Preterm children's brains can catch up years later
There's some good news for parents of preterm babies – latest research shows that by the time they become teenagers, the brains of many preterm children can perform almost as well as those born at term.
A study conducted by the University of Adelaide's Robinson Research Institute has found that as long as the preterm child experiences no brain injury in early life, their cognitive abilities as a teenager can potentially be as good as their term-born peers.
However, the results of the study, published in this month's issue of The Journal of Pediatrics, also highlight that the quality of the home environment at the time of the child's birth plays an important role in their cognition later in life.
"Every year, 10% of Australian babies are born preterm, and many studies have shown that these children often have cognitive difficulties in childhood," says one of the lead authors of the study, Dr Julia Pitcher from the University of Adelaide's Robinson Research Institute.
"This new study has some positive news. We looked at the factors that determine cognitive abilities in early adolescence, and found that whether or not you were born preterm appears to play a relatively minor role. Of significantly more importance is the degree of social disadvantage you experienced in your early life after birth, although genetics is important," Dr Pitcher says.
The study, conducted by Research Officer Dr Luke Schneider, assessed the cognitive abilities of 145 preterm and term-born young people now aged over 12. He also assessed data on social disadvantage at the time of birth and at the time of the cognitive assessment.
"The results of our study provide further proof that those born at term tend to have better cognitive abilities – such as working memory, brain processing efficiency and general intellectual ability.
"But the postnatal environment seems to be playing an important role in whether or not a preterm child is able to overcome that initial risk of reduced brain development.
"Reduced connectivity in the brain, associated with microstructural abnormalities from preterm birth, is likely contributing to the cognitive deficits in these children.
"But these abnormalities seem to be amenable to improvement depending on the environment the child grows up in, particularly as an infant, and might account for why some preterm children do better than others."
Julia Pitcher, PhD, the University of Adelaide's Robinson Research Institute.
Dr Pitcher adds: "What we don't yet know is how different factors in the home environment drive specific aspects of brain development. But early nutrition and enrichment through physical and intellectual stimulation are likely to have key roles."
To investigate the influence of a range of prenatal and postnatal factors on cognitive development in preterm and term-born adolescents.
Woodcock-Johnson III Tests of Cognitive Abilities were used to assess general intellectual ability and 6 broad cognitive abilities in 145 young adolescents aged approximately 12.5 years and born 25-41 weeks gestational age (GA). To study potential links between neurophysiologic and cognitive outcomes, corticomotor excitability was measured using transcranial magnetic stimulation and surface electromyography. The influence of various prenatal and postnatal factors on cognitive development was investigated using relative importance regression modeling.
Adolescents with greater GA tended to have better cognitive abilities (particularly general intellectual ability, working memory, and cognitive efficiency) and higher corticomotor excitability. Corticomotor excitability explained a higher proportion of the variance in cognitive outcome than GA. But the strongest predictors of cognitive outcome were combinations of prenatal and postnatal factors, particularly degree of social disadvantage at the time of birth, birthweight percentile, and height at assessment.
In otherwise neurologically healthy adolescents, GA accounts for little interindividual variability in cognitive abilities. The association between corticomotor excitability and cognitive performance suggests that reduced connectivity, potentially associated with brain microstructural abnormalities, may contribute to cognitive deficits in preterm children. It remains to be determined if the effects of low GA on cognitive outcomes attenuate over childhood in favor of a concomitant increase in the relative importance of heritability, or alternatively, if cognitive development is more heavily influenced by the quality of the postnatal environment.
This research is supported by the National Health and Medical Research Council (NHMRC).
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