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Section B – What is Fatigue?

The information in this section is provided to assist Senators and Members with their duty under the WHS Act to acquire, and keep up to date, knowledge of work health and safety matters that affect their workplace, including fatigue. It is also provided to assist MOP(S) Act employees to recognise and monitor their own levels of fatigue and to take steps to manage them.


Fatigue is physical and/or mental exhaustion that can be triggered by stress, medication, overwork, or mental or physical illness.

Symptoms of fatigue

Symptoms of fatigue vary but may include blurred vision, difficulty keeping eyes open, head nodding, drowsy feeling, irritability, falling asleep at work, micro sleeps, and feeling tired after sleep.

Effects of fatigue

Immediate effects

The health and safety consequences of fatigue include:

  • slowed reaction time;
  • poor coordination;
  • poor concentration;
  • poor communication;
  • high error rates;
  • reduced vigilance; and
  • reduced judgement and decision-making ability.

Longer-term effects

Longer-term health effects of fatigue include increased risks of:

  • heart disease;
  • diabetes;
  • hypertension;
  • gastrointestinal disorders;
  • lower fertility;
  • anxiety and/or depression.

Causes of Fatigue

Fatigue may be caused by factors including:

  • sleep loss;
  • long periods awake (greater than 17 consecutive hours);
  • inadequate sleep (less than 7-8 hours each night);
  • poor quality sleep; and
  • sustained mental or physical effort;
  • disruptions to circadian rhythms.

The body’s states of sleep and awakeness are regulated by the circadian clock, also known as the body clock. The body clock monitors the amount of light that the body is exposed to. As it gets darker towards the end of the day the brain begins to release a hormone called melatonin which prompts the body to fall asleep. Melatonin levels in the body remain high overnight and begin to decrease as morning approaches. This cycle is known as the circadian rhythm. A disruption to the circadian rhythm, such as working during the night, may put a person at risk of developing fatigue, even when they appear to be having adequate amounts of quality sleep.

Last updated: 06 November 2019