Cognitive impairment in fatigue and sleepiness associated conditions

Sleep problems and duration in school-aged children at different levels of giftedness

OBJECTIVES

Optimal sleep is crucial for developing and maintaining gifted children's cognitive abilities. However, only a few studies have explored the sleep profiles of gifted children and overlooked their internal variations. This study aimed to investigate subjective and object sleep profiles in school-aged gifted children with different levels of giftedness.

METHODS

This study included 80 school-aged children (50 % male) aged 6-11 years. Giftedness was assessed using the Wechsler Intelligence Scale for Children-Fourth Edition (WISC-IV). Subjective and objective sleep were evaluated using the Children's Sleep Habits Questionnaire (CSHQ) and Actiwatch 2.

RESULTS

The sample was divided into three groups based on their full scale intelligence quotient (IQ): 16 typically developing children (IQ < 130), 38 moderately gifted children (IQ: 130-145), and 26 highly gifted children (IQ > 145). The highly gifted children had the mildest sleep problems, particularly in sleep duration and daytime sleepiness. Moderately gifted children had the shortest subjective average sleep duration, while the three groups had no significant differences in Actiwatch-measured sleep variables. Furthermore, CSHQ total and daytime sleepiness subscale scores were negatively associated with the full scale IQ in gifted children after controlling for confounders including emotional and behavioral problems.

CONCLUSIONS

Children with higher levels of giftedness experience fewer subjective sleep problems but have similar objective sleep parameters. It is imperative to implement tailored sleep strategies for fostering intellectual development and nurturing young talents.

Minimal effect of long-term clonazepam on cognitive function in patients with isolated rapid eye movement sleep behavior disorder

STUDY OBJECTIVES

Despite its widespread use in patients with isolated rapid eye movement sleep behavior disorder (iRBD), the cognitive effect of clonazepam is uncertain. This study aimed to investigate the effect of cumulative clonazepam on cognitive function in patients with iRBD.

METHODS

Demographic characteristics, baseline cognitive test, and most recent cognitive test information were collected retrospectively. Based on cumulative clonazepam doses, patients were classified into 4 subgroups: group 1, < 365 mg (1 mg × 1 year); group 2, 365 mg to < 1,095 mg (1 mg × 3 years); group 3, 1,095 mg to < 2,190 mg (1 mg × 6 years); and group 4, 2,190 mg or more. Cognitive test scores were calculated as z scores adjusted for age, education, and sex.

RESULTS

This study included 101 patients with iRBD (63 males). Groups 1, 2, 3, and 4 had 14, 20, 32, and 35 patients, respectively. In within-group comparisons, follow-up Digit Span Backward test and the Trail Making Test A scores decreased in group 3, and follow-up Trail Making Test A and the Trail Making Test B scores decreased significantly in group 4. In the multiple regression analysis to determine influential factors on cognitive decline, cumulative clonazepam dose did not show a significant correlation with any cognitive domain. Follow-up cognitive function showed significant correlation only with baseline cognitive function.

CONCLUSIONS

Memory and executive functions tended to decline in patients with iRBD. However, there was no significant effect of cumulative clonazepam. There was no evidence that long-term use of clonazepam was related to cognitive decline in patients with iRBD.

CITATION

Lee M, Kim TK, Hong JK, Yoon I-Y. Minimal effect of long-term clonazepam on cognitive function in patients with isolated rapid eye movement sleep behavior disorder. J Clin Sleep Med. 2024;20(7):1173-1182.

Resting-state EEG and MEG biomarkers of pathological fatigue - A transdiagnostic systematic review

Fatigue is a highly prevalent and disabling symptom of many disorders and syndromes, resulting from different pathomechanisms. However, whether and how different mechanisms converge and result in similar symptomatology is only partially understood, and transdiagnostic biomarkers that could further the diagnosis and treatment of fatigue are lacking. We, therefore, performed a transdiagnostic systematic review (PROSPERO: CRD42022330113) of quantitative resting-state electroencephalography (EEG) and magnetoencephalography (MEG) studies in adult patients suffering from pathological fatigue in different disorders. Studies investigating fatigue in healthy participants were excluded. The risk of bias was assessed using a modified Newcastle-Ottawa Scale. Semi-quantitative data synthesis was conducted using modified albatross plots. After searching MEDLINE, Web of Science Core Collection, and EMBASE, 26 studies were included. Cross-sectional studies revealed increased brain activity at theta frequencies and decreased activity at alpha frequencies as potential diagnostic biomarkers. However, the risk of bias was high in many studies and domains. Together, this transdiagnostic systematic review synthesizes evidence on how resting-state M/EEG might serve as a diagnostic biomarker of pathological fatigue. Beyond, this review might help to guide future M/EEG studies on the development of fatigue biomarkers.

Sleep disorders affect cognitive function in adults: an overview of systematic reviews and meta-analyses

Sleep disorders frequently result in poor memory, attention deficits, as well as a worse prognosis for neurodegenerative changes, such as Alzheimer's disease. The purpose of this study is to investigate the impact of sleep disorders on cognition. We screened four databases for all meta-analyses and systematic reviews from the establishment through March 2022. We have carried out quality evaluation and review the eligible systematic reviews. Evidence grading and quality assessment were performed on 22 eligible articles. Sleep deprivation primarily affects simple attention, complex attention, and working memory in cognition and alertness. The moderate-to-high-quality evidence proves optimal sleep time as 7-8 h. Sleep time outside this range increases the risk of impaired executive function, non-verbal memory, and working memory. Sleep-related breathing disorders is more likely to cause mild cognitive impairment and affects several cognitive domains. In older adults, insomnia primarily affects working memory, episodic memory, inhibitory control, cognitive flexibility, problem-solving, operational ability, perceptual function, alertness, and complex attention, and maintaining sensitivity. Sleep disturbances significantly impair cognitive function, and early detection and intervention may be critical steps in reducing poor prognosis. A simple neuropsychological memory test could be used to screen people with sleep disorders for cognitive impairment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s41105-022-00439-9.

[Diagnosis and treatment of early forms of cognitive impairment: possibilities of influencing neuronal energy metabolism. Resolution of the Council of Experts]

Diagnosis and treatment of early forms of cognitive impairment: possibilities of influencing neuronal energy metabolism. Resolution of the Council of Experts.

Assessment of Perioperative Outcomes Among Surgeons Who Operated the Night Before

IMPORTANCE

The association between physician fatigue and patient outcomes is important to understand but has been difficult to examine given methodological and data limitations. Surgeons frequently perform urgent procedures overnight and perform additional procedures the following day, which could adversely affect outcomes for those daytime operations.

OBJECTIVE

To examine the association between an attending surgeon operating overnight and outcomes for operations performed by that surgeon the next day.

