Underestimating the societal costs of impaired alertness: safety, health and productivity risks

Impact of one night of sleep restriction on sleepiness and cognitive function: A systematic review and meta-analysis

Detrimental consequences of chronic sleep restriction on cognitive function are well established in the literature. However, effects of a single night of sleep restriction remain equivocal. Therefore, we synthesized data from 44 studies to investigate effects of sleep restriction to 2-6 h sleep opportunity on sleepiness and cognition in this meta-analysis. We investigated subjective sleepiness, sustained attention, choice reaction time, cognitive throughput, working memory, and inhibitory control. Results revealed a significant increase in subjective sleepiness following one night of sleep restriction (Standardized Mean Difference (SMD) = 0.986, p < 0.001), while subjective sleepiness was not associated with sleep duration during sleep restriction (β = -0.214, p = 0.039, significance level 0.01). Sustained attention, assessed via common 10-min tasks, was impaired, as demonstrated through increased reaction times (SMD = 0.512, p < 0.001) and attentional lapses (SMD = 0.489, p < 0.001). However, the degree of impaired attention was not associated with sleep duration (ps > 0.090). We did not find significant effects on choice reaction time, cognitive throughput, working memory, or inhibitory control. Overall, results suggest that a single night of restricted sleep can increase subjective sleepiness and impair sustained attention, a cognitive function crucial for everyday tasks such as driving.

Doctors' alertness, contentedness and calmness before and after night shifts: a latent profile analysis

BACKGROUND

While night shifts are crucial for patient care, they threaten doctors' well-being and performance. Knowledge of how the impact of night shifts differs for doctors is needed to attenuate the adverse effects of night shifts. This study aimed to obtain more precise insight into doctors' feelings surrounding night shift by: identifying profiles based on doctors' alertness, contentedness and calmness scores before and after night shifts (research question (RQ) 1); assessing how doctors' pre- and post-shift profiles change (RQ2); and determining associations of doctors' demographics and shift circumstances with alertness, contentedness and calmness change (RQ3).

METHODS

Latent Profile Analysis using doctors' pre- and post-shift self-rated alertness, contentedness and calmness scores was employed to identify pre- and post-shift profiles (RQ1). A cross-tabulation revealed pre- and post-shift profile changes (RQ2). Multiple regressions determined associations of demographics (i.e. age, sex, specialty) and night shift circumstances (i.e. hours worked pre-call, hours awake pre-call, shift duration, number of consecutive shifts, total hours of sleep) with alertness, contentedness and calmness change (RQ3).

RESULTS

In total, 211 doctors participated with a mean age of 39.8 ± 10 years; 47.4% was male. The participants included consultants (46.4%) and trainees (53.6%) of the specialties surgery (64.5%) and obstetrics/gynaecology (35.5%). Three pre-shift (Indifferent, Ready, Engaged) and four post-shift profiles (Lethargic, Tired but satisfied, Excited, Mindful) were found. Most doctors changed from Ready to Tired but satisfied, with alertness reducing most. Age, specialty, sleep, shift duration and the number of consecutive shifts associated with alertness, contentedness and calmness changes.

CONCLUSIONS

The results provided nuanced insight into doctors' feelings before and after night shifts. Future research may assess whether specific subgroups benefit from tailored interventions.

The Psychomotor Cognition Test for Measurement of Sleepiness/Fatigue on a Touch Screen. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2023;2023:1-4. [PMID: 38083744 DOI: 10.1109/embc40787.2023.10340988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

The Psychomotor Vigilance Test (PVT) is a simple and reliable performance test that measures sustained attention, alertness level, and fatigue level. The PVT is a convenient tool that can be used in real time in situ through a mobile device without the assistance of experts and therefore can be used to improve safety and prevent accidents. However, the original PVT is vulnerable to the subject's intentional concentration on the test, and the variance range among tests is narrow; these factors limit its usefulness in classifying the level of fatigue. This study overcome these limitations and develop the Psychomotor Cognition Test (PCT) by transforming the PVT into a tool that stably classifies fatigue levels, still requiring a short period of time. In the PCT, compared to the PVT, reaction time is significantly longer, and success rate is significantly lower (both p<0.0001). Whereas reaction time and success rate of the PVT do not show a significant correlation with fatigue level, those of the PCT show significant correlations with fatigue level, respectively (p<0.001). This study suggests that the PCT can be used in real time in situ as a risk management tool for workers performing dangerous tasks and can become an even more powerful tool when combined with other physiological indicators.

Guiding principles for determining work shift duration and addressing the effects of work shift duration on performance, safety, and health: guidance from the American Academy of Sleep Medicine and the Sleep Research Society

CITATION

Risks associated with fatigue that accumulates during work shifts have historically been managed through working time arrangements that specify fixed maximum durations of work shifts and minimum durations of time off. By themselves, such arrangements are not sufficient to curb risks to performance, safety, and health caused by misalignment between work schedules and the biological regulation of waking alertness and sleep. Science-based approaches for determining shift duration and mitigating associated risks, while addressing operational needs, require: (1) a recognition of the factors contributing to fatigue and fatigue-related risks; (2) an understanding of evidence-based countermeasures that may reduce fatigue and/or fatigue-related risks; and (3) an informed approach to selecting workplace-specific strategies for managing work hours. We propose a series of guiding principles to assist stakeholders with designing a shift duration decision-making process that effectively balances the need to meet operational demands with the need to manage fatigue-related risks.

Guiding principles for determining work shift duration and addressing the effects of work shift duration on performance, safety, and health: guidance from the American Academy of Sleep Medicine and the Sleep Research Society

Risks associated with fatigue that accumulates during work shifts have historically been managed through working time arrangements that specify fixed maximum durations of work shifts and minimum durations of time off. By themselves, such arrangements are not sufficient to curb risks to performance, safety, and health caused by misalignment between work schedules and the biological regulation of waking alertness and sleep. Science-based approaches for determining shift duration and mitigating associated risks, while addressing operational needs, require: (1) a recognition of the factors contributing to fatigue and fatigue-related risks; (2) an understanding of evidence-based countermeasures that may reduce fatigue and/or fatigue-related risks; and (3) an informed approach to selecting workplace-specific strategies for managing work hours. We propose a series of guiding principles to assist stakeholders with designing a shift duration decision-making process that effectively balances the need to meet operational demands with the need to manage fatigue-related risks.

