Impact of Sleep Fragmentation on Cognition and Fatigue

Sleep Fragmentation Modulates the Neurophysiological Correlates of Cognitive Fatigue

Cognitive fatigue (CF) is a critical factor affecting performance and well-being. It can be altered in suboptimal sleep quality conditions, e.g., in patients suffering from obstructive sleep apnea who experience both intermittent hypoxia and sleep fragmentation (SF). Understanding the neurophysiological basis of SF in healthy individuals can provide insights to improve cognitive functioning in disrupted sleep conditions. In this electroencephalographical (EEG) study, we investigated in 16 healthy young participants the impact of experimentally induced SF on the neurophysiological correlates of CF measured before, during, and after practice on the TloadDback, a working memory task tailored to each individual's maximal cognitive resources. The participants spent three consecutive nights in the laboratory two times, once in an undisrupted sleep (UdS) condition and once in an SF condition induced by non-awakening auditory stimulations, counterbalanced and performed the TloadDback task both in a high (HCL) and a low (LCL) cognitive load condition. EEG activity was recorded during wakefulness in the 5 min resting state immediately before and after, as well as during the 16 min of the TloadDback task practice. In the high cognitive load under a sleep-fragmentation (HCL/SF) condition, high beta power increased during the TloadDback, indicating heightened cognitive effort, and the beta and alpha power increased in the post- vs. pre-task resting state, suggesting a relaxation rebound. In the low cognitive load/undisturbed sleep (LCL/UdS) condition, low beta activity increased, suggesting a relaxed focus, as well as mid beta activity associated with active thinking. These findings highlight the dynamic impact of SF on the neurophysiological correlates of CF and underscore the importance of sleep quality and continuity to maintain optimal cognitive functioning.

The paradoxical impact of periodic limb movements on isolated REM sleep behavior disorder patients

Recently, the α-synuclein origin and connectome model described two types of Parkinson's disease: "brain-first" and "body-first" subtypes. We aimed to investigate the role of periodic limb movements during sleep (PLMS) in identifying these subtypes starting from a prodromal stage of α-synucleinopathies. 191 patients with isolated REM sleep behavior disorder (iRBD) underwent video-polysomnography (vPSG), questionnaires, clinical interview, and neuropsychological battery. Patients who presented PLMS index (PLMSi) > 15 were compared with patients presenting PLMSi ≤ 15 on clinical questionnaires, vPSG, and neuropsychological domains with age as a covariate. Correlations were performed between PLMSi and vPSG and neuropsychological domains in both groups of iRBD. 48.2% of patients presented PLMSi > 15. iRBD subgroup with PLMSi > 15 performed better than the iRBD subgroup with PLMSi ≤ 15 in the executive function domain. In patients with PLMSi > 15 negative correlations were observed between PLMSi and some neuropsychological domains (memory, language, and executive function). Moreover, this subgroup was older and their PLMSi was positively correlated with wake-after-sleep onset and inversely correlated with total sleep time and sleep efficiency, suggesting a detrimental effect of PLM on sleep also in this cohort. Patients with PLMSi > 15 are characterized by a more preserved cognitive status, despite a more disrupted sleep. PLMSi could be explored in longitudinal studies concerning the "brain-first" and "body-first" model.

Sleep, hopelessness, and suicidal ideation: An ecological momentary assessment and actigraphy study

Recent research shows that sleep disturbances are linked to increased suicidal ideation. In the present longitudinal cohort study, we used subjective (ecological momentary assessment, EMA) and objective (actigraphy) measures to examine the effects of sleep parameters on next-day suicidal ideation. Further, we examined hopelessness as a mediator between insufficient sleep and increased suicidal ideation. Individuals with current suicidal ideation (N = 82) completed 21 days of EMA and actigraphy to estimate suicidal ideation, hopelessness and sleep parameters. Multilevel linear-mixed models were used to examine the effects of sleep parameters on next-day suicidal ideation, as well as for the mediating effect of hopelessness (in the morning) on the association between previous night's sleep and suicidal ideation levels the next day. Significant concordance existed between subjective and objective sleep measures, with moderate-to-large correlations (r = 0.44-0.58). Lower subjective sleep quality and efficiency, shorter total sleep time and increased time awake after sleep onset were significantly associated with increased next-day suicidal ideation (controlling for previous-day suicidal ideation). Actigraphy-measured sleep fragmentation was also a significant predictor of next-day ideation. Hopelessness mediated the effects of the subjective sleep parameters on suicidal ideation, but did not account for the association with sleep fragmentation. Therefore, individuals' psychological complaints (hopelessness, suicidal ideation) were better predicted by subjective sleep complaints than by objective sleep indices. Increased hopelessness following from perceived insufficient sleep appears an important explanatory factor when considering the link between sleep disturbances and suicidal ideation.

