title: Clinical and polysomnographic data of positional sleep apnea and its predictors.
abstract: BACKGROUND
  In Asian population, facial structure may contribute to the primary pathophysiology of obstructive sleep apnea (OSA). We hypothesized that sleep position may have more effect on OSA in Asians compared to the Western population. If this hypothesis is accurate, positional therapy will have a major impact on treatment of OSA among Asians.
  
  
  METHODS
  We reviewed 263 polysomnographic studies from our laboratory from January 1, 2010 to June 30, 2010. Criteria for positional and non-positional OSA were (1) supine respiratory disturbance index (RDI)/non-supine RDI ≥2 and total RDI ≥5 and (2) supine RDI/non-supine RDI <2 and total RDI ≥5, respectively. We aimed to determine the difference in baseline characteristics, polysomnographic findings, and predictors for positional OSA.
  
  
  RESULTS
  We found 144 patients diagnosed with OSA (RDI ≥5), and 96 patients met the criteria for positional OSA (67%), in which in almost half of these patients (47%), RDI was normalized (RDI < 5) in non-supine position. Snoring frequency were significantly lower among positional OSA and OSA was less severe indicated by lower RDI and arousal index, higher mean and nadir oxygen saturation, and higher %NREM3. We also found that low snoring frequency (less than 20% of total sleep time) was a significant predictor for positional OSA (odd ratio of 3.27; p = 0.011), contrarily to low mean oxygen saturation (<95%) which was found to be a negative predictor (odd ratio of 0.31; p = 0.009). Among OSA patients, low RDI (<15) was a significant predictor for normalization of RDI in non-supine position (odd ratio of 8.77; p = < 0.001), contrarily to low mean oxygen saturation (<95%) which was also found to be a negative predictor (odd ratio of 0.13; p = 0.001).
  
  
  CONCLUSIONS
  Positional OSA is very prevalent and noted in almost 70% of our patients. Low snoring frequency was noted to be a positive predictor for positional OSA, contrarily to low mean oxygen saturation which was found to be a negative predictor. These findings are encouraging that positional therapy can be very beneficial as the treatment modality for OSA among Asians.
authors.affiliation: Department of Otolaryngology and Opthalmology, Naresuan University, Phitsanulok, Thailand.
authors.forename: Busarakum
authors.initials: B
authors.lastname: Teerapraipruk
authors.forename: Naricha
authors.initials: N
authors.lastname: Chirakalwasan
authors.forename: Rosalind
authors.initials: R
authors.lastname: Simon
authors.forename: Prakobkiat
authors.initials: P
authors.lastname: Hirunwiwatkul
authors.forename: Nattapong
authors.initials: N
authors.lastname: Jaimchariyatam
authors.forename: Tayard
authors.initials: T
authors.lastname: Desudchit
authors.forename: Natamon
authors.initials: N
authors.lastname: Charakorn
authors.forename: Chaisiri
authors.initials: C
authors.lastname: Wanlapakorn
mesh_terms: D000328:Adult; D000368:Aged; D002508:Cephalometry; D003431:Cross-Cultural Comparison; D003906:Developing Countries; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010100:Oxygen / Q000097:blood; D017286:Polysomnography; D011187:Posture; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology*; D012913:Snoring / Q000175:diagnosis / Q000453:epidemiology / Q000208:ethnology / Q000209:etiology; D013785:Thailand
chemical_list: D010100:Oxygen