Nita Lewis Shattuck

Psychomotor vigilance performance predicted by Epworth Sleepiness Scale scores in an operational setting with the United States Navy

It is critical in operational environments to identify individuals who are at higher risk of psychomotor performance impairments. This study assesses the utility of the Epworth Sleepiness Scale for predicting degraded psychomotor vigilance performance in an operational environment. Active duty crewmembers of a USA Navy destroyer (N = 69, age 21–54 years) completed the Epworth Sleepiness Scale at the beginning of the data collection period. Participants wore actigraphs and completed sleep diaries for 11 days. Psychomotor vigilance tests were administered throughout the data collection period using a 3‐min version of the psychomotor vigilance test on the actigraphs. Crewmembers with elevated scores on the Epworth Sleepiness Scale (i.e. Epworth Sleepiness Scale >10) had 60% slower reaction times on average, and experienced at least 60% more lapses and false starts compared with individuals with normal Epworth Sleepiness Scale scores (i.e. Epworth Sleepiness Scale ≤10). Epworth Sleepiness Scale scores were correlated with daily time in bed (P < 0.01), sleep (P < 0.05), mean reaction time (P < 0.001), response speed 1/reaction time (P < 0.05), slowest 10% of response speed (P < 0.001), lapses (P < 0.01), and the sum of lapses and false starts (P < 0.001). In this chronically sleep‐deprived population, elevated Epworth Sleepiness Scale scores identified that subset of the population who experienced degraded psychomotor vigilance performance. We theorize that Epworth Sleepiness Scale scores are an indication of personal sleep debt that varies depending on ones individual sleep requirement. In the absence of direct performance metrics, we also advocate that the Epworth Sleepiness Scale can be used to determine the prevalence of excessive sleepiness (and thereby assess the risk of performance decrements).

Operational assessment of the 5-h on/10-h off watchstanding schedule on a US Navy ship: sleep patterns, mood and psychomotor vigilance performance of crewmembers in the nuclear reactor department

Abstract We assessed sleep patterns, psychomotor vigilance performance, work demands and mood of 77 crewmembers of USS NIMITZ (CVN-68) on the rotating 5-h on/10-h off (5/10) watchstanding schedule. Within the 3-day cycle of the 5/10, sleep occurred at distinctly different times each day. On two of these days, sailors typically received only brief, 4-h sleep episodes followed by periods of sustained wakefulness (approximately 22 and 20 h). Crewmembers received approximately seven hours of sleep daily, but reported excessive fatigue and dissatisfaction with their schedule. Crewmembers’ mood worsened significantly over the course of the underway phase. Psychomotor vigilance performance (reaction times, lapses) was significantly degraded compared to performance when working circadian-aligned schedules. Overall, standing watch on the 5/10 schedule, combined with other work duties, resulted in poor sleep hygiene. Crewmembers on the 5/10 experienced periodic bouts of sustained wakefulness and accrued a significant sleep debt due to extended workdays and circadian-misaligned sleep. Practitioner summary: We assessed crewmembers’ sleep patterns, psychomotor vigilance performance and work demands when working a rotating 5-h on/10-h off (5/10) watchstanding schedule. The 5/10, combined with other work duties, resulted in poor sleep hygiene. Crewmembers experienced periodic bouts of sustained wakefulness and accrued a significant sleep debt due to extended workdays and circadian-misaligned sleep.

Assessment of a Novel Watchstanding Schedule on an Operational us Navy Vessel

One watchstanding schedule used in the US Navy is the modified 6-hr on/18-hr off, a 6-hr watch followed by an 18-hr non-watch period. In this four-section watchbill, rather than standing the same 6-hour period each day, two 3-hr watches are “dogged”, resulting in a day shorter than 24-hrs in length. We assessed the 6-hr on/18-hr off schedule to determine its affordance of rest/sleep and psychomotor vigilance, comparing it to a 3-hr on/9-hr off schedule. Results show the 3-hr on/9-hr off schedule is superior, affording 0.63 more hours of rest daily (p=0.054), 0.89 more hours of sleep daily (p=0.024), and decreased variability in psychomotor vigilance (i.e., reaction time and lapses) compared to the standard schedule (p<0.05). Variability of daily rest and sleep is also reduced (p<0.05). Subjective assessments between the 3-hr on/9-hr off and seven other watch schedules showed that participants preferred the 3-hr on/9-hr off schedule. The 3-hr on/9-hr off schedule yields better sleep hygiene, more stable performance and is well-accepted by crewmembers.