Trends and knowledge gaps in field research investigating effects of anthropogenic noise

Anthropogenic noise is a globally widespread sensory pollutant, recognized as having potentially adverse effects on function, demography, and physiology in wild animals. Human population growth and associated changes in urbanization, transportation, and resource extraction all contribute to anthropogenic noise and are predicted to increase in the coming decades. Wildlife exposure to anthropogenic noise is expected to rise correspondingly. Data collected through field research are uniquely important in advancing understanding of the real-world repercussions of human activity on wildlife. We, therefore, performed a systematic review of literature published from 2008 to 2018 that reported on field investigations of anthropogenic noise impacts. We evaluated publication metrics (e.g., publication rates and journal type), geographical distribution of studies, study subject, and methods used. Research activity increased markedly over the assessment period. However, there was a pronounced geographical bias in research, with most being conducted in North America or Europe, and a notable focus on terrestrial environments. Fewer than one-fifth of terrestrial studies were located in rural areas likely to experience urbanization by 2030, meaning data on ecosystems most likely to be affected by future changes are not being gathered. There was also bias in the taxonomic groups investigated. Most research was conducted on birds and aquatic mammals, whereas terrestrial mammals, reptiles, amphibians, fish, and invertebrates received limited attention. Almost all terrestrial studies examined diurnal species, despite evidence that nocturnality is the prevailing animal activity pattern. Nearly half the studies investigated effects of road or urban noise; the bulk of research was restricted to functional, rather than physiological or demographic consequences. Few experimental studies addressed repercussions of long-term exposure to anthropogenic noise or long-term postexposure effects, and multiple noise types or levels were rarely compared. Tackling these knowledge gaps will be vital for successful management of the effects of increasing wildlife exposure to anthropogenic noise.

Psychometric evaluation of the Chinese version of the Toronto Hospital Alertness Test

Background

Alertness is an important part of attention which is different from the opposite of sleepiness. This study aimed to translate and assess the measurement properties of the Toronto Hospital Alertness Test (THAT) in Hong Kong Chinese population.

Methods

The standard forward-backward translation procedure and cognitive debriefing were conducted to obtain the Chinese THAT. One hundred Chinese adults completed the Chinese THAT, the Center for Epidemiological Studies Depression Scale (CES-D), the Pittsburgh Sleep Quality Index (PSQI), and the Athens Insomnia Scale (AIS) by telephone interviews.

Results

The factorial validity was assessed by confirmatory factor analysis, and the internal reliability was examined by coefficient omega. The two negatively worded items of the THAT had low factor loadings and were removed. One more item was removed based on the modification indices of the eight-item model. The remaining seven-item THAT showed satisfactory unidimensionality with root mean square error of approximation (RMSEA) = 0.06, standardized root mean square residual (SRMR) = 0.08, and comparative fit index (CFI) = 1.00. The coefficient omega of the seven-item Chinese THAT was 0.80 (95% CI: 0.74–0.86). Convergent validity was demonstrated with THAT moderately associated with CES-D (r = − 0.45, P < 0.01), PSQI (r = − 0.40, P < 0.01), and AIS (r = − 0.45, P < 0.01).

Conclusions

The Chinese version of THAT demonstrated acceptable reliability and validity in a Chinese population.

A Generic Design of Driver Drowsiness and Stress Recognition Using MOGA Optimized Deep MKL-SVM

Driver drowsiness and stress are major causes of traffic deaths and injuries, which ultimately wreak havoc on world economic loss. Researchers are in full swing to develop various algorithms for both drowsiness and stress recognition. In contrast to existing works, this paper proposes a generic model using multiple-objective genetic algorithm optimized deep multiple kernel learning support vector machine that is capable to recognize both driver drowsiness and stress. This algorithm simplifies the research formulations and model complexity that one model fits two applications. Results reveal that the proposed algorithm achieves an average sensitivity of 99%, specificity of 98.3% and area under the receiver operating characteristic curve (AUC) of 97.1% for driver drowsiness recognition. For driver stress recognition, the best performance is yielded with average sensitivity of 98.7%, specificity of 98.4% and AUC of 96.9%. Analysis also indicates that the proposed algorithm using multiple-objective genetic algorithm has better performance compared to the grid search method. Multiple kernel learning enhances the performance significantly compared to single typical kernel. Compared with existing works, the proposed algorithm not only achieves higher accuracy but also addressing the typical issues of dataset in simulated environment, no cross-validation and unreliable measurement stability of input signals.

Neurobehavioural complications of sleep deprivation: Shedding light on the emerging role of neuroactive steroids

Sleep deprivation (SD) is associated with a broad spectrum of cognitive and behavioural complications, including emotional lability and enhanced stress reactivity, as well as deficits in executive functions, decision making and impulse control. These impairments, which have profound negative consequences on the health and productivity of many individuals, reflect alterations of the prefrontal cortex (PFC) and its connectivity with subcortical regions. However, the molecular underpinnings of these alterations remain elusive. Our group and others have begun examining how the neurobehavioural outcomes of SD may be influenced by neuroactive steroids, a family of molecules deeply implicated in sleep regulation and the stress response. These studies have revealed that, similar to other stressors, acute SD leads to increased synthesis of the neurosteroid allopregnanolone in the PFC. Whereas this up-regulation is likely aimed at counterbalancing the detrimental impact of oxidative stress induced by SD, the increase in prefrontal allopregnanolone levels contributes to deficits in sensorimotor gating and impulse control, signalling a functional impairment of PFC. This scenario suggests that the synthesis of neuroactive steroids during acute SD may be enacted as a neuroprotective response in the PFC; however, such compensation may in turn set off neurobehavioural complications by interfering with the corticolimbic connections responsible for executive functions and emotional regulation.

