Risk factors for hearing disorders: epidemiologic evidence of change over time in the UK.

The prevalence** of all bilateral sensorineural hearing impairments of at least 40 dB HL was assessed by a retrospective ascertainment study to be about 1.2 children per 1000 births per annum, over the period 1983-1988. This prevalence was highly variable over year and region of the study. For all profound (at least 95 dB HL) impairments, the prevalence was 1 in 2703 children per birth cohort. The contribution of acquired impairments and inter-region transfers after birth was not trivial, being over 25 percent for the profound impairments. The proportion of the bilateral moderately profoundly hearing impaired who might have been in the neonatal intensive care unit, have a family history of childhood deafness, or craniofacial anomaly recognizable prior to maternity discharge was 64 percent. Changes in the relative distribution of the etiology of hearing impairment seem to have taken place since the EC 1969 birth cohort study. These changes should have considerable impact on the planning of services for hearing-impaired children and child health surveillance in general.