TNFα G308A polymorphism is associated with resilience to sleep deprivation-induced psychomotor vigilance performance impairment in healthy young adults

Exploring Astrocyte-Mediated Mechanisms in Sleep Disorders and Comorbidity

Astrocytes, the most abundant cells in the brain, are integral to sleep regulation. In the context of a healthy neural environment, these glial cells exert a profound influence on the sleep-wake cycle, modulating both rapid eye movement (REM) and non-REM sleep phases. However, emerging literature underscores perturbations in astrocytic function as potential etiological factors in sleep disorders, either as protopathy or comorbidity. As known, sleep disorders significantly increase the risk of neurodegenerative, cardiovascular, metabolic, or psychiatric diseases. Meanwhile, sleep disorders are commonly screened as comorbidities in various neurodegenerative diseases, epilepsy, and others. Building on existing research that examines the role of astrocytes in sleep disorders, this review aims to elucidate the potential mechanisms by which astrocytes influence sleep regulation and contribute to sleep disorders in the varied settings of brain diseases. The review emphasizes the significance of astrocyte-mediated mechanisms in sleep disorders and their associated comorbidities, highlighting the need for further research.

Relationship between genetic polymorphisms of cytokines and self-reported sleep complaints and habitual caffeine consumption

Pro-inflammatory cytokines are involved in sleep-wake regulation and are associated with caffeine consumption. This is a cross-sectional study in 1023 active French workers investigating associations between self-reported sleep complaints (>3months) and total sleep time (TST) with nine single-nucleotide-polymorphisms (SNPs) including pro-inflammatory cytokines, according to caffeine consumption. Participants were characterized as low, moderate and high (0-50, 51-300, and >300 mg/day) caffeine consumers. After adjusting the odd ratios (OR) for age, gender, and smoking, the risk of sleep complaints was higher in subjects with genetic mutations in tumor necrosis factor alpha (TNF-α, rs 1800629) (ORa [95%CI] = 1.43 [1.07-1.92] for both G/A and A/A aggregate genotypes) or interleukin-1 beta (IL-1β, rs1143627) (ORa = 1.61 [1.08-2.44] for homozygous A/A genotype), and the risk was higher when subjects carry the mutations in TNF-α plus IL-1β regardless of caffeine consumption. When stratified with caffeine consumption, the risk of sleep complaints was higher in TNF-α A allele carriers in high caffeine consumers, and in homozygous A/A genotype of IL-1β in moderate and high consumers. None of the nine SNPs influence TST, with the exception of the mutation on CYP1A2 and only when stratified with caffeine consumption. Our results also indicated more caffeine side-effects when carrying mutation on IL1β. This study showed that polymorphisms in TNF-α and/or IL-1β influenced sleep complaints but did not influence total sleep time. This suggests that management of sleep complaints, which can be addressed by clinical interventions, should consider the influence of the genetic profile of pro-inflammatory cytokines.

Intricate role of sleep deprivation in modulating depression: focusing on BDNF, VEGF, serotonin, cortisol, and TNF-α

In this review article, we aimed to discuss intricate roles of SD in modulating depression in preclinical and clinical studies. Decades of research have shown the inconsistent effects of SD on depression, focusing on SD duration. However, inconsistent role of SD seems to be more complicated, and SD duration cannot be the only one factor. Regarding this issue, we chose some important factors involved in the effects of SD on cognitive functions and mood including brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), serotonin, cortisol, and tumor necrosis factor-alpha (TNF-α). It was concluded that SD has a wide-range of inconsistent effects on BDNF, VEGF, serotonin, and cortisol levels. It was noted that BDNF diurnal rhythm is significantly involved in the modulatory role of SD in depression. Furthermore, the important role of VEGF in blood-brain barrier permeability which is involved in modulating depression was discussed. It was also noted that there is a negative correlation between cortisol and BDNF that modulates depression. Eventually, it was concluded that TNF-α regulates sleep/wake cycle and is involved in the vulnerability to cognitive and behavioral impairments following SD. TNF-α also increases the permeability of the blood-brain barrier which is accompanied by depressive behavior. In sum, it was suggested that future studies should focus on these mechanisms/factors to better investigate the reasons behind intricate roles of SD in modulating depression.

Possible Neuropathology of Sleep Disturbance Linking to Alzheimer's Disease: Astrocytic and Microglial Roles

Sleep disturbances not only deteriorate Alzheimer’s disease (AD) progress by affecting cognitive states but also accelerate the neuropathological changes of AD. Astrocytes and microglia are the principal players in the regulation of both sleep and AD. We proposed that possible astrocyte-mediated and microglia-mediated neuropathological changes of sleep disturbances linked to AD, such as astrocytic adenosinergic A1, A2, and A3 regulation; astrocytic dopamine and serotonin; astrocyte-mediated proinflammatory status (TNFα); sleep disturbance-attenuated microglial CX3CR1 and P2Y12; microglial Iba-1 and astrocytic glial fibrillary acidic protein (GFAP); and microglia-mediated proinflammatory status (IL-1b, IL-6, IL-10, and TNFα). Furthermore, astrocytic and microglial amyloid beta (Aβ) and tau in AD were reviewed, such as astrocytic Aβ interaction in AD; astrocyte-mediated proinflammation in AD; astrocytic interaction with Aβ in the central nervous system (CNS); astrocytic apolipoprotein E (ApoE)-induced Aβ clearance in AD, as well as microglial Aβ clearance and aggregation in AD; proinflammation-induced microglial Aβ aggregation in AD; microglial-accumulated tau in AD; and microglial ApoE and TREM2 in AD. We reviewed astrocytic and microglial roles in AD and sleep, such as astrocyte/microglial-mediated proinflammation in AD and sleep; astrocytic ApoE in sleep and AD; and accumulated Aβ-triggered synaptic abnormalities in sleep disturbance. This review will provide a possible astrocytic and microglial mechanism of sleep disturbance linked to AD.