Working Time Society consensus statements: Prescriptive rule sets and risk management-based approaches for the management of fatigue-related risk in working time arrangements

Traditionally, working time arrangements to limit fatigue-related risk have taken a prescriptive approach, which sets maximum shift durations in order to prevent excessive buildup of fatigue (and the associated increased risk) within shifts and sets minimum break durations to allow adequate time for rest and recovery within and/or between shifts. Prescriptive rule sets can be successful when, from a fatigue-related risk standpoint, they classify safe work hours as permitted and unsafe work hours as not permitted. However, prescriptive rule sets ignore important aspects of the biological factors (such as the interaction between circadian and homeostatic processes) that drive fatigue, which are critical modulators of the relationship between work hours and fatigue-related risk. As such, in around-the-clock operations when people must work outside of normal daytime hours, the relationship between regulatory compliance and safety tends to break down, and thus these rule sets become less effective. To address this issue, risk management-based approaches have been designed to regulate the procedures associated with managing fatigue-related risk. These risk management-based approaches are suitable for nighttime operations and a variety of other non-standard work schedules, and can be tailored to the particular job or industry. Although the purpose of these fatigue risk management approaches is to curb fatigue risk, fatigue risk cannot be measured directly. Thus, the goal is not on regulating fatigue risk per se, but rather to put in place procedures that serve to address fatigue before, during, and after potential fatigue-related incidents. Examples include predictive mathematical modeling of fatigue for work scheduling, proactive fatigue monitoring in the workplace, and reactive post-incident follow-up. With different risks and different needs across industries, there is no "one size fits all" approach to managing fatigue-related risk. However, hybrid strategies combining prescriptive rule sets and risk management-based approaches can create the flexibility necessary to reduce fatigue-related risk based on the specific needs of different work environments while maintaining appropriate regulatory oversight.

Shining evolutionary light on human sleep and sleep disorders

Sleep is essential to cognitive function and health in humans, yet the ultimate reasons for sleep—i.e. ‘why’ sleep evolved—remain mysterious. We integrate findings from human sleep studies, the ethnographic record, and the ecology and evolution of mammalian sleep to better understand sleep along the human lineage and in the modern world. Compared to other primates, sleep in great apes has undergone substantial evolutionary change, with all great apes building a sleeping platform or ‘nest’. Further evolutionary change characterizes human sleep, with humans having the shortest sleep duration, yet the highest proportion of rapid eye movement sleep among primates. These changes likely reflect that our ancestors experienced fitness benefits from being active for a greater portion of the 24-h cycle than other primates, potentially related to advantages arising from learning, socializing and defending against predators and hostile conspecifics. Perspectives from evolutionary medicine have implications for understanding sleep disorders; we consider these perspectives in the context of insomnia, narcolepsy, seasonal affective disorder, circadian rhythm disorders and sleep apnea. We also identify how human sleep today differs from sleep through most of human evolution, and the implications of these changes for global health and health disparities. More generally, our review highlights the importance of phylogenetic comparisons in understanding human health, including well-known links between sleep, cognitive performance and health in humans.

Hearing difficulty and tinnitus among U.S. workers and non-workers in 2007

BACKGROUND

Hearing loss and tinnitus are two potentially debilitating physical conditions affecting many people in the United States. The purpose of this study was to estimate the prevalence of hearing difficulty, tinnitus, and their co-occurrence within U.S.

METHODS

Data from the 2007 National Health Interview Survey (NHIS) were examined. Weighted prevalence and adjusted prevalence ratios for self-reported hearing difficulty, tinnitus, and their co-occurrence were estimated and compared by demographic, among workers with and without occupational noise exposure, and across industries and occupations.

RESULTS

Seven percent of U.S. workers never exposed to occupational noise had hearing difficulty, 5% had tinnitus and 2% had both conditions. However, among workers who had ever been exposed to occupational noise, the prevalence was 23%, 15%, and 9%, respectively (P < 0.0001).

CONCLUSIONS

Hearing difficulty and tinnitus are prevalent in the U.S.; especially among noise-exposed workers. Improved strategies for hearing conservation or better implementation are needed.

Genotype vs. Phenotype and the Rise of Non-Communicable Diseases: The Importance of Lifestyle Behaviors During Childhood

Despite continued research and growing public awareness, the incidence of non-communicable diseases (NCD) continues to accelerate. While a person may have a genetic predisposition to certain NCDs, the rapidly changing epidemiology of NCDs points to the importance of environmental, social, and behavioural determinants of health. Specifically, three lifestyle behaviours expose children to important environmental cues and stressors: physical activity, nutritional intake, and sleep behaviour. Failure to expose children to proper gene-environment interactions, through the aforementioned lifestyle behaviours, can and will predispose children to the development of NCDs. Reengineering the environments of children can induce a paradigm shift, from a predominantly biomedical health model of treating symptomology, to a more holistic model based on encouraging appropriate behavioral decisions and optimal health.

Feedback Blunting: Total Sleep Deprivation Impairs Decision Making that Requires Updating Based on Feedback

STUDY OBJECTIVES

To better understand the sometimes catastrophic effects of sleep loss on naturalistic decision making, we investigated effects of sleep deprivation on decision making in a reversal learning paradigm requiring acquisition and updating of information based on outcome feedback.

DESIGN

Subjects were randomized to a sleep deprivation or control condition, with performance testing at baseline, after 2 nights of total sleep deprivation (or rested control), and following 2 nights of recovery sleep. Subjects performed a decision task involving initial learning of go and no go response sets followed by unannounced reversal of contingencies, requiring use of outcome feedback for decisions. A working memory scanning task and psychomotor vigilance test were also administered.

SETTING

Six consecutive days and nights in a controlled laboratory environment with continuous behavioral monitoring.

SUBJECTS

Twenty-six subjects (22-40 y of age; 10 women).

INTERVENTIONS

Thirteen subjects were randomized to a 62-h total sleep deprivation condition; the others were controls.

MEASUREMENTS AND RESULTS

Unlike controls, sleep deprived subjects had difficulty with initial learning of go and no go stimuli sets and had profound impairment adapting to reversal. Skin conductance responses to outcome feedback were diminished, indicating blunted affective reactions to feedback accompanying sleep deprivation. Working memory scanning performance was not significantly affected by sleep deprivation. And although sleep deprived subjects showed expected attentional lapses, these could not account for impairments in reversal learning decision making.

CONCLUSIONS

Sleep deprivation is particularly problematic for decision making involving uncertainty and unexpected change. Blunted reactions to feedback while sleep deprived underlie failures to adapt to uncertainty and changing contingencies. Thus, an error may register, but with diminished effect because of reduced affective valence of the feedback or because the feedback is not cognitively bound with the choice. This has important implications for understanding and managing sleep loss-induced cognitive impairment in emergency response, disaster management, military operations, and other dynamic real-world settings with uncertain outcomes and imperfect information.

