Assessment of the unified model of performance: accuracy of group-average and individualised alertness predictions.

To be effective as a key component of fatigue-management systems, biomathematical models that predict alertness impairment as a function of time of day, sleep history, and caffeine consumption must demonstrate the ability to make accurate predictions across a range of sleep-loss and caffeine schedules. Here, we assessed the ability of the previously reported unified model of performance (UMP) to predict alertness impairment at the group-average and individualised levels in a comprehensive set of 12 studies, including 22 sleep and caffeine conditions, for a total of 301 unique subjects. Given sleep and caffeine schedules, the UMP predicted alertness impairment based on the psychomotor vigilance test (PVT) for the duration of the schedule. To quantify prediction performance, we computed the root mean square error (RMSE) between model predictions and PVT data, and the fraction of measured PVTs that fell within the models' prediction intervals (PIs). For the group-average model predictions, the overall RMSE was 43 ms (range 15-74 ms) and the fraction of PVTs within the PIs was 80% (range 41%-100%). At the individualised level, the UMP could predict alertness for 81% of the subjects, with an overall average RMSE of 64 ms (range 32-147 ms) and fraction of PVTs within the PIs conservatively estimated as 71% (range 41%-100%). Altogether, these results suggest that, for the group-average model and 81% of the individualised models, in three out of four PVT measurements we cannot distinguish between study data and model predictions.

Dietary nitrate supplementation enhances heavy load carriage performance in military cadets.

PURPOSE: To determine the effects of dietary nitrate (NO3-) supplementation on physiological responses, cognitive function, and performance during heavy load carriage in military cadets. METHODS: Ten healthy males (81.0 ± 6.5 kg; 180.0 ± 4.5 cm; 56.2 ± 3.7 ml·kg·min-1 VO2max) consumed 140 mL·d-1 of beetroot juice (BRJ; 12.8 mmol NO3-) or placebo (PL) for six d preceding an exercise trial, which consisted of 45 min of load carriage (55% body mass) at 4.83 km·h-1 and 1.5% grade, followed by a 1.6-km time-trial (TT) at 4% grade. Gas exchange, heart rate, and perceptual responses were assessed during constant-load exercise and the TT. Cognitive function was assessed immediately prior to, during, and post-exercise via the psychomotor vigilance test (PVT). RESULTS: Post-TT HR (188 ± 7.1 vs. 185 ± 7.4; d = 0.40; p = 0.03), mean tidal volume (2.15 ± 0.27 vs. 2.04 ± 0.23; p = 0.02; d = 0.47), and performance (770.9 ± 78.2 s vs. 809.8 ± 61.4 s; p = 0.03; d = 0.63) were increased during the TT with BRJ versus PL. There were no effects of BRJ on constant-load gas exchange or perceptual responses, and cognitive function was unchanged at all time points. CONCLUSION: BRJ supplementation improves heavy load carriage performance in military cadets possibly as a result of attenuated respiratory muscle fatigue, rather than enhanced exercise economy.

Temporal fluctuations in vigilance and neural networks after sleep deprivation.

Vigilance instability in the sleep-deprived state was deemed to result from the imbalance in thalamic-FPN-DMN circuits (FPN: frontoparietal network; DMN: default mode network), but the behavioural correlation of this neural hypothesis is still unclear. To address this issue, we applied dynamic functional connectivity (DFC) analysis on the task-based fMRI data and detected high arousal state (HAS) and low arousal state (LAS). Relative to HAS, LAS demonstrated higher positive connectivity within task-positive networks (TPN), attenuated TPN-DMN anti-correlation, and greater anti-correlation between cerebral and subcortico-cerebellar networks. Critically, DFC differences between HAS and LAS were correlated with the ongoing vigilance performance in the sleep-deprived state. The current findings confirmed a direct link between vigilance instability and DFC in the thalamic-FPN-DMN circuits. In particular, we postulated that the integration within task-related system and segregation between task-related system and the subcortico-cerebellar system might be the critical neural markers underlying vigilance instability in the sleep-deprived state.

Abnormal dynamic functional connectivity after sleep deprivation from temporal variability perspective.

