (annulus 10∘-30∘) in comparison to the response to stimuli isolating or including melanopsin stimulation. All stimuli will be delivered at constant retinal irradiance using a Maxwellian view system or artificially restricting pupil size. Additionally, we will quantify and report effects of our test stimuli on the circadian system by comparing the dim light melatonin onset (DLMO) timing during two supplementary evening sessions, comparing dim-light conditions to such with experimental light exposure. Our work informs the fundamental biological mechanisms underlying the influence of light on the human circadian system. Based on our findings, current models about the sensitivity of the circadian system may need to be modified in order to account for the bidirectional influence of circadian function and photoreception.

Bibliometric and visual analysis of circadian rhythms in depression from 2004 to 2024

INTRODUCTION

Understanding the intricate relationship between circadian rhythms and depression is crucial for developing effective interventions and treatments for individuals affected by depression. Circadian rhythms regulate various physiological and behavioral processes, while depression manifests as persistent feelings of sadness and disturbances in sleep, appetite, and energy levels. Emerging research suggests a significant interplay between circadian rhythm disruption and depression, highlighting the need for comprehensive analysis in this area.

METHODOLOGY

A bibliometric and visual analysis of literature on circadian rhythms in depression from 2004 to 2024 was conducted using the Web of Science Core Collection. Data were analyzed using bibliometric tools including VOSviewer, CiteSpace, and Bibliometrix to identify publication trends, geographical distribution, authorship patterns, institutional collaborations, journal preferences, keyword co-occurrence, and highly cited references.

RESULTS

Analysis revealed a steady increase in publications and citations related to circadian rhythms in depression. The United States emerged as the leading contributor, with strong global collaborations. Key journals included Chronobiology International and Journal of Affective Disorders. Top keywords included circadian rhythm, depression, sleep, melatonin, and bipolar disorder. The most cited article is a review titled "Practice parameters for the indications for polysomnography and related procedures: An update for 2005".

CONCLUSIONS

This study offers a comprehensive overview of research on circadian rhythms in depression, highlighting key trends, contributors, and interdisciplinary intersections.

Exploring the nexus: Sleep disorders, circadian dysregulation, and Alzheimer's disease

We reviewed the connections among Alzheimer's disease (AD), sleep deprivation, and circadian rhythm disorders. Evidence is mounting that disrupted sleep and abnormal circadian rhythms are not merely symptoms of AD, but are also involved in accelerating the disease. Amyloid-beta (Aβ) accumulates, a feature of AD, and worsens with sleep deprivation because glymphatic withdrawal is required to clear toxic proteins from the brain. In addition, disturbances in circadian rhythm can contribute to the induction of neuroinflammation and oxidative stress, thereby accelerating neurodegenerative processes. While these interactions are bidirectional, Alzheimer's pathology further disrupts sleep and circadian function in a vicious cycle that worsens cognitive decline, which is emphasized in the review. The evidence that targeting sleep and circadian mechanisms may serve as therapeutic strategies for AD was strengthened by this study through the analysis of the molecular and physiological pathways. Further work on this nexus could help unravel the neurobiological mechanisms common to the onset of Alzheimer's and disrupted sleep and circadian regulation, which could result in earlier intervention to slow or prevent the onset of the disease.

Enhancing the Management of Hypersomnia: Examining the Role of the Orexin System

Excessive daytime sleepiness (EDS) is common. However, clinical features of excessive sleepiness can have broad and variable presentations. In addition, there can be an increased likelihood of medical or psychiatric comorbidity. Examination of the networks that regulate sleep-wake and circadian control reveals a complex and intricately designed integration system. Dysregulation in the coordination, effectiveness, or efficiency of these systems can contribute to developing EDS, and inform on the endotypes observed and pharmacologic considerations for treatment. The discovery and characterization of the diurnal expression and function of orexin (hypocretin) have led to a transformed understanding of sleep-wake control and EDS, as well as its role beyond sleep. As a result, a novel drug class, orexin agonists, is anticipated to emerge for clinical use in the near future. An understanding of orexin physiology and its transdisciplinary impact is necessary to best prepare for patient selection, use, and anticipated benefit and monitoring of both expected benefits and any other health change. This study provides a review of the range of clinical features and impact of EDS, the relationship between sleep-wake, circadian and other health networks, and an examination of orexin physiology with anticipatory guidance on the potential transdisciplinary role and impact of orexin agonists.

Hydrogen peroxide in midbrain sleep neurons regulates sleep homeostasis

Sleep could protect animals from oxidative damage, yet the dynamic interplay between the redox state and sleep homeostasis remains unclear. Here, we show that acute sleep deprivation (SD) in mice caused a general increase in brain oxidation, particularly in sleep-promoting regions. In vivo imaging of intracellular hydrogen peroxide (H2O2) real-time dynamics revealed that in nigra sleep neurons, the increase in cytosolic but not mitochondrial H2O2 reflects sleep debt and tracks spontaneous wakefulness by positively correlating with wake duration. By controllably manipulating intraneuronal H2O2, we discovered that H2O2 elevation is required for compensatory sleep and causally promotes sleep initiation, at least partly dependent on transient receptor potential melastatin 2 (TRPM2) channel. However, excessive H2O2 induced brain inflammation and sleep fragmentation. Together, our study demonstrates intraneuronal H2O2 as a crucial signaling molecule that translates brain redox imbalance into sleep drive and underscores the significance of oxidative eustress in sleep homeostasis.

Prenatal and Childhood Phthalate Mixtures and Adolescent Sleep Health in the HOME Study

BACKGROUND

The biological mechanisms linking early life phthalate exposure with adverse behaviors and cardiometabolic conditions also impact sleep health, but whether early life exposure impacts adolescent sleep is unknown.

OBJECTIVES

We evaluated whether gestational and childhood urinary phthalate metabolite mixtures were associated with sleep characteristics during adolescence. We also examined periods of heightened susceptibility to individual phthalates.

METHODS

In the Health Outcomes and Measures of the Environment (HOME) Study (Cincinnati, Ohio; 2003-2006; n = 156 ), we quantified urinary metabolites of eight parent phthalate diesters during pregnancy (16- and 26-wk) and childhood (ages 1, 2, 3, 4, 5, 8, and 12 years). Using regression calibration approaches, we estimated average measurement error-corrected phthalate metabolite concentrations during pregnancy and childhood. We used wrist actigraphy to assess sleep characteristics for 1 wk among participants at age 12. Using quantile-based g-computation, we estimated covariate-adjusted differences in sleep efficiency (%), sleep fragmentation index scores (%), sleep duration (minutes) per quartile increase in all phthalate metabolite concentrations (ψ ), and weights indicating the contribution of each metabolite to ψ . Using multiple informant models, we examined whether associations between individual phthalate metabolites and sleep characteristics varied by timing of exposure.

RESULTS

Increasing all gestational phthalate metabolites by a quartile was associated with lower sleep efficiency [ψ = - 1.3 % ; 95% confidence interval (CI): - 2.4 , - 0.3 ] and higher sleep fragmentation (ψ = 1.6 % ; 95% CI: 0.3, 3.0); mono-n-butyl phthalate (MnBP) and di(2-ethylhexyl) phthalate (DEHP) metabolites contributed most to these relations. Higher childhood phthalate metabolite mixture quartiles were associated with shorter sleep duration (ψ = - 21 minutes; 95% CI: - 34 , - 9 ); monoethyl phthalate (MEP) and monocarboxyoctyl phthalate (MCOP) contributed most to this association. We found that higher DEHP metabolite concentrations during pregnancy were more strongly related to higher sleep fragmentation than childhood concentrations. In contrast, higher MEP and MnBP concentrations during childhood, but not pregnancy, were consistently associated with shorter sleep duration.

DISCUSSION

Phthalate metabolite concentrations during pregnancy and childhood were associated with poorer adolescent sleep health. https://doi.org/10.1289/EHP15221.

