Steps toward developing a comprehensive fatigue monitoring and mitigation solution: perspectives from a cohort of United States Naval Surface Force officers.

Study Objectives: This study analyzed fatigue and its management in US Naval Surface Force warships, focusing on understanding current practices and barriers, and examining the influence of organizational and individual factors on managing chronic fatigue. Furthermore, this study explored the impact of organizational and individual factors on fatigue management. Methods: As part of a larger study, 154 naval officers (mean ±â€…standard deviation; 31.5 ±â€…7.0 years; 8.8 ±â€…6.8 years of service; 125 male, and 29 female) completed a fatigue survey. The survey addressed (1) self-reported fatigue, (2) fatigue observed in others, (3) fatigue monitoring strategies, (4) fatigue mitigation strategies, and (5) barriers to fatigue mitigation. Logistic and ordinal regressions were performed to examine the effect of individual (i.e. sleep quality and years in military service) and organizational (i.e. ship-class) factors on fatigue outcomes. Results: Fatigue was frequently experienced and observed by 23% and 54% of officers, respectively. Of note, officers often monitored fatigue reactively (i.e. 65% observed others nodding off and 55% observed behavioral impairments). Still, officers did not frequently implement fatigue mitigation strategies, citing few operationally feasible mitigation strategies (62.3%), being too busy (61.7%), and not having clear thresholds for action (48.7%). Fatigue management varies across organizational factors, which must be considered when further developing fatigue management strategies. Conclusions: Fatigue remains a critical concern aboard surface force ships and it may be better addressed through development of objective sleep and fatigue monitoring tools that could inform leadership decision-making.

Advancing a U.S. navy shipboard infrastructure for sleep monitoring with wearable technology.

Development of fatigue management solutions is critical to U.S. Navy populations. This study explored the operational feasibility and acceptability of commercial wearable devices (Oura Ring and ReadiBand) in a warship environment with 845 Sailors across five ship cohorts during at-sea operations ranging from 10 to 31 days. Participants were required to wear both devices and check-in daily with research staff. Both devices functioned as designed in the environment and reliably collected sleep-wake data. Over 10,000 person-days at-sea, overall prevalence of Oura and ReadiBand use was 69% and 71%, respectively. Individual use rates were 71 ± 38% of days underway for Oura and 59 ± 34% for ReadiBand. Analysis of individual factors showed increasing device use and less device interference with age, and more men than women found the devices comfortable. This study provides initial support that commercial wearables can contribute to infrastructures for operational fatigue management in naval environments.

Daytime Sleep-Tracking Performance of Four Commercial Wearable Devices During Unrestricted Home Sleep.

Purpose: Previous studies have found that many commercial wearable devices can accurately track sleep-wake patterns in laboratory or home settings. However, nearly all previous studies tested devices under conditions with fixed time in bed (TIB) and during nighttime sleep episodes only. Despite its relevance to shift workers and others with irregular sleep schedules, it is largely unknown how devices track daytime sleep. Therefore, we tested the sleep-tracking performance of four commercial wearable devices during unrestricted home daytime sleep. Participants and Methods: Participants were 16 healthy young adults (6 men, 10 women; 26.6 ± 4.6 years, mean ± SD) with habitual daytime sleep schedules. Participants slept at home for 1 week under unrestricted conditions (ie, self-selecting TIB) using a set of four commercial wearable devices and completed reference sleep logs. Wearables included the Fatigue Science ReadiBand, Fitbit Inspire HR, Oura Ring, and Polar Vantage V Titan. Daytime sleep episode TIB biases and frequencies of missed and false-positive daytime sleep episodes were examined. Results: TIB bias was low in general for all devices on most daytime sleep episodes, but some exhibited large biases (eg, >1 h). Total missed daytime sleep episodes were as follows: Fatigue Science: 3.6%; Fitbit: 4.8%; Oura: 6.0%; Polar: 37.3%. Missed episodes occurred most often when TIB was short (eg, naps <4 h). Conclusion: When daytime sleep episodes were recorded, the devices generally exhibited similar performance for tracking TIB (ie, most episodes had low bias). However, the devices failed to detect some daytime episodes, which occurred most often when TIB was short, but varied across devices (especially Polar, which missed over one-third of episodes). Findings suggest that accurate daytime sleep tracking is largely achievable with commercial wearable devices. However, performance differences for missed recordings suggest that some devices vary in reliability (especially for naps), but improvements could likely be made with changes to algorithm sensitivities.

