title: The interaction of obstructive sleep apnea and obesity on the inflammatory markers C-reactive protein and interleukin-6: the Icelandic Sleep Apnea Cohort.
abstract: OBJECTIVE
  To assess the relative roles and interaction of obstructive sleep apnea (OSA) severity and obesity on interleukin-6 (IL-6) and C-reactive protein (CRP) levels.
  
  
  METHODS
  Cross-sectional cohort.
  
  
  METHODS
  The Icelandic Sleep Apnea Cohort.
  
  
  METHODS
  454 untreated OSA patients (380 males and 74 females), mean ± standard deviation age 54.4 ± 10.6 yr.
  
  
  METHODS
  N/A.
  
  
  RESULTS
  Participants underwent a sleep study, abdominal magnetic resonance imaging to measure total abdominal and visceral fat volume, and had fasting morning IL-6 and CRP levels measured in serum. A significantly higher correlation was found for BMI than visceral fat volume with CRP and IL-6 levels. Oxygen desaturation index, hypoxia time, and minimum oxygen saturation (SaO₂) significantly correlated with IL-6 and CRP levels, but apnea-hypopnea index did not. When stratified by body mass index (BMI) category, OSA severity was associated with IL-6 levels in obese participants only (BMI > 30 kg/m²). A multiple linear regression model with interaction terms showed an independent association of OSA severity with IL-6 levels and an interaction between OSA severity and BMI, i.e., degree of obesity altered the relationship between OSA and IL-6 levels. An independent association of OSA severity with CRP levels was found for minimum SaO₂ only. A similar interaction of OSA severity and BMI on CRP levels was found for males and postmenopausal women.
  
  
  CONCLUSIONS
  OSA severity is an independent predictor of levels of IL-6 and CRP but interacts with obesity such that this association is found only in obese patients.
authors: Department of Respiratory Medicine and Sleep, Landspitali-The National University Hospital of Iceland, Reykjavik, Iceland.
authors: Erna S
authors: ES
authors: Arnardottir
authors: Greg
authors: G
authors: Maislin
authors: Richard J
authors: RJ
authors: Schwab
authors: Bethany
authors: B
authors: Staley
authors: Bryndis
authors: B
authors: Benediktsdottir
authors: Isleifur
authors: I
authors: Olafsson
authors: Sigurdur
authors: S
authors: Juliusson
authors: Micah
authors: M
authors: Romer
authors: Thorarinn
authors: T
authors: Gislason
authors: Allan I
authors: AI
authors: Pack
mesh_terms: D050153:Abdominal Fat / Q000033:anatomy & histology; D015415:Biomarkers / Q000097:blood; D015992:Body Mass Index; D002097:C-Reactive Protein / Q000032:analysis*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000097:blood*; D050152:Intra-Abdominal Fat / Q000033:anatomy & histology; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000150:complications*; D020181:Sleep Apnea, Obstructive / Q000097:blood / Q000150:complications*
chemical_list: D015415:Biomarkers; D015850:Interleukin-6; D002097:C-Reactive Protein