This article has a correction

Please see: Thorax 2012;68:96

Thorax 67:1090-1096 doi:10.1136/thoraxjnl-2012-202178
  • Original articles
    • Sleep disordered breathing

Continuous positive airway pressure improves sleepiness but not calculated vascular risk in patients with minimally symptomatic obstructive sleep apnoea: the MOSAIC randomised controlled trial

  1. John Stradling1,4
  1. 1Oxford Centre for Respiratory Medicine, Churchill Hospital, Oxford, UK
  2. 2Sleep Disorders Centre and Pulmonary Division, University Hospital Zurich, Zurich, Switzerland
  3. 3Medical Research Council Clinical Trials Unit, London, UK
  4. 4Oxford University and Oxford Biomedical Research Centre, Churchill Hospital, Oxford, UK
  1. Correspondence to Dr Sonya Elizabeth Craig, Oxford Centre for Respiratory Medicine, Churchill Hospital, Old Road, Headington, Oxford OX3 7LJ, UK; sonya.craig{at}
  • Received 28 June 2012
  • Accepted 5 October 2012
  • Published Online First 30 October 2012


Background Continuous positive airway pressure (CPAP) for symptomatic obstructive sleep apnoea (OSA) improves sleepiness and reduces vascular risk, but such treatment for the more prevalent, minimally symptomatic disease is contentious.

Methods This multicentre, randomised controlled, parallel, hospital-based trial across the UK and Canada, recruited 391 patients with confirmed OSA (oxygen desaturation index >7.5/h) but insufficient symptoms to warrant CPAP therapy. Patients were randomised to 6 months of auto-adjusting CPAP therapy, or standard care. Coprimary endpoints were change in Epworth Sleepiness Score (ESS) and predicted 5-year mortality using a cardiovascular risk score (components: age, sex, height, systolic blood pressure, smoking, diabetes, cholesterol, creatinine, left ventricular hypertrophy, previous myocardial infarction or stroke). Secondary endpoints included some of the individual components of the vascular risk score, objectively measured sleepiness and self-assessed health status.

Results Of 391 patients randomised, 14 withdrew, 347 attended for their follow-up visit at 6 months within the predefined time window, of which 341 had complete ESS data (baseline mean 8.0, SD 4.3) and 310 had complete risk score data. 22% of patients in the CPAP group reported stopping treatment and overall median CPAP use was 2 : 39 h per night. CPAP significantly improved subjective daytime sleepiness (adjusted treatment effect on ESS −2.0 (95% CI −2.6 to −1.4), p<0.0001), objectively measured sleepiness and self-assessed health status. CPAP did not improve the 5-year calculated vascular risk or any of its components.

Conclusions In patients with minimally symptomatic OSA, CPAP can reduce subjective and objective daytime sleepiness, and improve self-assessed health status, but does not appear to improve calculated vascular risk.