Comparison of clinical features and surgical outcomes between hypopnea- and apnea-predominant obstructive sleep apnea

Objectives: This study is aimed to investigate the differences in the clinical features and surgical outcomes between hypopnea- and apnea-predominant obstructive sleep apnea (OSA).

Design: Cohort study.

Setting: Single tertiary care centre.

Participants: This study included 190 patients with OSA who underwent multilevel upper airway surgery between September 2012 and September 2021. The patients were divided into two groups according to the proportion of each respiratory event: hypopnea-predominant (n = 102) and apnea-predominant (n = 88).

Main outcome measures: The primary outcome measure was the percentage improvement in the apnea-hypopnea index (AHI) from baseline AHI after surgery.

Results: The apnea-predominant group included more male patients and had higher AHI, respiratory disturbance index (RDI) and oxygen desaturation index (ODI) than the hypopnea-predominant group. Both groups showed significant improvements in AHI, apnea index, RDI, supine AHI, REM AHI, non-REM AHI, ODI, lowest O₂ saturation and Epworth Sleepiness Scale scores following the surgery. Notably, hypopnea index increased after surgery in the apnea-predominant OSA group. Although the improvement in the absolute value of AHI by surgery was significantly greater in the apnea-predominant group than in the hypopnea-predominant group, the two groups showed no significant difference in the percentage improvement in AHI from baseline AHI.

Conclusion: Patients with apnea-predominant OSA had more severe disease than those with hypopnea-predominant OSA; however, surgical outcomes, as evaluated by percentage AHI improvement, were comparable between the two groups. In addition, multilevel upper airway surgery may induce the transition from apnea to hypopnea in patients with apnea-predominant OSA.