Panagiotis Matsangas

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).

Comorbid Insomnia and Obstructive Sleep Apnea in Military Personnel: Correlation With Polysomnographic Variables

OBJECTIVES Military personnel undergoing polysomnography are typically diagnosed only with obstructive sleep apnea (OSA). Comorbid insomnia with OSA is a well-established, underappreciated diagnosis. We sought to determine if military personnel with mild OSA met clinical criteria for insomnia and if there was a pattern of polysomnogram (PSG) variables that identified insomnia in these patients. METHODS Retrospective chart review of military personnel with mild OSA; cluster analysis to describe PSG variables. RESULTS 206 personnel assessed, predominately male (96.6%), mean age 36.5 ± 8.14 years, body mass index 30.2 ± 3.66 kg/m(2) and apnea hypopnea index of 8.44 ± 2.92 per hour; 167 (81.1%) met criteria for insomnia. Cluster analysis identified a group of patients (N = 52) with PSG variables of increased wakefulness after sleep onset 77.3 minutes (27.7) (p < 0.001) and decreased sleep efficiency 82.6% (5.82) (p < 0.001) consistent with insomnia. Patients in this group were more likely to meet criteria for insomnia with an odds ratio 5.27 (1.20, 23.1), (p = 0.009). CONCLUSIONS The majority of military personnel with mild OSA meet criteria for insomnia. Roughly one-third of these patients can be identified by a pattern of PSG variables. Recognizing and treating both comorbid insomnia and OSA could improve clinical outcomes.

Yawning as a Behavioral Marker of Mild Motion Sickness and Sopite Syndrome

INTRODUCTION Severe motion sickness is easily identifiable with sufferers showing obvious behavioral signs, including emesis (vomiting). Mild motion sickness and sopite syndrome lack such clear and objective behavioral markers. We postulate that yawning may have the potential to be used in operational settings as such a marker. This study assesses the utility of yawning as a behavioral marker for the identification of soporific effects by investigating the association between yawning and mild motion sickness/sopite syndrome in a controlled environment. METHODS Using a randomized motion-counterbalanced design, we collected yawning and motion sickness data from 39 healthy individuals (34 men and 5 women, ages 27-59 yr) in static and motion conditions. Each individual participated in two 1-h sessions. Each session consisted of six 10-min blocks. Subjects performed a multitasking battery on a head mounted display while seated on the moving platform. The occurrence and severity of symptoms were assessed with the Motion Sickness Assessment Questionnaire (MSAQ). RESULTS Yawning occurred predominantly in the motion condition. All yawners in motion (N = 5) were symptomatic. Compared to nonyawners (MSAQ indices: Total = 14.0, Sopite = 15.0), subjects who yawned in motion demonstrated increased severity of motion sickness and soporific symptoms (MSAQ indices: Total = 17.2, Sopite = 22.4), and reduced multitasking cognitive performance (Composite score: nonyawners = 1348; yawners = 1145). DISCUSSION These results provide evidence that yawning may be a viable behavioral marker to recognize the onset of soporific effects and their concomitant reduction in cognitive performance.

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.

The Effect of Mild Motion Sickness and Sopite Syndrome on Multitasking Cognitive Performance

Objective: In this study, we investigated the effects of mild motion sickness and sopite syndrome on multitasking cognitive performance. Background: Despite knowledge on general motion sickness, little is known about the effect of motion sickness and sopite syndrome on multitasking cognitive performance. Specifically, there is a gap in existing knowledge in the gray area of mild motion sickness. Method: Fifty-one healthy individuals performed a multitasking battery. Three independent groups of participants were exposed to two experimental sessions. Two groups received motion only in the first or the second session, whereas the control group did not receive motion. Measurements of motion sickness, sopite syndrome, alertness, and performance were collected during the experiment. Results: Only during the second session, motion sickness and sopite syndrome had a significant negative association with cognitive performance. Significant performance differences between symptomatic and asymptomatic participants in the second session were identified in composite (9.43%), memory (31.7%), and arithmetic (14.7%) task scores. The results suggest that performance retention between sessions was not affected by mild motion sickness. Conclusion: Multitasking cognitive performance declined even when motion sickness and soporific symptoms were mild. The results also show an order effect. We postulate that the differential effect of session on the association between symptomatology and multitasking performance may be related to the attentional resources allocated to performing the multiple tasks. Results suggest an inverse relationship between motion sickness effects on performance and the cognitive effort focused on performing a task. Application: Even mild motion sickness has potential implications for multitasking operational performance.

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.