Sleep deprivation (SD) is very common in modern society and regarded as a potential causal mechanism of several clinical disorders. Previous neuroimaging studies have explored the neural mechanisms of SD using magnetic resonance imaging (MRI) from static (comparing two MRI sessions [one after SD and one after resting wakefulness]) and dynamic (using repeated MRI during one night of SD) perspectives. Recent SD researches have focused on the dynamic functional brain organization during the resting-state scan. Our present study adopted a novel metric (temporal variability), which has been successfully applied to many clinical diseases, to examine the dynamic functional connectivity after SD in 55 normal young subjects. We found that sleep-deprived subjects showed increased regional-level temporal variability in large-scale brain regions, and decreased regional-level temporal variability in several thalamus subregions. After SD, participants exhibited enhanced intra-network temporal variability in the default mode network (DMN) and increased inter-network temporal variability in numerous subnetwork pairs. Furthermore, we found that the inter-network temporal variability between visual network and DMN was negative related with the slowest 10% respond speed (ß = -.42, p = 5.57 × 10-4 ) of the psychomotor vigilance test after SD following the stepwise regression analysis. In conclusion, our findings suggested that sleep-deprived subjects showed abnormal dynamic brain functional configuration, which provides new insights into the neural underpinnings of SD and contributes to our understanding of the pathophysiology of clinical disorders.

Predisposing factors of daytime sleepiness in obese OSA patients.

Excessive daytime sleepiness is a common symptom in obese patients with obstructive sleep apnea. We investigated predisposing factors of excessive daytime sleepiness by comparing obese non-sleepy with sleepy patients with obstructive sleep apnea. Excessive daytime sleepiness was determined by the Epworth Sleepiness Scale in 43 patients (34 men and 9 women) with obstructive sleep apnea (apnea-hypopnea index ≥ 15 events per hr) and obesity (body mass index ≥ 30 kg m-2 ). Two subgroups were formed with (Epworth Sleepiness Scale ≥ 11) and without (Epworth Sleepiness Scale < 11) excessive daytime sleepiness. The concept of excessive daytime sleepiness was compared with other established daytime performance tests (Stanford Sleepiness Scale, Multiple Sleep Latency Test, Pupillographic Sleepiness Test, Marburger Vigilance test). Associations were calculated between excessive daytime sleepiness and demographic, metabolic and polysomnographic data. We included 19 sleepy patients (mean Epworth Sleepiness Scale score 15.2) and 24 non-sleepy patients (mean Epworth Sleepiness Scale score 5.8). Epworth Sleepiness Scale was negatively correlated with age and morning cortisol. Epworth Sleepiness Scale was positively correlated with body mass index, Stanford Sleepiness Scale, Beck's Depression Inventory and Marburger Vigilance test. Sleepy obese patients were significantly younger (mean 49.1 years), showed lower morning cortisol level (mean 9.41 µg L-1 ) and a trend to higher body mass index (mean 37.5 kg m- ²) compared with non-sleepy obese patients (mean: 59.3 years, 5.7 µg L-1 , 34.6 kg m- ², respectively). Many different excessive daytime sleepiness phenotypes are probably enclosed in obese patients with obstructive sleep apnea. Epworth Sleepiness Scale scores were best reflected by the objective Marburger Vigilance test results. The objective test can be particularly useful in cohorts where subjective reports are unreliable and operational readiness is paramount. Sleepy and non-sleepy obese patients with obstructive sleep apnea were similar in all polysomnographic parameters. Sleepy patients were younger, heavier and showed lower morning cortisol levels than non-sleepy patients.

2B-Alert Web 2.0, an Open-Access Tool for Predicting Alertness and Optimizing the Benefits of Caffeine: Utility Study.

