title: Association between heart rate recovery and severity of obstructive sleep apnea syndrome.
abstract: BACKGROUND
  Obstructive sleep apnea syndrome (OSAS) is associated with autonomic dysfunction and metabolic abnormalities including obesity, dyslipidemia, and insulin resistance. Heart rate recovery at 1min after exercise termination (HRR-1) is a marker of vagal tone. We hypothesized that patients with more severe OSAS would have a lower HRR-1, either due to the co-existing metabolic abnormalities or OSAS.
  
  
  METHODS
  Sixty-three patients with untreated OSAS (49.2+/-9.8years) without glucose- or lipid-lowering or negatively chronotropic drugs underwent cardiopulmonary exercise testing including HRR-1 measurement and assessment of several metabolic parameters. Patients with severe OSAS (apnea-hypopnea index [AHI]>30h(-1); n=32) were compared to patients with mild to moderate OSAS (AHI 5-30h(-1); n=31).
  
  
  RESULTS
  Patients with severe OSAS were more likely to be male (25 vs. 3%; p=0.01) and to have hypertension (72 vs. 39%; p=0.01); they also had higher fasting glucose (5.4+/-0.5 vs. 5.1+/-0.4mmol/l; p=0.016) and C-peptide [905 (651-1353) vs. 749 (597-919)pmol/l; p=0.028] levels compared to patients with mild to moderate OSAS. The groups did not differ with respect to peak heart rate (p=0.2) or peak oxygen consumption (p=0.9), but HRR-1 was significantly lower in patients with severe OSAS compared to patients with mild and moderate OSAS [20 (15-25) vs. 24 (18-34)bpm; p=0.022]. Higher AHI (p=0.01) and lower peak heart rate (p=0.02), but not body mass index or insulin resistance, were independently associated with lower HRR-1.
  
  
  CONCLUSIONS
  The severity of OSAS expressed as higher AHI is independently associated with lower HRR-1, a measure of autonomic dysfunction.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, Kantonsspital St. Gallen, CH-9007 St. Gallen, Switzerland. micha.maeder@bluewin.ch
authors.forename: Micha T
authors.initials: MT
authors.lastname: Maeder
authors.forename: Thomas
authors.initials: T
authors.lastname: Münzer
authors.forename: Hans
authors.initials: H
authors.lastname: Rickli
authors.forename: Otto D
authors.initials: OD
authors.lastname: Schoch
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Korte
authors.forename: Christoph
authors.initials: C
authors.lastname: Hürny
authors.forename: Peter
authors.initials: P
authors.lastname: Ammann
mesh_terms: D000328:Adult; D000368:Aged; D001341:Autonomic Nervous System / Q000503:physiopathology*; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000502:physiology; D001823:Body Composition / Q000502:physiology; D015992:Body Mass Index; D002096:C-Peptide / Q000097:blood; D004562:Electrocardiography; D005080:Exercise Test; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D006973:Hypertension / Q000503:physiopathology; D007333:Insulin Resistance / Q000502:physiology; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012189:Retrospective Studies; D012307:Risk Factors; D012737:Sex Factors; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology*; D014630:Vagus Nerve / Q000503:physiopathology*
chemical_list: D001786:Blood Glucose; D002096:C-Peptide