Several factors could provide plausible explanations that we failed to observe any association with susceptibility to PD for promoter polymorphisms of NFE2L2, e.g., (1) possible genetic differences between different ethnic groups; (2) different study designs and possible biases in recruiting case and normal controls among studies; (3) and the statistical approach in the previous studies did not account for significance testing, raising the possibility of a false positive result. The gene discussed is NFE2L2; the disease is Parkinson disease.