The two-process model of sleep regulation: a reappraisal

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.

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.

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.

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.

Activation of locus coeruleus noradrenergic neurons rapidly drives homeostatic sleep pressure

Homeostatic sleep regulation is essential for optimizing the amount and timing of sleep for its revitalizing function, but the mechanism underlying sleep homeostasis remains poorly understood. Here, we show that optogenetic activation of locus coeruleus (LC) noradrenergic neurons immediately increased sleep propensity following a transient wakefulness, contrasting with many other arousal-promoting neurons whose activation induces sustained wakefulness. Fiber photometry showed that repeated optogenetic or sensory stimulation caused a rapid reduction of calcium activity in LC neurons and steep declines in noradrenaline/norepinephrine (NE) release in both the LC and medial prefrontal cortex (mPFC). Knockdown of α2A adrenergic receptors in LC neurons mitigated the decline of NE release induced by repetitive stimulation and extended wakefulness, demonstrating an important role of α2A receptor-mediated auto-suppression of NE release. Together, these results suggest that functional fatigue of LC noradrenergic neurons, which reduces their wake-promoting capacity, contributes to sleep pressure.

Calcineurin: An essential regulator of sleep revealed by biochemical, chemical biological, and genetic approaches

Research into mechanisms underlying sleep traditionally relies on electrophysiology and genetics. Because sleep can only be measured on whole animals by behavioral observations and physical means, no sleep research was initiated by biochemical and chemical biological approaches. We used phosphorylation sites of kinases important for sleep as targets for biochemical and chemical biological approaches. Sleep was increased in mice carrying a threonine-to-alanine substitution at residue T469 of salt-inducible kinase 3 (SIK3). Our biochemical purification and photo-crosslinking revealed calcineurin (CaN) dephosphorylation, both in vitro and in vivo, of SIK3 at T469 and S551, but not T221. Knocking down CaN regulatory subunit reduced daily sleep by more than 5 h, exceeding all known mouse mutants. Our work uncovered a critical physiological role for CaN in sleep and pioneered biochemical purification and chemical biology as effective approaches to study sleep.

Association of self-monitoring performance of cognitive performance with personal diurnal preference when sleep-deprived

In modern society, many workers struggle with sleep deprivation due to their work schedules and excessive workloads. Accurate self-awareness and self-monitoring abilities are crucial for workers to adopt risk-coping strategies and protective behaviors when fatigued. The current study examined the relationship between chronotypes and self-monitoring performance during 24 h of sleep deprivation. The study involved 26 male adults in a two-night experiment, and participants' diurnal preferences were evaluated using the Morningness-Eveningness Questionnaire (MEQ). Self-monitoring performance was calculated by comparing actual task performance with self-rated predicted or post-estimated performance in the psychomotor vigilance task (PVT) and Digit Symbol Substitution Task (DSST). The study found that task and self-monitoring performances in the PVT and DSST were maintained until around 4:00 h, after which they began to deteriorate. Individuals with a higher MEQ score, indicating a stronger tendency towards a morning type, showed inaccurate self-monitoring, particularly in the final quarter of the sleep deprivation experiment, due to overly optimistic predictions. However, only prediction accuracy and not post-estimation showed this correlation. This study highlights the importance of considering an individual's chronotype in workplace management, particularly in workplaces with irregular work timings, rotating shifts, and long working hours, to ensure better occupational safety.

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.

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.

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.

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.

Strategic naps in automated driving - Sleep architecture predicts sleep inertia better than nap duration

At higher levels of driving automation, drivers can nap during parts of the trip but must take over control in others. Awakening from a nap is marked by sleep inertia which is tackled by the NASA nap paradigm in aviation: Strategic on-flight naps are restricted to 40 min to avoid deep sleep and therefore sleep inertia. For future automated driving, there are currently no such strategies for addressing sleep inertia. Given the disparate requirements, it is uncertain whether the strategies derived from aviation can be readily applied to automated driving. Therefore, our study aimed to compare the effects of restricting the duration of nap opportunities following the NASA nap paradigm to the effects of sleep architecture on sleep inertia in takeover scenarios in automated driving. In our driving simulator study, 24 participants were invited to sleep during three automated drives. They were awakened after 20, 40, or 60 min and asked to manually complete an urban drive. We assessed how napping duration, last sleep stage before takeover, and varying proportions of light, stable, and deep sleep influenced self-reported sleepiness, takeover times, and the number of driving errors. Takeover times increased with nap duration, but sleepiness and driving errors did not. Instead, all measures were significantly influenced by sleep architecture. Sleepiness increased after awakening from light and stable sleep, and takeover times after awakening from light sleep. Takeover times also increased with higher proportions of stable sleep. The number of driving errors was significantly increased with the proportion of deep sleep and after awakenings from stable and deep sleep. These results suggest that sleep architecture, not nap duration, is crucial for predicting sleep inertia. Therefore, the NASA nap paradigm is not suitable for driving contexts. Future driver monitoring systems should assess the sleep architecture to predict and prevent sleep inertia.

