School outcomes after HIE: a population-based cohort study

Objective: To study the school performance of children with hypoxic ischaemic encephalopathy (HIE) relative to population controls from childhood to early adolescence.

Design: Population-based cohort study.

Setting: New South Wales, Australia.

Patients: All 564 159 live-born infants ≥35 weeks' gestation born between 2008 and 2013 were eligible; 550 with HIE and 558 355 population controls. 

Exposure: Mild, moderate-severe HIE.

Main outcome measures: National school assessment performance at 8-9, 10-11 and 12-13 years. Secondary outcomes: reading, writing, spelling, grammar and numeracy scores at these ages. Linear regression models estimated the adjusted mean difference (aMD) at each timepoint. Hierarchical growth-curve modelling assessed academic trajectories (adjusted β).

Results: Children with moderate-severe HIE had significantly lower total z-scores compared with controls at 8-9 years (aMD -0.70; 95% CI -0.84 to -0.52), 10-11 years (aMD -0.96; 95% CI -1.19 to -0.57) and 12-13 years (aMD -0.82; 95% CI -1.12 to -0.53), especially in reading and writing. The gap in overall mean scores remained fixed over time. Despite a lower likelihood of passing each year compared with controls, most infants with moderate-severe HIE passed each year (n=103, 62.4%). Children with mild HIE did not perform significantly differently from controls at 8-9 years (aMD -0.09; 95% CI -0.32 to 0.15), although there was a signal of worsening performance with age (β=13.54; 95% CI -21 to -6.07).

Conclusions: Children with moderate-severe HIE perform at a lower academic level than their peers, yet most meet national standards up to early adolescence. In contrast, children with mild HIE perform on par with their peers. This information is crucial for families: providing reassurance and a basis for needed support.