Obstructive Sleep Apnea and Serotoninergic Signalling Pathway: Pathomechanism and Therapeutic Potential

Obstructive Sleep Apnea (OSA) is a disorder characterized by repeated upper airway collapse during sleep, leading to apneas and/or hypopneas, with associated symptoms like intermittent hypoxia and sleep fragmentation. One of the agents contributing to OSA occurrence and development seems to be serotonin (5-HT). Currently, the research focuses on establishing and interlinking OSA pathogenesis and the severity of the disease on the molecular neurotransmitter omnipresent in the human body-serotonin, its pathway, products, receptors, drugs affecting the levels of serotonin, or genetic predisposition. The 5-HT system is associated with numerous physiological processes such as digestion, circulation, sleep, respiration, and muscle tone-all of which are considered factors promoting and influencing the course of OSA because of correlations with comorbid conditions. Comorbidities include obesity, physiological and behavioral disorders as well as cardiovascular diseases. Additionally, both serotonin imbalance and OSA are connected with psychiatric comorbidities, such as depression, anxiety, or cognitive dysfunction. Pharmacological agents that target 5-HT receptors have shown varying degrees of efficacy in reducing the Apnea-Hypopnea Index and improving OSA symptoms. The potential role of the 5-HT signaling pathway in modulating OSA provides a promising avenue for new therapeutic interventions that could accompany the primary treatment of OSA-continuous positive airway pressure. Thus, this review aims to elucidate the complex role of 5-HT and its regulatory mechanisms in OSA pathophysiology, evaluating its potential as a therapeutic target. We also summarize the relationship between 5-HT signaling and various physiological functions, as well as its correlations with comorbid conditions.

Actigraphy-assessed sleep duration and quality and executive function in a sample of typically developing preschoolers

Sleep is essential for cognitive development and brain maturation during early childhood. Studies focused on preschool populations using objective measures of sleep are still scarce. The objective of this study was to examine the associations between objective measures of sleep duration and quality with executive functioning in a 133 non-clinical sample of Spanish participants (Mage = 60.33 months, SD = 9.04; ages 41-77 months; 51.1% girls). Sleep was assessed for five weeknights using actigraphy; Shape School task was applied to assess inhibition and cognitive flexibility; and Word Span task was used to assess working memory. The results revealed that relation between sleep and executive functioning was significant for inhibition and working memory. Preschoolers with higher sleep efficiency showed better results in executive functioning tasks after controlling for the effect of age. Additionally, age and sleep duration and quality variables were predictive of inhibition, working memory, and cognitive flexibility. These results suggest that the different dimensions of sleep could play an important role in the development of executive functions during preschool age. Therefore, improving sleep could lead to an improvement in children's executive functioning in both clinical and educational contexts.

Sleep and lucid dreaming in adolescent athletes and non-athletes

During lucid dreaming (LD), dreamers are aware of experiencing a dream and may consciously influence its content. This study used an online questionnaire to investigate the LD frequency and applications in 193 adolescent athletes and non-athletes (17.40 ± 2.09 years; 46% athletes, 54% controls). Given the critical role that sleep plays in adolescent health, development, and performance, associations of LD with various sleep parameters were also explored. LD is prominent in adolescents (67.4% experienced it at least once, 30.0% once a month or more, 12.9% at least once a week), but similar in terms of frequency and uses between athletes and non-athletes. A higher proportion of those who practiced sports/dance during LD reported improved waking self-efficacy (57.1%) over sport performance (42.9%). There was no indication that chronotype preference may influence LD nor that LD may be detrimental to adolescent sleep. Athletes and controls had similar sleep durations, daytime sleepiness, and sleep disturbances frequency, but athletes reported higher sleep quality. Despite, on average, meeting the minimum sleep recommendation guidelines for their age, a relatively large proportion of adolescents did not attain sufficient sleep, particularly on weeknights (47.4% 14-17 years; 20.0% 18-21 years), suggesting that restricted sleep remains prevalent in adolescent populations.

