A study of the prevalence of restless legs syndrome in previously untreated Parkinson's disease patients: absence of co-morbid association.

Abstract OBJECTIVE: The co-morbidity between Parkinson's disease (PD) and restless legs syndrome (RLS) is currently controversial, mainly because in most of the studies so far conducted, the patients were already on therapy with dopamine(DA)ergic drugs. This study has been carried out to assess the prevalence of RLS in de novo PD patients previously unexposed to DAergic drugs. METHODS: One hundred nine cognitively unimpaired outpatients with PD (70M/39F), mean age 66.89 years±9.37 SD were included in the study. The mean duration of PD was 15.81 months±11.24 SD, and the median Hoehn and Yahr (H&Y) stage was 2 (range 1.5-3). All patients underwent interview to assess the occurrence of overall life-time and current "primary" form of RLS according to the criteria of the International RLS Study Group (IRLSSG). One hundred sixteen age and sex matched subjects (74M/42F, mean age 66.52.years±8.65 SD) free from a history of neurological diseases, were taken as controls and likewise interviewed. "Secondary" forms of RLS in both patients and controls were subsequently excluded. RESULTS: No significant difference was found (chi-square test) in the frequency of overall life-time and of current "primary" RLS between PD patients and controls (6 out of 109 versus 5 out of 116 and 3 out of 109 versus 3 out of 116, respectively). CONCLUSIONS: This survey does not support the concept of a co-morbid association between the two conditions and confirm indirectly the findings of previous studies reporting the onset of RLS after diagnosis of PD has been made in the great majority of patients and so likely on ongoing DAergic treatment. Therefore, we speculate that RLS occurring in these patients could be related to DAergic therapy for PD.