Polysomnographic Phenotype of Positional Obstructive Sleep Apnea.

Background and objectives: Obstructive sleep apnea (OSA) is a prevalent sleep disorder characterized by recurrent upper airway obstruction, leading to disrupted sleep and various health complications. Positional OSA (POSA) refers to patients whose OSA severity is significantly influenced by body position, especially when lying supine. This study aimed to evaluate the polysomnographic characteristics of POSA and non-positional OSA (non-POSA) and to assess their clinical implications.

Methods: This retrospective study included patients diagnosed with OSA who underwent type 1 polysomnography. Patients were categorized into POSA and non-POSA groups based on whether their apnea-hypopnea index (AHI) in the supine position was at least twice as high as that in the lateral position. We collected and analyzed clinical and polysomnographic parameters, including AHI, oxygen desaturation index, arousal index, nadir peripheral oxygen saturation (SpO₂), and sleep position proportions. These were compared across different OSA severity levels-mild, moderate, and severe-to assess differences between the POSA and non-POSA groups.

Results: In total, 500 patients with OSA were analyzed, of whom 63.4% were classified as having POSA. Patients with POSA exhibited milder disease severity than those without, with an average AHI of 23.3±15.3/h versus 43.9±27.9/h, respectively, and a higher nadir SpO₂ of 82.8%±6.6% versus 77.1%±9.8%. POSA was more common in patients with mild OSA (76.5%) and moderate OSA (72.8%), while severe OSA cases were predominantly non-POSA (POSA was 47.4%). Moreover, patients with POSA spent significantly more sleep time in the lateral position (43.8%±22.7%) than non-POSA patients (27.2%±28.2%).

Conclusion: Patients with POSA generally exhibited milder disease and more favorable polysomnographic profiles than non-POSA patients. POSA is prevalent in mild-to-moderate OSA, and identifying it via polysomnography may inform tailored treatment strategies.