Motion-induced interruptions and postural equilibrium in linear lateral accelerations

This study assesses lateral tipping motion-induced interruptions (MIIs) in a simulated motion environment. The objective is to revisit MII occurrence and sway motion relationship by focusing on the frequency and acceleration of the lateral motion stimulus. Results verify that MIIs increase with increasing peak sway acceleration, but the effect of sway frequency is not as clear as that of acceleration. Complex multidirectional motions create more tipping MIIs than unidirectional motion. Research should incorporate acceleration, frequency and motion complexity as factors influencing MII occurrence. To describe a temporary loss of balance without tipping, the term ‘probable’ MII is introduced. This term fills the gap between the theoretical definition and a human-centred perception of an MII where loss of balance is not a binary phenomenon. The ‘probable’ MIIs were 16–67% more common than the ‘definite’ MIIs. The developed mathematical model of MII occurrence versus sway acceleration (amplitude, frequency) approximated the observed MIIs with less than 9% difference. Practitioner Summary: Motion-induced interruptions (MIIs) are important for operational readiness at sea. The rigid body model to predict MIIs does not include the effect of frequency of motion and lacks a human-centred approach. This study identifies that frequency and motion complexity are associated with MII occurrence and proposes a human-oriented extension of the existing MII definition.

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.

A Comparative Analysis of Sleep Disordered Breathing in Active Duty Service Members with and without Combat-Related Posttraumatic Stress Disorder.

STUDY OBJECTIVES Posttraumatic stress disorder (PTSD) and obstructive sleep apnea (OSA) are frequently co-occurring illnesses. The purpose of this study was to determine whether comorbid PTSD/OSA is associated with increased PTSD symptoms or decreased OSA severity compared to PTSD or OSA alone in recently deployed Active Duty Service Members (ADSM). METHODS Cross-sectional observational study of ADSM who returned from combat within 24 months. Participants underwent an attended diagnostic polysomnogram and were assessed for PTSD, depression, combat exposure severity, sleepiness, and sleep quality with validated clinical instruments. RESULTS Our study included 109 military personnel who returned from a combat deployment within 24 months with a mean age of 34.3 ± 8.23 and BMI of 30.8 ± 3.99. Twenty-four participants had PTSD/OSA, 68 had OSA, and 17 had PTSD. Mean PTSD Checklist- Military Version (PCL-M) scores were 62.0 ± 8.95, 60.5 ± 4.73, and 32.5 ± 8.95 in PTSD/OSA, PTSD, and OSA, respectively. The mean AHI was 16.9 ± 15.0, 18.9 ± 17.0, and 1.73 ± 1.3 for those with PTSD/OSA, OSA, and PTSD. PTSD symptoms and OSA severity in military personnel with comorbid PTSD/OSA were not significantly different from those with PTSD or OSA alone. On multivariate analysis, BMI was a significant predictor of OSA (OR, 1.21; 95% CI, 1.04-1.44) and age trended towards significance. Depression, but not OSA severity, was associated with PTSD symptoms. CONCLUSIONS Following recent combat exposure, comorbid PTSD/OSA is not associated with increased PTSD symptoms or decreased severity of OSA. Early evaluation after traumatic exposure for comorbid OSA is indicated in PTSD patients with sleep complaints given the high co-occurrence and adverse clinical implications.

Nightmares in United States Military Personnel With Sleep Disturbances

STUDY OBJECTIVES Sleep disturbances are common in United States military personnel. Despite their exposure to combat and trauma, little is known about nightmares in this population. The purpose of this study was to describe the prevalence and associated clinical and polysomnographic characteristics of nightmares in United States military personnel with sleep disturbances. METHODS Retrospective review of 500 active duty United States military personnel who underwent a sleep medicine evaluation and polysomnography at our sleep center. The Pittsburgh Sleep Quality Index and the Pittsburgh Sleep Quality Index-Addendum were used to characterize clinically significant nightmares. Subjective and objective sleep attributes were compared between groups. RESULTS At least weekly nightmares were present in 31.2%; yet, only 3.9% reported nightmares as a reason for evaluation. Trauma-related nightmares occurred in 60% of those patients with nightmares. Patients with nightmares had increased sleep onset latency (SOL) and rapid eye movement (REM) sleep latency (mean SOL/REM sleep latency 16.6/145 minutes, P = .02 and P = .01 respectively) compared to those without (mean SOL/REM sleep latency 12.5/126 minutes). The comorbid disorders of depression (P ≤ .01, relative risk [RR] 3.55 [95% CI, 2.52-4.98]), anxiety (P ≤ .01, RR 2.57 [95% CI, 1.93-3.44]), posttraumatic stress disorder (P ≤ .01, RR 5.11 [95% CI, 3.43-7.62]), and insomnia (P ≤ .01, RR 1.59 [95% CI, 1.42-1.79]) were all associated with nightmares. CONCLUSIONS Clinically significant nightmares are highly prevalent in United States military personnel with sleep disturbances. Nightmares are associated with both subjective and objective sleep disturbances and are frequently comorbid with other sleep and mental health disorders. COMMENTARY A commentary on this article appears in this issue on page 303.