The Case for Addressing Operator Fatigue

Longitudinal association of health behaviors and health-related quality of life with military spouse readiness

BACKGROUND

Unhealthy behaviors impose costs on health-related quality of life (HRQOL) reducing productivity and readiness among military members (Hoge et al., JAMA 295:1023-32, 2006; Mansfield et al. 362:101-9, 2010). Among married personnel in particular, patterns of spouse health behaviors may play an interdependent role. As a result, the identification of military spouse health factors related to readiness may inform strategies to screen for and identify those in need of greater support and enhance readiness. This study explored behavioral and HRQOL predictors and potential mediators of military spouse readiness utilizing data from the Millennium Cohort Family Study.

METHODS

The analytic sample comprised of 3257 spouses of active-duty, non-separated service members who responded to both waves 1 and 2 of the survey. Sample characteristics are described with respect to demographics (e.g., age, sex, race/ethnicity, etc.), readiness measures (i.e., military satisfaction, lost workdays, health care utilization, military-related stress, and satisfaction), health behaviors (i.e., exercise, sleep, smoking, and alcohol use) and HRQOL (Veterans RAND 12-Item Short Form Survey). We conducted multivariate mediation analyses to evaluate the role of mental and physical HRQOL as mediators between the baseline health behaviors and the health readiness outcomes at follow-up, while adjusting for spouse and service member demographics.

RESULTS

HRQOL had direct effects for all five readiness outcomes examined. Multiple health behaviors (insomnia, smoking, binge drinking, and exercise) were further significantly associated with spouse readiness outcomes, although most effects were mediated through HRQOL, suggesting this may be a useful index of military spouse readiness. Insomnia was the specific health behavior most consistently associated with poorer readiness across outcomes, and effects were only partially mediated by physical and mental HRQOL.

CONCLUSIONS

The results show spouse health behaviors are directly and indirectly (through HRQOL) associated with readiness indicators. This suggests that assessments of modifiable health behaviors (e.g., insomnia symptoms) and mental and physical HRQOL are important indicators of readiness among military spouses and should be used to inform future programs designed to improve population health.

The Efficacy of a Multimodal Bedroom-Based 'Smart' Alarm System on Mitigating the Effects of Sleep Inertia

Previous work has demonstrated the modest impact of environmental interventions that manipulate lighting, sound, or temperature on sleep inertia symptoms. The current study sought to expand on previous work and measure the impact of a multimodal intervention that collectively manipulated light, sound, and ambient temperature on sleep inertia. Participants slept in the lab for four nights and were awoken each morning by either a traditional alarm clock or the multimodal intervention. Feelings of sleep inertia were measured each morning through Psychomotor Vigilance Test (PVT) assessments and ratings of sleepiness and mood at five time-points. While there was little overall impact of the intervention, the participant's chronotype and the length of the lighting exposure on intervention mornings both influenced sleep inertia symptoms. Moderate evening types who received a shorter lighting exposure (≤15 min) demonstrated more lapses relative to the control condition, whereas intermediate types exhibited a better response speed and fewer lapses. Conversely, moderate evening types who experienced a longer light exposure (>15 min) during the intervention exhibited fewer false alarms over time. The results suggest that the length of the environmental intervention may play a role in mitigating feelings of sleep inertia, particularly for groups who might exhibit stronger feelings of sleep inertia, including evening types.

Spontaneous attentional failures reflect multiplicative interactions of chronic sleep loss with acute sleep loss and circadian misalignment

OBJECTIVES

Acute and chronic sleep loss and circadian timing interact such that, depending on their combination, small or very large performance decrements are observed in tasks of attention. Here, we tested whether such nonlinear interactions extend to a physiological measure of spontaneous visual attentional failures, indicating a fundamental principle of sleep-wake regulation.

