Papers by Nita Lewis Shattuck
Elsevier eBooks, 2023
ABSTRACT Military operations span a wide spectrum ranging from basic military training and educat... more ABSTRACT Military operations span a wide spectrum ranging from basic military training and education, through military operations other than war (MOOTW), to war itself. By their very nature, military operations are conducted under tremendously stressful conditions. Individuals in military settings are under pressure to continue to conduct operations when quality sleep may be a rare commodity — and sometimes , they are asked to perform without any sleep at all. Th eir duties expose them to life-and-death situations in environmentally hostile conditions that may even include facing enemy combatants. While the impact of fatigue is not restricted to the military, the combined eff ects of a multitude of acute and chronic stressors — including severe sleep restriction — make the military population both unique and relevant to study when exploring the range and limits of human performance. An Overview of Sleep Th is fi rst section of the chapter provides the rationale and scientifi c justifi cation for the entirety of the program of research that follows. It begins with a discussion of circadian rhythms and the requirement for sleep in humans. It then provides a short tutorial on sleep architecture that describes the function and purpose of various stages of sleep. Th is introductory sleep overview concludes with a summary of the eff ects of restricted sleep on various kinds of human performance.
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS.
Aerospace medicine and human performance, Oct 1, 2015
Environmental motion can aff ect shipboard sleep of crewmembers. Slamming and similar harsh motio... more Environmental motion can aff ect shipboard sleep of crewmembers. Slamming and similar harsh motion may interfere with sleep, whereas mild motion and sopite syndrome may enhance sleep. If sleep needs vary by sea condition, this factor should be considered when assessing human performance at sea. The goal of this study was to assess sleep duration in diff erent sea conditions. METHODS: Crewmembers ( N 5 52) from a U.S. Navy vessel participated in the study while performing their normal daily schedule of duties. Sleep was assessed with wrist-worn actigraphy. Motion sickness and sopite syndrome were assessed using standardized questionnaires. In rough sea conditions, crewmembers experienced increased severity of motion sickness and sopite syndrome compared to their ratings during calmer sea conditions. Crewmembers slept signifi cantly longer during sea state 5-6 compared to sleep on days with sea state 4 (25% increase) and sea state 3-4 (30% increase). Specifi cally, daily sleep increased from 6.97 6 1.24 h in sea state 3-4, to 7.23 6 1.65 h in sea state 4, to 9.04 6 2.90 h in sea state 5 -6 . DISCUSSION: Although the duration of sleep in rough seas increased signifi cantly compared to calmer sea conditions, causal factors are inconclusive. Accumulated sleep debt, motion-induced fatigue, and sopite syndrome all may have contributed, but results suggest that motion sickness and sopite syndrome were the predominant stressors. If sleep needs increase in severe motion environments, this factor should be taken into account when developing daily activity schedules or when modeling manning requirements on modern ships.
Nutrition and Health, Oct 27, 2020
Background: Due to their long workdays and erratic watch schedules, sailors on United States Navy... more Background: Due to their long workdays and erratic watch schedules, sailors on United States Navy (USN) ships often eat meals close to their bedtime, which may contribute to sleep disruption. Aim: To assess the duration of meal-to-sleep (M-S) intervals in relation to timing of sailor workdays and watch schedules. Methods: Longitudinal field assessment of USN sailors performing their underway duties (N ¼ 234). Participants completed questionnaires, wore actigraphs, and completed activity logs. Results: Approximately 35% of M-S intervals were <3 h in duration. M-S interval duration was associated with watchstanding status (p < 0.001) and the number of sections in the watchstanding schedule (p < 0.001). Sailors on the two-section watch schedule had, on average, the shortest M-S intervals (55 min) compared to sailors on three-or four-section watchbills (*4 h) and to non-watchstanders (4.85 h). Conclusion: Sailors on two-section watchbills often eat quite close to bedtime. To provide appropriate recommendations regarding healthy dietary patterns, we will continue assessing dietary behaviors and food choices of sailors while underway, especially as they relate to sailor work hours, circadian rhythms, and sleep practices.
Sleep and Biological Rhythms, Dec 24, 2015
The case of a 29-year-old active duty US Navy sailor with severe sleepiness is presented. He was ... more The case of a 29-year-old active duty US Navy sailor with severe sleepiness is presented. He was diagnosed with mild obstructive sleep apnea which did not fully explain his sleepiness. At follow-up, positive airway pressure usage demonstrated a progressive, variable phase delay. His sleep periods aligned with his 5-h on/10-h off (5/ 10) military duty schedule. Treatment with bright light exposure and melatonin resolved his circadian arrhythmia. While it is known that military personnel are habitual shift workers who receive insufficient sleep, there is little documentation of shift work disorders in this population.
