CYP2D6 and Parkinson disease: In the subgroup analysis stratified by ethnicity, the results also showed a significant contribution of the CYP2D6*4 allele polymorphism to PD development in the Caucasian population in all of the comparisons of the A vs. G allele (OR = 1.28, 95% CI = 1.13–1.44, P = 0.001); AA vs. GG (OR = 1.45, 95% CI = 1.07–1.96, P = 0.017); AG vs. GG (OR = 1.21, 95% CI = 1.05–1.40, P = 0.009); AG+AA vs. GG (OR = 1.26, 95% CI = 1.09–1.44, P = 0.001); and AA vs. AG+GG (OR = 1.37, 95% CI = 1.02–1.86, P = 0.034).