The Maintenance of Wakefulness Test (MWT) is widely used to objectively assess sleepiness and make safety-related decisions and Epworth Sleepiness Scale (ESS) is the most used scale used to assess subjective sleepiness in sleep medicine.

Besides Obstructive Sleep Apnea measures are rapidly evolving and conventional measures such as apnea-hypopnea index (AHI) and oxygen desaturation index (ODI) are increasingly being supplemented by measures of hypoxia such as hypoxic burden.

Residual AHI in treated OSA have limited predictive value for objective sleepiness. Therefore it seems particularly relevant to identify other predictors of both subjective and objective sleepiness.

This study aims at studying the influence of hypoxic burden as measure of both subjective or objective sleepiness.

We hypothesize that impaired nocturnal oxygenation might influence brain functioning during wakefulness and result in sleepiness as assessed by ESS and MWT.

Inclusion Criteria:

• OSA hospitalised to undergo both polysomnography (PSG) and the 40-min MWT in the Center for Sleep Medicine and Respiratory Disease, Lyon Academic Hospital from September 2017 to March 2020.

Exclusion Criteria:

• - age <18 years
• refusal to participate in the study
• diagnosis of central disorder of hypersomnolence
• missing data on the MWT
• Epworth Sleepiness Scale (ESS)
• apnea-hypopnea index (AHI).

This study involves consecutive adult patients referred to the Center for Sleep and Respiratory Medicine for performance of MCT from September 2017 to January 2020.