Altered Rhythmicity, Depressive Ruminative Thinking and Suicidal Ideation as Possible Correlates of an Unrecognized Autism Spectrum in Patients with Borderline Personality Disorder

BACKGROUND/OBJECTIVES

Recent research has explored the presence of subthreshold autistic traits (ATs) in individuals with borderline personality disorder (BPD), suggesting that these traits may contribute to the severity of BPD symptoms and increase the risk of other mental health issues, including suicidal behaviors. This study aims to investigate the relationship between ATs and affective symptoms, such as mood instability and suicidality, in people diagnosed with BPD.

METHODS

A total of 48 subjects with BPD were assessed with self-report questionnaires including the Adult Autism Subthreshold Spectrum (AdAS Spectrum), the mood spectrum self-report version (MOODS-SR) and the ruminative response scale (RRS).

RESULTS

Subjects with significant ATs scored higher than BPD subjects in all domains and in the total score of AdAS Spectrum, RRS, and MOODS-SR, as well as in the items investigating suicidality. RRS total score, its depression domain, and the MOODS-SR rhythmicity domain, as well as suicidality, were predictors of the presence of ATs.

CONCLUSIONS

Our data confirm the relationship between the presence of clinically significant ATs and affective symptoms, ruminative thinking, and suicidality in patients with BPD.

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.

Novel biomarkers derived from the Maintenance of Wakefulness Test as predictors of sleepiness and response to treatment

The Maintenance of Wakefulness Test (MWT) is a widely accepted objective test used to evaluate daytime somnolence and is commonly used in clinical studies evaluating novel therapeutics for excessive daytime sleepiness. In the latter, sleep onset latency (SOL) is typically the sole MWT endpoint. Here, we explored microsleeps, sleep probability measures derived from automated sleep scoring, and quantitative electroencephalography (qEEG) features as additional MWT biomarkers of daytime sleepiness, using data from a phase 1B trial of the selective orexin receptor 2 agonist danavorexton (TAK-925) in people with narcolepsy type 1 (NT1) or type 2 (NT2). Danavorexton treatment reduced the rate and duration of microsleeps during the MWT in NT1 (days 1 and 7; p ≤ .005) and microsleep rate in NT2 (days 1 and 7; p < .0001). The use of an EEG-sleep-staging - derived measure to determine the probability of wakefulness for each minute revealed a novel metric to track changes in daytime sleepiness, which were consistent with the θ/α ratio, a known biomarker of drowsiness. The slopes of line-fits to both the log-transformed sleepiness score or log-transformed θ/α ratio correlated well to (inverse) MWT SOL for NT1 (R = 0.93 and R = 0.83, respectively) and NT2 (R = 0.97 and R = 0.84, respectively), suggesting that individuals with narcolepsy have increased sleepiness immediately after lights-off. These analyses demonstrate that novel EEG-based biomarkers can augment SOL as predictors of sleepiness and its response to treatment and provide a novel framework for the analysis of wake EEG in hypersomnia disorders.

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.

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.

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.

Melatonin's Impact on Cytokine Storm and Modulation of Purinergic Receptors for COVID-19 Prognosis: A Mental Health Perspective

In 2019, coronavirus disease 2019 (COVID-19) started a global health crisis and was associated with high rates of depression and anxiety. Both mental disorders and COVID-19 exhibit similarities in pathophysiology, characterized by immune system overactivation, involvement of the purinergic system, and oxidative stress, besides additional factors and systems likely contributing to the complexities of these conditions. The purinergic system contributes to the disease-influenced immune response, an essential strategy for controlling pathophysiological effects. In this context, the hormone melatonin emerges as a substance that can modulate the purinergic system and contribute positively to the pathophysiology of SARS-CoV-2 infection and associated mental disorders. Melatonin is a hormone that regulates the body's circadian rhythms, plays an essential role in regulating sleep and mood, and modulates the purinergic system. Recent studies suggest melatonin's anti-inflammatory and antioxidant properties may benefit COVID-19. This review explores melatonin's impact on inflammatory cytokine storm in COVID-19 through purinergic system modulation.