Insomnia in shift work

BACKGROUND

Shift work disorder involves insomnia and/or excessive sleepiness associated with the work schedule. The present study examined the impact of insomnia on the perceived physical and psychological health of adults working on night and rotating shift schedules compared to day workers.

METHODS

A total of 418 adults (51% women, mean age 41.4 years), including 51 night workers, 158 rotating shift workers, and 209 day workers were selected from an epidemiological study. An algorithm was used to classify each participant of the two groups (working night or rotating shifts) according to the presence or absence of insomnia symptoms. Each of these individuals was paired with a day worker according to gender, age, and income. Participants completed several questionnaires measuring sleep, health, and psychological variables.

RESULTS

Night and rotating shift workers with insomnia presented a sleep profile similar to that of day workers with insomnia. Sleep time was more strongly related to insomnia than to shift work per se. Participants with insomnia in the three groups complained of anxiety, depression, and fatigue, and reported consuming equal amounts of sleep-aid medication. Insomnia also contributed to chronic pain and otorhinolaryngology problems, especially among rotating shift workers. Work productivity and absenteeism were more strongly related to insomnia.

CONCLUSION

The present study highlights insomnia as an important component of the sleep difficulties experienced by shift workers. Insomnia may exacerbate certain physical and mental health problems of shift workers, and impair their quality of life.

Sleep fragmentation in mice induces nicotinamide adenine dinucleotide phosphate oxidase 2-dependent mobilization, proliferation, and differentiation of adipocyte progenitors in visceral white adipose tissue

BACKGROUND

Chronic sleep fragmentation (SF) without sleep curtailment induces increased adiposity. However, it remains unclear whether mobilization, proliferation, and differentiation of adipocyte progenitors (APs) occurs in visceral white adipose tissue (VWAT), and whether nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (Nox2) activity plays a role.

METHODS

Changes in VWAT depot cell size and AP proliferation were assessed in wild-type and Nox2 null male mice exposed to SF and control sleep (SC). To assess mobilization, proliferation, and differentiation of bone marrow mesenchymal stem cells (BM-MSC), Sca-1+ bone marrow progenitors were isolated from GFP+ or RFP+ mice, and injected intravenously to adult male mice (C57BL/6) previously exposed to SF or SC.

RESULTS

In comparison with SC, SF was associated with increased weight accrual at 3 w and thereafter, larger subcutaneous and visceral fat depots, and overall adipocyte size at 8 w. Increased global AP numbers in VWAT along with enhanced AP BrDU labeling in vitro and in vivo emerged in SF. Systemic injections of GFP+ BM-MSC resulted in increased AP in VWAT, as well as in enhanced differentiation into adipocytes in SF-exposed mice. No differences occurred between SF and SC in Nox2 null mice for any of these measurements.

CONCLUSIONS

Chronic sleep fragmentation (SF) induces obesity in mice and increased proliferation and differentiation of adipocyte progenitors (AP) in visceral white adipose tissue (VWAT) that are mediated by increased Nox2 activity. In addition, enhanced migration of bone marrow mesenchymal stem cells from the systemic circulation into VWAT, along with AP differentiation, proliferation, and adipocyte formation occur in SF-exposed wild-type but not in oxidase 2 (Nox2) null mice. Thus, Nox2 may provide a therapeutic target to prevent obesity in the context of sleep disorders.

Prolonged sleep fragmentation of mice exacerbates febrile responses to lipopolysaccharide

BACKGROUND

Sleep disruption is a frequent occurrence in modern society. Whereas many studies have focused on the consequences of total sleep deprivation, few have investigated the condition of sleep disruption.

NEW METHOD

We disrupted sleep of mice during the light period for 9 consecutive days using an intermittently rotating disc.

RESULTS

Electroencephalogram (EEG) data demonstrated that non-rapid eye movement (NREM) sleep was severely fragmented and REM sleep was essentially abolished during the 12h light period. During the dark period, when sleep was not disrupted, neither NREM sleep nor REM sleep times differed from control values. Analysis of the EEG revealed a trend for increased power in the peak frequency of the NREM EEG spectra during the dark period. The fragmentation protocol was not overly stressful as body weights and water consumption remained unchanged, and plasma corticosterone did not differ between mice subjected to 3 or 9 days of sleep disruption and home cage controls. However, mice subjected to 9 days of sleep disruption by this method responded to lipopolysaccharide with an exacerbated febrile response.

COMPARISON WITH EXISTING METHODS

Existing methods to disrupt sleep of laboratory rodents often subject the animal to excessive locomotion, vibration, or sudden movements. This method does not suffer from any of these confounds.

CONCLUSIONS

This study demonstrates that prolonged sleep disruption of mice exacerbates febrile responses to lipopolysaccharide. This device provides a method to determine mechanisms by which chronic insufficient sleep contributes to the etiology of many pathologies, particularly those with an inflammatory component.

Prevalence of hearing loss in the United States by industry

BACKGROUND

Twenty-two million workers are exposed to hazardous noise in the United States. The purpose of this study is to estimate the prevalence of hearing loss among U.S. industries.

METHODS

We examined 2000-2008 audiograms for male and female workers ages 18-65, who had higher occupational noise exposures than the general population. Prevalence and adjusted prevalence ratios (PRs) for hearing loss were estimated and compared across industries.

RESULTS

In our sample, 18% of workers had hearing loss. When compared with the Couriers and Messengers industry sub-sector, workers employed in Mining (PR = 1.65, CI = 1.57-1.73), Wood Product Manufacturing (PR = 1.65, CL = 1.61-1.70), Construction of Buildings (PR = 1.52, CI = 1.45-1.59), and Real Estate and Rental and Leasing (PR = 1.61, CL = 1.51-1.71) [corrected] had higher risks for hearing loss.

CONCLUSIONS

Workers in the Mining, Manufacturing, and Construction industries need better engineering controls for noise and stronger hearing conservation strategies. More hearing loss research is also needed within traditional "low-risk" industries like Real Estate.

