Possible effect of periodic limb movements during sleep on the sleepiness of patients with sleep disordered breathing

We aimed to conduct a cross-sectional study in order to investigate the effect of periodic limb movements during sleep (PLMS) on daytime sleepiness in patients with sleep disordered breathing especially those with obstructive sleep apnea syndrome (OSAS), diagnosed by polysomnography (PSG). Our subjects included 233 male patients who visited our institute during the 25-month period between June 2012 and June 2013. We scored the number of Periodic Limb Movements per hour as the Periodic Limb Movements Index (PLMI) on standard PSG, and considered that periodic limb movements during sleep was present in the patients with PLMI >15/h. Non-PLMS group included those patients with PLMI <= 15/h. To assess the sleepiness of participants, we used Japanese version of the Epworth Sleepiness Scale (JESS) and Japanese version of the Pittsburgh Sleep Quality Index. We compared the sleep parameters and sleepiness indicators between patients with PLMS and age, apnea-hypopnea index (AHI), and body mass index-matched non-PLMS control groups. JESS scores were higher in patients with PLMS than in non-PLMS in both low AHI (<15/h) and high AHI (>= 15/h) strata. However, the difference was statistically significant only in high AHI stratum (P = 0.399 and 0.001, respectively). In conclusion, PLMS was associated with increased JESS especially in patients with moderate-to-severe OSAS. Although the magnitude of the difference in those with AHI <15/h was smaller and statistically insignificant in the present study, this issue warrants further investigation by enrolling more patients with AHI <15/h.