title: Effects of continuous positive airway pressure therapy on glycaemic control, insulin sensitivity and body mass index in patients with obstructive sleep apnoea and type 2 diabetes: a systematic review and meta-analysis.
abstract: BACKGROUND
  Evidence suggests that 15-30% of individuals with obstructive sleep apnoea (OSA) have type 2 diabetes mellitus (T2DM), and that OSA is an independent risk factor for T2DM. There is considerable interest in ascertaining whether OSA treatment improves glycaemic control and insulin sensitivity in patients with OSA and T2DM.
  
  
  OBJECTIVE
  To assess the effects of continuous positive airway pressure (CPAP) therapy on glycosylated haemoglobin (HbA1c) level, insulin sensitivity and body mass index (BMI) in patients with OSA and T2DM.
  
  
  METHODS
  MEDLINE, EMBASE and the Cochrane Library were searched to identify prospective studies involving patients with OSA and T2DM who had received CPAP, and data on primary outcome (change in HbA1c) and/or secondary outcomes (changes in insulin sensitivity and BMI) were reported. All relevant studies published before 31 January 2014 were included.
  
  
  RESULTS
  Six studies were included in the systematic review and meta-analysis. The numbers of patients ranged from 9 to 44 (total=128), and mean age ranged from 50.7 to 66.1 years. For the change in HbA1c (six studies, 128 patients), the combined standardised paired difference revealed no significant effect of CPAP (-0.071, 95% confidence interval (CI)=-0.245, 0.103; P=0.421). Similarly, there was no significant effect of CPAP on the change in BMI (-0.102, 95% CI=-0.296, 0.092; P=0.302; five studies, 103 patients). In contrast, there was a significant effect of CPAP on the change (improvement) in insulin sensitivity (0.330, 95% CI=0.001, 0.658; P=0.049; three studies, 39 patients).
  
  
  CONCLUSIONS
  The limited available evidence from randomised controlled trials and prospective observational studies suggests that CPAP does not decrease HbA1c level or BMI in patients with OSA and T2DM but may improve insulin sensitivity.
authors.affiliation: Department of Endocrinology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Feng
authors.affiliation: Department of Endocrinology, The First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, Zhejiang, China.
authors.forename: Zhe
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Intensive Care Unit, Ningbo Medical Treatment Center Lihuili Hospital, Ningbo, China.
authors.forename: Zhou-zhou
authors.initials: ZZ
authors.lastname: Dong
mesh_terms: D000293:Adolescent; D000328:Adult; D015992:Body Mass Index; D002648:Child; D015897:Comorbidity; D045422:Continuous Positive Airway Pressure; D003924:Diabetes Mellitus, Type 2 / Q000453:epidemiology; D005260:Female; D006442:Glycated Hemoglobin / Q000032:analysis*; D006801:Humans; D007333:Insulin Resistance; D008297:Male; D020181:Sleep Apnea, Obstructive / Q000453:epidemiology / Q000503:physiopathology* / Q000628:therapy*; D055815:Young Adult
chemical_list: D006442:Glycated Hemoglobin