Anemia Affects Infants' Cognition, Memory

Iron-deficiency anemia (IDA) in infancy appears associated with deficits in attention and memory development.

The study findings, reported in the August Pediatrics, reinforce previous research that found lower cognitive test scores among infants with iron deficiency than among those with healthy levels of iron.

The study, which compared 15 infants at ages 9 months and 12 months who had been diagnosed with IDA and 19 other infants who were “iron sufficient,” tested their ability to discriminate their mother's face—a highly familiar stimulus—from a stranger's face. Iron supplements were provided to the parents of all of the infants in the study, but the researchers were uncertain about the extent to which the supplements were administered to the infants.

The iron-sufficient group showed a greater response to the mother's face and a greater updating of memory for the stranger's face. This response was consistent with the age-appropriate pattern of development for 9-month-old infants.

A similar level of responsiveness was not seen in the IDA group until 12 months of age, which suggested a delay in cognitive development, according to the researchers. They said that the developmental delay in recognition memory seen in this study may be an early indicator of later cognitive problems, based on the findings of previous studies showing recognition-memory delay in infancy to be predictive of cognitive and language deficits in childhood.

“Previous research has shown infants are able to differentiate between mother and stranger very early on, and there is a distinct pattern of neural activation that is believed to reflect attention and recognition,” wrote study co-author Matthew Burden, Ph.D., a postdoctoral research fellow in the Department of Psychiatry and Behavioral Neurosciences at Wayne State University School of Medicine. “We found this pattern in the iron-sufficient infants at 9 months of age, but it was not evident in infants with IDA until 12 months, suggesting a cognitive developmental delay associated with iron deficiency.”

Although previous research studies have demonstrated lower scores among iron-deficient infants on IQ tests, they gave little indication of the neural mechanisms behind the cognitive deficits.

Burden and his colleagues used event-related potentials (ERPs) to measure transient changes in the brain's electrical activity noninvasively in response to stimuli. An electroencephalogram produced recordings from electrodes placed on the scalp when the visual stimulus was given. The infant was presented with randomly alternating digital photographs, repeated with equal probability, of their mothers' face and an unfamiliar face.

“In our study, infants in both groups seemed capable of discriminating between the stimuli, but the patterns of ERP activity in response to the mother and stranger suggested a delay in cognitive development in the infants with IDA,” the researchers said.

They pointed out that they were unaware of any other ERP study using a visually based, mother-stranger paradigm to assess effects of IDA, though auditory-recognition deficits have been found in studies of infants of diabetic mothers at high risk for prenatal brain iron deficiency.

“This study was able to reveal subtle cognitive differences associated with IDA that might not have been detected with standard behavioral or observational measures,” Burden told Psychiatric News.“ It highlights the importance of keeping a close watch on infants' health, because overt behavioral signs of health risks such as IDA may not always be obvious.”

Although the mechanisms behind the delay in cognitive development associated with iron deficiency are not clear, a growing body of animal research has found that the development of several important central nervous system processes are highly dependent on iron-containing enzymes and hemoproteins, he noted.

“We did expect that infants with IDA would show some differences in attention and recognition because of iron's impact on the central nervous system as well as having specific links to the hippocampus, which is important for memory,” Burden said.

While the study identified the same pattern of findings even after controlling for infant age at study entry and maternal depression, additional research is needed on a larger group of patients, the researchers acknowledged, to assess the degree to which this delay in cognitive development may presage adverse effects on subsequent cognitive and behavioral development in children with IDA in infancy.

“An Event-Related Potential Study of Attention and Recognition Memory in Infants With Iron-Deficiency Anemia” is posted at<http://pediatrics.aappublications.org/cgi/content/full/120/2/e336>.▪