Energy Types of Snoring Sounds in Patients with Obstructive Sleep Apnea Syndrome: A Preliminary Observation

Background: Annoying snore is the principle symptom and problem in obstructive sleep apnea syndrome (OSAS). However, investigation has been hampered by the complex snoring sound analyses. Objective: This study was aimed to investigate the energy types of the full-night snoring sounds in patients with OSAS. Patients and Method: Twenty male OSAS patients underwent snoring sound recording throughout 6 hours of in-lab overnight polysomnogragphy. Snoring sounds were processed and analyzed by a new sound analytic program, named as Snore Map (R). We transformed the 6-hour snoring sound power spectra into the energy spectrum and classified it as snore map type 1 (monosyllabic low-frequency snore), type 2 (duplex low-& mid-frequency snore), type 3 (duplex low-& high-frequency snore), and type 4 (triplex low-, mid-, & high-frequency snore). The interrator and test-retest reliabilities of snore map typing were assessed. The snore map types and their associations among demographic data, subjective snoring questionnaires, and polysomnographic parameters were explored. Results: The interrator reliability of snore map typing were almost perfect (kappa = 0.87) and the test-retest reliability was high (r = 0.71). The snore map type was proportional to the body mass index (r = 0.63, P = 0.003) and neck circumference (r = 0.52, P = 0.018). Snore map types were unrelated to subjective snoring questionnaire scores (All P > 0.05). After adjustment for body mass index and neck circumference, snore map type 3-4 was significantly associated with severity of OSAS (r = 0.52, P = 0.026). Conclusions: Snore map typing of a full-night energy spectrum is feasible and reliable. The presence of a higher snore map type is a warning sign of severe OSAS and indicated priority OSAS management. Future studies are warranted to evaluate whether snore map type can be used to discriminate OSAS from primary snoring and whether it is affected by OSAS management.