Patients were divided into four groups according to anemia level: (1) hemoglobin (Hb) < 7 mg/dl (n = 80), (2) Hb 7–9.9 mg/dl (n = 320), (3) Hb 10–10.9 mg/dl (n = 1300), and (4) Hb > 11 mg/dl (n = 3100, control group). Here, GSTM1 is linked to anemia.