Comparison of a Circadian-based and a Forward Rotating Watch Schedules on Sleep, Mood, and Psychomotor Vigilance Performance

In the military, any degradation in performance may have serious implications, potentially resulting in loss of life or affecting mission accomplishment. The maritime environment imposes the additional unique challenges of waterborne motion on the shipboard crew. Additionally, the U.S. Navy’s 24/7 operational requirements mandate rigorous equipment monitoring and shiftwork. This study assesses how crewmember sleep hygiene and psychomotor vigilance performance is affected by a shift from traditional work schedules to an alternative circadian-based schedule. Twenty-eight sailors were assessed while working two watch schedules, a conventional 5-hours on/10-hours off (5/10) rapidly rotating schedule, and an alternative 3-hours on/9-hours off (3/9) fixed schedule. Average daily sleep duration was the same for both watch schedules. However, compared to their scores on the 5/10, sailors on the 3/9 had significantly less daytime sleepiness, improved mood, 30% faster reaction times, and had 40% to 50% fewer errors (i.e., lapses combined with false starts). The significant improvements in performance, mood, and sleep hygiene observed in this within-subjects study suggest that circadian watch schedules should be chosen rather than non-circadian aligned schedules.

Wounded in Action: What the Sleep Community can Learn from Sleep Disorders of US Military Service Members

159 Editorial—Shattuck and Brown The tragic events of September 11, 2001, changed the fabric of American society in a myriad of ways. On that single day, thousands of lives were lost, all commercial flights were cancelled, and our nation and the world adjusted to a new normal that acknowledged terrorist organizations could dramatically disrupt our existence. For most civilians, the changes following the 9/11 attacks were slight inconveniences: for example, screening in airports and public buildings was heightened and travel restrictions were intensified. However, for members of the U.S. military, the events of 9/11 resulted in a significant increase in operational tempo and combat tours away from family and friends to support the operational mission of the “global war on terror.” The military population enters service after being closely screened for illness and disability. In general, members of the military start out as comparatively healthy young men and women, entering the service between 17 and 20 years of age.1 The entry and retention standards for US military service are rigorous: applicants must meet and maintain minimum standards in physical fitness, body fat, medical screening (to include both physical and mental health), and aptitude.2,3 However, these relatively healthy individuals do not stay that way. The reasons for the change in their health status—in particular, the development of sleep disorders—is of paramount interest to the sleep community. The military has long been known for its culture of insufficient sleep. For many individuals in the military, sleep is considered a luxury or even a weakness. In his illuminating article on the ethical responsibilities of military commanders, Shay4 argues that leaders must get adequate sleep in order to properly care for their troops. He cites historical examples dating back to the ancient Greeks which explore the origins of the mythical warrior who rarely sleeps. For millennia, military life and combat exposure have been inextricably linked to psychological stress and problematic sleep. Studies of “battle fatigue,” now termed posttraumatic stress disorder, or PTSD, from as far back as the U.S. Civil War document the central role of sleep disorders following combat exposure.5-8 The military culture requires round-the-clock operations, which produces acute and chronic sleep deprivation levels in a population that makes high-risk decisions and operEDITORIAL

Sleep and performance in simulated Navy watch schedules

To operate Navy ships 24h per day, watchstanding is needed around the clock, with watch periods reflecting a variety of rotating or fixed shift schedules. The 5/15 watch schedule cycles through watch periods with 5h on, 15h off watch, such that watches occur 4h earlier on the clock each day - that is, the watches rotate backward. The timing of sleep varies over 4-day cycles, and sleep is split on some days to accommodate nighttime watchstanding. The 3/9 watch schedule cycles through watch periods with 3h on, 9h off watch, allowing for consistent sleep timing over days. In some sections of the 3/9 watch schedule, sleep may need to be split to accommodate nighttime watchstanding. In both the 5/15 and 3/9 watch schedules, four watch sections alternate to cover the 24h of the day. Here we compared sleep duration, psychomotor vigilance and subjective sleepiness in simulated sections of the 5/15 and 3/9 watch schedules. Fifteen healthy male subjects spent 6 consecutive days (5 nights) in the laboratory. Sleep opportunities were restricted to an average of 6.5h daily. Actigraphically estimated sleep duration was 5.6h per watch day on average, with no significant difference between watch sections. Sleep duration was not reduced when sleep opportunities were split. Psychomotor vigilance degraded over watch days, and tended to be more variable in the 5/15 than in the 3/9 watch sections. These laboratory-based findings suggest that Navy watch schedules are associated with cumulative sleep loss and a build-up of fatigue across days. The fixed watch periods of the 3/9 watch schedule appear to yield more stable performance than the backward rotating watch periods of the 5/15 watch schedule. Optimal performance may require longer and more consistent daily opportunities for sleep than are typically obtained in Navy operations.

