title: Profound permanent hearing impairment in childhood: causative factors in two European countries.
abstract: A collaboration between Denmark and Wales was established in order to evaluate any differences between countries in factors causing permanent childhood hearing impairment (PCHI). Two identical 6-year birth-cohorts from 1975-1980 suffering from a permanent hearing loss > or = 90 dB HL in the better hearing ear, averaged across 0.5-4 kHz (BEHL), were included in the analysis. The overall estimated prevalence of children with this loss was 0.41/live births in Wales (n = 59). In Denmark the overall prevalence was 0.45/1,000 live births (n = 34), there being no significant differences in prevalence between the two countries. Both cohorts were subjected to a multidisciplinary investigation protocol. No significant differences were found between countries in the proportion of hearing impairment caused by the various factors, when based on uniform criteria and identical birth-cohorts. The proportion of inherited hearing loss is 47-50% in the two countries. Within inheritance the proportion of non-syndromal/syndromal inheritance differs slightly, as non-syndromal inheritance comprises 50% in Wales, and 76% in Denmark. The reported proportion of 16-34% of unknown factors causing profound PCHI emphasises the need for appropriate protocols for aetiological evaluation.
authors.affiliation: Audiological Department, Bispebjerg Hospital H:S, Copenhagen, Denmark. bbhaudap@login.dknct.dk
authors.forename: A
authors.initials: A
authors.lastname: Parving
authors.forename: D
authors.initials: D
authors.lastname: Stephens
mesh_terms: D002648:Child; D015331:Cohort Studies; D003638:Deafness / Q000453:epidemiology / Q000209:etiology*; D003718:Denmark / Q000453:epidemiology; D006801:Humans; D015995:Prevalence; D014852:Wales / Q000453:epidemiology