Background Respiratory event duration is an observable phenotype of obstructive sleep apnea (OSA) in routine polysomnographic studies and is relatively longer in Asian patients. This study examined the association of respiratory event duration with OSA severity and endotypes in Asian patients with moderate-to-severe OSA. Methods We recruited 1008 patients who underwent in-laboratory full-night polysomnographic studies. Event durations were averaged during NREM and REM sleep, respectively. The associations of event duration with endotypes (including arousal threshold, loop gain, circulatory delay, upper airway collapsibility, and compensation) and OSA severity (apnea-hypopnea index AHI and hypoxic burden) were examined. Results Participants demonstrated a mean event duration of 25.9 s in NREM sleep. Event duration exhibited an inverse U-shaped association with AHI during NREM sleep (peaking at 26.8 s) and a negative association with AHI during REM sleep, whereas hypoxic burden consistently increased with longer event durations. After adjusting for AHI, a one-second increase in event duration during NREM sleep was associated with a 3.46%eupnea (95% CI: 3.20–3.73) higher arousal threshold, 1.26%eupnea (95% CI: 1.13–1.39) worse collapsibility (V passive ), 0.61%eupnea (95% CI: 0.40–0.83) lower compensation, 0.07 s (95% CI: 0.05–0.08) higher delay, and 7.43%min·h −1 (95% CI: 6.56–8.30) higher hypoxic burden. In REM sleep, event duration was positively associated with arousal threshold, loop gain, and hypoxic burden, but negatively associated with V passive and compensation. Conclusions A high arousal threshold, a collapsible upper airway, and poor compensatory function characterize long event durations in patients with OSA. AHI does not adequately reflect the disease burden associated with hypoxia caused by prolonged respiratory events.
Shiao et al. (Thu,) studied this question.