DESIGN, SETTING, AND PARTICIPANTS

In this cross-sectional study, a retrospective analysis of a large multicenter registry of surgical procedures was done using a within-surgeon analysis to address confounding, with data from 20 high-volume US institutions. This study included 498 234 patients who underwent a surgical procedure during the day (between 7 am and 5 pm) between January 1, 2010, and August 30, 2020.

EXPOSURES

Whether the attending surgeon for the current day's procedures operated between 11 pm and 7 am the previous night. Two exposure measures were examined: whether the surgeon operated at all the previous night and the number of hours spent operating the previous night (including having performed no work at all).

MAIN OUTCOMES AND MEASURES

The primary composite outcome was in-hospital death or major complication (sepsis, pneumonia, myocardial infarction, thromboembolic event, or stroke). Secondary outcomes included operation length and individual outcomes of death, major complications, and minor complications (surgical site infection or urinary tract infection).

RESULTS

Among 498 234 daytime operations performed by 1131 surgeons, 13 098 (2.6%) involved an attending surgeon who operated the night before. The mean (SD) age of the patients who underwent an operation was 55.3 (16.4) years, and 264 740 (53.1%) were female. After adjusting for operation type, surgeon fixed effects, and observable patient characteristics (ie, age and comorbidities), the adjusted incidence of in-hospital death or major complications was 5.89% (95% CI, 5.41%-6.36%) among daytime operations when the attending surgeon operated the night before compared with 5.87% (95% CI, 5.85%-5.89%) among daytime operations when the same surgeon did not (absolute adjusted difference, 0.02%; 95% CI, -0.47% to 0.51%; P = .93). No significant associations were found between overnight work and secondary outcomes except for operation length. Operating the previous night was associated with a statistically significant decrease in length of daytime operations (adjusted length, 112.7 vs 117.4 minutes; adjusted difference, -4.7 minutes; 95% CI, -8.7 to -0.8, P = .02), although this difference is unlikely to be meaningful.

CONCLUSIONS AND RELEVANCE

The findings of this cross-sectional study suggest that operating overnight was not associated with worse outcomes for operations performed by surgeons the subsequent day. These results provide reassurance concerning the practice of having attending surgeons take overnight call and still perform operations the following morning.

Functional Connectivity Analysis and Detection of Mental Fatigue Induced by Different Tasks Using Functional Near-Infrared Spectroscopy

Objectives

The objective of this study was to investigate common functional near-infrared spectroscopy (fNIRS) features of mental fatigue induced by different tasks. In addition to distinguishing fatigue from non-fatigue state, the early signs of fatigue were also studied so as to give an early warning of fatigue.

Methods

fNIRS data from 36 participants were used to investigate the common character of functional connectivity network corresponding to mental fatigue, which was induced by psychomotor vigilance test (PVT), cognitive work, or simulated driving. To analyze the network reorganizations quantitatively, clustering coefficient, characteristic path length, and small worldness were calculated in five sub-bands (0.6–2.0, 0.145–0.600, 0.052–0.145, 0.021–0.052, and 0.005–0.021 Hz). Moreover, we applied a random forest method to classify three fatigue states.

Results

In a moderate fatigue state: the functional connectivity strength between brain regions increased overall in 0.021–0.052 Hz, and an asymmetrical pattern of connectivity (right hemisphere > left hemisphere) was presented. In 0.052–0.145 Hz, the connectivity strength decreased overall, the clustering coefficient decreased, and the characteristic path length increased significantly. In severe fatigue state: in 0.021–0.052 Hz, the brain network began to deviate from a small-world pattern. The classification accuracy of fatigue and non-fatigue was 85.4%. The classification accuracy of moderate fatigue and severe fatigue was 82.8%.

Conclusion

The preliminary research demonstrates the feasibility of detecting mental fatigue induced by different tasks, by applying the functional network features of cerebral hemoglobin signal. This universal and robust method has the potential to detect early signs of mental fatigue and prevent relative human error in various working environments.

Systematic review and meta-analysis of cognitive impairment in myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS)

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is commonly associated with cognitive complaints. To bring out the neuropsychological symptomatology inherent to ME/CFS, we conducted a systematic review according to PRISMA and MOOSE guidelines of the literature through the analysis of 764 studies published between 1988 and 2019 by using PubMed Central website and Clarivate analytics platform. We performed a meta-analysis to delineate an idea of the neuropsychological profile inherent in ME/CFS. The clinical picture typically affects visuo-spatial immediate memory (g = - 0.55, p = 0.007), reading speed (g = - 0.82, p = 0.0001) and graphics gesture (g = - 0.59, p = 0.0001). Analysis also revealed difficulties in several processes inherent in episodic verbal memory (storage, retrieval, recognition) and visual memory (recovery) and a low efficiency in attentional abilities. Executive functions seemed to be little or not affected and instrumental functions appeared constantly preserved. With regard to the complexity and heterogeneity of the cognitive phenotype, it turns out that determining a sound clinical picture of ME/CFS cognitive profile must go through a neuropsychological examination allowing a complete evaluation integrating the notion of agreement between the choice and the number of tests and the complexity intrinsic to the pathology.

Spotlight on non-motor symptoms and Covid-19

The Coronavirus Disease 2019 (Covid-19) pandemic has profoundly affected the quality of life (QoL) and health of the general population globally over the past 2 years, with a clear impact on people with Parkinson's Disease (PwP, PD). Non-motor symptoms have been widely acknowledged to hold a vital part in the clinical spectrum of PD, and, although often underrecognized, they significantly contribute to patients' and their caregivers' QoL. Up to now, there have been numerous reports of newly emerging or acutely deteriorating non-motor symptoms in PwP who had been infected by the Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), while some of these symptoms, like fatigue, pain, depression, anxiety and cognitive impairment, have also been identified as part of the long-COVID syndrome due to their persistent nature. The subjacent mechanisms, mediating the appearance or progression of non-motor symptoms in the context of Covid-19, although probably multifactorial in origin, remain largely unknown. Such mechanisms might be, at least partly, related solely to the viral infection per se or the lifestyle changes imposed during the pandemic, as many of the non-motor symptoms seem to be prevalent even among Covid-19 patients without PD. Here, we summarize the available evidence and implications of Covid-19 in non-motor PD symptoms in the acute and chronic, if applicable, phase of the infection, with a special reference on studies of PwP.

Objective Measures of Cognitive Performance in Sleep Disorder Research

Neurocognitive tests offer objective and reliable assessment of patients' status and progress. However, there is no consensus on how to use neurocognitive assessment in sleep disorder research. An effective use of neurocognitive assessment must be based on standardized practices and have a firm theoretic basis. The aim of this review is to offer an overview of how different tests have been used in the field, mapping each test onto a corresponding cognitive domain and propose how to move forward with a suggested cognitive battery of tests covering all major cognitive domains.

