title: Creatine phosphokinase elevation in obstructive sleep apnea syndrome: an unknown association?
abstract: OBJECTIVE
  To evaluate the impact of obstructive sleep apnea syndrome (OSAS) on serum creatine phosphokinase (CK) levels.
  
  
  METHODS
  Single-center prospective cross-sectional study.
  
  
  METHODS
  Academic sleep disorder center.
  
  
  METHODS
  Two hundred one consecutive patients (mean [+/- SD] age, 54.9 +/- 11.0 years; 155 men and 46 women; mean body mass index, 31.3 +/- 6.9 kg/m(2)) with suspected sleep-disordered breathing.
  
  
  RESULTS
  OSAS was confirmed in182 patients (apnea-hypopnea index [AHI], > 5 events per hour) and was ruled out in 19 patients (control subjects) by standard polysomnography. Sixty-six OSAS patients and 1 control patient showed an unexplained CK elevation. The mean baseline CK level was significantly higher in patients with severe OSAS (AHI, > 30 event per hour; n = 89) compared to those with mild-to-moderate OSAS (AHI, 5 to 30 events per hour; n = 93) and control subjects (191.4 +/- 12.9 vs 134.3 +/- 7.5 vs 107.1 +/- 7.9 U/L, respectively; p < 0.01). Receiver operating curve analysis identified an optimal cutoff value of > 148 U/L (r = 0.660) for CK, which yielded a positive predictive value of 99%, a sensitivity of 43%, and a specificity of 95% for the diagnosis of OSAS. The mean nocturnal oxyhemoglobin saturation was the main predictor of CK level (r = 0.47; p < 0.001). Continuous positive airway pressure (CPAP) treatment resulted in a significant decline of CK levels both in patients with mild-to-moderate OSAS (n = 38; 129.7 +/- 13.4 vs 96.7 +/- 7.6 U/L, respectively; p < 0.001) and in patients with severe OSAS (n = 39; 187.7 +/- 18.9 vs 132.2 +/- 12.9 U/L, respectively; p < 0.001).
  
  
  CONCLUSIONS
  One third of our study population showed a mild-to-moderate elevation in CK level, which was highly predictive of OSAS. The application of CPAP therapy in OSAS patients resulted in a significant decrease in CK level. We speculate that OSAS may account for a substantial number of cases of unexplained CK elevation (ie, hyperCKemia). Further studies should address the prevalence of OSAS in patients with mild-to-moderate hyperCKemia.
authors.affiliation: Department of Internal Medicine II, University of Bonn, Sigmund-Freud-Str. 25, D-53105 Bonn, Germany.
authors.forename: Silvia
authors.initials: S
authors.lastname: Lentini
authors.forename: Robert
authors.initials: R
authors.lastname: Manka
authors.forename: Sabine
authors.initials: S
authors.lastname: Scholtyssek
authors.forename: Birgit
authors.initials: B
authors.lastname: Stoffel-Wagner
authors.forename: Berndt
authors.initials: B
authors.lastname: Lüderitz
authors.forename: Selçuk
authors.initials: S
authors.lastname: Tasci
mesh_terms: D015415:Biomarkers; D045422:Continuous Positive Airway Pressure; D003402:Creatine Kinase / Q000097:blood*; D003430:Cross-Sectional Studies; D018450:Disease Progression; D004587:Electrophoresis, Agar Gel; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D011379:Prognosis; D011446:Prospective Studies; D012720:Severity of Illness Index; D020181:Sleep Apnea, Obstructive / Q000201:enzymology* / Q000503:physiopathology / Q000628:therapy
chemical_list: D015415:Biomarkers; D003402:Creatine Kinase