Sleepiness and Driving Risk Introduction over the Last 15 Years, Major Epidemiologi- Cal Studies Have Highlighted the Prevalence of Sleepiness and Sleep Disorders

OVER THE LAST 15 YEARS, MAJOR EPIDEMIOLOGICAL STUDIES HAVE HIGHLIGHTED THE PREVALENCE OF SLEEPINESS AND SLEEP DISORDERS AMONG general population.1-3 Sleepiness at the wheel2,4 has been identified as one of the major reasons for highway accidents and fatal crashes. Patients with obstructive sleep apnea syndrome (OSAS) have a much higher risk of accidents than drivers without nocturnal breathing disorders. Sleepiness at the wheel is a key factor in these accidents.5-7 Multiple Sleep Latency Test (MSLT) and Maintenance of Wakefulness Test (MWT) are useful clinical tests for the evaluation of excessive sleepiness. Unfortunately, these tests are timeconsuming and focused on a single day. For patients who suffer from OSAS, the MSLT which quantifies the ability to fall asleep, is not appropriate for the usage suggested by the Task Force of the American Academy of Sleep Medicine (AASM).8 The MWT (which requires the patient to fight against sleepiness in a soporific condition) is considered as a validated, objective measure of the ability to stay awake and is used as an adapted test for daytime evaluation of patients with OSAS. The MWT is a robust, replicable, and suitable test for multicenter studies9; some authors,10 however, have questioned its suitability to evaluate real world performances and/or risks. Very few studies have investigated the relationship between objective measurement of sleepiness (MSLT or MWT scores) and driving performance. Young et al.11 found among the Wisconsin Sleep Cohort a correlation between MSLT scores and driving accidents in male drivers with OSAS. Experimentally, impaired daytime alertness causes an increase in lateral deviations during simulated12-17 and real18-21 driving. Banks et al.22 have recently compared MWT with performance on a driving simulator in healthy sleep deprived volunteers. This was the first evidence of the predictive value of MWT on driving performances. Unfortunately, the simplified MWT (2 trials) used in the study did not correspond to the validated gold standard test (4 trials of 40 minutes), and only healthy individuals were tested. Physicians need to consider their own legal liability in allowing patients with untreated OSAS to drive, and the use of an objective measure of sleepiness could provide a helpful medical tool in this regard. In this study, we decided to test the ability to predict impairment in simulated driving in patients with untreated OSAS using 2 tests: the objective MWT and the subjective Epworth Sleepiness Scale.