Periodic limb movements of sleep: A comparison of REM and NREM

It is known that periodic limb movements of sleep (PLMS) impact various sleep parameters. Utilizing polysomnographic (PSG) data from a large set of retrospective records, we aimed to identify and describe differences in sleep efficiency comparing PLMS occurring in both rapid eye movement (REM) sleep and non-REM (NREM) sleep with PLMS occurring only in NREM sleep.

This was a retrospective analysis of consecutive full-night PSGs performed on adults (≥18) presenting for the clinical evaluation of insomnia, snoring, obstructive sleep apnea (OSA), PLMS, rapid eye movement (REM) behavior disorder (RBD), and other sleep disorders, at one institution, over a period of three years. The database of records was queried and the records were assembled into one of three groups: 1. Controls (those without notated sleep disorder diagnoses), 2. PLMS in NREM (those with PLMS found only in NREM sleep), and 3. PLMS in REM/NREM (those with PLMS found in both REM and NREM sleep). The PSG parameters of each group were then compiled and statistically evaluated.

A total of 4110 records were examined; 1635 were labeled as Controls, 1012 as PLMS in NREM, and 528 as PLMS in REM/NREM. Compared to PLMS in REM/NREM (76.1 ± 16.0%) and Controls (79.5 ± 17.3%), there was a significant reduction in sleep efficiency in PLMS in NREM (70.1 ± 19.5%) (p < 0.05). There were significantly more PLM arousals in both groups compared to Controls (0.5 ± 1.7/hr); the PLMS in NREM group demonstrated the highest index (2.5 ± 4.2/hr), followed by PLMS in REM/NREM (2.1 ± 3.8/hr).

It seems that the PLMS in which occur in NREM sleep may play a role in reducing sleep efficiency, perhaps through elevated PLM arousals, as compared to PLMS that occur in both REM and NREM sleep. Future research should consider these factors and explore longitudinal outcomes to understand better the long-term impact of PLMS.