Sleep Disturbance During Post-Traumatic Amnesia and Early Recovery After Traumatic Brain Injury

After moderate to severe traumatic brain injury (TBI), sleep disturbance commonly emerges during the confused post-traumatic amnesia (PTA) recovery stage. However, the evaluation of early sleep disturbance during PTA, its recovery trajectory, and influencing factors is limited. This study aimed to evaluate sleep outcomes in patients experiencing PTA using ambulatory gold-standard polysomnography (PSG) overnight and salivary endogenous melatonin (a hormone that influences the sleep-wake cycle) assessment at two time-points. The relationships between PSG-derived sleep-wake parameters and PTA symptoms (i.e., agitation and cognitive disturbance) were also evaluated. In a patient subset, PSG was repeated after PTA had resolved to assess the trajectory of sleep disturbance. Participants with PTA were recruited from Epworth HealthCare's inpatient TBI Rehabilitation Unit. Trained nurses administered overnight PSG at the patient bedside using the Compumedics Somté portable PSG device (Compumedics, Ltd., Australia). Two weeks after PTA had resolved, PSG was repeated. On a separate evening, two saliva specimens were collected (at 24:00 and 06:00) for melatonin testing. Results of routine daily hospital measures (i.e., Agitated Behavior Scale and Westmead PTA Scale) were also collected. Twenty-nine patients were monitored with PSG (mean: 41.6 days post-TBI; standard deviation [SD]: 28.3). Patients' mean sleep duration was reduced (5.6 h, SD: 1.2), and was fragmented with frequent awakenings (mean: 27.7, SD: 15.0). Deep, slow-wave restorative sleep was reduced, or completely absent (37.9% of patients). The use of PSG did not appear to exacerbate patient agitation or cognitive disturbance. Mean melatonin levels at both time-points were commonly outside of normal reference ranges. After PTA resolved, patients (n = 11) displayed significantly longer mean sleep time (5.3 h [PTA]; 6.5 h [out of PTA], difference between means: 1.2, p = 0.005). However, disturbances to other sleep-wake parameters (e.g., increased awakenings, wake time, and sleep latency) persisted after PTA resolved. This is the first study to evaluate sleep disturbance in a cohort of patients as they progressed through the early TBI recovery phases. There is a clear need for tailored assessment of sleep disturbance during PTA, which currently does not form part of routine hospital assessment, to suggest new treatment paradigms, enhance patient recovery, and reduce its long-term impacts.

A case-control study on the effect of rhythmic masticatory muscle activity (RMMA) clusters on sleep fragmentation and severity of orofacial muscle pain in sleep bruxism

Rhythmic masticatory muscle activity (RMMA) is a periodic muscle activity that characterises sleep bruxism (SB) events. These can occur as a single event, in pairs, or in clusters. Since RMMA episodes often occur in clusters and the relevance of this occurrence is unknown, we conducted a study to investigate the effect of RMMA clusters on sleep fragmentation and the severity of orofacial muscle pain. This study involved a secondary analysis using data from 184 adult subjects with orofacial muscle pain who underwent definitive polysomnography (PSG) for sleep bruxism diagnosis. Self-reported orofacial muscle pain (OFMP) was assessed using the numeric rating scale, and additional evaluation of side-to-side equivalence (symmetry) was described using a binary system. Among the 184 participants, 60.8% (n = 112) did not exhibit clusters and among the 72 participants with clusters, 36.1% (n = 26) and 63.9% (n = 46) were in the high and low RMMA frequency groups, respectively. The high SB group had significantly three times more phasic RMMA events than the noncluster group. A total of 89.67% (n = 165) of subjects reported orofacial muscle pain. While there was no difference in the severity of OFMP among groups, a significant decrease in symmetry between the severity of temporal muscle pain on the left and right sides was noted in the cluster group compared with the noncluster group. Clustering of RMMA events is associated with sleep fragmentation. The asymmetry of temporal muscle pain is related to the presence of RMMA clusters in sleep bruxism.

