Epidemiology and etiology of acquired hearing disorders in childhood in the Cologne area.

Because of their serious consequences for all aspects of development, severe hearing disorders in children are an important clinical entity. A better understanding of the epidemiology and etiology of acquired hearing disorders may potentially lead to more effective prevention. Marked differences in the epidemiology of acquired hearing disorders are reported in the literature. In order to illuminate the problem of acquired disorders and to define current etiological causes with special regard to ethnological factors in the Cologne area, we started a retrospective study. A total of 314 children in residence at the school for hearing impaired children in Cologne were investigated. We also obtained concise data on the structure of the population in order to determine prevalence of acquired hearing disorders in the German and immigrant portions of the population. We found an overall prevalence of 0.43 per thousand for severe hearing disorders and deafness. German children were most frequently affected by acquired, and non-German children by hereditary hearing disorders. The most common causes of acquired severe hearing disorder were the perinatal complex of premature delivery, anoxia and hyperbilirubinuria or kernicterus. Other causes were congenital rubella infections and meningitis in early childhood. The accumulation of perinatal etiologies seems to be the reason for the remarkable majority of acquired hearing disorders among German children. One reason might be progress in neonatology which exerts two effects. It decreases perinatal mortality but increases perinatal complications like acquired hearing impairment. The incidence of congenital rubella in Germany has decreased during recent years, reaching a low level.