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- Title
Hearing in the Elderly: Cochlear Implants in Comparison to Hearing Aids.
- Authors
Steffens, Thomas; Kießling, Jürgen; Müller-Deile, Joachim
- Abstract
Background: It is assumed that cognitive decline significantly influences speech recognition with cochlea implants (CI) in elderly patients. To explain the consequences of sensory impairment and central auditory processing deficits in the elderly, researchers outlined four processes - hearing, listening, comprehending, and communicating - that, when taken together, more fully describe auditory functioning [Kieflling et al., 2003]. While ever process is affected to some extent by aging, it appears that certain dimensions of hearing may be restored by use of a cochlear implant, which serves as a substitute for the sensory function of the inner hair cells. Furthermore, listening comprehending, and communicating can be enhanced by rehabilitation after hearing is sufficiently improved. Thus, through the provision of access to speech signals, elderly patients derive significant benefit from cochlear implantation, despite possible age-related peripheral an central deficits. However, a number of studies have shown an age-related difference in speech perception even after accounting for threshold elevation [for a review, see Pichora- Fuller and Souza, 2003]. Specifically, the masking and distracting effects of noise may inordinately reduce speech recognition if cognitive performance is reduced by aging [Pichora-Fuller et al., 1995]. Aim: If age is to be considered a general or independent factor in explaining reduced speech recognition in the elderly, it should be present in cochlear implant users, as well as in age-matched hearing aid (HA) patients. Indeed, this effect should be independent of the technical and physiological differences between hearing with HA and CI. This study addressed this hypothesis by comparing speech recognition in quiet and noise and cognitive performance of elderly CI and age-matched HA users. Materials and Methods: Unaided and aided pure-tone thresholds were measured for all aided ears. To monitor age-related cognitive decline, the Digit Span Test was used to assess auditory attention, maintenance of information in short-term memory and working memory capacity. Speech recognition in quiet was tested with the Freiburg Monosyllables Test at 50 and 65 dBSPL and the Oldenburger Sentence Test (OLSA) at 65 dBSPL. The OLSA was also used for assessments of speech recognition thresholds (SRT) in snoise, using a fixed noise level of 65 dBSPL and an adaptive speech level. Results for speech recognition of monosyllables in quiet were divided into better ear and worse ear categories in the case of bilaterally aided participants. The improvement in speech recognition due to head shadow effect (Interaural Level Difference, ILD) was assessed for unilateral and bilateral hearing. In patients with bilateral CI or HA fitting, binaural hearing improvement was assessed as Binaural Intelligibility Level Difference (BILD). Dementia was selected as an exclusion criterion and was screened using the Clock-Drawing Test. Age dependency was investigated by ANOVA and Pearson correlation. Results: Results of all cognitive and speech recognition tests were independent of age for the CI group, whereas for the HA group a significant age effect was found for all tests, except that of bilateral/binaural improvement (ILD and BILD). All of the speech testing results for the HA group correlated significantly with age by partial correlation analysis, when controlling for aided thresholds. According to the ANOVA results, no significant correlation with age was found for the CI group. Age dependency of aided thresholds were evident for 1 and 2 kHz in the CI group, as well as for 4 kHz in the HA group (Table 1). After controlling for age, negative partial correlations were significant for aided thresholds at 1 and 2 kHz with monosyllables in quiet and with 50 and 65 dBSPL sentences in quiet for the HA group. For the CI group, correlations were significant for aided thresholds at 4 kHz with monosyllables and OLSA in quiet at 65 dBSPL A significant correlation with OLSA in noise was also identified for aided thresholds at 4 kHz, in cases of unilateral hearing with CI at the side of the better ear. Discussion: The hypothesis that speech understanding in quiet and noise is age dependent was confirmed for the HA group but not for the CI users. For the HA group, speech understanding in quiet was probably driven by the limitation of the hearing aid bandwidth, as aided thresholds above 4 kHz revealed insufficient amplification to provide access to soft, high-frequency speech sounds. For the CI group, low-frequency aided thresholds at 1 and 2 kHz were uniformly low. Thresholds at 4 kHz were on average 5 dBHL higher than in the lower band, which might have led to a small, but significant effect on speech recognition in quiet. Conclusion: Age exhibited a stronger influence on speech recognition than on aided thresholds, but only in the case of acoustic hearing with HA. Speech recognition with direct electric stimulation of the acoustic nerve through a cochlear implant was not reduced with increasing age. In light of these findings, presbycusis appears closely related to acoustic hearing but largely ineffective at explaining electric hearing with CI.
- Subjects
SPEECH perception; COCHLEAR implants; PATIENTS; HEARING; NOISE
- Publication
Audiology & Neurotology, 2012, Vol 17, p6
- ISSN
1420-3030
- Publication type
Article