Perinatal and childhood predictors of general cognitive outcome at 28 years in a very‐low‐birthweight national cohort

Aim To determine IQ at 26 to 30 years in very‐low‐birthweight (VLBW) adults compared with term‐born controls; and to examine the stability of IQ in VLBW individuals between 7 to 8 years and 26 to 30 years, identify perinatal and social predictors of IQ, and assess the contribution of brain volume to IQ. Method At 26 to 30 years, 229 VLBW adults (71% survivors of prospectively enrolled national cohort) and 100 term‐born controls were tested on the Wechsler Abbreviated Scale of Intelligence. For VLBW, IQ at 7 to 8 years, perinatal and social data were extracted from the data set, and 150 adults underwent volumetric cranial magnetic resonance imaging (MRI). Results At 26 to 30 years, the mean adjusted difference between VLBW and controls for total IQ was 9.4 (95% CI 6.5–12.4) points. In VLBW individuals the correlation between IQ scores at 7 to 8 years and 26 to 30 years was 0.78. On multiple regression analysis, parental education was the strongest predictor of verbal and total IQ at both ages. Birthweight was a strong predictor of perceptual and total IQ. In VLBW individuals with MRI scans, the addition of brain volume as a variable increased the variance explained for perceptual and total IQ. Interpretation VLBW adults have mean IQ scores 9 to 11 points below controls. Parental education and birthweight are the strongest predictors of IQ. This article is commented on by Jaekel on page 1347 of this issue.