Differential effects of modafinil on performance of low-performing and high-performing individuals during total sleep deprivation.

BACKGROUND: Individual responses to the effects of inadequate sleep have been well documented; some people are more vulnerable to the effects of sleep loss than others. Fatigue-vulnerable individuals generally require access to effective fatigue countermeasures; however, the question arises as to whether these fatigue-vulnerable individuals receive the same benefits shown in group efficacy data. The present study administered modafinil to individuals to determine its differential effects on performance of best and worst performers during sleep deprivation. METHODS: A sample of 22 men, age 21-40 yrs., was tested on 2 separate occasions during which they were kept awake for 36 h. During one period they received 200 mg modafinil; during the other they received placebo. Participants were tested on a variety of tasks while rested and at 5-hr intervals across the continuous wakefulness period. Performance for each cognitive task and subjective measure of fatigue from the placebo period was used to group individuals into high (HP) or low performance (LP) groups to indicate fatigue vulnerability for each task. RESULTS: Results indicated that on the MTS task, the HP group performed the same throughout the testing period, regardless of whether they received modafinil or not. However, the LP group significantly improved after receiving modafinil compared to placebo. Performance on the PVT showed the HP group had a small decrease in the number of lapses after receiving modafinil compared to placebo, whereas the LP group had a large decrease in lapses after receiving modafinil compared to placebo. Performance on the RDM showed no difference between groups, regardless of drug condition. Groups did not differ after receiving modafinil on subjective fatigue measured by the POMS. CONCLUSIONS: Depending on the task, HP individuals did not benefit substantially when administered modafinil compared to placebo. However, the LP individuals improved after receiving modafinil compared to placebo.

Fatigue and its management in the workplace.

Fatigue and workplace sleepiness are consequences of modern industrial society. Fatigue is a complex biological phenomenon that occurs as a function of time awake, time-of-day, workload, health, and off-duty lifestyle. Fatigue is a function of two major biological factors - the homeostatic drive for sleep and circadian rhythm of sleepiness. The greatest cause of fatigue is insufficient or disrupted sleep. Excessive sleepiness in the workplace and on highways is a serious safety hazard, and insufficient or disrupted sleep results in numerous accidents and adverse mental and physical health outcomes. Evidence-based strategies that promote better sleep and optimize work/rest schedules can mitigate the impact of fatigue and sleep loss. Proper nap and sleep scheduling, work breaks, modeling and monitoring tools, fatigue detection technologies, and pharmacological countermeasures can be implemented at home and/or in the workplace to reduce performance and safety hazards. Education about obtaining adequate sleep, the dangers of fatigue in terms of both health and cognitive consequences, and the availability of scientifically-proven sleep-enhancement and alertness-management strategies is essential.

Fatiguing effect of multiple take-offs and landings in regional airline operations.

Fatigue is a risk factor for flight performance and safety in commercial aviation. In US commercial aviation, to help to curb fatigue, the maximum duration of flight duty periods is regulated based on the scheduled start time and the number of flight segments to be flown. There is scientific support for regulating maximum duty duration based on scheduled start time; fatigue is well established to be modulated by circadian rhythms. However, it has not been established scientifically whether the number of flight segments, per se, affects fatigue. To address this science gap, we conducted a randomized, counterbalanced, cross-over study with 24 active-duty regional airline pilots. Objective and subjective fatigue was compared between a 9-hour duty day with multiple take-offs and landings versus a duty day of equal duration with a single take-off and landing. To standardize experimental conditions and isolate the fatiguing effect of the number of segments flown, the entire duty schedules were carried out in a high-fidelity, moving-base, full-flight, regional jet flight simulator. Steps were taken to maintain operational realism, including simulated airplane inspections and acceptance checks, use of realistic dispatch releases and airport charts, real-world air traffic control interactions, etc. During each of the two duty days, 10 fatigue test bouts were administered, which included a 10-minute Psychomotor Vigilance Test (PVT) assessment of objective fatigue and Samn-Perelli (SP) and Karolinska Sleepiness Scale (KSS) assessments of subjective sleepiness/fatigue. Results showed a greater build-up of objective and subjective fatigue in the multi-segment duty day than in the single-segment duty day. With duty start time and duration and other variables that could impact fatigue levels held constant, the greater build-up of fatigue in the multi-segment duty day was attributable specifically to the difference in the number of flight segments flown. Compared to findings in previously published laboratory studies of simulated night shifts and nighttime sleep deprivation, the magnitude of the fatiguing effect of the multiple take-offs and landings was modest. Ratings of flight performance were not significantly reduced for the simulated multi-segment duty day. The US duty and flight time regulations for commercial aviation shorten the maximum duty duration in multi-segment operations by up to 25% depending on the duty start time. The present results represent an important first step in understanding fatigue in multi-segment operations, and provide support for the number of flight segments as a relevant factor in regulating maximum duty duration. Nonetheless, based on our fatigue results, a more moderate reduction in maximum duty duration as a function of the number of flight segments might be considered. However, further research is needed to include investigation of flight safety, and to extend our findings to nighttime operations.

