Nourizadeh N, et al. - Between August 2012 and September 2013, authors researched the consequence of functional endoscopic sinus surgery (FESS) for nasal polyposis on sleep performance and polysomnographic parameters. They estimated the subjective criteria of sleep quality by the Pittsburgh Sleep Quality Index (PSQI) questionnaire which showed significant improvement, especially in nocturnal awakening. No significant decrease in Apnea-Hypopnea Index (AHI) after surgery was recorded. AHI was reported improved in 7 subjects, deteriorated in 3 cases, and did not change in 1 subject among subjects who had suffered from obstructive sleep apnea. They observed a positive effect on sleep quality due to alteration of other sleep parameters like arousal index following surgery even after insignificant effect of FESS on apnea index.