Simon et al used MR to explore the effect of urate on PD progression; they used three SNPs in linkage disequilibrium in the SLC2A9 locus to stratify PD patients into three groups based on the number of risk alleles, and used time to initiation of levodopa treatment as the outcome in 735 PD patients of European descent.17 They observed a protective effect of urate on PD progression with a hazard ratio of 1.27 (95% CI = 1.00–1.61; p = 0.0497) for a 0.5-mg/dl genetically conferred decrease in serum urate. The gene discussed is SLC2A9; the disease is Parkinson disease.