Hearing impairment and deafness : genetic and environmental factors - interactions - consequences : a clinical audiological approach

Abstract: OBJECTIVES - Hearing impairment (HI) can be due to genetic or environmental factors, e.g. noise. More than 50% of HI cases are thougt to be hereditary. HI can affect social participation in different ways. How serious these problems becomes depends on several factors, for example, the type of social environment the person lives in. The objective of the present study was to point out the importance of studying HI and deafness in a broad perspective, from the molecular - biological level to the psychological - social level and to evaluate how interactions of factors at several levels form the consequences, in a long-term perspective, to witch HI and deafness can lead. MATERIAL AND METHODS - Three different study populations have been used to study the four levels in this study: Papers I - III; 1200 noise-exposed workers (molecular and biological levels), Paper IV; 50 persons with HI since early childhood, with or without a family history of HI (FHHI)(biological, psychological and social level), and in Paper V; 600 persons with early onset of deafness in two counties with differently strong Deaf communities (psychological and social level). RESULTS - The molecular genetic studies (Papers I – III) showed that the combination of smoking and having a mutation in the protective antioxidant system revealed an additional risk for noise induced hearing loss. In Paper IV, only small differences was found between subjects with and without a FHHI. The results in Paper V indicated that differences in the social environment, in terms of the strength of the Deaf community, influence family factors such as marriages, divorces and the number of children born. CONCLUSIONS - Analysing complex issues such as HI and deafness from a medical audiological perspective requires a multi- level approach at several levels. The results indicate that interactions of factors at all four levels form the consequences, in a long-term perspective, to wich HI and deafness can lead. Furthermore, this multi-level approach - here called a clinical audiological approach - is essential when using the ICF framework in audiological rehabilitation/habilitation.