Aviation-related Causes of Sleep Disruption

Due to the strong relationship between the sleep patterns and the circadian rhythms, any factors that disrupt the circadian rhythms would cause the sleep disruption.

Jet Lag

Jet lag is caused by undergoing a rapid time-zone transition (Waterhouse, 2005[10]). When an individual travels from one time zone to another in a short time, his/her internal circadian rhythm and the new time zone will be mismatched which results in the situation of circadian desynchronosis (Benca, 2012[2] and Campbell, 2002[5]). The severity of the problem depends on the number of time zones crossed (Bayer, 2001[3]). The short-term effects of jet lag include the inability to initiate and consolidate sleep, a reduction in overall sleep duration, and a reduction of REM sleep and increase of NREM sleep (Costa, 1999[6] and Mallis, 2010[9]). These effects usually last for few days because the circadian system resynchronizes slowly to the zeitgebers of the destination time zone (Campbell, 2002[5] and Graeber, 1988[8]). Since a cycle of normal circadian rhythm is a little bit more than 24 hours, eastward travel requires a longer period of adjustment than westward travel across equivalent time zones because of the circadian rhythm tends to cope with the phase delay (Benca, 2012[2] and Costa, 1999[6]).

Working on Shift

Shift workers may be required to work during their normal sleep hours and sleep during normal waking hours (Benca, 2012[2]). Due to the internal and external desynchronosis, the circadian cycle has to be adjusted to the new schedule after moving to a new shift (Caldwell, 2006[4] and Campbell, 2002[5]). These adjustments include changing the normal sleep-wake pattern and adjusting the body functions, to satisfy the demands of working when the shift workers should sleep and sleep when they should awake (Costa, 1999[6]). However, before being adapted to the new schedule, the quantity and quality of sleep would both decrease (Costa, 1999[6]). Morning shift workers usually have lesser hours of sleep due to the early wakeup, which also causes a reduction of REM sleep (Costa, 1999[6]). In addition, daytime sleep is often shortened, not only due to the inability to sleep resulting from the desynchronosis, but also because of the unfavorable daytime environmental disturbances, such as ringing telephones and traffic noises (Bayer, 2001[3] and Benca, 2012[2]).

Psychological Stress

Psychological stress is commonly resulted from the environmental demands in workplaces, such as downsizing, tight deadlines, long working hours, and heavy workload (Caldwell, 2006[4] and Ewing, 2003[7]). Such stressful conditions would decrease the quality of sleep as a result of the increased tension and difficulties in initiating or maintaining sleep (Akerstedt, 1987[1]). The sleep patterns would also be disrupted temporarily, in terms of intensified REM sleep, reduced total sleep time, reduced time of deep sleep and increased number of awakenings during sleep, until the stressful situation is soothed (Akerstedt, 1987[1] and Caldwell, 2006[4]).

References
1. Akerstedt, T. (1987). “Sleep and Stress.” In Peter, J. H., Podszus, T., and Wichert, P. Sleep Related Disorders and Internal Diseases. Germany: Springer-Verlag Berlin Heidelberg. p. 183-191.
2. Benca, R. M. (2012). Sleep Disorders: The Clinician’s Guide to Diagnosis and Management. New York, USA: Oxford University Press Inc. p.1-138.
3. Bayer, L. (2001). Sleep Disorders. USA: Chelsea House Publishers. p. 21-76.
4. Caldwell, J. L. (2006). “Physiology of Sleep and Wakefulness, Sleep Disorders, and the Effects on Aircrew.” In Rainford, D. J., and Gradwell, D. P. Ernsting’s Aviation Medicine. London: Hodder Education. p. 257-272.
5. Campbell, R. D., and Bagshaw, M. (2002). Human Performance and Limitations in Aviation. UK: Blackwell Science Ltd. p. 170-177.
6. Costa, G. (1999). “Fatigue and Biological Rhythms.” In Garland, D. J., Wise, J. A., and Hopkin, V. D. Handbook of Aviation Human Factors. London: Lawrence Erlbaum Associates. p. 235-256.
7. Ewing, R. L. (2003). Aviation Medicine and other Human Factors for Pilots with Assessment Modules. Christchurch, New Zealead: Old Sausage Publishers Limited. p. 132 - 141.
8. Graeber, R.G. (1988). “Aircrew Fatigue and Circadian Rhythmicity.” In Wiener, Earl L., David C. Nagel. Human Factors in Aviation. USA: Elsevier Science. p. 305-344.
9. Mallis, M. M., Bank, S., and Dinges, D. F. (2010). “Aircrew Fatigue, Sleep Need and Circadian Rhythmicity.” In Salas, E., and Maurino, D. Human Factors in Aviation. Amsterdam: Elsevier Inc. p.401-436.
10. Waterhouse, J., Nevill, A., Finnegan, J., Williams, P., Edwards ,B., Kao, S. Y., and Reilly, T. (2005). Further Assessment of the Relationship between Jet Lag and some of its Symptoms. Chronobiology International, 22(1), p. 121–136.

Want to know more?

1. Circadian Desynchronisation - Jet Lag
2. Stress in Aviation


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