PPARD and glioma: A seven-locus model including polymorphisms of PPARD (rs2016520, rs67056409, rs1053049 and rs2206030) and PPARG (rs2920503, rs4073770 and rs1151988) was the best model of SNP-SNP interaction for glioma risk (cross-validation consistency = 10/10, accuracy = 0.660, sensitivity = 0.751, specificity = 0.570, P < 0.001).