Impaired Vigilance Research Articles

0194 Sleep Tracker: How Accurate Does It Need To Be?

Abstract Introduction Commercial sleep tracker devices offer the ability to measure an individual’s sleep patterns, providing a portable and low-cost option to collect sleep-wake data to enhance fatigue management and minimize alertness impairment. While multiple studies have reported that sleep parameters estimated with these devices differ from gold-standard polysomnography (PSG), the extent to which these differences are acceptable is not known. Here, we provide a method to quantitatively assess whether sleep-duration errors generated by sleep trackers hinder our ability to assess alertness impairment. Methods To obtain representative statistics of sleep-duration errors, we performed a literature review and identified 14 studies that compared estimations of sleep parameters between 18 unique commercial sleep trackers and PSG. Then, we used the well-validated Unified Model of Performance (UMP), a mathematical model that predicts alertness impairment as a function of sleep history, to quantitatively assess the effect of sleep-duration errors on alertness predictions. For this purpose, we performed 20,000 simulations in which an individual slept 8 hour per night for 30 consecutive days. Each day, we randomly sampled sleep-duration errors using the obtained representative statistics and computed daily alertness-prediction errors. We repeated these simulations for 5 and 9 hours of sleep per night. We assumed that sleep-duration errors that lead to alertness-prediction errors of ≤30 ms (i.e., the within-subject variability under well-rested conditions) are not a concern. Results Based on the 14 studies, sleep trackers yielded sleep-duration errors with a mean of 22 minutes and a standard deviation of 44 minutes. Using these statistics to sample daily errors, we found that, at the end of the 30 days of UMP simulations, these sleep-duration errors led to a mean alertness-prediction error of ~20 ms, with ~75% of the errors ≤30 ms. We also found that, for each additional minute of sleep-duration error, the prediction error increased by ~1 ms. These results were consistent when the hours of sleep per night varied from 5 to 9 hours. Conclusion On average, sleep trackers lead to alertness-prediction errors that are consistently smaller than the within-subject variability of alertness impairment, suggesting that they are an alternative approach for measuring sleep duration. Support (if any)

0178 2B-Alert App: Personalized Caffeine Recommendations for Optimal Alertness

Abstract Introduction Sleep loss causes millions of individuals around the world to carry out daily activities with impaired alertness, affecting injury risk and productivity. If properly consumed, caffeine can safely and effectively mitigate the effects of sleep loss on alertness. However, to be effective, caffeine should be consumed at the right time and in the correct amount, depending on sleep history, work schedule and, importantly, sensitivity to sleep loss. Here, we present the 2B-Alert app, a unique smartphone application with capabilities to learn an individual’s trait-like response to sleep loss and to provide personalized caffeine recommendations to optimize alertness. Methods We conducted a prospective 62-h total sleep deprivation study to validate the capabilities of 2B-Alert. Throughout the challenge, 21 participants used the app to measure their alertness via the psychomotor vigilance test (PVT). The app used the PVT data collected during the first 36 h of wakefulness to learn each participant’s sleep-loss response and provided on-the-fly personalized caffeine recommendations (from 0 to 800 mg), so that each participant would sustain alertness at a pre-specified target level (mean PVT response time of 270 ms) during a 6-h period starting at 44 h into the challenge. To assess the effectiveness of the personalized recommendations, we computed the amount of PVT data during the 6-h period that fell within the target alertness level +/-2 times the within-subject variability of alertness impairment (i.e., +/-60 ms). Results We observed a wide range of responses to sleep loss, with some participants displaying high levels of resilience and others high levels of vulnerability. Accordingly, 2B-Alert recommended no caffeine to five participants, 100-400 mg to 11 participants, and 500-800 mg to five participants. Regardless of their sleep-loss response and the consumed amount of caffeine, participants sustained the target alertness level ~80% of the time during the 6-h period. Conclusion 2B-Alert automatically learns an individual’s trait-like response to sleep loss and provides personalized caffeine recommendations in real time so that individuals achieve a desired alertness level regardless of their susceptibility to sleep loss. Support (if any)

