How does aging affect recognition of spectrally degraded speech?

Objectives/hypothesis: Cochlear implants (CIs) restore auditory sensation to patients with moderate-to-profound sensorineural hearing loss. However, the benefits to speech recognition vary considerably among patients. Advancing age contributes to this variability in postlingual adult CI users. Similarly, older individuals with normal hearing (NH) perform more poorly on tasks of recognition of spectrally degraded speech. The overarching hypothesis of this study was that the detrimental effects of advancing age on speech recognition can be attributed both to declines in auditory spectral resolution as well as declines in cognitive functions.

Study Design: Case-control study.

Methods: Speech recognition was assessed in CI users (in the clear) and NH controls (spectrally degraded using noise-vocoding), along with auditory spectral resolution using the Spectral-Temporally Modulated Ripple Test. Cognitive skills were assessed using nonauditory visual measures of working memory, inhibitory control, speed of lexical/phonological access, nonverbal reasoning, and perceptual closure. Linear regression models were tested for mediation to explain aging effects on speech recognition performance.

Results: For both groups, older age predicted poorer sentence and word recognition. The detrimental effects of advancing age on speech recognition were partially mediated by declines in spectral resolution and in some measures of cognitive function.

Conclusions: Advancing age contributes to poorer recognition of degraded speech for CI users and NH controls through declines in both auditory spectral resolution and cognitive functions. Findings suggest that improvements in spectral resolution as well as cognitive improvements may serve as therapeutic targets to optimize CI speech recognition outcomes.

Level Of Evidence: 3b Laryngoscope, 2018.