Purpose:Obstructive sleep apnea (OSA) is a sleep disorder characterized by repeated nocturnal desaturation and sleep fragmentation. OSA can result in decreased daytime alertness and neurocognitive dysfunction. Although continuous positive airway pressure (CPAP) has been shown to improve daytime sleepiness in patients with OSA, the effect of CPAP on cognitive function is still controversial. Methods:A total of 45 patients with OSA were enrolled in this study. All patients completed three cognitive tasks (the psychomotor vigilance task, the Eriksen flanker task and the Stroop task) and two questionnaires (the Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS)) to measure cognitive function and daytime sleepiness before and after 3 months of standard CPAP treatment. Results:The majority of patients showed significant improvements in ESS and PSQI scores after three months of treatment. In addition, CPAP therapy resulted in a decrease in reaction time and error rate in incongruent trials in the flanker task. In the Stroop task, CPAP treatment resulted in an increase in accuracy rate and decreases in error rate and omission rate in congruent trials and an increase in accuracy rate and decreases in reaction time, error rate and omission rate in incongruent trials. There were no significant changes in performance on the psychomotor vigilance task test. Conclusions:A three-month CPAP therapy resulted in significant improvement in daytime sleepiness and increased executive function but did not have an effect on psychomotor vigilance in patients with OSA.