Cochlear implantation in older adults

Abstract

Cochlear implants allow individuals with severe to profound hearing loss access to sound and spoken language. The number of older adults in the United States who are potential candidates for cochlear implantation (CI) is approximately 150,000 and will continue to increase with the aging of the population. Should CI be routinely recommended for these older adults, and do these individuals benefit from CI? We reviewed our 12-year experience with CI in adults aged ≥60 years (n = 445) at Johns Hopkins Medical Institutions to investigate the impact of CI on speech understanding and to identify factors associated with speech performance. Complete data on speech outcomes at baseline and 1 year post-CI were available for 83 individuals. Our results demonstrate that CI in adults aged ≥60 years consistently improved speech understanding scores, with a mean increase of 60.0% (SD 24.1) on HINT (Hearing in Noise Test) sentences in quiet. The magnitude of the gain in speech scores was negatively associated with age at implantation, such that for every increasing year of age at CI the gain in speech scores was 1.3 percentage points less (95% confidence interval [95% CI], 0.6-1.9) after adjusting for age at hearing loss onset. Conversely, individuals with higher pre-CI speech scores (HINT scores between 40% and 60%) had significantly greater post-CI speech scores by a mean of 10.0 percentage points (95% CI, 0.4-19.6) than those with lower pre-CI speech scores (HINT <40%) after adjusting for age at CI and age at hearing loss onset. These results suggest that older adult CI candidates who are younger at implantation and with higher preoperative speech scores obtain the highest speech understanding scores after CI, with possible implications for current United States Medicare policy. Finally, we provide an extended discussion of the epidemiology and impact of hearing loss in older adults. Future research of CI in older adults should expand beyond simple speech outcomes to take into account the broad cognitive, social, and physical functioning outcomes that are likely detrimentally affected by hearing loss and may be mitigated by CI.

Figure 1

Schematic illustration of an ear with cochlear implantation. The microphone and the speech processor (external device) receives auditory signals from the external world and transmits the information to the receiver/stimulator (internal device), which is coupled to an electrode array (Illustration created by NIH Medical Arts).

Figure 2

Number of cochlear implantations performed in adults ≥60 years at Johns Hopkins from 1999–2010

Figure 3

Pre-CI and 1 year post-CI HINT speech scores in adults ≥ 60 years, n = 83

Figure 4

Change in HINT speech score from pre-CI to 1 year post-CI by age at CI, n = 83

Figure 5

Pre-CI and 1 year post-CI HINT speech scores by pre-CI speech score, n = 83

Figure 6

Schematic representation of cochlear anatomy. The top panel shows a cross section of the human ear, which is divided into 3 parts: external, middle and inner ear. The bottom panel shows the detailed anatomy of the cochlea, in particular the scala media, where the auditory neuroepithelium resides. (Illustration from Johns Hopkins Max Brödel Archives)

Figure 7

Three-dimensional spectrogram of a complex sound. Dimensions of a complex sound include frequency, intensity, and time, and all three aspects are encoded through cochlear transduction to afferent neural signals that are transmitted to the brainstem and higher order cortical structures for decoding.

Figure 8

Prevalence of hearing loss in the United States by age, 2001–2008.

Figure 9

Conceptual model of how hearing loss affects domains of health and functioning. Unshaded boxes depict domains most commonly studied in hearing research, and shaded boxes correspond to those domains of health and functioning that are central to aging research and public health.

Figure 10

Cognitive resource capacity is reduced by both auditory perceptual processing requirements and general age-related declines.