Australian Naturopaths Approach to the Clinical Management of Patients Presenting with Sleep Disorders

Objective: Naturopathic practitioners consult an estimated 6.2% of Australian adults, equating to 1,550,000 people receiving their care each year. Sleep is now recognized as a key pillar of health; however, nearly half of all Australian adults report inadequate sleep. Evidence suggests that many Australians consult naturopaths (NPs) for sleep-related problems and use complementary medicines (CMs) to manage these. However, NPs' clinical approach to caring for people living with sleep disorders has not been reported. Therefore, the aim of this study was to describe and understand the clinical assessment and treatment approaches used by NPs in their care of people living with sleep disorders. Materials and Methods: A cross-sectional online survey with a purposively sought sample. NPs were recruited via the practitioner research-based network. The participants received an email invitation containing a link to the survey along with a Participant Information Sheet. The online survey (Research Electronic Data Capture-see Supplementary Data S1) comprised multiple-choice, binary (yes/no) questions, or 5-point Likert scale-type questions structured across four sections related to: clinical assessment of patients, treatments used, interprofessional communication with conventional doctors, and demographics. Results: Sixty-seven complete data sets were analyzed. Most survey participants treated-one to three patients with sleep disorders weekly, being consulted primarily for insomnia (82%) and its treatment (98.5%). Comprehensive sleep health histories were commonly assessed. Additionally, 69% of participants reported that patients sought their services to complement conventional care. The most frequently used complementary medicine (CM) approaches included sleep hygiene counseling (75%) and meditation (64.7%). Vitamins, minerals, herbal medicines, and nutritional supplements were the most recommended CM medicines (92.6%). Referrals to conventional medicine professionals were minimal. Conclusion: Australian NPs are frequently consulted by people living with sleep disorders who are also using conventional medicines. Our study highlights the need for integrated models of health care tailored to patient needs that maximize potential benefits and reduce any harms associated with drug-CMs interactions. The provision of training to the Australian health care workforce of NPs that focuses on evidence-based behavioral treatments can improve access to these treatments for patients.

Differential Effects of Light Spectra on Sleep Architecture and Melatonin in Rats

Artificial light exposure, particularly from blue-rich sources, has raised concerns about its impact on sleep and circadian rhythms. While blue light's effects are well-documented, the comparative impact of longer wavelengths, such as orange light (590-635 nm), remains underexplored. This study investigated the effects of 8 h blue (470-490 nm) and orange light exposures (500 lux) on sleep architecture in the next consecutive three days in Sprague-Dawley rats during the light or dark phase of a 12:12 h light-dark cycle. Sleep-wake states were assessed via electroencephalography (EEG) over 72 h. Blue light during the light period suppressed rapid eye movement (REM) sleep acutely and enhanced non-NREM sleep on Days 2 and 3. Orange light during the light period induced no immediate changes but increased NREM sleep on Day 2 with a biphasic REM response-suppression followed by rebound-persisting into Day 3. Blue light during the dark period increased NREM sleep during exposure, followed by suppression in the subsequent light period, with effects normalizing by Day 2. Blue light exposure suppressed melatonin levels compared to controls. These findings highlight spectral and temporal influences on sleep, with blue light exerting stronger acute effects and orange light eliciting delayed, biphasic responses. The results suggest implications for managing light exposure to mitigate sleep disruptions in modern environments.

Dynamics of glia and neurons regulate homeostatic rest, sleep and feeding behavior in Drosophila

Homeostatic processes, including sleep, are critical for brain function. Here we identify astrocyte-like glia (or astrocytes, AL) and ensheathing glia (EG), the two major classes of glia that arborize inside the brain, as brain-wide, locally acting homeostats for the short, naturally occurring rest and sleep bouts of Drosophila, and show that a subset of neurons in the fan-shaped body encodes feeding homeostasis. We show that the metabolic gas carbon dioxide, changes in pH and behavioral activity all induce long-lasting calcium responses in EG and AL, and that calcium levels in both glia types show circadian modulation. The homeostatic dynamics of these glia can be modeled based on behavior. Additionally, local optogenetic activation of AL or EG is sufficient to induce rest. Together, these results suggest that glial calcium levels are homeostatic controllers of metabolic activity, thus establishing a link between metabolism, rest and sleep.

Multi-task exercise increases delta power in non-rapid eye movement sleep among older female adults: A randomized crossover trial

Delta power in electroencephalography during sleep has been used as a more quantitative approach to determine sleep depth and quality. Despite the positive effects of both exercise and cognitive activity on delta power during sleep, limited information is available regarding the effects of multi-task exercise, which combines these two activities. Therefore, this study aimed to investigate the impact of multi-task exercise on delta power during sleep. Fifteen older female adults participated in both multi-task and single-task exercises at low and moderate-to-vigorous intensities for 30 min each. Sleep architecture was recorded using polysomnography to compare the amount of delta power during sleep. Additionally, cortical hemodynamic changes in the prefrontal cortex were monitored using functional near-infrared spectroscopy before and after each exercise session. Low-intensity multi-task exercise increased cortical activation in the right and left ventrolateral prefrontal cortex and frontopolar area, which positively correlated with the increase in delta power. This study provides the first experimental evidence that low-intensity multi-task exercise enhances cortical activation in the prefrontal cortex of older female adults, leading to an increase in delta power during sleep. It also suggests that low-intensity multi-task exercise may be a more useful intervention for improving sleep quality in older adults.

EEG spectral analysis of nighttime sleep and daytime MSLTs and neurocognitive evaluations in subjects with co-morbid insomnia and OSA

BACKGROUND

Chronic insomnia and obstructive sleep apnea commonly co-occur. Few studies have explored the neurophysiological and neurocognitive characteristics of COMISA, which could help guide improving treatment diagnostic tools and determining novel therapeutic targets. This study aims to explore the neurophysiological and neurocognitive characteristics of COMISA using electroencephalographic (EEG) spectral analysis and subjective and objective neurocognitive measurements.

METHODS

Participants were from our community recruited OSA-insomnia-COMISA cohort with 206 included for our current analysis including 74 chronic insomniacs (CIs), 55 OSA patients and 77 COMISA patients. Standard polysomnography (PSG) and multiple sleep latency tests (MSLTs) were recorded and used to obtain relative EEG spectral power in each sleep stage during PSG and each session during MSLTs. A series of subjective and objective neurocognitive tests were conducted to evaluate executive function, attention, retrospective and prospective memory and meta-cognition.

RESULTS

In PSG and MSLTs, COMISA patients showed combined EEG power characteristics of both CIs and OSA. Specifically, COMISA patients exhibited similar EEG spectral characteristics to CIs, with decreased delta and increased alpha and beta power in NREM sleep stages, and increased beta power in REM and MSLTs. Similar to the EEG spectral power profile of OSA, COMISA patients showed increased delta power in REM and MSLTs. Compared to OSA patients, COMISA patients exhibited worse subjectively measured attention and meta-cognition related to negative beliefs about uncontrollability and danger of worry (NEG), which were positively associated with ISI scores.

CONCLUSIONS

The EEG spectral power characteristics of COMISA patients in overnight PSG and daytime MSLT appear to be the manifestation of elements of both CIs and OSA. However, the neurocognitive features of COMISA patients in subjectively measured attention and NEG meta-cognition were primarily affected by chronic insomnia.

Maternal depressive symptoms in and beyond the perinatal period: associations with infant and preschooler sleep

STUDY OBJECTIVES

(1) To describe sleep in infancy and early childhood among children born to mothers with and without clinically significant depressive symptoms, and (2) to explore the relationships between maternal depressive symptoms and sleep patterns and problems during infancy and early childhood.

