Preterm postnatal complications and risk of attention-deficit/hyperactivity disorder

Aim: To investigate the association between the risk of attention-deficit/hyperactivity disorder (ADHD) and preterm birth and determine how postnatal complications in children born preterm is associated with the risk of ADHD. Method: This population-based cohort study used data from the Hong Kong electronic medical records. We followed 359 614 children (48% female; 6–17 years old, mean 11 years 7 months, SD 3 years 2 months) born in public hospitals in Hong Kong from 1st January 2004 to 31st December 2014 and collected medical records and demographic details for mothers and children until 11th November 2020. Results: The risk of ADHD was 4.0% in children born at term and 5.1% in children born preterm. The odds ratio for ADHD was 2.08 (95% confidence interval [CI] 1.64–2.64) for children born extremely preterm, 1.64 (95% CI 1.46–1.85) for children born very preterm, and 1.15 (95% CI 1.08–1.23) for children born late preterm. Among preterm postnatal complications, only early respiratory disease, retinopathy of prematurity (ROP), and intraventricular haemorrhage were significant predictors of ADHD after controlling for preterm birth, other risk factors, and sociodemographic variables. The excess risk of ADHD among children born very preterm or late preterm could be partly explained by respiratory disease. ROP partially mediated the risk of ADHD in children born very preterm. Interpretation: Children born preterm in all subcategories, from extremely preterm to late preterm, have increased risk of ADHD. Early respiratory infection partially mediates the risk of ADHD in children born preterm.