title: Monitoring sound to quantify snoring and sleep apnea severity using a smartphone: proof of concept.
abstract: OBJECTIVE
  Habitual snoring is a prevalent condition that is not only a marker of obstructive sleep apnea (OSA) but can also lead to vascular risk. However, it is not easy to check snoring status at home. We attempted to develop a snoring sound monitor consisting of a smartphone alone, which is aimed to quantify snoring and OSA severity.
  
  
  METHODS
  The subjects included 50 patients who underwent diagnostic polysomnography (PSG), of which the data of 10 patients were used for developing the program and that of 40 patients were used for validating the program. A smartphone was attached to the anterior chest wall over the sternum. It acquired ambient sound from the built-in microphone and analyzed it using a fast Fourier transform on a real-time basis.
  
  
  RESULTS
  Snoring time measured by the smartphone highly correlated with snoring time measured by PSG (r = 0.93). The top 1 percentile value of sound pressure level (L1) determined by the smartphone correlated with the ambient sound L1 during sleep determined by PSG (r = 0.92). Moreover, the respiratory disturbance index estimated by the smartphone (smart-RDI) highly correlated with the apnea-hypopnea index (AHI) obtained by PSG (r = 0.94). The diagnostic sensitivity and specificity of the smart-RDI for diagnosing OSA (AHI ≥ 15) were 0.70 and 0.94, respectively.
  
  
  CONCLUSIONS
  A smartphone can be used for effectively monitoring snoring and OSA in a controlled laboratory setting. Use of this technology in a noisy home environment remains unproven, and further investigation is needed.
authors.affiliation: Sleep Disorders Center, Fukuoka National Hospital, Fukuoka City, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nakano
authors.affiliation: Sleep Disorders Center, Fukuoka National Hospital, Fukuoka City, Japan.
authors.forename: Kenji
authors.initials: K
authors.lastname: Hirayama
authors.affiliation: Sleep Disorders Center, Fukuoka National Hospital, Fukuoka City, Japan.
authors.forename: Yumiko
authors.initials: Y
authors.lastname: Sadamitsu
authors.affiliation: Sleep Disorders Center, Fukuoka National Hospital, Fukuoka City, Japan.
authors.forename: Ayaka
authors.initials: A
authors.lastname: Toshimitsu
authors.affiliation: Sleep Disorders Center, Fukuoka National Hospital, Fukuoka City, Japan.
authors.forename: Hisayuki
authors.initials: H
authors.lastname: Fujita
authors.affiliation: Sleep Disorders Center, Fukuoka National Hospital, Fukuoka City, Japan.
authors.forename: Shizue
authors.initials: S
authors.lastname: Shin
authors.affiliation: Department of Public Health, Ehime University Graduate School of Medicine, Shitsukawa, Toon, Ehime, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Tanigawa
mesh_terms: D006801:Humans; D063731:Mobile Applications; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis*
keywords: Snoring; home monitoring; obstructive sleep apnea; smartphone