Factors causing hearing impairment: some perspectives from Europe.

This review concentrates on factors causing permanent hearing impairment in childhood, described in some European studies. The emphasis is on comparative studies, based on strict criteria and terminology upon which longitudinal changes in the pattern of factors causing hearing impairment can be demonstrated in well-defined cohorts of children. The high proportion of 20-39 percent of unknown causes of permanent hearing impairment in childhood reflects a general lack of knowledge about causative factors and systematic etiologic evaluation within pediatric audiology. Future surveillance programs, including examination procedures directed towards causative factors, may see a reduction of the "unknown" category and ultimately may result in prevention of permanent hearing impairment in childhood. Some factors causing hearing impairment in adults are mentioned, including recent studies that show organic toxic solvents as a factor. As well, some controversial findings concerning the relationship between hearing impairment and endocrine disorders such as hypothyroidism and diabetes mellitus are briefly reported. It is concluded that future developments and research in the etiologic field within pediatric and adult audiology may contribute to the delineation of yet unknown damaging factors or reduction of the effect of factors causing hearing impairment--a disorder that ultimately results in adverse effects on the quality of life in all age groups.