Sleep apnoea and road accidents (page 1 of 2)
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Sleepiness and difficulty concentrating are the dominant symptoms of the obstructive sleep apnoea/hypopnoea syndrome (OSAHS). These symptoms are worst in monotonous situations such as driving on major roads and motorways, consequently drivers with OSAHS have an increased risk of road accidents. As OSAHS affects 1-4% of drivers this is a significant public health issue. This was highlighted in a recent report by a working party of the European Respiratory Society.
Although OSAHS patients tend to under-report driving difficulties, over one-third report having had an accident or near accident due to falling asleep at the wheel.1 Falling asleep while driving is also common in the general population, with 19% of men admitting to doing so in one study.2
Objective evidence indicates raised accident rates in sleep apnoeics. A study of all drivers presenting to an accident department showed that those with frequent apnoeas were six times more likely to be road accident drivers than subjects without sleep apnoea.3 Retrospective studies in patients prior to the diagnosis of OSAHS being established suggest a three-fold risk of road accidents compared to other drivers.4
There is also convincing evidence from vigilance tasks and driving simulators5 that driving performance is impaired in patients with OSAHS. Indeed drunk normal subjects perform better on a driving simulator than sober OSAHS patients.6 Interestingly the impairment is not just limited to periods when patients actually fall asleep; their response is also impaired when they are awake, reflecting impaired vigilance and delayed reaction times.7
Treatment of OSAHS significantly improves driving performance. Prospective studies have found that therapy with continuous positive airway pressure (CPAP) improves OSAHS patients’ performance on driving simulators8,9 and decreases the frequency and severity of road accidents. A recent analysis10 showed that CPAP not only returned OSAHS patients’ accident rates to the population norm, but also that treating 500 patients with CPAP for five years saved £4·9 million when the expenditure on treatment and follow-up were set against the savings on accident related costs. This is in addition to other well documented benefits of CPAP in terms of sleepiness, quality of life, mood, work performance and blood pressure.
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