title: Elevated serum cystatin C in severe OSA younger men without complications.
abstract: OBJECTIVE
  Serum cystatin C is a promising new biomarker of glomerular filtration rate and cardiovascular events, but few studies focused on serum cystatin C levels in obstructive sleep apnea (OSA) patients. The aim of our study was to evaluate the association between serum cystatin C and OSA in younger men (≤40 years old of age) without complications.
  
  
  METHODS
  We prospectively recruited consecutive participants without comorbidities who underwent polysomnography. Fasting blood samples were obtained from all subjects for biological profile measurements. Statistical analysis was used to evaluate the relationship between serum cystatin C and other parameters.
  
  
  RESULTS
  The population consisted of 98 subjects (mean age = 32.5 years, mean body mass index = 27.93 kg/m(2)) that were divided according to polysomnographic finding into control group (n = 23), mild (n = 15), moderate (n = 24), and severe (n = 36) OSA group. Compared with the control group, patients with severe OSA were significantly heavier (body mass index, 29.69 ± 3.81 vs. 26.42 ± 3.10) and presented significantly higher levels of high sensitive C-reactive protein (hsCRP) (1.10 ± 0.28 vs. 0.88 ± 0.20 mg/l) and serum cystatin C (0.87 ± 0.12 vs. 0.74 ± 0.10 mg/l) (p < 0.05 for all comparisons). Cystatin C was correlated with Apnea Hypopnea Index (AHI), Oxygen Desaturation Index, hsCRP, creatinine, and estimated glomerular filtration rate (r = 0.319, 0.279, 0.321, 0.233, -0.241, p = 0.001, 0.005, 0.001, 0.021, 0.017, respectively). After adjustment for confounding factors, AHI was significantly and positively associated with serum cystatin C levels (β = 0.284, p = 0.007).
  
  
  CONCLUSIONS
  Our finding indicated that serum cystatin C was associated with the severity of OSA in younger men. Further study is needed to find out whether OSA patients with increased serum cystatin C levels are prone to subclinical cardiovascular and renal diseases.
authors.affiliation: Department of Respiratory Medicine, The First Affiliated Hospital of Fujian Medical University, Fuzhou, People's Republic of China.
authors.forename: Xiao-Bin
authors.initials: XB
authors.lastname: Zhang
authors.forename: Qi-Chang
authors.initials: QC
authors.lastname: Lin
authors.forename: Chao-Sheng
authors.initials: CS
authors.lastname: Deng
authors.forename: Gong-Ping
authors.initials: GP
authors.lastname: Chen
authors.forename: Zhi-Ming
authors.initials: ZM
authors.lastname: Cai
authors.forename: Hua
authors.initials: H
authors.lastname: Chen
mesh_terms: D000328:Adult; D000367:Age Factors; D001143:Arousal / Q000502:physiology; D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000378:metabolism; D055316:Cystatin C / Q000097:blood*; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D017286:Polysomnography; D020181:Sleep Apnea, Obstructive / Q000097:blood*; D012913:Snoring / Q000097:blood
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D002097:C-Reactive Protein