The Potential Effect of Changing Patient Position on Snoring: A Systematic Review

Approximately 45% of adults snore occasionally, and 25% snore regularly, with a higher prevalence in men and an increase among postmenopausal women due to hormonal changes. Snoring is a health concern linked to vascular disease and decreased quality of life for both snorers and their bed partners. Effective snoring treatment, which aims to reduce or eliminate the sound, is challenging and depends on factors like age, comorbidities, disease severity, and anatomical features. This review aims to provide a systematic overview of the current literature on the effects of positional therapy (PT) on snoring. Various devices facilitate PT, including anti-snoring pillows and vibration alarms. PT devices maintain head and neck alignment to keep airways open, while head of bed elevation (HOBE) solutions reduce upper airway collapses by elevating the head and trunk. Studies show that PT and HOBE reduce snoring by increasing airway cross-sectional area and decreasing closing pressure. Despite their benefits, these non-surgical treatments have limitations, such as discomfort in certain sleeping positions and intolerance to prolonged head elevation. While reducing snoring intensity is critical for health reasons, further comparative studies between the different devices are needed to enhance snoring management.

The effect of transcranial electrical stimulation on the relief of mental fatigue

Objective

The presence of mental fatigue seriously affects daily life and working conditions. Non-invasive transcranial electrical stimulation has become an increasingly popular tool for relieving mental fatigue. We investigated whether transcranial direct current stimulation (tDCS) and transcranial alternating current stimulation (tACS) could be used to alleviate the state of mental fatigue in a population of healthy young adults and compared their effects.

Methods

We recruited 10 participants for a blank control, repeated measures study. Each participant received 15 min of anodal tDCS, α-tACS, and blank stimulation. Participants were required to fill in the scale, perform the test task and collect ECG signals in the baseline, fatigue and post-stimulus states. We then assessed participants' subjective fatigue scale scores, test task accuracy and HRV characteristics of ECG signals separately.

Results

We found that both anodal tDCS and α-tACS significantly (P < 0.05) reduced subjective fatigue and improved accuracy on the test task compared to the blank group, and the extent of change was greater with tACS. For the HRV features extracted from ECG signals. After tACS intervention, SDNN (t = -3.241, P = 0.002), LF (t = -3.511, P = 0.001), LFn (t = -3.122, P = 0.002), LFn/HFn (-2.928, P = 0.005), TP (t = -2.706, P = 0.008), VLF (t = -3.002, P = 0.004), SD2 (t = -3.594, P = 0.001) and VLI (t = -3.564, P = 0.001) showed a significant increasing trend, and HFn (t = 3.122, P = 0.002), SD1/SD2 (t = 3.158, P = 0.002) and CCM_1 (t = 3.106, P = 0.003) showed a significant decreasing trend. After tDCS intervention, only one feature, TINN, showed a significant upward trend (P < 0.05). The other features showed non-significant changes but roughly the same trend as the tACS group.

Conclusion

Both tDCS and α-tACS can be effective in relieving mental fatigue, and α-tACS is more effective than tDCS. This study provides theoretical support for tDCS with α-tACS having a alleviating effect on mental fatigue and the use of ECG as a valid objective assessment tool.

Preoperative recovery sleep ameliorates postoperative cognitive dysfunction aggravated by sleep fragmentation in aged mice by enhancing EEG delta-wave activity and LFP theta oscillation in hippocampal CA1

