Changes in the apnea index to hypopnea index ratio after upper airway stimulation therapy

Purpose: To examine the impact of upper airway stimulation therapy on the apnea index/hypopnea index ratio in patients with obstructive sleep apnea. Methods: We retrospectively analyzed 118 patients who received an upper airway stimulation device between 2015 and 2022. Results: The apnea–hypopnea index at baseline was 35.3 ± 8.9 events/hour, which significantly decreased to 14.9 ± 13.1 events/hour at three months and 14.9 ± 9.9 events/hour at twelve months (p < 0.001). The apnea index/hypopnea index ratio shifted from 1:1.3 at baseline to 1:2.3 and 1:2.4 at three and twelve months, respectively, indicating a greater reduction in apneas compared to hypopneas (p < 0.001). Conclusion: These findings suggest that upper airway stimulation therapy causes a shift from apneas to hypopneas, which may indicate that therapy prevents complete upper airway obstructions but may not fully prevent partial obstructions. These findings emphasize to look beyond overall apnea–hypopnea index reduction when evaluating the treatment effect of upper airway stimulation therapy.