Sleep and sleepiness among first-time postpartum parents: a field- and laboratory-based multimethod assessment

The study aim was to compare sleep, sleepiness, fatigue, and neurobehavioral performance among first-time mothers and fathers during their early postpartum period. Participants were 21 first-time postpartum mother-father dyads (N = 42) and seven childless control dyads (N = 14). Within their natural environment, participants completed 1 week of wrist actigraphy monitoring, along with multi-day self-administered sleepiness, fatigue, and neurobehavioral performance measures. The assessment week was followed by an objective laboratory-based test of sleepiness. Mothers obtained more sleep compared to fathers, but mothers' sleep was more disturbed by awakenings. Fathers had greater objectively measured sleepiness than mothers. Mothers and fathers did not differ on subjectively measured sleep quality, sleepiness, or fatigue; however, mothers had worse neurobehavioral performance than fathers. Compared to control dyads, postpartum parents experienced greater sleep disturbance, sleepiness, and sleepiness-associated impairments. Study results can inform social policy, postpartum sleep intervention development, and research on postpartum family systems and mechanisms that propagate sleepiness.

Health consequences of circadian disruption in humans and animal models

Daily rhythms in behavior and physiology are programmed by a hierarchical collection of biological clocks located throughout the brain and body, known as the circadian system. Mounting evidence indicates that disruption of circadian regulation is associated with a wide variety of adverse health consequences, including increased risk for premature death, cancer, metabolic syndrome, cardiovascular dysfunction, immune dysregulation, reproductive problems, mood disorders, and learning deficits. Here we review the evidence for the pervasive effects of circadian disruption in humans and animal models, drawing from both environmental and genetic studies, and identify questions for future research.

Deconstructing and reconstructing cognitive performance in sleep deprivation

Mitigation of cognitive impairment due to sleep deprivation in operational settings is critical for safety and productivity. Achievements in this area are hampered by limited knowledge about the effects of sleep loss on actual job tasks. Sleep deprivation has different effects on different cognitive performance tasks, but the mechanisms behind this task-specificity are poorly understood. In this context it is important to recognize that cognitive performance is not a unitary process, but involves a number of component processes. There is emerging evidence that these component processes are differentially affected by sleep loss. Experiments have been conducted to decompose sleep-deprived performance into underlying cognitive processes using cognitive-behavioral, neuroimaging and cognitive modeling techniques. Furthermore, computational modeling in cognitive architectures has been employed to simulate sleep-deprived cognitive performance on the basis of the constituent cognitive processes. These efforts are beginning to enable quantitative prediction of the effects of sleep deprivation across different task contexts. This paper reviews a rapidly evolving area of research, and outlines a theoretical framework in which the effects of sleep loss on cognition may be understood from the deficits in the underlying neurobiology to the applied consequences in real-world job tasks.

Changing the waveform of circadian rhythms: considerations for shift-work

Circadian disruption in shift-work is common and has deleterious effects on health and performance. Current efforts to mitigate these harms reasonably focus on the phase of the circadian pacemaker, which unfortunately in humans, shifts slowly and often incompletely. Temporal reorganization of rhythmic waveform (i.e., the shape of its 24 h oscillation), rather than phase, however, may better match performance demands of shift-workers and can be quickly and feasibly implemented in animals. In fact, a bifurcated pacemaker waveform may permit stable entrainment of a bimodal sleep/wake rhythm promoting alertness in both night and daylight hours. Although bifurcation has yet to be formally assessed in humans, evidence of conserved properties of circadian organization and plasticity predict its occurrence: humans respond to conventional manipulations of waveform (e.g., photoperiodism); behaviorally, the sleep/wake rhythm is adaptable; and finally, the human circadian system likely derives from the same multiple cellular oscillators that permit waveform flexibility in the rodent pacemaker. In short, investigation into untried manipulations of waveform in humans to facilitate adjustment to challenging schedules is justified.

The cost of poor sleep: workplace productivity loss and associated costs

OBJECTIVE

To assess the impact of sleep disturbances on work performance/productivity.

METHODS

Employees (N = 4188) at four US corporations were surveyed about sleep patterns and completed the Work Limitations Questionnaire. Respondents were classified into four categories: insomnia, insufficient sleep syndrome, at-risk, and good sleep. Employer costs related to productivity changes were estimated through the Work Limitations Questionnaire. Performance/productivity, safety, and treatment measures were compared using a one-way analysis of variance model.

RESULTS

Compared with at-risk and good-sleep groups, insomnia and insufficient sleep syndrome groups had significantly worse productivity, performance, and safety outcomes. The insomnia group had the highest rate of sleep medication use. The other groups were more likely to use nonmedication treatments. Fatigue-related productivity losses were estimated to cost $1967/employee annually.

CONCLUSIONS

Sleep disturbances contribute to decreased employee productivity at a high cost to employers.

Psychosocial Work Characteristics Predicting Daytime Sleepiness in Day and Shift Workers

Characteristics of work organization other than working time arrangements may contribute importantly to daytime sleepiness. The present study was designed to identify the psychosocial factors at work that predict daytime sleepiness in a sample of day and shift workers. Participants working at a pulp and chemical factory completed an annual questionnaire regarding psychosocial factors at work using the U.S. National Institute for Occupational Safety and Health Generic Job Stress Questionnaire (i.e., quantitative workload, variance in workload, job control, support from supervisor, coworkers, or family/friends, job satisfaction, and depressive symptoms), as well as daytime sleepiness (through the Epworth Sleepiness Scale [ESS]) and sleep disturbances for three years starting in 2002 (response rates, 94.6-99.0%). The present analysis included 55 day workers (11 women) and 57 shift workers (all men) who participated in all three years of the study, worked under the same work schedule throughout the study period, and had no missing data on any of the daytime sleep items. A repeated-measures analysis of covariance (ANCOVA) was used to test the effects of work schedule (day vs. shift work) and psychosocial factors at work in 2002 on the ESS scores in subsequent years, with sleep duration, insomnia symptoms, chronic diseases, and sleepiness levels at baseline as covariates. Given significant and near-significant interactions of work schedules with psychosocial factor or study year, the ANCOVA, with the factors of psychosocial work characteristics and study year, was performed by type of work schedule. The results indicated a significant main effect of psychosocial work characteristics (p = 0.010, partial eng2 = 0.14) and an almost significant main effect of study year (p = 0.067, partial eng2 = 0.06) and interaction between psychosocial work characteristics and study year (p = 0.085, partial eng2 = 0.06) for variance in workload among the day work group. The day workers reporting high variance in workload in 2002 exhibited significantly higher ESS scores in 2003 and 2004 than did those reporting low variance in workload. The ANCOVA for the shift work group showed a main effect of psychosocial work characteristics for job satisfaction (p = 0.026, partial eng2 = 0.10) and depressive symptoms (p = 0.094, partial eng2 = 0.06) with the interaction between psychosocial work characteristics and study year for job satisfaction (p = 0.172, partial eng2 = 0.04) and depressive symptoms (p = 0.035, partial eng2 = 0.07). The shift workers with low job satisfaction and high symptoms of depression in 2002 showed significantly greater ESS scores in 2003 and/or 2004 than did those with opposite characteristics. These results may suggest a potential predictive value of variance in workload for day workers as well as job satisfaction and depressive symptoms for shift workers with respect to daytime sleepiness. The present findings may imply that redesigning these aspects of work environment would be of help in managing daytime sleepiness.

