The purposes of this study were: To determine the quantitative and qualitative changes that occur in transient-evoked otoacoustic emissions(TEOAEs) in older individuals without addressing the effect of aging alone and without correction for hearing loss of the subject selection. To investigate the clinical value of measuring TEOAEs in the routine audiological evaluation of older people reasoning that a finding of hearing loss in the presence of TEOAEs could indicate a form of presbycusis with a primary central component.
Click-evoked otoacoustic emissions (CEOAEs) were measured in 201 subjects without middle ear problems aged 60 yr and older (range 60 to 97 yr) who volunteered for the study because of complaints concerning their hearing. Audiological procedures included a pure-tone audiogram, modified Speech Perception in Noise test (German version: Basler Satztest), and the Hearing Handicap Inventory for the Elderly (German version). Results from ears with a pure-tone average (PTA) at 0.5, 1, and 2 kHz of ≤30 dB HL were further analyzed with respect to the presence or absence of CEOAEs. In addition, tone burst evoked otoacoustic emissions (TbOAEs) were tested in ears with responses to click stimuli. The test consisted of a paradigm used previously in our laboratory to assess superposition and suppression of frequency within the cochlea (see Xu, Probst, Harris, & Roede, 1994).
CEOAEs were not detectable in ears with a PTA >30 dB HL. The prevalence of CEOAEs in ears with a PTA ≤30 dB HL was 60%. Response levels decreased as hearing thresholds became poorer, but there was no apparent influence on TEOAE level due to age alone. The audiological measures from ears with and without CEOAEs and with PTAs ≤30 dB HL were similar with the exception of small between group differences at lower frequencies. The TbOAE results showed no differences in linear superposition and suppression when results were compared with those of younger subjects tested previously.
The lower overall amplitudes of TEOAEs and the lower prevalence of 60% in comparison to results from younger subjects with normal hearing imply that cochlear changes do occur with aging. However, the preservation or loss of TEOAEs does not separate subjects with presbycusis into distinct audiological categories or handicaps. Tone burst results suggest that frequency processing within the cochlea is not affected by age alone. We conclude that TEOAEs add no relevant information in the routine clinical evaluation of elderly persons with hearing problems.
HNO-Universitätsklinik, Kantonsspital, CH-4031 Basel, Switzerland.
Address for correspondence: Prof. Dr. Rudolf Probst, HNO-Universitätsklinik, CH-4031 Basel, Switzerland.
Received July 26, 1996; accepted January 7, 1997