Caffeine is consumed by over 80% of U.S. adults. This review examines the effects caffeine has on cognitive and physical function, since most real-world activities require complex decision making, motor processing and movement. Caffeine exerts its effects by blocking adenosine receptors. Following low (∼40mg or ∼0.5mgkg-1) to moderate (∼300mg or 4mgkg-1) caffeine doses, alertness, vigilance, attention, reaction time and attention improve, but less consistent effects are observed on memory and higher-order executive function, such as judgment and decision making. Effects on physical performance on a vast array of physical performance metrics such as time-to-exhaustion, time-trial, muscle strength and endurance, and high-intensity sprints typical of team sports are evident following doses that exceed about 200mg (∼3mgkg-1). Many occupations, including military, first responders, transport workers and factory shift workers, require optimal physical and cognitive function to ensure success, workplace safety and productivity. In these circumstances, that may include restricted sleep, repeated administration of caffeine is an effective strategy to maintain physical and cognitive capabilities.

Fatigue and workplace sleepiness are consequences of modern industrial society. Fatigue is a complex biological phenomenon that occurs as a function of time awake, time-of-day, workload, health, and off-duty lifestyle. Fatigue is a function of two major biological factors - the homeostatic drive for sleep and circadian rhythm of sleepiness. The greatest cause of fatigue is insufficient or disrupted sleep. Excessive sleepiness in the workplace and on highways is a serious safety hazard, and insufficient or disrupted sleep results in numerous accidents and adverse mental and physical health outcomes. Evidence-based strategies that promote better sleep and optimize work/rest schedules can mitigate the impact of fatigue and sleep loss. Proper nap and sleep scheduling, work breaks, modeling and monitoring tools, fatigue detection technologies, and pharmacological countermeasures can be implemented at home and/or in the workplace to reduce performance and safety hazards. Education about obtaining adequate sleep, the dangers of fatigue in terms of both health and cognitive consequences, and the availability of scientifically-proven sleep-enhancement and alertness-management strategies is essential.

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.

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.