PLMS is associated with low arousal threshold and favorable upper airway patency in patients with OSA

Periodic limb movements during sleep (PLMS) in patients with obstructive sleep apnea (OSA) increases the complexity of disease management. However, pathological mechanisms linking OSA and PLMS have remained unclear. This study aims to compare the endotypic traits of sleep apnea in patients with combined PLMS (OSA-PLMS) versus those with OSA alone.

A total of 1008 adults with moderate-to-severe OSA were prospectively recruited from a single sleep center at which they underwent in-laboratory full-night polysomnographic studies. Periodic limb movements were manually scored, and endotypic traits - including arousal threshold, loop gain, upper airway collapsibility, and compensation - were retrieved from polysomnographic studies. Linear regression models were conducted to examine the associations between OSA-PLMS and endotypic traits.

Compared to the OSA-only group, patients in the OSA-PLMS group were older, had a lower body mass index, and showed a higher prevalence of heart diseases. Additionally, they experienced less snoring, a lower apnea-hypopnea index, a higher hypopnea fraction, and shorter apnea durations. After adjustment, OSA-PLMS patients showed 16.2 %eupnea lower arousal threshold, 5.4 %eupnea higher V_passive, 6.1 %eupnea higher compensation, 2.6 s shorter apnea duration, and 24.6 min%/h lower hypoxic burden compared to OSA-only patients.

Patients with OSA-PLMS demonstrated a less collapsible upper airway, better muscle recruitment ability, and lower arousal threshold compared to OSA-only.