Perspective: limiting resident work hours is a moral concern

The author outlines the cross-cultural and widespread expectation that the moral character of physicians is built on dual possession of skill and compassion. The details of the moral makeup of physicians are often hotly debated in the biomedical literature. Despite a lack of consensus regarding the required aspects of character, the author demonstrates that little debate exists that at a minimum physicians should possess not only knowledge but also a willingness to care for and comfort patients. The primacy of the patient in the physician's life is reflected in the panoply of oaths taken by new physicians despite great variability in other aspects of these oaths. The author details recent worrisome reports demonstrating the erosion of medical trainees' empathy and compassion by long work hours. Further, the continued linkage of these attitude changes and fatigue to poor medical outcomes is a call to action. Changes enacted by the Accreditation Council for Graduate Medical Education to reduce resident work hours are insufficient to achieve the goal of improved patient care while promoting moral development among resident physicians. The debate regarding resident work hours is often framed as an idealistic discussion of placing patients first. However, residents are used as an inexpensive labor force, and efforts to curtail this usage would have a significant economic impact. Economic concerns play a larger part in decision making than is generally discussed. The author calls for further alterations of resident work schedules to improve patient care and ensure the preservation of the moral ethos of medicine.

Validation of the Dutch Occupational Impact of Sleep Questionnaire (OISQ)

Sleep problems are often under-diagnosed, but may have a profound impact on work performance. The purpose of this study was to validate the Dutch version of the Occupational Impact of Sleep Questionnaire (OISQ). A total of 555 adults with a regular daytime job completed the OISQ. In addition, they also completed the Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS) and the SLEEP-50 questionnaire. 443 surveys were included in the analysis (220 men and 223 women). The Dutch OISQ had high reliability (Chronbach's alpha=0.96). OISQ scores correlated significantly with scores on the SLEEP-50 questionnaire, ESS, and PSQI (p<0.0001). Mean score on the OISQ was 14.0. Poor sleepers (OISQ score around 20) had approximately double the OISQ score as good sleepers (OISQ score around 10), irrespective of this classification was based on self-ratings, PSQI-scores or SLEEP-50 scores. The Dutch OISQ is a suitable tool to examine the occupational impact of sleep.

Diagnosis of circadian rhythm sleep disorders

Insomnia and excessive sleepiness are common in the investigation of sleep-disordered breathing. Circadian rhythm sleep disorders are perhaps the most often overlooked conditions in the differential diagnosis of these symptoms. Circadian rhythm sleep disorders manifest as misalignment between the sleep period and the physical/social 24-h environmental cycle. The two most prevalent circadian rhythm sleep disorders are delayed sleep phase (common in adolescents) and advanced sleep phase (common in the elderly), situations in which the sleep period is displaced to a later or earlier time, respectively. It is important to keep these two disorders in mind, since they can be confused with insomnia and excessive sleepiness. However, there are nine possible diagnoses, and all nine are of clinical interest. Since light is the principal cue used in synchronizing the biological clock, blind individuals and night-shift/swing-shift workers are more prone to develop circadian rhythm sleep disorders. In this article, the new international classification of circadian rhythm sleep disorders is reviewed.

Identification of SLEEPLESS, a sleep-promoting factor

Sleep is an essential process conserved from flies to humans. The importance of sleep is underscored by its tight homeostatic control. Through a forward genetic screen, we identified a gene, sleepless, required for sleep in Drosophila. The sleepless gene encodes a brain-enriched, glycosylphosphatidylinositol-anchored protein. Loss of SLEEPLESS protein caused an extreme (>80%) reduction in sleep; a moderate reduction in SLEEPLESS had minimal effects on baseline sleep but markedly reduced the amount of recovery sleep after sleep deprivation. Genetic and molecular analyses revealed that quiver, a mutation that impairs Shaker-dependent potassium current, is an allele of sleepless. Consistent with this finding, Shaker protein levels were reduced in sleepless mutants. We propose that SLEEPLESS is a signaling molecule that connects sleep drive to lowered membrane excitability.

Alertness management strategies for operational contexts

This review addresses the problem of fatigue (on-the-job-sleepiness) attributable to sleep loss in modern society and the scientifically proven strategies useful for reducing fatigue-related risks. Fatigue has become pervasive because many people work non-standard schedules, and/or they consistently fail to obtain sufficient sleep. Sleep restriction, sleep deprivation, and circadian desynchronization produce a variety of decrements in cognitive performance as well as an array of occupational and health risks. A number of real-world mishaps have resulted from performance failures associated with operator sleepiness. In some cases, fatigue/sleepiness is unavoidable, at least temporarily, due to job-related or other factors, but in other cases, fatigue/sleepiness results from poor personal choices. Furthermore, some individuals are more vulnerable to the effects of sleep loss than others. Fortunately, fatigue-related risks can be mitigated with scientifically valid alertness-management strategies. Proper work/rest scheduling and good sleep hygiene are of primary importance. If sleep time is available but sleep is difficult to obtain, sleep-inducing medications and behavioral circadian-adjustment strategies are key. In fatiguing situations such as when sleep opportunities are temporarily inadequate, limiting time on tasks, strategic napping, and the potential use of alertness-enhancing compounds must be considered. To optimize any alertness-management program, everyone must first be educated about the nature of the problem and the manner in which accepted remedies should be implemented. In the near future, objective fatigue-detection technologies may contribute substantially to the alleviation of fatigue-related risks in real-world operations.