Roles for Sleep in Neural and Behavioral Plasticity: Reviewing Variation in the Consequences of Sleep Loss

Sleep is a vital physiological state that has been broadly conserved across the evolution of animal species. While the precise functions of sleep remain poorly understood, a large body of research has examined the negative consequences of sleep loss on neural and behavioral plasticity. While sleep disruption generally results in degraded neural plasticity and cognitive function, the impact of sleep loss can vary widely with age, between individuals, and across physiological contexts. Additionally, several recent studies indicate that sleep loss differentially impacts distinct neuronal populations within memory-encoding circuitry. These findings indicate that the negative consequences of sleep loss are not universally shared, and that identifying conditions that influence the resilience of an organism (or neuron type) to sleep loss might open future opportunities to examine sleep's core functions in the brain. Here, we discuss the functional roles for sleep in adaptive plasticity and review factors that can contribute to individual variations in sleep behavior and responses to sleep loss.

The Molecular Basis of Resilience: A Narrative Review

Resilience refers to the adaptability of a person - an ability to "bounce-back" from stressors. We question if resilience can be strengthened, potentially to decrease the risk of stress-related disorders. Unfortunately, the molecular origins of resilience are complicated and not yet well understood. In this review, we examine the various physiological biomarkers of resilience, including the associated genes, epigenetic changes, and protein biomarkers associated with resilient phenotypes. In addition to assessing biomarkers that may indicate higher levels of resilience, we also review at length the many biomarkers that confer lower levels of resilience and may lead to disorders of low resilience, such as anxiety and depression. This large and encompassing review may help to identify the possible therapeutic targets of resilience. Hopefully these studies will lead to a future where stress-related disorders can be prevented, rather than treated.

Genetic Variants Associated With Resilience in Human and Animal Studies

Resilience is broadly defined as the ability to maintain or regain functioning in the face of adversity and is influenced by both environmental and genetic factors. The identification of specific genetic factors and their biological pathways underpinning resilient functioning can help in the identification of common key factors, but heterogeneities in the operationalisation of resilience have hampered advances. We conducted a systematic review of genetic variants associated with resilience to enable the identification of general resilience mechanisms. We adopted broad inclusion criteria for the definition of resilience to capture both human and animal model studies, which use a wide range of resilience definitions and measure very different outcomes. Analyzing 158 studies, we found 71 candidate genes associated with resilience. OPRM1 (Opioid receptor mu 1), NPY (neuropeptide Y), CACNA1C (calcium voltage-gated channel subunit alpha1 C), DCC (deleted in colorectal carcinoma), and FKBP5 (FKBP prolyl isomerase 5) had both animal and human variants associated with resilience, supporting the idea of shared biological pathways. Further, for OPRM1, OXTR (oxytocin receptor), CRHR1 (corticotropin-releasing hormone receptor 1), COMT (catechol-O-methyltransferase), BDNF (brain-derived neurotrophic factor), APOE (apolipoprotein E), and SLC6A4 (solute carrier family 6 member 4), the same allele was associated with resilience across divergent resilience definitions, which suggests these genes may therefore provide a starting point for further research examining commonality in resilience pathways.

Predictors of interindividual differences in vulnerability to neurobehavioral consequences of chronic partial sleep restriction

Interindividual differences in the neurobehavioral response to sleep loss are largely unexplained and phenotypic in nature. Numerous factors have been examined as predictors of differential response to sleep loss, but none have yielded a comprehensive view of the phenomenon. The present study examines the impact of baseline factors, habitual sleep-wake patterns, and homeostatic response to sleep loss on accrued deficits in psychomotor vigilance during chronic partial sleep restriction (SR), in a total of 306 healthy adults that participated in one of three independent laboratory studies. Findings indicate no significant impact of personality, academic intelligence, subjective reports of chronotype, sleepiness and fatigue, performance on working memory, and demographic factors such as sex, ethnicity, and body mass index, on neurobehavioral vulnerability to the negative effects of sleep loss. Only superior baseline performance on the psychomotor vigilance test and ability to sustain wakefulness on the maintenance of wakefulness test were associated with relative resilience to decrements in vigilant attention during SR. Interindividual differences in vulnerability to the effects of sleep loss were not accounted for by prior sleep history, habitual sleep patterns outside of the laboratory, baseline sleep architecture, or homeostatic sleep response during chronic partial SR. A recent theoretical model proposed that sleep-wake modulation may be influenced by competing internal and external demands which may promote wakefulness despite homeostatic and circadian signals for sleep under the right circumstances. Further research is warranted to examine the possibility of interindividual differences in the ability to prioritize external demands for wakefulness in the face of mounting pressure to sleep.

Genetics and Cognitive Vulnerability to Sleep Deprivation in Healthy Subjects: Interaction of ADORA2A, TNF-α and COMT Polymorphisms

Several genetic polymorphisms differentiate between healthy individuals who are more cognitively vulnerable or resistant during total sleep deprivation (TSD). Common metrics of cognitive functioning for classifying vulnerable and resilient individuals include the Psychomotor Vigilance Test (PVT), Go/noGo executive inhibition task, and subjective daytime sleepiness. We evaluated the influence of 14 single-nucleotide polymorphisms (SNPs) on cognitive responses during total sleep deprivation (continuous wakefulness for 38 h) in 47 healthy subjects (age 37.0 ± 1.1 years). SNPs selected after a literature review included SNPs of the adenosine-A2A receptor gene (including the most studied rs5751876), pro-inflammatory cytokines (TNF-α, IL1-β, IL-6), catechol-O-methyl-transferase (COMT), and PER3. Subjects performed a psychomotor vigilance test (PVT) and a Go/noGo-inhibition task, and completed the Karolinska Sleepiness Scale (KSS) every 6 h during TSD. For PVT lapses (reaction time >500 ms), an interaction between SNP and SDT (p < 0.05) was observed for ADORA2A (rs5751862 and rs2236624) and TNF-α (rs1800629). During TSD, carriers of the A allele for ADORA2A (rs5751862) and TNF-α were significantly more impaired for cognitive responses than their respective ancestral G/G genotypes. Carriers of the ancestral G/G genotype of ADORA2A rs5751862 were found to be very similar to the most resilient subjects for PVT lapses and Go/noGo commission errors. Carriers of the ancestral G/G genotype of COMT were close to the most vulnerable subjects. ADORA2A (rs5751862) was significantly associated with COMT (rs4680) (p = 0.001). In conclusion, we show that genetic polymorphisms in ADORA2A (rs5751862), TNF-α (rs1800629), and COMT (rs4680) are involved in creating profiles of high vulnerability or high resilience to sleep deprivation. (NCT03859882).