Systematic Review of Sleep Characteristics in Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

(1) Background—Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a multifaceted illness characterized by profound and persistent fatigue unrelieved by rest along with a range of other debilitating symptoms. Experiences of unrefreshing and disturbed sleep are frequently described by ME/CFS patients. This is the first systematic review assessing sleep characteristics in ME/CFS. The aim of this review is to determine whether there are clinical characteristics of sleep in ME/CFS patients compared to healthy controls using objective measures such as polysomnography and multiple sleep latency testing. (2) Methods—the following databases—Pubmed, Embase, Medline (EBSCO host) and Web of Science, were systematically searched for journal articles published between January 1994 to 19 February 2021. Articles that referred to polysomnography or multiple sleep latency testing and ME/CFS patients were selected, and further refined through use of specific inclusion and exclusion criteria. Quality and bias were measured using the Joanna Briggs Institute checklist. (3) Results—twenty observational studies were included in this review. The studies investigated objective measures of sleep quality in ME/CFS. Subjective measures including perceived sleep quality and other quality of life factors were also described. (4) Conclusions—Many of the parameters measured including slow- wave sleep, apnea- hypopnea index, spectral activity and multiple sleep latency testing were inconsistent across the studies. The available research on sleep quality in ME/CFS was also limited by recruitment decisions, confounding factors, small sample sizes and non-replicated findings. Future well-designed studies are required to understand sleep quality in ME/CFS patients.

A systematic review of neurological impairments in myalgic encephalomyelitis/ chronic fatigue syndrome using neuroimaging techniques

BACKGROUND

Myalgic encephalomyelitis/ Chronic Fatigue Syndrome (ME/CFS) is a multi-system illness characterised by a diverse range of debilitating symptoms including autonomic and cognitive dysfunction. The pathomechanism remains elusive, however, neurological and cognitive aberrations are consistently described. This systematic review is the first to collect and appraise the literature related to the structural and functional neurological changes in ME/CFS patients as measured by neuroimaging techniques and to investigate how these changes may influence onset, symptom presentation and severity of the illness.

METHODS

A systematic search of databases Pubmed, Embase, MEDLINE (via EBSCOhost) and Web of Science (via Clarivate Analytics) was performed for articles dating between December 1994 and August 2019. Included publications report on neurological differences in ME/CFS patients compared with healthy controls identified using neuroimaging techniques such as magnetic resonance imaging, positron emission tomography and electroencephalography. Article selection was further refined based on specific inclusion and exclusion criteria. A quality assessment of included publications was completed using the Joanna Briggs Institute checklist.

RESULTS

A total of 55 studies were included in this review. All papers assessed neurological or cognitive differences in adult ME/CFS patients compared with healthy controls using neuroimaging techniques. The outcomes from the articles include changes in gray and white matter volumes, cerebral blood flow, brain structure, sleep, EEG activity, functional connectivity and cognitive function. Secondary measures including symptom severity were also reported in most studies.

CONCLUSIONS

The results suggest widespread disruption of the autonomic nervous system network including morphological changes, white matter abnormalities and aberrations in functional connectivity. However, these findings are not consistent across studies and the origins of these anomalies remain unknown. Future studies are required confirm the potential neurological contribution to the pathology of ME/CFS.

The Effect of Fatigue on Working Memory and Auditory Perceptual Abilities in Trained Musicians

Purpose Many perceptual processing processes, such as cognition, vision, sensation, and audition, are affected due to fatigue. Musicians are prone to fatigue because of long working hours and demanding profession. The research on assessing working memory abilities in musicians is heterogeneous, as none of the studies has controlled the effect of fatigue. This study was thus designed to assess the effect of fatigue on working memory and auditory perception in trained instrumental musicians. Method Twenty-six trained instrumental musicians and 25 nonmusicians participated in this study. The effect of fatigue was assessed by administering the working memory and auditory perception tests in prefatigue and postfatigue conditions. The fatigue was assessed using a 100-point visual analog scale. The working memory was assessed using Operation Span, Reading Span, and Digit Span (Forward and Backward) tests (Knutson et al., 1991). Auditory perception was assessed using speech-perception-in-noise and temporal integration tests. Results Working memory and speech perception were affected due to fatigue. Musicians, despite having better working memory abilities than nonmusicians, are equally prone to fatigue-related distress. Conclusion The advantage of music training for the working memory abilities may be reduced due to fatigue; hence, measures to reduce fatigue should be employed by the musicians. Fatigue should also be treated as a variable in all future research related to assess cognitive processing in musicians.

Early temporal characteristics of elderly patient cognitive impairment in electronic health records

Background

The aging population has led to an increase in cognitive impairment (CI) resulting in significant costs to patients, their families, and society. A research endeavor on a large cohort to better understand the frequency and severity of CI is urgent to respond to the health needs of this population. However, little is known about temporal trends of patient health functions (i.e., activity of daily living [ADL]) and how these trends are associated with the onset of CI in elderly patients. Also, the use of a rich source of clinical free text in electronic health records (EHRs) to facilitate CI research has not been well explored. The aim of this study is to characterize and better understand early signals of elderly patient CI by examining temporal trends of patient ADL and analyzing topics of patient medical conditions in clinical free text using topic models.

Methods

The study cohort consists of physician-diagnosed CI patients (n = 1,435) and cognitively unimpaired (CU) patients (n = 1,435) matched by age and sex, selected from patients 65 years of age or older at the time of enrollment in the Mayo Clinic Biobank. A corpus analysis was performed to examine the basic statistics of event types and practice settings where the physician first diagnosed CI. We analyzed the distribution of ADL in three different age groups over time before the development of CI. Furthermore, we applied three different topic modeling approaches on clinical free text to examine how patients’ medical conditions change over time when they were close to CI diagnosis.

Results

The trajectories of ADL deterioration became steeper in CI patients than CU patients approximately 1 to 1.5 year(s) before the actual physician diagnosis of CI. The topic modeling showed that the topic terms were mostly correlated and captured the underlying semantics relevant to CI when approaching to CI diagnosis.

Conclusions

There exist notable differences in temporal trends of basic and instrumental ADL between CI and CU patients. The trajectories of certain individual ADL, such as bathing and responsibility of own medication, were closely associated with CI development. The topic terms obtained by topic modeling methods from clinical free text have a potential to show how CI patients’ conditions evolve and reveal overlooked conditions when they close to CI diagnosis.

