Time structure of leg movement activity during sleep in untreated Parkinson disease and effects of dopaminergic treatment

•PLMS index alone is a measure insufficient to describe their real periodicity.•Only few early-stage PD patients show PLMS; three quarters of them do not have PLMS.•Treated PD patients show sleep leg movements with no clear periodicity.•An interaction between PD pathology and PLMS genetic predisposition is speculated. Objectives: To evaluate the specific time structure of periodic leg movements during sleep (PLMS) in untreated Parkinson disease (PD) patients by means of an advanced analysis; and to evaluate the effects of treatment on this activity, in a cross-sectional comparison and in a prospective follow-up study, in a subgroup of previously untreated patients. Methods: Forty-four consecutive PD patients were enrolled in the study; 19 had not yet started any drug therapy for PD (PDnother); 10 out of these patients were re-evaluated after an average time lag of 19.6. months from baseline. The remaining 25 patients (PDther) were taking l-dopa and/or dopamine agonists. Eighteen age-matched normal controls were also included. All subjects underwent a polysomnographic recording and the time structure of their sleep leg movement activity was analyzed by means of the periodicity index and other advanced measures. Results: Both PD groups tended to show increased PLMS and decreased isolated limb movement activity with respect to controls. PLMS index >15/h was found in 26.3% of PDnother patients, 24.0% of PDther subjects, and in 16.7% of controls; none of the three PDnother patients who had PLMS index >15/h at baseline sustained this level at follow-up, nor did the other seven patients. The intermovement interval distribution showed a clear peak at 10-40. s in the PDnother group; a suppression of this peak was observed after the introduction of dopaminergic treatment in the subgroup of 10 PDnother patients. Both groups of PD patients showed a progressively decreasing number of PLMS through the night; an almost complete abolition of PLMS was seen in the first 2. h of sleep after the introduction of dopaminergic drug therapy. Conclusion: Our data do not seem to support the hypothesis that PLMS are particularly frequent in PD but seem to indicate an interaction between PD pathophysiology and genetic predisposition for PLMS, producing a slightly increased number of patients with this sleep motor phenomenon when compared to controls.