GSTM1 and anemia: Heterozygote CA of p.Gln141Lys (rs2231142) variant increased risk of early anemia nearly 4 times (OR 3.72; 95% CI 1.30–10.66; p = 0.014), together with the presence of both GSTT1 and GSTM1 genes (OR 3.13; 95% CI 1.04–9.40; p = 0.041).