0551 Predicting Daytime Alertness Impairment in Obstructive Sleep Apnea

Abstract Introduction Obstructive sleep apnea (OSA) reduces daytime alertness leading to social and occupational impairment. The Maintenance of Wakefulness Test (MWT), a gold-standard test for daytime alertness, is time-consuming and not routinely available in clinical practice. We examined EEG-based and clinical parameters derived from diagnostic polysomnography (PSG) as predictors of alertness impairment in adults with OSA. Methods Eighty-two participants with untreated OSA on diagnostic PSG (apnea hypopnea index, AHI ≥5/hour), enrolled in a two-center clinical trial were included. The day following PSG, each participant completed four 40-minute MWT and four 10-minute Psychomotor Vigilance Tests (PVT). The outcomes were MWT mean sleep latency (MSL) and PVT lapses (reaction time ≥500 milliseconds, square root transformed). Three multiple linear regression models were used: 1. “standard predictors” (total sleep time, TST, percent REM and slow wave sleep, AHI, time < 90% oxygen saturation, and arousal index), 2. “novel predictors” derived by spectral analysis and averaged across right and left central EEG (normalized EEG power, odds ratio product; ORP parameters, and spindle characteristics), and 3. combined standard and novel predictors. Age, sex, and body mass index (BMI) were included in each model, and backward elimination (step AIC) was used for models 2 and 3. Results Participants were middle-aged (mean ± standard deviation, SD 53.5±8.7 years), with moderate OSA (AHI 33.8±18.2) and daytime sleepiness (Epworth Sleepiness Scale 11.7±3.9), and 86% were men. The adjusted r2 for MSL were: model 1=0.09, model 2=0.16, and model 3=0.27, and PVT lapses were: model 1=0.09, model 2=0.31, and model 3=0.34. For MSL, the significant predictors in model 3 included TST (t-statistic -3.59, p=0.0007), REM% (2.51, p=0.01), ORP-9 (2.95, p=0.004), ORP NREM (-3.15, p=0.002), spindle frequency (-2.95, p=0.004), and normalized EEG power (-2.59, p=0.01). For PVT lapses, model 3 predictors included 2.25-2.5 ORP% (-2.91, p=0.005), normalized EEG power (3.22, p=0.002), spindle power (-4.30, p< 0.0001), spindle frequency (2.83, p=0.006), and sex (men vs. women, -2.56, p=0.01). Conclusion We have identified several novel PSG EEG-based predictors of impaired daytime alertness in OSA that will improve occupational evaluation and prognostication in OSA after future validation. Support (if any) National Institutes of Health, UM1-HL112856, UL1TR001422, and UL1TR002003.

0170 When to Sleep and Work to Optimize Alertness

Abstract Introduction Currently, millions of individuals work outside of the conventional 9-to-5 work shift and are often required to sleep at times that are not conducive to maximizing restorative sleep. This insufficient sleep leads to health and cognitive performance impairments that compromise workers’ safety and productivity. This can be mitigated by sleeping at the time of day that maximizes the restorative benefits of sleep and working at favorable hours, within their particular opportunity windows. Here, we present an optimization algorithm to identify sleep and work schedules that maximize alertness during work hours, while reducing impairment during non-working hours to the greatest extent possible. Methods We developed an optimization algorithm that searches through a large number of possible sleep and work schedules to identify the one that maximizes alertness during work times, while meeting user-provided constraints, such as the periods during which the user has flexible opportunities to sleep and work. To generate the possible sleep and work schedules, we used the well-validated Unified Model of Performance (UMP), including its ability to predict sleep latency and sleep duration. To assess the algorithm, we simulated four experimental studies, where we compared the effectiveness of the sleep schedules obtained by the algorithm against those of the sleep schedules used in the studies. In addition, we tested the algorithm’s ability to simultaneously optimize sleep and work schedules in one of the studies. Results Using the same amount of sleep as in the studies, the algorithm proposed sleep schedules that optimally allocated sleep, reducing alertness impairment during work hours by an average of 29%. Similarly, by simultaneously optimizing sleep and work schedules during a recovery period following a chronic sleep-restriction challenge, the algorithm’s solutions resulted in recovery to baseline alertness levels two days earlier than the conventional 9-to-5 work schedule. Conclusion Our work provides the first quantitative tool to optimize sleep and work schedules and complements other existing fatigue-management tools to provide a more comprehensive set of countermeasure strategies to mitigate alertness impairment due to limited sleep. Support (if any)