Genetic Markers of Differential Vulnerability to Sleep Loss in Adults

In this review, we discuss reports of genotype-dependent interindividual differences in phenotypic neurobehavioral responses to total sleep deprivation or sleep restriction. We highlight the importance of using the candidate gene approach to further elucidate differential resilience and vulnerability to sleep deprivation in humans, although we acknowledge that other omics techniques and genome-wide association studies can also offer insights into biomarkers of such vulnerability. Specifically, we discuss polymorphisms in adenosinergic genes (ADA and ADORA2A), core circadian clock genes (BHLHE41/DEC2 and PER3), genes related to cognitive development and functioning (BDNF and COMT), dopaminergic genes (DRD2 and DAT), and immune and clearance genes (AQP4, DQB1*0602, and TNFα) as potential genetic indicators of differential vulnerability to deficits induced by sleep loss. Additionally, we review the efficacy of several countermeasures for the neurobehavioral impairments induced by sleep loss, including banking sleep, recovery sleep, caffeine, and naps. The discovery of reliable, novel genetic markers of differential vulnerability to sleep loss has critical implications for future research involving predictors, countermeasures, and treatments in the field of sleep and circadian science.

Posttraumatic stress disorder symptoms and neurocognitive functioning in fire fighters: The mediating role of sleep problems and resilience

BACKGROUND

Firefighters are often exposed to terrible and dangerous scenes due to their duties, and thus have a high risk of developing posttraumatic stress disorder(PTSD). The purpose of the study is to examine the relationship between PTSD symptoms, sleep problems, resilience and neurocognitive functioning of firefighters, and to identify the sequential mediating effects of sleep problems and resilience on the relationship between PTSD symptoms and neurocognitive functioning (especially psychomotor speed and processing speed).

METHODS

Data were collected from 325 firefighters in eight fire departments in four regions of Korea. Subjects performed neurocognitive function tests and completed the following questionnaires: Primary Care PTSD Screening, Pittsburgh Sleep Quality Index-K and Connor-Davidson Resilience Scale-2. The correlation and dual mediation effects were analysed using SPSS 22.0 program and PROCESS macro 3.4 program.

RESULTS

PTSD symptoms, neurocognitive functioning, sleep problems and resilience were significantly correlated with each other. In the sequential mediation model, the relationship between PTSD and psychomotor speed/processing speed was sequentially mediated by sleep problems and resilience after adjusting for demographic variables.

CONCLUSIONS

The PTSD symptoms of firefighters were related to a sequential link between sleep problems, low resilience and decreased neurocognitive function. These findings could serve as a basis for more effective and integrated interventional strategies for facilitating better neurocognitive functioning in firefighters.

Genetic Determinants of Neurobehavioral Responses to Caffeine Administration during Sleep Deprivation: A Randomized, Cross Over Study (NCT03859882)

This study investigated whether four single nucleotide polymorphisms (SNPs) moderated caffeine effects on vigilance and performance in a double-blind and crossover total sleep deprivation (TSD) protocol in 37 subjects. In caffeine (2 × 2.5 mg/kg/24 h) or placebo-controlled condition, subjects performed a psychomotor vigilance test (PVT) and reported sleepiness every six hours (Karolinska sleepiness scale (KSS)) during TSD. EEG was also analyzed during the 09:15 PVT. Carriers of the TNF-α SNP A allele appear to be more sensitive than homozygote G/G genotype to an attenuating effect of caffeine on PVT lapses during sleep deprivation only because they seem more degraded, but they do not perform better as a result. The A allele carriers of COMT were also more degraded and sensitive to caffeine than G/G genotype after 20 h of sleep deprivation, but not after 26 and 32 h. Regarding PVT reaction time, ADORA2A influences the TSD effect but not caffeine, and PER3 modulates only the caffeine effect. Higher EEG theta activity related to sleep deprivation was observed in mutated TNF-α, PER3, and COMT carriers, in the placebo condition particularly. In conclusion, there are genetic influences on neurobehavioral impairments related to TSD that appear to be attenuated by caffeine administration. (NCT03859882).

The Iowa Resistance to Sleeplessness Test (iREST)

INTRODUCTION

Despite considerable individual differences in the vulnerability vs resistance to effects of sleep loss, there is no practical self-report tool to predict these differences across domains and only limited evidence whether they are general or domain-specific. To address this need, we developed the Iowa Resistance to Sleeplessness Test (iREST).

METHODS

A construct-validation approach was employed. During the substantive phase, self-report items were generated to capture vulnerability vs resistance to sleep loss across various psycho-behavioral domains. During the structural phase, analyses identified the underlying factor structure and examined reliability of individual scale scores. Finally, the external phase used convergent and discriminant analyses to evaluate the factors in light of related sleep and personality measures, and tested criterion validity of the scale scores in predicting neurocognitive and affective responses to experimental sleep restriction (Total N = 1018).

RESULTS

Analyses yielded discriminant and reliable scale scores that reflected resistance across cognitive, affective, and somatic responses, while also marking a general resistance factor. Convergent and discriminant probes revealed moderate associations of scale scores with daytime sleepiness and sleep-related distress, but small to negligible associations with other measures of sleep behavior, perceptions, and personality. Critically, criterion analyses yielded validity evidence for predicting cognitive and affective impairments in response to experimental sleep loss.

CONCLUSION

Scores on the iREST show validity in capturing cognitive and affective resistance to moderate sleep loss among young adults, supporting its further exploration as a practical tool for predicting behavior due to lost sleep.

