LRRK2 and Parkinson disease: In conclusion, our study highlighted evidence of similar regional linkage disequilibrium of LRRK2 among CEU and INS, and among JPT, CHS and CHB, suggesting that there is a higher likelihood to detect the association between PD and those trait-associated SNPs of LRRK2 gene found in Caucasian studies in INS, those LRRK2 SNPs found in Japanese studies are likely to be better replicated among CHB when allelic frequencies are similar in Caucasians and INS, or in JPT and CHB, respectively.