Prevalence of Musculoskeletal Symptoms, Excessive Daytime Sleepiness, and Fatigue in the Crewmembers of a U.S. Navy Ship

OBJECTIVES We assessed the prevalence of, and association among, musculoskeletal (MSK) symptoms, reported sleep, daytime alertness, fatigue, and consumption of caffeinated beverages. METHODS Crewmembers of a U.S. Navy aircraft carrier (N = 767) completed a survey pertaining to demographics, exercise frequency, sleep duration, caffeinated beverages consumption, daytime sleepiness, fatigue, and MSK symptoms occurrence. RESULTS Participants reported 6.12 hours of sleep per day while at sea, 31.8% reported increased daytime sleepiness, whereas 9% reported elevated fatigue levels. The 12-month prevalence of MSK symptoms was 57.5%, and the 7-day prevalence was 44.4%. Approximately 20% reported that MSK symptoms prevented them from carrying out normal activities. The lower back (39.5%) and knees (33.6%) were the two body parts most frequently reported for MSK symptoms. Symptoms in lower back, knees, and ankles/feet had an increased impact on preventing crewmembers from carrying out daily activities. Symptomatic crewmembers were more likely to report elevated daytime sleepiness, increased fatigue level, shorter nighttime sleep duration, and consume more caffeinated beverages. CONCLUSION MSK symptoms were frequent and frequently prevented crewmembers from carrying out their daily activities. From an occupational health perspective, interventions to optimize sleep hygiene in the naval environment should also address the impact of MSK symptoms as a confounding factor.

Caffeinated Beverage Consumption Rates and Reported Sleep in a United States Navy Ship

Ship crews live and work in an environment characterized by extreme sleep deprivation. In an attempt to maintain alertness, crewmembers frequently consume caffeinated beverages and energy drinks. As part of a broader study, this work assesses the consumption of caffeinated beverages and investigates the association between caffeinated beverage consumption and reported sleep amount. Crewmembers of a U.S. Navy aircraft carrier (N=767; age 18-49 years) completed a survey with questions pertaining to demographics, exercise frequency, average sleep duration, caffeine beverage consumption, the Epworth Sleepiness Scale (ESS), and the Fatigue Severity Scale (FSS). Results show that the sample of active duty personnel slept approximately six hours per night. Most respondents (~90%) reported using at least one type of caffeinated beverage (~55% coffee, ~50% soft drinks, ~35% energy drinks, and ~35% tea). The participants who reported drinking caffeinated drinks had an average weekly caffeine intake of 812±917 mg (MD=540), ranging from 30 to 9210 mg. Crewmembers who consumed more than 1,270 mg of caffeine weekly (equivalent to 180 mg daily) reported sleeping 5.79±1.17 hours, whereas crewmembers that drank less than 1,270 mg of caffeine reported sleeping 6.17±1.07 hours (p<0.001). Overall, our study shows widespread use of caffeine among active duty crewmembers in our sample. Our results suggest that caffeine intake – in the form of coffee, tea, caffeinated soft drinks, or energy drinks – is associated with sleep and may interfere with sleep patterns while working at sea. Future efforts should be directed at exploring causal relationships involved in this phenomenon. Better understanding of causal links will enable appropriate guidance for better sleep hygiene in the maritime operational environment.

Comparison of Two Watch Schedules for Personnel at the White House Military Office President’s Emergency Operations Center

Objective 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.

Sleep Duration in Rough Sea Conditions.

INTRODUCTION Environmental motion can affect 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 different sea conditions. METHODS Crewmembers (N = 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. RESULTS In rough sea conditions, crewmembers experienced increased severity of motion sickness and sopite syndrome compared to their ratings during calmer sea conditions. Crewmembers slept significantly longer during sea state 5-6 compared to sleep on days with sea state 4 (25% increase) and sea state 3-4 (30% increase). Specifically, daily sleep increased from 6.97 ± 1.24 h in sea state 3-4, to 7.23 ± 1.65 h in sea state 4, to 9.04 ± 2.90 h in sea state 5-6. DISCUSSION Although the duration of sleep in rough seas increased significantly 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.