BACKGROUND: One-third of the US population experiences sleep loss, with the potential to impair physical and cognitive performance, reduce productivity, and imperil safety during work and daily activities. Computer-based fatigue-management systems with the ability to predict the effects of sleep schedules on alertness and identify safe and effective caffeine interventions that maximize its stimulating benefits could help mitigate cognitive impairment due to limited sleep. To provide these capabilities to broad communities, we previously released 2B-Alert Web, a publicly available tool for predicting the average alertness level of a group of individuals as a function of time of day, sleep history, and caffeine consumption. OBJECTIVE: In this study, we aim to enhance the capability of the 2B-Alert Web tool by providing the means for it to automatically recommend safe and effective caffeine interventions (time and dose) that lead to optimal alertness levels at user-specified times under any sleep-loss condition. METHODS: We incorporated a recently developed caffeine-optimization algorithm into the predictive models of the original 2B-Alert Web tool, allowing the system to search for and identify viable caffeine interventions that result in user-specified alertness levels at desired times of the day. To assess the potential benefits of this new capability, we simulated four sleep-deprivation conditions (sustained operations, restricted sleep with morning or evening shift, and night shift with daytime sleep) and compared the alertness levels resulting from the algorithm's recommendations with those based on the US Army caffeine-countermeasure guidelines. In addition, we enhanced the usability of the tool by adopting a drag-and-drop graphical interface for the creation of sleep and caffeine schedules. RESULTS: For the 4 simulated conditions, the 2B-Alert Web-proposed interventions increased mean alertness by 36% to 94% and decreased peak alertness impairment by 31% to 71% while using equivalent or smaller doses of caffeine as the corresponding US Army guidelines. CONCLUSIONS: The enhanced capability of this evidence-based, publicly available tool increases the efficiency by which diverse communities of users can identify safe and effective caffeine interventions to mitigate the effects of sleep loss in the design of research studies and work and rest schedules.

The impact of shift work schedules on PVT performance in naturalistic settings: a systematic review.

OBJECTIVE: The Psychomotor Vigilance Test (PVT) is considered the gold standard for detecting sleep loss and circadian misalignment related changes in performance in laboratory and field settings. This short 3-, 5- or 10-min test appraises an individual's sustained vigilant attention on a visual stimulus through reaction time, false starts and performance lapses. The PVT has been widely used as a measure to assess vigilant attention among shift workers, but information evaluating the application and performance of this test in different naturalistic shift work settings is limited. The purpose of this review is to synthesise and evaluate existing literature which has used the PVT to assess and monitor psychomotor performance in response to shift work schedules and rosters performed in real-world settings. METHODS: A systematic search of studies examining PVT performance in response to 24/7 shift work schedules (e.g., day, afternoon, evening and night shifts) performed under naturalistic conditions was conducted. Articles were identified by searching Medline, Embase, CINHAL and PsycINFO databases in April 2020. RESULTS: The search yielded 135 results, of which 16 publications were suitable to be included in this review. Articles were grouped according to when the PVT was applied to a research cohort, which included (a) multiple instances per shift, (b) commencement and cessation of shift and (c) other varying times. CONCLUSIONS: This review suggests PVT performance is typically congruent across studies when the test is applied at generally consistent time intervals. The lack of research concerning the use of the PVT during extended duty shifts (e.g., shifts and on call work > 30 h) is an area for future research.

Fatigue risk management based on self-reported fatigue: Expanding a biomathematical model of fatigue-related performance deficits to also predict subjective sleepiness.

Biomathematical models of fatigue can be used to predict neurobehavioral deficits during sleep/wake or work/rest schedules. Current models make predictions for objective performance deficits and/or subjective sleepiness, but known differences in the temporal dynamics of objective versus subjective outcomes have not been addressed. We expanded a biomathematical model of fatigue previously developed to predict objective performance deficits as measured on the Psychomotor Vigilance Test (PVT) to also predict subjective sleepiness as self-reported on the Karolinska Sleepiness Scale (KSS). Four model parameters were re-estimated to capture the distinct dynamics of the KSS and account for the scale difference between KSS and PVT. Two separate ensembles of datasets - drawn from laboratory studies of sleep deprivation, sleep restriction, simulated night work, napping, and recovery sleep - were used for calibration and subsequent validation of the model for subjective sleepiness. The expanded model was found to exhibit high prediction accuracy for subjective sleepiness, while retaining high prediction accuracy for objective performance deficits. Application of the validated model to an example scenario based on cargo aviation operations revealed divergence between predictions for objective and subjective outcomes, with subjective sleepiness substantially underestimating accumulating objective impairment, which has important real-world implications. In safety-sensitive operations such as commercial aviation, where self-ratings of sleepiness are used as part of fatigue risk management, the systematic differences in the temporal dynamics of objective versus subjective measures of functional impairment point to a potentially significant risk evaluation sensitivity gap. The expanded biomathematical model of fatigue presented here provides a useful quantitative tool to bridge this previously unrecognized gap.

Inside the clinical evaluation of sleepiness: subjective and objective tools.

