Presently, there isn't any international recommendation to evaluate vigilance in Obstructive Sleep Apnea Syndrome. The French Society of Sleep Research and Medicine (SFRMS) recommend evaluating professional driver with a MWT but no recommendation exists for other patients. After a minimal treatment of 4 weeks, the physician has to evaluate the drowsiness risk of these patients using either an objective test like the MWT or a subjective one. In the university hospital Amiens-Picardie, since the 01/01/2015, every patient with an Obstructive Sleep Apnea Syndrome diagnosed by a polysomnography or a ventilatory polygraphy had a MWT after 4 weeks of treatment. At each time of the evaluation, Epworth Sleepiness Scale, tiredness score of Pichot, and depressive score of Beck are performed.

Inclusion Criteria:

• patients treated by CPAP for Obstructive Sleep Apnea Syndrome

Exclusion Criteria:

• Central Apnea Syndrome
• Central Hypersomnia

all patients more than 18 years treated by CPAP for Obstructive Sleep Apnea Syndrome diagnosed at the Sleep Medicine Unity of the Amiens Hospital having a MWT between the 01/01/15 and 31/12/16 were included. Patients were excluded if they had an Central Apnea Syndrome, Central Hypersomnia, no driving license or if they refused.