Otoacoustic emissions in the general adult population of Nord-Trøndelag, Norway: II. Effects of noise, head injuries, and ear infections.

Otoacoustic emissions (OAEs) have been suggested as a sensitive measure of cochlear function with the potential for preclinical detection of damage. The present work assesses the risk for decreased OAEs associated with occupational and leisure noise, head injuries and recurrent ear infections. The predictive power of the environmental factors on different OAE values is compared with the prediction of conventional pure-tone hearing thresholds (PTTs). The analyses are based on data from 5072 adult subjects comprising a subsample of the 51975 subjects from the Nord-Trøndelag Hearing Loss Study. The subjects participated in a general health screening, including an examination of pure-tone audiometry, transient OAEs and distortion-product OAEs, and completed a questionnaire regarding history of noise exposure and ear disease. The predictions of OAEs and PTTs were analysed using regression analysis for various sex and age groups (20-44 years, 45-64 years, > or = 65 years). The fraction of the variance explained by exposure was generally moderate (0-4%, varying with age, sex, and type of measurement). Males showed moderate effects of work noise, impulse noise and ear infection, while ear infection was the only significant predictor in females. There were no effects of music noise and head injuries. The effect of exposure on OAEs that remained after controlling for PTTs was small and similar to the effect of exposure on PTTs that remained after controlling for OAEs.