As over-the-counter hearing aids and their intended users – adults with mild to moderate hearing loss — continue to generate headlines, the under-utilization of cochlear implants remains largely overlooked. Reports indicate that just under 8% of adults with severe-to-profound hearing loss have received a cochlear implant (CI), a technology with proven outcomes for those who meet the candidacy requirements for it.
Experts believe there are a variety of reasons that explain this low uptake CI rate, poor access to audiologists & otolaryngologists, and a general lack of education by both these professions about recent advances in cochlear implants. Poor public awareness about the consequences of hearing loss and its associated risk factors, in part, accounts for poor market penetration rates for hearing aids. In contrast, the poor uptake associated with cochlear implants, which requires a comprehensive evaluation from both an audiologist and otolaryngologist before they can be used can be blamed, at least to some extent, on a lack of awareness of cochlear implant candidacy requirements and potential benefit among these professionals.
Considering that for more than a decade hearing aids and cochlear implants have become more alike than different, it’s somewhat surprising cochlear implants have not received the full attention of audiologists. Both technologies have sophisticated sound processing strategies, Bluetooth streaming capability, and offer the patient a variety of accessory options. Today, the result is individuals with hearing loss can expect enhanced performance and benefit from the latest professionally fitted hearing aids and cochlear implants. Regardless on this technological convergence, estimates indicate just over 10% of audiologists in the United States classify themselves as a CI audiologist.
Cochlear Implant Candidacy Has Expanded
Because of these innovations, cochlear implant candidacy requirements have expanded. Historically, cochlear implants have been confined to individuals with severe to profound hearing loss. Since 2005, however, adults with a moderate to profound hearing loss, and sentence recognition-in-noise scores below 60% for private insurance and below 40% for Medicare patients are considered candidates. The expanded CI candidacy requirements are primarily driven by technological innovations, such as the electric acoustic stimulation (EAS) CI system (also known as the hybrid system) that combines a CI with a conventional air conduction hearing aid in the same ear. Candidates for the EAS CI system can have up to a 60% word recognition score in the ear to be implanted, and a up to 80% word recognition score in the contralateral ear, plus thresholds sloping from near-normal in the low frequencies to moderate-to-severe in the mid to high frequency range. Although these technological advancements have expanded the candidate population, and blurred the lines between hearing aids and cochlear implants, CI uptake has remained sluggish.
A recent prospective study published in the open access journal Trends in Hearing shed light on factors that contribute to these low CI uptake rates. Over a two-year period, researchers at Vanderbilt University in Nashville, TN collected data on 287 adults who presented at their clinic for a CI evaluation. The primary goal of the study was to better understand the adult population seeking a CI evaluation. A secondary goal of the study, according to the researchers, was to define the percentage of adults presenting for the CI evaluation who is a candidate for either a bimodal (CI plus hearing aid in contralateral ear) or bilateral CI candidate.
Results of the prospective study reveal several findings sure to be of interest to clinicians. All the adults (mean age = 62.3 years) who presented to the clinic for a CI evaluation had hearing aid experience, but a whopping 62% of the individuals presented to the CI evaluation without their hearing aids. Additionally, only 32 of the 110 (29%) individuals who wore their hearing aids to the CI evaluation were successfully fitted to a standard audibility target for average level sound inputs.
Perhaps even more surprising, despite the expanded CI candidacy requirements that have occurred over the past decade-plus, nearly two-thirds of individuals who presented for the CI evaluation at Vanderbilt University clinic had a severe-to-profound hearing loss with a mean pure tone average of 82.5 dB and very low unaided sentence recognition-in-noise scores on the AzBio of 23.3% across all 287 adults. Even though CI candidacy requirements have expanded, individuals with moderate to profound with aided speech understanding near the upper range of candidacy are not finding their way into the CI center for an evaluation.
Following the CI evaluation on the 287 adults, 236 (82%) received an implant, with 24.6% choosing Advanced Bionics, 40.8% choosing Cochlear Americas, and 34.5% selecting the MED-EL device. Contrary to the hearing aid selection process used by most clinicians in the US, the audiologists at the Bill Wilkerson Center at Vanderbilt, unless there is an extenuating circumstance, request the patient select their CI manufacturer. Allowing the patient to choose their CI manufacturer pre-operatively seems to be a customary practice among CI clinics in the US.
Opportunities for Non-CI Audiologists, Too
Only 5% of adults who participated in the CI evaluation scored at or above the candidacy criteria. Given the historically low uptake rate of CIs (market penetration rates range from 1% to just under 8%) the researchers concluded “there are still many hearing aid users that could benefit from a CI who are not being referred.” The researchers went on to suggest that a self-report tool like the Speech and Spatial Qualities (SSQ) questionnaire, one that is seldom used in the clinic, might do a better job of measuring pre-CI performance with adults who currently use hearing aids.
Finally, from their pool of 287 adults, the researchers offered guidance on candidacy for the hybrid CI system, bilateral CI and a bimodal arrangement, respectively. They determined that about three-quarters of the individuals who received one CI were a candidate for a hearing aid in the contralateral ear, as most adult CI candidates (~70%) have adequate aidable acoustic hearing in the low frequency region that enable them to be bimodal candidates.
Although cochlear implants have made enormous technological progress over the past few decades, these successes have not translated into greater activity or awareness within hearing aid clinics. This study offers both proof and guidance on how adults who often struggle with conventional hearing aids might obtain better day-to-day benefit from implantable technology. In the emerging era of direct-to-consumer healthcare and deregulated hearing aid distribution, rank and file clinicians would be wise to get more involved in these proven, yet unheralded solutions.
*featured image courtesy Ohio State University Medical Center