Impact of sleep deprivation and obstructive sleep apnea syndrome on daytime vigilance and driving performance: a laboratory perspective.

INTRODUCTION: To study the impact of sleepiness, a well-established cause of car accidents, on driving ability, we designed a 30-min monotonous simulated driving task. MATERIALS AND METHODS: Our simulated driving task encompasses both primary vehicle control (standard deviation of lane position, crash occurrence) and secondary tasks (type and reaction times to divided attention tasks). Driving simulator data were correlated to subjective (state/trait) and objective (MSLT/MWT) sleepiness measures in healthy subjects undergoing sleep deprivation (SD) and in obstructive sleep apnea (OSAS) patients. RESULTS: SD induced severe sleepiness during nighttime, when state sleepiness increased while primary vehicle control ability worsened. After SD, driving ability decreased and was inversely correlated to subjective and objective sleepiness at MSLT. OSAS patients driving ability was well correlated to objective sleepiness, with inverse correlation to sleep propensity at the MSLT and even more strict relation with the ability to maintain wakefulness at the MWT. CONCLUSIONS: Sleepiness worsens driving ability in healthy subjects after SD and in OSAS patients. Driving ability correlates with subjective and objective sleepiness measures, in particular to the ability to maintain wakefulness.