METHODS

Secondary analysis of longitudinal data from the Moe Kura: Mother and Child, Sleep and Wellbeing in Aotearoa/New Zealand study. Data were collected in pregnancy (T1), 12 weeks postpartum (T2), and 3 years post-birth (T3). Participants were 262 Māori and 594 non-Māori mother-child dyads. Chi-square and independent t-tests measured bivariate associations between maternal mood (T1, T2, and T3) and child sleep characteristics (T2 and T3). Binary logistic regression models examined longitudinal and concurrent associations between maternal depressive symptoms and infant and preschooler sleep. Adjusted models accounted for key socio-demographic variables, as well as infant sleep variables in preschooler models.

RESULTS

Bivariate associations were found between prior and concurrent depressive symptomology and many of the infant and preschooler sleep outcomes. In adjusted models, prenatal depressive symptoms remained independently associated with shorter-than-recommended sleep durations in preschoolers. In these models, concurrent depression was also associated with night waking, night LSRSP, and perceived sleep problems at 12 weeks postpartum, and CSHQ-determined and perceived sleep problems at 3 years post-birth.

CONCLUSIONS

Longitudinal and cross-sectional associations were found between maternal depressive symptoms and child sleep. Sleep appears to be one pathway by which maternal depression confers risk for suboptimal child health outcomes. Findings support the need for earlier and better maternal mental health services.

The role of sleep traits in prostate, endometrial, and epithelial ovarian cancers: An observational and Mendelian randomisation study

Background

Sleep traits may influence cancer risk; however, their associations with prostate (PCa), endometrial (ECa), and epithelial ovarian (EOCa) cancer remain unclear.

Methods

We conducted an observational analysis using the UK Biobank cohort and a two-sample Mendelian randomisation (MR) analysis to investigate the association of six sleep traits-duration, chronotype, insomnia, daytime napping, daytime sleepiness, and snoring-with PCa, ECa, and EOCa risk. Cox proportional hazards models were used for the observational analysis, while the inverse variance-weighted (IVW) method was applied in MR, with multiple sensitivity analyses. A Bonferroni correction accounted for multiple testing.

Results

Among 8,608 PCa, 1,079 ECa, and 680 EOCa incident diagnoses (median follow-up: 6.9 years), snoring was associated with reduced EOCa risk (HR=0.78, 95%CI: 0.62-0.98), while daytime sleepiness was associated with increased EOCa risk (HR=1.23, 95%CI: 1.03-1.47). However, these associations were not confirmed in MR. MR suggested higher odds of PCa (OR IVW =1.05, 95%CI: 1.01-1.11) and aggressive PCa (OR IVW =1.10, 95%CI: 1.02-1.19) for evening compared to morning chronotype. None of the findings survived multiple testing correction.

Conclusion

Sleep traits were not associated with PCa, ECa, or EOCa risk, but evening chronotype may increase PCa risk. Further research is needed to verify this association and investigate potential underlying mechanisms.

Impact

The proposed results have potential utility in reproductive cancer prevention.

What is already known on this topic

Sleep traits have been implicated in cancer risk, but their associations with prostate, endometrial, and epithelial ovarian cancer remain unclear.

What this study adds

This study found suggestive evidence that an evening chronotype may be associated with an increased risk of overall and aggressive prostate cancer.

How this study might affect research practice or policy

Further research is needed to confirm the potential association between chronotype and prostate cancer risk, which could inform personalised cancer prevention strategies.

JACUZI-SD: An automated, high-throughput, minimally stressful approach to sleep depriving larval zebrafish

While sleep deprivation broadly disrupts health and well-being, the neural and molecular mechanisms that signal increased sleep pressure remain poorly understood. A key obstacle to progress is the fact that traditional methods for inducing sleep deprivation (SD) in animal models often introduce confounding stress or disrupt circadian rhythms. Here, we present JACUZI-SD (Jetting Automated Currents Under Zebrafish to Induce Sleep Deprivation), a fully automated, high-throughput system designed to induce sleep deprivation in larval zebrafish with minimal stress. By delivering randomized water pulses via a custom milli-fluidic device integrated with a 96-well plate and controlled by an Arduino, JACUZI-SD promotes wakefulness during the natural dark cycle without the stress associated with existing SD methods. Our results demonstrate that JACUZI-SD reduces total sleep time by 41-64% and elicits a robust rebound sleep characterized by increased sleep bout length following deprivation. Importantly, this method avoids activating the hypothalamic-pituitary-interrenal (HPI) stress axis, as shown by reduced stress marker expression compared to other sleep deprivation methods. Additionally, the system reliably activates known sleep pressure pathways, including upregulating galanin expression in the neurosecretory preoptic area, while also revealing biologically relevant inter-individual variability in homeostatic rebound responses. JACUZI-SD provides a powerful, minimally invasive platform for dissecting the neural and molecular underpinnings of sleep homeostasis in vertebrates.

Associations between real-life light exposure patterns and sleep behaviour in adolescents

One of the most striking changes in the regulation of sleep-wake behaviour during adolescence is circadian phase delay. Light exposure synchronises circadian rhythms, impacting sleep regulation, however, the influence of real-life light exposure on sleep variations remains less clear. We aimed to describe the sleep and light exposure patterns of high school students with comparable schedules and socio-economic backgrounds, and to evaluate whether there was any association between them, considering chronotype. We analysed five school days and two free days of actigraphy records, from 35 adolescents (24 female, mean age: 16.23 ± 0.60). The sample was described using the Sleep Regularity Index (SRI), chronotype (actigraphy MSFsc), and self-reported diurnal preference (Morning/Evening Scale). Regression models were constructed to assess the impact of light exposure (daytime and nighttime) on subsequent sleep episodes; and to confirm whether the associations could be an indirect consequence of chronotype. Despite following similar routines, the SRI varied considerably (48.25 to 88.28). There was compatibility between the actigraphy proxy for chronotype and the self-reported diurnal preference, extracted using the circadian rhythm scale for adolescents. Less light exposure during the day was associated with later sleep onset and shorter sleep duration. An increase of 100 lux in average daytime light exposure advance of 8.08 minutes in sleep onset and 7.16 min in sleep offset. When the regressions were controlled for chronotype, these associations persisted. These findings facilitate discussions regarding the behavioural aspect of the impact of real-life light exposure on sleep and its potential as a target for interventions aiming to enhance adolescents' sleep quality.

The effects of diazepam on sleep depend on the photoperiod

Daylength (i.e., photoperiod) provides essential information for seasonal adaptations of organisms. Earlier studies have demonstrated that photoperiod influences sleep in several species. Notably, photoperiod can change the excitatory/inhibitory balance in the brain, with long photoperiod exhibiting increased γ-aminobutyric-acid (GABA)-mediated excitation. In this study, we first investigated whether different photoperiods influence sleep and the sleep electroencephalogram (EEG) in mice, and, subsequently, whether these photoperiods alter GABAergic functioning by treating mice with diazepam (3 mg/kg, i.p.). EEG and electromyogram (EMG) recordings were conducted in mice well-adapted to long or short photoperiod (16:8 vs. 8:16 light-dark cycle) in baseline conditions, after 4-h sleep deprivation, and following diazepam administration. Different photoperiods led to a redistribution of sleep and wakefulness in 24-h albeit without altering the overall amount of vigilance states; during darkness, mice exposed to the long photoperiod were more awake and showed very little rapid-eye-movement (REM) sleep compared to the short photoperiod. Furthermore, an overall lower EEG power density, across all vigilance states, was found in the long compared to short photoperiod. After diazepam treatment, slow-wave-activity (SWA) in NREM sleep was suppressed independent of the photoperiod. However, following diazepam administration, mice showed more REM sleep in the short photoperiod, and increased EEG power density in the slower frequencies (2.5-7 Hz), during wakefulness in the long photoperiod. These results demonstrate that photoperiod can affect the diazepam-induced changes on sleep architecture and EEG, suggesting that treatments with GABAA agonists exert dissimilar effects depending on the photoperiod. Future studies are warranted to explore potential photoperiod effects in humans which could have consequences for the treatment of anxiety and sleep disturbances.

