AUSTROADS: Assessing Fitness to Drive

Last year 1,367 Australians were killed on our roads and many tens of thousands seriously injured. The total economic cost of this exceeds $15 billion annually and the accompanying social costs greatly impact on our communities.

While many factors contribute to safety on the road, driver health is an important consideration and drivers must meet certain medical standards to ensure their health status does not increase their crash risk.

Studies have shown an increased rate of motor vehicle crashes, of between two and seven times that of control subjects, in those with sleep apnoea. Studies have also demonstrated increased objectively measured sleepiness while driving (electro-encephalography and eye closure measurements) and impaired driving-simulator performance in people with confirmed sleep apnoea. This performance impairment is similar to that seen due to illegal alcohol impairment or sleep deprivation. Drivers with severe sleep disordered breathing (respiratory disturbance index greater than 34) may have a higher rate of crashes than those with a less severe sleep disorder.

Excessive daytime sleepiness, which manifests itself as a tendency to doze at inappropriate times when intending to stay awake, can arise from many causes and is associated with an increased risk of motor vehicle crashes. It is important to distinguish sleepiness (the tendency to fall asleep) from fatigue or tiredness that is not associated with a tendency to fall asleep. Many chronic illnesses cause fatigue without increased sleepiness.

Until the disorder is investigated, treated effectively and licence status determined, people should be advised to avoid or limit driving if they are sleepy, and not to drive if they are at high risk, particularly in the case of commercial vehicle drivers. High-risk people include:

• those who experience moderate to severe excessive daytime sleepiness (Epworth Sleepiness Scale score of 16 to 24)
• those with a history of frequent self-reported sleepiness while driving and
• those who have had a motor vehicle crash caused by inattention or sleepiness.

People with these high-risk features have a significantly increased risk of sleepiness-related motor vehicle crashes (odds ratio 15.2). These people should be referred to a sleep disorders specialist, particularly in the case of commercial vehicle drivers.