Young adults who were born very
prematurely, but without any serious brain impairments, may still not be
as mentally sharp as their peers, a small study published Monday
suggests.
Finnish researchers found that of 208 young
adults they tested, the half born at a very low weight – less than 3.3
pounds – generally had lower scores on some measures of memory,
attention and other mental skills.
They also had a lower average IQ score,
though it was still in the normal range, the researchers report in the
journal Neurology.
"While we know babies born severely preterm
generally achieve lower cognitive test scores, this is one of the first
studies to look at how severely low birth weight impacts executive
functioning, such as attention and visual memory, when these babies
become young adults," senior researcher Katri Raikkonen, of the
University of Helsinki in Finland, said in a news release from the journal.
The real-life impact of the lower test
scores is not clear.
Test performance for the low birthweight
group was lower, but still "normal," according to Raikkonen.
And, she noted in an email, the differences
between the two groups are averages. That is, some preemies "fare
better, others worse, which of course is the case for (full-term) babies
as well," Raikkonen told Reuters Health.
"Our study shows group differences, and one
cannot make individual-level conclusions from these findings," she said.
As far as school achievement, the preemie
group was more likely to need remedial education. But academically, they
ended up doing as well as their peers born full-term.
It's not clear how to interpret that,
Raikkonen said. One possibility, she noted, is that remedial help in
school is especially helpful for preemies, but that's not certain.
The findings are based on 103 adults in
their 20s who were born weighing less than 3.3 pounds, and 105 born
full-term. All took standard tests of memory, attention, planning and
other cognitive skills.
On average, the low-birthweight group had a
lower IQ – 102, versus just under 111 in the full-term group. But that
score is still in the normal IQ range.
The low-birthweight group also tended to
score a few points lower on the cognitive tests, though not on all of
them.
When it came to school, many more
low-birthweight adults said they had needed remedial help: 46 percent,
versus 19 percent.
On the other hand, they ended up doing as
well as the comparison group, with a similar grade point average and
education level (an average of just over 13 years of schooling).
In the U.S., it's been estimated that about
12 percent of infants are born preterm. And survival rates for tiny
preemies, like those in the current study, have risen substantially in
the past few decades.
Still, those infants are at
higher-than-normal risk of health problems in the long run. Another
recent study also found mild learning problems in extreme preemies once
they reached kindergarten.
The current work excluded preemies with any
major neurological impairments, Raikkonen said. But it's still possible
that more-subtle problems in early brain development could explain the
lower test scores, she explained.
"Even in apparently healthy infants," she
said, "minor brain insults may restrict later brain plasticity and brain
maturation and manifest in altered neurocognitive functioning even in
young adulthood."
"Plasticity" refers to the brain's ability
to change in response to input from the environment, which includes
recovering from injury. It's possible, Raikkonen said, that plasticity
does not fully compensate for early brain injury in some preemies.
For parents of preemies, Raikkonen pointed
out that "'normal' sensitive parenting, and stimulating environment,
benefits development of all babies, regardless of their birthweight and
length of gestation (pregnancy)."
She added that some evidence suggests that
breastfeeding aids infants' development, particularly preemies' though
study findings have not been consistent on that.
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