Residual periodic limb movement index after CPAP therapy is associated with hypoxemia.

Study objectives: Periodic limb movements during sleep (PLMS) frequently coexist with obstructive sleep apnea (OSA), yet the impact of CPAP treatment on PLMS remains unclear. This study investigates factors associated persistence of periodic limb movement index (PLMI) during CPAP therapy.

Methods: A retrospective cross-sectional study analyzed data from 107 adult patients who underwent split polysomnographic studies. Participants were classified into four groups based on PLMI changes: normal PLMI throughout (Group 1), persistent elevated PLMI (Group 2), worsened PLMI (Group 3), and resolved PLMI (Group 4). Predictors of PLMI persistence, including sleep architecture, oxygen desaturation, age, and BMI, were assessed using logistic regression analysis.

Results: 36.1% of patients experienced resolution of elevated PLMI, 16.4% showed worsening, and 47.5% had persistent PLMI despite CPAP therapy. Logistic regression analysis revealed that male sex (OR = 5.38, 95% CI [1.64-17.61], p = 0.005), higher BMI (OR = 1.09, 95% CI [1.01-1.17], p = 0.018), and greater time spent with oxygen saturation ≤88% during the diagnostic portion (OR = 1.034, 95% CI [1.002-1.066], p = 0.035) were significant predictors of residual PLMI. Sleep architecture variables such as total sleep time, sleep efficiency, and sleep stage distribution were not independently associated with residual PLMI.

Conclusions: Residual periodic limb movements during CPAP therapy are common and are independently associated with male sex, higher BMI, and greater hypoxemia during the diagnostic portion of sleep.