DRD4 and Parkinson disease: By contrast, Paus and colleagues examined 204 PD patients (102 with sleep attacks matched to 102 without sleep attacks, with the same dopaminergic treatment) and did not find any significant association between sleep attacks and 141 C del/ins, rs1800497 SNPs both in DRD2, and rs6280 SNP in DRD3. However, the authors found higher frequency of homozygosis of 48-bp VNTR with two repeats in DRD4 among patients with sleep attacks without warning signs, concluding that this allele may represent a risk factor for sleep attacks in PD patients on dopaminergic drugs [117].