Scientific consensus is that sleep is an unconscious state essential for life, and that humans spend approximately eight of every 24 hours, or roughly one third of their lives, sleeping. This observation suggests that sleep has a major physiological function, and that insufficient or altered sleeping patterns can lead to relatively significant changes to this function, with major physiological consequences, in particular with regards to awareness.
Numerous dramatic occupational accidents testify to this:
- In April 2010, a Chinese bulk carrier, the Shen Neng, ran aground causing one of Australia’s worst ever environmental catastrophes. The Australian Transport Safety Bureau (ATSB) found that fatigue affecting the captain and the first officer was the main cause of the grounding. Specifically, the captain had only had two and a half hours’ sleep during the two days preceding the accident.
- The Chernobyl disaster occurred at 1:23 am. Reduced vigilance due to the late hour was considered by investigators to be a significant factor in the disaster.
- The accidental meltdown of the Three Mile Island nuclear reactor in 1979 occurred at 4 am. As at Chernobyl, the lack of vigilance was a contributing factor.
- The explosion of the pesticides plant at Bhopal in 1984, which officially killed 3,500 people, occurred at 12:30 am.
- The Exxon Valdez ran aground in Alaska in 1989 at midnight.
Human fatigue was a contributing factor in all of these disasters. But we must bear in mind that numerous occupational and domestic accidents are caused directly or indirectly by fatigue, though not with the same dramatic consequences and thus not widely reported.
Generally speaking, the scientific literature notes that sleep deprivation symptoms often include memory, cognitive and executive functions, changes of mood, and motor control. At the same time as these central effects, limited sleep affects other functions including the energy metabolism and the endocrine and immune systems. Sleep deprivation thus results in complex changes in many body functions that directly affect occupational well-being.
In terms of public health, a report from Dr Giordanella to the French Minister of Health in 2006 emphasised the need to take sleep into proper account as a factor in good health and occupational safety. There also seems to be broad agreement that all populations and all age groups are affected, and are thus potentially exposed to the harmful and even dangerous effects of acute or chronic sleep deprivation.