Snoring Sound Intensity and Formant Frequencies by Sleep Position in Patients with Positional Obstructive Sleep Apnea

Abstract

Background and Objectives Snoring is the most common symptom of obstructive sleep apnea (OSA) and is caused by turbulent airflow due to narrowing of the upper airways. In patients with positional OSA, a change in sleep posture from supine to lateral is known to reduce snoring and sleep apnea. This study was performed to compare changes in snoring sound intensity and formant frequencies according to sleep position.Subjects and Method A total of 19 patients (male: 18; female: 1) diagnosed with positional OSA by polysomnography (PSG) were enrolled in this study. The snoring sounds recorded during PSG were analyzed acoustically and compared according to sleep position (i.e., supine vs. lateral).Results Snoring disappeared on changing sleep position in five patients, all of whom had Apnea-Hypopnea Index (AHI) <15. In other patients, the snoring sounds tended to decrease with posture change, and the degree of decrease was inversely proportional to AHI (p=0.015) and respiratory disturbance index (RDI) (p=0.013). Formant frequencies 1, 3, and 4 (F1, F3, and F4, respectively) decreased when sleeping in the lateral position (p=0.02, 0.03, and 0.01, respectively).Conclusion In patients with positional OSA, a change in sleep posture from supine to lateral during sleep reduced the intensity and frequency of snoring sound.