Proceedings of the Human Factors and Ergonomics Society ... Annual Meeting, Sep 1, 2018
The study assesses the agreement between the 3-minute version of the Psychomotor Vigilance Task (... more The study assesses the agreement between the 3-minute version of the Psychomotor Vigilance Task (PVT) with an interstimulus interval (ISI) of 2 to 10 seconds and the validated 3-minute laptop-based PVT (ISI=1-4 seconds). The experiment utilized a randomized, within-subject, repeated-measures design with three factors (PVT device type, the backlight feature of the wrist-worn device, ambient lighting). Results show the differences in reaction times (RT) between devices are incrementally associated with the magnitude of the RTs. These differences tend to be in opposing directions when the backlight feature in the wrist-worn device is on. That is, RTs in the wrist-worn device tend to be faster compared to the laptop for (on average) faster individuals, whereas (on average) slower individuals tend to do better in the laptop compared to the wrist-worn device. The proportional bias introduced by the wrist-worn device compared to the laptop makes it difficult to translate individual RTs between different devices. The proportional bias, however, may work in favor for detecting differences between slow and fast RTs.
Chronobiology International, Aug 26, 2020
It is often assumed the quality of life of dayworkers is better than that of shiftworkers. Our fi... more It is often assumed the quality of life of dayworkers is better than that of shiftworkers. Our findings from United States Navy (USN) sailors (N = 804, 78.4% males) showed dayworkers slept better, were less sleepy, and reported greater vigor and reduced fatigue (Profile of Mood States) than shiftworkers. Nevertheless, ~25% of dayworkers slept <6.5 h/d, ~62% had split sleep, 31% reported excessive daytime sleepiness (EDS), and ~64% were poor sleepers (Pittsburgh Sleep Quality Index). The two groups had similar sleep-related behaviors, rates of insomnia, comorbid EDS/ insomnia, and scores on total mood disturbance, tension/anxiety, depression, anger/hostility, and confusion/bewilderment. The findings of our study indicate shipboard sleep-related issues are prevalent among USN sailors.
CRC Press eBooks, Jul 7, 2023
Proceedings of the Human Factors and Ergonomics Society ... Annual Meeting, Dec 1, 2020
We assessed the utility of the 3-section, fixed, 4hrs-on/8hrs-off watchstanding schedule on a shi... more We assessed the utility of the 3-section, fixed, 4hrs-on/8hrs-off watchstanding schedule on a ship of the Swedish Royal Navy (HSwMS ORIOΝ). Data from the ORIOΝ (n=12 sailors) were compared with data from three USN vessels (n=22). Daily sleep duration, number of sleep episodes/day, and daily work duration were equivalent in the two samples. Compared to their USN peers, however, sailors on the ORION were more alert, reported better sleep quality, less severe insomnia symptoms, and better mood. Also, sailors on the ORION were faster and made fewer errors on the psychomotor vigilance task (PVT). Analysis of daily activities suggests that Swedish sailors may have felt and performed better because sailors working night shifts were allowed to wake up later. Our findings suggest the sailor well-being when standing watch on the fixed 4/8 can be improved when sailors are allowed flexible wake up times in the morning after a night shift.
Proceedings of the Human Factors and Ergonomics Society ... Annual Meeting, Nov 1, 2019
We assessed the utility of a fixed, 3-section, watchstanding schedule in a small surface combatan... more We assessed the utility of a fixed, 3-section, watchstanding schedule in a small surface combatant of the United States Navy. Sailors on the "5 hrs-daytime/3 hrs-nighttime" or "D5/N3" schedule stood two watches every day, one a 5-hour daytime shift and one a 3-hour nighttime shift. Crewmembers (N = 27) completed a questionnaire while the ship was underway to assess the utility and the crew's acceptance of the D5/N3. Crewmembers reported sleeping 5.6 ± 1.3 hours daily. The average PSQI Global score was 8.3 ± 3.5, with ~81% of the participants identified as "poor sleepers." Approximately 94% of the respondents noted that the D5/N3 was either better (53%) or the same (41%) compared to their previous watch schedule. The predictability of the daily schedule, the ability to plan daily activities, the adequacy of time to complete watch duties, the availability of time for off-watch duties/shipboard-departmental qualifications, and higher alertness/better ability to focus were considered the strengths of the D5/N3. Overall, the D5/N3 has the potential to be a useful alternative to existing 3-section watch standing schedules in terms of crew alertness levels, acceptance by the crewmembers, and workload management when working in a Navy vessel. Because it is a novel schedule, however, more effort should be focused on how to best implement the D5/N3 on a ship, and on the factors that affect its use at sea.
