Response speed measurements on the psychomotor vigilance test: how precise is precise enough?

Impact of Carbon Dioxide Exposures on Sleep Latency among Healthy Volunteers: A Randomized Order, Paired Crossover Study, Evidence from the Multiple Sleep Latency Test

BACKGROUND

Daytime sleepiness affects work efficiency, occupational safety, and public health. Although previous studies have reported an association between environmental carbon dioxide (eCO2) and daytime sleepiness, it has been challenging to draw a firm conclusion due to the lack of standardized sampling and profiling protocols.

OBJECTIVE

We examined the effect of pure CO2 exposure at 5,000 (ppm, parts per million) on daytime sleepiness.

METHODS

Eleven healthy participants (males of 24 ± 3 years, mean ± SD) completed a four-nap multiple sleep latency test (MSLT) protocol in the environmentally controlled chamber under two conditions: the CO2 condition (4,851 ± 229 ppm) and the Control condition (1,102 ± 204 ppm). The subjective sleepiness level and cognitive performances were also evaluated using the Stanford Sleepiness Scale (SSS) questionnaire, Psychomotor Vigilance Test (PVT), and Stroop test after each nap session.

RESULTS

A significant reduction in sleep latency was observed in the CO2 exposure condition (Control vs. CO2 = 13.1 ± 3.3 min vs. 9.7 ± 3.2 min). The subjective sleepiness scores were also significantly higher in the CO2 exposure condition than in the Control condition (Control vs. CO2 = 2.7 ± 0.5 vs. 4.7 ± 0.8). Cognitive responses after naps showed no significant difference across conditions.

CONCLUSION

This study revealed that exposure to environmental CO2 at a concentration as high as the upper safety limit at work sites significantly shortened the sleep latency and enhanced subjective sleepiness during naps in the MSLT without affecting cognitive responses after each exposure. Our results demonstrated that exposure to high environmental CO2 induces daytime sleepiness that potentially compromises work efficiency and safety.

Effect of oxygen supplementation on cognitive performance among HEMS providers after acute exposure to altitude: the HEMS II randomized clinical trial

IMPORTANCE

Emergency medical services (EMS) providers transiently ascend to high altitude for primary missions and secondary transports in mountainous areas in helicopters that are unpressurised and do not have facilities for oxygen supplementation. The decrease in cerebral oxygen saturation can lead to impairment in attention and reaction time as well as in quality of care during acute exposure to altitude.

OBJECTIVE

The primary aim of the current study was to investigate the effect of oxygen supplementation on cognitive performance in Helicopter EMS (HEMS) providers during acute exposure to altitude.

DESIGN, SETTING, AND PARTICIPANTS

This interventional, randomized, controlled, double-blind, cross-over clinical trial was conducted in October 2021. Each trial used a simulated altitude scenario equivalent to 4000 m, in which volunteers were exposed to hypobaric hypoxia with a constant rate of ascent of 4 m/s in an environmental chamber under controlled, replicable, and safe conditions. Trials could be voluntarily terminated at any time. Inclusion criteria were being members of emergency medical services and search and rescue services with an age between 18 and 60 years and an American Society of Anesthesiologists physical status class I.

EXPOSURES

Each participant conducted 2 trials, one in which they were exposed to altitude with oxygen supplementation (intervention trial) and the other in which they were exposed to altitude with ambient air supplementation (control trial).

MAIN OUTCOMES AND MEASURES

Measurements included peripheral oxygen saturation (SpO2), cerebral oxygenation (ScO2), breathing and heart rates, Psychomotor Vigilance Test (PVT), Digit-Symbol Substitution Test (DSST), n-Back test (2-BACK), the Grooved Pegboard test, and questionnaires on subjective performance, stress, workload, and positive and negative affect. Paired t-tests were used to compare conditions (intervention vs. control). Data were further analyzed using generalized estimating equations (GEE).