Sustained attention deficits in schizophrenia: Effect of memory load on the Identical Pairs Continuous Performance Test

BackgroundSustained attention and vigilance impairments are well documented in people with schizophrenia (PSZ). The processes implicated in this impairment remain unclear. Here we investigated whether vigilance performance varied as a function of working memory load, and also examined the role of attentional lapsing that might arise from a loss of task set resulting in mind wandering. MethodWe examined Continuous Performance Test Identical Pairs (CPT-IP) data from a cumulative sample of 247 (PSZ) and 238 healthy control (HC) participants collected over a series of studies. ResultsPSZ performed more poorly that HC across conditions with signal/noise discrimination (d′) decreasing with increasing working memory load across both groups However, there was a significant interaction of group and load suggesting that performance of PSZ was more negatively impacted by increasing load. We also found that PSZ has a significantly higher rate of attention lapsing than did HC. DiscussionOur results suggest that difficulties maintaining task set and working memory limitations are implicated in the impairments observed on the Identical Pairs CPT. Difficulties with task set maintenance appear to explain the majority of between-group variance, with a more subtle impact of increasing working memory load.

Reconfigurations in brain networks upon awakening from slow wave sleep: Interventions and implications in neural communication.

Sleep inertia is the brief period of impaired alertness and performance experienced immediately after waking. Little is known about the neural mechanisms underlying this phenomenon. A better understanding of the neural processes during sleep inertia may offer insight into the awakening process. We observed brain activity every 15 min for 1 hr following abrupt awakening from slow wave sleep during the biological night. Using 32-channel electroencephalography, a network science approach, and a within-subject design, we evaluated power, clustering coefficient, and path length across frequency bands under both a control and a polychromatic short-wavelength-enriched light intervention condition. We found that under control conditions, the awakening brain is typified by an immediate reduction in global theta, alpha, and beta power. Simultaneously, we observed a decrease in the clustering coefficient and an increase in path length within the delta band. Exposure to light immediately after awakening ameliorated changes in clustering. Our results suggest that long-range network communication within the brain is crucial to the awakening process and that the brain may prioritize these long-range connections during this transitional state. Our study highlights a novel neurophysiological signature of the awakening brain and provides a potential mechanism by which light improves performance after waking.

PREVALENCE OF DRIVING FATIGUE AND ITS ASSOCIATED FACTORS AMONG LOGISTIC TRUCK DRIVERS IN MALAYSIA

Fatigue is a very serious problem for transportation workers that contributes to various issues such as reduced alertness, slower reaction time, and deteriorating driving performance leading to road accidents. This study aimed to determine the prevalence of driving fatigue and its associated factors with individual, work-related, physiological changes in heart rate, and reduced alertness among logistics truck drivers in Malaysia. A cross-sectional study was conducted among 168 truck drivers employed in a logistics and transportation company in several locations including Klang Valley, Johor, and Penang. A self-administered questionnaire was used to obtain demographic and work-related information. The Swedish Occupational Fatigue Inventory (SOFI) and Karolinska Sleepiness Scale (KSS) were used to evaluate the fatigue and level of sleepiness of logistic truck drivers. A heart rate monitor and alertness impairment assessed psychological changes using psychomotor vigilance task (PVT). Measurements were assessed before and after work conditions for subjective sleepiness scale, changes in heart rate, and alertness reduction via PVT. The prevalence of occupational fatigue among logistic truck drivers was 42.9%. There was a strong association between occupational fatigue with age (β= -0.329, 95% CI: -0.644 to -0.013), job satisfaction (β= -0.381, 95% CI: -0.502 to -0.260) and the need for recovery after work (β= 0.172, 95% CI: 0.067 to 0.277) respectively. A significant difference was found in sleepiness levels before and after driving conditions (p<0.001, t=-12.96). However, no significant association was found between heart rate and occupational fatigue (p> 0.05). For PVT mean, the results showed that significant differences were found before and after working conditions (p=0.009, t=2.44). The combination of subjective and objective evaluation of fatigue was identified as the variables contributing to driving fatigue. Age, job satisfaction, and the need for recovery were the intrinsic variables that should be put into consideration in order to overcome the driving fatigue of logistic truck drivers.