METHODS

Nine healthy volunteers completed an in-laboratory 3-week forced desynchrony protocol consisting of 12 consecutive 42.85-hour cycles with a sleep-wake ratio of 1:3.3. The protocol induced increasing chronic sleep loss, while extended wake (32.85 hours) and sleep episodes (10 hours) occurred at multiple circadian phases. Attentional failure rate was quantified from continuous electrooculograms (number of 30-second epochs with slow eye movements/h of wakefulness) as a function of time since scheduled wake (acute sleep loss), week of study (chronic sleep loss), and circadian (melatonin) phase.

RESULTS

During the first ∼8 hours awake, attentional failure rate was low, irrespective of the week. During the following wake hours, attentional failure rate increased steadily but at a faster rate in weeks 2 and 3 compared to week 1. The effects of acute and chronic sleep loss on attentional failure rate were magnified during the biological night compared to the biological day.

CONCLUSIONS

A single extended sleep episode can only temporarily reverse attentional impairment associated with chronic sleep loss. Multiplicative effects of acute and chronic sleep loss-further amplified during the biological night-substantiate the interaction of 2 homeostatic response mechanisms and caution against underestimating their disproportionate combined impact on performance, health, and safety.

OperatorEYEVP: Operator Dataset for Fatigue Detection Based on Eye Movements, Heart Rate Data, and Video Information

Detection of fatigue is extremely important in the development of different kinds of preventive systems (such as driver monitoring or operator monitoring for accident prevention). The presence of fatigue for this task should be determined with physiological and objective behavioral indicators. To develop an effective model of fatigue detection, it is important to record a dataset with people in a state of fatigue as well as in a normal state. We carried out data collection using an eye tracker, a video camera, a stage camera, and a heart rate monitor to record a different kind of signal to analyze them. In our proposed dataset, 10 participants took part in the experiment and recorded data 3 times a day for 8 days. They performed different types of activity (choice reaction time, reading, correction test Landolt rings, playing Tetris), imitating everyday tasks. Our dataset is useful for studying fatigue and finding indicators of its manifestation. We have analyzed datasets that have public access to find the best for this task. Each of them contains data of eye movements and other types of data. We evaluated each of them to determine their suitability for fatigue studies, but none of them fully fit the fatigue detection task. We evaluated the recorded dataset by calculating the correspondences between eye-tracking data and CRT (choice reaction time) that show the presence of fatigue.

Combining four screening tools for cost effective screening of OSA in train drivers: A UK experience

Background

Obstructive sleep apnoea (OSA) in drivers/workers has been implicated in railway and road traffic safety incidents; however, there are insufficient data on its prevalence and cost-effective screening methods.

Aim

This pragmatic study examines four OSA screening tools: the Epworth sleepiness scale (ESS), the STOP-Bang (SB), the adjusted neck circumference (ANC) and the body mass index (BMI), exploring their suitability and effectiveness separately and in combination.

Method

Using all four tools, 292 train drivers were opportunistically screened between 2016 and 2017. A polygraph (PG) test was carried out when OSA was suspected. Patients with an apnoea-hypopnea index (AHI) ≥5 were referred to a clinical specialist and reviewed annually. Those who had continuous positive airway pressure (CPAP) treatment were evaluated for compliance and control.

Results

Of the 40 patients who had PG testing, 3 and 23 participants met the ESS >10 and SB >4, criteria, respectively, whereas 25 participants each had an ANC >48 and a BMI >35 with a risk factor or ≥40 with none. OSA was detected in 3, 18 and 16 of them who met the ESS, SB and ANC criteria, respectively, and was positive for OSA in addition to 16 others who met the BMI criteria. A total of 28 (72%) were diagnosed with OSA.

Conclusion

Although when used individually, these screening methods are less effective/inadequate, combining them is easy, feasible and offers the maximum chance of OSA detection in train drivers.

