title: The impact of body posture and sleep stages on sleep apnea severity in adults.
abstract: OBJECTIVE
  Determining the presence and severity of obstructive sleep apnea (OSA) is based on apnea and hypopnea event rates per hour of sleep. Making this determination presents a diagnostic challenge, given that summary metrics do not consider certain factors that influence severity, such as body position and the composition of sleep stages.
  
  
  METHODS
  We retrospectively analyzed 300 consecutive diagnostic PSGs performed at our center to determine the impact of body position and sleep stage on sleep apnea severity.
  
  
  RESULTS
  The median percent of REM sleep was 16% (reduced compared to a normal value of ~25%). The median percent supine sleep was 65%. Fewer than half of PSGs contained > 10 min in each of the 4 possible combinations of REM/NREM and supine/non-supine. Half of patients had > 2-fold worsening of the apnea-hypopnea index (AHI) in REM sleep, and 60% had > 2-fold worsening of AHI while supine. Adjusting for body position had greater impact on the AHI than adjusting for reduced REM%. Misclassification--specifically underestimation of OSA severity--is attributed more commonly to body position (20% to 40%) than to sleep stage (~10%).
  
  
  CONCLUSIONS
  Supine-dominance and REM-dominance commonly contribute to AHI underestimation in single-night PSGs. Misclassification of OSA severity can be mitigated in a patient-specific manner by appropriate consideration of these variables. The results have implications for the interpretation of single-night measurements in clinical practice, especially with trends toward home testing devices that may not measure body position or sleep stage.
authors.affiliation: Neurology Department, Massachusetts General Hospital, Boston, MA 02114, USA.
authors.forename: Nathaniel A
authors.initials: NA
authors.lastname: Eiseman
authors.forename: M Brandon
authors.initials: MB
authors.lastname: Westover
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Ellenbogen
authors.forename: Matt T
authors.initials: MT
authors.lastname: Bianchi
mesh_terms: D000328:Adult; D005188:False Negative Reactions; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010641:Phenotype; D017286:Polysomnography; D011187:Posture; D012189:Retrospective Studies; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology; D012894:Sleep Stages; D012895:Sleep, REM; D016683:Supine Position