title: Obstructive sleep apnea is associated with visit-to-visit variability in low-density lipoprotein-cholesterol in patients with coronary artery disease.
abstract: OBJECTIVE
  Visit-to-visit variability in low-density lipoprotein-cholesterol (LDL-C) was found to be a novel predictor of adverse cardiac events. Obstructive sleep apnea (OSA), an emerging cardiovascular risk factor, is characterized by sympathetic activation and increased oxidative stress which are regulators of LDL-C metabolism. We hypothesized that OSA was associated with LDL-C variability.
  
  
  METHODS
  We prospectively recruited 190 patients with coronary artery disease for an overnight sleep study. Statin was prescribed upon discharge for 186 patients. Serum LDL-C levels were measured at clinic every 3 to 6 months. Severity of OSA (on the basis of apnea-hypopnea index (AHI)) was correlated with visit-to-visit LDL-C variability (on the basis of variation independent of mean (VIM)) in outpatient clinic.
  
  
  RESULTS
  The mean AHI was 21.9 ± 18.9. Using an AHI cut-off of 5-14.9, 15-29.9, and ≥30, the prevalence of mild, moderate, and severe OSA was 26.3, 18.9, and 27.4 %, respectively. After 53.2 ± 25.3 months, LDL-C was recorded over 8.1 ± 4.2 measurements. VIM positively correlated with AHI (Pearson's r = 0.183, p = 0.016), but not body mass index, baseline and mean follow-up LDL-C levels, and number of LDL-C measurements. In multiple linear regression analysis, AHI remained an independent predictor of VIM after adjusting for diabetes mellitus and hyperlipidemia. A 10-unit rise in AHI led to a 3.8 % increase in VIM (95 % CI 0.1 to 7.4 %; p = 0.044).
  
  
  CONCLUSIONS
  This is the first study to show the independent correlation between OSA severity and visit-to-visit LDL-C variability. Our finding contributes to the understanding of the vasculopathic effects of OSA.
authors: Department of Cardiology, National University Heart Centre Singapore, 1E, Kent Ridge Road, Singapore, 119228, Singapore.
authors: Gavin
authors: G
authors: Ng
authors: Department of Cardiology, National University Heart Centre Singapore, 1E, Kent Ridge Road, Singapore, 119228, Singapore.
authors: Elaine
authors: E
authors: Boey
authors: Department of Medicine, University of Otago, Christchurch, New Zealand.
authors: Chris
authors: C
authors: Frampton
authors: Department of Cardiology, National University Heart Centre Singapore, 1E, Kent Ridge Road, Singapore, 119228, Singapore.|Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore.
authors: Arthur Mark
authors: AM
authors: Richards
authors: Department of Cardiology, National University Heart Centre Singapore, 1E, Kent Ridge Road, Singapore, 119228, Singapore.
authors: Tiong-Cheng
authors: TC
authors: Yeo
authors: Department of Cardiology, National University Heart Centre Singapore, 1E, Kent Ridge Road, Singapore, 119228, Singapore. mdclchr@nus.edu.sg.|Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore. mdclchr@nus.edu.sg.
authors: Chi-Hang
authors: CH
authors: Lee
mesh_terms: D000328:Adult; D000368:Aged; D008078:Cholesterol, LDL / Q000097:blood*; D015331:Cohort Studies; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D017286:Polysomnography; D012846:Singapore; D020181:Sleep Apnea, Obstructive / Q000097:blood* / Q000175:diagnosis / Q000453:epidemiology; D013223:Statistics as Topic
chemical_list: D008078:Cholesterol, LDL
keywords: Biometric; Cholesterol; Coronary artery; Hypoxia; Sleep