Daytime Sleepiness and Driving Performance in Patients with Obstructive Sleep Apnea: Comparison of the MSLT, the MWT, and a Simulated Driving Task

2009 Sleep  
sleepiness (EDS). It affects from 2% to 4.4% (women) and from 4% to 11% (men) of the middle-aged population according to current diagnostic criteria and epidemiologic data. 1,2 OSAS is associated with increased mortality, acting as an independent risk factor for heart and cerebrovascular events and for the proneness to traffic crashes. 3-5 Drivers with OSAS are at 2 to 3 times increased risk of being involved in motor vehicle crashes, but neither disease severity nor sleepiness is consistently
more » ... orrelated with crash risk. 6 Sleepiness is a multidimensional entity that integrates qualitatively different facets: the sleep propensity in active or passive situations and the subjective perceptual component. 7 The intensity of sleepiness could range from the normal expression of the need for sleep (ie, innate behavior) to the main symptom of severe medical and neurologic disturbances. The measurement of sleepiness reflects its complexity, with several objective and subjective tools available. Objectively, the Multiple Sleep Latency Test (MSLT) and the Maintenance of Wakefulness Test (MWT) are the gold standards for the detection of EDS in the clinical practice of sleep medicine. 1, 8 The MSLT provides a measure of sleep propensity in a quiet appropriate situation (lying on a bed in a dark room), assuming that the more the sleep latency is reduced, the greater the subject's need for sleep. In the MSLT setting, sleepiness is equivalent to the ability to sleep, disregarding the potential occurrence of high "sleep ability" even in absence of any confirmatory sign of sleepiness (ie, in normal conditions). 9 The MWT evaluates subjects' ability to maintain wakefulness in a quiet boring, situation (sitting on a comfortable chair in a semidark room). In the MWT setting, sleepiness corresponds to alertness, in terms of capability to stay awake in a soporific (but somewhat uncommon for everyday life) condition. Moreover, the reported wide variability of MSLT and MWT sleep latencies in the normal population clearly overlaps with findings in medical disorders characterized by EDS. 10-13 Normative data include a mean sleep latency (to the first epoch of sleep) of 10.4 (± 4.3) minutes on the MSLT and of 30.4 (± 11.2) minutes on the MWT. Therefore, the range of normal falls between 1.8 and 19 minutes and between 8 and 40 minutes, respectively for MSLT and MWT (using the 2 SD from the mean to identify 95% of the normal values). 8,10-13 According to international criteria, the MSLT and MWT are the objective tools exploring different features of sleepiness. They are recommended for different clinical purposes from diagnosis confirmation (eg, MSLT) to the evaluation of therapeutic efficacy (eg, MWT), in association with subjective trait sleepiness assessment using the Epworth Sleepiness Scale (ESS). 1, 8, 14 Driving is a complex psychomotor task that requires an adequate level of alertness to interact efficiently with the road environment but, in parallel, involves several perceptual, motor, and cognitive processes. The recent awareness of sleepiness-related crashes is mirrored by the medicolegal aspects concerning fitness to drive and consequent physicians' referral of patients with medical conditions. 15 Concerning individual ability to drive safely, sleepiness-related crashes can result from falling asleep while driving or from more subtle phenomena, such as inattention or study objectives: To test the reliability of a driving-simulation test for the objective measurement of daytime alertness compared with the Multiple Sleep Latency Test (MSLT) and with the Maintenance of Wakefulness Test (MWT), and to test the ability to drive safely, in comparison with on-road history, in the clinical setting of untreated severe obstructive sleep apnea. Design: N/A. setting: Sleep laboratory. Patients or Participants: Twenty-four patients with severe obstructive sleep apnea and reported daytime sleepiness varying in severity (as measured by the Epworth Sleepiness Scale). interventions: N/A. Measurements and results: Patients underwent MSLT and MWT coupled with 4 sessions of driving-simulation test on 2 different days randomly distributed 1 week apart. Simulated-driving performance (in terms of lane-position variability and crash occurrence) was correlated with sleep latency on the MSLT and more significantly on the MWT, showing a predictive validity toward the detection of sleepy versus alert patients with obstructive sleep apnea. In addition, patients reporting excessive daytime sleepiness or a history of car crashes showed poorer performances on the driving simulator. conclusions: A simulated driving test is a suitable tool for objective measurement of daytime alertness in patients with obstructive sleep apnea. Further studies are needed to clarify the association between simulated-driving performance and on-road crash risk of patients with sleep disordered breathing. sleepiness and driving performance in patients with obstructive sleep apnea: comparison of the MSLT, the MWT, and a simulated driving task. SLEEP 2009;32(3):382-391.
doi:10.5665/sleep/32.3.382 fatcat:uhwyhtrsmvevznudznusvr5qee