In addition, a recent meta-analysis has shown a significantly higher prevalence of RLS in patients with PD than in controls [36], and a genetic case-control association study of cases and controls has shown a decreased risk for RLS in carriers of the longest-size-variant allele (allele 2) of the complex microsatellite repeat Rep1 within the α-synuclein gen (SNCA, PARK1) [37]. This evidence concerns the gene SNCA and Parkinson disease.