Desynchronizing the sleep---wake cycle from circadian timing to assess their separate contributions to physiology and behaviour and to estimate intrinsic circadian period

Circadian clocks drive cyclic variations in many aspects of physiology, but some daily variations are evoked by periodic changes in the environment or sleep-wake state and associated behaviors, such as changes in posture, light levels, fasting or eating, rest or activity and social interactions; thus, it is often important to quantify the relative contributions of these factors. Yet, circadian rhythms and these evoked effects cannot be separated under typical 24-h day conditions, because circadian phase and the length of time awake or asleep co-vary. Nathaniel Kleitman's forced desynchrony (FD) protocol was designed to assess endogenous circadian rhythmicity and to separate circadian from evoked components of daily rhythms in multiple parameters. Under FD protocol conditions, light intensity is kept low to minimize its impact on the circadian pacemaker, and participants have sleep-wake state and associated behaviors scheduled to an imposed non-24-h cycle. The period of this imposed cycle, Τ, is chosen so that the circadian pacemaker cannot entrain to it and therefore continues to oscillate at its intrinsic period (τ, ~24.15 h), ensuring circadian components are separated from evoked components of daily rhythms. Here we provide detailed instructions and troubleshooting techniques on how to design, implement and analyze the data from an FD protocol. We provide two procedures: one with general guidance for designing an FD study and another with more precise instructions for replicating one of our previous FD studies. We discuss estimating circadian parameters and quantifying the separate contributions of circadian rhythmicity and the sleep-wake cycle, including statistical analysis procedures and an R package for conducting the non-orthogonal spectral analysis method that enables an accurate estimation of period, amplitude and phase.

The relative impact of injury and deployment on mental and physical quality of life among military service members

US service members injured in the recent conflicts in Iraq and Afghanistan were more likely to survive than those in previous conflicts because of advances in medicine and protective gear. However, there is limited research examining the long-term impact of injuries while deployed on physical and mental quality of life (QOL) among service members. We used data from two time-points with an average follow-up period of 4.27 years (SD = 2.13; n = 118,054) to prospectively examine the association between deployment and injury status with QOL. Data were derived from the Millennium Cohort Study surveys (2001 to 2016) and linked with the Department of Defense Trauma Registry (DoD-TR) among a cohort of US service members from all branches and components. The primary predictor (a combination of deployment and injury status) was comprised of the following four categories: 1) not deployed, 2) deployed and not injured, 3) deployed and non-battle injured, and 4) deployed and battle injured. Demographic, military, psychological and behavioral health, and life stress factors were adjusted for in multivariable models. Outcomes of interest were physical and mental QOL from the Short-Form Health Survey for Veterans (VR-36) measured at ~4 year follow-up. Between group comparisons indicated that those deployed and battle-injured had the greatest decline in both mental (-3.82) and physical (-10.13) QOL scores over time (p < .05). While deployment and injury status were associated with poorer mental and physical QOL in adjusted models; only the association between deployment and injury status with physical QOL was clinically meaningful (more than 2.5). In adjusted models, Time 1 mental and physical QOL explained most of the variance (23–25%) in Time 2 mental and physical health QOL as compared to other covariates (e.g., injury and deployment, and other sociodemographic factors increased variance by ~5%). Time 1 QOL was the most significant predictor of later QOL, but those injured while deployed experienced significant and meaningful decrements to long-term physical QOL. This suggests that prevention and rehabilitation interventions should focus on improving physical health among injured service members to avoid long-term adverse effects.

Longitudinal associations of military-related factors on self-reported sleep among U.S. service members

STUDY OBJECTIVES

Sleep loss is common in the military, which can negatively affect health and readiness; however, it is largely unknown how sleep varies over a military career. This study sought to examine the relationships between military-related factors and the new onset and reoccurrence of short sleep duration and insomnia symptoms.

METHODS

Millennium Cohort Study data were used to track U.S. military service members over time to examine longitudinal changes in sleep. Outcomes were self-reported average sleep duration (categorized as ≤5 hours, 6 hours, or 7-9 hours [recommended]) and/or insomnia symptoms (having trouble falling or staying asleep). Associations between military-related factors and the new onset and reoccurrence of these sleep characteristics were determined, after controlling for multiple health and behavioral factors.