Prechemotherapy Levels of Plasma Dehydroepiandrosterone and Its Sulfated Form as Predictors of Cancer-Related Cognitive Impairment in Patients with Breast Cancer Receiving Chemotherapy

Study Objective

Dehydroepiandrosterone (DHEA) and its sulfated form (DHEAS)—jointly referred to as DHEA(S)—are neurosteroids known to regulate brain development and function that have been found to be positively correlated with cognitive function. It is unknown whether prechemotherapy plasma DHEA(S) levels are associated with the onset of cancer‐related cognitive impairment (CRCI). The objective of this study was to evaluate whether an association exists between prechemotherapy plasma DHEA(S) levels and onset of CRCI in patients with breast cancer receiving chemotherapy.

Design

Multicenter, prospective cohort study.

Setting

Two specialized cancer centers in Singapore.

Patients

Eighty‐one patients with early‐stage breast cancer (stages I–III) who had no prior exposure to chemotherapy and/or radiotherapy and were scheduled to receive anthracycline‐based or taxane‐based chemotherapy treatment with curative intent.

Measurements and Main Results

Patients completed assessments for self‐perceived and objective cognitive function at three time points: prechemotherapy (T1), during chemotherapy (T2), and after chemotherapy (T3). Plasma samples were collected prior to chemotherapy, and DHEA(S) levels were quantified by using ultra–high‐performance liquid chromatography–tandem mass spectrometry. Multivariable logistic regression was used to adjust for clinically important factors and to evaluate the association between prechemotherapy plasma DHEA(S) levels and CRCI. Mean ± SD age was 48.9 ± 9.3 years, with 27.8% of patients experiencing clinically significant cognitive impairment based on global Functional Assessment of Cancer Therapy–Cognitive Function scores. The mean ± SD prechemotherapy plasma DHEAS and DHEA levels were 1.61 ± 0.91 μmol/L and 19.21 ± 13.13 nmol/L, respectively. Prechemotherapy DHEAS levels were found to be associated with impairment in the self‐perceived cognitive domains of verbal fluency (adjusted odds ratio [OR] 0.27, 95% confidence interval [CI] 0.08–0.96) and mental acuity (adjusted OR 0.25, 95% CI 0.08–0.74). Conversely, DHEA levels were not associated with impairment in any cognitive subdomains.

Conclusion

Our findings suggest that patients with higher prechemotherapy DHEAS levels had lower odds of developing self‐perceived cognitive impairment. Future studies are required to further investigate the effect of DHEA(S) on specific cognitive domains and to validate our findings in independent cohorts.

Impact of sleep deprivation on anaesthesia residents' non-technical skills: a pilot simulation-based prospective randomized trial

Background

Sleep deprivation is common in anaesthesia residents, but its impact on performance remains uncertain. Non-technical skills (team working, situation awareness, decision making, and task management) are key components of quality of care in anaesthesia, particularly in crisis situations occurring in the operating room. The impact of sleep deprivation on non-technical skills is unknown. We tested the hypothesis that in anaesthesia residents sleep deprivation is associated with impaired non-technical skills.

Methods

Twenty anaesthesia residents were randomly allocated to undergo a simulation session after a night shift [sleep-deprived (SLD) group, n =10] or after a night of rest [rested (R) group, n =10] from January to March 2015. The simulated scenario was a situation of crisis management in the operating room. The primary end point was a composite score of anaesthetists' non-technical skills (ANTS) assessed by two blinded evaluators.

Results

Non-technical skills were significantly impaired in the SLD group [ANTS score 12.2 (interquartile range 10.5-13)] compared with the R group [14.5 (14-15), P <0.02]. This difference was mainly accounted for by a difference in the team working item. On the day of simulation, the SLD group showed increased sleepiness and decreased confidence in anaesthesia skills.

Conclusions

In this randomized pilot trial, sleep deprivation was associated with impaired non-technical skills of anaesthesia residents in a simulated anaesthesia intraoperative crisis scenario.

Trial registration

NCT02622217.

A unifying theory for cognitive abnormalities in functional neurological disorders, fibromyalgia and chronic fatigue syndrome: systematic review

BACKGROUND

Functional cognitive disorder (FCD) describes cognitive dysfunction in the absence of an organic cause. It is increasingly prevalent in healthcare settings yet its key neuropsychological features have not been reported in large patient cohorts. We hypothesised that cognitive profiles in fibromyalgia (FM), chronic fatigue syndrome (CFS) and functional neurological disorders (FNDs) would provide a template for characterising FCD.

METHODS

We conducted a systematic review of studies with cognition-related outcomes in FM, CFS and FND.

RESULTS

We selected 52 studies on FM, 95 on CFS and 39 on FND. We found a general discordance between high rates of subjective cognitive symptoms, including forgetfulness, distractibility and word-finding difficulties, and inconsistent objective neuropsychological deficits. Objective deficits were reported, including poor selective and divided attention, slow information processing and vulnerability to distraction. In some studies, cognitive performance was inversely correlated with pain, exertion and fatigue. Performance validity testing demonstrated poor effort in only a minority of subjects, and patients with CFS showed a heightened perception of effort.

DISCUSSION

The cognitive profiles of FM, CFS and non-cognitive FND are similar to the proposed features of FCD, suggesting common mechanistic underpinnings. Similar findings have been reported in patients with mild traumatic brain injury and whiplash. We hypothesise that pain, fatigue and excessive interoceptive monitoring produce a decrease in externally directed attention. This increases susceptibility to distraction and slows information processing, interfering with cognitive function, in particular multitasking. Routine cognitive processes are experienced as unduly effortful. This may reflect a switch from an automatic to a less efficient controlled or explicit cognitive mode, a mechanism that has also been proposed for impaired motor control in FND. These experiences might then be overinterpreted due to memory perfectionism and heightened self-monitoring of cognitive performance.

Features of Resting-State Electroencephalogram Theta Coherence in Somatic Symptom Disorder Compared With Major Depressive Disorder: A Pilot Study

OBJECTIVE

Somatic symptom disorder (SSD) often co-occurs with major depressive disorder (MDD). Both conditions share common psychobiological and biobehavioral characteristics, but little is known about differential patterns in brain function. In this study, we compared resting-state functional brain connectivity between SSD and MDD using quantitative electroencephalography.

METHODS

Fifteen patients with SSD (SSD group), 15 patients with MDD (MDD group), and 15 healthy volunteers (healthy control [HC] group) participated in this study. Participants were assessed with quantitative electroencephalography using a 21-channel electroencephalogram system. Electroencephalogram coherence in the theta frequency range (3.5-7.5 Hz) was assessed between the following seven electrode pairs: Fp1 and Fp2, F7 and T3, F8 and T4, T5 and P3, P4 and T6, P3 and Pz, and Pz and P4. Differences in coherence between groups were analyzed using analysis of variance.