Dynamic impacts of sleep disruption on ecologically assessed affective, behavioral, and cognitive risk factors for suicide: a study protocol

Diminished sleep health is a known warning sign for suicide. However, the contexts and time periods within which diminished sleep elevates suicide risk are unknown. Modeling the complex process by which diminished sleep health impacts daily functioning and establishing proximal suicide risk factors can aid in addressing these important knowledge gaps. This paper describes the methods and research protocol for a study that aims to elucidate the nature of the sleep-suicide relationship and develop an integrated model of proximal suicide risk. Participants will be 200 adults at high risk for suicide recruited from a psychiatric inpatient unit. They will complete a baseline assessment including clinical interviews and self-reports, and laboratory tasks with concurrent electroencephalography to phenotype-relevant risk processes. This baseline assessment will be followed by 4 weeks of ecological momentary assessment and digital phenotyping, coupled with assessments of sleep via a wearable used to generate a minute-by-minute metric of cognitive effectiveness using the Sleep Activity, Fatigue, and Task Effectiveness algorithm index. Follow-up assessments will be conducted 1-, 3-, and 6-months post-hospital discharge to determine how the developed proximal model of risk prospectively predicts suicidal ideation and behavior. The results of this study have the potential to greatly enhance understanding of how and why diminished sleep health is related to real-world fluctuations in suicide risk, knowledge that can inform efforts to better prevent, and intervene to reduce suicides.

A meta-analytic investigation of the effect of sleep deprivation on inhibitory control

Sleep deprivation may have a deleterious effect on inhibitory control; however, this effect is not consistent across studies. To arrive at an overall estimate of the relationship between sleep deprivation and inhibitory control, this report used meta-analysis to summarise the magnitude of the effects of sleep deprivation on inhibitory control as measured by the Go/No-Go and Stop Signal Tasks. These are two widely used tasks in the literature. A systematic search of four databases (APAPsycINFO, Medline, CINAHL and Embase) from their inception to November 2023 identified 24 studies involving 712 healthy individuals. Separate random-effects models were used to estimate the effect size of sleep deprivation on performance in these tasks. The meta-analysis revealed a moderate negative effect of sleep deprivation on inhibitory control in both the Go/No-Go and Stop Signal Tasks. Given the importance of inhibitory control in everyday behaviour, future research should investigate the neural and neurophysiological mechanisms underlying this relationship and explore its impact in clinical populations.

The relationship between sleep and interoception

The present study aimed to characterise the relationship between sleep and interoception in two independent studies. Theoretical grounds for such a relationship include a weak relationship between subjectively- and objectively-measured sleep, the covariance of sleep with pain, as well as the mass regulation of a number of visceral biological systems. In addition, such a relationship is often reflected in our language (i.e., 'feeling' tired). In both studies (Study 1: N = 118, 73% female, mean age 20.98 years; Study 2: N = 830, 49% female, mean age 38.04 years) sleep over the last month was self-reported. Confidence in interoceptive accuracy, which is the precision with which a person can monitor visceral signals, was measured using the Interoceptive Accuracy Scale, while interoceptive attention, which is the dispositional tendency to attend to bodily signals, was measured using the Body Perception Questionnaire. Study 1 revealed a relationship between long sleep latency and low confidence in interoceptive accuracy (β = -0.222, p = 0.021) and poor sleep quality and less interoceptive attention (β = -0.226, p = 0.016). Study 2 replicated these results as well as made clear a more general pattern whereby poor sleep-characterised by short duration, poor quality, less efficiency, long latency, and more frequent nighttime awakenings-related to an interoceptive phenotype of less confidence in interoceptive accuracy and more interoceptive attention (all β ≥ 0.047, p ≤ 0.17). In conclusion, results from these two independent studies provide robust cross-sectional evidence for associations between various dimensions of poor sleep and greater interoceptive attention, but less confidence in interoceptive accuracy.

Exploratory analyses of sleep intraindividual variability and fatigue in parents of children on the autism spectrum

Fatigue is associated with numerous harmful physical and mental health outcomes. Despite the established relationship between sleep and fatigue, research examining sleep variability within a person (i.e. intraindividual variability; IIV) and fatigue is limited. In addition, the associations between child and parent sleep regarding parent fatigue have not been explicitly explored, which could be relevant for parents of autistic children with increased sleep disturbance likelihood. The current study used two weeks of objective sleep (actigraphy) and subjective fatigue data from 81 parents and their children to explore associations among child sleep IIV, parent sleep IIV, and parent average daily fatigue, including evaluating evidence for mediation. Sleep IIV was estimated using a validated Bayesian model. Linear regression analyses indicated that greater parent total sleep time IIV predicted significantly higher fatigue levels. Child sleep IIV was unrelated to parent sleep IIV and fatigue, unsupportive of hypothesized mediation. Similarly, post hoc analyses examining child sleep averages, parent total sleep time IIV, and average parent fatigue were insignificant. Findings cautiously support the uniqueness of total sleep time IIV within parental sleep's relationship with fatigue, independent of child sleep. Objective sleep IIV should continue to be examined in addition to average levels.Lay abstractFatigue is associated with numerous harmful physical and mental health outcomes. Despite research indicating a relationship between fatigue and sleep, there has been a limited focus on how the variability of a person's sleep may be associated with fatigue. In addition, previous studies have not explicitly explored relationships among child sleep, parent sleep, and parent fatigue. Increasing knowledge about this area of research could be particularly relevant for families with autistic children with an increased likelihood of sleep disturbances. The current study used two weeks of objective sleep (actigraphy) data and subjective ratings of parent fatigue from 81 parents and their autistic children to examine associations among child and parent within-person sleep variability regarding average parent fatigue levels. Evidence was assessed for the role of parent sleep variability in hypothesized connections between child sleep variability and parent fatigue. We found that only greater variability in parents' total sleep time was associated with higher levels of parents' average daily fatigue rating over the two weeks. Child sleep variability was not significantly associated with parent sleep variability or average daily fatigue. In addition, average levels of child sleep were unrelated to parent total sleep time variability and fatigue. Although cautious interpretation is required, findings support the idea that variability in total sleep time may be a unique aspect of parental sleep's association with fatigue, independent of child sleep. In addition, sleep variability could be important to consider when examining sleep in addition to average levels of parameters like total sleep time.

Unlocking Mysteries: Exploring the Dynamic Interplay among Sleep, the Immune System, and Curcumin in Contemporary Research

The scientific disciplines encompassing sleep, the immune system, and curcumin have garnered considerable interest due to their interconnectedness and potential implications for human health. Sleep is a crucial factor in maintaining optimal immune function, as it facilitates the release of cytokines, which are signaling molecules responsible for regulating immune responses. On the contrary, sleep deprivation has the potential of inhibiting immune function, thereby heightening the susceptibility to infection and disease. Curcumin, a naturally occurring polyphenol derived from the turmeric plant, has been observed to possess immunomodulatory characteristics through its ability to modulate the equilibrium between pro- and anti-inflammatory cytokines. It is worth noting that there is evidence suggesting that curcumin supplementation could enhance the quality of sleep. Scientific studies have indicated that curcumin supplementation has been associated with an increase in the duration of sleep and a decrease in wakefulness among individuals who are in good health. Additionally, curcumin supplementation has been found to enhance sleep quality and alleviate symptoms of depression in individuals diagnosed with major depressive disorder. The intricate interplay among sleep, the immune system, and curcumin is multifaceted, and scientific investigations indicate that curcumin may serve as a beneficial dietary adjunct to enhance immune function and optimize sleep quality. Nevertheless, additional investigation is required to fully comprehend the mechanisms through which curcumin alters the immune system and enhances sleep, as well as to ascertain the most effective dose and timing of curcumin supplementation.

