We examined subjective symptoms ( snoring intensity , frequency , witnessed apnea , and daytime sleepiness ) and objective snoring and respiratory parameters ( snoring duration [ proportion of sleep while snoring louder than 50 dB ] , snoring loudness , apnea-hypopnea index , respiratory disturbance index , minimum arterial oxygen saturation , and oxygen desaturation index4 % ) at 3 to 6 months after surgery .