RESULTS

Theta coherence between the F7 and T3 electrodes was lower in the SSD group than the MDD and HC groups (F(2,42) = 6.67, p = .0030). Theta coherence between the T5 and P3 electrodes was lower in the SSD and MDD groups than the HC group (F(2,42) = 5.65, p = .0067). Theta coherence between the Pz and P4 electrodes was lower in the SSD group than the MDD group (F(2,42) = 6.41, p = .0037).

CONCLUSIONS

Both SSD and MDD patients commonly showed decreased functional connectivity within the left temporoparietal junction, which has neurophysiological implications for cognitive-attentional processing and social interaction. Frontostriatal circuit dysfunction affects processes that control perception and emotion, as well as misperception of somatosensory data in the parietal somatosensory area, and is more likely to be a neuropathology of SSD than MDD.

Convergent Results from Neuropsychology and from Neuroimaging in Patients with Mild Cognitive Impairment

BACKGROUND/AIMS

To investigate the correspondence between neuropsychological single measures and variation in fludeoxyglucose positron emission tomography (FDG PET) glucose metabolism and magnetic resonance imaging (MRI) cortical thickness in mild cognitive impairment (MCI) patients.

METHODS

Forty-two elderly controls and 73 MCI subjects underwent FDG PET and MRI scanning. Backward regression analyses with PET and MRI regions were used as dependent variables, while Rey Auditory Verbal Memory Test (RAVLT) recall, Trail Making Test B (TMT B), and a composite test score (RAVLT learning and immediate recall, TMT A, COWAT, and letter-number sequencing) were used as predictor variables.

RESULTS

The composite score predicted variation in cortical metabolism; supplementary analyses showed that TMT B was significantly correlated with PET metabolism as well. RAVLT and TMT B were significant predictors of variation in MRI cortical thickness.

CONCLUSION

Our results indicate that RAVLT and TMT B are sensitive to variation in Alzheimer disease neuroimaging markers.

Short-term memory impairment in vestibular patients can arise independently of psychiatric impairment, fatigue, and sleeplessness

Vestibular dysfunction is associated with visual short-term memory impairment; however, it remains unclear if this impairment arises as a direct result of the vestibular dysfunction or is a consequence of comorbid changes in mood, affect, fatigue, and/or sleep. To this end, we assessed the concurrence and interdependence of these comorbidities in 101 individuals recruited from a tertiary balance clinic with a neuro-otological diagnosis. Over fifty per cent of the sample showed reduced visuospatial short-term memory, 60% and 37% exceeded cut-off on the Beck Anxiety and Depression Inventories, respectively, 70% exceeded cut-off on the Fatigue Severity Scale, 44% reported daytime sleepiness on the Epworth Sleepiness Scale, and 78% scored above cut-off on the Pittsburgh Sleep Quality Index. The high concurrence of these symptoms gives reason to infer the existence of a vestibular cognitive affective syndrome. Structural equation modelling indicated that the significant statistical association between general unassisted posture (a marker of chronic vestibular dysfunction and strong predictor of falls risk) and short-term memory was not mediated by mood and wakefulness. Instead, the memory impairment related more directly to vestibular dysfunction. From a rehabilitation perspective, the implication is that if the vestibular disorder is treated successfully then the memory problem will likewise improve.

Daytime sleepiness and related factors in nursing students

BACKGROUND

Evaluation of the frequency and causes of daytime sleepiness in nursing students because it is an important factor in improving the health status of the students, controlling sleep problems, improving students' academic achievements, and maintaining a healthy lifestyle.

AIM

The aim of this study was to determine the prevalence of daytime sleepiness in nursing students and the factors associated with it.

DESIGN

A cross-sectional research design was used in this study.

PARTICIPANTS

Nursing students (n=382).

METHOD

Data were collected using a questionnaire prepared by the authors to assess socio-demographic characteristics, sleep habits, and problems of nursing students and the Epworth Sleepiness Scale (ESS), which assesses daytime sleepiness. Descriptive statistics included numbers, percentages, mean, median, and standard deviation. Mann-Whitney U test (Z) and Kruskal-Wallis (KW) analysis of variance were used for evaluating the relationship between ESS scores and independent variables.

RESULTS

The prevalence of daytime sleepiness in the students was found to be 10.5%. Those in the 2nd grade, who were married, who did not consume coffee or tea, lived alone, regarded their own academic achievement as poor, and used the Internet during morning hours experienced increased daytime sleepiness. Moreover, students who talk in their sleep, grind their teeth, feel restless before sleep, experience problems in falling asleep, and wake up at night were found to experience increased daytime sleepiness.

CONCLUSIONS

Daytime sleepiness is a considerably common health problem in nursing students. This study found that daytime sleepiness is associated with individual characteristics, lifestyle and consumption habits, and sleep habits.

The Minneapolis-Manchester Quality of Life Instrument: reliability and validity of the Adult Form in cancer survivors

PURPOSE

Childhood cancer survivors are at risk for deficits in health-related quality of life (HRQL) as they age. Youth (8-12 years) and adolescent (13-20 years) versions of the Minneapolis-Manchester Quality of Life Instrument (MMQL) have been developed to address survivor-specific issues and are currently in use; the MMQL-Adult Form has now been developed to assess HRQL in childhood cancer survivors aged 21-55 years.

METHODS

The MMQL-Adult Form was administered to 499 adults: 65 cancer patients on-therapy, 107 off-therapy, and 327 healthy controls. Forty-four percent of patients were under 30 years old at cancer diagnosis. Principal components analysis was performed. We evaluated internal consistency reliability, stability (re-administration of the MMQL-Adult Form 2 weeks later), construct validity (concurrent administration of the SF-36), and known-groups validity (score comparisons across the three groups).

RESULTS

Principal components analysis resulted in retention of 44 items across six scales: social functioning, physical functioning, cognitive functioning, outlook on life, body image, and psychological functioning. Internal consistency (Cronbach's α) was 0.80-0.90 for individual scales and 0.95 overall. Strong intraclass correlations (0.98 overall) indicated high stability. The MMQL-Adult Form distinguished between known groups; healthy controls scored better than patients on four of six scales. The MMQL-Adult Form scales correlated highly with similar SF-36 scales, demonstrating construct validity.

CONCLUSIONS

The MMQL-Adult Form is a reliable and valid self-report instrument for measuring multidimensional HRQL in cancer survivors. Development of this instrument ensures availability of a tool enabling cross-sectional and longitudinal assessment of HRQL in childhood cancer survivors as they age.