Sleep Deficiency in Adolescents: The School Start Time Debate

Adolescence is commonly accepted as a challenging time for sleep, with multiple factors contributing to sleep deficiency in adolescents. These include physiologic changes with shifts in their circadian rhythm; medical sleep disorders; and social, cultural, and environmental factors. Early school start times negatively affect sleep in adolescents as well, with poorer outcomes in their overall health, wellbeing, and performance. This article highlights the different contributing factors for sleep deficiency in adolescents and the consequences of sleep deficiency. In addition, the authors discuss the impact of delayed school start times in improving adolescents' sleep and overall function.

Is the Current Lights-Off Time in General Hospitals Too Early, Given People's Usual Bedtimes?

OBJECTIVE

This study aimed to investigate how shift-working nursing professionals perceive the current lights-off time in wards as early, appropriate, or late and how their perceptions can be influenced when considering people's usual bedtimes.

METHODS

An online survey was conducted comprising queries about the current lights-off time in wards and respondents' opinions, self-rated psychological status, and perceptions of the current lights-off time considering others' usual bedtimes. Psychological status was evaluated using the Insomnia Severity Index, the Patient Health Questionnaire-9, the Dysfunctional Beliefs and Attitudes about Sleep-16, and the Discrepancy between Desired Time in Bed and Desired Total Sleep Time (DBST) Index, along with the expected DBST Index of others.

RESULTS

Of 159 nursing professionals, 88.7% regarded the current lights-off time of 9:46±0:29 PM as appropriate. However, when considering others' usual bedtimes, the proportion perceiving the lights-off time as too early rose from 6.9% to 28.3%. Participants recommended delaying the lights-off time to 10:06±0:42 PM for patients' sleep and 10.22±0:46 PM for nursing care activities. Nursing professionals' insomnia severity was significantly higher among who responded that current light off time is too early after considering usual bedtime of other people.

CONCLUSION

This study underscores the need to reassess lights-off times in wards given individuals' typical bedtimes. The findings emphasize the need to address nursing professionals' perspectives and insomnia severity when optimizing lights-off schedules in healthcare settings.

Comparative Analysis of Methods of Evaluating Human Fatigue

The present study used four different methods to estimate fatigue. Forty-seven volunteers (45 men and 2 women), 41.3 ± 7.5 years old, truck operators for 11.5 ± 6.0 years, were included. All participants accepted the invitation to be included in the study. Actigraphy and core temperature were evaluated. The 5-minute psychomotor vigilance test, the Karolinksa Sleepiness Scale (KSS), and the postural assessment using the Light Sonometer™ (Belo Horizonte, Minas Gerais, Brazil) were performed. Fatigue prediction was performed using the Fatigue Avoidance Scheduling Tool (FAST) program. In response to the Pittsburgh Sleep Quality Index (PSQI), 51.06% had good sleep quality and 48.94% had poor sleep quality with an average efficiency of 81.6%. In response to the actigraphy, workers slept an average of 7.2 hours a day with 93.5% efficiency. The workers' core body temperature (CBT) cosinor analysis showed a preserved circadian curve. Core body temperature showed differences between the 6 hours worked in each shift. Similarly, the light sound level meter showed lower risk scores for fatigue in day shifts. Only the variable of the fastest 10% of the Psychomotor Vigilance Test (PVT) showed worse results, while no significant differences were observed by the KSS. The risk analysis by FAST showed a strong influence of the circadian factor. In conclusion, each method has positive and negative points, and it is up to the evaluator/manager to identify the method that best suits the purpose of the evaluation, as well as the local culture and conditions. We recommend using different methods of risk assessment and management in combination with fatigue prediction by Sonometer as well as carrying out assessments, which enable researchers to estimate performance and fatigue throughout the working day, since these may change over the duration of the working day.

