Abstract

Background: Nasal obstruction has been implicated in the pathophysiology of obstructive sleep apnoea (OSA), potentially contributing to upper airway instability and impaired breathing during sleep. However, its precise role in determining disease severity remains unclear. This study aimed to evaluate the relationship between patients’ subjective perception of breathing patterns (nasal vs. oral) and OSA severity, as well as the impact of structural nasal abnormalities and their anatomical location. Methods: This cross-sectional study was conducted at the University Hospital Center Osijek, Croatia, between May 2024 and September 2025. Sixty adult patients with diagnosed moderate-to-severe OSA (apnoea–hypopnoea index [AHI] ≥ 15 events/hour) were included. All participants underwent polysomnography and otorhinolaryngological evaluation, including anterior rhinoscopy and nasal endoscopy. Structural abnormalities assessed included septal deviation and inferior turbinate hypertrophy, classified according to a modified Cottle system. Statistical analyses were performed using non-parametric tests and correlation methods, with significance set at p < 0.05. Results: The study included 60 patients (median age 56 years; 71.7% male), of whom 23% had moderate and 77% severe OSA (median AHI 39.4). No significant association was found between subjective breathing pattern and OSA severity (p = 0.8), although patients with predominantly oral breathing exhibited higher median AHI values. Oral breathing was significantly associated with the presence of septal deviation (p < 0.001) and inferior turbinate hypertrophy (p < 0.001). Structural deformities in oral breathers were most frequently localized in the nasal valve region (Area II) (p < 0.001). However, neither the presence nor the anatomical location of nasal deformities showed a significant relationship with AHI values (p = 0.93). Conclusions: Subjective breathing pattern was not significantly associated with OSA severity, although oral breathing tended to be linked with higher AHI values. Structural nasal abnormalities were significantly more prevalent among oral breathers but did not influence disease severity. These findings suggest that nasal obstruction plays a limited role in determining OSA severity, while remaining clinically relevant as a potentially modifiable factor influencing breathing patterns and treatment adherence. Further research is warranted to evaluate the impact of interventions targeting nasal breathing in the comprehensive management of OSA.

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