Recipe for fatigue: sleep, work patterns, and well-being of galley workers on surface ships of the US Navy.

Study Objectives: The purpose of the study was to compare the fatigue levels, work/rest patterns, health-related behaviors, and well-being of galley workers with other sailors on US Navy ships while underway. Methods: Analysis was based on a retrospective comparison of data from 3 fit-for-duty groups of sailors: 67 galley workers, 192 non-watchstanders, and 466 watchstanders. Participants completed questionnaires (Epworth Sleepiness Scale [ESS], Insomnia Severity Index [ISI], Pittsburgh Sleep Quality Index [PSQI], and Profile of Mood States [POMS]) and activity logs, and wore actigraphs. Results: Galley workers slept MD = 6.57 (IQR = 1.42) h/d and worked MD = 12.8 (IQR = 2.42) h/d. Approximately 84% of the galley workers were classified as poor sleepers, ~57% reported having excessive daytime sleepiness (EDS), and ~38% reported elevated insomnia symptoms. Compared to non-watchstanders, galley workers had worse scores on POMS (total mood disturbance, tension-anxiety, depression, anger-hostility, fatigue, and confusion-bewilderment), ESS, ISI, and PSQI. Compared to non-watchstanders, galley workers had a higher risk for symptoms of EDS (75%), symptoms of clinically relevant insomnia (126%), and for being classified as poor sleepers (27%). Galley workers slept less and worked on average 2 h/d more than non-watchstanders. Compared to watchstanders, galley workers had worse ESS, ISI, and anger-hostility scores. More watchstanders napped compared to galley workers. Conclusions: Although they are considered day workers, the sleep patterns, fatigue levels, and mood of galley workers are comparable to, or worse than, watchstanders or other non-watchstanders. To ameliorate the effects of long work hours on sailor well-being, ship leadership should consider adopting strategies to improve galley workers' well-being.

Erratum: Reconfigurations in brain networks upon awakening from slow wave sleep: Interventions and implications in neural communication.

[This corrects the article DOI: 10.1162/netn_a_00272.].

Sleepy and grumpy go hand in hand for US Navy Sailors.

Study Objectives: The study explores how sleep, sleep-related practices, and behaviors, in addition to various demographic and occupational characteristics, are related to overall mood of US Navy sailors when they are underway. Methods: Longitudinal assessment of US Navy sailors performing their underway duties (N = 873, 79.2% males, median age 25 years). Participants completed standardized questionnaires, wore wrist-worn actigraphs, and completed daily activity logs. Results: Sailors who reported worse profile of mood states (POMS) total mood disturbance scores had shorter sleep duration, worse sleep quality, and more episodes of split sleep. The group with worse mood also reported more symptoms of excessive daytime sleepiness as well as more symptoms of insomnia. In addition to sleep results, sailors with worse mood also tended to be younger, more likely to use nicotine and tobacco products, and less likely to have an exercise routine when compared to sailors with better POMS scores. Finally, the group with worse POMS scores included more enlisted personnel, tended to work more hours per day, and were more likely to stand watch-especially on rotating watch schedules. Conclusions: The results found significant associations between the sleep practices and mood of sailors aboard US Navy ships. Numerous other demographic and occupational factors were also strongly associated with mood. This paper is part of the Sleep and Circadian Rhythms: Management of Fatigue in Occupational Settings Collection.

An at-home evaluation of a light intervention to mitigate sleep inertia symptoms.