Treatment of narcolepsy and other hypersomnias of central origin

OBJECTIVE

The purpose of this paper is to summarize current knowledge about treatment of narcolepsy and other hypersomnias of central origin.

METHODS

The task force performed a systematic and comprehensive review of the relevant literature and graded the evidence using the Oxford grading system. This paper discusses the strengths and limitations of the available evidence regarding treatment of these conditions, and summarizes key information about safety of these medications. Our findings provide the foundation for development of evidence-based practice parameters on this topic by the Standards of Practice Committee of the American Academy of Sleep Medicine.

RESULTS

The majority of recent papers in this field provide information about use of modafinil or sodium oxybate for treatment of sleepiness associated with narcolepsy. Several large randomized, placebo-controlled studies indicate that modafinil and sodium oxybate are effective for treatment of hypersomnia due to narcolepsy. We identified no studies that report direct comparison of these newer medications versus traditional stimulants, or that indicate what proportion of patients treated initially with these medications require transition to traditional stimulants or to combination therapy to achieve adequate alertness. As with the traditional stimulants, modafinil and sodium oxybate provide, at best, only moderate improvement in alertness rather than full restoration of alertness in patients with narcolepsy. Several large randomized placebo-controlled studies demonstrate that sodium oxybate is effective for treatment of cataplexy associated with narcolepsy, and earlier studies provide limited data to support the effectiveness of fluoxetine and tricyclic antidepressants for treatment of cataplexy. Our findings indicate that very few reports provide information regarding treatment of special populations such as children, older adults, and pregnant or breastfeeding women. The available literature provides a modest amount of information about improvement in quality of life in association with treatment, patient preferences among the different medications, or patient compliance.

CONCLUSION

Several recent studies provide evidence that modafinil and sodium oxybate are effective for treatment of hypersomnia due to narcolepsy. No studies were identified that report direct comparison of these newer medications with traditional stimulants. Despite significant advances in understanding the pathophysiology of narcolepsy, we do not have an ideal treatment to restore full and sustained alertness. Future investigations should be directed toward development of more effective and better tolerated therapies, and primary prevention.

Optimization of biomathematical model predictions for cognitive performance impairment in individuals: accounting for unknown traits and uncertain states in homeostatic and circadian processes

Current biomathematical models of fatigue and performance do not accurately predict cognitive performance for individuals with a priori unknown degrees of trait vulnerability to sleep loss, do not predict performance reliably when initial conditions are uncertain, and do not yield statistically valid estimates of prediction accuracy. These limitations diminish their usefulness for predicting the performance of individuals in operational environments. To overcome these 3 limitations, a novel modeling approach was developed, based on the expansion of a statistical technique called Bayesian forecasting. The expanded Bayesian forecasting procedure was implemented in the two-process model of sleep regulation, which has been used to predict performance on the basis of the combination of a sleep homeostatic process and a circadian process. Employing the two-process model with the Bayesian forecasting procedure to predict performance for individual subjects in the face of unknown traits and uncertain states entailed subject-specific optimization of 3 trait parameters (homeostatic build-up rate, circadian amplitude, and basal performance level) and 2 initial state parameters (initial homeostatic state and circadian phase angle). Prior information about the distribution of the trait parameters in the population at large was extracted from psychomotor vigilance test (PVT) performance measurements in 10 subjects who had participated in a laboratory experiment with 88 h of total sleep deprivation. The PVT performance data of 3 additional subjects in this experiment were set aside beforehand for use in prospective computer simulations. The simulations involved updating the subject-specific model parameters every time the next performance measurement became available, and then predicting performance 24 h ahead. Comparison of the predictions to the subjects' actual data revealed that as more data became available for the individuals at hand, the performance predictions became increasingly more accurate and had progressively smaller 95% confidence intervals, as the model parameters converged efficiently to those that best characterized each individual. Even when more challenging simulations were run (mimicking a change in the initial homeostatic state; simulating the data to be sparse), the predictions were still considerably more accurate than would have been achieved by the two-process model alone. Although the work described here is still limited to periods of consolidated wakefulness with stable circadian rhythms, the results obtained thus far indicate that the Bayesian forecasting procedure can successfully overcome some of the major outstanding challenges for biomathematical prediction of cognitive performance in operational settings.

Is sleep really for sissies? Understanding the role of work in insomnia in the US

This study explores the role of work in patient narratives about their experiences with insomnia. "Work" includes such facets as the nature of one's occupation, the associated volume or amount of work required, mental demands related to work, work schedules and work-related stress. Interviews conducted with 24 patients aged between 22 and 74 receiving treatment for insomnia at one of two sleep medicine clinics in Oregon and Texas, USA, suggest that work is a pivotal influence in shaping interpretations of the nature of insomnia, its causes, and the efficacy of medical treatment. Results suggest correlations between sleeplessness and modern working lifestyles in American culture, in which labor seems to transcend the physical workplace, manifesting itself in the form of cognitive labor or continued problems into retirement. Patients often cite work as the primary causal agent in the development of their insomnia, their primary reason for needing "good" sleep, their impetus for seeking medical attention, and behavioral compliance with a medically prescribed regimen. Insomnia as an illness experience thus serves as a mechanism through which respondents consciously or unconsciously comment on the nature of work in their lives. The medical and social implications of these results are discussed.

Sleep deprivation reduces perceived emotional intelligence and constructive thinking skills

BACKGROUND AND PURPOSE

Insufficient sleep can adversely affect a variety of cognitive abilities, ranging from simple alertness to higher-order executive functions. Although the effects of sleep loss on mood and cognition are well documented, there have been no controlled studies examining its effects on perceived emotional intelligence (EQ) and constructive thinking, abilities that require the integration of affect and cognition and are central to adaptive functioning.

PATIENTS AND METHODS

Twenty-six healthy volunteers completed the Bar-On Emotional Quotient Inventory (EQi) and the Constructive Thinking Inventory (CTI) at rested baseline and again after 55.5 and 58 h of continuous wakefulness, respectively.