Screening for Sleep Apnea in Morbidly Obese Pilots.

BACKGROUND: Debate regarding the merits of screening pilots for sleep apnea has been stimulated by recently issued guidance from the Federal Aviation Administration. It has long been appreciated that sleep apnea results in poor quality sleep, and that poor quality sleep is associated with daytime fatigue and decrements in performance. However, the relationship between sleep apnea and poor performance, including risk for accidents is not as well understood. Good quality data are available for commercial truck drivers and have helped influence transportation policy, but there is a lack of pilot specific data. The purpose of this article is to review the basic epidemiology, pathophysiology, and treatment of sleep apnea, including major risk factors for apnea, such as body mass index (BMI), and to look at what is known about the impact of sleep apnea on performance in transportation related occupations. While pilot specific data may be lacking, good quality data for commercial truckers are available and can be used to formulate rational public policy with the goal of improving aviation safety. This article was reviewed by the Council of the Aerospace Medical Association and approved as a position paper of the Association.

Improving multi-tasking ability through action videogames.

The present study examined whether action videogames can improve multi-tasking in high workload environments. Two groups with no action videogame experience were pre-tested using the Multi-Attribute Task Battery (MATB). It consists of two primary tasks; tracking and fuel management, and two secondary tasks; systems monitoring and communication. One group served as a control group, while a second played action videogames a minimum of 5 h a week for 10 weeks. Both groups returned for a post-assessment on the MATB. We found the videogame treatment enhanced performance on secondary tasks, without interfering with the primary tasks. Our results demonstrate action videogames can increase people's ability to take on additional tasks by increasing attentional capacity.

Individual differences in cognitive vulnerability to fatigue in the laboratory and in the workplace.

Individual differences in cognitive functioning during extended work hours and shift work are of considerable magnitude, and observed both in the laboratory and in the workplace. These individual differences have a biological basis in trait-like, differential vulnerability to fatigue from sleep loss and circadian misalignment. Trait-like vulnerability is predicted in part by gene polymorphisms and other biological or psychological characteristics, but for the larger part it remains unexplained. A complicating factor is that whether individuals are vulnerable or resilient to sleep deprivation depends on the fatigue measure considered--subjective versus objective assessment, or one cognitive task versus another. Such dissociation has been observed in laboratory data published previously, and in data from a simulated operational setting first presented here. Discordance between subjective and objective measures of fatigue has been documented in various contexts, and may be one of the reasons why vulnerable individuals do not systematically opt out of professions involving high cognitive demands and exposure to fatigue. Discordance in vulnerability to fatigue among different measures of cognitive performance may be related to the "task impurity problem," which implies that interrelated cognitive processes involved in task performance must be distinguished before overall performance outcomes can be fully understood. Experimental studies and cognitive and computational modeling approaches are currently being employed to address the task impurity problem and gain new insights into individual vulnerability to fatigue across a wide range of cognitive tasks. This ongoing research is driving progress in the management of risks to safety and productivity associated with vulnerability to cognitive impairment from fatigue in the workplace.

Fatigue countermeasures in aviation.

Pilot fatigue is a significant problem in modern aviation operations, largely because of the unpredictable work hours, long duty periods, circadian disruptions, and insufficient sleep that are commonplace in both civilian and military flight operations. The full impact of fatigue is often underappreciated, but many of its deleterious effects have long been known. Compared to people who are well-rested, people who are sleep deprived think and move more slowly, make more mistakes, and have memory difficulties. These negative effects may and do lead to aviation errors and accidents. In the 1930s, flight time limitations, suggested layover durations, and aircrew sleep recommendations were developed in an attempt to mitigate aircrew fatigue. Unfortunately, there have been few changes to aircrew scheduling provisions and flight time limitations since the time they were first introduced, despite evidence that updates are needed. Although the scientific understanding of fatigue, sleep, shift work, and circadian physiology has advanced significantly over the past several decades, current regulations and industry practices have in large part failed to adequately incorporate the new knowledge. Thus, the problem of pilot fatigue has steadily increased along with fatigue-related concerns over air safety. Accident statistics, reports from pilots themselves, and operational flight studies all show that fatigue is a growing concern within aviation operations. This position paper reviews the relevant scientific literature, summarizes applicable U.S. civilian and military flight regulations, evaluates various in-flight and pre-/postflight fatigue countermeasures, and describes emerging technologies for detecting and countering fatigue. Following the discussion of each major issue, position statements address ways to deal with fatigue in specific contexts with the goal of using current scientific knowledge to update policy and provide tools and techniques for improving air safety.