OBJECTIVES: Under laboratory settings, light exposure upon waking at night improves sleep inertia symptoms. We investigated whether a field-deployable light source would mitigate sleep inertia in a real-world setting. METHODS: Thirty-six participants (18 female; 26.6 years ± 6.1) completed an at-home, within-subject, randomized crossover study. Participants were awoken 45 minutes after bedtime and wore light-emitting glasses with the light either on (light condition) or off (control). A visual 5-minute psychomotor vigilance task, Karolinska sleepiness scale, alertness and mood scales, and a 3-minute auditory/verbal descending subtraction task were performed at 2, 12, 22, and 32 minutes after awakening. Participants then went back to sleep and were awoken after 45 minutes for the opposite condition. A series of mixed-effect models were performed with fixed effects of test bout, condition, test bout × condition, a random effect of the participant, and relevant covariates. RESULTS: Participants rated themselves as more alert (p = .01) and energetic (p = .001) in the light condition compared to the control condition. There was no effect of condition for descending subtraction task outcomes when including all participants, but there was a significant improvement in descending subtraction task total responses in the light condition in the subset of participants waking from N3 (p = .03). There was a significant effect of condition for psychomotor vigilance task outcomes, with faster responses (p < .001) and fewer lapses (p < .001) in the control condition. CONCLUSIONS: Our findings suggest that light modestly improves self-rated alertness and energy after waking at home regardless of sleep stage, with lower aggression and improvements to working memory only after waking from N3. Contrary to laboratory studies, we did not observe improved performance on the psychomotor vigilance task. Future studies should include measures of visual acuity and comfort to assess the feasibility of interventions in real-world settings.

Reconfigurations in brain networks upon awakening from slow wave sleep: Interventions and implications in neural communication.

Sleep inertia is the brief period of impaired alertness and performance experienced immediately after waking. Little is known about the neural mechanisms underlying this phenomenon. A better understanding of the neural processes during sleep inertia may offer insight into the awakening process. We observed brain activity every 15 min for 1 hr following abrupt awakening from slow wave sleep during the biological night. Using 32-channel electroencephalography, a network science approach, and a within-subject design, we evaluated power, clustering coefficient, and path length across frequency bands under both a control and a polychromatic short-wavelength-enriched light intervention condition. We found that under control conditions, the awakening brain is typified by an immediate reduction in global theta, alpha, and beta power. Simultaneously, we observed a decrease in the clustering coefficient and an increase in path length within the delta band. Exposure to light immediately after awakening ameliorated changes in clustering. Our results suggest that long-range network communication within the brain is crucial to the awakening process and that the brain may prioritize these long-range connections during this transitional state. Our study highlights a novel neurophysiological signature of the awakening brain and provides a potential mechanism by which light improves performance after waking.

Sex differences in perceptions of sleep inertia following nighttime awakenings.

Study Objectives: The influence of biological sex on sleep inertia symptoms is currently unknown. We investigated the role of sex differences in the subjective experience and objective cognitive manifestation of sleep inertia following nighttime awakenings. Methods: Thirty-two healthy adults (16 female, 25.91 ±â€…5.63 years) completed a 1-week at-home study with one experimental night during which sleep was measured by polysomnography and participants were awakened during their habitual sleep time. Participants completed a psychomotor vigilance task, Karolinska Sleepiness Scale (KSS), visual analog mood scales, and a descending subtraction task (DST) prior to sleep (baseline) and at 2, 12, 22, and 32 min after awakening. A series of mixed-effects models with Bonferroni-corrected post hoc tests were used to examine the main effects of test bout and sex, and their interaction, with a random effect of participant, and order of wake-up and sleep history as covariates. Results: All outcomes except for percent correct on the DST showed a significant main effect of test bout, with worse performance after waking compared to baseline (all ps < .003). Significant effects of sex (p = .002) and sex × test bout (p = .01; R2M = 0.49, R2C = 0.69) were observed for KSS, with females reporting a greater increase in sleepiness from baseline to after waking compared to males. Conclusions: These results suggest that while females reported feeling sleepier than males following nighttime awakenings, their cognitive performance was comparable. Future research is needed to determine whether perceptions of sleepiness influence decision-making during the transition from sleep to wakefulness.

Cervical headgear therapy and sleep-related attributes.