Obstructive sleep apnea-related intermittent hypoxaemia is associated with impaired vigilance.

Obstructive sleep apnea (OSA)-related intermittent hypoxaemia is a potential risk factor for different OSA comorbidities, for example cardiovascular disease. However, conflicting results are found as to whether intermittent hypoxaemia is associated with impaired vigilance. Therefore, we aimed to investigate how desaturation characteristics differ between the non-impaired vigilance and impaired vigilance patient groups formed based on psychomotor vigilance task (PVT) performance and compared with traditional OSA severity parameters. The study population comprised 863 patients with suspected OSA who underwent a PVT test before polysomnography. The conventional OSA parameters, for example, the apnea-hypopnea index, oxygen desaturation index, and arousal index were computed. Furthermore, the median desaturation area, fall area, recovery area, and desaturation depth were computed with the pre-event baseline reference and with reference to the 100% oxygen saturation level. Patients were grouped into best- and worst-performing quartiles based on the number of lapses in PVT (Q1: PVT lapses <5 and Q4: PVT lapses >36). The association between parameters and impaired vigilance was evaluated by cumulative distribution functions (CDFs) and binomial logistic regression. Based on the CDFs, patients in Q4 had larger desaturation areas, recovery areas, and deeper desaturations when these were referenced to 100% saturation compared with Q1. The odds ratio (OR) of the median desaturation area (OR=1.56), recovery area (OR=1.71), and depth (OR=1.65) were significantly elevated in Q4 in regression models. However, conventional OSA parameters were not significantly associated with impaired vigilance (ORs: 0.79-1.09). Considering desaturation parameters with a 100% SpO2 reference in the diagnosis of OSA could provide additional information on the severity of OSA and related daytime vigilance impairment.

O068 Slow frequency wake EEG and hypoxemia during sleep predicts vigilance performance following extended wakefulness in patients with OSA

Abstract Study Objectives Obstructive sleep apnea is highly prevalent, but heterogeneous making identifying patients at risk of driving impairment challenging. Resting wake electroencephalography (qEEG) is associated with vigilance performance in healthy subjects. We examined if qEEG and clinical measures predict vigilance impairment in OSA. Methods Fifty-four patients underwent baseline PSG and 28hr extended wakefulness (EW) with 2 hourly psychomotor vigilance test (PVT) and Karolinska drowsiness test and driving simulator performance at baseline and following EW. Resting wake EEG was subjected to fast Fourier transform analysis to derive EEG power in delta, theta, alpha and beta ranges. Cluster analysis assigned participants into groups of either resistant (n=39) or vulnerable (n=15) to alertness failure based on PVT and driving performance. Backward stepwise regression models were used to determine the strongest clincal and wake EEG predictors vigilance impairment. Results Compared with resistant patients, the vulnerable group exhibited increased wake EEG delta (p&amp;lt;0.001) and theta (p=0.003) power during eyes open across all testing periods. The only significant predictors of vulnerability to alertness failure (PVT and driving) included O2Nadir from baseline PSG and baseline wake EEG theta and delta (eyes open) respectively explaining 42 and 32% of the variance in vigilance outcome in models that included Age, BMI, ESS, SOL, TST, AHI, O2 Nadir. Conclusions Slow frequency wake EEG (delta and theta) and hypoxemia are predictive of future alertness failure and driving impairments in patients with OSA. These findings are important for fitness to drive assessment in OSA but require validation in independent sample.