Sleep fragmentation (SF) is a common sleep problem experienced during the perioperative period by older adults, and is associated with postoperative cognitive dysfunction (POCD). Increasing evidence indicates that delta-wave activity during non-rapid eye movement (NREM) sleep is involved in sleep-dependent memory consolidation and that hippocampal theta oscillations are related to spatial exploratory memory. Recovery sleep (RS), a self-regulated state of sleep homeostasis, enhances delta-wave power and memory performance in sleep-deprived older mice. However, it remains unclear whether RS therapy has a positive effect on cognitive changes following SF in older mouse models. Therefore, this study aimed to explore whether preoperative RS can alleviate cognitive deficits in aged mice with SF. A model of preoperative 24-h SF combined with exploratory laparotomy-induced POCD was established in 18-month-old mice. Aged mice were treated with preoperative 6-h RS following SF and postoperative 6-h RS following surgery, respectively. The changes in hippocampus-dependent cognitive function were investigated using behavioral tests, electroencephalography (EEG), local field potential (LFP), magnetic resonance imaging, and neuromorphology. Mice that underwent 24-h SF combined with surgery exhibited severe spatial memory impairment; impaired cognitive performance could be alleviated by preoperative RS treatment. In addition, preoperative RS increased NREM sleep; enhanced EEG delta-wave activity and LFP theta oscillation in the hippocampal CA1; and improved hippocampal perfusion, microstructural integrity, and neuronal damage. Taken together, these results provide evidence that preoperative RS may ameliorate the severity of POCD aggravated by SF by enhancing delta slow-wave activity and hippocampal theta oscillation, and by ameliorating the reduction in regional cerebral blood flow and white matter microstructure integrity in the hippocampus.

Melatonin Improves Glucose Homeostasis and Insulin Sensitivity by Mitigating Inflammation and Activating AMPK Signaling in a Mouse Model of Sleep Fragmentation

Sleep fragmentation (SF) can increase inflammation and production of reactive oxygen species (ROS), leading to metabolic dysfunction. SF is associated with inflammation of adipose tissue and insulin resistance. Several studies have suggested that melatonin may have beneficial metabolic effects due to activating AMP-activated protein kinase (AMPK). However, it is unclear whether melatonin affects the AMPK signaling pathway in SF-induced metabolic dysfunction. Therefore, we hypothesize that SF induces metabolic impairment and inflammation in white adipose tissue (WAT), as well as altered intracellular homeostasis. We further hypothesize that these conditions could be improved by melatonin treatment. We conducted an experiment using adult male C57BL/6 mice, which were divided into three groups: control, SF, and SF with melatonin treatment (SF+Mel). The SF mice were housed in SF chambers, while the SF+Mel mice received daily oral melatonin. After 12 weeks, glucose tolerance tests, insulin tolerance tests, adipose tissue inflammation tests, and AMPK assessments were performed. The SF mice showed increased weight gain, impaired glucose regulation, inflammation, and decreased AMPK in WAT compared to the controls. Melatonin significantly improved these outcomes by mitigating SF-induced metabolic dysfunction, inflammation, and AMPK downregulation in adipose tissue. The therapeutic efficacy of melatonin against cardiometabolic impairments in SF may be due to its ability to restore adipose tissue homeostatic pathways.

Objective sleep characteristics and hypertension: a community-based cohort study

Objective

The link between sleep quality and hypertension risk is well-established. However, research on the specific dose-relationship between objective sleep characteristics and hypertension incidence remains limited. This study aims to explore the dose-relationship association between objective sleep characteristics and hypertension incidence.

Methods

A community-based prospective cohort study design was employed using data from the Sleep Heart Health Study (SHHS). A total of 2,460 individuals were included in the study, of which 780 had hypertension. Baseline personal characteristics and medical history were collected. Objective sleep characteristics were obtained through polysomnography (PSG). Multivariate logistic regression models were utilized for analysis. Restricted cubic splines (RCS) were used to examine dose-relationship associations.

Results

After adjusting for covariates, the percentage of total sleep duration in stage 2 (N2%) was positively associated with hypertension incidence, while the N3% was negatively associated with hypertension incidence Odds ratio (OR) = 1.009, 95% confidence interval (CI) [1.001, 1.018], P = 0.037; OR = 0.987, 95% CI: [0.979, 0.995], P = 0.028, respectively. For every 10% increase in N2 sleep, the risk of developing hypertension increases by 9%, while a 3% decrease in N3 sleep corresponds to a 0.1% increase in the incidence of hypertension. In the subgroup of non-depression, a positive association between N2% and hypertension was significant statistically (OR = 1.012, 95%CI, 1.002, 1.021, P = 0.013, Pinteraction = 0.013). RCS demonstrated that the risk of developing hypertension was lower when N2% ranged from 38% to 58% and rapidly increased thereafter (P = 0.002, non-linear P = 0.040). The lowest risk for hypertension incidence risk of N3% occurring at 25%, and a significant increase below 15% or above 40% (P = 0.001, non-linear P = 0.008).

