Screened and unscreened hearing threshold levels for the adult population: Results from the Nord-Trondelag Hearing Loss Study

This paper presents normative data of hearing threshold levels of a population screened with various criteria, as compared to unscreened population data. Computer-controlled pure-tone audiometry was administered to the adult population in Nord-Trondelag County, Norway, during 1995-1997. The 51 975 participants also provided questionnaire information about occupational and leisure noise exposure, previous car infections, and head injury. While screening had little effect on the median hearing threshold levels of young adults, there was a substantial effect when screening men above 40 years of age for a history of noise exposure. Screening for known ear-related disorders and diseases resulted in small effects on the mean hearing threshold levels. The median hearing thresholds of both the screened and the unscreened sample exceeded the age and sex specific thresholds specified by the ISO 7029.