Developmental and neurophysiologic deficits in iron deficiency in children

Abstract

Introduction: Several studies in animals and humans have clearly demonstrated the effect of ID on development, cognition, behavior and neurophysiology. The effect of ID have been shown: on brain metabolism, neurotransmitter function, and myelination. Changes in brain iron content caused by early ID in animals are not reversible by iron therapy, inspite of correction of anemia and other tissue deficits and result in changes in behavior which continue into adulthood. ID has repercussions in the perinatal period, infancy and childhood. Some effects are irreversible while other defects may be corrected: timing of ID in a child may be critical.

Developmental deficits: Children (6-23 months) with moderate to severe anemia (ID) or chronic anemia (>3 months) had lower mental and psychomotor development scores than the nonanemic, and except for some continued to have lower scores in spite of iron therapy for 3 months although anemia was corrected. The deficits persisted on re-evaluation at 5, 11-14, and at 19 years.

Scholastic achievement: Scholastic achievement is lower and ID children are twice more likely to have problems with mathematics. Ten year follow-up indicated special educational assistance was required for initially anemic children. ID affects WICS items of information, comprehension and verbal performance and full scale IQ. EEG power spectrum had a slower activity suggesting developmental lag compared to iron sufficient children. Treatment with iron improved IQ scores significantly; other studies found differential effects: improvement in cognition and mental scores in older but not in younger children. IQ levels are affected by ID: IQ at 4 years may be predicted by hemoglobin at 5 and 36 months.

Neurophysiological deficits: Abnormal Evoked Response Potentials (ERPs):ABRs and VEPs are seen in ID, which persist in children who were anemic in infancy on retesting at 4 years. Differences have been consistently found in ID infants and in older children. Iron supplementation may significantly reduce latencies of some ERPs. ID affects newborn temperament, ERPs and recognition memory. Iron supplementation in infants (<1,301 g) improved neurocognitive and psychomotor development by 5.3 years (median age). Preventive iron supplementation in well nourished infants also show a positive effect on motor development. The changes are usually subtle, however, with prevalence of anemia of 79.2% in children 6-35 months and 57.9% in pregnant women (NFHS-3, 2005-06), the adverse effects of cognitive, development and behavioral defects should not be underestimated.