title: Severe obstructive sleep apnea increases cystatin C in clinically latent renal dysfunction.
abstract: BACKGROUND
  Obstructive sleep apnea (OSA) increases the risk of cardiovascular disease (CVD) and has been reported to be associated with chronic kidney disease (CKD). Recent studies have demonstrated that cystatin C is a prognostic biomarker of the risk of death and CVD even in patients without established CKD.
  
  
  METHODS
  In a cross-sectional study, we enrolled 267 consecutive OSA patients without CKD who had an apnea-hypopnea index (AHI) ≥ 5 events per hour in overnight polysomnography. CKD was defined as an estimated glomerular filtration rate (eGFR) < 60 mL/min/1.73 m(2) according to the modification of diet in renal disease (MDRD) equation (modified for Japanese). Serum cystatin C levels were measured in all patients.
  
  
  RESULTS
  Cystatin C was significantly correlated with age (r = 0.37), body mass index (BMI) (r = 0.12), AHI (r = 0.17), C-reactive protein (CRP) (r = 0.12), and Brachial-ankle pulse wave velocity (r = 0.18). Logistic regression analysis demonstrated that severe OSA defined by an AHI ≥ 30 events per hour was an independent variable for the highest quartiles of serum cystatin C levels (≥0.88 mg/L) (OR: 2.04, 95% CI: 1.04-4.01, P = 0.04) even after adjustment for age, BMI ≥ 25, hypertension, and diabetes mellitus.
  
  
  CONCLUSIONS
  This study indicates that severe OSA independently increases serum cystatin C levels in patients without CKD. Cystatin C is considered to be a biomarker that reflects both clinically latent renal dysfunction and cardiovascular risk that are influenced by OSA.
authors.affiliation: Department of Cardiology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo 160-0023, Japan.
authors.forename: Kota
authors.initials: K
authors.lastname: Kato
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Takata
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Usui
authors.forename: Kazuki
authors.initials: K
authors.lastname: Shiina
authors.forename: Kihiro
authors.initials: K
authors.lastname: Asano
authors.forename: Yuki
authors.initials: Y
authors.lastname: Hashimura
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Saruhara
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Nishihata
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Tomiyama
authors.forename: Akira
authors.initials: A
authors.lastname: Yamashina
mesh_terms: D000367:Age Factors; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D002318:Cardiovascular Diseases / Q000209:etiology / Q000378:metabolism*; D003430:Cross-Sectional Studies; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D051436:Renal Insufficiency, Chronic / Q000150:complications / Q000175:diagnosis / Q000378:metabolism* / Q000503:physiopathology; D012307:Risk Factors; D020181:Sleep Apnea, Obstructive / Q000150:complications / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D055316:Cystatin C