GSTM1 and anemia (phenotype): More generally and at a global level, the use of the WHO age-independent cutoff is the reason that the highest anemia prevalence is found in preschool children[37], because the lowest Hb levels are at 6 to 11 months old and values increase with age[47,68,69] as shown in NHANES II and Peruvian population (Table 1).