title: Effect of CPAP on blood pressure in patients with minimally symptomatic obstructive sleep apnoea: a meta-analysis using individual patient data from four randomised controlled trials.
abstract: BACKGROUND
  CPAP reduces blood pressure (BP) in patients with symptomatic obstructive sleep apnoea (OSA). Whether the same benefit is present in patients with minimally symptomatic OSA is unclear, thus a meta-analysis of existing trial data is required.
  
  
  METHODS
  The electronic databases Medline, Embase and trial registries were searched. Trials were eligible if they included patients with minimally symptomatic OSA, had randomised them to receive CPAP or either sham-CPAP or no CPAP, and recorded BP at baseline and follow-up. Individual participant data were obtained. Primary outcomes were absolute change in systolic and diastolic BP.
  
  
  RESULTS
  Five eligible trials were found (1219 patients) from which data from four studies (1206 patients) were obtained. Mean (SD) baseline systolic and diastolic BP across all four studies was 131.2 (15.8) mm Hg and 80.9 (10.4) mm Hg, respectively. There was a slight increase in systolic BP of 1.1 mm Hg (95% CI -0.2 to 2.3, p=0.086) and a slight reduction in diastolic BP of 0.8 mm Hg (95% CI -1.6 to 0.1, p=0.083), although the results were not statistically significant. There was some evidence of an increase in systolic BP in patients using CPAP <4 h/night (1.5 mm Hg, 95% CI -0.0 to 3.1, p=0.052) and reduction in diastolic BP in patients using CPAP >4 h/night (-1.4 mm Hg, 95% CI -2.5 to -0.4, p=0.008). CPAP treatment reduced both subjective sleepiness (p<0.001) and OSA severity (p<0.001).
  
  
  CONCLUSIONS
  Although CPAP treatment reduces OSA severity and sleepiness, it seems not to have a beneficial effect on BP in patients with minimally symptomatic OSA, except in patients who used CPAP for >4 h/night.
authors.affiliation: Medical Research Council Clinical Trials Unit at University College London, London, UK.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Bratton
authors.affiliation: Oxford Centre for Respiratory Medicine and NIHR Biomedical Research Centre, Oxford University, Oxford, UK.
authors.forename: John R
authors.initials: JR
authors.lastname: Stradling
authors.affiliation: Department of Pneumology, Biomedical Research Institute IRB Lleida and CIBERES, Madrid, Spain.
authors.forename: Ferran
authors.initials: F
authors.lastname: Barbé
authors.affiliation: Division of Pulmonology, University Hospital Zurich, Zurich, Switzerland.
authors.forename: Malcolm
authors.initials: M
authors.lastname: Kohler
mesh_terms: D001794:Blood Pressure / Q000502:physiology*; D045422:Continuous Positive Airway Pressure / Q000379:methods*; D006801:Humans; D016032:Randomized Controlled Trials as Topic; D020181:Sleep Apnea, Obstructive / Q000503:physiopathology / Q000628:therapy*
keywords: Sleep Apnoea