title: Obstructive sleep apnea is associated with impaired exercise capacity: a cross-sectional study.
abstract: OBJECTIVE
  Obstructive sleep apnea (OSA) is associated with increased risk of adverse cardiovascular events. Because cardiopulmonary exercise testing (CPET) aids in prognostic assessment of heart disease, there is rising interest in its utility for cardiovascular risk stratification of patients with OSA. However, the relationship between OSA and exercise capacity is unclear. This study was conducted to test the hypothesis that OSA is associated with impaired exercise capacity.
  
  
  METHODS
  Fifteen subjects with moderate-to-severe OSA (apnea-hypopnea index [AHI] ≥15 events/h) and 19 controls with mild or no OSA (AHI <15 events/h) were enrolled. Subjects underwent standard polysomnography to determine AHI and exclude other sleep disorders. Resting metabolic rate was measured via indirect calorimetry, followed by maximum, symptom-limited CPET. Subjects completed a sleep diary and physical activity questionnaire characterizing behaviors in the week prior to testing.
  
  
  RESULTS
  Percent predicted peak oxygen uptake (V˙O2) was significantly lower in OSA subjects than controls (70.1%±17.5% vs 83.8%±13.9%; p = 0.02). Each 1-unit increase in log-transformed AHI was associated with a decrease in percent predicted peak V˙O2 of 3.20 (95% CI 0.53-5.88; p = 0.02). After adjusting for baseline differences, this association remained significant (p < 0.01). AHI alone explained 16.1% of the variability observed in percent predicted peak V˙O2 (p = 0.02).
  
  
  CONCLUSIONS
  OSA is associated with impaired exercise capacity. Further study is needed to evaluate the utility of CPET for prognostic assessment of patients with OSA.
authors.affiliation: Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors.forename: Jeremy R
authors.initials: JR
authors.lastname: Beitler
authors.affiliation: Department of Neurology, Beth Israel Deaconess Medical Center, Boston, MA.
authors.forename: Karim M
authors.initials: KM
authors.lastname: Awad
authors.affiliation: Division of Sleep Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors.forename: Jessie P
authors.initials: JP
authors.lastname: Bakker
authors.affiliation: Division of Sleep Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors.forename: Bradley A
authors.initials: BA
authors.lastname: Edwards
authors.affiliation: Division of Pulmonary and Critical Care Medicine, University of California, San Diego, San Diego, CA.
authors.forename: Pam
authors.initials: P
authors.lastname: DeYoung
authors.affiliation: Division of Sleep Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors.forename: Ina
authors.initials: I
authors.lastname: Djonlagic
authors.affiliation: Division of Cardiovascular Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Forman
authors.affiliation: Division of Sleep Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA and Arizona Respiratory Center, University of Arizona College of Medicine, Tucson, AZ.
authors.forename: Stuart F
authors.initials: SF
authors.lastname: Quan
authors.affiliation: Division of Pulmonary and Critical Care Medicine, University of California, San Diego, San Diego, CA.
authors.forename: Atul
authors.initials: A
authors.lastname: Malhotra
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D003430:Cross-Sectional Studies; D005080:Exercise Test / Q000379:methods*; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010101:Oxygen Consumption / Q000502:physiology*; D017286:Polysomnography; D012016:Reference Values; D018570:Risk Assessment; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000453:epidemiology*; D055815:Young Adult
keywords: cardiopulmonary exercise test; exercise test; exercise tolerance; obstructive sleep apnea; risk assessment