John A. Caldwell

The U.S. Army Special Forces Assessment and Selection course (SFAS) is an extremely stressful, physically and mentally challenging 19–20 days long selection procedure. Only 30%–40% of soldiers who volunteer for it complete it. The purpose of SFAS is to identify soldiers who can complete 1–2 years of physically and mentally challenging training for the Special Forces and be successful Special Forces soldiers thereafter. This study examined association of pre‐course self‐reported mood state and sleep quality and quantity with subsequent success or failure at SFAS. Data from 780 male soldiers collected in 2015–2017 were analysed. Prior to SFAS, the Profile of Mood States (POMS), Dimension of Anger Reactivity (DAR), Duke University Social Support Questionnaire (Duke‐SSQ), General Anxiety Disorder and Depression inventories (GAD‐7), and Pittsburgh Sleep Quality Index (PSQI) were administered. Group differences among these variables and their ability to predict selection versus non‐selection were assessed. There were significant differences in pre‐SFAS mood and sleep in selected versus non‐selected volunteers. Selected candidates reported more positive mood (POMS vigour, friendliness), less negative mood (POMS depression, anger, fatigue, confusion), less anger (DAR), and less social support (Duke‐SSQ). Selected candidates reported longer and higher quality sleep (PSQI) than non‐selected soldiers. These differences were not sufficient to serve as an accurate predictive model based on logistic regression, as the best‐fit model accounted for 4.9% of the variance. In conclusion, there were differences in pre‐course mood state and sleep between those who succeeded or failed a stressful course that selects individuals for elite military training and service, but they were not of sufficient strength to predict individual success of failure.

INTRODUCTION: Insomnia and sleep apnea (SA) can have adverse effects on operating aircraft. This study examined trends in insomnia and SA incidence rates in U.S. military aviators from 2006–2022 and examined associated demographic and operational factors. METHODS: Data on incidence cases of outpatient insomnia and SA, aviator demographics, and operational factors were obtained from the Defense Medical Epidemiological Database, a comprehensive online archive of military medical data. Insomnia and SA cases were identified using specific International Classification of Diseases codes. RESULTS: For the entire military aviator population ( N = 331,992 ± 1649, mean ± SD) overall rates of insomnia and SA were 10.2 and 24.9 cases/1000 person-years, respectively. Compared to the entire U.S. military nonaviator population, aviators had lower incidence of insomnia, but higher incidence of SA. Insomnia rates among aviators increased up to 2015 and declined afterwards, while SA rate generally rose over the period. Insomnia and SA rates among aviators increased with age, were higher among those of black and other nonwhite races, were highest among Army personnel (compared to other services) and were highest among helicopter pilots (compared to fixed-wing aircraft pilots). Insomnia rates were similar among male and female aviators, but SA rates were higher among men. DISCUSSION: These data indicate that insomnia and SA are prevalent within the military aviation population; however, the incidence of insomnia appears to have fallen as the tempo of military operations has decreased while the incidence of SA continues on an upward trajectory, possibly associated with the growing problem of obesity. Caldwell JA, Knapik JJ. Trends and factors associated with insomnia and sleep apnea in U.S. military aviators, 2006–2022 . Aerosp Med Hum Perform. 2025; 96(1):23–30.

To synthesize original articles exploring the effects of sleep restriction on cognitive performance specifically for Elite Cognitive Performers, i.e. those who engage in cognitively demanding tasks with critical or safety-critical outcomes in their occupation or area of expertise. Backward snowballing techniques, gray literature searches, and traditional database searches (Embase, MEDLINE, Web of Science, Google Scholar, PSYCinfo, and SportDiscus) were used to obtain relevant articles. A quality assessment was performed, and the risk of training effects was considered. Results were narratively synthesized. Fourteen articles fit the criteria. Cognitive outcomes were divided into three categories defined by whether cognitive demands were “low-salience,” “high-salience stable,” or “high-salience flexible.” Low-salience tests (i.e. psychomotor vigilance tasks & serial reaction tests), mainly requiring vigilance and rudimentary attentional capacities, were sensitive to sleep restriction, however, this did not necessarily translate to significant performance deficits on low-salience occupation-specific task performance. High-salience cognitive outcomes were typically unaffected unless when cognitive flexibility was required. Sleep restriction is of particular concern to occupations whereby individuals perform (1) simple, low-salience tasks or (2) high-salience tasks with demands on the flexible allocation of attention and working memory, with critical or safety-critical outcomes.

Sleep is a vital component of preparation, performance and recovery for a Super Rugby game. The purpose of this study was to quantify sleep behaviours and alertness of professional rugby union players during training and a game. Thirty-six rugby union players from a Super Rugby team wore a wrist-activity device (Readiband™) to measure sleep for 3 days before, 3 days after and on the night of an evening game. Players were separated into those selected to play the game (n = 23) and those who were not (n = 13). Alertness was assessed for all training and game times using bio-mathematical modelling. Alertness measures ≤90% were considered to reflect impaired reaction time. Those selected to play in the game progressively increased sleep duration over the nights prior to the game (by 92 min p ≤ 0.05) by delaying wake time. Players went to bed later after the game (02:20 ± 114 min vs 22:57 ± 60 min; p ≤ 0.001) which resulted in decreased sleep duration on game night compared to pre-game nights (296 ± 179 min vs 459 ± 78 min; p ≤ 0.05). Four players did not achieve any sleep on game night. Sleep duration appeared to be truncated by early morning training sessions (before 08:00) on the second and third mornings after the game. Alertness was >90% for all training and game times for all players. In conclusion, in the days leading into a Super Rugby game, players delay morning time at wake and consequently increase sleep duration with post-game sleep reduced in some.

Fatigue from inadequate sleep has been a problem for many years, possibly beginning with the advent of the electric light bulb when the ability to be active at night as well as during the day became possible. Modern transportation technology contributed further when air travel enabled time-zone transitions at a rate that severely outpaced the body clock’s physiological rate of adaptation. In recent years, the problem of sleepiness/fatigue has been a focus in aviation due to the safety hazards associated with impaired operator alertness.

Summary Pilot fatigue is a significant, but often under-reported problem in both civilian and military aviation operations. Although estimates vary, official statistics indicate that fatigue is involved in at least 4-8% of aviation mishaps, and surveys of pilots and aircrew members reveal that fatigue is an important concern throughout today's 24/7 flight operations. Regulatory efforts aimed at limiting flight hours and ensuring at least minimal periods of crew rest have to some extent mitigated fatigue-related difficulties in the cockpit, but it is clear that much remains to be done about this insidious threat to air safety. Scheduling factors, sleep deprivation, circadian disruptions, and extended duty periods continue to challenge the alertness and performance levels of both short-haul and long-haul pilots and crews. Solutions for these problems are not straightforward, but they can be developed through the cooperative efforts of scientists, regulators, managers, and the pilots themselves. Over the past 20 years, scientific understanding of human sleep, fatigue, and circadian rhythms has expanded considerably. The thorough integration of this new knowledge into modern crew-resource management practices will facilitate the establishment of optimal crew scheduling routines and the implementation of valid aviation fatigue countermeasures.