The aim of the proposed project is to study the effect of CPAP withdrawal on subjective sleepiness in OSA patients using CPAP for less than 4h/night on average. We hypothesize that two-week CPAP withdrawal in patients with 3-4h/night use will lead to a return of OSA-related symptoms. This trial will better establish the minimum level of CPAP adherence which could generally be regarded as effective in reducing OSA-related symptoms.