Postprandial Sleep in Short-Sleeping Mexican Cavefish

Interactions between sleep and feeding behaviors are critical for adaptive fitness. Diverse species suppress sleep when food is scarce to increase the time spent foraging. Postprandial sleep, an increase in sleep time following a feeding event, has been documented in vertebrate and invertebrate animals. While interactions between sleep and feeding appear to be highly conserved, the evolution of postprandial sleep in response to changes in food availability remains poorly understood. Multiple populations of the Mexican cavefish, Astyanax mexicanus, have independently evolved sleep loss and increased food consumption compared to surface-dwelling fish of the same species, providing the opportunity to investigate the evolution of interactions between sleep and feeding. Here, we investigate the effects of feeding on sleep in larval and adult surface fish, and in two parallelly evolved cave populations of A. mexicanus. Larval surface and cave populations of A. mexicanus increase sleep immediately following a meal, providing the first evidence of postprandial sleep in a fish model. The amount of sleep was not correlated to meal size and occurred independently of feeding time. In contrast to larvae, postprandial sleep was not detected in adult surface or cavefish, which can survive for months without food. Together, these findings reveal that postprandial sleep is present in multiple short-sleeping populations of cavefish, suggesting sleep-feeding interactions are retained despite the evolution of sleep loss. These findings raise the possibility that postprandial sleep is critical for energy conservation and survival in larvae that are highly sensitive to food deprivation.

Circadian de(regulation) in physiology: implications for disease and treatment

Time plays a crucial role in the regulation of physiological processes. Without a temporal control system, animals would be unprepared for cyclic environmental changes, negatively impacting their survival. Experimental studies have demonstrated the essential role of the circadian system in the temporal coordination of physiological processes. Translating these findings to humans has been challenging. Increasing evidence suggests that modern lifestyle factors such as diet, sedentarism, light exposure, and social jet lag can stress the human circadian system, contributing to misalignment; i.e., loss of phase coherence across tissues. An increasing body of evidence supports the negative impact of circadian disruption on several human health parameters. This review aims to provide a comprehensive overview of how circadian disruption influences various physiological processes, its long-term health consequences, and its association with various diseases. To illustrate the relevant consequences of circadian disruption, we focused on describing the many physiological consequences faced by shift workers, a population known to experience high levels of circadian disruption. We also discuss the emerging field of circadian medicine, its founding principles, and its potential impact on human health.

Four SpsP neurons are an integrating sleep regulation hub in Drosophila

Sleep is essential and highly conserved, yet its regulatory mechanisms remain largely unknown. To identify sleep drive neurons, we imaged Drosophila brains with calcium-modulated photoactivatable ratiometric integrator (CaMPARI). The results indicate that the activity of the protocerebral bridge (PB) correlates with sleep drive. We further identified a key three-layer PB circuit, EPG-SpsP-PEcG, in which the four SpsP neurons in the PB respond to ellipsoid body (EB) signals from EPG neurons and send signals back to the EB through PEcG neurons. This circuit is strengthened by sleep deprivation, indicating a plasticity response to sleep drive. SpsP neurons also receive inputs from the sensorimotor brain region, suggesting that they may encode sleep drive by integrating sensorimotor and navigation cues. Together, our experiments show that the four SpsP neurons and their sleep regulatory circuit play an important and dynamic role in sleep regulation.

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 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 occurs mediated by sleep-dependent oscillation of glutamate-synaptic phenotypes.

Heat Shock Factor 1 Governs Sleep-Wake Cycles Across Species

Heat Shock Factor 1 (HSF1) is a critical transcription factor for cellular proteostasis, but its role in sleep regulation remains unexplored. We demonstrate that nuclear HSF1 levels in the mouse brain fluctuate with sleep-wake cycles, increasing during extended wakefulness and decreasing during sleep. Using CUT&RUN and RNA-seq, we identified HSF1-regulated transcriptional changes involved in synaptic organization, expanding its known functions beyond traditional heat shock responses. Both systemic and brain-specific Hsf1 knockout mice exhibit altered sleep homeostasis, including increased delta power after sleep deprivation and upregulation of sleep-related genes. However, these knockouts struggle to maintain sleep due to disrupted synaptic organization. In Drosophila , knockout of HSF1's ortholog results in fragmented sleep patterns, suggesting a conserved role for HSF1 in sleep regulation across species. Our findings reveal a novel molecular mechanism underlying sleep regulation and offer potential therapeutic targets for sleep disturbances.

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

LAY ABSTRACT

Fatigue 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.

