0789 Associations Between Obstructive Sleep Apnea and Periodic Limb Movements in a Pediatric Cohort with Elevated PLMD Index

Abstract Introduction Although prior studies suggest a bidirectional or masking relationship between obstructive sleep apnea (OSA) and elevated periodic limb movement index (PLMI), the true interaction between respiratory disturbance severity and limb movement activity in pediatric populations remains unclear. The aims of this study were to (1) compare demographic, clinical, and polysomnographic characteristics of children with elevated PLMI stratified by OSA severity; (2) evaluate the association between OSA and PLMI; and (3) identify independent predictors of PLMI. Methods This was a retrospective study involved children ≤18 years with elevated PLMI ( 5 events/h) at a tertiary pediatric sleep center from 2020–2024. OSA severity was categorized by obstructive apnea-hypopnea index (OAHI) as normal ( 1.5 events/h), mild (1.5–4.9 events/h), moderate (5–9.9 events/h), and severe (≥ 10 events/h). Results Out of 4,571 studies in 4 years, 542 children (12.0%) had an elevated PLMI, of which 223 (41%) had no OSA, and 319 (59%) had OSA. Race distribution, BMI z-score, and tonsillar grade differed significantly across OSA severity groups (p 0.01). Restless legs syndrome, restless sleep, and PLMI ≥10/h were more prevalent in OSA, increasing with OSA severity (p=0.024, p 0.0001, and p 0.0001, respectively). The median PLMI was significantly higher in OSA vs. non-OSA (10.4 vs. 8.0 events/hr, p 0.0001). Total PLMS and PLMI increased progressively across OSA severity categories (p=0.004 and p 0.0001). Iron indices did not differ between groups. OAHI showed a significant positive correlation with the PLMI (r=0.198, p 0.0001). For every 1-unit increase in OAHI, the PLMI increases by a factor of exp (0.01) = 1.01 (or 1%). In multivariable modeling, higher OAHI (β=0.010, p 0.001) and use of antihistamines or SSRIs (β=0.27, p=0.003) independently predicted higher PLMI, whereas female sex predicted a lower PLMI (β=–0.11, p=0.029). Conclusion In children with elevated PLMI, OSA is associated with higher PLMI burden, higher PLMI, and increased prevalence of restless sleep and RLS symptoms. Although the correlation between OAHI and PLMI is modest, OSA severity independently predicts PLMI after adjustment for confounders. These findings suggest a clinically meaningful link between respiratory obstruction and limb-movement activity in pediatric sleep disorders. Support (if any)