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.

Considerations of pharmacology on fitness for duty in the operational environment.

Coordination of strategies for transitioning psychoactive pharmacological compounds from basic laboratory research to the field environment has been an ongoing effort among military laboratories. Several workshops have been held specifically to address the operationally relevant issues and other military and scientific challenges as they relate to the enhancement and sustainability of cognitive performance. In this preface, we tie together recommendations of the Pharmacological Strategies Focus Team for one such Workshop, review current literature, and discuss findings reported at recent professional meetings. The papers presented within this pharmacology section are discussed. These section papers are organized into three areas of operational relevance--the first assesses the effectiveness of a treatment given for migraines, a condition with known detrimental effects on productivity and readiness; the second discusses ethical considerations surrounding the use of pharmaceutical countermeasures for fatigue in the operational environment; and the third discusses a case report highlighting the aeromedical considerations regarding selective serotonin reuptake inhibitors (SSRIs) and aviator flight performance, particularly as assessed with neuropsychological testing. The papers and commentaries in this section encourage us to consider the complex variables effecting the decisions to administer pharmacological agents, as the impact of their use is weighed against the cognitive performance effects they may have in the operational environment.

Investigating systematic individual differences in sleep-deprived performance on a high-fidelity flight simulator.

Laboratory research has revealed considerable systematic variability in the degree to which individuals' alertness and performance are affected by sleep deprivation. However, little is known about whether or not different populations exhibit similar levels of individual variability. In the present study, we examined individual variability in performance impairment due to sleep loss in a highly select population of militaryjet pilots. Ten active-duty F-117 pilots were deprived of sleep for 38 h and studied repeatedly in a high-fidelity flight simulator. Data were analyzed with a mixed-model ANOVA to quantify individual variability. Statistically significant, systematic individual differences in the effects of sleep deprivation were observed, even when baseline differences were accounted for. The findings suggest that highly select populations may exhibit individual differences in vulnerability to performance impairment from sleep loss just as the general population does. Thus, the scientific and operational communities' reliance on group data as opposed to individual data may entail substantial misestimation of the impact of job-related stressors on safety and performance.

Fatigue in military aviation: an overview of US military-approved pharmacological countermeasures.

Uncomfortable working and sleeping environments, high operational tempos, sustained operations, and insufficient staffing make fatigue a growing concern. In aviation, where a single mistake can cost millions of dollars, it is essential to optimize operator alertness. Although behavioral and administrative fatigue countermeasures should comprise the "first line" approach for sustaining aircrew performance, pharmacological fatigue countermeasures are often required. Various components of the U.S. military have authorized the use of specific compounds for this purpose. Hypnotics such as temazepam, zolpidem, or zaleplon can mitigate the fatigue associated with insufficient or disturbed sleep. Alertness-enhancing compounds such as caffeine, modafinil, or dextroamphetamine can temporarily bridge the gap between widely spaced sleep periods. Each of these medications has a role in sustaining the safety and effectiveness of military aircrews. The present paper provides a short overview of these compounds as well as factors to be considered before choosing one or more to help manage fatigue.

Are individual differences in fatigue vulnerability related to baseline differences in cortical activation?

Recent evidence suggests that underlying patterns of cortical activation may partially account for individual differences in susceptibility to the effects of sleep deprivation. Here, functional magnetic resonance imaging (fMRI) was used to examine the activation of military pilots whose sleep-deprivation vulnerability previously was quantified. A Sternberg Working Memory Task (SWMT; S. Sternberg, 1966) was completed alternately with a control task during a 13-min blood oxygen level-dependent fMRI scan. Examination of the activated voxels in response to SWMT indicated that, as a group, the pilots were more similar to fatigue-resistant nonpilots than to fatigue-vulnerable nonpilots. Within the pilots, cortical activation was significantly related to fatigue vulnerability on simulator-flight performance. These preliminary data suggest that baseline fMRI scan activation during a working memory task may correlate with fatigue susceptibility.

Modafinil's effects on simulator performance and mood in pilots during 37 h without sleep.