Lipopolysaccharide-mediated effects of the microbiota on sleep and body temperature

Recent research suggests that microbial molecules translocated from the intestinal lumen into the host's internal environment may play a role in various physiological functions, including sleep. Previously, we identified that butyrate, a short-chain fatty acid produced by intestinal bacteria, and lipoteichoic acid, a cell wall component of gram-positive bacteria, induce sleep when their naturally occurring translocation is mimicked by direct delivery into the portal vein. Building upon these findings, we aimed to explore the sleep signaling potential of intraportally administered lipopolysaccharide (LPS), a primary component of gram-negative bacterial cell walls, in rats. Low dose of LPS (1 μg/kg) increased sleep duration and prolonged fever, without affecting systemic LPS levels. Interestingly, administering LPS systemically outside the portal region at a dose 20 times higher did not affect sleep, indicating a localized sensitivity within the hepatoportal region for the sleep and febrile effects of LPS. Furthermore, both the sleep- and fever-inducing effects of LPS were inhibited by indomethacin, a prostaglandin synthesis inhibitor, and replicated by intraportal administration of prostaglandin E2 or arachidonic acid, suggesting the involvement of the prostaglandin system in mediating these actions.

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.

Restful Rehabilitation: Sleep's Essential Role in Occupational Therapy Education, Intervention, and Research

All humans have the occupational right to sleep; therefore, occupational therapy practitioners must prioritize sleep with their clients. In this column, we identify ways to incorporate sleep health into the education and training of occupational therapy practitioners. This starts with identifying entry-level and continuing education opportunities to proclaim sleep as an occupation and a basic biological need. Current practitioners must recognize that sleep health is multidisciplinary, and existing interventions can help clients achieve good sleep health throughout their lifespan. Given the paucity of sleep research in occupational therapy, the potential exists to investigate new, occupation-based assessments and interventions. We provide specific approaches to expand sleep and sleep health knowledge in occupational therapy education, practice, and research.

Melatonin's role in the timing of sleep onset is conserved in nocturnal mice

Melatonin supplementation strengthens non-restorative sleep rhythms and its temporal alignment in both humans and night-active rodents. Of note, although the sleep cycle is reversed in day-active and night-active (nocturnal) mammals, both, produce melatonin at night under the control of the circadian clock. The effects of exogenous melatonin on sleep and sleepiness are relatively clear, but its endogenous role in sleep, particularly, in timing sleep onset (SO), remains poorly understood. We show in nocturnal mice that the increases in mid-nighttime sleep episodes, and the mid-nighttime decline in activity, are coupled to nighttime melatonin signaling. Furthermore, we show that endogenous melatonin modulates SO by reducing the threshold for wake-to-sleep transitioning. Such link between melatonin and SO timing may explain phenomena such as increased sleep propensity in circadian rhythm sleep disorders and chronic insomnia in patients with severely reduced nocturnal melatonin levels. Our findings demonstrate that melatonin's role in sleep is evolutionarily conserved, effectively challenging the argument that melatonin cannot play a major role in sleep regulation in nocturnal mammals, where the main activity phase coincides with high melatonin levels.

Timing Mechanisms for Circadian Seizures

For centuries, epileptic seizures have been noticed to recur with temporal regularity, suggesting that an underlying biological rhythm may play a crucial role in their timing. In this review, we propose to adopt the framework of chronobiology to study the circadian timing of seizures. We first review observations made on seizure timing in patients with epilepsy and animal models of the disorder. We then present the existing chronobiology paradigm to disentangle intertwined circadian and sleep-wake timing mechanisms. In the light of this framework, we review the existing evidence for specific timing mechanisms in specific epilepsy syndromes and highlight that current knowledge is far from sufficient. We propose that individual seizure chronotypes may result from an interplay between independent timing mechanisms. We conclude with a research agenda to help solve the urgency of ticking seizures.

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.

Bidirectional Interaction of Sepsis and Sleep Disorders: The Underlying Mechanisms and Clinical Implications

Sepsis is defined as life-threatening organ injury induced by infection, with high incidence and mortality. Sleep disorder is prevalent in septic patients and approximately 50% of patients with sepsis may develop atypical sleep patterns, but many of them may have been underdiagnosed by physicians. Sleep disorders and sepsis exhibit a close bidirectional relationship, with each condition significantly influencing the other. Conversely, sleep deprivation, sleep dysrhythmia and sleep fragmentation have been shown to impact the outcome of sepsis. This review endeavors to offer a comprehensive understanding of the intricate mechanisms that underpin the interplay between sepsis and sleep disorders, in addition to exploring potential clinical intervention strategies that could enhance outcomes for patients suffering from sepsis.

