People with sleep apnoea may be more likely to doze off at the wheel of a car, a new study indicates.

Sleep apnoea is a potentially life-threatening condition in which breathing is disrupted during sleep. Symptoms can include feeling tired or drowsy during the daytime, recurrent awakenings during sleep and snoring.

Previous research has suggested that people with the sleep disorder may have an increased risk of being in a road traffic accident. Scientists from the UK decided to look into this further. They carried out two studies involving a driving simulator test.

As part of the first study, 133 people with untreated sleep apnoea and 89 people without the condition took part in a 90km motorway driving simulation. A number of areas were assessed, including their ability to complete the task and their positioning on the road.

The scientists found that those with sleep apnoea were more likely to fail the test. In fact, one in four failed it compared to one in nine of those without the condition. Thirteen of those with the sleep disorder could not complete the task because they fell asleep and veered completely off the motorway.

Those with sleep apnoea also tended to have more unprovoked crashes.

For the second study, 118 people with untreated sleep apnoea and 69 people without the condition also undertook a 90km driving simulation test. They also completed a questionnaire.

The results of the questionnaire revealed that at least one in three people with sleep apnoea had previously nodded off at the wheel of a vehicle. Almost 40% of these went on to fail the simulation test.

In comparison, just one in 10 people without sleep apnoea admitted to previously nodding off at the wheel and none of these failed the simulation test.

"Driving simulators can be a good way of checking the effects that a condition like sleep apnoea can have on driving ability. Our research suggests that people with the condition are more likely to fail the test," commented lead investigator, Dr Mark Elliott, of University Hospital in Leeds.

Details of these findings were presented at the Sleep and Breathing Conference in Berlin, which was organised by the European Respiratory Society and the European Sleep Research Society.