PURPOSE: To critically review the available tools for evaluating excessive daytime sleepiness (EDS) in clinical practice. METHODS: Objective tests and subjective scales were divided into three groups in accordance with the different dimensions of sleepiness they measure, namely physiological, manifest, and introspective. Strengths, weaknesses, and limitations of each test have been analysed and discussed along with the available recommendations for their use in clinical practice. RESULTS: The majority of the tests developed for sleepiness evaluation do not have practical usefulness outside the research setting. The suboptimal correlation between different tests mainly depends on the different dimensions of sleepiness they analyse. Most importantly in-laboratory tests poorly correlate with sleepiness in real-life situations and, to date, none is able to predict the risk of injuries related to EDS, especially on an individual level. CONCLUSIONS: There exists not the one best test to assess EDS, however, clinicians can choose a more specific test to address a specific diagnostic challenge on the individual level. The development of novel performance tests with low cost and easy to administer is advisable for both screening purposes and fitness for duty evaluations in populations at high risk of EDS-related injuries, for example professional drivers.

Test-retest reliability of cerebral blood flow for assessing brain function at rest and during a vigilance task.

Arterial spin labeled (ASL) perfusion magnetic resonance imaging (MRI) is increasingly used to assess regional brain activity and cerebrovascular function in both healthy and clinical populations. ASL perfusion imaging provides a quantitative measure of regional brain activity by determining absolute cerebral blood flow (CBF) values at a resting state or during task performance. However, the comparative reliability of these ASL measures is not well characterized. It is also unclear whether the test-retest reliability of absolute CBF or task-induced CBF change measures would be comparable to the reliability of task performance. In this study, fifteen healthy participants were scanned three times in a strictly controlled in-laboratory study while at rest and during performing a simple and reliable psychomotor vigilance test (PVT). The reliability of absolute CBF and task-induced CBF changes was evaluated using the intraclass correlation coefficient (ICC) and compared to that of task performance. Absolute CBF showed excellent test-retest reliability across the three scans for both resting and PVT scans. The reliability of regional absolute CBF was comparable to that of behavioral measures of PVT performance, and was slightly higher during PVT scans as compared with resting scans. Task-induced regional CBF changes demonstrated only poor to moderate reliability across three scans. These findings suggest that absolute CBF measures are more reliable than task-induced CBF changes for characterizing regional brain function, especially for longitudinal and clinical studies.

2B-Alert App: A mobile application for real-time individualized prediction of alertness.

Knowing how an individual responds to sleep deprivation is a requirement for developing personalized fatigue management strategies. Here we describe and validate the 2B-Alert App, the first mobile application that progressively learns an individual's trait-like response to sleep deprivation in real time, to generate increasingly more accurate individualized predictions of alertness. We incorporated a Bayesian learning algorithm within the validated Unified Model of Performance to automatically and gradually adapt the model parameters to an individual after each psychomotor vigilance test. We implemented the resulting model and the psychomotor vigilance test as a smartphone application (2B-Alert App), and prospectively validated its performance in a 62-hr total sleep deprivation study in which 21 participants used the app to perform psychomotor vigilance tests every 3 hr and obtain real-time individualized predictions after each test. The temporal profiles of reaction times on the app-conducted psychomotor vigilance tests were well correlated with and as sensitive as those obtained with a previously characterized psychomotor vigilance test device. The app progressively learned each individual's trait-like response to sleep deprivation throughout the study, yielding increasingly more accurate predictions of alertness for the last 24 hr of total sleep deprivation as the number of psychomotor vigilance tests increased. After only 12 psychomotor vigilance tests, the accuracy of the model predictions was comparable to the peak accuracy obtained using all psychomotor vigilance tests. With the ability to make real-time individualized predictions of the effects of sleep deprivation on future alertness, the 2B-Alert App can be used to tailor personalized fatigue management strategies, facilitating self-management of alertness and safety in operational and non-operational settings.

The long-term effects of mandibular advancement splint on cardiovascular fitness and psychomotor performance in patients with mild to moderate obstructive sleep apnea: a prospective study.