P116 Increased airflow limitation during nocturnal respiratory events is associated with increased psychomotor vigilance task lapses in obstructive sleep apnoea patients

Abstract Introduction Impaired daytime vigilance is common in obstructive sleep apnoea (OSA) patients. However, the apnoea-hypopnea index (AHI) has been shown to have a weak correlation with daytime vigilance. This may be because the AHI only quantifies respiratory event frequency. Thus, we aimed to test our hypothesis that increased airflow limitation during nocturnal respiratory events is associated with daytime vigilance impairment. Methods 495 OSA patients (AHI≥5) completed a psychomotor vigilance task (PVT) and in-lab polysomnographic recording. The number of lapses (response time &amp;gt;500ms) was the primary outcome. Airflow limitation was quantified from nasal airflow using a validated algorithm. Linear regression models were adjusted for age, sex, and body mass index. Results The percentage of flow-limited breaths during respiratory events was associated with the number of PVT lapses (R=0.119, p&amp;lt;0.05); AHI was not (p&amp;gt;0.05). One standard deviation (SD, 20%) increase in the percentage of flow-limited breaths during respiratory events increased the number of lapses by 2.5. This effect-size was greater than that for age (one SD increase, 12.5 years, increased the number of lapses by 1.3). These results were similar after adjusting for AHI, arousal index, and desaturation event area. Similar findings were observed using the percentage of flow-limited breaths during all sleep. Discussion Increased airflow limitation during nocturnal respiratory events was associated with decreased daytime vigilance in OSA patients. This association appeared to be independent of respiratory event frequency, arousal frequency, and hypoxaemia severity. This suggests that disproportionately large ventilatory drive versus achieved ventilation (i.e. flow-limitation) contributes to daytime vigilance impairment.

Effects of energy balance on cognitive performance, risk-taking, ambulatory vigilance and mood during simulated military sustained operations (SUSOPS)

Sustained operations (SUSOPS) require military personnel to conduct combat and training operations while experiencing physical and cognitive stress and limited sleep. These operations are often conducted in a state of negative energy balance and are associated with degraded cognitive performance and mood. Whether maintaining energy balance can mitigate these declines is unclear. This randomized crossover study assessed the effects of energy balance on cognitive performance, risk-taking propensity, ambulatory vigilance, and mood during a simulated 72-h SUSOPS. MethodsTen male Soldiers (mean ± SE; 22.4 ± 1.7 y; body weight 87.3 ± 1.1 kg) completed two, 72-h simulated SUSOPS in random order, separated by 7 days of recovery. Each SUSOPS elicited ∼4500 kcal/d total energy expenditure and restricted sleep to 4 h/night. During SUSOPS, participants consumed either an energy-balanced or restricted diet that induced a 43 ± 3% energy deficit. A cognitive test battery was administered each morning and evening to assess: vigilance, working memory, grammatical reasoning, risk-taking propensity, and mood. Real-time ambulatory vigilance was assessed each morning, evening, and night via a wrist-worn monitoring device. ResultsParticipants exhibited heightened risk-taking propensity (p = 0.047) with lower self-reported self-control (p = 0.021) and fatigue (p = 0.013) during energy deficit compared to during energy balance. Vigilance accuracy (p < 0.001) and working memory (p = 0.040) performance decreased, and vigilance lapses increased (p < 0.001) during SUSOPS, but did not differ by diet. Percentage of correct responses to ambulatory vigilance stimuli varied during SUSOPS (p = 0.019) independent of diet, with generally poorer performance during the morning and night. Total mood disturbance (p = 0.001), fatigue (p < 0.001), tension (p = 0.003), and confusion (p = 0.036) increased whereas vigor decreased (p < 0.001) during SUSOPS, independent of diet. ConclusionProlonged physical activity combined with sleep restriction is associated with impaired vigilance, memory, and mood state. Under such conditions, maintaining energy balance prevents increased risk-taking and improves self-control, but does not improve other aspects of cognitive function or mood. Given the small sample in the present study, replication in a larger cohort is warranted.

One night of 10-h sleep restores vigilance after total sleep deprivation: the role of delta and theta power during recovery sleep.

