Narcolepsy is a rare sleeping disorder affecting 1:2000 persons . Sufferers commonly have 'sleep attacks' in which they fall asleep without warning. This often occurs in inappropriate settings and even after a good night sleep. Narcolepsy has obvious potential hazards for drivers (http://www.science.org.au/nova/074/074key.htm).
The sleep episode can last between a few seconds and an hour. Possible side-effects of the disorder include hallucinations, temporary paralysis on waking, and cataplexy (loss of muscle control in emotional situations). This disorder is genetically based and can be treated with stimulants and anti-depressants.
Legislation concerning narcolepsy and fitness to drive differs among EU countries. For example in the UK, sufferers from narcolepsy are not usually permitted to drive. In many other EU countries specific legislation in regard to narcolepsy is lacking.
Obstructing sleep apnoea 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, resulting in a fractured and less restful sleep. Sufferers are commonly tired during the day and more prone to symptoms of fatigue, including 'micro-sleeps' (sleep episodes in inappropriate settings that last a few seconds). Symptoms of sleep apnoea may be made worse by the consumption of alcohol and tobacco.
Epidemiological data indicate that at least 5 million patients suffer from sleep apnoea throughout Europe . This is about 0, 7% of the European population. Of course, registered patients are an underestimation of all persons who suffer from this handicap. It is estimated that perhaps as much as 5% of a population may actually be affected by it (see: http://www.science.org.au/nova/074/074key.htm)
In Europe, there are no uniformly accepted regulations concerning driving licensing and sleep apnoea. Many national European licensing make no specific mention of sleep apnoea or excessive daytime sleepiness . Sassani et al  concluded that treating all US drivers suffering from obstructive sleep apnoea syndrome with (CPAP) therapy has a favourable cost-benefit ratio. This would cost 3, 2 US billion (dollars) and save 980 lives and 11, 1 US billion in collision costs annually in the USA.