RESULTS

A total of 36 volunteers (30 men; mean [SD] age, 36 [9] years; mean [SD] education, 17 [4] years) were exposed to the intervention and control trials. The intervention trials, compared with the control trials, had higher values of SpO2 (mean [SD], 97.9 [1.6] % vs. 86 [2.3] %, t-test, p = 0.004) and ScO2 (mean [SD], 69.9 [5.8] % vs. 62.1 [5.2] %, paired t-test, p = 0.004). The intervention trials compared with the control trials had a shorter reaction time (RT) on the PVT after 5 min (mean [SD], 277.8 [16.7] ms vs. 282.5 [15.3] ms, paired t-test, p = 0.006) and after 30 min (mean [SD], 276.9 [17.7] ms vs. 280.7 [15.0] ms, paired t-test, p = 0.054) at altitude. While controlling for other variables, there was a RT increase of 0.37 ms for each % of SpO2 decrease. The intervention trials showed significantly higher values for DSST number of correct responses (with a difference of mean [SD], 1.2 [3.2], paired t-test, p = 0.035). Variables in the intervention trials were otherwise similar to those in the control trials for DSST number of incorrect responses, 2-BACK, and the Grooved Pegboard test.

CONCLUSIONS AND RELEVANCE

This randomized clinical trial found that oxygen supplementation improves cognitive performance among HEMS providers during acute exposure to 4000 m altitude. The use of oxygen supplementation may allow to maintain attention and timely reaction in HEMS providers. The impact of repeated altitude ascents on the same day, sleep-deprivation, and additional stressors should be investigated. Trial registration NCT05073406, ClinicalTrials.gov trial registration.

Medical intelligence using PPG signals and hybrid learning at the edge to detect fatigue in physical activities

The educational environment plays a vital role in the development of students who participate in athletic pursuits both in terms of their physical health and their ability to detect fatigue. As a result of recent advancements in deep learning and biosensors benefitting from edge computing resources, we are now able to monitor the physiological fatigue of students participating in sports in real time. These devices can then be used to analyze the data using contemporary technology. In this paper, we present an innovative deep learning framework for forecasting fatigue in athletic students following physical exercise. It addresses the issue of lack of precision computational models and extensive data analysis in current approaches to monitoring students' physical activity. In our study, we classified fatigue and non-fatigue based on photoplethysmography (PPG) signals. Several deep learning models are compared in the study. Using limited training data, determining the optimal parameters for PPG presents a significant challenge. For datasets containing many data points, several models were trained using PPG signals: a deep residual network convolutional neural network (ResNetCNN) ResNetCNN, an Xception architecture, a bidirectional long short-term memory (BILSTM), and a combination of these models. Training and testing datasets were assigned using a fivefold cross validation approach. Based on the testing dataset, the model demonstrated a proper classification accuracy of 91.8%.

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.

Effects of total sleep deprivation on performance in a manual spacecraft docking task

Sleep deprivation and circadian rhythm disruptions are highly prevalent in shift workers, and also among astronauts. Resulting sleepiness can reduce cognitive performance, lead to catastrophic occupational events, and jeopardize space missions. We investigated whether 24 hours of total sleep deprivation would affect performance not only in the Psychomotor Vigilance Task (PVT), but also in a complex operational task, i.e. simulated manual spacecraft docking. Sixty-two healthy participants completed the manual docking simulation 6df and the PVT once after a night of total sleep deprivation and once after eight hours of scheduled sleep in a counterbalanced order. We assessed the impact of sleep deprivation on docking as well as PVT performance and investigated if sustained attention is an essential component of operational performance after sleep loss. The results showed that docking accuracy decreased significantly after sleep deprivation in comparison to the control condition, but only at difficult task levels. PVT performance deteriorated under sleep deprivation. Participants with larger impairments in PVT response speed after sleep deprivation also showed larger impairments in docking accuracy. In conclusion, sleep deprivation led to impaired 6df performance, which was partly explained by impairments in sustained attention. Elevated motivation levels due to the novelty and attractiveness of the task may have helped participants to compensate for the effects of sleepiness at easier task levels. Continued testing of manual docking skills could be a useful tool both to detect sleep loss-related impairments and assess astronauts' readiness for duty during long-duration missions.

Safety and pharmacodynamics of a single infusion of danavorexton in adults with idiopathic hypersomnia

STUDY OBJECTIVES

Idiopathic hypersomnia (IH) is a chronic disorder characterized by excessive daytime sleepiness unexplained by another disorder or drug/medication use. Although the orexin system plays a role in sleep-wake regulation, orexin A levels in the cerebrospinal fluid are normal in people with IH. This phase 1b, randomized, placebo-controlled, crossover study aimed to investigate the safety, pharmacokinetics, and pharmacodynamics of danavorexton, a small-molecule orexin-2 receptor agonist, in adults with IH.