A series of studies have demonstrated that impaired vigilance performance caused by total sleep deprivation could restore to baseline when recovery sleep is longer than the habitual sleep. However, it is unclear which factors on the recovery night affected the restoration of vigilance performance impaired by sleep deprivation. 22 participant's sleep electroencephalograms were recorded with polysomnography in 8-h baseline sleep and one-night 10-h recovery sleep following 36-h sleep deprivation. Participants completed a 10-min psychomotor vigilance task and subjective ratings after baseline and recovery sleep the following day. Objective vigilance and subjective ratings were impaired by sleep deprivation and recovered to baseline after one-night 10-h recovery sleep. Compared with baseline sleep, sleep depth increased with enhanced delta and theta power density, and sleep duration was also prolonged during recovery sleep. The vigilance performance difference between recovery and baseline sleep was taken as a behavioral index of the restoration of vigilance. The restoration of vigilance was correlated with the delta and theta power density of stage N3 in the frontal and central region during the recovery sleep. These findings indicated that one-night 10-h recovery sleep could restore the impaired objective vigilance and subjective ratings caused by sleep deprivation. The recuperative effect of vigilance relies on individual differences in sleep intensity. Individuals with higher sleep intensity in recovery sleep obtained better vigilance recovery.

Desaturation event scoring criteria affect the perceived severity of nocturnal hypoxic load

Objectives/BackgroundInterest in using blood oxygen desaturations in the diagnostics of sleep apnea has risen in recent years. However, no standardized criteria for desaturation scoring exist which complicates the drawing of solid conclusions from literature. Patients/methodsWe investigated how different desaturation scoring criteria affect the severity of nocturnal hypoxic load and the prediction of impaired daytime vigilance in 845 patients. Desaturations were scored based on three features: 1) minimum oxygen saturation drop during the event (2–20%, 1% interval), 2) minimum duration of the event (2–20s, 1s interval), and 3) maximum plateau duration within the event (5–60s, 5s interval), resulting in 4332 different scoring criteria. The hypoxic load was described with oxygen desaturation index (ODI), desaturation severity (DesSev), and desaturation duration (DesDur) parameters. Association between hypoxic load and impaired vigilance was investigated with covariate-adjusted area under curve (AUC) analyses by dividing patients into normal (≤5 lapses) and impaired (≥36 lapses) vigilance groups based on psychomotor vigilance task performance. ResultsThe severity of hypoxic load varied greatly between different scoring criteria. For example, median ODI ranged between 0.4 and 12.9 events/h, DesSev 0.01–0.23 %-point, and DesDur 0.3–9.6 %-point when the minimum transient drop criterion of 3% was used and other two features were altered. Overall, the minimum transient drop criterion had the largest effect on parameter values. All models with differently determined parameters predicted impaired vigilance moderately (AUC = 0.722–0.734). ConclusionsDesaturation scoring criteria greatly affected the severity of hypoxic load. However, the difference in the prediction of impaired vigilance between different criteria was rather small.

Frequency of discharge of hospitalized patients with stroke to free-standing hospice facilities-a register study from Germany.

Due to a lack of data, it is unknown if and how frequently in-patients with severe stroke are discharged to free-standing hospice facilities in Germany. Patients aged 18 or over who had been hospitalized for ischemic stroke (IS) (International Statistical Classification of Diseases, ICD-10: I63), intracerebral bleeding (ICB) (ICD-10: I61), or subarachnoid bleeding (SAB) (ICD-10: I60) were investigated. The analysis was based on data from the Northwest-German Stroke Registry from 2017 to 2020. The aim was to determine the frequency (crude/age-standardized) of hospital discharges to hospices. In addition, factors influencing the primary outcome, hospital discharge to a free-standing hospice, were assessed using multivariate logistic regression. A total of 339,513 cases of hospitalized patients diagnosed with stroke were recorded, comprising 308,067 (90.7%) with IS, 26,957 (7.9%) with ICB, and 4,489 (1.3%) with SAB. Their mean age was 73.1±13.1 years, and 52.6% were men. During hospitalization, 26,037 patients died (7.7%), including 18,623 with IS, 6,818 with ICB, and 596 with SAB. A total of 497 patients were transferred to a hospice (IS: 414, ICB: 76, SAB: 7). The corresponding (age-standardized) frequencies were as follows [95% confidence interval (CI)]: all patients, 0.05% (0.04-0.06%); IS, 0.05% (0.04-0.06%); ICB, 0.07% (0.05-0.09%); SAB, 0.01% (0.00-0.02%). Independent influencing factors that were identified included nursing-home care prior to hospitalization [odds ratio (OR) 0.34, 95% CI: 0.25-0.44], impaired vigilance on admission (OR 1.71, 95% CI: 1.39-2.10), severe functional impairment at hospital discharge (modified Rankin scale 5 vs. 0-2: OR 34.78, 95% CI: 22.94-52.75), and determination of a palliative care treatment goal during hospitalization (OR 14.22, 95% CI: 11.32-17.87). In-patients with severe stroke are hardly ever discharged to free-standing hospice facilities in Germany. The reasons for this may be complex, including an acute course in severe stroke, inadequate perception by physicians of these patients' need for palliative care, and structural conditions in long-term care for patients outside the hospital.

