Drivers should take a break from the wheel if they feel sleepy

Road accidents are one of the leading causes of death in developed countries and sleepiness at the wheel plays a significant role.

People with the medical condition sleep apnoea are particularly prone to dozing off and are thought to have a car accident rate 2-7 times higher others.

The European Respiratory Journal study checked the safety of 31 such drivers.

Drowsy drivers

The simulator placed the subjects in monotonous driving conditions for 60 minutes at an average virtual speed of 100 kilometres/hour or 62 miles/hour.

The drivers also had to navigate through various weather conditions, including wind, sunshine, rain and snow, and avoid collisions with a range of obstacles, such as animals, pedestrians and other vehicles.

They were tested before and they had treatment with a therapy called CPAP, which has been shown to improve daytime wakefulness in people with sleep apnoea.

CPAP stands for continuous positive airway pressure and works by delivering air to the individual while they sleep to help them have a restful night and avoid excessive daytime sleepiness.

Before the treatment the apnoea drivers experienced 2.7 "accidents", which included collisions with other vehicles or pedestrians or veering off the carriageway, and a further 12.4 lapses of concentration in the simulator.

After the CPAP treatment their accident rate fell to less than one and lapses of concentration to 4.9, on average.

When the researchers looked at the results of standard tools used to assess alertness and sleepiness - polysomnography and neuropsychological tests - they found such measures did not predict increased accident risk.

Tiredness can kill

The researchers said: "Driving simulation is a possible benchmark parameter of driving performance in sleep apnoea patients."

In the UK, the Driver and Vehicle Licensing Agency (DVLA) says people with sleep apnoea must not drive unless they have satisfactory control of their symptoms which is confirmed by medical experts.

A spokesman from the DVLA said: "The DVLA already makes medical assessment of drivers with symptomatic sleep disorders, including obstructive sleep apnoea (OSA), and are aware of the benefits of treatment with CPAP for many OSA patients."

To avoid road accidents due to tiredness, government road safety advisors recommend that drivers plan their journey to include a 15-minute break every two hours.

If drivers feel drowsy they should find a safe place to stop. They should not start a long trip if they are already tired and when possible should avoid long trips between midnight and 6am when it is likely that they will feel sleepy anyway.