The goal of this clinical trial is to evaluate the isolated and combined effects of orofacial myofunctional therapy (OMT) and continuous positive airway pressure (CPAP) in adults with mild-to-moderate obstructive sleep apnea. The main questions it aims to answer are whether OMT alone, CPAP alone, or combined OMT plus CPAP improves obstructive sleep apnea severity at Week 12, as measured by the apnea-hypopnea index (AHI), and whether these interventions improve mandibular excursion. Researchers will compare 4 groups-sham plus standard of care, OMT plus standard of care, CPAP plus standard of care, and combined OMT plus CPAP plus standard of care-to assess differences in respiratory and anatomical-functional outcomes. Participants will be randomized to 1 of the 4 study arms. During the 12-week supervised intervention phase, participants will receive their assigned intervention together with standardized sleep-hygiene and lifestyle counseling. Assessments include sleep recording, mandibular excursion measurements, questionnaires on sleepiness and sleep quality, dento-occlusal and anthropometric measurements, and treatment adherence monitoring. After Week 12, participants will enter an observational follow-up phase through Week 52 to evaluate durability of treatment effects, treatment persistence, symptom recurrence, and clinically indicated treatment modifications.

Obstructive sleep apnea (OSA) is a common chronic disorder associated with substantial cardiovascular, metabolic, and neurocognitive morbidity. Continuous positive airway pressure (CPAP) remains the standard treatment, but adherence is often suboptimal, especially in patients with mild-to-moderate OSA. Orofacial myofunctional therapy (OMT) is a promising non-pharmacological approach that may improve upper-airway function and reduce disease severity. However, few randomized studies have compared OMT and CPAP within the same factorial design, and limited data are available regarding the relationship between mandibular excursion and improvement in OSA severity. OMPACT-OSA was developed to address these gaps in a Lebanese academic clinical setting.

OMPACT-OSA is a randomized, controlled, four-arm parallel-group clinical trial with a 2 x 2 factorial treatment structure and 1:1:1:1 allocation. Randomization will be stratified by baseline OSA severity. Participants will be assigned to sham plus standard of care, OMT plus standard of care, CPAP plus standard of care, or combined OMT plus CPAP plus standard of care. Mandibular excursion assessors and polysomnography scorers will remain blinded to treatment allocation, although participants cannot be blinded to CPAP exposure. Sham follow-up visits are used to mimic the intensity of OMT follow-up and reduce performance bias. The trial includes a 12-week supervised intervention phase followed by a 40-week observational phase, for a total duration of 52 weeks.

The primary objective is to compare the efficacy of OMT alone, CPAP alone, and combined OMT plus CPAP on the severity of mild-to-moderate OSA at Week 12. The primary endpoint is apnea-hypopnea index (AHI) at Week 12 assessed by sleep recording. The key secondary endpoint is change in mandibular excursion from baseline to Week 12. Additional outcomes will assess whether baseline mandibular excursion, Mallampati score, and baseline respiratory-event phenotype (including apnea index, hypopnea index, and hypopnea-predominant versus apnea-predominant OSA) predict response to OMT, sleep quality, dento-occlusal effects, anthropometric measures, therapeutic adherence, treatment persistence, nocturnal respiratory parameters, and safety and tolerability outcomes.

Eligible participants are adults with mild-to-moderate OSA confirmed by Type I polysomnography, no previous treatment with CPAP or OMT, and sufficient protrusive excursion to allow study procedures. Participants with severe OSA or urgent need for CPAP, obesity hypoventilation syndrome or chronic ventilatory failure, unstable major cardiovascular disease, uncontrolled diabetes requiring treatment intensification, upper-airway neurological or ENT disease, craniofacial abnormalities, recent maxillofacial surgery, temporomandibular pain preventing exercises, active periodontitis, pregnancy, foreseeable non-adherence, or ongoing CPAP/OMT at inclusion will be excluded.

The sham arm consists of placebo breathing sessions combined with standard of care. The OMT arm consists of a structured 12-week program with 3 sessions per day, each lasting approximately 8 minutes, together with adherence support. The CPAP arm consists of CPAP treatment over 12 weeks, with technical and adherence support. The combined arm receives both full OMT and CPAP concurrently. Standard of care is provided uniformly to all participants and includes standardized sleep-hygiene counseling and general non-pharmacological lifestyle recommendations.

