title: C-reactive protein is associated with obstructive sleep apnea independent of visceral obesity.
abstract: BACKGROUND
  Obstructive sleep apnea (OSA) is associated with adverse cardiovascular outcomes. C-reactive protein (CRP) predicts atherosclerotic complications. Our study evaluates whether OSA is associated with an elevated CRP level, after elimination of known confounders including visceral obesity.
  
  
  METHODS
  Men without significant chronic medical illness, regular medications, or illness in the preceding 4 weeks were enrolled. Subjects with morbid obesity, newly detected high BP, or fasting glucose were excluded. They underwent polysomnography and MRI of abdomen to quantify visceral fat volume. High-sensitivity CRP levels were measured.
  
  
  RESULTS
  111 men with mean body mass index (BMI) 26.3 +/- 3.8 kg/m(2) were evaluated. After adjustment for age, smoking, BMI, waist circumference, and sleep efficiency, CRP correlated positively with the apnea-hypopnea index (AHI) [r = 0.35, p < 0.001], duration of O(2) saturation < 90% (r = 0.29, p = 0.002), and arousal index (r = 0.32, p = 0.001), and it correlated negatively with minimal O(2) saturation (r = -0.29, p = 0.002). These correlations were consistent when adjustment was made for MRI visceral fat volume instead of waist circumference. In the regression model, significant predictors of CRP included AHI, waist circumference, and triglycerides (adjusted R(2), 0.33, p = 0.001, p = 0.002, p = 0.018, respectively). Among the 111 subjects, 32 subjects with no or mild OSA (AHI < 15 events/h) were matched with 32 subjects with moderate-to-severe OSA (AHI > or = 15 events/h) in MRI visceral fat volume. CRP was higher in subjects with moderate-to-severe OSA (median, 1.32; 0.45 to 2.34 mg/L) when compared to subjects with no or mild OSA (median, 0.54; 0.25 to 0.89 mg/L; p = 0.001).
  
  
  CONCLUSIONS
  In healthy middle-aged men, elevated CRP level is associated with OSA independent of visceral obesity.
authors.affiliation: Department of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
authors.forename: Macy Mei-Sze
authors.initials: MM
authors.lastname: Lui
authors.affiliation: Department of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
authors.forename: Jamie Chung-Mei
authors.initials: JC
authors.lastname: Lam
authors.affiliation: Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
authors.forename: Henry Ka-Fung
authors.initials: HK
authors.lastname: Mak
authors.affiliation: Research Centre of Heart, Brain, Hormone and Healthy Aging, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
authors.forename: Aimin
authors.initials: A
authors.lastname: Xu
authors.affiliation: Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
authors.forename: Clara
authors.initials: C
authors.lastname: Ooi
authors.affiliation: Department of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
authors.forename: David Chi-Leung
authors.initials: DC
authors.lastname: Lam
authors.affiliation: Department of Medicine, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
authors.forename: Judith Choi-Wo
authors.initials: JC
authors.lastname: Mak
authors.affiliation: Department of Diagnostic Radiology, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China.
authors.forename: Pek Lan
authors.initials: PL
authors.lastname: Khong
authors.affiliation: Research Centre of Heart, Brain, Hormone and Healthy Aging, Queen Mary Hospital, The University of Hong Kong, Hong Kong Special Administrative Region, People's Republic of China. Electronic address: msmip@hkucc.hku.hk.
authors.forename: Mary Sau-Man
authors.initials: MS
authors.lastname: Ip
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000032:analysis*; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000032:analysis*; D006801:Humans; D050152:Intra-Abdominal Fat; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012680:Sensitivity and Specificity; D020181:Sleep Apnea, Obstructive / Q000378:metabolism*; D055105:Waist Circumference
chemical_list: D015415:Biomarkers; D002097:C-Reactive Protein