Hemoglobin Status Associated with Performance IQ but Not Verbal IQ in Chinese Preschool Children

Background: Despite the body of literature that links anemia with poorer cognition in children and the evidence that the severity of the effects of anemia on children's cognition vary in different populations, few studies have investigated the effects of anemia on the cognitive development of Chinese children.

Methods: This longitudinal cohort included 171 children from a developing region of China. Hemoglobin (Hb) and iron levels were taken when the children were 4 years old. At age 6, the children's cognition was tested with the Chinese Wechsler Preschool and Primary Scale of Intelligence. Psychosocial information was also used in analyses.

Results: Results showed that the children who had low Hb levels had significantly lower scores in performance IQ (PIQ), but not verbal IQ. Although blood Fe levels were not shown to moderate the link between Hb levels and IQ, we found children who performed the best on IQ tests exhibited low iron levels concurrent with high Hb levels, whereas the group who performed the worst exhibited high iron but low Hb levels. We also found that psychosocial adversity did not differ significantly between children who had normal or low Hb levels, although the effect of Hb on PIQ became only suggestive after controlling for psychosocial adversity, therefore the correlation is not causal but only a suggestive association.

Conclusion: Our findings are in agreement with literature on the negative effects of anemia on children's cognition and point to the possibility that the portions of the brain associated with PIQ components are particularly affected by low Hb during crucial periods of development.