Prevalence and correlates of destructive behaviors in the US Naval Surface Forces from 2010-2020.

PURPOSE: To estimate the prevalence of domestic violence, sexual assault, and suicide for United States Navy (USN) personnel between 2010 and 2020 and identify potential associated factors. METHODS: Official report data were used to calculate prevalence rates and odds ratios, accounting for sample and general USN population demographic data to assess differences in over- or underrepresentation of destructive behaviors. RESULTS: Domestic violence and sexual assault offenders tended to be younger lower-ranked males. For sexual assaults, offenders were three times more likely to be senior to the victim, which was not the case for domestic violence. Females were overrepresented in terms of suicidal ideation and attempts relative to the USN population, while males accounted for more actual suicides. The relative rates of suicidal ideation and attempts for females exceeded those for males (i.e., comparing the sample rate against the USN male and female populations), but the sample proportion for completed suicides (compared to the USN population) were greater for males than for females. Those in the junior enlisted (E1-E3) paygrades exhibited greater odds of suicide attempts versus suicidal ideations relative to those in the Petty Officers (E4-E6) paygrades, although E4-E6s completed more suicides. CONCLUSION: The descriptive profile of destructive behaviors in a representative sample of USN personnel provides an overview of the possible factors associated with destructive behaviors and includes an exploration of the relational dynamics and nature of the incidents. The results suggest that sexual assault and domestic violence are characterized by unique relational dynamics and that these destructive behaviors should not necessarily be classified together as male-oriented aggressions (i.e., mainly perpetrated by males against female victims). Those in the E1-E3 and E4-E6 paygrades displayed different patterns in suicidal ideation, attempts, and actual suicides. The results highlight individual characteristics to help inform the development of targeted policies, practices, and interventions for military and other hierarchical organizations (e.g., police).

Sleep deficiency, operational fatigue and the interplay of compromising factors: Analysis to aid in fatigue management.

The United States Navy is a high-reliability organization that must maintain optimum performance under challenging conditions. One key challenge for sailors is obtaining sufficient sleep, which can lead to fatigue and other outcomes that compromise operational readiness. Identifying sleep issues and their causes is critical for military leaders to care for their personnel, and to make informed, risk-based operational decisions. Though previous studies in shipboard environments have implicated factors responsible for insufficient sleep (e.g. poor sleep environment and work demands), there has been less research into characterizing the complex interplay among such factors in relation to sleep and work-related fatigue outcomes. This study seeks to address this gap. Data were drawn from the Afloat Safety Climate Assessment Survey of 7617 sailors from 73 ships. The survey included demographic characteristics and measures of crew endurance (e.g. sleep, occupational impairment due to fatigue). Descriptive analyses characterized the presence and severity of sleep issues across subpopulations and operational settings (e.g. the type of ship); structural equation modelling techniques characterized and quantified the statistical associations among factors. The results indicate that sleep deficits are widespread, holding across subpopulations and operational settings. Though sleep deficits varied across subpopulations, no group obtained an average of more than 7 hr of sleep per night. Fatigue-induced occupational functional impairment was directly related to sleep deficiency, and sleep environment and job-related factors were contributors to sleep deficiency. Moreover, job-related factors emerged as potentially more consequential. Lastly, factors may exist aboard a ship that could help promote better sleep.

Performance of Four Commercial Wearable Sleep-Tracking Devices Tested Under Unrestricted Conditions at Home in Healthy Young Adults.

Purpose: Commercial wearable sleep-tracking devices are growing in popularity and in recent studies have performed well against gold standard sleep measurement techniques. However, most studies were conducted in controlled laboratory conditions. We therefore aimed to test the performance of devices under naturalistic unrestricted home sleep conditions. Participants and Methods: Healthy young adults (n = 21; 12 women, 9 men; 29.0 ± 5.0 years, mean ± SD) slept at home under unrestricted conditions for 1 week using a set of commercial wearable sleep-tracking devices and completed daily sleep diaries. Devices included the Fatigue Science Readiband, Fitbit Inspire HR, Oura ring, and Polar Vantage V Titan. Participants also wore a research-grade actigraphy watch (Philips Respironics Actiwatch 2) for comparison. To assess performance, all devices were compared with a high performing mobile sleep electroencephalography headband device (Dreem 2). Analyses included epoch-by-epoch and sleep summary agreement comparisons. Results: Devices accurately tracked sleep-wake summary metrics (ie, time in bed, total sleep time, sleep efficiency, sleep latency, wake after sleep onset) on most nights but performed best on nights with higher sleep efficiency. Epoch-by-epoch sensitivity (for sleep) and specificity (for wake), respectively, were as follows: Actiwatch (0.95, 0.35), Fatigue Science (0.94, 0.40), Fitbit (0.93, 0.45), Oura (0.94, 0.41), and Polar (0.96, 0.35). Sleep stage-tracking performance was mixed, with high variability. Conclusion: As in previous studies, all devices were better at detecting sleep than wake, and most devices compared favorably to actigraphy in wake detection. Devices performed best on nights with more consolidated sleep patterns. Unrestricted sleep TIB differences were accurately tracked on most nights. High variability in sleep stage-tracking performance suggests that these devices, in their current form, are still best utilized for tracking sleep-wake outcomes and not sleep stages. Most commercial wearables exhibited promising performance for tracking sleep-wake in real-world conditions, further supporting their consideration as an alternative to actigraphy.

