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Iron-deficient infants have lower cognitive scores at 19, especially in lower socioeconomic levels

November 07, 2006

Costa Rican teens who were iron-deficient as infants continue to lag behind their peers in cognitive test scores, with a wider gap for children at lower socioeconomic levels, according to study results published in the November issue of Archives of Pediatrics & Adolescent Medicine, one of the JAMA/Archives journals.

Several previous studies have shown that children with low levels of iron in their blood do worse than those without an iron deficiency on tests that measure cognitive skills, such as thinking, learning and memory, according to background information in the article. About one-fifth to one-fourth of children around the world have iron deficiency anemia, in which a lack of iron causes problems with hemoglobin-the compound that red blood cells use to transport oxygen through the bloodstream. Many more have low iron without anemia. Children from poor, minority or immigrant backgrounds are more likely to be iron-deficient.

Betsy Lozoff, M.D., University of Michigan, Ann Arbor, and colleagues studied the long-term effects of iron deficiency and socioeconomic status in a group of 185 children from an urban area in Costa Rica. The children, who were an average of 17 months old when the study began in 1983 to 1985, were screened for iron deficiency at their first visit. They were given cognitive tests (on which the index, or overall average score, is 100) then and again at ages 5, 11 to 14, 15 to 18 and 19 years. Those who had low iron levels in infancy even after three months of iron therapy were compared with those who had normal iron levels either without or after treatment.

Of the 185 children, 87 were from middle-class families and 98 were from families with low socioeconomic status. Sixty-two percent of those with chronic iron deficiency and 49 percent of those with good iron status were from families with low socioeconomic status. In middle-class families, initial scores on cognitive tests were eight points apart, 101.2 for those with iron deficiency and 109.3 for those with sufficient iron levels; the gap remained at eight or nine points through 19 years. For those in lower classes, initial scores were also eight points apart: 93.1 for iron-deficient infants and 102.8 for those with normal iron levels. By the time these individuals were 19 years old, the gap in cognitive scores between iron-deficient and non-iron deficient teens had widened to 25 points (70.4 vs. 95.3). "Such a difference is likely to be functionally significant regarding educational attainment and career choices in adulthood," the authors write.

"The observed pattern appears to make sense in terms of the cumulative and transactional nature of cognitive development," they continue. "Acquisition of new skills is intimately linked to mastery of skills at an earlier developmental level. If direct and indirect effects of early iron deficiency on the brain disrupted or delayed basic developmental processes, there could be a snowball effect. In an economically stressed family environment, there might not be the resources or capacity to help children compensate."

The results highlight the need to identify children at risk for iron deficiency and prevent or treat the condition in infancy, the authors conclude.

JAMA and Archives Journals