Nocturnal Hypoxemia and Airway Phenotype in Adults with Cancer: An Exploratory Case–Control Study

Background/Objectives: Human breathing occurs through either the nasal or the oral route. Nasal breathing is the physiological mode of ventilation and contributes to nitric oxide delivery, upper-airway regulation, and efficient pulmonary gas exchange. In contrast, chronic oral breathing has been associated with upper-airway dysfunction, impaired nocturnal oxygenation, and chronic intermittent hypoxia, conditions increasingly associated with cardiovascular, metabolic, respiratory, neurocognitive, and oncological diseases. To determine whether adults with cancer exhibit structural and functional craniofacial characteristics associated with oral breathing patterns and altered nocturnal oxygenation. Methods: We conducted an exploratory case–control study including adults with cancer and matched controls. Participants underwent a standardized multidimensional airway assessment comprising symptom evaluation using the STOP-BANG questionnaire, structured clinical examination of upper-airway and orofacial characteristics, craniofacial assessment, cone-beam computed tomography (CBCT), and home respiratory polygraphy to characterize upper-airway phenotype and nocturnal oxygenation patterns. Results: Adults with cancer exhibited impaired nocturnal oxygenation despite comparable apnea–hypopnea index values. They also exhibited a higher prevalence of structural and functional upper-airway abnormalities, including restricted tongue mobility, anterior open bite, and reduced maxillary transverse dimensions. Conclusions: This exploratory study identifies a distinct upper-airway phenotype in adults with cancer, characterized by craniofacial and functional features associated with impaired nocturnal oxygenation. These findings suggest that upper-airway anatomy and nocturnal oxygenation may contribute to systemic disease vulnerability and warrant further investigation.