Self-reported sleep and sleep deficiency: Results from a large initiative of sailors attached to U.S. Navy warships.

Chronic insufficient sleep is known to lead to a broad range of negative consequences (e.g. poor health and cognitive performance). While insufficient sleep and associated fatigue are present in many diverse populations, it is of special concern in high-risk military environments, where a mishap can result in catastrophic outcomes. Although many studies have been conducted to characterise sleep in general military populations, relatively few have been conducted using a large representative sample of sailors assigned to United States Naval warships. The present cross-sectional study characterises self-reported sleep parameters in sailors (N = 11,738) and explores the role of possible contributors to insufficient sleep. The results indicate that sailors, across a variety of different subgroups, do not obtain the amount of sleep that they report requiring for feeling well-rested. Of the many potential factors thwarting sleep, workload and an uncomfortable mattress are the most promising candidates to target for improvement.

How word comprehension exposures facilitate later spoken production: implications for lexical processing and repetition priming.

Both comprehension and production exposures to words facilitate spoken production of the same words in picture-naming tasks performed several minutes later. Three experiments examined the mechanisms by which different types of comprehension exposures to words facilitate spoken production. Both overt and silent reading and listening tasks elicited substantial priming in picture naming at 10-minute but not 1-week retention intervals. Relative to silent conditions, encoding conditions that involved speaking the target word overtly elicited stronger priming effects in both RT and accuracy and larger frequency effects in RT. Frequency effects were not reliable in accuracy priming or silent-encoding RT priming. Articulatory suppression did not diminish priming effects relative to silent reading/listening, and priming effects did not depend on whether presentations at encoding were visual or auditory. Together, the results indicate that a common modality-general lemma representation is accessed in comprehension and production, that both lemma and phonological retrieval contribute to repetition priming in production, and that phonological retrieval is sensitive to word frequency. These results are consistent with a theory based on transfer-appropriate processing if word comprehension elicits top-down processing or feedback from the concept to the lemma.

Performance of seven consumer sleep-tracking devices compared with polysomnography.

STUDY OBJECTIVES: Consumer sleep-tracking devices are widely used and becoming more technologically advanced, creating strong interest from researchers and clinicians for their possible use as alternatives to standard actigraphy. We, therefore, tested the performance of many of the latest consumer sleep-tracking devices, alongside actigraphy, versus the gold-standard sleep assessment technique, polysomnography (PSG). METHODS: In total, 34 healthy young adults (22 women; 28.1 ± 3.9 years, mean ± SD) were tested on three consecutive nights (including a disrupted sleep condition) in a sleep laboratory with PSG, along with actigraphy (Philips Respironics Actiwatch 2) and a subset of consumer sleep-tracking devices. Altogether, four wearable (Fatigue Science Readiband, Fitbit Alta HR, Garmin Fenix 5S, Garmin Vivosmart 3) and three nonwearable (EarlySense Live, ResMed S+, SleepScore Max) devices were tested. Sleep/wake summary and epoch-by-epoch agreement measures were compared with PSG. RESULTS: Most devices (Fatigue Science Readiband, Fitbit Alta HR, EarlySense Live, ResMed S+, SleepScore Max) performed as well as or better than actigraphy on sleep/wake performance measures, while the Garmin devices performed worse. Overall, epoch-by-epoch sensitivity was high (all ≥0.93), specificity was low-to-medium (0.18-0.54), sleep stage comparisons were mixed, and devices tended to perform worse on nights with poorer/disrupted sleep. CONCLUSIONS: Consumer sleep-tracking devices exhibited high performance in detecting sleep, and most performed equivalent to (or better than) actigraphy in detecting wake. Device sleep stage assessments were inconsistent. Findings indicate that many newer sleep-tracking devices demonstrate promising performance for tracking sleep and wake. Devices should be tested in different populations and settings to further examine their wider validity and utility.