Time-Dependent Regulation of Sleep-Wakefulness and Electroencephalographic Characteristics by Spontaneous Running in Male Mice

The relationship between physical activity and sleep quality is a critical area of investigation, given the importance of both behaviours for health and disease. Despite the common use of running wheels to assess circadian rhythms and exercise, their impact on sleep has not been thoroughly explored. Here, we present a detailed analysis of how voluntary running affected sleep/wakefulness duration, architecture and electrophysiological characteristics in mice. Sequential electroencephalogram (EEG) assessments revealed that voluntary running elicits a progressive alteration in sleep/wake configurations, including a reduction in overall daily sleep time and an enhancement in sleep/wakefulness consolidation. These modifications exhibited a temporal association with the intensity of running activities. The observed changes in sleep/wakefulness duration and architecture partially persist even after the discontinuation of running. Spontaneous running also gradually changed the amplitude and/or frequency of EEG theta power not only during the running phase but also in rapid eye movement sleep (REMS). In vivo endoscopic calcium imaging in freely behaving mice revealed that running and REMS were accompanied by the activation of largely shared yet distinctive neuronal cohorts within the hippocampal CA1 region, concomitant with EEG theta oscillations during both behaviours. These findings highlight the dynamic nature of sleep/wakefulness regulation in response to voluntary exercise and suggest that physical activity played a pivotal role in modulating sleep need and the daily balance between sleep and wakefulness.

Mapping the Neural Basis of Wake Onset Regularity and Its Effects on Sleep Quality and Positive Affect

The regularity of sleep-wake cycles is a defining characteristic of normative sleep patterns that are typically associated with proper circadian rhythmicity. The previous literature indicates that consistent patterns of sleep and wake are associated with improved sleep quality and cognitive functioning. Conversely, sleep irregularity has been associated with reduced well-being and inefficiency in resting-state neural networks. This study investigated the relationship between specific sleep regularity measures and outcomes, including emotional affect, sleep quality, and resting-state functional connectivity. We found that variability in wake onset predicted poorer sleep quality and reduced positive affect. Furthermore, sleep regularity measures were associated with altered functional connectivity between the posterior cingulate cortex and regions involved in emotional processing. We propose that alterations in default mode network (DMN) connectivity linked to sleep irregularity reflect disruptions in emotional processing and sleep quality.

Investigating the impact of electroconvulsive therapy on brain networks and sleep: an observational study protocol

INTRODUCTION

Electroconvulsive therapy (ECT) is a highly effective treatment for refractory depression, but it may also cause cognitive side effects. Despite decades of use, the mechanisms by which ECT exerts both its antidepressant and cognitive effects are still poorly understood, with the latter substantially limiting referral and adherence to therapy. ECT induces changes in correlated neural activity-functional connectivity-across various brain networks, which may underlie both its clinical efficacy and associated cognitive side effects. Electroencephalography (EEG) could address these knowledge gaps by identifying biomarkers that predict therapeutic outcomes or cognitive side effects. Such developments could ultimately improve patient selection and adherence. Such markers likely span large-scale functional brain networks or temporal dynamics of brain activity during sleep. We hypothesise that enhancement in slow wave sleep mediates the relationship between antidepressant effects and changes in functional connectivity throughout the course of ECT.

METHODS AND ANALYSIS

Disruptions of Brain Networks and Sleep by Electroconvulsive Therapy (DNS-ECT) is an ongoing observational study investigating the impact of ECT on large-scale brain functional networks and their relationships to sleep slow waves, an EEG marker linked to synaptic plasticity. The novelty of this study stems from our focus on the assessment of EEG markers during sleep, wakefulness and ECT-induced seizures over the course of therapy. Graph-based network analyses of high-density EEG signals allow characterisation of functional networks locally in specific subnetworks and globally over large-scale functional networks. Longitudinal assessments of EEG alongside clinical and cognitive outcomes provide a unique opportunity to improve our understanding of the circuit mechanisms underlying the development of cognitive impairments and antidepressant effects incurred during ECT.

ETHICS AND DISSEMINATION

Recruitment for this 5-year study started in March 2023. Dissemination plans include presentations at scientific conferences and peer-reviewed publications. This study has been registered with ClinicalTrials.gov registry under identifier.

TRIAL REGISTRATION NUMBER

NCT05905705.

Supplementation of essential amino acids suppresses age-associated sleep loss and sleep fragmentation but not loss of rhythm strength under yeast-restricted malnutrition in Drosophila

Sleep quality and quantity decrease with age, and sleep disturbance increases the risk of many age-associated diseases. There is a significant relationship between nutritional status and sleep outcomes, with malnutrition inducing poor sleep quality in older adults. However, it remains elusive whether, and if so how, nutritional supplementation prevents age-associated sleep problems. Here, we utilized Drosophila to investigate the effects of a malnutrition diet with restricted yeast, a primary protein source, and supplementation of 10 essential amino acids (EAAs) on sleep profiles during ageing. Compared with the standard diet containing 2.7% yeast, the malnutrition diet containing 0.27% yeast significantly decreased target of rapamycin (TOR) signalling and shortened the lifespan of male Canton-S flies. By contrast, age-associated sleep loss, sleep fragmentation and loss of rhythm strength were similarly observed under both diets. Supplementation of the malnutrition diet with EAAs in restricted yeast significantly ameliorated age-associated sleep loss and sleep fragmentation without altering loss of rhythm strength. It also rescued decreased TOR signalling activity but not the shortened lifespan, suggesting that the effects of EAAs on sleep integrity are independent of TOR activity and lifespan regulation. These results may help to develop dietary interventions that improve age-related sleep problems in humans.

Simultaneous activation of different subtypes of dopamine receptors may lead to activation of homeostatic sleep regulatory mechanisms

Dopaminergic system gains importance in homeostatic sleep regulation, but the role of different dopamine receptors is not well-defined. 72 h rat electrocorticogram and sleep recordings were made after single application of dopaminergic drugs in clinical use or at least underwent clinical trials. The non-selective agonist apomorphine evoked short pharmacological sleep deprivation with intense wakefulness followed by pronounced sleep rebound. D2 agonist bromocriptine induced moderate and extended increase in wakefulness without a homeostatic sleep replacement but downregulated slow wave sleep need for 72 h. Selective D1 agonist SKF-38393 failed to induce enhanced waking sufficient for sleep replacement. High-dose D2 antagonism by sulpiride temporarily enhanced wakefulness. All drugs evoked extended (72 h) sleep changes after single application. Opposite sleep changes could be seen after the application of different doses in case of both bromocriptine and sulpiride. Theta, beta and gamma power reflected intensity differences in drug-induced wakefulness stages. Apomorphine- and high sulpiride dose-induced waking showed elevated power in all three frequency bands. Bromocriptine-induced wakefulness dominated by beta activity. Enhancement of more, than one type of electrocorticogram activities during wakefulness was a prerequisite for the activation of sleep homeostasis. According to present data, D1- or D2-like receptor agonism are not separately involved in the homeostatic regulation of slow wave sleep. Simultaneous and non-selective agonism on DA receptors is the most effective way to elicit intense W, which is followed by slow wave sleep rebound. REM sleep rebound could be evoked by D2 agonism. Rebound indicates the activation of homeostatic sleep regulation, but with unknown exact mechanisms.

Topical review: sleep regulation as a novel target for treating preschool-aged children with attention-deficit/hyperactivity disorder symptoms

OBJECTIVE

Elevated attention-deficit/hyperactivity disorder (ADHD) symptoms in preschoolers are a risk factor for poorer psychiatric health, cognitive deficits, and social and academic impairment across the lifespan. The first-line treatment for these preschoolers, behavioral parent training (BPT), reduces children's disruptive behaviors and parenting stress, yet its impact on core ADHD symptoms is inconsistent. Early interventions targeting biological mechanisms linked to core ADHD pathophysiology are critically needed.