RESULTS

Military-related factors consistently associated with an increased risk for new onset and/or reoccurrence of short sleep duration and insomnia symptoms included active duty component, Army or Marine Corps service, combat deployment, and longer than average deployment lengths. Military officers and noncombat deployers had decreased risk for either sleep characteristic. Time-in-service and separation from the military were complex factors; they lowered risk for ≤5 hours sleep but increased risk for insomnia symptoms.

CONCLUSIONS

Various military-related factors contribute to risk of short sleep duration and/or insomnia symptoms over time, although some factors affect these sleep characteristics differently. Also, even when these sleep characteristics remit, some military personnel have an increased risk of reoccurrence. Efforts to improve sleep prioritization and implement interventions targeting at-risk military populations, behaviors, and other significant factors are warranted.

How much sleep do you need? A comprehensive review of fatigue related impairment and the capacity to work or drive safely

In developed countries, deaths attributable to driving or working while intoxicated have steadily declined over recent decades. In part, this has been due to (a) public education programs about the risks and (b) the deterrence value associated with penalties and prosecutions based on an individual being 'deemed impaired' if they exceed a proscribed level of blood alcohol or drug concentration while driving/working. In contrast, the relative proportion of fatigue-related accidents have remained stubbornly high despite significant public and workplace education. As such, it may be useful to introduce the legal principle of 'deemed impaired' with respect to fatigue and/or sleep loss. A comprehensive review of the impairment and accident literature was performed, including 44 relevant publications. Findings from this review suggests that a driver or worker might reasonably be 'deemed impaired' once the amount of sleep falls below five hours in the prior 24. Building on the legal principles first outlined in recent New Jersey legislation (Maggie's Law), this review argues that an individual can reasonably be 'deemed impaired' based on prior sleep wake behaviour. In Maggie's Law, a driver can be indirectly 'deemed impaired' if they have not slept in the prior 24 h. Based on the extant literature, we argue that, relative to drug and alcohol intoxication, this may be overly conservative. While roadside measurement of fatigue and prior sleep-wake behavior is not yet possible, we suggest that public education programs should provide specific guidance on the amount of sleep required and that post-accident forensic examination of prior sleep wake behaviours may help the community to determine unsafe behaviours and liability more objectively than is currently the case.

Circadian misalignment increases mood vulnerability in simulated shift work

Night shift work can associate with an increased risk for depression. As night workers experience a 'misalignment' between their circadian system and daily sleep-wake behaviors, with negative health consequences, we investigated whether exposure to circadian misalignment underpins mood vulnerability in simulated shift work. We performed randomized within-subject crossover laboratory studies in non-shift workers and shift workers. Simulated night shifts were used to induce a misalignment between the endogenous circadian pacemaker and sleep/wake cycles (circadian misalignment), while environmental conditions and food intake were controlled. Circadian misalignment adversely impacted emotional state, such that mood and well-being levels were significantly decreased throughout 4 days of continuous exposure to circadian misalignment in non-shift workers, as compared to when they were under circadian alignment (interaction of "circadian alignment condition" vs. "day", mood: p < 0.001; well-being: p < 0.001; adjusted p-values). Similarly, in shift workers, mood and well-being levels were significantly reduced throughout days of misalignment, as compared to circadian alignment (interaction of "circadian alignment condition" vs. "day", mood: p = 0.002; well-being: p = 0.002; adjusted p-values). Our findings indicate that circadian misalignment is an important biological component for mood vulnerability, and that individuals who engage in shift work are susceptible to its deleterious mood effects.

