In a further study of prognosis, Facheris et al looked at four SNPs in the SLC2A9 locus, and their association with age at onset in 664 PD patients of European ancestry, and found one SNP to be associated with a mean difference in age at onset of −4.56 (95% CI, −8.13 to −1.00) per urate-decreasing allele.18 These studies, undertaken in patients that already have PD, may not be directly comparable with our research findings because, as already mentioned, risk factors for disease may differ from those that affect timing of disease diagnosis and its progression. Here, SLC2A9 is linked to Parkinson disease.