Published by Australian Academy of Science
Driver fatigue – an accident waiting to happen Box 2 | Sleep disorders

Narcolepsy is a rare sleeping disorder with some obvious potential hazards for drivers. Sufferers commonly have 'sleep attacks' in which they fall asleep without warning, often in inappropriate settings and even after a good sleep the night before. The sleep episode lasts for anywhere between a few seconds and an hour and often features the rapid-eye-movement (REM) stage of sleep. Other possible effects of the disorder include hallucinations, temporary paralysis on waking, and cataplexy, which is the loss of muscle control in emotional situations. It appears to be genetically based and can be treated with stimulants and anti-depressants.

Obstructive sleep apnoea is more common than narcolepsy, affecting perhaps 5 per cent of the population. It is characterised by the restriction of a person's airflow during sleep, caused by the closure of the upper airway. People with sleep apnoea receive inadequate quantities of oxygen while asleep, causing them to wake frequently and thus to have a fractured and less restful sleep. This in turn means that sufferers are commonly tired during the day and more prone to symptoms of fatigue, including 'microsleeps', which are sleep episodes in inappropriate settings that last a few seconds. Several factors contribute to sleep apnoea, including facial structure (ie, the narrowness of the throat), obesity and the loss of muscle tone with ageing. Symptoms may be made worse by the consumption of alcohol and tobacco.

Related site

• Medical standards – sleep disorders (National Road Transport Commisssion (Australia)

Other boxes

Box 1. Circadian rhythms at the molecular level