BACKGROUND: Obstructive sleep apnea (OSA) manifests as a reduction or complete cessation of airflow despite an ongoing inspiratory effort, leading to hypoxemia and hypercapnia. The inability to maintain normal breathing reduces the oxygen saturation in blood leading to a cycle of various systemic implications. Hence, a prospective single arm study was planned to evaluate the long-term (2 years) effect of oral appliance on cardiovascular fitness and psychomotor performance in patients with mild to moderate obstructive sleep apnea. METHODS: Thirty dentulous OSA patients (25 males; 5 females; age 41 ± 4 years; BMI 22 ± 5; AHI 5-30) were included in the study. All the patients were assessed for systolic blood pressure (SBP), diastolic blood pressure (DBP), apnea/hypopnea index (AHI), lipid peroxidation, and psychomotor vigilance test at baseline, 6 months, 1 year, and 2 years after wearing mandibular advancement splint (MAS). RESULTS: A significant reduction in AHI, blood pressure, and lipid peroxidation was observed following MAS use. Psychomotor vigilance test showed marked improvement in response time with almost 0 count of lapses after 2 years of MAS use. CONCLUSIONS: The present study suggested that MAS can be helpful in improving cardiovascular fitness and cognitive response in patients with mild to moderate OSA.

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

Cytokines such as TNFα play an integral role in sleep/wake regulation and have recently been hypothesized to be involved in cognitive impairment due to sleep deprivation. We examined the effect of a guanine to adenine substitution at position 308 in the TNFα gene (TNFα G308A) on psychomotor vigilance performance impairment during total sleep deprivation. A total of 88 healthy women and men (ages 22-40) participated in one of five laboratory total sleep deprivation experiments. Performance on a psychomotor vigilance test (PVT) was measured every 2-3h. The TNFα 308A allele, which is less common than the 308G allele, was associated with greater resilience to psychomotor vigilance performance impairment during total sleep deprivation (regardless of time of day), and also provided a small performance benefit at baseline. The effect of genotype on resilience persisted when controlling for between-subjects differences in age, gender, race/ethnicity, and baseline sleep duration. The TNFα G308A polymorphism predicted less than 10% of the overall between-subjects variance in performance impairment during sleep deprivation. Nonetheless, the differential effect of the polymorphism at the peak of performance impairment was more than 50% of median performance impairment at that time, which is sizeable compared to the effects of other genotypes reported in the literature. Our findings provided evidence for a role of TNFα in the effects of sleep deprivation on psychomotor vigilance performance. Furthermore, the TNFα G308A polymorphism may have predictive potential in a biomarker panel for the assessment of resilience to psychomotor vigilance performance impairment due to sleep deprivation.

Functional cortical connectivity analysis of mental fatigue unmasks hemispheric asymmetry and changes in small-world networks.

Changes in functional connectivity across mental states can provide richer information about human cognition than simpler univariate approaches. Here, we applied a graph theoretical approach to analyze such changes in the lower alpha (8-10 Hz) band of EEG data from 26 subjects undergoing a mentally-demanding test of sustained attention: the Psychomotor Vigilance Test. Behavior and connectivity maps were compared between the first and last 5 min of the task. Reaction times were significantly slower in the final minutes of the task, showing a clear time-on-task effect. A significant increase was observed in weighted characteristic path length, a measure of the efficiency of information transfer within the cortical network. This increase was correlated with reaction time change. Functional connectivity patterns were also estimated on the cortical surface via source localization of cortical activities in 26 predefined regions of interest. Increased characteristic path length was revealed, providing further support for the presence of a reshaped global topology in cortical connectivity networks under fatigue state. Additional analysis showed an asymmetrical pattern of connectivity (right>left) in fronto-parietal regions associated with sustained attention, supporting the right-lateralization of this function. Interestingly, in the fatigue state, significance decreases were observed in left, but not right fronto-parietal connectivity. Our results indicate that functional network organization can change over relatively short time scales with mental fatigue, and that decreased connectivity has a meaningful relationship with individual difference in behavior and performance.

Association between habitual snoring and vigilant attention in elementary school children.

