These genetic studies support the protective effect of caffeine intake on PD through the interaction between caffeine and GRIN2A, LRRK2, and A2AR. These findings raise the exciting possibility of selecting patient subpopulations by these genetic polymorphisms of the GRIN2A, LRRK2, A2AR, and CYP1A1 genes. This evidence concerns the gene LRRK2 and Parkinson disease.