The American Academy of Audiology Foundation (AAAF) is proud to present the 16th Annual Marion Downs Lecture in Pediatric Audiology at AAA 2020 + HearTECH Expo in New Orleans, Louisiana, on April 3, from 10:15 to 11:45 am.
The popular lecture series, sponsored by the Oticon Foundation, is one of the major highlights of the conference—and this year’s speaker is sure to draw a crowd. Ryan McCreery, PhD, a well-known and admired pediatric audiologist, will present this year’s session, which will be focused on the critical factors related to successful outcomes for children using hearing aids.
Dr. McCreery is the director of research and the director of the audibility, perception, and cognition laboratory at Boys Town National Research Hospital. He worked as a clinical and research audiologist in hospitals and private-practice settings before returning to complete his PhD in Human Sciences at the University of Nebraska, Lincoln. His research interests center on improving the quality of life for children with hearing loss by improving our understanding of how to adapt hearing aids to the listening needs of children.
As most audiologists will agree, it takes a special person to devote his or her career to pediatric audiology. What led you down this path?
Pediatric audiology is a great way to use science to make people’s lives better. There were several experiences in my life that, in retrospect, make it seem like the perfect career focus for me.
I have always been a scientist. As a kid, I would conduct experiments that mostly involved mixing chemicals from the garage and observing the effects of these toxic concoctions on local ant populations. I’m sure my parents were very concerned. In high school, I did a job-shadowing experience with a speech-language pathologist and found myself obsessed with how children learn to listen and talk.
I enrolled as a communication disorders undergraduate at the University of Northern Colorado and worked in a classroom for children who were deaf and hard of hearing. The children mostly wore body aids and had significant communication challenges, but many were communicating quite well. At that time, newborn hearing screening was starting in Colorado, thanks to Marion Downs and others. I saw the potential for a career where things were going to change rapidly and wanted to try to contribute as a clinician to help kids with hearing loss achieve better outcomes.
I understand your talk will be titled Enhancing Auditory Experience in Children with Hearing Aids. What do you define as the optimal auditory experience for children with hearing loss?
The basic idea is that hearing loss limits access to auditory learning and that any intervention approach where spoken language is desired should seek to provide consistent access to acoustic information to facilitate that process. Our current conceptualization of auditory experience really emerged as part of a wonderful collaboration among the University of Iowa, University of North Carolina, and Boys Town. The result of this collaboration is known as the Outcomes of Children with Hearing Loss (OCHL) Study.
The idea that hearing loss has cumulative effects on development has been talked about since Myklebust (1960) wrote about auditory deprivation in the 1950s and 1960s—and by numerous researchers since then. Initially, the idea of cumulative auditory experience was simply based on comparisons of development between children with typical hearing and children with hearing loss.
The focus shifted to differences in development among children with varying degrees of hearing loss in the 1980s, including Julia Davis’s work at Iowa that demonstrated that children with milder degrees of hearing loss were often “forgotten” when it came to intervention.
With the focus on universal newborn hearing screening, scientists such as Christine Yoshinaga-Itano and Mary Pat Moeller published research to show that earlier identification and intervention led to better language outcomes.
In the OCHL study, we had an opportunity to build on this previous research and directly test how hearing aids contribute to auditory experience separately from other components of the intervention process, which have often been lumped together.
Our key findings were that children with better speech audibility through their hearing aids and more consistent hearing aid use had better language, academic, and auditory development outcomes than peers with more limited audibility and hearing aid use. This work has established a dose-response relationship between hearing aids and outcomes that indicates that the work pediatric audiologists do to make sure hearing aids are optimally fitted and worn has a major positive impact on the development of the children they serve.
What are the three most critical demographic or hearing-related factors that influence auditory experiences for children with hearing loss?
The first factor that I think is most critical is speech audibility. The extent of audibility loss with hearing loss and how much can be restored with hearing aids are probably the most consistent predictors of a wide range of outcomes in our study.
The second critical factor is hearing aid use. Even the best fitted hearing aids cannot benefit a child if they are not worn consistently.
Finally, the linguistic environment of the child, including the quantity and quality of linguistic input from parents and caregivers, is extremely influential. Fortunately, all three of these factors can be positively influenced by audiologists and other professionals who serve children with hearing loss.
How important is full-time hearing aid use for children with hearing loss? What does data-logging tell us about usage trends in children?
