The impact of sustained wakefulness and time-of-day on OSPAT performance

An evaluation and comparison of commercial driver sleepiness detection technology: a rapid review

Objective. Sleepiness-related motor vehicle crashes, caused by lack of sleep or driving during night-time hours, often result in serious injury or fatality. Sleepiness detection technology is rapidly emerging as a sleepiness risk mitigation strategy for drivers. Continuous monitoring technologies assess and alert to driver sleepiness in real-time, while fit for duty technologies provide a single assessment of sleepiness state. The aim of this rapid review was to evaluate and compare sleepiness detection technologies in relation to specifications, cost, target consumer group and validity.Approach. We evaluated a range of sleepiness detection technologies suitable for consumer groups ranging from regular drivers in private vehicles through to work-related drivers within large businesses.Main results. Continuous monitoring technologies typically ranged between $100 and $3000 AUD and had ongoing monthly costs for telematics functionality and manager alerts. Fit for duty technologies had either a one-off purchase cost or a monthly subscription cost. Of concern, the majority of commercial continuous monitoring technologies lacked scientific validation. While some technologies had promising findings in terms of their ability to detect and reduce driver sleepiness, further validation work is required. Field studies that evaluate the sensitivity and specificity of technology alerts under conditions that are regularly experienced by drivers are necessary. Additionally, there is a need for longitudinal naturalistic driving studies to determine whether sleepiness detection technologies actually reduce sleepiness-related crashes or near-crashes.Significance. There is an abundance of sleepiness detection technologies on the market, but a majority lacked validation. There is a need for these technologies and their validation to be regulated by a driver safety body. Otherwise, consumers will base their technology choices on cost and features, rather than the ability to save lives.

Fatigue in the Indonesian rail industry: A study examining passenger train drivers

OBJECTIVE

The railway industry in Indonesia has grown substantially in the past five years, with greater network and tracks length that will double in 2030. There has been a growing concern, however, that fatigue among front-line personnel have not been addressed satisfactorily. This study aimed at evaluating the degree of fatigue among passenger train drivers and suggested practical recommendations to the Indonesian Railway Company.

METHOD

A total of 32 train drivers (driving for about 4 h during the morning or afternoon shifts) agreed to participate in the study. Subjective and objective measures of fatigue (and sleepiness) were obtained prior to, during, and immediately following the end of a duty. Fatigue and driving performance were also determined based on (off-line) analysis of continuous video recordings of the drivers performing the duty.

RESULTS

Fatigue generally increased as a function of time and, for some, 2 h of driving was sufficient in inducing substantial level of fatigue increase. Unlike the morning shift, the afternoon shift was characterized with increased undue fatigue and unacceptable level of performance decrements.

CONCLUSION

In general, fatigue was not found among train drivers working the morning shift. For these drivers, however, there were a couple of individuals with excessive levels of fatigue. The effects of fatigue were more apparent for the afternoon shift. This is possibly due to the degraded sleep quality as a result of split rest periods obtained prior to the duty. It is suggested in this study that the company pay a much closer attention to the work-sleep schedules, and to improve sleep quality by redesigning better sleeping arrangements.

Fatigue in Emergency Services Operations: Assessment of the Optimal Objective and Subjective Measures Using a Simulated Wildfire Deployment

Under controlled laboratory conditions, neurobehavioral assays such as the Psychomotor Vigilance Task (PVT) are sensitive to increasing levels of fatigue, and in general, tend to correlate with subjective ratings. However, laboratory studies specifically curtail physical activity, potentially limiting the applicability of such findings to field settings that involve physical work. In addition, laboratory studies typically involve healthy young male participants that are not always representative of a typical working population. In order to determine whether these findings extend to field-like conditions, we put 88 Australian volunteer firefighters through a multi-day firefighting simulation. Participants were required to perform real-world physical and cognitive tasks under conditions of elevated temperature and moderate sleep restriction. We aimed to examine changes in fatigue in an effort to determine the optimum objective and subjective measures. Objective and subjective tests were sensitive to fatigue outside laboratory conditions. The PVT was the most sensitive assay of objective fatigue, with the Samn-Perelli fatigue scale the most sensitive of the subjective measures. The Samn-Perilli fatigue scale correlated best with PVT performance, but explained a small amount of variance. Although the Samn-Perelli scale can be easily administered in the field, the wide range of individual variance limits its efficacy as a once-off assessment tool. Rather, fatigue measures should be applied as a component of a broader fatigue risk management system. Findings provide firefighting agencies, and other occupations involving physical work, guidance as to the most sensitive and specific measures for assessing fatigue in their personnel.