Behavioral Sleep Medicine, Feb 15, 2019
Journal of Sleep Research, Jan 31, 2022
SummarySleep inertia is the brief period of performance impairment and reduced alertness experien... more SummarySleep inertia is the brief period of performance impairment and reduced alertness experienced after waking, especially from slow‐wave sleep. We assessed the efficacy of polychromatic short‐wavelength‐enriched light to improve vigilant attention, alertness and mood immediately after waking from slow‐wave sleep at night. Twelve participants (six female, 23.3 ± 4.2 years) maintained an actigraphy‐confirmed sleep schedule of 8.5 hr for 5 nights, and 5 hr for 1 night prior to an overnight laboratory visit. In the laboratory, participants were awakened from slow‐wave sleep, and immediately exposed to either dim, red ambient light (control) or polychromatic short‐wavelength‐enriched light (light) for 1 hr in a randomized crossover design. They completed a 5‐min Psychomotor Vigilance Task, the Karolinska Sleepiness Scale, and Visual Analogue Scales of mood at 2, 17, 32 and 47 min after waking. Following this testing period, lights were turned off and participants returned to sleep. They were awakened from their subsequent slow‐wave sleep period and received the opposite condition. Compared with the control condition, participants exposed to light had fewer Psychomotor Vigilance Task lapses (χ2[1] = 5.285, p = 0.022), reported feeling more alert (Karolinska Sleepiness Scale: F1,77 = 4.955, p = 0.029; Visual Analogue Scalealert: F1,77 = 8.226, p = 0.005), and reported improved mood (Visual Analogue Scalecheerful: F1,77 = 8.615, p = 0.004). There was no significant difference in sleep‐onset latency between conditions following the testing period (t10 = 1.024, p = 0.330). Our results suggest that exposure to polychromatic short‐wavelength‐enriched light immediately after waking from slow‐wave sleep at night may help improve vigilant attention, subjective alertness, and mood. Future studies should explore the potential mechanisms of this countermeasure and its efficacy in real‐world environments.
Human Factors, Mar 20, 2015
The aim of this study was to assess effectiveness of an alternative, 24-hr-on/72-hr-off watchstan... more The aim of this study was to assess effectiveness of an alternative, 24-hr-on/72-hr-off watchstanding schedule on sleep and morale of personnel assigned to the President's Emergency Operations Center (PEOC). Background: As part of the White House Military Office, PEOC personnel historically worked a 12-hr "Panama" watch schedule. Personnel reported experiencing chronic insufficient and disrupted sleep patterns and sought advice for improving their watchstanding schedule. Method: Participants (N = 14 active-duty military members, ages 29 to 42 years) completed the Profile of Mood State (POMS) three times: before, during, and after switching to the alternative schedule with 5-hr sleep periods built into their workday. Participants completed a poststudy questionnaire to assess individual schedule preferences. Sleep was measured actigraphically, supplemented by activity logs. Results: As indicated by POMS scores, mood improved significantly on the new schedule. Although average total sleep amount did not change substantively, the timing of sleep was more consistent on the new schedule, resulting in better sleep hygiene. PEOC personnel overwhelmingly preferred the new schedule, reporting not only that they felt more rested but that the new schedule was more conducive to the demands of family life. Conclusions: Demands of family life and time spent commuting were found to be critical factors for acceptance of the alternative schedule. This new schedule will be most effective if personnel adhere to the scheduled rest periods assigned during their 24-hr duty. Application: A successful schedule should avoid conflicts between social life and operational demands. Results may lead to changes in the work schedules of other departments with similar 24/7 responsibilities.
Proceedings of the Human Factors and Ergonomics Society ... Annual Meeting, Sep 1, 2017
Sleep problems are prevalent in the naval operational environment. Crewmembers attribute some of ... more Sleep problems are prevalent in the naval operational environment. Crewmembers attribute some of these problems to habitability-related issues in their berthing compartments. This study has two goals: first, to assess the provisions in current habitability standards used in ship design; and second, to assess the extent to which habitability factors in berthing compartments affect the sleep of crewmembers in United States Navy (USN) ships. Results from eight field studies show that environmental conditions (e.g., temperature, noise, light, air quality) affect sleep quality in berthing spaces. Despite the provisions in current standards, sleep-related habitability issues remain a concern for crewmembers in the USN. Our findings suggest that living conditions may be improved in berthing compartments by revising current standards. We have identified three areas for improvement: noise (both continuous and intermittent), temperature within the compartment, and designing berthing compartments according to the organizational structure of the ship.
Military Medicine, Jul 1, 2016
Public reporting burden for this collection of information is estimated to average 1 hour per res... more Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense, Washington Headquarters Services, Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.
