P18 Is the risk of permanent childhood hearing impairment higher in babies of shorter gestational length

Background Permanent childhood hearing impairment (PCHI) has major implications for social and cognitive development over the life-course. Early detection and management improves outcomes, providing the rationale for universal newborn hearing screening (UNHS), introduced in England from 2002. In England and Wales, one baby in every eight is admitted to specialist neonatal care, including neonatal intensive or special care baby units (NICU/SCBU), a known risk factor for PCHI, however the association with gestational length remains unclear. In England and Wales, 7.6% infants are born before 37 weeks gestation; this is higher (16.2%) among those of South Asian ethnicity. We examined PCHI risk by age 11 years in a prospective UK-wide cohort of children born before UNHS. We tested the hypothesis that lower gestational length is associated with higher PCHI risk after adjusting for NICU/SCBU admission and ethnicity. Methods PCHI risk (cumulative incidence) was based on parental report of hearing impairment and associated treatment at ages nine months, three, five, seven and 11 years for 19 518 children participating in the Millennium Cohort Study. The association of PCHI (defined by provision of hearing aids/cochlear implants, persisting hearing impairment at final report, and absence of glue ear) with gestational length was investigated using multivariable discrete-time survival analysis, adjusting for NICU/SCBU admission, ethnicity and other confounding factors, and weighting for survey design (Stata: Release 14; StataCorp LP). Results Parents reported no health problems in the first week after birth in 10 247 (52.4%), children, neonatal illness without NICU/SCBU admission in 6781 (38.0%), and NICU/SCBU admission in 1785 (9.6%). PCHI was ascertained in 44 children by age 11 years. PCHI risk was 1.0 per 1000 children (95% CI: 0.6–1.6) by age 9 months, rising by age five to 1.5 (1.0–2.2) and by age 11 to 2.1 (1.5–3.0). PCHI risk by age 11 was not associated with gestational length (hazard ratio (HR): 1.00, 95% CI: 0.98–1.03), but was associated with parental report of neonatal illness with or without NICU/SCBU admission (HR: 6.33; 2.27–17.63 and 2.62; 1.15–5.97, respectively) and Bangladeshi or Pakistani ethnicity (HR: 2.78; 1.06–7.31). Conclusion In this cohort, born before UNHS, PCHI risk was highest in infancy. Neonatal illness, irrespective of NICU/SCBU admission, and not gestational length, increased PCHI risk by age 11 years. Further research should explore the observed increased PCHI risk in children of Bangladeshi or Pakistani ethnicity, and the relevance for UNHS of PCHI with onset or diagnosis after infancy. ESRC-funded PhD ES/J500185/1.