METHODS

Adults with IH aged 18-75 years were randomized to one of two treatment sequences of single intravenous infusions of danavorexton 112 mg and placebo. Pharmacodynamic endpoints included the maintenance of wakefulness test (MWT), the Karolinska Sleepiness Scale (KSS), and the psychomotor vigilance task (PVT). Adverse events were monitored throughout the study period.

RESULTS

Of 28 randomized participants, 12 (44.4%) had a treatment-emergent adverse event (TEAE) and 10 (37.0%) had a TEAE considered related to study drug, most of which were mild or moderate. Four participants (18.2%) had urinary TEAEs while receiving danavorexton, all of which were mild in severity. There were no deaths or TEAEs leading to discontinuation. Improvements in MWT, KSS, and PVT scores were observed with danavorexton compared to placebo. Following drug administration, a mean sleep latency of 40 min (maximum value) was observed during the MWT within 2 h of danavorexton infusion in most participants.

CONCLUSIONS

A single infusion of danavorexton improves subjective and objective excessive daytime sleepiness in people with IH with no serious TEAEs, indicating orexin-2 receptor agonists are promising treatments for IH. Clinical Trial: Clinicaltrials.gov. https://clinicaltrials.gov/ct2/show/NCT04091438.

Effects of face masks on fairness in on-site personnel selection during a pandemic

Introduction

Despite significant challenges, personnel selection procedures had to continue as on-site testing in the Covid-19 pandemic. Health and safety measures and specifically the use of face masks threaten to limit the fairness of cognitive testing and behavioral observation in the assessment center.

Methods

In this study, we compare the performance and pass rates of pilot selection under three different conditions in the selection campaigns of 2019 (pre-pandemic), 2020 (health and safety measures without mask), and 2021 (health and safety measures with mask).

Results

Mask wearing and other health and safety measures had no influence on the objective parameters of pilot selection. However, for some of the areas of competence in the assessment center subjective observability was rated lower for the condition with face masks.

Discussion

We conclude that the fairness and precision of selection processes are not compromised by wearing face masks and that a high degree of standardization in diagnostic instruments prevents a partially reduced subjective observability from affecting the selection's outcome.

[Correlation of the Karolinska sleepiness scale with performance variables of the monotonous bimanual psychomotor test]

OBJECTIVE

To assess the objectivity of measuring the level of sleepiness in the subjects using a monotonous psychomotor bimanual tapping test developed by us, performed on mobile devices running Android OS.

MATERIAL AND METHODS

Four hundred and ninety-four hour-long experiments with the performance of a psychomotor test were conducted on 102 students. Using the method of mixed linear models, correlations between the levels of sleepiness according to the Karolinska Sleepiness Scale (KSS) and the Epworth Sleepiness Scale (ESS) and the behavioral indicators of the test were evaluated.

RESULTS

Statistically significant correlations between the increase in KSS scores and such indicators as a decrease in the total number of button taps and an increase in the frequency of «microsleep» episodes are shown. Statistically significant correlations of ESS score characteristics with the behavioral indicators of the test were not found.

CONCLUSION

A large statistical material shows a reliable correlation of the parameters of the psychomotor test with the level of sleepiness on the Karolinska scale, which allows using the mobile application developed by us to determine the current level of sleepiness /alertness in the field.

The influence of blue light on sleep, performance and wellbeing in young adults: A systematic review

Introduction: Blue light from electronic devices has a bad reputation. It has a wavelength which may influence our circadian rhythm and cause bad sleep. But there are other aspects of blue light exposure which are often overlooked, for example, it may influence performance and wellbeing. However, few resources summarize its effects systematically. Therefore, the goal of this systematic review was to distil the present evidence on blue light exposure and its influence on sleep, performance and wellbeing and discuss its significance for athletes.

Methods: The databases that were searched were Cochrane, Embase, Pubmed, Scopus, and Virtual Health Library. The studies included investigated the influence of blue light exposure on either sleep, performance, wellbeing or a combination of those parameters on healthy humans. Quality assessment was done based on the quantitative assessment tool “QualSyst.”

Results: Summarizing the influence of blue light exposure, the following results were found (expressed as proportion to the number of studies investigating the particular parameter): Fifty percent of studies found tiredness to be decreased. One fifth of studies found sleep quality to be decreased and one third found sleep duration to be decreased. Half of the studies found sleep efficacy to be decreased and slightly less than half found sleep latency to be increased. More than one half of the studies found cognitive performance to be increased. Slightly more than two thirds found alertness to be increased and reaction time to be decreased. Slightly less than half of the studies found wellbeing to be increased.