Alarm tones, music and their elements: Analysis of reported waking sounds to counteract sleep inertia

Sleep inertia is a potentially dangerous reduction in human alertness and occurs 0-4 hours after waking. The type of sound people set as their alarm for waking has been shown to reduce the effects of sleep inertia, however, the elemental musical factors that underpin these waking sounds and their relationships remain unclear. The goal of this research is to understand how a particular sound or music chosen to assist waking may counteract sleep inertia, and more specifically, what elements of these sounds may contribute to its reduction. Through an anonymous, self-report online questionnaire, fifty participants (N = 50) reported attributes of their preferred waking sound, their feeling towards the waking sound, and perceived sleep inertia after waking. This data enabled the analysis and comparison between these responses to identify statistically significant relationships. Our results did not return any significant association between sleep inertia and the reported waking sound type, nor the subject's feeling towards their sound. However, the analysis did reveal that a sound which is ranked as melodic by participants shows a significant relationship to reports of reductions in perceived sleep inertia, and in contrast, sound rated as neutral (neither unmelodic nor melodic) returns a significant relationship to the reports of increases in perceived sleep inertia. Additionally, our secondary analysis revealed that a sound rated as melodic is considered to be more rhythmic than a melodically neutral interpretation. Together these findings raise questions regarding the impact melody and rhythm may hold with respect to sleep inertia intensity. Considering that the implementation of auditory assisted awakening is a common occurrence, the musical elements of a chosen waking sound may be an area to further interrogate with respect to counteracting sleep inertia.

Scheduled afternoon-evening sleep leads to better night shift performance in older adults

OBJECTIVES

This study investigated whether an intervention designed to reduce homeostatic sleep pressure would improve night shift performance and alertness in older adults.

METHODS

Non-shift workers aged 57.9±4.6 (mean±SD) worked four day (07:00-15:00) and four night shifts (23:00-07:00). Two intervention groups were instructed to remain awake until ~13:00 after each night shift: the sleep timing group (ST; n=9) was instructed to spend 8 hours in bed attempting sleep, and the sleep ad-lib group (n=9) was given no further sleep instructions. A control group (n=9) from our previous study was not given any sleep instructions. Hourly Karolinska Sleepiness Scales and Psychomotor Vigilance Tasks assessed subjective sleepiness and performance.

RESULTS

The ST group maintained their day shift sleep durations on night shifts, whereas the control group slept less. The ST group were able to maintain stable performance and alertness across the initial part of the night shift, while the control group's alertness and performance declined across the entire night. Wake duration before a night shift negatively impacted sustained attention and self-reported sleepiness but not reaction time, whereas sleep duration before a night shift affected reaction time and ability to sustain attention but not self-reported sleepiness.

CONCLUSIONS

A behavioural change under the control of the individual worker, spending 8 hours in bed and waking close to the start of the night shift, allowed participants to acquire more sleep and improved performance on the night shift in older adults. Both sleep duration and timing are important factors for night shift performance and self-reported sleepiness.

Effects of circadian misalignment on cognition in chronic shift workers

Shift work is associated with increased human operational errors, presumably due to the circadian timing system that inhibits optimal cognitive function during the night. Circadian misalignment, which is the misalignment between the circadian pacemaker and behavioral/environmental cycles, impairs cognitive performance in non-shift workers. However, it remains uncertain whether the adverse cognitive consequences of circadian misalignment are also observed in chronic shift workers. Thus, we investigated the effects of circadian misalignment on cognitive performance in chronic shift workers. Using a randomized, cross-over design that simulated day shift work (circadian alignment) and night shift work (circadian misalignment), we show that circadian misalignment increases cognitive vulnerability on sustained attention, information processing and visual-motor performance, particularly after more than 10 hours of scheduled wakefulness. Furthermore, their increased levels of subjective sleepiness and their decreased sleep efficiency were significantly associated with impaired sustained attention and visual-motor performance. Our data suggest that circadian misalignment dramatically deteriorates cognitive performance in chronic shift workers under circadian misalignment. This increased cognitive vulnerability may have important safety consequences, given the increasing number of nighttime jobs that crucially rely on the availability of cognitive resources.

