Clinical Significance of Periodic Limb Movement Disorder (PLMD) in Insomnia Patients

While periodic limb movement disorder (PLMD) in some studies has been linked with a range of negative consequences, others have questioned the validity of the diagnosis. The aim of the present study was to investigate the clinical significance of co-morbid PLMD in terms of daytime impairment in insomnia patients when defined in accordance with the new diagnostic criteria. 64 older adults complaining of insomnia (mean age = 61.9) were included in the study, and assessed with polysomnography, a sleep diary, the Epworth Sleepiness Scale, and a computerized vigilance test. In all, 28 patients had a PLM-index above 15 on at least one polysomnography registration; while the remaining 36 participants served as comparison group (comprising insomniacs patients without co-morbid PLMD). Adjusting for the potential confounding effects of demographics, apnea/hypopneas and symptoms of restless legs syndrome (RLS), we found no significant associations between PLMD and daytime sleepiness (measured with both subjective and objective measures). These findings illustrate that daytime symptoms of insomnia and PLMD may be difficult to distinguish, thus supporting the notion that the clinical significance of PLMD may be questionable.