Prediction of cognitive abilities at the age of 5 years using developmental follow-up assessments at the age of 2 and 3 years in very preterm children.

Aim: This study investigated prediction of separate cognitive abilities at the age of 5 years by cognitive development at the ages of both 2 and 3 years, and the agreement between these measurements, in very preterm children.

Methods: Preterm children (n=102; 44 males; 58 females) with a gestational age less than 30 weeks and/or birthweight less than 1000g were assessed at the ages of 2 and 3 years using the second edition of the Bayley Scales of Infant Development, the Child Behaviour Checklist, and a neurological examination, and at the age of 5 years using the third edition of the Wechsler Preschool and Primary Scale of Intelligence.

Results: Cognitive development at ages 2 and 3 years explained 44% and 57% respectively of full-scale intelligence at the age of 5 years. Adding psychomotor, neurological, and behavioural outcomes to the regression model could not or only marginally improve the prediction; adding perinatal and sociodemographic characteristics to the regression model increased the explained variance to 57% and 64% respectively. These percentages were comparable for verbal intelligence. Processing speed quotient and especially performance intelligence were predicted less accurately.

Interpretation: Not all aspects of intelligence are predicted sufficiently by the Mental Development Index at ages 2 and 3 years. Follow-up of very preterm children until at least the age of 5 years is needed to distinguish between different aspects of cognitive development.