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Consequences of using chronological age versus corrected age when testing cognitive and motor development in infancy
Jacqueline F Gould1,2,3, Belinda G Fuss2, Rachel M Roberts2
1Women and Kids, South Australian Health and Medical Research Institute, Adelaide, South Australia, Australia.
Insights
Preterm infants show significant differences in cognitive and motor scores when age is standardized by chronological versus corrected age, especially in early childhood. These differences persist into later childhood, impacting research assessments.
Area of Science:
- Neurodevelopmental research
- Pediatric psychology
- Developmental pediatrics
Background:
- Children born preterm (<37 weeks' gestation) face higher risks of neurodevelopmental issues, including lower intelligence quotient (IQ).
- Standardizing assessments for preterm infants requires careful consideration of age-correction methods.
Purpose of the Study:
- To investigate psychometric score differences in cognition and motor skills for preterm children when age-standardized by chronological versus corrected age.
- To determine the impact of age-standardization methods on neurodevelopmental assessments in preterm infants.
Main Methods:
- Assessed 554 preterm infants (<33 weeks' gestation) using Bayley Scales of Infant Development at 18 months and Wechsler Abbreviated Scale of Intelligence at seven years.
- Compared cognitive and motor scores standardized by chronological age versus corrected age, analyzing score differences and impairment classifications.
Main Results:
- At 18 months, mental and motor scores standardized by chronological age were significantly lower than by corrected age (17.3 and 11.8 points, respectively).
- By seven years, a smaller but persistent difference in IQ scores was observed between chronological and corrected age standardization (1.9 points).
- Cognitive scores showed greater impact than motor scores, with more substantial differences in early childhood.
Conclusions:
- Neurodevelopmental outcome assessments for preterm infants vary significantly based on whether chronological or corrected age is used for standardization.
- While clinical assessments may only require correction in early childhood, research should continue to use corrected age into later childhood to account for persistent preterm-related biases.
Background:
Children born preterm (<37 weeks' gestation) have an increased risk of poor neurodevelopment, including lower intelligence quotient (IQ) scores compared with their term-born counterparts.
Objective:
To explore the differences in psychometric scores for cognition and motor skills when they are age-standardized according to chronological age instead of corrected age for children born preterm.
Methods:
We assessed = 554 children born <33 weeks' gestation with the Bayley Scales of Infant Development, 2nd edition (mental and motor scores) at 18 months and the Weschler Abbreviated Scale of Intelligence (IQ score) at seven years of age. Scores were standardized according to chronological age and corrected age and differences between mean chronological and corrected scores were compared, along with the proportion of children whose scores could be classified as impaired.
Results:
When scores were standardized according to chronological age instead of corrected age there was a large significant difference of 17.3 points on the mental scale (79.5 vs. 96.8, respectively) and 11.8 points on the motor scale (84.8 vs. 96.6, respectively) at 18 months. By seven years, the difference in IQ scores remained, although of a smaller magnitude at 1.9 points between mean chronological and corrected age scoring (97.2 vs. 99.1, respectively).
Conclusion:
Consistent with previous literature, outcome assessments for preterm infants consistently differed according to use of chronological or corrected age to standardized scores. Cognitive scores were impacted more severely than motor scores, and differences were more substantial in early childhood than later in childhood. For clinical purposes, correction for preterm birth is only likely to have an impact during early childhood, however assessments for research purposes should continue to correct into childhood to account for the persistent bias due to preterm birth.
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