August 6, 2010 — Iron-deficiency anemia (IDA) is linked to memory deficits in children, according to the results of a study reported online July 26 in Pediatrics.
"IDA in infancy is associated with cognitive deficits, which may persist later in life," write R. Colin Carter, MD, from Children's Hospital Boston and Harvard Medical School in Boston, Massachusetts, and colleagues. "Socioemotional deficits are also consistently observed in infants with IDA, but it is not known whether these deficits affect cognitive function."
The goal of the study was to determine effects of IDA on specific functions involved in infant cognition, as well as the effect of socioemotional deficits related to IDA in modulating these effects. During routine 9-month visits to an inner-city clinic, infants were recruited into the study. Criteria for IDA were hemoglobin levels of less than 110 g/L with abnormal values for at least 2 of the following iron deficiency indicators: mean corpuscular volume, red cell distribution width, zinc protoporphyrin-heme ratio, transferrin saturation, and ferritin.
Cognitive testing at 9 and 12 months included the Fagan Test of Infant Intelligence; A-not-B task; Emotionality, Activity, and Sociability Temperament Survey; and Behavior Rating Scale. The investigators adjusted the analyses for age, sociodemographic variables, and other potential confounders.
Study participants were 28 infants with IDA, 28 with nonanemic iron deficiency, and 21 with iron sufficiency. At 9 months, infants with IDA were least likely to demonstrate object permanence, iron sufficiency most likely, and nonanemic iron deficiency intermediate, suggesting a linear effect.
Compared with infants without IDA, those with IDA and those with hemoglobin level of 105 g/L or less had worse recognition memory on the Fagan Test of Infant Intelligence, but these effects were partially mediated by the Behavior Rating Scale orientation/engagement measure. Infants with poorer scores on the socioemotional measures had stronger effects of IDA on these outcomes.
"These data indicate poorer object permanence and short-term memory encoding and/or retrieval in infants with IDA at 9 months," the study authors write. "These cognitive effects were attributable, in part, to IDA-related deficits in socioemotional function. Children with poor socioemotional performance seem to be more vulnerable to the effects of IDA on cognitive function."
Limitations of this study include small sample size, inability to supervise iron administration, and inability to determine response to iron for infants who did not come for a subsequent blood test. In addition, the degree of IDA in this sample was relatively mild and duration probably quite short, limiting generalizability to more severe cases.
"Our findings provide evidence of specific deficits in cognitive processing (attention and memory) with IDA during an important period of infant development before the usual age for IDA screening in the primary care setting," the study authors conclude. "Deficits in these processes, which have demonstrated predictive validity for later cognitive function, have implications for intellectual function in childhood. Furthermore, these early cognitive deficits seem to be mediated, in part, by the effects of IDA on the infant's ability to engage affectively with the environment, and socioemotional deficits seem to increase the infant's vulnerability to the cognitive effects of early IDA."
This study was supported by a program project grant from the National Institutes of Health and a grant from the Joseph Young, Sr, Fund from the State of Michigan to coauthor Joseph L. Jacobson, PhD. The study authors have disclosed no relevant financial relationships.
Pediatrics. Published online July 26, 2010.
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