Inclusion Criteria:  body mass index (BMI) of less than 35kg/m2, age between 35 and 65 years, and diagnosed by laboratory polysomnography with moderate to severe OSA (apnea-hypopnea index, AHI≥20 events/hour of sleep)  Exclusion Criteria:  illiteracy, participants with more than 50% of the respiratory events obtained in the polysomnography exam being central apneas; participants with central AHI>5 events/hour of sleep; participants with sleepiness, measured by the Epworth sleepiness scale≥14; participants with severe otorhinolaryngological diseases that preclude the use of CPAP (severe nasal septum deviation, severe nasal turbinate hypertrophy, marked palatine and/or adenoid hypertrophy); abuse of alcohol or chronic use of psychoactive drugs; participants with decompensated clinical, neurological or psychiatric illness; participants with other sleep disorders; participants who had already undergone previous OSA treatments.