Interestingly, a dual-null GSTM1–GSTT1 genotype was associated with bladder cancer risk in the overall population and in Asians (overall population: OR = 1.48, 95% CI: 1.15–1.92, P = 0.002; Asians: OR = 1.62, 95% CI: 1.15–2.28, P = 0.006). This evidence concerns the gene GSTM1 and urinary bladder cancer.