Tired of blunt tools? Sharpening the clinical assessment of fatigue and sleepiness

Fatigue and sleepiness are ubiquitous symptoms in various conditions and are frequently associated to impaired sleep quality. While separate fatigue and sleepiness scales exist, both constructs are often confused. Unraveling this issue requires estimating the instruments' measurement properties, potential scale recalibration and re-evaluation of symptom intensities on a comparable basis. This study aims at improving the assessment of these symptoms and quantifying their degree of overlap using common-person-equating (CPE). One hundred fifty-nine patients, either with complaints of fatigue, sleepiness and/or non-restorative sleep, addressed to an academic sleep unit for a full-night polysomnography (PSG), enrolled in the study. Symptom levels were measured with the Fatigue Severity (FSS) and Epworth Sleepiness (ESS) scales. Sleep quality was assessed by the Pittsburgh Sleep Quality Index, defining 'good' and 'poor' sleeper groups. Good and poor sleepers did not differ statistically regarding demographics and PSG parameters. Rasch analysis revealed that, considering proper calibration, the ESS and FSS generate reliable and valid, unidimensional linear measures and to be invariant to perceived sleep quality. CPE showed predominantly fatigued, rather than sleepy patients, being more likely to present as poor sleepers. A concordance diagram based on scale scores is provided, in order to improve the differentiation of both symptoms.

Electroencephalogram characteristics in patients with chronic fatigue syndrome

OBJECTIVE

To explore the electroencephalogram (EEG) characteristics in patients with chronic fatigue syndrome (CFS) using brain electrical activity mapping (BEAM) and EEG nonlinear dynamical analysis.

METHODS

Forty-seven outpatients were selected over a 3-month period and divided into an observation group (24 outpatients) and a control group (23 outpatients) by using the non-probability sampling method. All the patients were given a routine EEG. The BEAM and the correlation dimension changes were analyzed to characterize the EEG features.

RESULTS

1) BEAM results indicated that the energy values of δ, θ, and α1 waves significantly increased in the observation group, compared with the control group (P<0.05, P<0.01, respectively), which suggests that the brain electrical activities in CFS patients were significantly reduced and stayed in an inhibitory state; 2) the increase of δ, θ, and α1 energy values in the right frontal and left occipital regions was more significant than other encephalic regions in CFS patients, indicating the region-specific encephalic distribution; 3) the correlation dimension in the observation group was significantly lower than the control group, suggesting decreased EEG complexity in CFS patients.

CONCLUSION

The spontaneous brain electrical activities in CFS patients were significantly reduced. The abnormal changes in the cerebral functions were localized at the right frontal and left occipital regions in CFS patients.

Effects of a selective educational system on fatigue, sleep problems, daytime sleepiness, and depression among senior high school adolescents in Taiwan

OBJECTIVE

The aim of the study reported here was to clarify the effects of academic pressure on fatigue, sleep problems, daytime sleepiness, and depression among senior high school adolescents in Taiwan.

METHODS

This cross-sectional study enrolled 757 senior high school adolescents who were classified into four groups: Grade 1 (n=261), Grade 2 (n=228), Grade 3T (n=199; Grade 3 students who had another college entrance test to take), and Grade 3S (n=69; Grade 3 students who had succeeded in their college application). Fatigue, sleep quality, daytime sleepiness, and depression were assessed using the Chinese version of the Multidimensional Fatigue Symptom Inventory - Short Form, Pittsburgh Sleep Quality Index-Taiwan Form, the Chinese version of the Epworth Sleepiness Scale, and the Chinese version of the Beck Depression Inventory(®)-II (BDI-II), respectively.

RESULTS

Physical, emotional, and mental fatigue scores were all higher in higher-grade groups. The Grade 3T (test) students had the worst fatigue severity, and the Grade 3S (success) students had the least fatigue severity. More than half of the students (60.9%) went to bed after 12 am, and they had on average 6.0 hours of sleep per night. More than 30% of the students in Grade 2 (37.3%) and Grades 3T/S (30.2%/30.4%) possibly had daily sleepiness problems. The students in Grade 3T had the worst BDI-II score (13.27±9.24), and the Grade 3S students had a much lower BDI-II score (7.91±6.13).

CONCLUSION

Relatively high proportions of fatigue, sleep problems, daytime sleepiness, and depression among senior high school adolescents were found in our study. The severities of fatigue, sleep problems, and depression were significantly diminished in the group under less academic stress (Grade 3S). Our findings may increase the understanding of the mental health of senior high school students under academic pressure in Taiwan. Further large sample size and population-based study should be done for better understanding about this topic.

Myalgic Encephalomyelitis: Symptoms and Biomarkers

Myalgic Encephalomyelitis (ME) continues to cause significant morbidity worldwide with an estimated one million cases in the United States. Hurdles to establishing consensus to achieve accurate evaluation of patients with ME continue, fueled by poor agreement about case definitions, slow progress in development of standardized diagnostic approaches, and issues surrounding research priorities. Because there are other medical problems, such as early MS and Parkinson's Disease, which have some similar clinical presentations, it is critical to accurately diagnose ME to make a differential diagnosis. In this article, we explore and summarize advances in the physiological and neurological approaches to understanding, diagnosing, and treating ME. We identify key areas and approaches to elucidate the core and secondary symptom clusters in ME so as to provide some practical suggestions in evaluation of ME for clinicians and researchers. This review, therefore, represents a synthesis of key discussions in the literature, and has important implications for a better understanding of ME, its biological markers, and diagnostic criteria. There is a clear need for more longitudinal studies in this area with larger data sets, which correct for multiple testing.

Dimensions of pure chronic fatigue: psychophysical, cognitive and biological correlates in the chronic fatigue syndrome

OBJECTIVES

To investigate associated dimensions of fatigue regarding cognitive impairment, psychomotor performances, muscular effort power and circulating cytokine levels and their relations to symptom intensity in a sample of pure chronic fatigue syndrome (CFS) patients without overlapping objective sleepiness or sleep disorders.

METHODS

16 CFS patients were compared to 14 matched controls. We assessed structured symptom-scales, polysomnography, multiple sleep latency tests, attention (Zazzo-Cancellation ZCT, digit-symbol-substitution DSST), psychomotor vigilance and speed (PVT, finger tapping test, FTT), dynamometer handgrip force (tonic and phasic trials) and circulating cytokines (IFN-γ, IL-1b, IL-6, IL-8, IL-10, TNF-α).

RESULTS

In addition to fatigue, CFS patients presented with higher affective symptom intensity and worse perceived sleep quality. Polysomnography showed more slow-wave sleep and microarousals in CFS but similar sleep time, efficiency and light-sleep durations than controls. Patients presented with impaired attention (DSST, ZCT), slower reaction times (PVT) but not with lower hit rates (FTT). Notwithstanding lower grip strength during tonic and phasic trials, CFS also presented with higher fatigability during phasic trials. Cytokine levels were increased for IL-1b, IL-8, IL-10 and TNF-α and fatigue intensity was correlated to grip strength and IL-8.

