The influence of sex, age and sleep wake state on characteristics of periodic leg movements in restless legs syndrome patients

Restless legs syndrome (RLS) patients experience periodic stereotyped leg m ovements while awake and during sleep. The aim of the present study was to measure the effects of sex, age and the sleep/wake state on several charact eristics (frequency, duration and periodicity) of these periodic leg moveme nts (PLM). One hundred unrelated patients diagnosed with primary RLS were s tudied. During wakefulness, frequency of PLM increased and the mean inter-m ovement interval decreased with advancing age. The modal value of inter-mov ement interval distribution was also altered suggesting that aging influenc es rhythm-generation mechanisms. Sleep/wake states had a profound effect on leg movement characteristics. Movements of longer duration were seen durin g wakefulness, while REM sleep was characterized by the shorter duration an d the lowest frequency of PLM, due most likely to the inhibition of spinal motoneurons that prevails in REF I sleep. States of vigilance also modulate d the periodicity of PLM. Intervals were shorter during wakefulness and inc reased progressively from stage 1 to stage 2 sleep, and to slow wave sleep (SWS). During REM, the duration of sleep intervals returned to values obtai ned in stage 1 sleep; these two stages sharing similar patterns of EEG acti vity. These results indicate that a single state dependent mechanism may be responsible for the periodicity of PLM noted both during sleep and wakeful ness. (C) 1999 Elsevier Science Inland Ltd. All rights reserved.