Individual cognitive patterns and developmental trajectories after preterm birth

Cognitive outcome after preterm birth is heterogeneous, and group level analyses may disguise individual variability in development. Using a person-oriented approach, this study investigated individual cognitive patterns and developmental trajectories from preschool age to late adolescence. As part of a prospective longitudinal study, 118 adolescents born preterm, with a birth weight<1,500g, participated in neuropsychological assessments at age 51/2years and at 18years. At each age, four cognitive indices, two tapping general ability and two tapping executive functions, were formed to reflect each individual's cognitive profile. Cluster analyses were performed at each age separately, and individual movements between clusters across time were investigated. At both 51/2 and 18years, six distinct, and similar, cognitive patterns were identified. Executive functions were a weakness for some but not all subgroups, and verbal ability was a strength primarily among those whose overall performance fell within the normal range. Overall, cognitive ability at 51/2years was highly predictive of ability at age 18. Those who performed at low levels at 51/2 years did not catch up but rather deteriorated in relative performance. Over half of the individuals who performed above the norm at 51/2years improved their relative performance by age 18. Among those performing around the norm at 51/2years, half improved their relative performance over time, whereas the other half faced increased problems, indicating a need for further developmental monitoring. Perinatal factors were not conclusively related to outcome, stressing the need for cognitive follow-up assessment of the preterm-born child before school entry.