Iron deficiency and cognitive achievement among school-aged children and adolescents in the United States

Context. Iron deficiency anemia in infants can cause developmental problems . However, the relationship between iron status and cognitive achievement i n older children is less clear. Objective. To investigate the relationship between iron deficiency and cogn itive test scores among a nationally representative sample of school-aged c hildren and adolescents. Design. The National Health and Nutrition Examination Survey III 1988-1994 provides cross-sectional data for children 6 to 16 years old and contains m easures of iron status including transferrin saturation, free erythrocyte p rotoporphyrin, and serum ferritin. Children were considered iron-deficient if any 2 of these values were abnormal for age and gender, and standard hem oglobin values were used to detect anemia. Scores from standardized tests w ere compared for children with normal iron status, iron deficiency without anemia, and iron deficiency with anemia. Logistic regression was used to es timate the association of iron status and below average test scores, contro lling for confounding factors. Results. Among the 5398 children in the sample, 3% were iron-deficient. The prevalence of iron deficiency was highest among adolescent girls (8.7%). A verage math scores were lower for children with iron deficiency with and wi thout anemia, compared with children with normal iron status (86.4 and 87.4 vs 93.7). By logistic regression, children with iron deficiency had greate r than twice the risk of scoring below average in math than did children wi th normal iron status (odds ratio: 2.3; 95% confidence interval: 1.1-4.4). This elevated risk was present even for iron-deficient children without ane mia (odds ratio: 2.4; 95% confidence interval: 1.1-5.2). Conclusions. We demonstrated lower standardized math scores among iron-defi cient school-aged children and adolescents, including those with iron defic iency without anemia. Screening for iron deficiency without anemia may be w arranted for children at risk.