OBJECTIVES: Vigilant attention (VA) is a fundamental neurocognitive function. However, the association between habitual snoring (HS) and VA in community-based children remains unclear. Therefore, this study aimed to elucidate the association. METHODS: The study included 2014 children from grades 1-6 across six elementary schools. Snoring frequency was evaluated using a questionnaire administered to parents. VA was assessed using a brief 3-min psychomotor vigilance test (PVT-B). Generalized linear models and multivariate logistic regression analysis were utilized to examine the association between snoring frequency and PVT-B performance. Impaired PVT-B performance was defined as the worst quartile of PVT-B metrics. RESULTS: The PVT-B performance significantly improved with advancing school grade level (p trend < 0.0001). A significant negative correlation was observed between snoring frequency and PVT-B performance. Particularly, in grade 1, HS was associated with a higher risk of impaired PVT-B performance, including response speed (mean reciprocal reaction time) (adjusted odds ratio [aOR] 2.56, 95% confidence interval [CI]: 1.20-5.50), more slowest 10% RT (aOR 3.28, 95% CI: 1.51-6.88), and more lapse500 (number of lapse of reaction time ≥ 500 ms) (aOR 3.18, 95% CI: 1.45-6.80) compared to children without snoring. CONCLUSIONS: Our findings show that VA rapidly improves throughout elementary school. Additionally, younger children with HS are at risk of VA deficits, emphasizing the importance of early intervention for HS.

Multiscale entropy in a 10-minute vigilance task.

Research has shown multiscale entropy, brain signal behavior across time scales, to reliably increase at lower time scales with time-on-task fatigue. However, multiscale entropy has not been examined in short vigilance tasks (i.e., ≤ 10 min). Addressing this gap, we examine multiscale entropy during a 10-minute Psychomotor Vigilance Test (PVT). Thirty-four participants provided neural data while completing the PVT. We compared the first 2 min of the task to the 7th and 8th minutes to avoid end-spurt effects. Results suggested increased multiscale entropy at lower time scales later compared to earlier in the task, suggesting multiscale entropy is a strong marker of time-on-task fatigue onset during short vigils. Separate analyses for Fast and Slow performers reveal differential entropy patterns, particularly over visual cortices. Here, observed brain-behavior linkage between entropy and reaction time for slow performers suggests that entropy assays over sensory cortices might have predictive value for fatigue onset or shifts from on- to off-task states.

The impact of intermittent fasting during Ramadan on psychomotor and cognitive skills in adolescent athletes.

Introduction: Intermittent fasting (IF) represents a dietary intervention similar to caloric restriction, characterized by the strategic limitation of food consumption. Among the diverse array of practices for IF, Ramadan IF (RIF), a religious observance in Islam, mandates that healthy adult Muslims abstain from both food and drinks during daylight hours. In sports, researchers have extensively studied IF effects on health, including sleep and physical performance, but its impact on cognitive functions during RIF remains understudied. Therefore, this study was conducted to evaluate the influence of RIF on psychomotor and cognitive performance among young female athletes. Methods: To achieve this purpose, a cohort of 23 female handball players, aged 17.2 ± 0.5 years, participated in a series of six testing sessions: one conducted prior to Ramadan (R0), and others during the first (R1), second (R2), third (R3), and fourth (R4) weeks of Ramadan, followed by a session in the week after Ramadan (R5). Each session involved assessments using a Simple Reaction Time Test (SRT), Choice Reaction Time Test (CRT), Vigilance Test (VT), and Mental Rotation Test (MRT). Additionally, dietary intake, body composition, and Pittsburgh Sleep Quality Index (PSQI) scores were evaluated during these periods. Results and discussion: The obtained data illustrated that there was a decrease in SRT, CRT, VT, and MRT performances during R1 in comparison to R0 (all p < .001). This reduction was also observed in R2, R3, R4, and R5. Notably, during the fourth week of Ramadan (R4), these cognitive and psychomotor parameters were significantly lower than during the earlier weeks (R1, R2, R3; all p < .001). Furthermore, a gradual decrease in total PSQI scores, sleep quality, and sleep duration was observed throughout the Ramadan period, reaching the lowest levels during R4. These findings illustrate that RIF has a significantly detrimental impact on neuromuscular and cognitive abilities as well as sleep quality in young female athletes. The study also highlights a fluctuating pattern in cognitive function across the four weeks of Ramadan, with the most pronounced decline observed during the final week of fasting illustrating the importance of conducting similar studies on normal individuals from both genders with larger sample size.

Implementation of a psychomotor vigilance test to investigate the effects of driving fatigue on oil and gas truck drivers' performance.

