title: Phenotypes of patients with mild to moderate obstructive sleep apnoea as confirmed by cluster analysis.
abstract: OBJECTIVE
  Patients with OSA manifest different patterns of disease. However, this heterogeneity is more evident in patients with mild-moderate OSA than in those with severe disease and a high total AHI. We hypothesized that mild-moderate OSA can be categorized into discreet disease phenotypes, and the aim of this study was to comprehensively describe the pattern of OSA phenotypes through the use of cluster analysis techniques.
  
  
  METHODS
  The data for 1184 consecutive patients, collected over 24 months, was analysed. Patients with a total AHI of 5-30/h were categorized according to the sleep stage and position in which they were predominantly affected. This categorization was compared with one in which patients were grouped using a K-means clustering technique with log linear modelling and cross-tabulation.
  
  
  RESULTS
  Patients with mild-moderate OSA can be categorized according to polysomnographic parameters. This clinical categorization was validated by comparison with a categorization in which patients were grouped by unsupervised K-means cluster analysis. The clinical groups identified were: (i) rapid eye movement (REM) predominant OSA, 44.6%; (ii) non-REM predominant OSA, 18.9%; (iii) supine predominant OSA, 61.9%; and (iv) intermittent OSA, 12.4%. Patients categorized as having both REM and supine predominant OSA showed characteristics of both the REM predominant and supine predominant OSA groups.
  
  
  CONCLUSIONS
  Patients with mild-moderate OSA show different polysomnographic phenotypes. This approach to categorization more appropriately reflects disease heterogeneity and the likely multiple pathophysiological processes involved in OSA.
authors.affiliation: Department of Respiratory and Sleep Medicine, Monash Medical Centre, Melbourne, Australia.
authors.forename: Simon A
authors.initials: SA
authors.lastname: Joosten
authors.forename: Kais
authors.initials: K
authors.lastname: Hamza
authors.forename: Scott
authors.initials: S
authors.lastname: Sands
authors.forename: Anthony
authors.initials: A
authors.lastname: Turton
authors.forename: Philip
authors.initials: P
authors.lastname: Berger
authors.forename: Garun
authors.initials: G
authors.lastname: Hamilton
mesh_terms: D000063:Accidents, Traffic / Q000517:prevention & control*; D017677:Age Distribution; D001835:Body Weight; D002318:Cardiovascular Diseases / Q000209:etiology / Q000235:genetics*; D016000:Cluster Analysis; D005260:Female; D006801:Humans; D006973:Hypertension / Q000209:etiology / Q000235:genetics*; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D017286:Polysomnography; D012720:Severity of Illness Index; D012727:Sex Characteristics; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000175:diagnosis / Q000235:genetics*; D012894:Sleep Stages; D016683:Supine Position