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universidade lusófona

Rescue the Fatigue! An ecological study in the Portuguese Air Force operational

Principal investigator

Catarina N. Matias (CIDEFES) and Maria João Valamatos (FMH - CIPER)




To evaluate the physiological, psychological, and cognitive impact of a single mission of fifteen days in the islands, in Portuguese Air Force Militaries. Also, to analyze and evaluate the impact of cumulative effects of 1 year of service in missions and its physical and mental repercussions.


In 2020, the European Aviation Safety Agency (EASA) defined the state of well-being and fitness for air functions as the main safety issue for both civil aviation and military aviation1. In the last two decades, fatigue has been identified as the most likely cause of aviation accidents (~21 to 23% of aviation accidents)2-5.

Fatigue can be multifaceted, with mental and physical fatigue being the ones that most frequently affect performance in aviation 6-10. This is also recognized by the International Civil Aviation Organization (ICAO, 2020) when defining fatigue as “A physiological state of reduced mental or physical performance, such as a consequence of sleep deprivation, prolonged wakefulness, circadian cycle phase and/or workload (mental and physical) (…)”11.

In the context of military aviation, mental fatigue and drowsiness have been mentioned as the most important form of fatigue12,13, which can compromise the success of missions. It is known that some characteristics of sleep, i.e., quality and duration, are essential for accelerating recovery processes and combating mental fatigue5 and that food also plays a crucial factor in physical recovery, where macronutrients are indispensable for the correct functioning of the body and consequently physical and mental performance14,15.

Nevertheless, factors such as sleep and food may change during a mission due to the adjustment of the mission place and a natural change in the circadian rhythms due to be on call for 24/716.

Literature has shown that fatigue can have long-term effects on health17-20. Some authors report that fatigue may reduce work capacity and may be associated with depression and anxiety21-23. However, it should be noted that, in addition to the mental and psychological fatigue resulting from the mission, there is also a substantial physical demand, resulting from rescue operations.

Air Force crews deployed for missions are multidisciplinary teams composed of elements with highly specific tasks, requiring high levels of experience, efficiency, and effectiveness, where precision, physical robustness, and mental acuity are essential. In rescue missions, five soldiers are typically involved with different functions: pilot-in-command, co-pilot, systems operator, salvage rescuer, and aeronautical nurse. The physical and mental demands are clearly differentiated between each operating element. For example, in the case of system operators or lifeguards, the physical demand is greater when compared to pilots in command, co-pilots, and aeronautical nurses. In the latter, focus, fine motor skills and mental acuity acquire greater importance. These characteristics naturally lead to a high inter-individual dependence, where small individual errors can compromise the team’s task and consequently the success of the mission, reinforcing the need to correctly evaluate the fatigue state in the military due to a single mission or a set of missions’ occurrence over a year.

1 European Union Aviation Safety Agency (EASA) (2020). “Annual Safety Review 2020”. (Cologne, Germany: European Union Aviation Safety Agency)

2 Caldwell, J. A. (2012). Crew schedules, sleep deprivation, and aviation performance. Curr. Dir. Psychol. Sci. 21, 85–89. doi: 10.1177/0963721411435842.

3 Gaines, A. R., Morris, M. B., and Gunzelmann, G. (2020). Fatigue-related Aviation mishaps. Aerosp. Med. Hum. Perform. 91, 440–447. doi: 10.3357/ AMHP.5515.2020

4 Marcus, J. H., and Rosekind, M. R. (2017). Fatigue in transportation: NTSB investigations and safety recommendations. Inj. Prev. 23, 232–238. doi: 10.1136/injuryprev-2015-041791.

5 Wingelaar-Jagt YQ, Wingelaar TT, Riedel WJ and Ramaekers JG (2021) Fatigue in Aviation: Safety Risks, Preventive Strategies and Pharmacological Interventions. Front. Physiol. 12:712628. doi: 10.3389/fphys.2021.712628

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7 Reis, C., Mestre, C., and Canhao, H. (2013). Prevalence of fatigue in a group of airline pilots. Aviat. Space Environ. Med. 84, 828–833. doi: 10.3357/ ASEM.3548.2013

8 Aljurf, T. M., Olaish, A. H., and BaHammam, A. S. (2018). Assessment of sleepiness, fatigue, and depression among gulf cooperation council commercial airline pilots. Sleep Breath. 22, 411–419. doi: 10.1007/s11325-017-1565-7.

