title: Sleepiness in obstructive sleep apnea: a harbinger of impaired cardiac function?
abstract: OBJECTIVE
  Daytime sleepiness is a common clinical presentation in both obstructive sleep apnea (OSA) and cardiovascular diseases. The purpose of this study was to assess the relationship between degree of subjective daytime sleepiness and cardiac performance in patients with obstructive sleep apnea.
  
  
  METHODS
  Observational study.
  
  
  METHODS
  General Clinical Research Center.
  
  
  METHODS
  The study sample was comprised of 86 patients (68 men and 18 women) with an average age of 47 years. All were suspected of having obstructive sleep apnea and underwent confirmatory diagnostic polysomnography (respiratory disturbance index > or = 15).
  
  
  RESULTS
  Stroke volume and cardiac output were measured using impedance cardiography and corrected for body surface area to yield stroke index and cardiac index. Daytime sleepiness was quantified using the Epworth Sleepiness Scale. A higher Epworth Sleepiness Scale score, suggesting more daytime sleepiness, was significantly related to lower stroke index and cardiac index. In multiple regression analyses, the relationships of Epworth Sleepiness Scale score with both stroke index and cardiac index were significant (p < .05), even after controlling for age, sex, ethnicity, respiratory disturbance index, and mean sleep oxygen saturation.
  
  
  CONCLUSIONS
  These results suggest that daytime sleepiness is independently associated with decreases in cardiac function as assessed by impedance cardiography in patients with obstructive sleep apnea.
authors.affiliation: Department of Neuropsychiatry, Kyunggi Provincial Hospital for the Elderly, Kyunggi-do, South Korea.
authors.forename: Jong-Bae
authors.initials: JB
authors.lastname: Choi
authors.forename: Richard
authors.initials: R
authors.lastname: Nelesen
authors.forename: José S
authors.initials: JS
authors.lastname: Loredo
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Mills
authors.forename: Sonia
authors.initials: S
authors.lastname: Ancoli-Israel
authors.forename: Michael G
authors.initials: MG
authors.lastname: Ziegler
authors.forename: Joel E
authors.initials: JE
authors.lastname: Dimsdale
mesh_terms: D002307:Cardiography, Impedance; D002318:Cardiovascular Diseases / Q000175:diagnosis / Q000453:epidemiology* / Q000503:physiopathology*; D006970:Disorders of Excessive Somnolence / Q000175:diagnosis / Q000453:epidemiology*; D004562:Electrocardiography; D004569:Electroencephalography; D004585:Electrooculography; D005260:Female; D006333:Heart Failure / Q000175:diagnosis / Q000453:epidemiology; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000175:diagnosis / Q000453:epidemiology; D017286:Polysomnography; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000453:epidemiology*