GSTM1 and type 2 diabetes mellitus: Data of 4095 and 1273 T2DM patients in study 1 and study 2, respectively, were extracted from the database based on the following conditions: (i) began treatment with a single OHA (sulfonylurea, biguanide, thiazolidinedione, α-glucosidase inhibitor, glinide, or dipeptidyl peptidase-4 inhibitor) and continued the medication for ~1–1.4 years; (ii) hemoglobin (Hb)A1c level at baseline was available; (iii) age at baseline was 40–70 years; (iv) presence or absence of CVD history was not considered in study 1, but presence of CVD history was considered in study 2.