9 Goel, N., Rao, H., Durmer, J. S., and Dinges, D. F. (2009). Neurocognitive consequences of sleep deprivation. Semin. Neurol. 29, 320–339. doi: 10.1055/ s-0029-1237117

10 Gregory, K. B., Winn, W., Johnson, K., and Rosekind, M. R. (2010). Pilot fatigue survey: exploring fatigue factors in air medical operations. Air Med. J. 29, 309–319. doi: 10.1016/j.amj.2010.07.002

11 International Civil Aviation Organization (ICAO) (2020). “Manual for the Oversight of Fatigue Management Approaches (Doc 9966)”. (Montreal, Canada: International Civil Aviation Organization).

12 O’Hagan, A. D., Issartel, J., McGinley, E., and Warrington, G. (2018). A pilot study exploring the effects of sleep deprivation on analogue measures of pilot competencies. Aerosp. Med. Hum. Perform. 89, 609–615. doi: 10.3357/ AMHP.5056.2018

13 Williamson, A., Lombardi, D. A., Folkard, S., Stutts, J., Courtney, T. K., and Connor, J. L. (2011). The link between fatigue and safety. Accid. Anal. Prev. 43, 498–515. doi: 10.1016/j.aap.2009.11.011

14 Kerksick, C. M., Arent, S., Schoenfeld, B. J., Stout, J. R., Campbell, B., Wilborn, C. D., Taylor, L., Kalman, D., Smith-Ryan, A. E., Kreider, R. B., Willoughby, D., Arciero, P. J., VanDusseldorp, T. A., Ormsbee, M. J., Wildman, R., Greenwood, M., Ziegenfuss, T. N., Aragon, A. A., & Antonio, J. (2017). International society of sports nutrition position stand: nutrient timing. Journal of the International Society of Sports Nutrition, 14, 33.

15 Oliver, L. S., Sullivan, J. P., Russell, S., Peake, J. M., Nicholson, M., McNulty, C., & Kelly, V. G. (2021). Effects of Nutritional Interventions on Accuracy and Reaction Time with Relevance to Mental Fatigue in Sporting, Military, and Aerospace Populations: A Systematic Review and Meta-Analysis. International journal of environmental research and public health, 19(1), 307.

16 Kelley, A. M., Feltman, K. A., and Curry, I. P. (2018). A survey of fatigue in army aviators. Aerosp. Med. Hum. Perform. 89, 464–468. doi: 10.3357/ AMHP.5044.2018

17 Good, C. H., Brager, A. J., Capaldi, V. F., and Mysliwiec, V. (2020). Sleep in the United States military. Neuropsychopharmacology 45, 176–191. doi: 10.1038/ s41386-019-0431-7

18 Straif, K., Baan, R., Grosse, Y., Secretan, B., El Ghissassi, F., Bouvard, V., et al. (2007). Carcinogenicity of shift-work, painting, and fire-fighting. Lancet Oncol. 8, 1065–1066. doi: 10.1016/S1470-2045(07)70373-X

19 Goel, N., Basner, M., Rao, H., and Dinges, D. F. (2013). Circadian rhythms, sleep deprivation, and human performance. Prog. Mol. Biol. Transl. Sci. 119, 155–190. doi: 10.1016/b978-0-12-396971-2.00007-5

20 International Agency for Research on Cancer (IARC) (2019). “IARC Monographs Meeting 124: Night Shift Work (4–11 June 2019)”. (Lyon, France: World Health Organization).

21 O’Hagan, A. D., Issartel, J., Fletcher, R., and Warrington, G. (2016). Duty hours and incidents in flight among commercial airline pilots. Int. J. Occup. Saf. Ergon. 22, 165–172. doi: 10.1080/10803548.2016.1146441

22 Pasha, T., and Stokes, P. R. A. (2018). Reflecting on the Germanwings disaster: A systematic review of depression and suicide in commercial airline pilots. Front. Psych. 9 :86. doi : 10.3389/fpsyt.2018.00086

23 Pellegrino, P., and Marqueze, E. C. (2019). Aspects of work and sleep associated with work ability in regular aviation pilots. Rev. Saude Publica 53:16. doi: 10.11606/s1518-8787.2019053000345