INTRODUCTION: The study aimed to assess (1) the effect of the treatment with cervical headgear on patients' sleep-related attributes and well-being and (2) whether these sleep-related parameters (ie, sleep quality and quantity) were associated with patients' compliance during the orthodontic treatment. METHODS: The study protocol was based on a prospective longitudinal quasi-experimental design. Participants (n = 26; 9 males; mean age, 12.4 ± 1.68 years) were patients in the Postgraduate Orthodontic Clinic, National and Kapodistrian University of Athens. All patients received treatment with a cervical headgear having an embedded TheraMon microsensor. Sleep was assessed by wrist-worn actigraphy for 59 ± 19 days. The Epworth Sleepiness Scale was used to assess average daytime sleepiness, whereas we used the Athens Insomnia Scale for insomnia symptoms. Oral health-related quality of life (OHRQOL) was assessed by the Oral Health Impact Profile (OHIP-14). RESULTS: Patients slept on average 7.35 ± 0.42 h/d. Compared with the lowest sleep duration recommended for their age group, patients had an average chronic sleep deficit of 1.40 ± 0.49 h/d. Patients wore the headgear 90.9% of the days for 10.40 ± 4.17 h/d. However, only 7 (28%) patients reached or exceeded the wear-time recommendation of 12 h/d. In contrast, 2 (8%) patients wore headgear <5 h/d, 11 (44%) 5-10 h/d, and 12 (48%) patients wore headgear >10 h/d. Aggregated by participants, the median Epworth Sleepiness Scale score during the study was 3.40 (interquartile range [IQR], 4.85; range, 0.2-13.6), the median Athens Insomnia Scale score was 3.00 (IQR, 4.25; range, 0-7), and the median Oral Health Impact Profile score was 1.40 (IQR, 4.17; range, 0.0-20.8). Compared with patients who wore the orthodontic appliance >7.8 h/d, patients who wore it <7.8 h/d had worse average daytime sleepiness (P = 0.050) and worse OHRQOL (P = 0.019). CONCLUSIONS: Orthodontic treatment with cervical headgear has no substantive negative effect on sleep attributes (quantity and quality), average daytime sleepiness and OHRQOL. However, poor compliance with orthodontic treatment seems to be associated with higher levels of daytime sleepiness.

Using Light to Facilitate Circadian Entrainment from Day to Night Flights.

BACKGROUND: As part of a larger project to provide recommendations regarding limitations and best practices for shifting aviators from day to night operations, a study was conducted to assess the efficacy of high energy visible (HEV) light to shift the circadian rhythm in humans. The study attempted to replicate the patterns of military aviators who could be required to shift abruptly from day to night flight operations.METHODS: Simulated flight performance and salivary melatonin levels of 10 U.S. military aviators were collected over a 3-night period using a within-subject dim light melatonin onset (DLMO) study design. Data were collected in a laboratory with participants returning home to sleep following each of the three evenings/nights of data collection. Light treatment included a single 4-h exposure of blue-enriched white light (∼1000 lux) on night 2. Data collected included melatonin levels, light exposure, sleepiness, cognitive workload, and simulated flight performance.RESULTS: The average delay in melatonin onset was 1.32 ± 0.37 h (range: 53 min to 1 h 56 min). Sleepiness (P = 0.044) and cognitive workload (P = 0.081) improved the night following the light treatment compared to the baseline. No systematic differences were identified in flight performance.DISCUSSION: The HEV light treatment successfully delayed the circadian phase of all participants even though participants' ambient light levels (including daylight) outside the laboratory were not controlled. These findings were used to develop circadian synchronization plans for aviators who are asked to transition from day to night operations. These plans will be assessed in a follow-on study in an operational unit.Shattuck NL, Matsangas P, Reily J, McDonough M, Giles KB. Using light to facilitate circadian entrainment from day to night flights. Aerosp Med Hum Perform. 2023; 94(2):66-73.

Who sleeps more and who works longer in the US Navy: Officers or enlisted personnel?

