Can Hearing Aids Affect Cognition? New Research from Starkey
Carolyn Smaka: Brent, it’s great to catch up with you. Since your study on listening effort was published in 2009, this has become a hot topic in the audiology. We’re looking forward to your webinar on the topic in April as part of a 3-part series on new hearing aid research from Starkey. Can you give us an overview?
Brent Edwards: Yes, I’d be happy to. We’ve spent years focusing on understanding issues facing people with hearing loss beyond audibility and speech in noise issues. Namely, we’ve been interested in the impact of hearing loss on the cognitive ability of people with hearing loss, and whether or not hearing aids have an effect on cognitive function. We started with collaborative work at UC Berkeley, developing a method for measuring listening effort that has been cited well over one hundred times by other cognitive scientists today. That laid the groundwork for this kind of thinking.
We have continued our research along that route and the upcoming webinar will review what the issues are with hearing loss and cognition. Why does hearing loss have an impact on cognitive ability at all? It may seem counterintuitive that damage in the cochlea should have an effect on the auditory cortex and impact things like working memory, but it does. I’ll discuss these issues within the framework of auditory scene analysis. From my view of auditory perception, one of the first complex stages of auditory processing is creating an auditory scene. The auditory scene is the process by which we organize sound into perceptually meaningful events. The auditory scene is the beginning of auditory analysis, and it sets up the whole system to understand the world around the person. It is not only a first stage for understanding words, but also a first stage for comprehension, connecting with people, remembering things, and allowing the listener to do multiple tasks at the same time.
If there are any difficulties in the process due to hearing loss, there is a chain reaction and the whole system is impacted. In my talk, I will try to create an understanding of that chain of events and the links between each stage in the process. This can give us insight into the difficulties that people with hearing loss have, beyond simple audibility and understanding speech in noise.
I will also talk about some of the research worldwide that has followed from our initial listening effort experiment. Then, I’ll move on to some of the more recent experiments that we have done, specifically those looking at whether hearing aid technology can help the issue.
Sridhar Kalluri, PhD
Carolyn: This is a fascinating area and we’re excited to hear about the emerging data. The June webinar in the series will be presented by Dr. Sridhar Kalluri and covers binaural hearing. Is this an area you are also investigating?
Brent: Yes, and for this research, we are developing new outcome measures. These are new types of speech tests that are quite different from traditional audiological speech tests that have been used both in clinics and in other research. We are looking at the effects of binaural hearing on cognition, to understand if it provides better restoration of binaural perception for people with hearing loss, and its impact. Sridhar will talk about binaural perception and the effect of hearing aids on binaural function. Clinicians will be very interested to learn that we’re finding a relationship between poor binaural hearing and cognitive ability. We know there are also other more basic functions, such as localization, that are affected if you do not have good binaural function. Ultimately, it is about this very complex auditory system and how it all integrates into the creation of an auditory scene. The cognitive system uses the auditory scene to process the world around, and binaural hearing plays an important role in that. I will talk about that from the perspective of cognition, while Sridhar will talk about it from a broader perspective beyond cognition.
Carolyn: It reminds me of Carol Flexer’s mantra, “It’s all about the brain”, when she refers to the impact of amplification and auditory stimulation on the developing brains of young children with hearing loss. Your research shows us that it is still all about the brain in adults who may have developed hearing loss later in life.
Brent: Right. An analogy I have used in the past is that the brain is a highly evolved system and one of the best-engineered systems that has ever been created.
I liken the brain to a finely tuned and engineered Ferrari engine that is capable of amazing speeds and amazing performance. However, if you feed that engine poor grade gasoline and throw some dirt and water in too, that engine will not function nearly as well as it should. I view the effect of hearing loss on the brain in the same way. If you give it poor input such as distorted and inadequate auditory information, it is going to have a hard time doing what it has evolved over tens of thousands of years to do so automatically and effortlessly. It is going to take effort and it will not function as well. Hearing aids need to clean up the gasoline and provide high performance fuel again, so that the brain receives quality information that it needs to do its job.
Carolyn: That is a great analogy to use with patients when we are talking about hearing aids.
Brent: I think it will resonate with our patients. They do not come in to the audiologist’s office saying they have a harder time hearing soft fricatives and high frequency consonants. They say when they are at a family function, they have a hard time focusing and they get tired. That is cognitive ability. They are not talking about audibility; they are concerned about the impact hearing loss has on their higher processing and cognitive functions.