METHODS

This topical review explores sleep dysregulation as a potential key target for early intervention for ADHD symptoms among preschoolers.

RESULTS

Sleep dysregulation is common in school-aged children with ADHD, and treating sleep improves core ADHD symptoms in older children. Cross-sectional and prospective research with preschoolers offers compelling evidence that sleep dysregulation and ADHD symptoms are closely linked over the course of early development. BPT and behavioral sleep medicine (BSM) interventions share an underlying theoretical framework and could be streamlined to target sleep in addition to daytime behaviors.

CONCLUSIONS

Novel early interventions targeting underlying biological mechanisms linked to core ADHD pathophysiology are critically needed to improve the trajectories of ADHD symptoms, comorbidity, and functional deficits for preschoolers with elevated ADHD symptoms. Sleep regulation is a promising mechanistic treatment target for this population, and future interventions may draw from the shared behavioral principles of BPT and BSM to target behaviors across the 24-hr period and employ scalable formats to optimize the number of families who can benefit from parent-based interventions targeting ADHD symptoms and sleep in early development.

Evolution of canonical circadian clock genes underlies unique sleep strategies of marine mammals for secondary aquatic adaptation

To satisfy the needs of sleeping underwater, marine mammals, including cetaceans, sirenians, and pinnipeds, have evolved an unusual form of sleep, known as unihemispheric slow-wave sleep (USWS), in which one brain hemisphere is asleep while the other is awake. All aquatic cetaceans have only evolved USWS without rapid eye movement (REM) sleep, whereas aquatic sirenians and amphibious pinnipeds display both bihemispheric slow-wave sleep (BSWS) and USWS, as well as REM sleep. However, the molecular genetic changes underlying USWS remain unknown. The present study investigated the evolution of eight canonical circadian genes and found that positive selection occurred mainly within cetacean lineages. Furthermore, convergent evolution was observed in lineages with USWS at three circadian clock genes. Remarkably, in vitro assays showed that cetacean-specific mutations increased the nuclear localization of zebrafish clocka, and enhanced the transcriptional activation activity of Clocka and Bmal1a. In vivo, transcriptome analysis showed that the overexpression of the cetacean-specific mutant clocka (clocka-mut) caused the upregulation of the wakefulness-promoting glutamatergic genes and the differential expression of multiple genes associated with sleep regulation. In contrast, the GABAergic and cholinergic pathways, which play important roles in promoting sleep, were downregulated in the bmal1a-mut-overexpressing zebrafish. Concordantly, sleep time of zebrafish overexpressing clocka-mut and bmal1a-mut were significantly less than the zebrafish overexpressing the wild-type genes, respectively. These findings support our hypothesis that canonical circadian clock genes may have evolved adaptively to enhance circadian regulation ability relating to sleep in cetaceans and, in turn, contribute to the formation of USWS.

Habitual caffeine intake, genetics and cognitive performance

BACKGROUND

Research on caffeine and cognitive performance remains controversial. Variations in genes associated with caffeine metabolism and response such as CYP1A2, AHR and ADORA2A may account for variable findings.

AIM

To investigate caffeine × gene interactions on cognitive performance in all key domains of cognition in healthy individuals.

METHODS

Participants completed a lifestyle and food frequency questionnaire and a cognitive test battery including validated tasks to assess the domains of social cognition, memory, attention and executive function. Genotyping was performed for AHR rs6968554, CYP1A2 rs2472297, ADORA2A rs5751876, ADA rs73598374 and APOE rs429358 and rs7412.

RESULTS

Significant gene × caffeine interactions were observed for the domains of social cognition, (F2, 123 = 5.848, p = 0.004) and executive function (F2, 109 = 3.690, p = 0.028). 'Slow' metabolisers had a higher performance in social cognition compared with 'fast' metabolisers among high-caffeine consumers (p = 0.004), while 'fast' metabolisers had a higher performance in executive function compared with 'slow' metabolisers among moderate caffeine consumers (p = 0.002).

CONCLUSIONS

The present findings suggest an association between genetic caffeine metabolism, habitual caffeine intake and cognitive function in the domains of social cognition and executive function. More research in naturalistic environments using larger cohorts is needed to confirm these findings to add to our understanding of how habitual caffeine may influence cognitive function based on individual genotype.

Suprachiasmatic Neuromedin-S Neurons Regulate Arousal

Mammalian circadian rhythms, which orchestrate the daily temporal structure of biological processes, including the sleep-wake cycle, are primarily regulated by the circadian clock in the hypothalamic suprachiasmatic nucleus (SCN). The SCN clock is also implicated in providing an arousal 'signal,' particularly during the wake-maintenance zone (WMZ) of our biological day, essential for sustaining normal levels of wakefulness in the presence of mounting sleep pressure. Here we identify a role for SCN Neuromedin-S (SCN NMS ) neurons in regulating the level of arousal, especially during the WMZ. We used chemogenetic and optogenetic methods to activate SCN NMS neurons in vivo, which potently drove wakefulness. Fiber photometry confirmed the wake-active profile of SCN NM neurons. Genetically ablating SCN NMS neurons disrupted the sleep-wake cycle, reducing wakefulness during the dark period and abolished the circadian rhythm of body temperature. SCN NMS neurons target the dorsomedial hypothalamic nucleus (DMH), and photostimulation of their terminals within the DMH rapidly produces arousal from sleep. Pre-synaptic inputs to SCN NMS neurons were also identified, including regions known to influence SCN clock regulation. Unexpectedly, we discovered strong input from the preoptic area (POA), which itself receives substantial inhibitory input from the DMH, forming a possible arousal-promoting circuit (SCN->DMH->POA->SCN). Finally, we analyzed the transcriptional profile of SCN NMS neurons via single-nuclei RNA-Seq, revealing three distinct subtypes. Our findings link molecularly-defined SCN neurons to sleep-wake patterns, body temperature rhythms, and arousal control.

Significance Statement

Our study's findings provide a cellular and neurobiological understanding of how Neuromedin-S (NMS)-containing SCN neurons contribute to regulating circadian rhythms, sleep-wake patterns, body temperature, and arousal control in mammals. This research illuminates the circuit, cellular, and synaptic mechanisms through which SCN neurons regulate daily cycles of wakefulness and sleep, with implications for understanding and potentially manipulating these processes in health and disease.

Sleep need driven oscillation of glutamate synaptic phenotype

Sleep loss increases AMPA-synaptic strength and number in the neocortex. However, this is only part of the synaptic sleep loss response. We report an increased AMPA/NMDA EPSC ratio in frontal-cortical pyramidal neurons of layers 2-3. Silent synapses are absent, decreasing the plastic potential to convert silent NMDA to active AMPA synapses. These sleep loss changes are recovered by sleep. Sleep genes are enriched for synaptic shaping cellular components controlling glutamate synapse phenotype, overlap with autism risk genes, and are primarily observed in excitatory pyramidal neurons projecting intra-telencephalically. These genes are enriched with genes controlled by the transcription factor, MEF2c, and its repressor, HDAC4. Sleep genes can thus provide a framework within which motor learning and training occur mediated by the sleep-dependent oscillation of glutamate-synaptic phenotypes.

