title: Impaired functional capacity predicts mortality in patients with obstructive sleep apnea.
abstract: BACKGROUND
  Obstructive sleep apnea (OSA) is associated with increased mortality, for which impaired functional capacity (IFC) has been established as a surrogate. We sought to assess whether IFC is associated with increased mortality in patients with OSA and whether IFC is predictive of increased mortality after accounting for coronary artery disease.
  
  
  METHODS
  Patients with OSA who underwent both polysomnography testing and exercise stress echocardiogram were selected. Records were reviewed retrospectively for demographics, comorbidities, stress echocardiographic parameters, and polysomnography data. Univariable and multivariable logistic regression analysis was used to evaluate the association between IFC and overall mortality. We then evaluated the variables associated with IFC in the overall population and in the subgroup with normal Duke treadmill score (DTS).
  
  
  RESULTS
  In our cohort, 404 (26%) patients had IFC. The best predictors of IFC were female sex, history of smoking, ejection fraction less than 55, increased body mass index, presence of comorbidities, abnormal exercise echocardiogram, abnormal heart rate recovery, and abnormal DTS. Compared with those without IFC, patients with IFC were 5.1 times more likely to die (odds ratio [OR], 5.1; 95% confidence interval [CI], 2.5-10.5; P < 0.0001) by univariate analysis and 2.7 times more likely to die (OR, 2.7; 95% CI, 1.2-6.1; P = 0.02) by multivariate analysis, when accounting for heart rate recovery, DTS, and sleep apnea severity. Among those without coronary artery disease, patients with IFC were at significantly increased risk of mortality (OR, 4.3; 95% CI, 1.35-13.79; P = 0.0088) compared with those with preserved functional capacity.
  
  
  CONCLUSIONS
  In our OSA population, IFC was a strong predictor of increased mortality. Among those with normal DTS, IFC identified a cohort at increased risk of mortality.
authors.affiliation: 1 Heart and Vascular Institute.
authors.forename: Shiraz A
authors.initials: SA
authors.lastname: Nisar
authors.forename: Raghunandan
authors.initials: R
authors.lastname: Muppidi
authors.forename: Sumit
authors.initials: S
authors.lastname: Duggal
authors.forename: Adrian V
authors.initials: AV
authors.lastname: Hernandez
authors.forename: Vidyasagar
authors.initials: V
authors.lastname: Kalahasti
authors.forename: Wael
authors.initials: W
authors.lastname: Jaber
authors.forename: Omar A
authors.initials: OA
authors.lastname: Minai
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000704:Analysis of Variance; D016022:Case-Control Studies; D002423:Cause of Death; D016009:Chi-Square Distribution; D003324:Coronary Artery Disease / Q000175:diagnosis / Q000401:mortality*; D025401:Echocardiography, Stress; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D017286:Polysomnography / Q000379:methods; D011237:Predictive Value of Tests; D012129:Respiratory Function Tests; D012189:Retrospective Studies; D012737:Sex Factors; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000401:mortality*; D016019:Survival Analysis; D013990:Tidal Volume
keywords: coronary artery disease; impaired functional capacity; mortality; polysomnography; sleep apnea