Introduction: Driving fatigue has been shown to increase the risk of accidents and potentially fatal crashes. Fatigue is a serious risk that some drivers do not take seriously. Previous studies investigated the effects of driving fatigue in the Malaysian oil and gas transportation industry by employing survey questionnaires. However, they did not explain the behavior of fatigue. Besides, these results required validation by a more reliable method that can describe how fatigue occurs. Methods: Thus, in this study, we used the Psychomotor Vigilance Test (PVT-192) and a short survey to address driving fatigue behavior and identify the influences of driving fatigue on driving performance in real life (on the road) with actual oil and gas tanker drivers. The total participants in the experimental study were 58 drivers. Results: For the analysis, a Wilcoxon Signed Ranks Test, Z value and Spearman's rho were used to measure the significant difference between the pre and post-tests of PVT and the correlation between the fatigue variables and driving performance. Discussion: During the experiment's first and second days, this study's results indicated that driving fatigue gradually escalated. Likewise, there was a negative correlation based on the test of the relationship between the PVT data and the driving performance survey data. Additionally, the drivers suffer from accumulative fatigue, which requires more effort from the transportation company management to promote the drivers awareness of fatigue consequences.

Eyelid Closure Behavior of Patients with Idiopathic and Nonorganic Hypersomnia, Narcolepsy-Cataplexy, and Healthy Controls in the Maintenance of Wakefulness Test.

Purpose: Differential diagnosis of central disorders of hypersomnolence remains challenging, particularly between idiopathic (IH) and nonorganic hypersomnia (NOH). We hypothesized that eyelid closure behavior in the maintenance of wakefulness test (MWT) could be a valuable biomarker. Patients and Methods: MWT recordings of patients with IH, NOH, narcolepsy-cataplexy (NC), and healthy sleep-deprived controls (H) were retrospectively analyzed (15 individuals per group). For each MWT trial, visual scoring of face videography for partial (50-80%) and full eyelid closure (≥80%) was performed from "lights off" to the first microsleep episode (≥3 s). Results: In all groups, the frequency and cumulative duration of periods with partial and full eyelid closure gradually increased toward the first microsleep episode. On the group level, significant differences occurred for the latency to the first microsleep episode (IH 21 min (18-33), NOH 23 min (17-35), NC 11 min (7-19), H 10 min (6-25); p = 0.009), the ratio between partial and full eyelid closure duration (IH 2.2 (0.9-3.1), NOH 0.5 (0-1.2), NC 2.8 (1.1-5), H 0.7 (0.4-3.3); p = 0.004), and the difference between full and partial eyelid closure duration in the five minutes prior to the first microsleep episode (∆full - partial eyelid closure duration: IH -16 s (-35 to 28); NOH 46 s (9-82); NC -6 s (-26 to 5); H 10 s (-4 to 18); p = 0.007). IH and NOH significantly differed comparing the ratio between partial and full eyelid closure (p = 0.005) and the difference between ∆full - partial eyelid closure duration in the five minutes prior to the first microsleep episode (p = 0.006). Conclusion: In the MWT, eyelid closure behavior (∆full - partial) in the period prior to the first microsleep episode could be of value for discriminating NOH from other etiologies of excessive daytime sleepiness, particularly IH.

PERCLOS-based technologies for detecting drowsiness: current evidence and future directions.

Drowsiness associated with sleep loss and circadian misalignment is a risk factor for accidents and human error. The percentage of time that the eyes are more than 80% closed (PERCLOS) is one of the most validated indices used for the passive detection of drowsiness, which is increased with sleep deprivation, after partial sleep restriction, at nighttime, and by other drowsiness manipulations during vigilance tests, simulated driving, and on-road driving. However, some cases have been reported wherein PERCLOS was not affected by drowsiness manipulations, such as in moderate drowsiness conditions, in older adults, and during aviation-related tasks. Additionally, although PERCLOS is one of the most sensitive indices for detecting drowsiness-related performance impairments during the psychomotor vigilance test or behavioral maintenance of wakefulness test, no single index is currently available as an optimal marker for detecting drowsiness during driving or other real-world situations. Based on the current published evidence, this narrative review suggests that future studies should focus on: (1) standardization to minimize differences in the definition of PERCLOS between studies; (2) extensive validation using a single device that utilizes PERCLOS-based technology; (3) development and validation of technologies that integrate PERCLOS with other behavioral and/or physiological indices, because PERCLOS alone may not be sufficiently sensitive for detecting drowsiness caused by factors other than falling asleep, such as inattention or distraction; and (4) further validation studies and field trials targeting sleep disorders and trials in real-world environments. Through such studies, PERCLOS-based technology may contribute to preventing drowsiness-related accidents and human error.