CONCLUSIONS

In contrast to sleepiness, chronic fatigue is a more complex phenomenon that cannot be reduced to one single measured dimension (i.e., sleep propensity). Showing its relations to different measurements, our study reflects this multidimensionality, in a psychosomatic disorder such as CFS. To obtain objective information, routine assessments of fatigue should rule out sleepiness, combine aspects of mental and physical fatigue and focus on fatigability.

Non-REM sleep EEG power distribution in fatigue and sleepiness

OBJECTIVES

The aim of this study is to contribute to the sleep-related differentiation between daytime fatigue and sleepiness.

METHODS

135 subjects presenting with sleep apnea-hypopnea syndrome (SAHS, n=58) or chronic fatigue syndrome (CFS, n=52) with respective sleepiness or fatigue complaints and a control group (n=25) underwent polysomnography and psychometric assessments for fatigue, sleepiness, affective symptoms and perceived sleep quality. Sleep EEG spectral analysis for ultra slow, delta, theta, alpha, sigma and beta power bands was performed on frontal, central and occipital derivations.

RESULTS

Patient groups presented with impaired subjective sleep quality and higher affective symptom intensity. CFS patients presented with highest fatigue and SAHS patients with highest sleepiness levels. All groups showed similar total sleep time. Subject groups mainly differed in sleep efficiency, wake after sleep onset, duration of light sleep (N1, N2) and slow wave sleep, as well as in sleep fragmentation and respiratory disturbance. Relative non-REM sleep power spectra distributions suggest a pattern of power exchange in higher frequency bands at the expense of central ultra slow power in CFS patients during all non-REM stages. In SAHS patients, however, we found an opposite pattern at occipital sites during N1 and N2.

CONCLUSIONS

Slow wave activity presents as a crossroad of fatigue and sleepiness with, however, different spectral power band distributions during non-REM sleep. The homeostatic function of sleep might be compromised in CFS patients and could explain why, in contrast to sleepiness, fatigue does not resolve with sleep in these patients. The present findings thus contribute to the differentiation of both phenomena.

Information processing speed in obstructive sleep apnea syndrome: a review

To provide a comprehensive review of studies on information processing speed in patients with obstructive sleep apnea syndrome (OSAS) as compared to healthy controls and normative data, and to determine whether continuous positive airway pressure (CPAP) treatment improves information processing speed. A systematic review was performed on studies drawn from Medline and PsycINFO (January 1990-December 2011) and identified from lists of references in these studies. After inclusion criteria, 159 articles were left for abstract review, and after exclusion criteria 44 articles were fully reviewed. The number of patients in the studies reviewed ranged from 10 to 157 and the study samples consisted mainly of men. Half of the studies reported that patients with OSAS showed reduced information processing speed when compared to healthy controls. Reduced information processing speed was seen more often (75%) when compared to norm-referenced data. Psychomotor speed seemed to be particularly liable to change. CPAP treatment improved processing speed, but the improvement was marginal when compared to placebo or conservative treatment. Patients with OSAS are affected by reduced information processing speed, which may persist despite CPAP treatment. Information processing is usually assessed as part of other cognitive functioning, not as a cognitive domain per se. However, it is important to take account of information processing speed when assessing other aspects of cognitive functioning. This will make it possible to determine whether cognitive decline in patients with OSAS is based on lower-level or higher-level cognitive processes or both.

Executive dysfunction in OSA before and after treatment: a meta-analysis

STUDY OBJECTIVES

Obstructive sleep apnea (OSA) is a frequent and often underdiagnosed condition that is associated with upper airway collapse, oxygen desaturation, and sleep fragmentation leading to cognitive dysfunction. There is meta-analytic evidence that subdomains of attention and memory are affected by OSA. However, a thorough investigation of the impact of OSA on different subdomains of executive function is yet to be conducted. This report investigates the impact of OSA and its treatment, in adult patients, on 5 theorized subdomains of executive function.

DESIGN

An extensive literature search was conducted of published and unpublished materials, returning 35 studies that matched selection criteria. Meta-analysis was used to synthesize the results from studies examining the impact of OSA on executive functioning compared to controls (21 studies), and before and after treatment (19 studies); 5 studies met inclusion in both categories.

MEASUREMENTS

Research papers were selected which assessed 5 subdomains of executive function: Shifting, Updating, Inhibition, Generativity, and Fluid Reasoning.

RESULTS

All 5 domains of executive function demonstrated medium to very large impairments in OSA independent of age and disease severity. Furthermore, all subdomains of executive function demonstrated small to medium improvements with CPAP treatment.

DISCUSSION

Executive function is impaired across all five domains in OSA; these difficulties improved with CPAP treatment. Age and disease severity did not moderate the effects found; however, further studies are needed to explore the extent of primary and secondary effects, and the impact of age and premorbid intellectual ability (cognitive reserve).

Regular breakfast consumption is associated with increased IQ in kindergarten children

BACKGROUND

Studies have documented a positive relationship between regular breakfast consumption and cognitive outcomes in youth. However, most of these studies have emphasized specific measures of cognition rather than cognitive performance as a broad construct (e.g., IQ test scores) and have been limited to Western samples of school-age children and adolescents. This study aims to extend the literature on breakfast consumption and cognition by examining these constructs in a sample of Chinese kindergarten-age children.

METHODS

This cross-sectional study consisted of a sample of 1269 children (697 boys and 572 girls) aged 6 years from the Chinese city of Jintan. Cognition was assessed with the Chinese version of the Wechsler preschool and primary scale of intelligence-revised. Breakfast habits were assessed through parental questionnaire. Analyses of variance and linear regression models were used to analyze the association between breakfast habits and IQ. Socioeconomic and parental psychosocial variables related to intelligence were controlled for.

RESULTS

Findings showed that children who regularly have breakfast on a near-daily basis had significantly higher full scale, verbal, and performance IQ test scores (all p<0.001) compared to children who "sometimes" have breakfast. This relationship persisted for VIQ (verbal IQ) and FIQ (full IQ) even after adjusting for gender, current living location, parental education, parental occupation, and primary child caregiver.

CONCLUSION

Findings may reflect nutritional as well as social benefits of regular breakfast consumption on cognition, and regular breakfast consumption should be encouraged among young children.

Memory and obstructive sleep apnea: a meta-analysis

STUDY OBJECTIVES

To examine episodic memory performance in individuals with obstructive sleep apnea (OSA).

