Moderate anaemia (Hb = 7.0–9.9 g/dL) occurred commonly (60.6%, 95% CI = 55.7–65.3%) in the participants than mild (13.0%, 95% CI = 10.3–16.6%) and severe anaemia (1.8%, 95% CI = 0.9–3.6%). This evidence concerns the gene GSTM1 and anemia (phenotype).