Prevalence and risk factors for delayed-onset hearing loss in early childhood: A population-based observational study in Okayama Prefecture, Japan

Objectives: The aim of this study was to retrospectively document prevalence rates of delayed-onset hearing loss (DOHL) under 7 years old after passing the newborn hearing screening (NHS) program using its database in Okayama Prefecture, as well as records from Okayama Kanariya Gakuen (OKG, Auditory Center for Hearing Impaired Children, Okayama Prefecture, Japan). We explored the percentage of children with DOHL among all children who underwent the NHS and surveyed risk factors abstracted from their clinical records. Methods: We collected data of 1171 children, who first visited OKG from April 2006 to March 2018. DOHL children were defined as bilaterally hearing-impaired children who were diagnosed under 7 years old after passing the NHS at birth. Based on the medical records, we investigated age at diagnosis, hearing levels, and risk factors. As population-based data of 168,104 children, the percentage of DOHL subjects was retrospectively calculated among the total number of children who underwent the NHS in Okayama Prefecture from April 2005 to March 2017. Results: During the period, we identified 96 children with bilateral DOHL, of which 34 children had failed the NHS unilaterally and 62 had passed the NHS bilaterally. Among all children who underwent the NHS in Okayama Prefecture, the prevalence rate of DOHL in unilaterally referred infants was 5.2%, and 0.037% in bilaterally passed children. The prevalence of bilateral DOHL was 0.057% overall. Unilaterally referred children with DOHL were diagnosed at an average of 13.9 months, while bilaterally passed children with DOHL were diagnosed at an average of 42.3 months. Approximately 59.4% of children with DOHL had risk factors, among which family history of hearing loss was the most frequent. Conclusion: We propose the first English report of DOHL prevalence in the prefecture population in Japann, which is among the largest community-based population ever reported. The NHS is not a perfect strategy to detect all early-childhood hearing loss; therefore, careful assessment of hearing throughout childhood is recommended, especially in children with risk factors of hearing loss. Further interventional strategies must be established, such as regular hearing screening in high-risk children and assessments of hearing and speech/language development in public communities and nursery schools.