Delay of cortical thinning in very preterm born children

•We investigated age effects on cortical thickness in preterm and control children.•In preterms, age correlated negatively with frontal and parietal cortical thickness.•In controls, age was not associated with cortical thickness.•Cortical thickness differences were found in young but not in older children.•Results point to a developmental delay of cortical thinning caused by prematurity.

BackgroundCortical gray matter thinning occurs during childhood due to pruning of inefficient synaptic connections and an increase in myelination. Preterms show alterations in brain structure, with prolonged maturation of the frontal lobes, smaller cortical volumes and reduced white matter volume. These findings give rise to the question if there is a differential influence of age on cortical thinning in preterms compared to controls.AimsTo investigate the relationship between age and cortical thinning in school-aged preterms compared to controls.Study design and outcome measuresThe automated surface reconstruction software FreeSurfer was applied to obtain measurements of cortical thickness based on T1-weighted MRI images.SubjectsForty-one preterms (< 32 weeks gestational age and/or < 1500 g birth weight) and 30 controls were included in the study (7–12 years).ResultsIn preterms, age correlated negatively with cortical thickness in right frontal, parietal and inferior temporal regions. Furthermore, young preterms showed a thicker cortex compared to old preterms in bilateral frontal, parietal and temporal regions. In controls, age was not associated with cortical thickness.ConclusionIn preterms, cortical thinning still seems to occur between the age of 7 and 12 years, mainly in frontal and parietal areas whereas in controls, a substantial part of cortical thinning appears to be completed before they reach the age of 7 years. These data indicate slower cortical thinning in preterms than in controls.