Background: The frequency of RLS in Parkinson's disease (PD) patients has been reported to be between 10% and 26%. Several hypotheses have sought to link these two diseases; however, the pathophysiology of RLS in PD patients has yet to be completely defined. Many patients with idiopathic RLS have low serum ferritin levels, which negatively influence RLS symptomatology. Our objective was to investigate the role of iron deficiency in PD patients with and without RLS.
Methods: We consecutively included 42 PD inpatients undergoing pharmacological treatment. Patients with anemia, renal insufficiency, or polyneuropathy were excluded from the study. The control group consisted of 42 PD inpatients without RLS (PD-nonRLS), matched for age and severity of PD. RLS was diagnosed clinically according to diagnostic criteria. Serum ferritin levels were measured at admission for all patients.
Results: Mean serum ferritin values were 142.20 ± 91.17 ng/dL for PD patients with RLS (PD+RLS) and 160.65 ± 142.57 ng/dL in PD-nonRLS (P = 0.704). There was no difference concerning the total dopaminergic dose (levodopa equivalent dose) between PD+RLS and PD-nonRLS patients (828.22 ± 389.02 vs. 775.32 ± 324.69 mg; P = 0.501). The frequency of dopamine agonist (DA) use did not differ between the two groups (P = 0.306).
Conclusions: There were no significant differences in serum ferritin levels between PD+RLS and PD-nonRLS in our study. This suggests a different pathophysiology of RLS in PD patients, where iron deficiency is not necessarily observed. DA use was not found to be associated with the occurrence of RLS symptoms.
Keywords: Parkinson's disease; ferritin; iron; restless legs syndrome (RLS).