Prevalence of Musculoskeletal Injuries Sustained During Marine Corps Recruit Training.

Musculoskeletal injuries cost the U.S. Marine Corps approximately $111 million and 356,000 lost duty days annually. Information identifying the most common types of injuries and events leading to their cause would help target mitigation efforts. The purpose of this effort was to conduct an archival data review of injuries and events leading to injury during recruit training. An archival dataset of Marine recruits from 2011 to 2016 was reviewed and included 43,004 observations from 28,829 unique individuals. Injuries were classified as mild, moderate, and severe and categorized into new overuse, preexisting overuse, and traumatic. Injury classification and categorization were stratified by event in which the injury occurred. The majority of injuries were due to overuse, and the most common types were sprains, strains, iliotibial band syndrome, and stress fractures, which constituted over 40% of all injuries. Conditioning hikes were the primary event leading to injury, with 31% of all injuries occurring during this training; running claimed 12%. Most injuries sustained during basic training comprised sprains and strains. Marines who remained uninjured during basic training outperformed those who reported at least one injury on fitness tests. These results point to enhanced conditioning as a potential entry point to target future intervention efforts.

The Benefit of Mental Skills Training on Performance and Stress Response in Military Personnel.

Mental skills training (MST) has been suggested to reduce stress in civilian and athletic populations, however, whether these techniques and practices transfer to a military population are unknown. Therefore, the purpose of this study was to evaluate two MST programs against a baseline condition, training-as-usual (TAU), during an intense, active-duty, military training environment. Two hundred and three Marines enrolled in the United States Marine Corps' Basic Reconnaissance Course participated in this effort (n = 203; age = 22.7 ± 3.3 years; height = 178 ± 6.35 cm; weight = 97.7 ± 8.3 kg; Mean ± SD). Each Marine was assigned to one of three groups, Mindfulness-Based Mind Fitness Training (MMFT), General Mental Skills Training (GMST), or TAU. Operational and cognitive performance measures, as well as, physiological metrics were obtained across three training phases (phase 1-3). Furthermore, phase 3 was sub-divided into pre-ambush, ambush and post-ambush time points. Significant group × time interactions were found for the total number of errors committed on the sustained attention response task (p = 0.004); as well as, plasma cortisol (p < 0.0001) and insulin-like growth factor-1 (IGF-1; p < 0.0001). There were mixed results between groups on operational performance tasks with the MST groups tending to perform better than TAU the more time participants had with MST instruction. During ambush, the differences among groups were especially pronounced for measures of information processing that one would expect MST to enhance: coordinates recall, plot time, and plot accuracy (p < 0.001), with improvements ranging from 24.7 to 87.9% for the MST conditions when compared to TAU. These data demonstrate that independent of the specific type of MST program, the fundamental characteristics of stress regulation embedded within each MST program may enhance performance and cognitive function during time of heightened stress.

Preparing for Combat Readiness for the Fight: Physical Performance Profile of Female U.S. Marines.

Females have been restricted from serving in direct combat arms' positions for decades. One reason for the exclusion derives from the perceived physical demands of these positions. As a result, many current efforts are directed toward defining the physical demands of combat arms' positions. The purpose of this study was to develop a physical performance and body composition profile of females who could overcome the physical demands of combat tasks that rely primarily on upper body strength. This study is based on an analysis of archival data from 2 separate samples of active-duty female Marines (n = 802), who had been recruited to participate in heavy lifting tasks. These tasks included lifting a heavy machine gun (HMG) lift (cohort 1, n = 423) and Clean and Press lifts (29.5-52.3 kg) (cohort 2, n = 379). To develop the physical performance profile, data from annual physical fitness tests were collected, which included run times, ammunition can lift, 804. Seven-meter (880-yard) movement to contact, and the maneuver under fire. In cohort 1, 65 females (∼15%; n = 423 females) successfully completed HMG; in cohort 2, 33 females (∼9%; n = 379 females) successfully completed another strength task, a Clean and Press of 52.3 kg. In both samples, female Marines who were successful on these tasks also outperformed their unsuccessful counterparts on the annual physical fitness tests. In addition, larger females typically outperformed their smaller counterparts. Females seeking assignment to closed combat arms' positions would thus be well served by targeting upper body strength, while maintaining overall physical fitness.