Accidents related to sleepiness: review of medical causes and prevention with special reference to Switzerland.

Sleepiness is a major cause of traffic accidents. Our purpose was to review determinants of accidents related to sleepiness and measures to prevent them. We performed a systematic literature review on the topic and studied official accident statistics and legislation regarding medical driving ability in Switzerland. In 1997, 79,178 road traffic accidents, each causing bodily injury or property damage in excess of 500 Swiss francs, occurred in Switzerland. According to official statistics, sleepiness accounted for only 1% of identified causes. However, scientific studies performed in other countries suggest that sleepiness is a contributing factor in up to 30% of traffic accidents. Causes of hypersomnolence are sleep restriction, sleep disturbance by external environmental factors, inappropriate sleep hygiene, and sleep disorders. Several reports suggest an increased crash rate in patients with obstructive sleep apnoea syndrome. At our clinic, every sixth sleep apnoea patient reports sleepiness-related driving problems which resulted in traffic accidents in one third of them. Long monotonous motorway drives, late night, early morning and late afternoon hours are associated with an increased crash rate. Drivers with excessive sleepiness should not drive until the cause of hypersomnolence is determined and treated appropriately. Medical assessment of driving ability in patients with sleep disorders involves a specific history including standardised questionnaires, sleep studies and vigilance tests. Swiss legislation authorizes physicians to report sleepy drivers to the authorities if they are thought to represent an accident risk for themselves or others. We conclude that sleepiness is a common but under-recognised cause of traffic accidents. Enhancing awareness of the problem in the public, early recognition and treatment of sleep disorders, and counselling of drivers with excessive sleepiness may contribute to prevention.