Variations of autonomic arousal mediate the reportability of mind blanking occurrences

Mind blanking (MB) is the inability to report mental events during unconstraint thinking. Previous work shows that MB is linked to decreased levels of cortical arousal, indicating dominance of cerebral mechanisms when reporting mental states. What remains inconclusive is whether MB can also ensue from autonomic arousal manipulations, pointing to the implication of peripheral physiology to mental events. Using experience sampling, neural, and physiological measurements in 26 participants, we first show that MB was reported more frequently in low arousal conditions, elicited by sleep deprivation. Also, there was partial evidence for a higher occurence of MB reports in high arousal conditions, elicited by intense physical exercise. Transition probabilities revealed that, after sleep deprivation, mind wandering was more likely to be followed by MB and less likely to be followed by more mind wandering reports. Using classification schemes, we found higher performance of a balanced random forest classifier trained on both neural and physiological markers in comparison to performance when solely neural or physiological were used. Collectively, we show that both cortical and autonomic arousal affect MB report occurrences. Our results establish that MB is supported by combined brain-body configurations, and, by linking mental and physiological states, they pave the way for novel embodied accounts of spontaneous thinking.'The stage 1 protocol for this Registered Report was accepted in principle on 02/01/23. The protocol, as accepted by the journal, can be found at: 10.17605/OSF.IO/SH2YE' Techniques: Life sciences techniques, Biophysical methods [Electrocardiography - EKG]; Life sciences techniques, Biophysical methods [Electroencephalography - EEG]; CTS received date: 27.11.2024.

Perinatal Photoperiod Has Long-Term Effects on the Rest-Activity Cycle and Sleep in Male and Female Mice

Environmental light conditions during development can have long-lasting effects on the physiology and behavior of an animal. Photoperiod, a clear example of environmental light conditions, is detected by and coded in the suprachiasmatic nucleus. It is therefore possible that differences observed in behavior in adulthood after exposure to different perinatal photoperiods are caused by lasting changes in the suprachiasmatic nucleus or alternatively, in other nuclei affected by perinatal photoperiod. It can then be expected that behavior with strong circadian aspects, like rest-activity and sleep, are affected by difference in photoperiod during development as well. To investigate this further, we exposed mice to different photoperiods during their development in the womb until weaning (long: 16 h of light, 8 h of darkness; short: 8 h of light, 16 h of darkness). After weaning, the animals were exposed to a 12 h:12 h light:dark cycle for at least 3 more weeks and some animals were subsequently exposed to constant darkness. We assessed their rest-activity patterns by recording voluntary locomotor activity and used EEG recordings to determine sleep architecture and electroencephalographic spectral density. Perinatal long photoperiod animals showed a shorter duration of locomotor activity than short photoperiod-developed mice in a 12:12 light-dark cycle. This difference disappeared in constant darkness. In the light phase, that is, during the day, perinatal long photoperiod mice spent less time awake and more time in NREM sleep than short photoperiod-developed mice. No effects of perinatal photoperiod were observed in the EEG spectral density or in response to sleep deprivation. We see lasting differences in behavioral locomotor activity and sleep in female and male mice after exposure to different perinatal photoperiods. We conclude that perinatal photoperiod programs a developing mammal for different external conditions and changes brain physiology, which in turn results in long-lasting, possibly even permanent, changes in the sleep and locomotor activity.

Prolactin in sleep and EEG regulation: New mechanisms and sleep-related brain targets complement classical data

The role of prolactin in sleep regulation has been the subject of extensive research over the past 50 years, resulting in the identification of multiple, disparate functions for the hormone. Prolactin demonstrated a characteristic circadian release pattern with elevation during dark and diminution during light. High prolactin levels were linked to non-rapid eye movement sleep and electroencephalogram delta activity in humans. Conversely, hyperprolactinemia showed strong correlation with REM sleep in rodent studies. Prolactin may be implicated in the alterations in female sleep patterns observed during the reproductive cycle, it may play a role in the REM sleep enhancement following stress and in sleep-related immunological processes. In conclusion, prolactin appears to have a sleep-promoting role, particularly during the dark phase. However, it does not appear to play a central and coherent role in sleep regulation, as observed in some neuropeptides such as orexin. Conversely, its principal function may be to facilitate situational, yet adaptive, changes in sleep patterns in response to challenging physiological phases, such as those associated with stress, immunological challenges, or the reproductive cycle. Neuronal substrates for prolactin-mediated sleep effects remain unknown; however, recent rodent sleep studies may provide insights into the potential sites of these effects.

Novel applications of sleep pharmacology as delirium therapeutics

Sleep-wake and circadian disruption (SCD) is a core feature of delirium. It has been hypothesized that SCD contributes to delirium pathogenesis; therefore, interventions that prevent or reverse SCD represent an array of promising opportunities in relation to delirium. This review explores the relationship between sleep-wake/circadian physiology and delirium pathophysiology with a focus on neurotransmitter systems. Across potential targets aimed at preventing or treating delirium, three broad approaches are considered: 1. Pharmacological mechanisms that contribute to physiological sleep may preserve or restore next-day cognition in patients with or at risk for delirium (e.g., alpha 2 agonists, dopamine 2 antagonists, serotonin 2 A antagonists, dual orexin receptor antagonists, or GHB agonists); 2. Pharmacological mechanisms that promote wakefulness during the day may combat hypoactive delirium (e.g., adenosine 2 A antagonists, dopamine transporter antagonists, orexin agonists, histamine 3 antagonists); and 3. Melatonergic and other circadian interventions could strengthen the phase or amplitude of circadian rhythms and ensure appropriately entrained timing in patients with or at risk for delirium (e.g., as informed by a person's preexisting circadian phase).

Chronic short sleep duration lengthens reaction time, but the deficit is not associated with motor preparation

The purpose of this study was to investigate the association between chronic sleep duration and reaction time performance and motor preparation during a simple reaction time task with a startling acoustic stimulus in adults. This cross-sectional study included self-reported short sleepers (n = 25, ≤ 6 hr per night) and adequate sleepers (n = 25, ≥ 7.5 hr per night) who performed a simple reaction time task requiring a targeted ballistic wrist extension in response to either a control-tone (80 dB) or a startling acoustic stimulus (120 dB). Outcome measures included reaction times for each stimulus (overall and for each trial block), lapses, and proportion of startle responses. Chronic short sleepers slept on average 5.7 hr per night in the previous month, which was 2.8 hr per night less than the adequate sleepers. Results revealed an interaction between sleep duration group and stimulus type; the short sleepers had significantly slower control-tone reaction times compared with adequate sleepers, but there was no significant difference in reaction time between groups for the startling acoustic stimulus. Further investigation showed that chronic short sleepers had significantly slower control-tone reaction times after two blocks of trials lasting about 5 min, until the end of the task. Lapses were not significantly different between groups. Chronic short sleep duration was associated with poorer performance; however, these reaction time deficits cannot be attributed to motor preparation, as startling acoustic stimulus reaction times were not different between sleep duration groups. While time-on-task performance decrements were associated with chronic sleep duration, alertness was not. Sleeping less than the recommended sleep duration on a regular basis is associated with poorer cognitive performance, which becomes evident after 5 min.

Circadian realignment and depressed mood: A systematic review

Chronotherapeutic interventions aimed at realigning the circadian system can improve depression. This systematic review evaluated the current evidence for circadian realignment as an antidepressant mechanism. A comprehensive search was conducted in studies that implemented a chronotherapeutic intervention in samples with depression and/or delayed sleep/circadian timing using PubMed, EMBASE, Cochrane Central Register of Controlled Trials (Wiley), Europe PMC, and PsycINFO. The Downs and Black checklist was used to evaluate study quality. There were 58 studies included, of which 23 studies reported the association between realignment and depression. Circadian realignment was associated with improved depression in studies that included participants with baseline delays and elevated depression. Randomized clinical trials measuring circadian phase markers are needed to further elucidate circadian realignment as an antidepressant mechanism.