TNFα G308A genotype, resilience to sleep deprivation, and the effect of caffeine on psychomotor vigilance performance in a randomized, double-blind, placebo-controlled, crossover study

The TNFα G308A gene polymorphism has been reported to influence performance impairment during total sleep deprivation (TSD). We investigated this effect in a randomized, double-blind, crossover laboratory study of repeated exposure to 48 h TSD with caffeine administration at different doses. In a retrospective analysis, we replicated the finding that the A allele of TNFα G308A, found in 4 of 12 study participants, confers resilience to performance impairment during TSD. There was no evidence of an interaction of TNFα genotype with the beneficial effect of caffeine (200 or 300 mg) on performance during TSD, suggesting distinct underlying mechanisms.

Genotyping on blood and buccal cells using loop-mediated isothermal amplification in healthy humans

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Genetic variations contribute to phenotypic individual vulnerabilities to sleep debt.

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LAMP-MC is a recently developed method to characterize Single Nucleotide Polymorphism.

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Detection is performed directly from whole blood or buccal cells.

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LAMP-MC method produced specific melting curves for 5 sleep debt-related SNPs.

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High concordance of results was observed between LAMP-MC and Taqman referent method.

Genetic variations contribute to phenotypic individual vulnerabilities to sleep debt, particularly for five single nucleotide polymorphisms (SNPs). Loop-mediated isothermal amplification and melting curve analysis (LAMP-MC) is a recently developed method to characterize SNPs. The aim of present study was to evaluate the LAMP-MC method on blood and buccal cells for detection of five SNPs of interest in healthy humans.

We first analyzed signals obtained from LAMP-MC method on 42 samples. Then we compared the results with those of referent TaqMan method.

The LAMP-MC method produced specific melting curves for the five SNPs. A high concordance of genotyping results was observed between the two methods for rs5751876_ADORA2A, rs1800629_TNF-α, rs73598374_ADA and rs228697_PER3 in blood and saliva (Cohen’s kappa coefficient >0.80). A good agreement ( = 0.61) was observed for rs4680_COMT in blood only.

LAMP-MC is a simple and reliable method to study genetic influences on health, sleep debt-related performance impairments and countermeasures.

Trait-like vulnerability of higher-order cognition and ability to maintain wakefulness during combined sleep restriction and circadian misalignment

STUDY OBJECTIVES

Determine stability of individual differences in executive function, cognitive processing speed, selective visual attention, and maintenance of wakefulness during simulated sustained operations with combined sleep restriction and circadian misalignment.

METHODS

Twenty healthy adults (eight female), aged 25.7 (±4.2 SD), body mass index (BMI) 22.3 (±2.1) kg/m2 completed an 18-day protocol twice. Participants maintained habitual self-selected 8-hour sleep schedules for 2 weeks at home prior to a 4-day laboratory visit that included one sleep opportunity per day: 8 hours on night 1, 3 hours on night 2, and 3 hours on mornings 3 and 4. After 3 days of unscheduled sleep at home, participants repeated the entire protocol. Stability and task dependency of individual differences in performance were quantified by intra-class correlation coefficients (ICC) and Kendall's Tau, respectively.

RESULTS

Performance on Stroop, Visual Search, and the Maintenance of Wakefulness Test were highly consistent within individuals during combined sleep restriction and circadian misalignment. Individual differences were trait-like as indicated by ICCs (0.54-0.96) classified according to standard criteria as moderate to almost perfect. Individual differences on other performance tasks commonly reported in sleep studies showed fair to almost perfect ICCs (0.22-0.94). Kendall's rank correlations showed that individual vulnerability to sleep restriction and circadian misalignment varied by task and by metric within a task.

CONCLUSIONS

Consistent vulnerability of higher-order cognition and maintenance of wakefulness to combined sleep restriction and circadian misalignment has implications for the development of precision countermeasure strategies for workers performing safety-critical tasks, e.g. military, police, health care workers and emergency responders.

Sleep deprivation, vigilant attention, and brain function: a review

Vigilant attention is a major component of a wide range of cognitive performance tasks. Vigilant attention is impaired by sleep deprivation and restored after rest breaks and (more enduringly) after sleep. The temporal dynamics of vigilant attention deficits across hours and days are driven by physiologic, sleep regulatory processes-a sleep homeostatic process and a circadian process. There is also evidence of a slower, allostatic process, which modulates the sleep homeostatic setpoint across days and weeks and is responsible for cumulative deficits in vigilant attention across consecutive days of sleep restriction. There are large inter-individual differences in vulnerability to sleep loss, and these inter-individual differences constitute a pronounced human phenotype. However, this phenotype is multi-dimensional; vulnerability in terms of vigilant attention impairment can be dissociated from vulnerability in terms of other cognitive processes such as attentional control. The vigilance decrement, or time-on-task effect-a decline in performance across the duration of a vigilant attention task-is characterized by progressively increasing response variability, which is exacerbated by sleep loss. This variability, while crucial to understanding the impact of sleep deprivation on performance in safety-critical tasks, is not well explained by top-down regulatory mechanisms, such as the homeostatic and circadian processes. A bottom-up, neuronal pathway-dependent mechanism involving use-dependent, local sleep may be the main driver of response variability. This bottom-up mechanism may also explain the dissociation between cognitive processes with regard to trait vulnerability to sleep loss.

