Clinical pure-tone versus three-interval forced-choice thresholds: effects of hearing level and age.

Hearing threshold levels were measured at 2 kHz using both a standard clinical procedure and a three-interval forced-choice procedure. The 240 subjects (aged 50-75 years) embraced both normal hearing and symmetrical sensorineural hearing impairment. The sample was carefully constructed to dissociate hearing threshold level from age, by oversampling the young impaired and the older normally hearing. The forced-choice threshold was found to be generally acuter than the clinical threshold. This was related to increasing severity of hearing loss at 1.7 dB per 10 dB HL and to age at 1.6 dB HL per 10 years. Hearing threshold accounted for 12% of the variance in the discrepancy between the two types of threshold, while age accounted for only 4% due to the narrow range used. After control for these thresholds and age, there were also significant associations with a self-estimate of hearing ability and with the neuroticism score from a personality questionnaire. When interpreting epidemiological findings, particularly in longitudinal studies, the separation between sensory and cognitive factors in threshold measures needs to be considered. The obtained discrepancies as a function of hearing level and age were applied to a statistical model for population prevalences for hearing impairment. The results suggested that the choice of method could have material effects on overall prevalence estimates and on the magnitude of the apparent age effect.