Higher arousal threshold predicts hypoxic burden in OSA

A higher arousal threshold is associated with a more severe hypoxic burden in patients with obstructive sleep apnea (OSA) but shows a nonlinear correlation with apnea-hypopnea index (AHI), reveals a study.

A team of investigators prospectively recruited 1,167 adults with moderate-to-severe OSA from a sleep centre, who underwent in-laboratory full-night polysomnographic studies. They estimated endotypic traits—collapsibility (V_passive, ventilation at eupenic drive), loop gain, arousal threshold, and compensation—using polysomnographic signals and examined OSA severity by AHI and hypoxic burden.

Generalized additive models were used to visualize the associations between individual endotypic traits and OSA severity. Finally, the investigators explored the interaction between arousal threshold and compensation on OSA severity.

A more collapsible upper airway and higher loop gain demonstrated a linear association with greater OSA severity. Arousal threshold showed a positive association with hypoxic burden and an inverse U-shaped relationship with AHI.

A favourable upper airway patency was seen among patients with a relatively low arousal threshold (<173.5 %eupnea). Moreover, AHI increased with rising arousal threshold. The combination of a high arousal threshold and high compensation correlated with increased AHI during non-REM sleep, “where the high compensation resulted from a very low V_passive,” according to the investigators.

“Arousal threshold and compensation should be considered together when evaluating OSA severity,” they said.