Sleep and cardiovascular disease: Emerging opportunities for psychology

Sleep disturbances and disorders have been implicated in cardiovascular morbidity and mortality. Converging evidence suggests that psychosocial factors that confer risk or resilience to cardiovascular disease (CVD) are also related to sleep. Profound differences in sleep among racial/ethnic minorities compared with non-Hispanic Whites in the United States suggest that sleep, and its interplay with psychosocial factors, may contribute to observed disparities in CVD and in health and functioning more broadly. Less understood is the extent to which sleep and psychosocial factors interact to influence the pathophysiology and clinical course of CVD. This article reviews observational and experimental evidence linking short sleep duration and insomnia, both modifiable sleep disturbances, to CVD, including key physiological mechanisms. Also reviewed is evidence of significant interrelationships among sleep, race/ethnicity, and psychosocial factors known to confer risk or resilience to CVD, including depression, psychological stress, and close interpersonal relationships. It is proposed that a transdisciplinary research framework that integrates knowledge, methods, and measures from the fields of psychology and sleep research may be used to catalyze advances in the prevention and treatment of CVD. Also discussed are promising new directions, expected challenges, and the importance of training in transdisciplinary science and research approaches. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Classifying attentional vulnerability to total sleep deprivation using baseline features of Psychomotor Vigilance Test performance

There are strong individual differences in performance during sleep deprivation. We assessed whether baseline features of Psychomotor Vigilance Test (PVT) performance can be used for classifying participants’ relative attentional vulnerability to total sleep deprivation. In a laboratory, healthy adults (n = 160, aged 18–30 years) completed a 10-min PVT every 2 h while being kept awake for ≥24 hours. Participants were categorized as vulnerable (n = 40), intermediate (n = 80), or resilient (n = 40) based on their number of PVT lapses during one night of sleep deprivation. For each baseline PVT (taken 4–14 h after wake-up time), a linear discriminant model with wrapper-based feature selection was used to classify participants’ vulnerability to subsequent sleep deprivation. Across models, classification accuracy was about 70% (range 65–76%) using stratified 5-fold cross validation. The models provided about 78% sensitivity and 86% specificity for classifying resilient participants, and about 70% sensitivity and 89% specificity for classifying vulnerable participants. These results suggest features derived from a single 10-min PVT at baseline can provide substantial, but incomplete information about a person’s relative attentional vulnerability to total sleep deprivation. In the long term, modeling approaches that incorporate baseline performance characteristics can potentially improve personalized predictions of attentional performance when sleep deprivation cannot be avoided.

Drowsiness measures for commercial motor vehicle operations

Timely detection of drowsiness in Commercial Motor Vehicle (C MV) operations is necessary to reduce drowsiness-related CMV crashes. This is relevant for manual driving and, paradoxically, even more so with increasing levels of driving automation. Measures available for drowsiness detection vary in reliability, validity, usability, and effectiveness. Passively recorded physiologic measures such as electroencephalography (EEG) and a variety of ocular parameters tend to accurately identify states of considerable drowsiness, but are limited in their potential to detect lower levels of drowsiness. They also do not correlate well with measures of driver performance. Objective measures of vigilant attention performance capture drowsiness reliably, but they require active driver involvement in a performance task and are prone to confounds from distraction and (lack of) motivation. Embedded performance measures of actual driving, such as lane deviation, have been found to correlate with physiologic and vigilance performance measures, yet to what extent drowsiness levels can be derived from them reliably remains a topic of investigation. Transient effects from external circumstances and behaviors - such as task load, light exposure, physical activity, and caffeine intake - may mask a driver's underlying state of drowsiness. Also, drivers differ in the degree to which drowsiness affects their driving performance, based on trait vulnerability as well as age. This paper provides a broad overview of the current science pertinent to a range of drowsiness measures, with an emphasis on those that may be most relevant for CMV operations. There is a need for smart technologies that in a transparent manner combine different measurement modalities with mathematical representations of the neurobiological processes driving drowsiness, that account for various mediators and confounds, and that are appropriately adapted to the individual driver. The research for and development of such technologies requires a multi-disciplinary approach and significant resources, but is technically within reach.

Time-on-Task Effect During Sleep Deprivation in Healthy Young Adults Is Modulated by Dopamine Transporter Genotype

Study Objectives

The time-on-task (TOT) effect and total sleep deprivation (TSD) have similar effects on neurobehavioral functioning, including increased performance instability during tasks requiring sustained attention. The TOT effect is exacerbated by TSD, suggesting potentially overlapping mechanisms. We probed these mechanisms by investigating genotype-phenotype relationships on psychomotor vigilance test (PVT) performance for 3 a-priori selected genes previously linked to the TOT effect and/or TSD: dopamine active transporter 1 (DAT1), catechol-O-methyltransferase (COMT), and tumor necrosis factor alpha (TNFα).

Methods

N = 82 healthy adults participated in 1 of 3 laboratory studies. A 10-min PVT was administered repeatedly during 38 h of TSD. We assessed changes in response time (RT) across each minute of the PVT as a function of time awake and genotype. Additionally, cumulative relative RT frequency distributions were constructed to examine changes in performance from the first to the second 5 min of the PVT as a function of genotype.

Results

DAT1, COMT, and TNFα were associated with differences in the build-up of the TOT effect across the 10-min PVT. DAT1 additionally modulated the interaction between TSD and the TOT effect. Subjects homozygous for the DAT1 10-repeat allele were relatively protected against TOT deficits on the PVT during TSD compared to carriers of the 9-repeat allele.

Conclusions

DAT1 is known to regulate dopamine reuptake and is highly expressed in the striatum. Our results implicate striatal dopamine in mechanisms involved in performance instability that appear to be common to TSD and the TOT effect. Furthermore, DAT1 may be a candidate biomarker of resilience to the build-up of performance impairment across TOT due to TSD.

Astrocyte expression of the Drosophila TNF-alpha homologue, Eiger, regulates sleep in flies

Sleep contributes to cognitive functioning and is sufficient to alter brain morphology and function. However, mechanisms underlying sleep regulation remain poorly understood. In mammals, tumor necrosis factor-alpha (TNFα) is known to regulate sleep, and cytokine expression may represent an evolutionarily ancient mechanism in sleep regulation. Here we show that the Drosophila TNFα homologue, Eiger, mediates sleep in flies. We show that knockdown of Eiger in astrocytes, but not in neurons, significantly reduces sleep duration, and total loss-of-function reduces the homeostatic response to sleep loss. In addition, we show that neuronal, but not astrocyte, expression of the TNFα receptor superfamily member, Wengen, is necessary for sleep deprivation-induced homeostatic response and for mediating increases in sleep in response to human TNFα. These data identify a novel astrocyte-to-neuron signaling mechanism in the regulation of sleep homeostasis and show that the Drosophila cytokine, Eiger, represents an evolutionarily conserved mechanism of sleep regulation across phylogeny.