Irregular sleep/wake patterns in student-athletes exposed to early morning training

This study aimed to examine the sleep parameters and sleep/wake regularity of a cohort of student-athletes who start training between 06:30 and 07:00. Twenty-one male Rugby Union players, aged 21 ± 2 years and competing at a national level, were assessed using actigraphy over two weeks, and the Athlete Sleep Screening Questionnaire (ASSQ). Sleep/wake regularity was calculated using the Sleep Regularity Index (SRI). Wilcoxon signed-rank tests showed that nocturnal sleep preceding morning training had a significantly shorter sleep duration (1.8 hr, r = .67), and advanced sleep onset (0.9 hr, r = .50) and sleep offset times (3.2 hr, r = .85) compared to nocturnal sleep preceding free days. The variability of training demands resulted in an inconsistent sleep pattern between consecutive days, resulting in a median SRI score of 67.0 (interquartile range: 17.0). Pearson correlations revealed that lower SRI was significantly associated with a higher daily sleep duration including naps (r = -.62), delayed sleep onset (r = -.50) and sleep offset (r = -.60), and a later chronotype assessed using the ASSQ (r = .52). These findings indicate that early morning training is a factor contributing to irregular sleep/wake patterns in student-athletes, and where feasible should be scheduled at an alternative time.

The influence of transcranial alternating current stimulation on EEG spectral power during subsequent sleep: A randomized crossover study

OBJECTIVE

To evaluate the instant impact of transcranial alternating current stimulation (tACS) on sleep brain oscillations.

METHODS

Thirty-six healthy subjects were randomly assigned to receive tACS and sham stimulation in a crossover design separated by a one-week washout period. After stimulation, a 2-h nap polysomnography (PSG) was performed to obtain Electroencephalogram (EEG) data and objective sleep variables, and self-reported subjective sleep parameters were collected at the end of the nap. EEG spectral analyses were conducted on the EEG data to obtain the absolute and relative power for each sleep stage during the nap. The associations between power values and objective and subjective measurements were analyzed using Spearman or Pearson correlation coefficients.

RESULTS

The tACS group presented higher power in slow wave activity (SWA) and delta frequency bands and lower alpha, sigma and beta power values compared to the sham group during the N2 and N3 sleep stages. SWA and delta power were positively associated with sleep duration and sleep efficiency relevant parameters; while alpha, sigma and beta power were positively associated with prolonged sleep latency and wakefulness related variables. PSG, self-reported and sleep diary measured objective and subjective sleep parameters were comparable between the tACS and the sham groups.

CONCLUSION

Our results support that tACS could promote sleep depth in microstructure of sleep EEG, manifesting as an increase in EEG spectral power in low frequency bands and a decrease in high frequency bands. The registration number of this study is ChiCTR2200063729.

Novel psychotherapies for insomnia

Insomnia disorder, characterized by a complaint of reduced sleep quality or quantity and associated daytime impairment, is highly prevalent and associated with reduced quality of life and productivity. Cognitive behavioural therapy for insomnia (CBT-I) is the current first-line treatment for chronic insomnia disorder. Here, we outline our perspective for the future optimization of psychotherapeutic treatment for insomnia. We identified the following areas as the most promising: first, optimizing efficacy of the CBT-I protocol; second, developing diagnostic and therapeutic approaches for non-responders and partial responders; and third, advancing widespread implementation of psychotherapy for insomnia. More specifically, we outline how the current CBT-I protocol could be optimized through an improved understanding of treatment mechanisms, and discuss the potential of adaptive treatment strategies. Another promising approach for improving the current CBT-I protocol is using add-ons such as physical exercise or circadian-based interventions. Both may be promising in certain subgroups of patients with insomnia. In terms of non-response, we identify acceptance and commitment therapy for insomnia (ACT-I) as a promising treatment for non-responders to CBT-I. ACT-I, however, still needs to be evaluated in actual non-responders to CBT-I. Implementing CBT-I in clinical practice is still one of the major challenges at hand. We outline how brief treatment, targeted treatment for challenging patient groups, and digital treatment may help improve implementation. For a future research agenda, we suggest that further research into treatment mechanisms, randomized-controlled trials in non-responders to CBT-I, and a focus on implementation science have a potential to bring the field forward.

Calcineurin governs baseline and homeostatic regulations of non-rapid eye movement sleep in mice

Sleep need accumulates during waking and dissipates during sleep to maintain sleep homeostasis (process S). Besides the regulation of daily (baseline) sleep amount, homeostatic sleep regulation commonly refers to the universal phenomenon that sleep deprivation (SD) causes an increase of sleep need, hence, the amount and intensity of subsequent recovery sleep. The central regulators and signaling pathways that govern the baseline and homeostatic sleep regulations in mammals remain unclear. Here, we report that enhanced activity of calcineurin Aα (CNAα)-a catalytic subunit of calcineurin-in the mouse brain neurons sharply increases the amount (to ~17-h/d) and delta power-a measure of intensity-of non-rapid eye movement sleep (NREMS). Knockout of the regulatory (CnB1) or catalytic (CnAα and CnAβ) subunits of calcineurin diminishes the amount (to ~4-h/d) and delta power of baseline NREMS, but also nearly abrogates the homeostatic recovery NREMS following SD. Accordingly, mathematical modeling of process S reveals an inability to accumulate sleep need during spontaneous or forced wakefulness in calcineurin deficient mice. Moreover, calcineurin promotes baseline NREMS by antagonizing wake-promoting protein kinase A and, in part, by activating sleep-promoting kinase SIK3. Together, these results indicate that calcineurin is an important regulator of sleep need and governs both baseline and homeostatic regulations of NREMS in mice.

A carnitine transporter at the blood-brain barrier modulates sleep via glial lipid metabolism in Drosophila

To regulate brain function, peripheral compounds must traverse the blood-brain barrier (BBB), an interface between the brain and the circulatory system. To determine whether specific transport mechanisms are relevant for sleep, we conducted a BBB-specific inducible RNAi knockdown (iKD) screen for genes affecting sleep in Drosophila. We observed reduced sleep with knockdown of solute carrier CG6126, a carnitine transporter, as determined by isotope flux. Our findings suggest that CG6126 regulation of sleep is through the role of the carnitine shuttle in regulating fatty acid metabolism as lipid droplets accumulate in the brains of CG6126 BBB iKD flies. Knocking down mitochondrial carnitine transferases in non-BBB glial cells mimicked the reduced sleep of the CG6126 BBB iKD flies, while bypassing the necessity of carnitine transport with dietary medium-chain fatty acids or palmitoylcarnitine rescued sleep. We propose that carnitine transport via CG6126 promotes brain fatty acid metabolism necessary for maintaining sleep.

Spontaneous oxycodone withdrawal disrupts sleep, diurnal, and electrophysiological dynamics in rats

Opioid dependence is defined by an aversive withdrawal syndrome upon drug cessation that can motivate continued drug-taking, development of opioid use disorder, and precipitate relapse. An understudied but common opioid withdrawal symptom is disrupted sleep, reported as both insomnia and daytime sleepiness. Despite the prevalence and severity of sleep disturbances during opioid withdrawal, there is a gap in our understanding of their interactions. The goal of this study was to establish an in-depth, temporal signature of spontaneous oxycodone withdrawal effects on the diurnal composition of discrete sleep stages and the dynamic spectral properties of the electroencephalogram (EEG) signal in male rats. We continuously recorded EEG and electromyography (EMG) signals for 8 d of spontaneous withdrawal after a 14-d escalating-dose oxycodone regimen (0.5-8.0 mg/kg, 2×d; SC). During withdrawal, there was a profound loss (peaking on days 2-3) and gradual return of diurnal structure in sleep, body temperature, and locomotor activity, as well as decreased sleep and wake bout durations dependent on lights on/off. Withdrawal was associated with significant alterations in the slope of the aperiodic 1/f component of the EEG power spectrum, an established biomarker of arousal level. Early in withdrawal, NREM exhibited an acute flattening and return to baseline of both low (1-4 Hz) and high (15-50 Hz) frequency components of the 1/f spectrum. These findings suggest temporally dependent withdrawal effects on sleep, reflecting the complex way in which the allostatic forces of opioid withdrawal impinge upon sleep and diurnal processes. These foundational data based on continuous tracking of vigilance state, sleep stage composition, and spectral EEG properties provide a detailed construct with which to form and test hypotheses on the mechanisms of opioid-sleep interactions.