GSTM1 and anemia: Median Hb values were 13.4 (IQR: 12.7–14.2) g/dl, 11.6 (11.3–11.9) g/dl, and 9.7 (8.7–10.4) g/dl in the no anemia, mild anemia, and moderate/severe anemia groups, respectively (P < 0.001).