title: Obstructive sleep apnoea and risks of all-cause mortality: preliminary evidence from prospective cohort studies.
abstract: OBJECTIVE
  A meta-analysis of prospective cohort studies was conducted to clarify the association between obstructive sleep apnoea (OSA) and future risk of all-cause mortality.
  
  
  METHODS
  Eligible studies were identified by searching the PubMed and EMBASE databases up to July 2015. Pooled hazard ratios (HRs) and their corresponding 95 % confidence intervals (CIs) were calculated to estimate the association between OSA and risk of all-cause mortality. Sources of heterogeneity were identified by subgroup and meta-regression analyses.
  
  
  RESULTS
  Twelve prospective cohort studies involving 34,382 participants were included in this meta-analysis. The pooled HR of all-cause mortality was 1.262 (95 % CI 1.093-1.431) with significant heterogeneity. Subgroup analyses indicated that the pooled HRs of all-cause mortality in patients with mild, moderate and severe OSA were 0.945 (95 % CI 0.810-1.081), 1.178 (95 % CI 0.978-1.378) and 1.601 (95 % CI 1.298-1.902), respectively. OSA severity could be a possible sources of heterogeneity. Existing publication bias produced a minor contribution to effect size.
  
  
  CONCLUSIONS
  Severe, but not mild to moderate, OSA is significantly associated with increased risk of all-cause mortality.
authors.affiliation: Department of Respiratory and Critical Care Medicine, Binzhou Medical University Hospital, Binzhou, Shandong, 256603, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Pan
authors.affiliation: Department of Radiotherapy, Xuzhou Central Hospital, The Affiliated Xuzhou Hospital of Medical College of Southeast University, Xuzhou, Jiangsu, 221009, China.
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Xie
authors.affiliation: Department of Respiratory Medicine, XuZhou Central Hospital, The Affiliated XuZhou Hospital of Medical College of Southeast University, 199 South Jiefang Road, Xuzhou, Jiangsu, 221009, China.
authors.forename: Dayue
authors.initials: D
authors.lastname: Liu
authors.affiliation: Department of Respiratory Medicine, The Affiliated Hospital of Qingdao University, Qingdao, Shandong, 266003, China.
authors.forename: Dunqiang
authors.initials: D
authors.lastname: Ren
authors.affiliation: Department of Respiratory Medicine, XuZhou Central Hospital, The Affiliated XuZhou Hospital of Medical College of Southeast University, 199 South Jiefang Road, Xuzhou, Jiangsu, 221009, China. yongzhguo@sina.cn.
authors.forename: Yongzhong
authors.initials: Y
authors.lastname: Guo
mesh_terms: D002423:Cause of Death; D015331:Cohort Studies; D006801:Humans; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D020181:Sleep Apnea, Obstructive / Q000401:mortality*
keywords: All-cause mortality; Meta-analysis; Obstructive sleep apnoea