, mild anemia group (Hb levels: > 90 g/L, ≤ 130 g/L for males and ≤ 120 g/L for females), and moderate anemia group (Hb levels: between 60 g/L and 90 g/L), where an OR of < 1 suggests that the factor is a protective factor. This evidence concerns the gene GSTM1 and anemia (phenotype).