Early Identification of Hearing Loss in Adults and the Limitations of the Audiogram: Interview with Courtney Coburn Glavin

Brian Taylor 0:10
Hi everybody, welcome to another edition of This Week in Hearing. I’m Brian Taylor. And this week we’re going to be talking about identifying the early signs of hearing loss in adults, and why it’s important that we might want to redefine the audiogram. And that my guest this week is Courtney Colburn Glavin, who’s a PhD candidate at Northwestern University in Evanston, Illinois. Courtney, welcome to This Week in Hearing.

Courtney Coburn Glavin 0:35
Thank you very much, Brian.

Brian Taylor 0:38
Well, I know you’ve done some really interesting research in this area that was published in Jaro, which you can explain a little bit, it’s not exactly top of mind reading for most audiologists out there. But nevertheless, it’s a really important bit of research that you’ve done. But before we get to that, I thought we would start by having you first. Tell us a little bit about yourself. And what prompted you to get a PhD in audiology at Northwestern?

Courtney Coburn Glavin 1:06
Sure, um, yeah, I fell into audiology the way that many people do. As an undergraduate at Northwestern, I was interested in pre med, ended up becoming a CSD or communication sciences and disorders major, and took an intro to audiology class. And the rest was history from there after that class. I then did my AuD, and ended up working a few years clinically and in industry. And ultimately, after those experiences, I decided I wanted to go back for a PhD because despite the fact that we have a lot of power and potential as audiologists, I saw that our diagnostic tools and treatment options had limitations. And so I ultimately returned back to Northwestern. Now I’m a PhD candidate working with Dr. Sumit Dhar, and I’m primarily interested in age related hearing loss and how we can better diagnose that hearing loss.

Brian Taylor 2:07
Well, that’s probably another a good place to start. So let’s talk about age related hearing loss. You know, I know that you probably can talk more about this. Many clinicians out there see patients that are, let’s say middle aged, that maybe have a normal pure tone audiogram, but have many self reported hearing difficulties. So maybe you could talk a little bit about how prevalent that type of condition, age related hearing loss in general is, and just how prevalent it is to have a normal audiogram with those kind of deficits.

Courtney Coburn Glavin 2:39
Sure. If we start by talking about the prevalence of age related hearing loss, I think that kind of puts things into perspective about how important it is that we address these issues, because it’s estimated that about a third of people between the ages of 65 and 74, have some degree of hearing impairment. And that number goes up and it goes to one in two or half of people above the age of 75, estimated to have some form of hearing impairment. And in the US alone, that equates to roughly 30 million or more people who today are experiencing age related hearing loss. And with the population aging both in the US and globally, we can think about this is, we can think about the fact that this is only likely to get worse in the coming years. And age related hearing loss is obviously a real issue. And I think that researchers and clinicians alike are well suited to try to address this issue.

Brian Taylor 3:43
Right. Well, I already mentioned, you know, these middle aged people, let’s say 45 to 65. And that clinician see a fair number of them that have self reported hearing difficulties. But in my own experience in the clinic, you’re doing case history on a person like this, you think this person’s gonna have a pretty significant hearing loss, and then you put them in the booth and you find that their audiogram is essentially normal. I guess the obvious question is, what does that say about the audiogram?