Investigating the effects of sleepiness in truck drivers on their headway: An instrumental variable model with grouped random parameters and heterogeneity in their means

Sleepiness is a common human factor among truck drivers resulting from sleep loss or time of day and causing impairment in vigilance, attention, and driving performance. While driver sleepiness may be associated with increased risk on the road, sleepy drivers may drive more cautiously as a result of risk-compensating behaviour. This endogeneity has been overlooked in the previous driver behaviour studies and may provide new insight into the effects of sleepiness on driving performance. In addition, the Karolinska Sleepiness Scale (KSS) has been widely used to quantify sleepiness. However, the KSS is a subjective self-reported measure and is reliant on honest reporting and understanding of the scale. An alternative way of quantifying sleepiness is using drivers’ heart rate and correlating it with their sleepiness. While recent advances in data collection technologies have made it possible to collect heart rate data in real-time and in an unobtrusive way, their application in measuring sleepiness particularly among truck drivers has been unexplored.This study aims to address these gaps and contribute to analytic methods in road safety research by collecting truck drivers’ heart rate data in real-time, measuring sleepiness from those data, and using it in an instrumental variable modelling framework to investigate its effect on driving performance. To this end, a driving simulator experiment was conducted in Belgium and heart rate data were collected for 35 truck drivers via sensors installed on the steering wheel of the simulator. Additional demographic data were collected using a questionnaire before the experiment. An instrumental variable model consisting of a discrete binary logit and a continuous generalized linear model with grouped random parameters and heterogeneity in their means was then developed to study the effects of driver sleepiness on headway. Results indicate that age, years of holding driver licence, road type, type of truck transport, and weekly distance travelled are significantly associated with sleepiness among the participants of this study. Sleepy driving is associated with reduced headway for 30.5% of the drivers and increased headway for the other 69.5%, and night-time shift is associated with such varied effects. These findings indicate that there may be group- or context-specific risk patterns which cannot be explicitly addressed by hours of service regulations and therefore, transport operators, driver trainers and fleet managers should identify and handle such context-specific high risk patterns in order to ensure safe operations.

The experience and management of sleep inertia in Australian volunteer firefighters

ObjectiveTo determine how firefighters experience and manage sleep inertia (the state of impaired alertness and performance upon waking) during night calls. MethodsSemi-structured interviews were conducted with sixteen volunteer firefighters. Firefighters were asked about their experiences of sleep inertia and what strategies they use to manage sleep inertia when waking and responding to night calls. ResultsFirefighters perceive that the duration and risk of sleep inertia is less than what is commonly espoused in the literature. This presents a potential barrier to implementing sleep inertia countermeasures in this cohort. However, firefighters informally managed sleep inertia directly and indirectly. Several deliberate strategies to directly reduce sleep inertia (e.g., running to and from their car), and indirect strategies to manage the impact of sleep inertia (e.g., risk assessments) emerged. Moreover, it was identified that various aspects of the firefighting role have the potential to reduce sleep inertia through multifactorial physical and mental stimulation (e.g., through waking to the pager alarm and the cognitive demand of firefighting tasks). ConclusionsThe firefighting role can be inherently stimulating and has the potential to reduce the severity of sleep inertia for firefighters waking and responding to night calls. Regardless, informal strategies to manage sleep inertia could be incorporated into formal education procedures of organisations to improve the safety of firefighters. Relevance to industryInformal sleep inertia management strategies could be formalised to help educate less experienced firefighters on how to manage night-time calls and improve the safety of personnel in the firefighting industry.

