Periodic leg movements in RLS patients as compared to controls: Are there differences beyond the PLM index?

OBJECTIVE: To characterize periodic leg movements (PLM) and their association with sleep disturbances in drug-free patients with restless legs syndrome (RLS) and healthy subjects without sleep complaints.

METHODS: Polysomnographic recordings of 95 patients with idiopathic RLS and 31 age-matched controls were compared, and correlation analysis between sleep efficiency and PLM variables was performed. All patients and controls were free of medication for 10 days prior to polysomnography.

RESULTS: PLM measures revealed a significantly longer mean duration of single PLM during wakefulness and non rapid eye movement (NREM) sleep in RLS patients as compared to controls. PLM indices were higher in RLS patients than in controls during all sleep stages, but not during wakefulness and slow wave sleep. A significantly higher number of PLM sequences was found in RLS patients than in controls. In RLS patients decreased sleep efficiency was associated with a higher number and a shorter duration of PLM sequences.

CONCLUSIONS: The mean duration of single PLM might be an appropriate parameter to discriminate between healthy subjects with PLM and patients with RLS. High numbers of PLM sequences of short duration might be an indicator for the decreased sleep quality in RLS patients.