Fatigue in Aviation: Safety Risks, Preventive Strategies and Pharmacological Interventions

Abstract

Fatigue poses an important safety risk to civil and military aviation. In addition to decreasing performance in-flight (chronic) fatigue has negative long-term health effects. Possible causes of fatigue include sleep loss, extended time awake, circadian phase irregularities and work load. Despite regulations limiting flight time and enabling optimal rostering, fatigue cannot be prevented completely. Especially in military operations, where limits may be extended due to operational necessities, it is impossible to rely solely on regulations to prevent fatigue. Fatigue management, consisting of preventive strategies and operational countermeasures, such as pre-flight naps and pharmaceuticals that either promote adequate sleep (hypnotics or chronobiotics) or enhance performance (stimulants), may be required to mitigate fatigue in challenging (military) aviation operations. This review describes the pathophysiology, epidemiology and effects of fatigue and its impact on aviation, as well as several aspects of fatigue management and recommendations for future research in this field.

Effects of modafinil and caffeine on night-time vigilance of air force crewmembers: A randomized controlled trial

“…Our findings are in line with the literature, although previous studies investigated the effects of caffeine and modafinil after longer periods of sustained wakefulness (Killgore et al, 2008; Wesensten et al, 2005; Wingelaar-Jagt et al, 2021). Modafinil sustains flight performance and mood state during continuous wakefulness when tested during simulated or in-flight operations, while the results for caffeine were mixed and inconclusive in these studies (Ehlert and Wilson, 2021).…”

“…Moreover, sleep-related factors were not considered in this study. Sleep deprivation and also an extended period of wakefulness may negatively affect performance (Wingelaar-Jagt et al, 2021). To best reflect circumstances of operational military aviation, the participants were not imposed with bedtimes or waking times; therefore, the time since the last sleeping period and the duration of that sleeping period differed between subjects.…”

“…Regulations limiting flight times and suggesting optimal rosters have been implemented by aviation authorities (EASA, 2014; Federal Aviation Administration, 2012). Although these cannot completely prevent fatigue, they provide a framework to manage fatigue (Wingelaar-Jagt et al, 2021). However, the introduction of these regulations in the Royal Netherlands Air Force (RNLAF) is complicated by the variety of aircrafts available and the types of operations performed.…”

“…Although its exact mechanism of action remains undetermined, it is thought to exert a stimulating effect by altering the levels of several neurotransmitters, including serotonin, noradrenalin, dopamine, and gamma-aminobutyric acid (Battleday and Brem, 2015; Kim, 2012). It has a longer T max (2–4 h) and T 1/2 (12–15 h) than caffeine (30–120 min and 4–6 h, respectively) (Robertson and Hellriegel, 2003; Wingelaar-Jagt et al, 2021). Evaluations of the efficacies of pharmaceutical agents showed that modafinil is a promising fatigue countermeasure.…”

Increased Serum Levels of Proinflammatory Cytokines Are Accompanied by Fatigue in Military T-6A Texan II Instructor Pilots

“…Sleep loss is considered the primary cause of fatigue in aviators ( Caldwell et al, 2009 ; Gore et al, 2010 ; Caldwell et al, 2019 ; Morris et al, 2020 ; Wilson et al, 2020 ; Wingelaar-Jagt et al, 2021 ). However, multiple experimental, observational, and medical studies have identified biochemical mechanisms promoting the onset and maintenance of fatigue as well as sleepiness ( Raison et al, 2006 ; Raison et al, 2009 ; Dantzer et al, 2014 ).…”