title: Complex sleep apnea syndrome: is it a unique clinical syndrome?
abstract: OBJECTIVE
  Some patients with apparent obstructive sleep apnea hypopnea syndrome (OSAHS) have elimination of obstructive events but emergence of problematic central apneas or Cheyne-Stokes breathing pattern. Patients with this sleep-disordered breathing problem, which for the sake of study we call the "complex sleep apnea syndrome," are not well characterized. We sought to determine the prevalence of complex sleep apnea syndrome and hypothesized that the clinical characteristics of patients with complex sleep apnea syndrome would more nearly resemble those of patients with central sleep apnea syndrome (CSA) than with those of patients with OSAHS.
  
  
  METHODS
  Retrospective review
  
  
  METHODS
  Sleep disorders center.
  
  
  METHODS
  Two hundred twenty-three adults consecutively referred over 1 month plus 20 consecutive patients diagnosed with CSA.
  
  
  METHODS
  NA.
  
  
  RESULTS
  Prevalence of complex sleep apnea syndrome, OSAHS, and CSA in the 1-month sample was 15%, 84%, and 0.4%, respectively. Patients with complex sleep apnea syndrome differed in gender from patients with OSAHS (81% vs 60% men, p < .05) but were otherwise similar in sleep and cardiovascular history. Patients with complex sleep apnea syndrome had fewer maintenance-insomnia complaints (32% vs 79%; p < .05) than patients with CSA but were otherwise not significantly different clinically. Diagnostic apnea-hypopnea index for patients with complex sleep apnea syndrome, OSAHS, and CSA was 32.3 +/- 26.8, 20.6 +/- 23.7, and 38.3 +/- 36.2, respectively (p = .005). Continuous positive airway pressure suppressed obstructive breathing, but residual apnea-hypopnea index, mostly from central apneas, remained high in patients with complex sleep apnea syndrome and CSA (21.7 +/- 18.6 in complex sleep apnea syndrome, 32.9 +/- 30.8 in CSA vs 2.14 +/- 3.14 in OSAHS; p < .001).
  
  
  CONCLUSIONS
  Patients with complex sleep apnea syndrome are mostly similar to those with OSAHS until one applies continuous positive airway pressure. They are left with very disrupted breathing and sleep on continuous positive airway pressure. Clinical risk factors don't predict the emergence of complex sleep apnea syndrome, and best treatment is not known.
authors.affiliation: Mayo Clinic Sleep Disorders Center, Division of Pulmonary and Critical Care Medicine, 200 First Street SW, Rochester, MN 55905, USA. tmorgenthaler@mayo.edu
authors.forename: Timothy I
authors.initials: TI
authors.lastname: Morgenthaler
authors.forename: Vadim
authors.initials: V
authors.lastname: Kagramanov
authors.forename: Viktor
authors.initials: V
authors.lastname: Hanak
authors.forename: Paul A
authors.initials: PA
authors.lastname: Decker
mesh_terms: D000328:Adult; D045422:Continuous Positive Airway Pressure / Q000379:methods; D003710:Demography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D015995:Prevalence; D012189:Retrospective Studies; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000175:diagnosis* / Q000453:epidemiology / Q000628:therapy; D012895:Sleep, REM / Q000502:physiology