8.1 Relevance to the driving task
8.1.1 Evidence of crash risk
Studies have shown an increased rate of motor vehicle crashes of between two and seven times that of among 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 > 34) may have a higher rate of crashes than those with a less severe sleep disorder.1
Those with narcolepsy perform worse on simulated driving tasks and are more likely to have vehicle crashes than control subjects.
8.1.2 Impact of treatment on crash risk
Treating obstructive sleep apnoea (OSA) with nasal continuous positive airways pressure (CPAP) has been shown to reduce daytime sleepiness and reduce the risk of crashes to the same level as controls. CPAP has also been shown to improve driving-simulator performance to the same levels as the control group. When used to treat OSA, mandibular advancement splints reduce daytime sleepiness and improve vigilance; however, studies have not been performed to assess whether they reduce motor vehicle crash rates.2,3,4,5