The predictors of objective impaired alertness assessed by Maintenance of Wakefulness Tests (MWT) are poorly understood. Identifying such predictors are essential from a clinical point of view and from a pathophysiological perspective, to better understand the determinants of residual Excessive Daytime Sleepiness (EDS) and the complex link between subjective and objective impairments. Also, the objective of this study is to describe psychological but also sociological and professional factors associated with Maintenance of Wakefulness Tests results.