Epidemiology of hereditary hearing disorders in childhood: a retrospective study in Germany with special regard to ethnic factors.

Recent studies have revealed marked differences in the prevalence of hearing impairment in childhood. It remains unknown whether this is caused by geographic, sociocultural or ethnic factors. In order to provide consistent data, 314 children in residence at a school for hearing impaired children of a well-defined German area were investigated retrospectively. We estimated an overall prevalence of .43/1000 of hearing impairment for this area. A striking variability between different nationalities could be observed. For German children, the prevalence was .36/1000, for Turkish 1.04/1000 and for Italian children 1.37/1000. Hereditary hearing losses and, in particular, autosomal recessive caused hearing disorders were the most common cause of hearing impairment in foreign but not in native children. One reason might be the frequency of marriages between relatives resulting from the social isolation of the foreign groups in German society.