INTRODUCTION: Modafinil is a relatively new alertness-enhancing compound of interest to the military aviation community. Although modafinil has been well-tested in clinical settings, additional studies are required to establish its safety and efficacy for use in pilots. OBJECTIVE: The purpose of this study was to determine whether modafinil (100 mg after 17, 22, and 27 h without sleep) would attenuate the effects of fatigue on fighter-pilot mood and performance during 37 h of continuous wakefulness. METHODS: A quasi-experimental, single-blind, counterbalanced design tested the effects of modafinil in 10 Air Force F-117 pilots. RESULTS: Modafinil attenuated flight performance decrements on six of eight simulator maneuvers. Overall, modafinil maintained flight accuracy within approximately 15-30% of baseline levels, whereas performance under the no-treatment/placebo condition declined by as much as 60-100%. Modafinil decreased self-ratings of depression and anger, while improving ratings of vigor, alertness, and confidence. Benefits were most noticeable after 24 to 32 h of continuous wakefulness. One potential drawback of modafinil was that, at least at the 100-mg dose level, the drug's effects were not subjectively salient. Since this may lead personnel to escalate the dose without flight surgeon approval, personnel should be cautioned regarding this particular drug characteristic. CONCLUSION: Although modafinil did not sustain performance at predeprivation levels, the present study suggests that modafinil should be considered for the military's armament of short-term fatigue countermeasures. Future research will evaluate whether 200-mg doses are more beneficial than the 100-mg doses used here.

Utility of dextroamphetamine for attenuating the impact of sleep deprivation in pilots.

INTRODUCTION: Dextroamphetamine (Dexedrine) is an effective fatigue countermeasure for use in military subject pilots who are deprived of sleep. Anecdotal reports have indicated Dexedrine (Dex) is effective in "real world" sustained operations, and controlled laboratory tests have yielded positive results as well. The aim of this study was to substantiate the efficacy of Dex for sustaining the alertness and performance of pilots during periods of sleep deprivation by showing the robust effects of the medication and its consistent effects across several research efforts. METHODS: In the present report, selected data from several controlled aviation studies were reviewed and combined to corroborate the efficacy of Dex as a fatigue countermeasure. RESULTS: The results showed Dex to be effective for maintaining flight skills, psychological mood, and physiological activation (measured via electroencephalograph data) in sleep-deprived pilots. The positive benefits of the medication were not offset by marked disruptions in recovery sleep, although some negative effects were observed (sleep was lighter for several hours following drug administration). CONCLUSIONS: Dex is a viable remedy for fatigue in aviation sustained operations. However, Dex is not a substitute for proper crew-rest scheduling because there is no replacement for adequate restful sleep.

Improving daytime sleep with temazepam as a countermeasure for shift lag.

BACKGROUND: Working night shift (reverse cycle) presents problems to personnel due to the difficulty in maintaining alertness during the nighttime hours. When the shift must be worked several consecutive nights, a cumulative sleep debt is created. Appropriate countermeasures are required to help personnel obtain as much sleep as possible so they may perform their duties effectively. HYPOTHESIS: The objectives were to determine whether a hypnotic taken before daytime sleep would improve sleep quality, and to determine whether improved daytime sleep would increase alertness, reduce fatigue, and mitigate the usual performance decrements which occur on night shift. METHODS: Sixteen UH-60 Army aviators were randomly assigned to either a temazepam or a placebo group. Test sessions, consisting of vigilance assessments, flight simulation, and mood state questionnaires were administered during baseline, three nights of reverse cycle, and three days following a return to day shift. Temazepam (30 mg) was administered before daytime sleep to one group while another group received a lactose-filled capsule. RESULTS: Subjects who received temazepam slept longer and with less fragmentation than those who received placebo. Generally, the subjects in the temazepam group indicated more subjective alertness and less fatigue than those in the placebo group. Flight performance was not unequivocally improved by better daytime sleep, but the temazepam group performed better on the Psychomotor Vigilance Task than the placebo group. CONCLUSIONS: Temazepam is helpful in prolonging daytime sleep, with some attenuation of performance decrements during the night shift. However, physicians should be careful when administering this substance to ensure the aviator has a minimum of 8 h in which to sleep.

Body posture affects electroencephalographic activity and psychomotor vigilance task performance in sleep-deprived subjects.

OBJECTIVE: This study examined the effects of posture on electroencephalographic (EEG) activity and psychomotor vigilance task (PVT) performance in 16 sleep-deprived volunteers. METHODS: EEG data were collected while participants completed 10 min PVTs under two counterbalanced sitting/standing conditions during 28 h of continuous wakefulness. RESULTS: In both the sitting and standing conditions, theta activity progressively increased as a function of sleep loss, but standing upright significantly attenuated this effect, suggesting that alertness was improved by the more upright posture. The PVT results showed that cognitive psychomotor performance was maintained at nearly well-rested levels by standing upright, whereas reaction time and attention noticeably deteriorated when participants were seated. CONCLUSIONS: These results suggest that an upright posture increases EEG arousal and sustained attention, indicating that postural manipulations can be useful for counteracting fatigue in sleep-deprived individuals.