Conclusion: Blue light exposure can positively affect cognitive performance, alertness, and reaction time. This might benefit sports reliant on team-work and decision-making and may help prevent injury. Blue light might also have negative effects such as the decrease in sleep quality and sleep duration, which might worsen an athlete’s physical and cognitive performance and recovery. Further research should explore if blue light can improve sleep, performance and wellbeing to significantly benefit athletic performance.

The 3-Minute Psychomotor Vigilance Test Demonstrates Inadequate Convergent Validity Relative to the 10-Minute Psychomotor Vigilance Test Across Sleep Loss and Recovery

The Psychomotor Vigilance Test (PVT) is a widely used behavioral attention measure, with the 10-min (PVT-10) and 3-min (PVT-3) as two commonly used versions. The PVT-3 may be comparable to the PVT-10, though its convergent validity relative to the PVT-10 has not been explicitly assessed. For the first time, we utilized repeated measures correlation (rmcorr) to evaluate intra-individual associations between PVT-10 and PVT-3 versions across total sleep deprivation (TSD), chronic sleep restriction (SR) and multiple consecutive days of recovery. Eighty-three healthy adults (mean ± SD, 34.7 ± 8.9 years; 36 females) received two baseline nights (B1-B2), five SR nights (SR1-SR5), 36 h TSD, and four recovery nights (R1-R4) between sleep loss conditions. The PVT-10 and PVT-3 were completed every 2 h during wakefulness. Rmcorr compared responses on two frequently used, sensitive PVT metrics: reaction time (RT) via response speed (1/RT) and lapses (RT > 500 ms on the PVT-10 and > 355 ms on the PVT-3) by day (e.g., B2), by study phase (e.g., SR1-SR5), and by time point (1000-2000 h). PVT 1/RT correlations were generally stronger than those for lapses. The majority of correlations (48/50 [96%] for PVT lapses and 38/50 [76%] for PVT 1/RT) were values below 0.70, indicating validity issues. Overall, the PVT-3 demonstrated inadequate convergent validity with the "gold standard" PVT-10 across two different types of sleep loss and across extended recovery. Thus, the PVT-3 is not interchangeable with the PVT-10 for assessing behavioral attention performance during sleep loss based on the design of our study and the metrics we evaluated. Our results have substantial implications for design and measure selection in laboratory and applied settings, including those involving sleep deprivation.

Sleep deficiency in spaceflight is associated with degraded neurobehavioral functions and elevated stress in astronauts on six-month missions aboard the International Space Station

Astronauts are required to maintain optimal neurobehavioral functioning despite chronic exposure to the stressors and challenges of spaceflight. Sleep of adequate quality and duration is fundamental to neurobehavioral functioning, however astronauts commonly experience short sleep durations in spaceflight (<6 h). As humans embark on long-duration space exploration missions, there is an outstanding need to identify the consequences of sleep deficiency in spaceflight on neurobehavioral functions. Therefore, we conducted a longitudinal study that examined the sleep-wake behaviors, neurobehavioral functions, and ratings of stress and workload of N = 24 astronauts before, during, and after 6-month missions aboard the International Space Station (ISS). The computerized, Reaction SelfTest (RST), gathered astronaut report of sleep-wake behaviors, stress, workload, and somatic behavioral states; the RST also objectively assessed vigilant attention (i.e. Psychomotor Vigilance Test-Brief). Data collection began 180 days before launch, continued every 4 days in-flight aboard the ISS, and up to 90 days post-landing, which produced N = 2,856 RSTs. Consistent with previous ISS studies, astronauts reported sleeping ~6.5 h in-flight. The adverse consequences of short sleep were observed across neurobehavioral functions, where sleep durations <6 h were associated with significant reductions in psychomotor response speed, elevated stress, and higher workload. Sleep durations <5 h were associated with elevated negative somatic behavioral states. Furthermore, longer sleep durations had beneficial effects on astronaut neurobehavioral functions. Taken together, our findings highlight the importance of sleep for the maintenance of neurobehavioral functioning and as with humans on Earth, astronauts would likely benefit from interventions that promote sleep duration and quality.

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

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