Cognitive, perceptual, and motor profiles of school-aged children with developmental coordination disorder.

Developmental coordination disorder (DCD) is a heterogeneous condition. Besides motor impairments, children with DCD often exhibit poor visual perceptual skills and executive functions. This study aimed to characterize the motor, perceptual, and cognitive profiles of children with DCD at the group level and in terms of subtypes. A total of 50 children with DCD and 31 typically developing (TD) peers (7–11 years old) underwent a comprehensive neuropsychological (15 tests) and motor (three subscales of the Movement Assessment Battery for Children-2) assessment. The percentage of children with DCD showing impairments in each measurement was first described. Hierarchical agglomerative and K-means iterative partitioning clustering analyses were then performed to distinguish the subtypes present among the complete sample of children (DCD and TD) in a data-driven way. Moderate to large percentages of children with DCD showed impaired executive functions (92%) and praxis (meaningless gestures and postures, 68%), as well as attentional (52%), visual perceptual (46%), and visuomotor (36%) skills. Clustering analyses identified five subtypes, four of them mainly consisting of children with DCD and one of TD children. These subtypes were characterized by: (i) generalized impairments (8 children with DCD), (ii) impaired manual dexterity, poor balance (static/dynamic), planning, and alertness (15 DCD and 1 TD child), (iii) impaired manual dexterity, cognitive inhibition, and poor visual perception (11 children with DCD), (iv) impaired manual dexterity and cognitive inhibition (15 DCD and 5 TD children), and (v) no impairment (25 TD and 1 child with DCD). Besides subtle differences, the motor and praxis measures did not enable to discriminate between the four subtypes of children with DCD. The subtypes were, however, characterized by distinct perceptual or cognitive impairments. These results highlight the importance of assessing exhaustively the perceptual and cognitive skills of children with DCD.

"I Want to Be Safe and Not Still Half Asleep": Exploring Practical Countermeasures to Manage the Risk of Sleep Inertia for Emergency Service Personnel Using a Mixed Methods Approach.

PurposeThe aim of this exploratory cross-sectional mixed methods study was to determine 1) whether sleep inertia, the temporary state of impaired vigilance performance upon waking, is perceived to be a concern by emergency service personnel, 2) what strategies are currently used by emergency service workplaces to manage sleep inertia, 3) the barriers to implementing reactive sleep inertia countermeasures, and 4) what strategies personnel suggest to manage sleep inertia.Participants and MethodsA sample (n = 92) of employed and volunteer Australian emergency service personnel (fire and rescue, ambulance, police, state-based rescue and recovery personnel) completed an online survey. Data collected included demographic variables and work context, experiences of sleep inertia in the emergency role, barriers to sleep inertia countermeasures, and existing workplace sleep inertia countermeasures and recommendations. Quantitative data were analysed using descriptive statistics, and qualitative data were thematically analysed.ResultsApproximately 67% of participants expressed concern about sleep inertia when responding in their emergency role. Despite this, there were few strategies to manage sleep inertia in the workplace. One major barrier identified was a lack of time in being able to implement sleep inertia countermeasures. Fatigue management strategies, such as reducing on-call periods, and operational changes, such as screening calls to reduce false alarms, were suggested by participants as potential strategies to manage sleep inertia.ConclusionSleep inertia is a concern for emergency service personnel and thus more research is required to determine effective sleep inertia management strategies to reduce the risks associated with sleep inertia and improve personnel safety and those in their care. In addition, future studies could investigate strategies to integrate reactive sleep inertia countermeasures into the emergency response procedure.

The severity and morphology of intermittent hypoxemias are related to impaired daytime alertness

The severity and morphology of intermittent hypoxemias are related to impaired daytime alertness

Increased variability in total sleep time is associated with reduced psychomotor vigilance impairment following experimental sleep continuity disruption

Increased variability in total sleep time is associated with reduced psychomotor vigilance impairment following experimental sleep continuity disruption