RESULTS

Relative to baseline, sleep deprivation was associated with lower scores on Total EQ (decreased global emotional intelligence), Intrapersonal functioning (reduced self-regard, assertiveness, sense of independence, and self-actualization), Interpersonal functioning (reduced empathy toward others and quality of interpersonal relationships), Stress Management skills (reduced impulse control and difficulty with delay of gratification), and Behavioral Coping (reduced positive thinking and action orientation). Esoteric Thinking (greater reliance on formal superstitions and magical thinking processes) was increased.

CONCLUSIONS

These findings are consistent with the neurobehavioral model suggesting that sleep loss produces temporary changes in cerebral metabolism, cognition, emotion, and behavior consistent with mild prefrontal lobe dysfunction.

Rapid phase adjustment of melatonin and core body temperature rhythms following a 6-h advance of the light/dark cycle in the horse

Background

Rapid displacement across multiple time zones results in a conflict between the new cycle of light and dark and the previously entrained program of the internal circadian clock, a phenomenon known as jet lag. In humans, jet lag is often characterized by malaise, appetite loss, fatigue, disturbed sleep and performance deficit, the consequences of which are of particular concern to athletes hoping to perform optimally at an international destination. As a species renowned for its capacity for athletic performance, the consequences of jet lag are also relevant for the horse. However, the duration and severity of jet lag related circadian disruption is presently unknown in this species. We investigated the rates of re-entrainment of serum melatonin and core body temperature (BT) rhythms following an abrupt 6-h phase advance of the LD cycle in the horse.

Methods

Six healthy, 2 yr old mares entrained to a 12 h light/12 h dark (LD 12:12) natural photoperiod were housed in a light-proofed barn under a lighting schedule that mimicked the external LD cycle. Following baseline sampling on Day 0, an advance shift of the LD cycle was accomplished by ending the subsequent dark period 6 h early. Blood sampling for serum melatonin analysis and BT readings were taken at 3-h intervals for 24 h on alternate days for 11 days. Disturbances to the subsequent melatonin and BT 24-h rhythms were assessed using repeated measures ANOVA and analysis of Cosine curve fitting parameters.

Results

We demonstrate that the equine melatonin rhythm re-entrains rapidly to a 6-h phase advance of an LD12:12 photocycle. The phase shift in melatonin was fully complete on the first day of the new schedule and rhythm phase and waveform were stable thereafter. In comparison, the advance in the BT rhythm was achieved by the third day, however BT rhythm waveform, especially its mesor, was altered for many days following the LD shift.

Conclusion

Aside from the temperature rhythm disruption, rapid resynchronization of the melatonin rhythm suggests that the central circadian pacemaker of the horse may possess a particularly robust entrainment response. The consequences for athletic performance remain unknown.

Identification of a biomarker for sleep drive in flies and humans

It is a common experience to sacrifice sleep to meet the demands of our 24-h society. Current estimates reveal that as a society, we sleep on average 2 h less than we did 40 years ago. This level of sleep restriction results in negative health outcomes and is sufficient to produce cognitive deficits and reduced attention and is associated with increased risk for traffic and occupational accidents. Unfortunately, there is no simple quantifiable marker that can detect an individual who is excessively sleepy before adverse outcomes become evident. To address this issue, we have developed a simple and effective strategy for identifying biomarkers of sleepiness by using genetic and pharmacological tools that dissociate sleep drive from wake time in the model organism Drosophila melanogaster. These studies have identified a biomarker, Amylase, that is highly correlated with sleep drive. More importantly, both salivary Amylase activity and mRNA levels are also responsive to extended waking in humans. These data indicate that the fly is relevant for human sleep research and represents a first step in developing an effective method for detecting sleepiness in vulnerable populations.

Sleep and cognitive performance of flight nurses after 12-hour evening versus 18-hour shifts

BACKGROUND

Inadequate rest can result in disastrous medical and aviation errors. Using a prospective within-subjects design, this study compared the amount of daily sleep and the cognitive performance in flight nurses working 12-hour evening versus 18-hour shifts during a 72-hour duty schedule.

METHODS

Ten flight nurses who worked two different duty schedules participated in the study. The first duty schedule consisted of three back-to-back 12-hour (7:00 pm to 7:00 am) evening shifts. The second duty schedule consisted of two 18-hour (7:00 am to 1:00 am) shifts separated by a 24-hour rest period. Pre- and duty sleep times were monitored using actigraphy. The flight nurses were tested using a battery of neuropsychological tests before and immediately after completing 12- and 18-hour duty schedules. After the conclusion of both duty schedules, nurses were asked to rate the 12- versus 18-hour duty schedules via questionnaire.

RESULTS

Daily sleep times for the 12- versus 18-hour were not different for the pre-duty schedule (8.9 +/- 2.3 vs. 9.0 +/- 2.3 hours) or during duty schedule (7.0 +/- 1.4 vs. 6.9 +/- 1.3 hours). A significant decline was seen in the amount of pre- versus duty sleep for both the 12-hour (8.9 +/- 2.3 vs. 7.0 +/- 1.4 hours; P < .05) and the 18-hour (9.0 +/- 2.3 vs. 6.9 +/- 1.3 hours; P = .04) duty schedules. During the 72-hour duty schedule, the 12-hour vs. 18-hour duty schedules, the nurses had less pre-shift sleep (3.2 +/- 1.2 vs. 6.2 +/- 0.6; P = .001) and more on-shift (4.4 +/- 1.7 vs. 2.1 +/- 0.8; P = .002) sleep. Despite the decline in daily sleep during both duty schedules, no significant decline in the before versus after cognitive test scores were observed for either the 12- or 18-hour duty schedule. A questionnaire given to the 10 nurses indicated that the 18-hour duty schedule was more compatible with their non-work lifestyle (P = .04).

CONCLUSIONS

Provided adequate daily sleep (at least 7 hours/day) is obtained, we found no difference or decline in the cognitive function of flight nurses working either a 12-hour evening or 18-hour shift during a 72-hour duty schedule. Eighteen-hour duty shifts may be a practical economical means of expanding the period of helicopter site coverage without adversely affecting cognitive performance in medical crewmembers. Actigraphy may be a useful tool for air medical programs that want to objectively assess whether adequate sleep is occurring in individuals working extended (>12 hours) or unusual duty shifts.