OBJECTIVES: Periodic limb movement disorder (PLMD) has been debated with regard to its clinical significance and diagnostic criteria. The current diagnostic criterion for PLMD in adults has been changed from periodic limb movement index (PLMI) > 5/ hour to PLMI > 15/hour by the International Classification of Sleep Disorders (ICSD). In this study, we aimed to investigate the changes in polysomnographic sleep variables according to PLMI and to determine the relevance of the diagnostic criterion for PLMD. METHODS: Out of 4195 subjects who underwent standard polysomnography, we selected 666 subjects (370 males and 296 females, aged 47.1 ± 14.8) who were older than 17 years and were not diagnosed with primary insomnia, sleep apnea, narcolepsy, or REM sleep behavior disorder. Subjects were divided into three groups according to PLMI severity: group 1 (PLMI ≤ 5), group 2 (5 < PLMI ≤ 15), and group 3 (PLMI > 15). Demographic and polysomnographic sleep variables and Epworth sleepiness scale (ESS) were compared among the three groups. RESULTS: There were significant differences among the three groups in age and gender. Sleep efficiency (SE) and stage 3 sleep percentage in group 1 were significantly higher than those in groups 2 and 3. The wake after sleep onset (WASO) score in group 1 was significantly lower than those in groups 2 and 3. However, there were no significant differences in SE, stage 3 sleep percentage, or WASO between groups 2 and 3. Sleep latency (SL) in group 1 was significantly lower than that in group 3, but there was no difference in SL between group 2 and group 3. ESS score in group 1 was significantly higher than that in group 3, but there was no difference between group 2 and group 3. Partial correlation analysis adjusted by age showed that PLMI was significantly related to SE and WASO. CONCLUSION: This study suggests that PLMI influences polysomnographic sleep variables. In addition, we found the individuals who did not have PLMD but had PLMI > 5 were not different in polysomnographic sleep variables from the individuals who had PLMD according to the current criterion. These results raise questions about the relevance of the current diagnostic criterion of PLMD.
Adult ; Classification ; Extremities* ; Female ; Humans ; Male ; Narcolepsy ; Nocturnal Myoclonus Syndrome ; Polysomnography ; REM Sleep Behavior Disorder ; Sleep Apnea Syndromes ; Sleep Initiation and Maintenance Disorders ; Sleep Wake Disorders