Hb levels decreased in the malaria groups (n = 42, 48 and 44, p<0.001), with mean values of 93.98 g/dl (SD = 14.77 g/dl) for UM, 75.96 g/dl (SD = 16.48 g/dl) for HM and 64.34 g/dl (SD = 22.99 g/dl) for SM. This evidence concerns the gene GSTM1 and malaria.