Aim: To assess the intelligence quotient (IQ) and academic achievement in early adulthood of a cohort of extremely-low-birthweight (ELBW 1000 g) subjects.
Methods: All 82 ELBW survivors consecutively born in or referred to a single tertiary center in 1976-1981 were traced at a mean age of 18 y. Three disabled children had died. Fifty-nine subjects (75%) had their IQ tested and 69 (87%) responded to a questionnaire. They were compared to 44 term, normal birthweight (NBW) matched controls. Outcome measures were: IQ (Wechsler Adult Intelligence Scale) and educational outcome. The main outcome variables were compared between groups and analyzed for neonatal and demographic data and in the ELBW group for childhood data.
Results: There was a strong relationship (r2=0.55, p<0.0001) between childhood and adult IQ for the 41 ELBW subjects tested at both ages (6.1+/-1.3 and 18.4+/-1.9 y). Differences were significant between ELBW and NBW groups: in mean full-scale IQ (94+/-12 vs 108+/-14), verbal IQ (93+/-12 vs 106+/-14) and performance IQ (97+/-14 vs 109+/-16) (p<0.0001). Differences between ELBW and NBW groups in prevalence of IQ<85 (19 vs 2%, p=0.012), of schooling in a regular curriculum for age (36 vs 68%, p=0.0011), of requirement for special classes or schools (33 vs 9%, p=0.0032), and of obtainment of secondary school diploma for those 18 y or older (56 vs 85%, p=0.018) were largely due to fathers' socio-economic score.
Conclusion: ELBW subjects had a mean adult IQ in the normal range; however, it was one standard deviation below that of NBW subjects and they had more school failures. Despite this, more than half of ELBW subjects aged 18 y or more had obtained their secondary school diploma.