Conclusions

There's a negative association between N3% and the incidence of hypertension, and a positive association between N2% and the incidence of hypertension, particularly among non-depression individuals. These associations exhibit strong non-linear dose-response relationships.

Predictors of sleep quality components in patients undergoing transarterial chemoembolisation: a cross-sectional study

PURPOSE

Patients undergoing transarterial chemoembolisation experience postembolisation symptoms and interferences affecting sleep quality, which require intervention. The study aimed to identify the predictors of sleep quality components in patients undergoing transarterial chemoembolisation.

METHODS

This study included two groups of participants: 50 patients undergoing transarterial chemoembolisation and 45 nurses caring for them. Data were collected from September to November 2022 using a structured questionnaire, and analysed using descriptive statistics, the t-test, analysis of variance, Spearman's rank correlation, and multiple regression analysis using the SPSS 27.0 program (IBM Corp., Armonk, NY, USA).

RESULTS

The mean sleep quality score was 40.28±14.10. Heat sensation (t=-2.08, p=.043) and fatigue (t=-4.47, p<.001) predicted sleep fragmentation in 38.6% of the patients. Abdominal pain (t=-2.54, p=.014), vomiting (t=-2.21, p=.032), and the expected fatigue by the nurses (t=2.68, p=.014) predicted sleep length in 41.7% of patients. Abdominal pain (t=-2.05, p=.046) explained 42.9% of sleep depth.

CONCLUSION

Based on the predictors of sleep quality components obtained in this study, strategies to improve sleep quality tailored to patients undergoing transarterial chemoembolisation should be developed. This study highlighted the need to bridge the gap between patients' and nurses' expected fatigue and its contribution to sleep fragmentation and sleep length. It also highlighted the importance of noncontact temperature measurement, controlling vomiting, and pain relief for improving sleep length in patients undergoing transarterial chemoembolisation.

Inflammatory Markers and Sleep Architecture in Sleep Bruxism-A Case-Control Study

Background: Sleep bruxism (SB) is a common sleep-related movement behavior with a multifaceted etiology and a deficiently understood pathophysiology. A recent hypothesis suggests a link between SB and systemic inflammation. The scope of the study was to determine whether bruxers have altered sleep structure and different levels of inflammatory parameters compared to nonbruxers. Methods: A total of 83 adults underwent full-night polysomnography. The polysomnograms were evaluated using the American Academy of Sleep Medicine (AASM) guidelines. Then, the blood samples were obtained from the participants by venipuncture and the analyses were performed. The study group was divided based on bruxism episode index (BEI) into two groups: BEI ≤ 4 and BEI > 4. Results: In comparison with nonbruxers, the oxygen desaturation index (ODI) was significantly higher in severe bruxers (7.5 ± 11.08 vs. 3.33 ± 5.75, p < 0.005), as well as the arousal parameters (7.77 ± 4.68 vs. 4.03 ± 2.97, p < 0.001), and the mean oxygen desaturation (3.49 ± 0.69 vs. 3.01 ± 0.67, p < 0.05). Moreover, the differences in sleep architecture and deprivation of the deep sleep phase were observed, the non-REM sleep stage 3 was significantly shorter in severe bruxers (p < 0.03). Differences were also noted in non-REM sleep stage 1 and REM sleep phase. In the investigated group, there were no statistical differences in inflammatory cytokines levels between bruxers and nonbruxers. Conclusions: Sleep bruxism is associated with sleep structure alterations and may be associated with deep sleep phase deprivation. The inflammatory markers are not linearly correlated with the severity of sleep bruxism expressed as BEI.