Every animal sleeps, from fruit flies to humans. However, the function of sleep is still currently unknown. Identifying conserved mechanisms of sleep regulation in evolutionarily ancient organisms may help us to understand the function of sleep. Therefore, we have examined whether Eiger, the homologue of the cytokine tumor necrosis factor-alpha (TNFα), regulates sleep in the fruit fly as it does in higher mammals. Cytokines are inflammatory molecules and are typically elevated following infection or fever and may contribute to increased sleepiness when sick. We found that, in the fruit fly, Eiger regulates sleep duration just like TNFα does in mammals: increasing cytokine levels increased sleep duration while decreasing Eiger reduced sleep. In addition, we found that Eiger expression in glial astrocytes, is responsible for the alteration in sleep duration. We also examined the necessity of Eiger receptor activation on neurons and found that astrocyte-to-neuron communication was required for regulating the normal increases in sleep following sleep deprivation. These data show that a novel cytokine mechanism regulates sleep in flies and mammals, and provides insight into conserved roles of astrocytes in sleep behavior.

Sleep Quality and Chronotype Differences between Elite Athletes and Non-Athlete Controls

Previous research has found that elite athletes have insufficient sleep, yet the specific kinds of sleep disturbances occurring as compared to a control group are limited. Here we compare the subjective sleep quality and chronotype of elite athletes to a control group of non-athlete good sleepers. Sixty-three winter Canadian National Team athletes (mean age 26.0 ± 0.0; 32% females) completed the Pittsburgh Sleep Quality Index (PSQI) and the Athlete Morningness Eveningness Scale. They were compared to 83 healthy, non-athlete, good-sleeper controls (aged 27.3 ± 3.7; 51% females) who completed the PSQI and the Composite Scale of Morningness. The elite athletes reported poorer sleep quality (PSQI global score 5.0 ± 2.6) relative to the controls (PSQI global score 2.6 ± 1.3), despite there being no group difference in self-reported sleep duration (athletes 8.1 ± 1.0 h; controls 8.0 ± 0.7 h). Further, athletes’ chronotype distribution showed a greater skew toward morningness, despite there being no group differences in self-reported usual bedtime and wake time. These results suggest that a misalignment of sleep times with circadian preference could contribute to poorer sleep quality in elite athletes.

Exploring gene expression biomarker candidates for neurobehavioral impairment from total sleep deprivation

Background

Although sleep deprivation is associated with neurobehavioral impairment that may underlie significant risks to performance and safety, there is no reliable biomarker test to detect dangerous levels of impairment from sleep loss in humans. This study employs microarrays and bioinformatics analyses to explore candidate gene expression biomarkers associated with total sleep deprivation (TSD), and more specifically, the phenotype of neurobehavioral impairment from TSD. Healthy adult volunteers were recruited to a sleep laboratory for seven consecutive days (six nights). After two Baseline nights of 10 h time in bed, 11 subjects underwent an Experimental phase of 62 h of continuous wakefulness, followed by two Recovery nights of 10 h time in bed. Another six subjects underwent a well-rested Control condition of 10 h time in bed for all six nights. Blood was drawn for measuring gene expression on days two, four, and six at 4 h intervals from 08:00 to 20:00 h, corresponding to 12 timepoints across one Baseline, one Experimental, and one Recovery day.

Results

Altogether 212 genes changed expression in response to the TSD Treatment, with most genes exhibiting down-regulation during TSD. Also, 28 genes were associated with neurobehavioral impairment as measured by the Psychomotor Vigilance Test. The results support previous findings associating TSD with the immune response and ion signaling, and reveal novel candidate biomarkers such as the Speedy/RINGO family of cell cycle regulators.

Conclusions

This study serves as an important step toward understanding gene expression changes during sleep deprivation. In addition to exploring potential biomarkers for TSD, this report presents novel candidate biomarkers associated with lapses of attention during TSD. Although further work is required for biomarker validation, analysis of these genes may aid fundamental understanding of the impact of TSD on neurobehavioral performance.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-4664-3) contains supplementary material, which is available to authorized users.

Interindividual variability in neurobehavioral response to sleep loss: A comprehensive review

Stable trait-like responding is well established for neurobehavioral performance measures across repeated exposures to total sleep deprivation and partial chronic sleep restriction. These observed phenotypes are task-dependent, suggesting that there are distinct cognitive profiles of responding with differential vulnerability to sleep loss within the same individual. Numerous factors have been investigated as potential markers of phenotypic vulnerability to the effects of sleep loss but none fully account for this phenomenon. Observed interindividual differences in performance during extended wakefulness may be driven by underlying deficits in the wake-promoting system resulting in greater performance instability due to failure to counteract increased homeostatic pressure. Further work would benefit from a systems approach to the study of interindividual vulnerability in which behavioral, neurobiological, and genetic data are integrated in a larger framework delineating the relationships between genes, proteins, neurobiology, and behavior.

Insufficient Sleep Syndrome: Is it time to classify it as a major noncommunicable disease?

Over the last three to four decades, it has been observed that the average total number of hours of sleep obtained per night by normal individuals have decreased. Concomitantly, global figures indicate that insufficient sleep is associated with serious adverse health and social outcomes. Moreover, insufficient sleep has been linked to seven of the fifteen leading causes of death. Additionally, current evidence suggests that sleep plays a significant role in determining cognitive performance and workplace productivity. There is a great need for a systematic analysis of the economic impact of insufficient sleep, particularly given current evidence that this phenomenon, as well as the poor sleep hygiene practices which produce it, is increasing worldwide. This paper takes the view that health authorities around the world need to raise the general awareness of benefits of sleep. There is considerable scope for research into both the public health impact as well as the macroeconomic consequences of insufficient sleep syndrome (ISS). Additionally, various models which estimate the undiagnosed burden of ISS on the GDP (gross domestic product) are needed to prioritize health issues and to highlight the national policies that are necessary to combat this medical problem. Sleep insufficiency has been declared to be a 'public health epidemic'; therefore, we propose ISS as a potential noncommunicable disease. This review elaborates on this topic further, exploring the causes and consequences of insufficient sleep, and thus providing a perspective on the policies that are needed as well as the research that will be required to support and justify these policies.

