Preterm birth with very low birth weight (VLBW, ≤1500 g) is connected to reduced white matter (WM) integrity in childhood and adolescence. These changes in WM are correlated to motor, sensory and neuropsychological impairments. CNS myelination continues into the early twenties, but the consequences of this for WM integrity in VLBWs have not been explored. DTI and tract based spatial statistics (TBSS) was carried out to test for voxelwise differences in fractional anisotropy (FA), eigenvalues and mean diffusivity (MD) between a preterm VLBW group (n=49) and a control group born at term (n=59) at 18-22 years of age. TBSS was also used to explore the relationship between perinatal clinical data and general cognitive ability (total IQ), respectively, and the DTI metrics (FA and MD), with gender and age as a confounder. In the VLBW group several major WM tracts particularly in the posterior region had significantly reduced FA caused by an increase in the two lowest eigenvalues. MD was significantly increased in the VLBWs in 50% of the same regions as the FA changes, but encompassing also more peripheral WM. In the VLBW group, FA was found to correlate positively with birth weight and negatively with number of days in intensive care and on mechanical ventilator, particularly in the corpus callosum. FA was found to correlate positively with total IQ in the young preterm adults. In the controls there was no correlation between FA and total IQ. Our results indicate that the neurologic sequelae of preterm birth with VLBW are a lifelong condition inducing structural and functional impairments also in adulthood in VLBW survivors. The greatest risk of having reduced WM integrity in adulthood was found in the most immature VLBW neonates requiring mechanical ventilation and long-term intensive care.
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