Detecting impairment: sensitive cognitive measures of dose-related acute alcohol intoxication

The cognitive impairment that results from acute alcohol intoxication is associated with considerable safety risks. Other psychoactive substances, such as medications, pose a similar risk to road and workplace safety. However, there is currently no legal limit for operating vehicles or working while experiencing drug-related impairment. The current study sought to identify a brief cognitive task sensitive to a meaningful degree of impairment from acute alcohol intoxication to potentially stand as a reference from which to quantify impairment from other similar substances. A placebo-controlled single-blind crossover design was employed to determine the relative sensitivity of four commonly-administered cognitive tasks (Compensatory Tracking Task, Digit Symbol Substitution Test, Brief Stop Signal Task and Inspection Time Task) to alcohol-related impairment in male social drinkers at ~0.05% ascending breath alcohol concentration (BrAC), ~0.08% peak BrAC and 0.05% descending BrAC. The Inspection Time Task was identified as the most sensitive task, detecting a medium to large magnitude increase in impairment (g ≈ 0.60) at 0.05% ascending and descending BrAC, and a large magnitude effect size (g = 0.80) at 0.08% peak BrAC. The remaining tasks failed to demonstrate sensitivity to dose-dependent and limb-dependent changes in alcohol-induced impairment. The Inspection Time Task was deemed the most sensitive task for screening alcohol-related impairment based on the present results. Confirmation of equivalence with other drug-related impairment and sensitivity to alcohol-induced impairment in real-world settings should be established in future research.

Visually guided tracking on a handheld device: can it be used to measure visuomotor skill in shift workers?

OBJECTIVE

We introduced a new visually controlled tracking task that can be assessed on a handheld device in shift workers to evaluate time-of-day dependent modulations in visuomotor performance.

BACKGROUND

Tracking tasks have been used to predict performance fluctuations depending on time of day mainly under laboratory conditions. One challenge to an extended use at the actual working site is the complex and fixed test setup consisting of a test unit, a monitor, and a manipulation object, such as a joystick.

METHOD

Participants followed an unpredictably moving target on the screen of a handheld device with an attachable stylus. A total of 11 shift workers (age range: 20-59, mean: 33.64, standard deviation: 10.56) were tested in the morning, the evening, and the night shift in 2-hr intervals with the tracking task and indicated their fatigue levels on visual analogue scales. We evaluated tracking precision by calculating the mean spatial deviation from the target for each session.

RESULTS

Tracking precision was significantly influenced by the interaction between shift and session, suggesting a clear time-of-day effect of visuomotor performance under real-life conditions. Tracking performance declined during early-morning hours whereas fatigue ratings increased.

CONCLUSION

These findings suggest that our setup is suitable to detect time-of-day dependent performance changes in visually guided tracking.

APPLICATION

Our task could be used to evaluate fluctuations in visuomotor coordination, a skill that is decisive in various production steps at the actual working place to assess productivity.

Inhibition of return, but not facilitation, disappears under vigilance decrease due to sleep deprivation

In this study, we assessed whether unspecific attention processes signaled by general reaction times (RTs), as well as specific facilitatory (validity or facilitation effect) and inhibitory (inhibition of return, IOR) effects involved in the attentional orienting network, are affected by low vigilance due to both circadian factors and sleep deprivation (SD). Eighteen male participants performed a cuing task in which peripheral cues were nonpredictive about the target location and the cue-target interval varied at three levels: 200 ms, 800 ms, and 1,100 ms. Facilitation with the shortest and IOR with the longest cue-target intervals were observed in the baseline session, thus replicating previous related studies. Under SD condition, RTs were generally slower, indicating a reduction in the participants' arousal level. The inclusion of a phasic alerting tone in several trials partially compensated for the reduction in tonic alertness, but not with the longest cue-target interval. With regard to orienting, whereas the facilitation effect due to reflexive shifts of attention was preserved with sleep loss, the IOR was not observed. These results suggest that the decrease of vigilance produced by SD affects both the compensatory effects of phasic alerting and the endogenous component involved in disengaging attention from the cued location, a requisite for the IOR effect being observed.