Human Factors, Feb 28, 2020
Article reuse guidelines: sagepub. com/ journals-permissions Objective: The study had two objecti... more Article reuse guidelines: sagepub. com/ journals-permissions Objective: The study had two objectives: (a) to assess the prevalence of sleep-related habitability concerns in the berthing compartments of U.S. Navy surface ships and (b) to assess whether habitability issues in berthing compartments affected the sleep and well-being of crew members. Background: The importance of habitability for human well-being is recognized. Little is known, however, about the association between habitability factors in the sleeping/berthing compartments and sailor wellbeing in operational conditions. Method: Fit-for-duty sailors (N = 1,269; from six ships) participated in this naturalistic and longitudinal study. Sailors reported habitability factors affecting their sleep and completed four standardized questionnaires to assess daytime sleepiness, insomnia, sleep quality, and mood. Sleep was assessed through wrist-worn actigraphy and activity logs. Results: Noise, ambient temperature, poor bedding conditions, and ambient light were the most frequently reported factors of concern. Compared to their peers with fewer complaints, sailors with more habitability-related complaints were more likely to have elevated daytime sleepiness (by 23%) and to report insomnia symptoms (145%) and lower sleep quality (21%). Sailors who reported more habitabilityrelated issues also tended to sleep longer. Individuals with more complaints about habitability also tended to report worse mood (total mood disturbance, tension/anxiety, depression, fatigue, and confusion/ bewilderment). Conclusion: Habitability-related complaints are associated with sailor well-being and sleep. Future studies should expound on the various detrimental factors that degrade conditions in berthing compartments and negatively impact crew well-being. Application: Habitability in berthing compartments of surface ships is associated with sailors' daytime sleepiness, insomnia severity, mood, and sleep attributes. Ship designers should take these findings into consideration and investigate viable and cost-effective methods to mitigate the problems we identified.
Proceedings of the Human Factors and Ergonomics Society ... Annual Meeting, Sep 1, 2018
Members of the military get inadequate sleep due to a variety of reasons. Reduced manning, extend... more Members of the military get inadequate sleep due to a variety of reasons. Reduced manning, extended work hours, shiftwork schedules that result in circadian misalignment-all of these factors contribute to the sleep debt and degraded alertness observed in much of the military population. The issue of watchstanding schedules, performance, and alertness is of critical importance to the US military and is the focus of the current study. Based on a sample of active duty military members (N=75), this study had two goals. First, to conduct a field-based monitoring of the sleep and performance of military personnel while performing their duties. Second, to create and validate optimal recommendations based on the results of this empirical study. Participants wore actigraphs over a two-week period, completed daily activity logs, and took threeminute reaction time tests before and after standing watch on their regular schedules. Participants worked on a 2-day on/2-day off schedule, either in 3-section 8-hour shifts, or 2-section 12-hour shifts. Although there were no significant differences in the sleep amounts between the two schedules, results showed that participants on 8-hr shifts had fewer errors and less variable reaction time performance than those working 12-hr shifts. The 8-hr group reported better sleep quality, too. Our results suggest that the 8-hour schedule is better than the 12-hour schedule in terms of sleep and performance but may be more difficult to be applied. This study clearly shows the difficulty of implementing a specific watchstanding schedule in operational environments overloaded with unplanned, and irregular operational duties.
Sleep, May 25, 2022
Introduction: A recent population shift has increased residents of high-altitude locations. Addit... more Introduction: A recent population shift has increased residents of high-altitude locations. Additionally, travel infrastructure has created the opportunity for rapid displacement to high altitudes without adaptation. Residing at high-altitude is a physiological challenge, which increases the risk of overnight hypoxia from sleep disordered breathing. Sleep disordered breathing, including sleep apnea, is a risk factor for a variety of additional negative health outcomes. Additional information is needed to understand the physiology of high-altitude adaptation in generationally un-adapted residents and prevent negative health outcomes. Methods: Healthy residents of high altitude participated in this community-supported observational study. Health and altitude history were gathered. Participants completed one night of overnight oxygen monitoring with finger pulse oximetry. Participants with BMI >30 kg/m2, sleep time <4 or >10 hours were excluded. Results: Total of 41 participants included, 68.3% female, 44.9±13.0 years (SD), BMI 23.7±2.5 kg/m2. Participants resided at altitudes between 2500-3048 m. Participants were also characterized by their years at altitude and percent of life spent at altitude, average 15.9±12.2 years (median 13) and average 33.0±21.7% of life at altitude. Neither years or percent of life at altitude were predicted percent of time below 88% O2 on overnight pulse oximetry (R2 = 0.04 and 0.03, both p>0.12). Multiple Linear Regression indicated BMI was the only factor that explained a signification portion of the variance in adaptation (p<0.01). Conclusion: In a generationally un-adapted population of highaltitude residents, years at altitude and percent of life at altitude do not explain the variance of adaptation to altitude as measured by percent of night spent hypoxic with less than 88% SpO2. While these data do not provide support for an adaptation response based on time at altitude, they indicate future directions in human altitude adaptation should focus on other covariates, potentially including genetic differences. Support (If Any
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Papers by Nita Lewis Shattuck