Produced by the Royal College of Physicians of Edinburgh and Royal College of Physicians and Surgeons of Glasgow

Sleep apnoea and road accidents

  • Professor N Douglas, Respiratory Consultant, Royal Infirmary of Edinburgh, Edinburgh, Scotland


Sleep apnoea is a significantly under-diagnosed condition which causes symptoms of sleepiness and difficulty in concentrating. It can also cause drivers to fall asleep at the wheel. Prof Neil Douglas provides an overview of the link between sleep apnoea and road traffic accidents.

Key Points

  • Obstructive sleep apnoea/hypopnoea syndrome (OSAHS) is caused by airway obstructions during sleep. It disrupts sleep and results in sleepiness, impaired thought processes and delayed reaction times during the day.
  • Falling asleep while driving is common. About a fifth of men in the general population have reported falling asleep while driving, but a third of those with OSAHS have had an accident or a near accident due to falling asleep.
  • Drunk normal subjects perform better than sober OSAHS patients on a driving simulator.
  • Treatment for OSAHS can return driving performance to normal.

Declaration of interests: Chair, International Medical Advisory Board of ResMed (a US/Australian company which makes CPAP units to test OSAHS). Professor Douglas's Department has previously received research funding from ResMed.

Sleepiness and difficulty concentrating are the dominant symptoms of the obstructive sleep apnoea/hypopnoea syndrome (OSAHS). These symptoms are worst in monotonous situations such as driving on major roads and motorways, consequently drivers with OSAHS have an increased risk of road accidents. As OSAHS affects 1-4% of drivers this is a significant public health issue. This was highlighted in a recent report by a working party of the European Respiratory Society.

Although OSAHS patients tend to under-report driving difficulties, over one-third report having had an accident or near accident due to falling asleep at the wheel.1 Falling asleep while driving is also common in the general population, with 19% of men admitting to doing so in one study.2

Objective evidence indicates raised accident rates in sleep apnoeics. A study of all drivers presenting to an accident department showed that those with frequent apnoeas were six times more likely to be road accident drivers than subjects without sleep apnoea.3 Retrospective studies in patients prior to the diagnosis of OSAHS being established suggest a three-fold risk of road accidents compared to other drivers.4

There is also convincing evidence from vigilance tasks and driving simulators5 that driv