Selective neuronal lapses precede human cognitive lapses following sleep deprivation

Sleep deprivation is a major source of morbidity with widespread health effects, including increased risk of hypertension, diabetes, obesity, heart attack, and stroke. Moreover, sleep deprivation brings about vehicle accidents and medical errors and is therefore an urgent topic of investigation. During sleep deprivation, homeostatic and circadian processes interact to build up sleep pressure, which results in slow behavioral performance (cognitive lapses) typically attributed to attentional thalamic and frontoparietal circuits, but the underlying mechanisms remain unclear. Recently, through study of electroencephalograms (EEGs) in humans and local field potentials (LFPs) in nonhuman primates and rodents it was found that, during sleep deprivation, regional 'sleep-like' slow and theta (slow/theta) waves co-occur with impaired behavioral performance during wakefulness. Here we used intracranial electrodes to record single-neuron activities and LFPs in human neurosurgical patients performing a face/nonface categorization psychomotor vigilance task (PVT) over multiple experimental sessions, including a session after full-night sleep deprivation. We find that, just before cognitive lapses, the selective spiking responses of individual neurons in the medial temporal lobe (MTL) are attenuated, delayed, and lengthened. These 'neuronal lapses' are evident on a trial-by-trial basis when comparing the slowest behavioral PVT reaction times to the fastest. Furthermore, during cognitive lapses, LFPs exhibit a relative local increase in slow/theta activity that is correlated with degraded single-neuron responses and with baseline theta activity. Our results show that cognitive lapses involve local state-dependent changes in neuronal activity already present in the MTL.

Stressful work characteristics, health indicators and work behavior: the case of machine operators

This article shows the results of research on psychosocial risks for a group of machine and plant operators (n = 1014) from the construction, chemical, energy, mining, metal and food industries in Poland. The Psychosocial Risk Scale designed in Nofer Institute of Occupational Medicine (NIOM) by Moscicka-Teske and Potocka was used to indicate the occurrence of general and specific occupational stressors and the level of their stressfulness. The results revealed that the studied machine and plant operators experience job context stress - related to working environment features concerning work organization - more frequently than job content stressors - related to the type of tasks they perform. Moreover, a correlation analysis between work features and the health and occupational functioning of the respondents revealed significant but weak relationships between the variables (from -0.08 to -0.23). Comparative analysis revealed the differences between the studied sectors. Such a comparison makes it possible to set goals for each sector and to attempt to improve the distinctive areas.

Sleep-deprived motor vehicle operators are unfit to drive: a multidisciplinary expert consensus statement on drowsy driving

OBJECTIVES

This article presents the consensus findings of the National Sleep Foundation Drowsy Driving Consensus Working Group, which was an expert panel assembled to establish a consensus statement regarding sleep-related driving impairment.

METHODS

The National Sleep Foundation assembled a expert panel comprised of experts from the sleep community and experts appointed by stakeholder organizations. A systematic literature review identified 346 studies that were abstracted and provided to the panelists for review. A modified Delphi RAND/UCLA Appropriateness Method with 2 rounds of voting was used to reach consensus.

RESULTS

A final consensus was reached that sleep deprivation renders motorists unfit to drive a motor vehicle. After reviewing growing evidence of impairment and increased crash risk among drivers who obtained less than optimal sleep duration in the preceding 24 hours, the panelists recognized the need for public policy guidance as to when it is certainly unsafe to drive. Toward this end, the panelists agreed upon the following expert consensus statement: "Drivers who have slept for two hours or less in the preceding 24 hours are not fit to operate a motor vehicle." Panelists further agreed that most healthy drivers would likely be impaired with only 3 to 5 hours of sleep during the prior 24 hours.

CONCLUSIONS

There is consensus among experts that healthy individuals who have slept for 2 hours or less in the preceding 24 hours are too impaired to safely operate a motor vehicle. Prevention of drowsy driving will require sustained and collaborative effort from multiple stakeholders. Implications and limitations of the consensus recommendations are discussed.