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
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>.▪