As I mentioned before, hearing aid use is essential. Data from a paper by my colleagues on the OCHL study showed that children who wore their hearing aids more than 10 hours per day were closing the language-development gap with their peers with normal hearing between two to six years of age (Tomblin et al, 2015).
Data-logging is a wonderful feature in modern hearing aids that provides an objective estimate of how long the hearing aid is on. We always recommend comparing data-logging estimates to parent-reported hours of hearing aid use as a cross-check. Our data suggest that wearing the hearing aids all waking hours, as we often recommend, is challenging for most families of children who wear hearing aids, particularly during infancy.
This work has led us to rethink how we discuss hearing aid use with families and shift the conversation from all waking hours to identifying areas of success and situations where hearing aid use is more challenging. We want to build up parent and caregiver confidence, so they can eventually reach full-time hearing aid use.
What signal-processing or advanced features appear to influence children’s performance with hearing aids (or long-term success)?
The literature on the effects of different signal-processing strategies on perception and development for children who wear hearing aids can be summarized overall by saying that the benefits and limitations appear to be small for digital-noise reduction, directional microphones, and frequency lowering.
In part, I think that some of the tools we have used to research these technologies, such as speech recognition in noise and parental questionnaires, are not sensitive to how these features might benefit or limit performance with hearing aids in real-world listening environments.
I also think that children who wear hearing aids are an extremely heterogeneous group. The way we have designed studies of hearing aid signal-processing for children has focused on whether a specific feature is beneficial overall at the group level.
I think a promising direction for future research would shift the research questions from: “Is Feature X beneficial for children?” to “What are the characteristics of children who are most likely to benefit from Feature X?”
I think there are some great examples of the latter type of research question in the frequency-lowering literature and I hope that research continues in that direction.
Are remote-microphone systems helpful for children with hearing loss?
Remote-microphone systems are immensely helpful when you have a single-target talker of interest in a noisy environment. Even with well-fitted hearing aids, children with hearing loss are not yet able to reach the same levels of speech recognition in noise as their peers with normal hearing.
Remote microphones can help them to achieve those benefits, but we have work to do to help parents, caregivers, and teachers understand the listening situations where remote microphones are most beneficial.
Research on the positive effects of remote-microphone systems on language development have been recently published by my colleague from Iowa, Beth Walker, and researchers from Vanderbilt (Walker et al, 2019).
The only caveat that I would add to qualify those statements about the benefits of remote-microphone technology is that there are many listening situations where only accessing a single talker might make things more challenging.
How important are parents/caregivers in the habilitative process?
Parents and caregivers are the most important members of the habilitative process for children with hearing loss. Mary Pat Moeller published a study back in 2000 in Pediatrics that most people remember for the main finding that children with hearing loss who were enrolled in intervention at earlier ages had better language development than peers who started intervention later (Moeller, 2000).
My own favorite aspect of that paper was the finding that parents or caregivers who were highly engaged in the early-intervention process had children with the highest language scores, even when identification or intervention did not occur until later ages.
Hearing aid use and high-quality language input are other elements where parents hold the key to their child’s development. We are at our best as professionals when we can support and empower families to provide that input for their child.
Are you still collecting longitudinal data from the Outcomes of Children with Hearing Loss Study? If so, what do you hope to learn from future data?
The OCHL study and an extension of that study officially ended in August 2018. However, our team will be writing papers from that study for many years to come.
I am most excited about some of the upcoming projects examining hearing aid candidacy for children with mild hearing loss, academic and reading outcomes for our cohort, and an examination of the impacts of hearing loss on the development of executive function skills.
We also have several new projects that are logical extensions of the OCHL study and team. One NIH-funded project, Complex Listening Skills in School-Age Children with Hearing Loss, is a collaboration between Boys Town and Iowa that is in its sixth year and is focusing on identifying the mechanisms that support listening in classrooms, public places, and social settings where children with hearing loss must often communicate.
Our team at Boys Town also has a collaboration with the University of North Carolina and Case Western Reserve University where we are developing and validating a closed-set speech-recognition test that can be given in either English or Spanish. This project is crucially important because we have so few outcome measures in Spanish and other languages and a shortage of audiologists who are bilingual to administer them.
I am grateful that I get to do this work and collaborate with such amazing people on these projects. I never could have expected that my early science experiments in the garage could have led me here.