Sleep apnoea can lead to daytime sleepiness, which in turn increases the risk of road accidents. In an article to be published in November’s ERJ, German researchers show that a driving simulator could allow easy, objective assessment of the accident risk. They also confirm the potential road safety benefits of the standard treatment provided to sleep apnoea sufferers.

Road accidents are now one of the leading causes of death in developed countries. And, while accusing fingers are rightly being pointed at speed and alcohol, sleepiness at the wheel also plays a significant role, which may be seriously underestimated.

Since daytime sleepiness is one of the main signs of sleep apnoea, sufferers from the condition are thus particularly vulnerable. They are thought to have an accident rate between two and seven times higher than that of the general population.

In view of this, doctors are tending increasingly (and in some countries have an obligation) to make judgements about their apnoeic patients’ safety at the wheel. But how is the risk to be judged objectively, and with what diagnostic tool?
Maritta Orth and her team, of Bergmannsheil University Hospital in Bochum, Germany, recommend a driving simulator, such as the C.A.R.® (Computer Aided Risk Simulator), which was used in the study they publish in November’s ERJ.

Simulator more effective than neuropsychological tests

The German team tested the driving performance of 31 patients with obstructive sleep apnoea. The simulator placed the subjects in monotonous driving conditions for 60 minutes at an average virtual speed of 100 kilometres/hour (62 miles/hour). Various weather conditions (wind, sunshine, rain, snow, etc.) and a range of obstacles (such as animals, pedestrians and other vehicles) were integral to the simulation.

The results obtained by Orth and her colleagues show first of all that, on average, untreated apnoea sufferers experienced 2.7 “accidents” (collisions with other vehicles or pedestrians, veering off the carriageway) in such a driving simulation, with a further 12.4 lapses of concentration. The ERJ study also demonstrates the ineffectiveness of neuropsychological tests or polysomnographic tracing to predict increased accident risk. No correlation could be demonstrated between driving performance and polysomnographic parameters or neuropsychological test results.

Positive airway pressure’s effectiveness confirmed

Most importantly, the German study shows that the usual treatment for sleep apnoea, namely continuous positive airway pressure (CPAP), delivered through a mask worn over the nose and mouth at night, can significantly improve safety behind the wheel.

Orth’s team measured apnoeic subjects’ driving performance before treatment and then two and 42 days after the start of treatment.

The results in November’s ERJ are unambiguous: not only were attention and alertness improved after 42 days’ treatment, as were sleepiness scores and polysomnographic traces; but a safer driving performance could be seen even before the other improvements. The comparative accident rate fell sharply as soon as treatment began (2.7 before the start of CPAP, 1.5 after two days and 0.9 at 42 days).

In parallel to these results, the German team emphasises the qualities of the simulator used in the study, which it found particularly well suited to this type of investigation.

“The C.A.R.® driving simulator is the best tool for comparing obstructive sleep apnoea sufferers’ driving abilities before and under CPAP”, the authors state.
Its scope appears very broad: already tested for multiple sclerosis sufferers, it could be used to assess the road safety implications of many other conditions.
It could also prove useful in evaluating the effect of drug treatments on driving performance.

Title of original article:
Driving simulator and neuropsychological testing in OSAS before and under CPAP therapy

The European Respiratory Journal is the peer-reviewed scientific publication of the European Respiratory Society (more than 7,500 specialists in lung diseases and respiratory medicine in Europe, the United States and Australia).

EUROPEAN RESPIRATORY JOURNAL (ERJ), Vol. 26, No 5
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