Objectives: To determine continuous positive airway pressure (CPAP) treatment compliance and reversal of excessive daytime sleepiness in patients with mild OSA.Background: CPAP therapy is the most widely accepted and used intervention in patients with a diagnosis of obstructive sleep apnea (OSA). There are, however, no widely accepted protocols to help guide the rational use of CPAP therapy. Patients with mild OSA (respiratory event index (REI) >5 or </=25) represent a subset of the OSA population where CPAP implementation needs to be evaluated.Methods: This is a retrospective study of 740 consecutive patients evaluated for sleep apnea in 1996. Mild OSA was documented in 241 patients, of whom, 41 opted for CPAP therapy. Implementation of CPAP treatment included an education session and an overnight clinical polysomnography (CPSG) for titration purposes. Patients returned for follow-ups after 1 week and 1 year of CPAP use. During each appointment, compliance and response to treatment were evaluated.Results: Of the initial 41 patients nine were lost to follow-up, 16 discontinued CPAP use during the first week, and 16 were still using CPAP after 1 year. For the 16 still using CPAP after one year, hours of use the first week was correlated to hours of use the first year (r=0.81). Patients using CPAP more than 4 h/night experienced a marked improvement in daytime sleepiness after 1 year (P<0.01).Conclusions: Patients with mild OSA showed a high rate of CPAP discontinuation. Those patients who manifested good compliance during the first week of treatment continued using CPAP for the entire first year. These patients experienced improved alertness during the day. A 1 week trial on CPAP therapy is warranted to identify patients who benefit from this form of therapy.