Cardiopulmonary coupling spectrogram as an ambulatory clinical biomarker of sleep stability and quality in health, sleep apnea, and insomnia

STUDY OBJECTIVES

Ambulatory tracking of sleep and sleep pathology is rapidly increasing with the introduction of wearable devices. The objective of this study was to evaluate a wearable device which used novel computational analysis of the electrocardiogram (ECG), collected over multiple nights, as a method to track the dynamics of sleep quality in health and disease.

METHODS

This study used the ECG as a primary signal, a wearable device, the M1, and an analysis of cardiopulmonary coupling to estimate sleep quality. The M1 measures trunk movements, the ECG, body position, and snoring vibrations. Data from three groups of patients were analyzed: healthy participants and people with sleep apnea and insomnia, obtained from multiple nights of recording. Analysis focused on summary measures and night-to-night variability, specifically the intraclass coefficient.

RESULTS

Data were collected from 10 healthy participants, 18 people with positive pressure-treated sleep apnea, and 20 people with insomnia, 128, 65, and 121 nights, respectively. In any participant, all nights were consecutive. High-frequency coupling (HFC), the signal biomarker of stable breathing and stable sleep, showed high intraclass coefficients (ICCs) in healthy participants and people with sleep apnea (0.83, 0.89), but only 0.66 in people with insomnia. The only statistically significant difference between weekday and weekend in healthy subjects was HFC duration: 242.8 ± 53.8 vs. 275.8 ± 57.1 minutes (89 vs. 39 total nights), F(1,126) = 9.86, p = .002.

CONCLUSIONS

The M1 and similar wearable devices provide new opportunities to measure sleep in dynamic ways not possible before. These measurements can yield new biological insights and aid clinical management.

Catechol-O-methyltransferase (COMT) genotype affects cognitive control during total sleep deprivation

Adaptive decision making is profoundly impaired by total sleep deprivation (TSD). This suggests that TSD impacts fronto-striatal pathways involved in cognitive control, where dopamine is a key neuromodulator. In the prefrontal cortex (PFC), dopamine is catabolized by the enzyme catechol-O-methyltransferase (COMT). A functional polymorphism (Val158Met) influences COMT's enzymatic activity, resulting in markedly different levels of prefrontal dopamine. We investigated the effect of this polymorphism on adaptive decision making during TSD. Sixty-six healthy young adults participated in one of two in-laboratory studies. After a baseline day, subjects were randomized to either a TSD group (n = 32) with 38 h or 62 h of extended wakefulness or a well-rested control group (n = 34) with 10 h nighttime sleep opportunities. Subjects performed a go/no-go reversal learning (GNGr) task at well-rested baseline and again during TSD or equivalent control. During the task, subjects were required to learn stimulus-response relationships from accuracy feedback. The stimulus-response relationships were reversed halfway through the task, which required subjects to learn the new stimulus-response relationships from accuracy feedback. Performance on the GNGr task was quantified by discriminability (d') between go and no-go stimuli before and after the stimulus-response reversal. GNGr performance did not differ between COMT genotypes when subjects were well-rested. However, TSD exposed a significant vulnerability to adaptive decision making impairment in subjects with the Val allele. Our results indicate that sleep deprivation degrades cognitive control through a fronto-striatal, dopaminergic mechanism.

Sleep Deprivation Diminishes Attentional Control Effectiveness and Impairs Flexible Adaptation to Changing Conditions

Insufficient sleep is a global public health problem resulting in catastrophic accidents, increased mortality, and hundreds of billions of dollars in lost productivity. Yet the effect of sleep deprivation (SD) on decision making and performance is often underestimated by fatigued individuals and is only beginning to be understood by scientists. The deleterious impact of SD is frequently attributed to lapses in vigilant attention, but this account fails to explain many SD-related problems, such as loss of situational awareness and perseveration. Using a laboratory study protocol, we show that SD individuals can maintain information in the focus of attention and anticipate likely correct responses, but their use of such a top-down attentional strategy is less effective at preventing errors caused by competing responses. Moreover, when the task environment requires flexibility, performance under SD suffers dramatically. The impairment in flexible shifting of attentional control we observed is distinct from lapses in vigilant attention, as corroborated by the specificity of the influence of a genetic biomarker, the dopaminergic polymorphism DRD2 C957T. Reduced effectiveness of top-down attentional control under SD, especially when conditions require flexibility, helps to explain maladaptive performance that is not readily explained by lapses in vigilant attention.

Tumor necrosis factor alpha in sleep regulation

This review details tumor necrosis factor alpha (TNF) biology and its role in sleep, and describes how TNF medications influence sleep/wake activity. Substantial evidence from healthy young animals indicates acute enhancement or inhibition of endogenous brain TNF respectively promotes and inhibits sleep. In contrast, the role of TNF in sleep in most human studies involves pathological conditions associated with chronic elevations of systemic TNF and disrupted sleep. Normalization of TNF levels in such patients improves sleep. A few studies involving normal healthy humans and their TNF levels and sleep are consistent with the animal studies but are necessarily more limited in scope. TNF can act on established sleep regulatory circuits to promote sleep and on the cortex within small networks, such as cortical columns, to induce sleep-like states. TNF affects multiple synaptic functions, e.g., its role in synaptic scaling is firmly established. The TNF-plasticity actions, like its role in sleep, can be local network events suggesting that sleep and plasticity share biochemical regulatory mechanisms and thus may be inseparable from each other. We conclude that TNF is involved in sleep regulation acting within an extensive tightly orchestrated biochemical network to niche-adapt sleep in health and disease.