Carolyn: How does the Acceptable Noise Level (ANL) tie into all of this? I know that you are doing research on the ANL, and that Dr. Karrie Recker will present a course in this series on this topic.
Karrie Recker, PhD
Brent: I am pretty excited about the Acceptable Noise Level as a tool for the audiologist. We started a series of research experiments several years ago to understand the psychological meaning behind an ANL score with patients.
When we started these experiments, we thought that there were two things that were interesting about the ANL based on Nabelek’s study in 2006. She indicated that the ANL could be the only predictor that we have of patient success with hearing aids. Success in this case is defined as whether patients wear their hearing aids when they are needed. That is interesting in and of itself, because there are not a lot of means to predict whether a patient is actually going to wear their hearing aids or not. The second finding that was interesting to us was how two people with the same audiograms could have very different ANL scores. We can see differences of up to 20 dB, which is enormous. That was difficult to understand and it seemed like there was something beyond the auditory periphery causing these very different ANL scores in people with the same audiograms. I wanted to understand what it is that drives an ANL score, or what is the perceptual basis for the ANL, so I could then understand what the perceptual basis is for being a successful hearing aid wearer. If we understand that, then we can perhaps we can either create a clinical fitting process or design technology that is specifically intended to improve patients’ success with hearing aids.
However, if we do not understand what is behind the ANL, it is not as clear as to how to incorporate it in clinical practice. How do you treat patients differently because you have measured their ANL score, and how do you help all patients succeed with amplification? We may know how to measure ANL, and we know there is a relationship with hearing aid success, but why does someone have the ANL score that they do? There was a lack of a scientific understanding of it. That led to a series of experiments that we did that Karrie will detail.
Without giving too much away, let me just say that through a series of experiments, we were able to figure out what it is that makes someone have a good ANL score and what makes someone have a bad ANL score. Particularly regarding people who have bad ANL scores, as they are at risk to not succeed with amplification, this is tremendous insight for audiologists. Now that we understand the psychology behind the scores, we can use the information in a meaningful way to provide individualized treatment and help our patients become successful hearing aid wearers. Join us for Karrie’s course to hear the details.
Carolyn: Otherwise, you fit, verify, counsel and hope for the best during the trial period where you know the patient is at risk for non-use or a return for credit. This sounds great.
In addition to the research you and your team will be covering in the upcoming webinars, what other research is happening at Starkey?
Brent: In addition to research on these topics, we’re developing signal processing algorithms, and we have some pretty interesting projects on new tools for audiologists in the clinic. We are still in the research phase so I can’t provide more details, but if the research is successful, audiologists will have more powerful 21st century tools to use. Attendees of the Hearing Innovation Expo may have seen some of these ideas in the Concept Office.
We are also continuing to work with UC-Berkeley and their psychology department on the development of realistic outcome measures for hearing aids. We developed a new speech test that simulates a real multi-talker environment, where the outcome measure is not how many discrete words or sentences were understood, but a comprehension test. Are you able to follow a story, and easily switch your attention from one person to another? These are the kinds of things that people with normal hearing take for granted when we are surrounded by multiple conversations, but can be a challenge for people with hearing loss. This new test really gets at measuring binaural and cognitive functions in more realistic environments.
At Starkey, we have about 50 people in research, with about 12 people in our Berkeley center and the rest at headquarters in Minneapolis. We have a variety of projects focused on signal processing features to improve speech understanding in noise, and on mechanical transducers to provide enhanced audio quality or better usability of the hearing aid, which is important for patient satisfaction. We know that outcome with hearing aids is not just about audibility and speech understanding or even cognition, but things like usability are also important. We also have a whole audiology research group that is looking at things like aural rehabilitation tools, and how to make new user experiences better. They are looking at ways of integrating mobile phone apps and online capabilities such as with mystarkey.com, in order to better connect the audiologist with their patient and to provide a better overall experience for the patient. It is about continuing to improve patient satisfaction and use of hearing aids, so that patients can stop thinking about their hearing loss and focus on getting back to their lives. Ultimately, it’s about improving lives.
Carolyn: What a wide scope of research! We look forward to the upcoming talks, and to further updates from Starkey research. Thanks, Brent. Here are the course links again for readers who would like more information:
Brent: Excellent. It was great talking with you and we’re also looking forward to the upcoming talks on AudiologyOnline.