Different diagnostic criteria for periodic leg movements in patients with obstructive sleep apnea after continuous positive airway pressure titration

OBJECTIVE: Periodic leg movement in sleep (PLMS) is common among patients with obstructive sleep apnea (OSA). The PLMS frequency changes after continuous positive airway pressure (CPAP) titration. This study investigated the effects of two PLMS diagnostic criteria on PLMS prevalence and the restless leg syndrome (RLS) detection rate in patients with OSA before and after CPAP titration. METHODS: This retrospective study included patients with OSA who received polysomnography (PSG) and successful CPAP titration from December 2012 to December 2014. Their clinical variables and sleep parameters were evaluated using the PLMS diagnostic criteria: PLMS index (PLMI) ≥5 and ≥15. PLMS prevalence and the RLS detection rate were analyzed according to the PLMI before and after CPAP. RESULTS: In patients with OSA with a PLMI of ≥5 and ≥15 after PSG with CPAP titration, the PLMS prevalence was 20.1% (76/378) and 4.5% (17/378), respectively, which revealed CPAP titration increased PLMI. Moreover, in terms of PLMI ≥5 and ≥15, PSG with CPAP titration led to significantly higher PLMS prevalence than PSG alone (20.1% vs 7.1% and 4.5% vs 0.8%, respectively; both P<0.001). PLMI ≥5 also demonstrated a higher RLS detection rate than PLMI ≥15 did (69.2% vs 15.4%; P=0.016). CONCLUSION: In patients with OSA, CPAP titration increases PLMS prevalence and the PLMI regardless of whether PLMI is ≥5 or ≥15. The use of the current diagnostic criteria, PLMI ≥15, for PLMS may lead to underestimation of PLMS prevalence and the RLS detection rate in patients with OSA.