The effects of shift work and time of day on fine motor control during handwriting

Handwriting is an elaborate and highly automatised skill relying on fine motor control. In laboratory conditions handwriting kinematics are modulated by the time of day. This study investigated handwriting kinematics in a rotational shift system and assessed whether similar time of day fluctuations at the work place can be observed. Handwriting performance was measured in two tasks of different levels of complexity in 34 shift workers across morning (6:00-14:00), evening (14:00-22:00) and night shifts (22:00-6:00). Participants were tested during all three shifts in 2-h intervals with mobile testing devices. We calculated average velocity, script size and writing frequency to quantify handwriting kinematics and fluency. Average velocity and script size were significantly affected by the shift work schedule with the worst performance during morning shifts and the best performance during evening shifts. Our data are of high economic relevance as fine motor skills are indispensable for accurate and effective production at the work place.

PRACTITIONER SUMMARY

Handwriting is one of the most complex fine motor skills in humans, which is frequently performed in daily life. In this study, we tested handwriting repeatedly at the work place in a rotational shift system. We found slower handwriting velocity and reduced script size during morning shifts.

Circadian rhythm in force tracking and in dual task costs

The present study determined a circadian rhythm in force control during a visually guided tracking task under single task conditions (i.e., tracking task presented alone) and dual task conditions (i.e., tracking task together with a memory task). Nine healthy young male subjects participated in a Constant Routine protocol involving a week of regular bedtimes, a baseline night of 8 h sleep, and subsequent wakefulness of 40 h. Subjects performed an eye-hand coordination task that required tracking an unpredictable target (presented on a computer screen) by using grip force to adjust a visual feedback to the changing target. Tracking performance (both in precision and delay) were time-of-day-specific with worst performance at around 04:00 h. The dual task costs, as an index of interference of two tasks performed simultaneously, only showed a significant effect of the memory task on tracking precision during the circadian minimum. In contrast, dual task costs were close to zero during midday and absent in tracking delay. Tracking precision descriptively revealed inter-individual differences: half of the subjects maintained fairly stable performance during the 40 h of wakefulness, whereas the other half showed a clear circadian rhythmicity in tracking precision. Thus, tracking precision seems to be a sensitive parameter for conditions of divided attention and inter-individual variability during the circadian minimum, whereas tracking delay revealed neither a dichotomy of task conditions nor inter-individual differences in performance-amplitude over sessions. Nonetheless, both tracking precision and delay showed a comparable circadian rhythmicity.

Altered sleep–wake cycles and physical performance in athletes

Sleep-waking cycles are fundamental in human circadian rhythms and their disruption can have consequences for behaviour and performance. Such disturbances occur due to domestic or occupational schedules that do not permit normal sleep quotas, rapid travel across multiple meridians and extreme athletic and recreational endeavours where sleep is restricted or totally deprived. There are methodological issues in quantifying the physiological and performance consequences of alterations in the sleep-wake cycle if the effects on circadian rhythms are to be separated from the fatigue process. Individual requirements for sleep show large variations but chronic reduction in sleep can lead to immuno-suppression. There are still unanswered questions about the sleep needs of athletes, the role of 'power naps' and the potential for exercise in improving the quality of sleep.

Orienting and alerting: effect of 24 h of prolonged wakefulness

It is well known that a decrease in vigilance can easily occur during 24 h of continuous wakefulness, but no study has assessed whether and in what way extended wakefulness might affect spatial orienting. In other words, it is not clear what happens when a subject has to orient his attention during a state of poor vigilance, resulting from sleep loss or sustained wakefulness. The aim of this study was to investigate this issue. Twelve right-handed male subjects participated in the experiment, which took place on two consecutive days. On the first day, in order to evaluate baseline orienting attention, the subjects performed a covert orienting task (in which the cue stimuli generated endogenous shifts of attention), lasting 20 min; on the second day, during 24 h of prolonged wakefulness, the same task was performed 12 times, about every 120 min, beginning at 10.00 a.m. Results showed an overall slowing of reaction time across the sessions, indicating a linear decrease of vigilance. However, this vigilance decrease did not seem to affect attention-orienting mechanisms, suggesting that the two systems are independent of each other.