OBJECTIVES: To determine whether United States Navy (USN) officers and enlisted personnel have different sleep and work patterns while underway on USN surface ships. METHODS: Variables of interest were assessed by actigraphy, activity logs, and validated questionnaires. RESULTS: The 2 groups had similar daily sleep (officers: 6.41 ± 0.95 hrs/day; enlisted: 6.57 ± 0.97 hrs/day) and work duration. Enlisted personnel, however, were more likely to report excessive daytime sleepiness-EDS (41% more likely), clinically relevant insomnia (105%), to have both EDS and elevated insomnia (121%), to be classified as poor sleepers (17%), to use nicotine products (174%), and to forego routine exercise (57%). Enlisted personnel were 487% more likely to report all 3 of these behaviors: drink caffeinated beverages, use nicotine/tobacco products, forego routine exercise. CONCLUSIONS: Even though the work and sleep hours do not differ significantly, the state of well-being of enlisted personnel is in general lower than officers. Our findings can provide insight to Navy leadership towards improving sailor well-being and crew endurance.

Rise and shine: The use of polychromatic short-wavelength-enriched light to mitigate sleep inertia at night following awakening from slow-wave sleep.

Sleep 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.

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.

Physiological and Cognitive Performance in F-22 Pilots During Day and Night Flying.

BACKGROUND: Many workers routinely transition between day and night shiftsincluding pilots, where night flights are commonly considered more stressful. The physiological toll from this transition is not fully understood, though fatigue is a factor in many aviation accidents. This research investigated the changes in physiological markers of stress and cognitive performance as F-22 pilots transitioned from day flying to night flying.METHODS: There were 17 fully-qualified F-22 pilots who took part in a 2-wk data collection using salivary swabs, wrist-worn activity monitors, the National Aeronautics and Space Administration-Task Load Index (NASA-TLX) inventory, and a go/no-go (GNG) test.RESULTS: No differences were found in comparing day and night flying on the GNG reaction time/accuracy, NASA-TLX scores, or sleep quantity. Cortisol levels were significantly higher than civilian levels in all experimental conditions and control days. Participants had higher than predicted cortisol levels postflight in the day-flying condition and lower than predicted cortisol levels postflight in the night-flying condition, relative to levels from control day patterns. We also found smaller changes in cortisol (pre- to postflight) in the day-flying condition for those with more F-22 experience. Finally, we found a negative correlation between Perceived Stress Scale scores and age of pilots (r 0.72).DISCUSSION: We hypothesized that the night-flying environment would be more stressful, but our results disputed this claim. Our results suggest day flying elicits more of a stress response; however, a larger sample size is required to verify results. Preliminary findings of potential stress adaptation may suggest stress adaptation in the F-22 community needs further investigation.Combs EK, Dahlman AS, Shattuck NL, Heissel JA, Whitaker LR. Physiological and cognitive performance in F-22 pilots during day and night flying. Aerosp Med Hum Perform. 2021; 92(5):303311.

Eating behaviors in sailors of the United States Navy: Meal-to-sleep intervals.

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 = 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.

Habitability in Berthing Compartments and Well-Being of Sailors Working on U.S. Navy Surface Ships.

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 well-being 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 habitability-related 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.

Does the quality of life differ for shift workers compared to day workers?

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.

Sleep quality, occupational factors, and psychomotor vigilance performance in the U.S. Navy sailors.