Sleep apnea syndrome associated with gonadal hormone imbalance (Review)

Patients with obstructive sleep apnea exhibit an increased risk of developing gonadal disorders. Because a notable number of people worldwide have sleep respiratory and reproductive disorders, it is essential to recognize the association between local upper airway dysfunction and its gonadal effects. Repeated breathing pauses cause sleep fragmentation, disorganization of sleep cycles and stages, sympathetic activation, intermittent hypoxemia and systemic inflammation. Nocturnal intermittent hypoxemia has a direct central effect on neurotransmitters, with disturbances in the normal production of hypothalamic-pituitary hormones. Awakenings and micro-awakenings at the end of apneic episodes produce a central stress responsible for hormonal changes and subsequent endocrine imbalances. The aim of the present study was to investigate the impact of obstructive sleep apnea syndrome (OSAS) on gonadal hormonal homeostasis and its consequences. Recognizing and understanding how local upper airway dysfunction causes gonadal imbalance may facilitate better care for patients with OSAS. Although there may be a direct relationship between sleep-disordered breathing and gonadal function mediated by hormones via the hypothalamic-pituitary-gonadal axis, to date, current therapies have not been effective.

Insomnia and REM sleep instability

In this narrative review, we give an overview of the concept of rapid eye movement sleep instability and its reported implications in the context of insomnia. The term rapid eye movement sleep instability was coined to describe the observation of a modified rapid eye movement quality in insomnia, characterized by an increased tendency of perceiving rapid eye movement sleep as wake, a small but consistent rapid eye movement sleep reduction and an increased rapid eye movement sleep arousal index. Current research highlights relationships that are transdiagnostic in nature, corresponding to the known interaction of insomnia with many psychiatric disorders, and showing relationships to chronic stress and anxiety disorders.

Sleep in Residents: A Comparison between Anesthesiology and Occupational Medicine Interns

Sleep deprivation is a significant risk to the health and judgment of physicians. We wanted to investigate whether anesthesiology residents (ARs) who work only one night shift per week have different physical and mental health from occupational medicine residents (OMRs) who do not work at night. A total of 21 ARs and 16 OMRs attending a university general hospital were asked to wear an actigraph to record sleep duration, heart rate and step count and to complete a questionnaire for the assessment of sleep quality, sleepiness, fatigue, occupational stress, anxiety, depression and happiness. ARs had shorter sleep duration than OMRs; on average, they slept 1 h and 20 min less (p < 0.001). ARs also had greater daytime sleepiness, a higher heart rate and lower happiness than OMRs. These results should be interpreted with caution given the cross-sectional nature of the study and the small sample size, but they are an incentive to promote sleep hygiene among residents.

Activation of ventral tegmental area vesicular GABA transporter (Vgat) neurons alleviates social defeat stress-induced anxiety in APP/PS1 mice

Introduction

Alzheimer's disease (AD) is a progressive neurodegenerative disease that results in cognitive impairment and is often accompanied by anxiety. In this study, we investigated whether the activation of VTA^Vgat neurons could reduce anxiety in APP/PS1 mice. We hypothesized that acute social defeat stress (SDS) would lead to anxiety in APP/PS1 mice, and that the activation of VTA^Vgat neurons would alleviate this anxiety.

Methods

We exposed APP/PS1 mice to acute SDS and assessed anxiety using the open field test and elevated plus-arm test. Activated VTA^Vgat neurons was tested by cfos staining. Sleep quality was detected using electroencephalogram after SDS or non-SDS procedure. Sleep duration, sleep latency, and non-rapid eye movement (NREM) percentage were analyzed. VTA^Vgat neurons were chemogenetically activated by deschloroclozapine.

Results

Our results showed that acute SDS led to anxiety in APP/PS1 mice, as evidenced by increased anxiety-related behaviors in the open field and elevated plus-arm tests. Activation of VTA^Vgat neurons by SDS led to an increase in sleep duration, primarily due to a decrease in sleep latency and an increase in NREMs. However, the quality of sleep was poor. Chemogenetical activation of VTA^Vgat neurons improved sleep quality and relieved SDS-induced anxiety. Furthermore, the anxiety state correlated negatively with sleep duration and NREM percentage and correlated positively with theta power density in APP/PS1 mice.

Discussion

Our study provides evidence that the activation of VTA^Vgat neurons alleviates SDS-induced anxiety in APP/PS1 mice, suggesting that poor sleep quality may exacerbate anxiety in AD. These findings may have important implications for the treatment of anxiety in AD, as targeting VTA^Vgat neurons could be a potential therapeutic approach.