Thorax 53:341-345 doi:10.1136/thx.53.5.341
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Randomised placebo controlled trial of daytime function after continuous positive airway pressure (CPAP) therapy for the sleep apnoea/hypopnoea syndrome

  1. Heather M Englemana,
  2. Sascha E Martina,
  3. Ruth N Kingshotta,
  4. Thomas W Mackaya,
  5. Ian J Dearyb,
  6. Neil J Douglasa
  1. aRespiratory Medicine Unit, bDepartment of Psychology, cUniversity of Edinburgh, UK
  1. Professor N J Douglas, Department of Medicine, Royal Infirmary of Edinburgh, Lauriston Place, Edinburgh EH3 9YW, UK.
  • Received 9 January 1998
  • Revision requested 14 January 1998
  • Revised 9 February 1998
  • Accepted 10 February 1998


BACKGROUND Patients with the sleep apnoea/hypopnoea syndrome (SAHS) report improved sleepiness, cognitive function, and psychological well being after continuous positive airway pressure (CPAP) therapy, and it is for these daytime features that CPAP is usually given. However, few randomised or controlled studies exist on the effects of CPAP on daytime function.

METHODS A prospective, randomised, single blind, placebo controlled, crossover trial of daytime function after CPAP was conducted in 23 patients with SAHS, all with ⩾15 apnoeas+hypopnoeas/hour and ⩾2 symptoms of SAHS. All patients spent four weeks on CPAP therapy and four weeks on oral placebo treatment, following randomisation to treatment order. With ethics committee approval, patients were told the placebo tablet might improve upper airway function. Average effective CPAP use was monitored using hidden time clocks. Assessments of objective and subjective sleepiness, symptoms, cognitive performance, and psychological well being were performed on the last day of each treatment and compared.

RESULTS Objective sleepiness measured by sleep onset latency on the multiple sleep latency test improved with CPAP (mean difference from placebo +2.4 min, 95% CI 0.8 to 4.0; p<0.001) as did subjective sleepiness on the Epworth scale (mean difference –6, 95% CI –3 to –9; p = 0.001). Symptom total score also fell with CPAP (mean difference –1.6, 95% CI –2.2 to –1.0; p<0.001). No determinants of these changes with active treatment were identified, and no significant enhancements to cognitive function or psychosocial well being were found in this small sample.

CONCLUSIONS These findings provide further evidence for clinically significant benefits to daytime function from CPAP.


  • Conflict of interest: N J Douglas is a medical advisor to ResMed Ltd.