STUDY OBJECTIVES: This field study (a) assessed sleep quality of sailors on the U.S. Navy (USN) ships while underway, (b) investigated whether the Pittsburgh Sleep Quality Index (PSQI) scores were affected by occupational factors and sleep attributes, and (c) assessed whether the PSQI could predict impaired psychomotor vigilance performance. METHODS: Longitudinal field assessment of fit-for-duty USN sailors performing their underway duties (N = 944, 79.0% males, median age 26 years). Participants completed questionnaires, wore actigraphs, completed logs, and performed the wrist-worn 3-min Psychomotor Vigilance Task (PVT). RESULTS: Sailors slept on average 6.60 ± 1.01 h/day with 86.9% splitting their sleep into more than one episode/day. The median PSQI Global score was 8 (interquartile range [IQR] = 5); 80.4% of the population were classified as "poor sleepers" with PSQI scores >5. PSQI scores were affected by sailor occupational group, rank, daily sleep duration, and number of sleep episodes/day. Sleep quality showed a U-shape association with daily sleep duration due to the confounding effect of split sleep. Sailors with PSQI scores >9 had 21.1% slower reaction times (p < 0.001) and 32.8%-61.5% more lapses combined with false starts (all p < 0.001) than sailors with PSQI scores ≤9. Compared to males and officers, females and enlisted personnel had 86% and 23% higher risk, respectively, of having PSQI scores >9. Sailors in the PSQI > 9 group had more pronounced split sleep. CONCLUSIONS: Working on Navy ships is associated with elevated PSQI scores, a high incidence of poor sleep, and degraded psychomotor vigilance performance. The widely used PSQI score>5 criterion should be further validated in active-duty service member populations.

Hand-Held and Wrist-Worn Field-Based PVT Devices vs. the Standardized Laptop PVT.

BACKGROUND: Given the challenges of collecting reliable Psychomotor Vigilance Task (PVT) data in the field, this study compared a 3-min PVT on a hand-held device and wrist-worn device vs. a standardized laptop.METHODS: The experiment utilized a randomized, repeated-measures design. Subjects (N = 36) performed the PVT on a touch-screen, hand-held device (HHD), a wrist-worn device (WWD), and a standardized laptop (L). Sleep was assessed using wrist-worn actigraphy.RESULTS: Compared to the L, the HHD was slower on average (∼50% longer reaction times; ∼34% slower response speeds; ∼600% more lapses in attention combined with false starts) and introduced a proportional bias that decreased the range of response speeds by 60%. Compared to the L, the WWD with the backlight on was faster on average (reaction time: ∼6%; response speed: ∼13%), but equivalent in lapses combined with false starts, and introduced a proportional bias that increased the range of responses by 60%.DISCUSSION: Compared to the L PVT, using a hand-held, touch screen interface to collect PVT data may introduce a large constant bias and a proportional bias that decreases the range of response speed. However, performance on the WWD closely mirrors performance on the L PVT and the proportional bias tends to be in favor of detecting individuals with slower responses. Researchers should avoid comparing PVT metrics between different device types. Reliability of PVT data from a WWD or HHD may be degraded when used in an operational setting with unpredictable environmental movement (such as a surface maritime setting).Matsangas P, Shattuck NL. Hand-held and wrist-worn field-based PVT devices vs. the standardized laptop PVT. Aerosp Med Hum Perform. 2020; 91(5):409-415.

Assessing Surgical Task Load and Performance: A Comparison of Simulation and Maritime Operation.

INTRODUCTION: This study examined the effects of simulated and actual vessel motion at high seas on task load and surgical performance. METHODS: This project was performed in phases. Phase I was a feasibility study. Phase II utilized a motion base simulator to replicate vessel motion. Phase III was conducted aboard the U.S. Naval Ship Brunswick. After performing surgical tasks on a surgical simulation mannequin, participants completed the Surgical Task Load Index (TLX) designed to collect workload data. Simulated surgeries were evaluated by subject matter experts. RESULTS: TLX scores were higher in Phase III than Phase II, particularly at higher sea states. Surgical performance was not significantly different between Phase II (84%) and Phase III (89%). Simulated motions were comparable in both phases. CONCLUSIONS: Simulated motion was not associated with a significant difference in surgical performance or deck motion, suggesting that this simulator replicates the conditions experienced during surgery at sea on the U.S. Naval Ship Brunswick. However, Surgical TLX scores were dramatically different between the two phases, suggesting increased workload at sea, which may be the result of time at sea, the stress of travel, or other factors. Surgical performance was not affected by sea state in either phase.