Obstructive sleep apnea (OSA) is a common disease, which affects 4% middle-aged men and 2% women. Daytime sleepiness is one of the symptoms of OSA which drive patients to seek medical help. Sleepiness in OSA has been reported to be raised by microarousal, altered sleep structure and somnogenic cytokine and modifications in body metabolism. The assessments of daytime sleepiness included objective measures, like multiple sleep latency test and subjective measures, like Epworth sleepiness scale (ESS).