• Malcolm Kohler, Sonya Craig, Pepperell Justin C T JCT Somerset Centre for Respiratory Medicine, Musgrove Park Hospital, Taunton, England., Debby Nicoll, Daniel J Bratton, Andrew J Nunn, Paul Leeson, and John R Stradling.
• Sleep Unit and Pulmonary Division, University Hospital Zurich, Zurich, Switzerland; Oxford Centre for Respiratory Medicine and Oxford Biomedical Research Centre, Churchill Hospital, Oxford, England. Electronic address: Malcolm.K@bluewin.ch.
• Chest. 2013 Sep 1; 144 (3): 896-902.

BackgroundMinimally symptomatic OSA is a highly prevalent disorder, and the effects of CPAP on vascular function in these patients are unknown. This trial aimed to investigate whether CPAP improves vascular function in minimally symptomatic OSA.MethodsIn two centers taking part in the MOSAIC (Multicentre Obstructive Sleep Apnoea Interventional Cardiovascular) trial, 253 patients with minimally symptomatic OSA were randomized to 6 months of CPAP or standard care. Two hundred eight patients attended their follow-up visit within the predefined time window and had complete measurements of arterial stiffness (augmentation index [AIx]), and 64 patients had endothelial function measurements by brachial artery flow-mediated dilatation (FMD). Multivariable analyses adjusting for baseline measurements and minimization factors were performed to assess the effect of CPAP treatment on FMD (% dilatation) and AIx (% augmentation) compared with standard care.ResultsThe mean ± SD baseline oxygen desaturation index and Epworth Sleepiness Score (ESS) of the 208 patients (age 58 ± 7.3 years, 31 women) were 13.7 ± 12.8 events/h and 8.3 ± 4.2, respectively. There was no CPAP treatment effect on arterial stiffness (AIx, -1.4%; 95% CI, -3.6 to +0.9%; P = .23), but CPAP improved endothelial function (FMD, +2.1%; 95% CI, +1.0 to +3.2%; P < .0001). CPAP reduced daytime sleepiness (ESS, -2.2; 95% CI, -3.0 to -1.5; P < .0001) compared with standard care. There was a larger improvement in FMD in patients using CPAP for > 4 h/night than those who used it less (P = .013).ConclusionsCPAP improves endothelial function, but not arterial stiffness, in minimally symptomatic OSA. Thus, minimally symptomatic OSA may be a cardiovascular risk factor.Trial RegistryISRCTN Register; No.: ISRCTN 34164388; URL: http://isrctn.org.

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