Signal-to-Noise Ratio in PVT Performance as a Cognitive Measure of the Effect of Sleep Deprivation on the Fidelity of Information Processing

Study Objectives

There is a long-standing debate about the best way to characterize performance deficits on the psychomotor vigilance test (PVT), a widely used assay of cognitive impairment in human sleep deprivation studies. Here, we address this issue through the theoretical framework of the diffusion model and propose to express PVT performance in terms of signal-to-noise ratio (SNR).

Methods

From the equations of the diffusion model for one-choice, reaction-time tasks, we derived an expression for a novel SNR metric for PVT performance. We also showed that LSNR-a commonly used log-transformation of SNR-can be reasonably well approximated by a linear function of the mean response speed, LSNRapx. We computed SNR, LSNR, LSNRapx, and number of lapses for 1284 PVT sessions collected from 99 healthy young adults who participated in laboratory studies with 38 hr of total sleep deprivation.

Results

All four PVT metrics captured the effects of time awake and time of day on cognitive performance during sleep deprivation. The LSNR had the best psychometric properties, including high sensitivity, high stability, high degree of normality, absence of floor and ceiling effects, and no bias in the meaning of change scores related to absolute baseline performance.

Conclusions

The theoretical motivation of SNR and LSNR permits quantitative interpretation of PVT performance as an assay of the fidelity of information processing in cognition. Furthermore, with a conceptual and statistical meaning grounded in information theory and generalizable across scientific fields, LSNR in particular is a useful tool for systems-integrated fatigue risk management.

Functional Polymorphisms in Dopaminergic Genes Modulate Neurobehavioral and Neurophysiological Consequences of Sleep Deprivation

Sleep deprivation impairs cognitive performance and reliably alters brain activation in wakefulness and sleep. Nevertheless, the molecular regulators of prolonged wakefulness remain poorly understood. Evidence from genetic, behavioral, pharmacologic and imaging studies suggest that dopaminergic signaling contributes to the behavioral and electroencephalographic (EEG) consequences of sleep loss, although direct human evidence thereof is missing. We tested whether dopamine neurotransmission regulate sustained attention and evolution of EEG power during prolonged wakefulness. Here, we studied the effects of functional genetic variation in the dopamine transporter (DAT1) and the dopamine D₂ receptor (DRD2) genes, on psychomotor performance and standardized waking EEG oscillations during 40 hours of wakefulness in 64 to 82 healthy volunteers. Sleep deprivation consistently enhanced sleepiness, lapses of attention and the theta-to-alpha power ratio (TAR) in the waking EEG. Importantly, DAT1 and DRD2 genotypes distinctly modulated sleep loss-induced changes in subjective sleepiness, PVT lapses and TAR, according to inverted U-shaped relationships. Together, the data suggest that genetically determined differences in DAT1 and DRD2 expression modulate functional consequences of sleep deprivation, supporting the hypothesis that striato-thalamo-cortical dopaminergic pathways modulate the neurobehavioral and neurophysiological consequences of sleep loss in humans.

Effects of partial sleep deprivation on reaction time in anesthesiologists

BACKGROUND

Fatigue in anesthesiologists may have implications that extend beyond individual well-being.

AIM

The aim of the present study was to evaluate the impact of sleep deprivation on the reaction time in anesthesiologists either after an overnight call or regular working hours. Moderation of this effect by coping strategies was observed.

METHODS

Psychomotor vigilance test was used to assess reaction time in 23 anesthesiologists at two time-points: (i) on a regular non-call day and (ii) after a 17-h in-house call. Student's paired t-test was used to compare Psychomotor Vigilance Task data at these two moments. Change score regression was performed to determine the association between coping strategies, assessed using the Coping Strategy Indicator instrument, and decline in reaction time after night call.

RESULTS

Twenty-one colleagues completed the psychomotor vigilance test measurements after two decided to end their participation for personal reasons. Post-call psychomotor vigilance test mean reaction time decreased by an average of 31.2 ms (95% CI: 0.5, 61.9; P = 0.047) when compared to regular day. Reliance on specific coping mechanisms, indicated by Coping Strategy Indicator scale scores, included problem-solving (28 ± 4), followed by seeking social support (23 ± 5) and avoidance (19 ± 4). The change score regression model (r² = 0.48) found that greater reliance on avoidance was associated with greater increase in reaction time after night call.

CONCLUSION

Reaction time increased considerably in anesthesiologists after a night call duty. Greater subjective reliance on avoidance as a coping strategy was associated with greater deterioration in performance.

Interindividual differences in the dynamics of the homeostatic process are trait-like and distinct for sleep versus wakefulness

The sleep homeostatic Process S reflects the build-up of sleep pressure during waking and its dissipation during sleep. Process S is modelled as a saturating exponential function during waking and a decreasing exponential function during sleep. Slow wave activity is a physiological marker for non-rapid eye movement (non-REM) sleep intensity and serves as an index of Process S. There is considerable interindividual variability in the sleep homeostatic responses to sleep and sleep deprivation. The aim of this study was to investigate whether interindividual differences in Process S are trait-like. Polysomnographic recordings of 8 nights (12-h sleep opportunities, 22:00-10:00 hours) interspersed with three 36-h periods of sustained wakefulness were performed in 11 healthy young adults. Empirical mean slow wave activity per non-REM sleep episode at episode mid-points were used for parameter estimation. Parameters of Process S were estimated using different combinations of consecutive sleep recordings, resulting in two to three sets of parameters per subject. Intraclass correlation coefficients were calculated to assess whether the parameters were stable across the study protocol and they showed trait-like variability among individuals. We found that the group-average time constants of the build-up and dissipation of Process S were 19.2 and 2.7 h, respectively. Intraclass correlation coefficients ranged from 0.48 to 0.56, which reflects moderate trait variability. The time constants of the build-up and dissipation varied independently among subjects, indicating two distinct traits. We conclude that interindividual differences in the parameters of the dynamics of the sleep homeostatic Process S are trait-like.