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.

Tapeworm infection affects sleep-like behavior in three-spined sticklebacks

Sleep is a complex and conserved biological process that affects several body functions and behaviors. Evidence suggests that there is a reciprocal interaction between sleep and immunity. For instance, fragmented sleep can increase the probability of parasitic infections and reduce the ability to fight infections. Moreover, viral and bacterial infections alter the sleep patterns of infected individuals. However, the effects of macro-parasitic infections on sleep remain largely unknown, and measuring sleep in non-model organisms remains challenging. In this study, we investigated whether macro-parasite infections could alter sleep-like behavior of their hosts. We experimentally infected three-spined sticklebacks (Gasterosteus aculeatus), a freshwater fish, with the tapeworm Schistocephalus solidus and used a hidden Markov model to characterize sleep-like behavior in sticklebacks. One to four days after parasite exposure, infected fish showed no difference in sleep-like behavior compared with non-exposed fish, and fish that were exposed-but-not-infected only showed a slight reduction in sleep-like behavior during daytime. Twenty-nine to 32 days after exposure, infected fish showed more sleep-like behavior than control fish, while exposed-but-not-infected fish showed overall less sleep-like behavior. Using brain transcriptomics, we identified immune- and sleep-associated genes that potentially underlie the observed behavioral changes. These results provide insights into the complex association between macro-parasite infection, immunity, and sleep in fish and may thus contribute to a better understanding of reciprocal interactions between sleep and immunity.

Sleep Characteristics Among Children with a Parental History of Alcohol Use Disorder

Purpose of Review

The purpose of the review was to examine findings on sleep characteristics among children with a parental history of alcohol use disorder (CPHAUDs) in different age groups. We identified unanswered questions and discussed directions for future research. We also discussed the implications of these current findings on alcohol prevention and intervention programs.

Recent Findings

Parental ratings and youth report of sleep difficulties have been longitudinally associated with the emergence of alcohol use and alcohol-related problems among both CPHAUDsand non-CPHAUDs. There were inconsistent findings comparing sleep characteristics in these two groups. Studies that used self-report and parental ratings reported no or minimal differences while studies that used actigraphy and polysomnography found significant, albeit moderate but meaningful differences.

Summary

Current research shows that CPHAUDs and non-CPHAUDs are similar on most objective and subjective sleep measures. There are a few significant differences between the two groups that may have implications for the development of behavioral problems, substance use and other risk behaviors.

Alzheimer's disease and sleep disorders: A bidirectional relationship

Alzheimer's disease (AD) is the most prevalent dementia, pathologically featuring abnormal accumulation of amyloid-β (Aβ) and hyperphosphorylated tau, while sleep, divided into rapid eye movement sleep (REM) and nonrapid eye movement sleep (NREM), plays a key role in consolidating social and spatial memory. Emerging evidence has revealed that sleep disorders such as circadian disturbances and disruption of neuronal rhythm activity are considered as both candidate risks and consequence of AD, suggesting a bidirectional relationship between sleep and AD. This review will firstly grasp basic knowledge of AD pathogenesis, then highlight macrostructural and microstructural alteration of sleep along with AD progression, explain the interaction between accumulation of Aβ and hyperphosphorylated tau, which are two critical neuropathological processes of AD, as well as neuroinflammation and sleep, and finally introduce several methods of sleep enhancement as strategies to reduce AD-associated neuropathology. Although theories about the bidirectional relationship and relevant therapeutic methods in mice have been well developed in recent years, the knowledge in human is still limited. More studies on how to effectively ameliorate AD pathology in patients by sleep enhancement and what specific roles of sleep play in AD are needed.

Association between sleep duration and the risk of hyperhomocysteinemia among adults in the United States: National Health and Nutrition Examination Survey, 2005-2006

The study aimed to discuss the association between sleep duration and the risk of hyperhomocysteinemia (Hhcy). This cross-sectional study included 4173 adults (≥ 20 years) from the National Health and Nutrition Examination Survey 2005-2006. According to their sleep duration, participants were divided into five subgroups. Multivariate logistic regression analysis models and restrictive cubic spline regressions were used to explore the association between sleep duration and the risk of Hhcy. Compared with the participants who sleep 7 h, sleep deprivation (≤ 5 h) increased the risk of Hhcy, odds ratio (OR) 1.68 (95% confidence interval (CI) 1.06-2.68); Excessive sleep (≥ 9 h) also increased the risk of Hhcy, OR 1.86 (95% CI 1.09-3.14) after adjusting for a series of confounding factors in the entire population. The risk of Hhcy was distributed in a U-shape with sleep duration. Similar results were demonstrated in obese populations. The association between sleep duration and the risk of Hhcy is U-shaped. Both sleep deprivation and excessive sleep can increase the risk of Hhcy.