DESIGN

Meta-analysis was used to synthesize results from individual studies examining the impact of OSA on episodic memory performance. The performance of individuals with OSA was compared to healthy controls or normative data.

PARTICIPANTS

Forty-two studies were included, comprising 2,294 adults with untreated OSA and 1,364 healthy controls. Studies that recorded information about participants at baseline prior to treatment interventions were included in the analysis.

MEASUREMENTS

PARTICIPANTS WERE ASSESSED WITH TASKS THAT INCLUDED A MEASURE OF EPISODIC MEMORY: immediate recall, delayed recall, learning, and/or recognition memory.

RESULTS

The results of the meta-analyses provide evidence that individuals with OSA are significantly impaired when compared to healthy controls on verbal episodic memory (immediate recall, delayed recall, learning, and recognition) and visuo-spatial episodic memory (immediate and delayed recall), but not visual immediate recall or visuo-spatial learning. When patients were compared to norms, negative effects of OSA were found only in verbal immediate and delayed recall.

CONCLUSIONS

This meta-analysis contributes to understanding of the nature of episodic memory deficits in individuals with OSA. Impairments to episodic memory are likely to affect the daily functioning of individuals with OSA.

Sleep problems, fatigue, and cognitive performance in Chinese kindergarten children

OBJECTIVE

To examine sleep problems and fatigue and their associations with cognitive performance in Chinese kindergarten children.

STUDY DESIGN

A cross-sectional analysis of baseline data from Jintan Child Cohort Study was conducted, which includes a cohort of 1656 kindergarten children in Jintan City, Jiangsu Province, China. The sample used in the current study consisted of 1385 children (44.8% girls, mean age 5.72 [SD = 0.42] years) for whom data on sleep problems or cognitive performance were available. Child Behavior Checklist was used to measure child sleep problems and fatigue, and Wechsler Preschool and Primary Scale of Intelligence-Revised was used to assess child IQ.

RESULTS

Sleep problems were prevalent, ranging from 8.9% for difficulty maintaining sleep to 70.5% for unwilling to sleep alone. Other reported sleep problems were difficulty initiating sleep (39.4%), nightmares (31.6%), sleep talking (28%), sleeping less (24.7%), and sleep resistance (23.4%). Fatigue was also prevalent, with 29.6% of children reported to be overtired and 12.6% lack of energy. Children with difficulty maintaining sleep, sleep talking, sleep resistance, or nightmares scored 2-3 points lower in full IQ than children without sleep problems. Children reported to have fatigue scored 3-6 points lower in full IQ than those children without fatigue.

CONCLUSIONS

Sleep problems and fatigue are prevalent in Chinese kindergarten children. Furthermore, sleep problems and fatigue are associated with poor cognitive performance.

Trait-like vulnerability to total and partial sleep loss

OBJECTIVE

To determine the extent to which individual differences in vulnerability to total sleep deprivation also reflect individual differences in vulnerability to multiple nights of sleep restriction.

DESIGN

Two sleep loss conditions (order counterbalanced) separated by 2 to 4 weeks: (a) total sleep deprivation (TSD) of 2 nights (63 h continuous wakefulness); (b) sleep restriction (SR) of 7 nights of 3 h nightly time in bed (TIB). Both conditions were preceded by 7 in-laboratory nights with 10 h nightly TIB; and followed by 3 recovery nights with 8 h nightly TIB. Measures of cognitive performance (psychomotor vigilance, working memory [1-Back], and mathematical processing), objective alertness, subjective sleepiness, and mood were obtained at regular intervals under both conditions. Intra-class correlation coefficients (ICC) were computed using outcome metrics averaged over the last day (08:00-20:00) of TSD and SR.

SETTING

Residential sleep/performance testing facility.

PARTICIPANTS

Nineteen healthy adults (ages 18-39; 11 males, 8 females).

INTERVENTIONS

2 nights of TSD and 7 nights SR (3 h nightly TIB).

RESULTS

volunteers who displayed greater vulnerability to TSD displayed greater vulnerability to SR on cognitive performance tasks (ICC: PVT lapses = 0.89; PVT speed = 0.86; 1-Back = 0.88; mathematical processing = 0.68, Ps < 0.05). In addition, trait-like responsivity to TSD/SR was found for mood variables vigor (ICC = 0.91), fatigue (ICC = 0.73), and happiness (ICC = 0.85) (all Ps < 0.05).

CONCLUSION

Resilience to sleep loss is a trait-like characteristic that reflects an individual's ability to maintain performance during both types of sleep loss (SR and TSD). Whether the findings extend to sleep schedules other than those investigated here (63 h of TSD and 7 nights of 3 h nightly TIB) will be the focus of future studies.

Selective modulations of attentional asymmetries after sleep deprivation

Pseudoneglect is a slight but consistent misplacement of attention toward the left visual field, commonly observed in young healthy subjects. This leftward attentional bias is thought to result from a right hemispheric dominance in visuospatial processing. Changes in endogenous levels of alertness may modulate attentional asymmetries and pseudoneglect in particular. In line with this hypothesis, it has been shown that sleep deprived shift-workers present a reversal of their attentional bias in a landmark (LDM) task (Manly, T., Dobler, V. B., Dodds, C. M., & George, M. A. (2005). Rightward shift in spatial awareness with declining alertness. Neuropsychologia, 43(12), 1721-1728). However, circadian disturbances and fatigue effects at the end of a shift work may have contributed to this reversal effect. In a first experiment, we show that sleep deprivation (SD) under controlled conditions does not markedly change the leftward bias, observable both at 21:00 and at 07:00 after SD. In a second experiment, we tested the hypothesis that a drastic reduction or inversion in the attentional bias would be present only when both the circadian drive for sleep propensity is maximal (i.e. around 05:00) and homeostatic sleep pressure is high. Thus participants were tested at 21:00 and under SD conditions at 05:00 and 09:00. Additionally, we used the greyscales (GS) task well-known to evidence a leftward bias in luminance judgments. Although results evidenced a consistent leftward bias both in the LDM and GS, we found a suppression of the leftward bias at the circadian nadir of alertness (05:00) after SD only for the GS, but not for the LDM. Noticeably, the leftward bias in the GS vanished at 05:00 after SD but reappeared at 09:00 despite continued SD, suggesting a predominant circadian influence on attentional asymmetries in the GS. Additionally, inter-sessions correlations evidenced a reproducible, consistent bias both in the LDM and GS, with no consistent relationship between the two tasks, suggesting independence of the neural networks subtending performance in LDM and GS. Overall, our results suggest that SD per se does not impede the leftward bias both in LDM and GS, whereas circadian-related variations in vigilance may impact attentional asymmetries in luminance judgments.