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-Trøndelag County, Norway, during 1995-1997. The 51975 participants also provided questionnaire information about occupational and leisure noise exposure, previous ear 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.
The aim of the study was to compare the frequency-specific effects of noise on hearing acuity across the range 250-8000 Hz and the extent to which the patterns of frequency-specific threshold shifts differ between occupational noise and impulse noise. Pure-tone audiometry was administered to an adult general population sample with 51 975 subjects who also provided questionnaire information about noise exposure and other risk factors. Threshold shifts induced by life-long occupational noise and impulse noise (mostly shooting) were estimated separately in six age and sex groups for eight frequencies. Reported noise exposure, as well as observed threshold shifts, were moderate among women. Threshold shifts averaged over both ears among subjects in the higher 2% of exposure to occupational noise, reached 13 dB (3000 Hz, age 65 years + ) among men and were generally largest at 3000-4000 Hz. The shifts induced by impulse noise reached approximately 8 dB among men 45-64 years and men 65 years+. The effects of impulse noise were strongest at 3000-8000 Hz and varied little within this frequency range.
Pure-tone audiometry was administered to the adult population in Nord-Trøndelag County, Norway, 1995-97. The 51,975 participants also provided questionnaire information about occupational and leisure noise exposure, previous ear infections, and head injury. Values averaged over both ears were calculated for low (250 and 500 Hz), middle (1 and 2 kHz) and high frequencies (3, 4, 6 and 8 kHz). The aim was to estimate the magnitude of hearing loss associated with various types of exposure by age and sex. Noise, ear infections and head injury explained 1-6% of the variance in hearing loss (varying with age, sex, and frequency range), in addition to what could be explained by age alone (30-58%). Only moderate effects of noise could be detected among women. The upper tenth percentile regarding occupational noise among men older than 44 years had on average an 8-9-dB high-frequency loss, adjusted for other predictors. Exposure to impulse noise (hunting, sports shooting) caused a 7-8-dB high-frequency loss in the same group. No significant effects of frequent use of personal stereo players or regular attendance at discotheques or rock concerts could be demonstrated. There were clear effects of recurrent ear infections and head injury.
Reported EIs are associated with similar consequences in terms of reduced hearing across frequencies 0.25 to 8 kHz for male and female subjects. The observed effects are stronger among older than among younger subjects, perhaps because effects increase with age or possibly because EI affected the hearing more before 1940 than during subsequent decades. Reported early age of onset of EI increases the risk of a substantially reduced hearing level later in life.
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