Preoccupation with sleep and dysfunctional beliefs about sleep mediate the influence of psychological inflexibility on insomnia in the older adult population

INTRODUCTION

This study aimed to explore whether the Discrepancy between the desired time in Bed and the desired total Sleep Time (DBST) index influences insomnia severity in the older adult population and examined the potential role of psychological inflexibility in this association.

METHODS

An online survey study was conducted for older individuals aged ≥ 65 via a survey company between January and February 2023. A total of 300 responses and data without personally identifiable information were delivered to the researchers. The survey questionnaires include the DBST, Glasgow Sleep Effort Scale (GSES), Insomnia Severity Index (ISI), Dysfunctional Beliefs about Sleep-2 items (DBS-2), and Acceptance and Action Questionnaire-II (AAQ-II).

RESULTS

The analysis included 295 older adult participants. The DBST index was significantly correlated with all questionnaires. Linear regression revealed the DBST index was predicted only by the ISI (β = 0.26, p = 0.003). Mediation analysis showed that the GSES (Z = 2.92, p = 0.003) and DBS-2 (Z = 2.17, p = 0.030) mediated the effect of the DBST index on the ISI, while the AAQ-II did not. Path analysis showed that the DBST could be directly predicted by the ISI (Z = 2.94, p = 0.003), GSES (Z = 2.75, p = 0.006), and DBS2 (Z = 2.71, p = 0.007) but not by the AAQ-II itself. However, the AAQ-II exerted a significant indirect effect on the ISI through the DBS-2 (Z = 2.21, p = 0.027) and GSES (z = 2.24, p = 0.025).

CONCLUSIONS

Our study showed that preoccupation and dysfunctional beliefs about sleep may mediate the relationship between the DBST index and insomnia severity in the older adult population. We opine that psychological inflexibility might play a significant role in insomnia severity via preoccupation with and dysfunctional beliefs about sleep.

Neuronal subtype-specific transcriptomic changes in the cerebral neocortex associated with sleep pressure

Sleep is homeostatically regulated by sleep pressure, which increases during wakefulness and dissipates during sleep. Recent studies have suggested that the cerebral neocortex, a six-layered structure composed of various layer- and projection-specific neuronal subtypes, is involved in the representation of sleep pressure governed by transcriptional regulation. Here, we examined the transcriptomic changes in neuronal subtypes in the neocortex upon increased sleep pressure using single-nucleus RNA sequencing datasets and predicted the putative intracellular and intercellular molecules involved in transcriptome alterations. We revealed that sleep deprivation (SD) had the greatest effect on the transcriptome of layer 2 and 3 intratelencephalic (L2/3 IT) neurons among the neocortical glutamatergic neuronal subtypes. The expression of mutant SIK3 (SLP), which is known to increase sleep pressure, also induced profound changes in the transcriptome of L2/3 IT neurons. We identified Junb as a candidate transcription factor involved in the alteration of the L2/3 IT neuronal transcriptome by SD and SIK3 (SLP) expression. Finally, we inferred putative intercellular ligands, including BDNF, LSAMP, and PRNP, which may be involved in SD-induced alteration of the transcriptome of L2/3 IT neurons. We suggest that the transcriptome of L2/3 IT neurons is most impacted by increased sleep pressure among neocortical glutamatergic neuronal subtypes and identify putative molecules involved in such transcriptional alterations.

