Mandibular advancement device versus CPAP in lowering 24-hour blood pressure in patients with obstructive sleep apnoea and hypertension: the CRESCENT trial protocol.

INTRODUCTION: Although treatment of obstructive sleep apnoea (OSA) using continuous positive airway pressure (CPAP) reduces blood pressure (BP), adherence to CPAP is often suboptimal. A mandibular advancement device (MAD) is a guideline-endorsed alternative therapy for OSA. Still, there is limited evidence on the relative efficacy between MAD and CPAP on BP reduction. We evaluate whether treatment of moderate-to-severe OSA using MAD can improve BP and other health-related outcomes compared with CPAP. METHODS AND ANALYSIS: This is a randomised, controlled, non-inferiority trial conducted. We will recruit 220 Asians with a history of hypertension and high cardiovascular risk for an overnight polysomnography screening. Those with moderate-to-severe OSA (apnoea-hypopnoea index ≥15 events/hour) will be randomised to treatment with either MAD or CPAP in a 1:1 ratio. Stratified by age (60 vs <60 years old), body mass index (25 vs <25 kg/m2) and apnoea-hypopnoea index (30 vs <30 events/hour), an adaptive randomisation scheme with permuted blocks constructed in real-time is implemented to restrict imbalance. The overall study duration is 12 months. The primary endpoint is the 24-hour mean arterial BP difference between baseline and 6-month follow-up. The secondary endpoints include other measures of ambulatory BP monitoring, arrhythmia based on a 4-day electrocardiographic monitoring, biomarker and proteomic analysis, cardiovascular magnetic resonance-derived myocardial fibrosis and remodelling and quality-of-life questionnaires. Recruitment began in October 2019 and ended in December 2022. Comparison between MAD and CPAP will be performed using covariance (ANCOVA) analysis of the changes in 24-hour mean arterial BP while adjusting for the baseline 24-hour mean arterial BP. We will compare the 95% CIs around the treatment difference point estimate with the prespecified non-inferiority margin (1.5 mm Hg). If the upper limit of the 95% CI is <1.5 mm Hg and crosses 0, non-inferiority of the MAD relative to CPAP will be established. ETHICS AND DISSEMINATION: The Domain Specific Review Board-C, National Healthcare Group under approved the study protocol (NHG DSRB Ref: 2019/00359, approved on 28 August 2019). Study findings will be disseminated to various local, national, and international audiences through abstract presentations and publication in peer-reviewed journals. TRIAL REGISTRATION NUMBER: NCT04119999.