Latent class growth analysis identified different trajectories in cognitive development of extremely low birthweight children

Background Recent longitudinal studies suggest stable cognitive development in preterm children, although with great individual variation. This prospective neurocognitive follow-up study of extremely low birthweight (ELBW, <1000 g) children aimed to characterise groups with different developmental trajectories from preschool to preteen age. Methods ELBW children (n=115) born in Finland in 1996-1997 participated in cognitive assessments at a median age of 5.0 years and 11.3 years. A standardised test of intelligence (Wechsler Preschool and Primary Scale of Intelligence-Revised or Wechsler Intelligence Scale for Children-third edition) was administered at both ages. Results Three ELBW groups with different developmental trajectories over time were identified with latent class growth analysis. Children with average (Full-Scale IQ (FSIQ): 85-115) and below average (FSIQ: <85) intelligence at 5 years of age had significant decreases in intelligence scores by 11 years of age (-11.7 points and -14.9 points, respectively, both p<0.001), while those with above average intelligence (FSIQ: >115) showed stable development (-3.2 points, p=0.250). Multiple linear regression showed that neonatal complications (intraventricular haemorrhage grade 3-4 and blood culture positive sepsis) and maternal education significantly predicted lower intelligence at the second assessment (F(3,106)=7.27, p<0.001, adjusted R 2 =0.147). Conclusions ELBW children represent a heterogeneous patient population in which groups with different cognitive trajectories can be detected. Deterioration may occur particularly in children with initial average or below average cognitive performance at 5 years of age, with neonatal complications and lower maternal education presenting as risk factors. Catch-up in cognitive functions seems more uncommon in the ELBW population, which should be noted in clinical work.