Morning resting hypothalamus-dorsal striatum connectivity predicts individual differences in diurnal sleepiness accumulation

While the significance of obtaining restful sleep at night and maintaining daytime alertness is well recognized for human performance and overall well-being, substantial variations exist in the development of sleepiness during diurnal waking periods. Despite the established roles of the hypothalamus and striatum in sleep-wake regulation, the specific contributions of this neural circuit in regulating individual sleep homeostasis remain elusive. This study utilized resting-state functional magnetic resonance imaging (fMRI) and mathematical modeling to investigate the role of hypothalamus-striatum connectivity in subjective sleepiness variation in a cohort of 71 healthy adults under strictly controlled in-laboratory conditions. Mathematical modeling results revealed remarkable individual differences in subjective sleepiness accumulation patterns measured by the Karolinska Sleepiness Scale (KSS). Brain imaging data demonstrated that morning hypothalamic connectivity to the dorsal striatum significantly predicts the individual accumulation of subjective sleepiness from morning to evening, while no such correlation was observed for the hypothalamus-ventral striatum connectivity. These findings underscore the distinct roles of hypothalamic connectivity to the dorsal and ventral striatum in individual sleep homeostasis, suggesting that hypothalamus-dorsal striatum circuit may be a promising target for interventions mitigating excessive sleepiness and promoting alertness.

Sleep disturbances in chronic liver disease

Sleep disturbances are common in chronic liver disease and significantly impact patient outcomes and quality of life. The severity and nature of sleep disturbances vary by liver disease etiology and severity. While there is ongoing research into the association between liver disease and sleep-wake dysfunction, the underlying pathophysiology varies and, in many cases, is poorly understood. Liver disease is associated with alterations in thermoregulation, inflammation, and physical activity, and is associated with disease-specific complications, such as HE, that may directly affect sleep. In this article, we review the relevant pathophysiologic processes, disease-specific sleep-wake disturbances, and clinical management of CLD-associated sleep-wake disturbances.

Exploring the Therapeutic Potential of Terpenoids for Depression and Anxiety

This review focus on the terpenoids as potential therapeutic agents for depression and anxiety disorders, which naturally found in a variety of plants and exhibit a wide range of biological activities. Among the terpenoids discussed in this review are α-pinene, β-caryophyllene, α-phellandrene, limonene, β-linalool, 1, 8-cineole, β-pinene, caryophyllene oxide, p-cymene, and eugenol. All of these compounds have been studied extensively regarding their pharmacological properties, such as neuroprotective effect, anti-inflammation, antibacterial, regulation of neurotransmitters and antioxidant effect. Preclinical evidence are reviewed to highlight their diverse mechanisms of action and therapeutic potential to support antidepressant and anxiolytic properties. Additionally, challenges and future directions are also discussed to emphasize therapeutic utility of terpenoids for mental health disorders. Overall, this review provides a promising role of terpenoids as novel therapeutic agents for depression and anxiety, with potential implications for the development of more effective and well-tolerated treatments in the field of psychopharmacology.

Assessing sleep in primary brain tumor patients using smart wearables and patient-reported data: Feasibility and interim analysis of an observational study

Background

Sleep-wake disturbances are common and disabling in primary brain tumor (PBT) patients but studies exploring longitudinal data are limited. This study investigates the feasibility and relationship between longitudinal patient-reported outcomes (PROs) and physiologic data collected via smart wearables.

Methods

Fifty-four PBT patients ≥ 18 years wore Fitbit smart-wearable devices for 4 weeks, which captured physiologic sleep measures (eg, total sleep time, wake after sleep onset [WASO]). They completed PROs (sleep hygiene index, PROMIS sleep-related impairment [SRI] and Sleep Disturbance [SD], Morningness-Eveningness Questionnaire [MEQ]) at baseline and 4 weeks. Smart wearable use feasibility (enrollment/attrition, data missingness), clinical characteristics, test consistency, PROs severity, and relationships between PROs and physiologic sleep measures were assessed.

Results

The majority (72%) wore their Fitbit for the entire study duration with 89% missing < 3 days, no participant withdrawals, and 100% PRO completion. PROMIS SRI/SD and MEQ were all consistent/reliable (Cronbach's alpha 0.74-0.92). Chronotype breakdown showed 39% morning, 56% intermediate, and only 6% evening types. Moderate-severe SD and SRI were reported in 13% and 17% at baseline, and with significant improvement in SD at 4 weeks (P = .014). Fitbit-recorded measures showed a correlation at week 4 between WASO and SD (r = 0.35, P = .009) but not with SRI (r = 0.24, P = .08).

Conclusions

Collecting sleep data with Fitbits is feasible, PROs are consistent/reliable, > 10% of participants had SD and SRI that improved with smart wearable use, and SD was associated with WASO. The skewed chronotype distribution, risk and impact of sleep fragmentation mechanisms warrant further investigation.

Trial Registration

NCT04 669 574.