Your brain will get slow and sluggish as you become fatigued.

The longer you stay awake, the greater the toll fatigue takes on your ability to function. One place where your performance degrades is in your cognitive functions. Here are a few interesting findings:

  • If you stay up for 17 hours, your hand-eye coordination will be similar to how you perform after drinking enough alcohol to bring your blood alcohol level up to 0.05%[1]
  • If you stay up for 18 hours, your ability to problem solve, maintain vigilance and communicate will decrease by 30%, add another 30 hours of wakefulness and you will decrease another 30%[2]
  • Fatigue will also make your brain slow and sluggish. This means that it will take you longer to react to important information[3]
  • Fatigue can also make it difficult for you to process visual information from the peripheral retina[4] and to subsequently react to it.


[1] Dawson, D., & Reid, K. (1997). Fatigue, alcohol and performance impairment. Nature, 388, 235.

[2]  Angus, R., Pigeau, R., & Heslegrave, R. (1992). Sustained operation studies: From the field to the laboratory. In C. Stampi (Ed.) Why We Nap: Evolution, Chronobiology, and Functions of Polyphasic and Ultrashort Sleep. Boston: Birkhäuser.

[3] See for examples:

  • Belenky, G., Wesensten, N., Thorne, D., Thomas M., Sing, H., Redmond, D., Russo, M., & Balkin, T. (2003). Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: A sleep dose-response study. Journal of Sleep Research, 12(1), 1-12.
  • Dinges, D. (1992). Probing the limits of functional capability: The effects of sleep loss on short –duration tasks. In Broughton, R. (Ed.) Sleep, Arousal, and Performance. Boston: Birkhäuser.
  • Galy, E., Mélan, C., & Cariou, M. (2008). Investigation of task performance variations according to task requirements and alertness across the 24-h day in shift workers. Ergonomics, 51(9), 1338-1351.
  • Van Dongen, H., Maislin, G., Mullington J., & Dinges, D., (2003). The cumulative cost of additional wakefulness: Dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep, 26(2), 117-126.
  • Wylie, C. & Mackie, R. (1988). Stress and sonar operator performance: Enhancing target detection performance by means of signal injection and feedback. Goleta, CA: Essex Corporation, Human Factors Research Division.

[4] Haworth, N., Heffernan, C., & Horne, E. (1989). Fatigue in truck accidents. Report No. 3. Victoria: Monash University Accident Research Centre.