title: Meta-analyses of the Association of Sleep Apnea with Insulin Resistance, and the Effects of CPAP on HOMA-IR, Adiponectin, and Visceral Adipose Fat.
abstract: OBJECTIVE
  We sought to conduct an updated meta-analysis of randomized controlled trials (RCTs) on the effect of continuous positive airway pressure (CPAP) on insulin resistance, as measured by homeostasis model assessment of insulin resistance (HOMA-IR), visceral abdominal fat (VAF), and adiponectin. Additionally, we performed a separate meta-analysis and meta-regression of studies on the association of insulin resistance and obstructive sleep apnea (OSA).
  
  
  METHODS
  All included studies were searched from PubMed (from conception to March 15, 2014). Data were pooled across all included RCTs as the mean difference in HOMA-IR and VAF, and as the standardized mean difference in the case of adiponectin analysis. From the included case-control studies, data on the difference of HOMA-IR between cases and controls were pooled across all studies, as the standardized mean difference (SMD).
  
  
  RESULTS
  There was a significant difference in HOMA-IR (-0.43 [95% CIs: -0.75 to -0.11], p = 0.008) between CPAP treated and non CPAP treated participants. However, there was no significant difference in VAF or adiponectin; (-47.93 [95% CI: -112.58 to 16.72], p = 0.14) and (-0.06 [95% CI: -0.28 to 0.15], p = 0.56), respectively. Meta-analysis of 16 case-control studies showed a pooled SMD in HOMA-IR of 0.51 (95% CI: 0.28 to 0.75), p ≤ 0.001, between cases and controls.
  
  
  CONCLUSIONS
  The results of our meta-analyses show that CPAP has a favorable effect on insulin resistance. This effect is not associated with any significant changes in total adiponectin levels or amount of VAF. Our findings also confirm a significant association between OSA and insulin resistance.
authors.affiliation: Division of Pulmonary, Critical Care, and Sleep Medicine, University of South Carolina School of Medicine, Columbia, SC.
authors.forename: Imran H
authors.initials: IH
authors.lastname: Iftikhar
authors.affiliation: Woolcock Institute of Medical Research, Central Clinical School, University of Sydney, Australia.
authors.forename: Camilla M
authors.initials: CM
authors.lastname: Hoyos
authors.affiliation: Woolcock Institute of Medical Research, Central Clinical School, University of Sydney, Australia.|Department of Respiratory and Sleep Medicine, Royal North Shore Hospital, Sydney, Australia.
authors.forename: Craig L
authors.initials: CL
authors.lastname: Phillips
authors.affiliation: Divison of Pulmonary, Allergy, Critical Care, and Sleep Medicine, Ohio State University Wexner Medical Center, Columbus, OH.
authors.forename: Ulysses J
authors.initials: UJ
authors.lastname: Magalang
mesh_terms: D052242:Adiponectin / Q000097:blood*; D045422:Continuous Positive Airway Pressure; D006801:Humans; D007333:Insulin Resistance / Q000502:physiology*; D050152:Intra-Abdominal Fat / Q000473:pathology*; D008875:Middle Aged; D020181:Sleep Apnea, Obstructive / Q000473:pathology / Q000503:physiopathology* / Q000628:therapy
chemical_list: D052242:Adiponectin
keywords: adiponectin; continuous positive airway pressure; insulin resistance; obstructive sleep apnea; visceral abdominal fat