HLA-DRB1 and Parkinson disease: Using stratification analyses and unconditional logistic regression analysis adjusted for gender, we found that the positive association between HLA-DRB1*0301 and PD risk was independent of onset age(onset age ≤50:OR = 3.350, P = 4.039E-4, onset age >50: OR = 1.726, P = 0.007).