Participants will undergo baseline and follow-up assessments, including sleep studies, mandibular excursion measurements using the George Gauge and Jaw Motion Analyser, insomnia severity assessment with the ISI, review of medications affecting sleep or respiratory drive, focused evaluation of comorbid conditions likely to confound sleep-related symptoms, and Mallampati classification. Baseline polysomnography data, including apnea index, hypopnea index, and respiratory-event phenotype, will be extracted, alongside anthropometric and dento-occlusal evaluation and adherence monitoring. After Week 12, all participants enter observational follow-up through Week 52 to evaluate durability of treatment effects under real-world conditions, document treatment persistence and symptom recurrence, and prospectively record treatment resumption, crossovers, and other protocol-relevant therapeutic changes.

The final planned sample size is 168 participants, corresponding to 42 participants per arm. The primary analysis population is the intention-to-treat population. The study will be analyzed primarily as a four-arm randomized trial with a factorial structure, with prespecified sensitivity and exploratory analyses. An independent monitoring committee will be established to help ensure participant safety, proper data collection, and compliance with study procedures.

Inclusion Criteria:

• Age 18 years or older.
• Mild-to-moderate OSA (AHI 5.0-29.9 events/hour) confirmed by Type I polysomnography.
• Protrusive excursion of at least 5 mm measured with the George Gauge.
• No previous treatment with CPAP or OMT.
• Ability to perform oropharyngeal exercises.
• Written informed consent.

Exclusion Criteria:

• Severe obstructive sleep apnea (AHI 30 events/hour or higher) or urgent need for CPAP
• Suspected or confirmed obesity hypoventilation syndrome, chronic ventilatory failure, or severe obesity associated with daytime hypercapnia or hypoxemia
• Clinically significant insomnia, defined as an Insomnia Severity Index (ISI) score > 14 at screening.
• Uncontrolled psychiatric or neurological conditions likely to substantially affect sleep quality or daytime symptoms independently of OSA (e.g., major depressive episode, severe anxiety disorder, chronic disabling migraine)., as judged by the investigator.
• Current use of medications likely to affect sleep architecture, respiratory drive, or PAP tolerance, including chronic opioid therapy and other sedative medications judged incompatible with study participation.
• Unstable or severe cardiovascular disease requiring priority standard management, including poorly controlled arrhythmia, nocturnal angina, decompensated heart failure, treatment-resistant hypertension, or recent acute coronary syndrome
• Uncontrolled diabetes mellitus requiring treatment intensification, for example - HbA1c greater than 10% and/or symptomatic hyperglycemia
• Neurological or ear-nose-throat disease affecting the upper airway
• Craniofacial abnormalities
• Maxillofacial surgery within the previous 6 months
• Temporomandibular pain preventing completion of exercises
• Active periodontitis
• Pregnancy
• Foreseeable non-adherence to the intervention
• Inability to use CPAP despite standard fitting and troubleshooting, or any contraindication to CPAP treatment.
• Ongoing CPAP or OMT at inclusion

De-identified individual participant data underlying the results reported in publications from this trial will be shared. This will include baseline demographic and clinical characteristics, treatment allocation, adherence data for OMT and/or CPAP, sleep-study variables including apnea-hypopnea index (AHI), oxygen desaturation index (ODI), oxygen saturation nadir, mandibular excursion measurements, questionnaire data including ESS and PSQI scores, dento-occlusal and temporomandibular assessment data, anthropometric measures, and follow-up outcome data collected at the protocol-defined study visits.

Beginning 6 months after publication of the primary results manuscript or, if no publication occurs, 12 months after study completion, and ending 5 years thereafter.

De-identified individual participant data and supporting documents will be made available to qualified researchers who provide a methodologically sound research proposal. Requests will be reviewed by the study investigators and sponsor institution for scientific merit, feasibility, consistency with participant consent, ethics requirements, and compliance with applicable data-protection regulations. Approved requestors will receive access only to the data necessary for the approved analyses, after signing a data access and confidentiality agreement. Data will be shared in de-identified form through a secure controlled-access process coordinated by the study team.

Mandibular excursion assessors and polysomnography scorers will remain blinded to treatment allocation. Participants cannot be blinded to CPAP exposure; however, sham follow-up visits will mimic the intensity of OMT follow-up to reduce performance bias.