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INTRODUCTION:Continuous positive airway pressure (CPAP) is currently the treatment of choice for sleepiness in patients with obstructive sleep apnea (OSA), however, adherence is often thought to be suboptimal. We investigated the effects of suboptimal CPAP-usage on objective and subjective sleepiness parameters in patients with OSA. MATERIAL AND METHODS:In this 2-week, parallel, double-blind, randomised controlled trial we enrolled moderate-to-severe OSA patients with excessive pre-treatment daytime sleepiness (Epworth-Sleepiness-Scale [ESS] score >10 points) who had suboptimal CPAP adherence over at least 12 months (mean nightly usage time 3-4 h). Patients were allocated through minimisation to either subtherapeutic CPAP ("sham-CPAP") or continuation of CPAP (therapeutic-CPAP). A Bayesian analysis with historical priors calculated the posterior probability of superiority. RESULTS:Between May, 2016 and November, 2018, 57 patients (60±8 years, 79% men, 93% Caucasian) were allocated in total, and 52 who completed the study (50% in each arm) were included in the final analysis. The unadjusted ESS-score increase was +2.4 points (95% CI +0.6 to +4.2; p=0.01) in the sham-CPAP-group when compared to continuing therapeutic CPAP. The probability of superiority of therapeutic CPAP over sham CPAP was 90.4% for ESS, 90.1% for systolic, and 80.3% for diastolic blood pressure. CONCLUSIONS:Patients with moderate-to-severe OSA and daytime sleepiness are still getting a substantial benefit from suboptimal CPAP adherence, albeit not as much as they might get if they adhered more. Whether a similar statement can be made for even lower adherence levels remains to be established in future trials.

Original publication




Journal article


The European respiratory journal

Publication Date



Department of Pulmonology, University Hospital Zurich, Zurich, Switzerland.