Courtney Coburn Glavin 4:11
Yeah, I think that’s a great question. And I think any clinician would be able to describe at least one or two patients that they’ve seen that is the experience you just described, where they put them in the booth, tested their hearing, and everything is normal. And that does not at all align with what the patient has reported about their experiences. And I think this brings up a couple of limitations about the audiogram. I think I first have to say that the audiogram is a really useful tool, and it’s key for audiologists to use and being able to find a person’s thresholds or the softest sound at which they can hear across a range of frequencies is really important information. But think in the back of our minds through all this. We have to remember that the audiogram isn’t and shouldn’t be the end all, be all. And one obvious flaw that we can start with is the fact that the audiogram, generally, at least traditionally used in clinic, only measures out to 8000Hz, despite the fact that the range of human hearing extends up to 20,000Hz. So we’re missing a lot of information when we only test out to 8000Hz. And in the context of age related hearing loss, that’s really important, because we know that age related changes in hearing tend to first occur at those highest frequencies of human hearing. So we’re really missing a lot of information there. Another limitation that I would say is worth mentioning, is the fact that we’re only assessing threshold when we use behavioral audiometry, or when we’re looking at the audiogram. And so, again, that’s an important piece of information. But we’ve learned from more recent work, that there’s more to auditory function than just how someone is doing at threshold or for very soft sounds. So for example, there’s well known workout of the Kujawa and Lieberman laboratories, that’s showing us that auditory nerve fibers, for example, that are responsible for coding above threshold sounds may be damaged in when they’re exposed to noise for certain periods of time. And some have also thought that this might be related to why some people have problems understanding speech and noise, for example, even though they might have a normal audiogram. So essentially, this is telling us that there’s more to the auditory system than just how we hear soft sounds. And I guess the final thing I would talk about there is the fact that there are flaws with how we define, quote, unquote, ‘normal hearing’ on the audiogram. And Andrea Gatlin and Sumit. Dhar, from our laboratory here at Northwestern, have a really great paper in AJA, about this from 2020. And they talk about the history of the definition of normal hearing and how it came to be and the implications of this definition. And in essence, the 25 dB HL cut off that’s traditionally used to define normal hearing was defined pretty arbitrarily. And importantly, when we think about auditory aging, the auditory system doesn’t follow these categorical barriers, like you’re not young, one day and old the next day. age related hearing loss is a gradual process and decline. And it’s not something that magically happens overnight, as there’s also not something magical that happens once you have a threshold that’s above 25 dB HL. And so, you know, all of these things are telling us, we should not put all of our eggs into the audiogram basket, I think we’re not routinely measuring above 8kHz, we’re not routinely assessing suprathreshold function. And the definition of normal may be incorrect. And so can we kind of step back and look deeper? And is it possible that people who are normal on the audiogram actually aren’t normal? Are they, or do they have some kind of auditory dysfunction?

Brian Taylor 8:43
Right, well, a couple things. First, I’m glad you mentioned that there’s still some value in the pure tone audiogram. Maybe from a medical perspective, when you think about pure tones, air/bone, speech, immittance audiometry, I think that constellation of tests are helpful for diagnosis, pretty essential. So we don’t want to forget that. Also, I’m glad you mentioned the that paper in AJA, American Journal of audiology published two years ago by Professor Dhar and I guess one of your fellow PhD candidates,

Courtney Coburn Glavin 9:16
AuD student,

Brian Taylor 9:17
AuD student. Okay.

That’s an excellent paper. I was gonna mention that to you really some useful information there about the history of the audiogram. Just how arbitrary it is. And it’s been around for such a long time and how limited it is. But anyway, I’m glad you mentioned that. But let’s go ahead and jump into your research. I think one of the more eye opening things and you can get into this is you mentioned the aging process. And based on my reading of your research, I think it may be starts a lot earlier than we want to acknowledge. So maybe tell us a little bit about your research with DPOAEs.

Courtney Coburn Glavin 9:57
Sure. So, our primary clinical question was, essentially, to look at DPOAEs and see if they could tell us something more about the auditory, the auditory system, excuse me, and people who have normal hearing on the audiogram. And for those who I guess we should step back for a second and just briefly talk about DPOAEs. I study OAEs pretty extensively, so we could probably have a three hour podcast about OAEs. No one would listen to it.

Brian Taylor 10:35
No, there’d be a few of us out there that woud maybe DPOAE, you’ve been using this term distortion product otoacoustic emission, and maybe you can explain what that is exactly.

Courtney Coburn Glavin 10:44
Yeah, exactly. So, distortion product otoacoustic emissions are a type of otoacoustic emission or OAE. And an OAE, in general is basically a sound that your ears make. So we can actually play a stimulus or a sound into the ear, and measure or response back out of the ear that we didn’t, a sound that we did not put in. So your ears are actually making sounds if, if they’re healthy, and DPs in particular are one type of otoacoustic emission that we measure by playing two tones in simultaneously. And we think that DPOAEs in particular have the potential to be a valuable tool, when we’re talking about kind of supplemental things, tools to use, in addition to the audiogram, or in lieu of the audiogram. And we think it’s pretty powerful. We think DPOAEs are pretty powerful for a couple of reasons. One, because they’re already used clinically. So a common application today is in newborn hearing screenings. So the equipment, the framework, the general knowledge about OAEs is already there. And two, we know from previous work, that DPOAE’s tend to decline with age. But the caveat to this previous work is that generally it has looked at DPOAEs only in people who already have declining thresholds on the audiogram. So they already have a little bit of hearing loss. And at that point, it’s pretty difficult to disentangle the DPOAEs from, from the audiogram. Right. Um, and another caveat is that DPOAEs in both research and the clinic tend to just be measured at one stimulus level, or maybe a couple of stimulus levels. And just like assessing just threshold on the audiogram isn’t telling us everything, probably assessing just one or two, two stimulus levels with OAEs can’t tell us everything about the function of the auditory system either. What we tried to do in this study is a) only look at DPOAEs in people who have clinically defined ‘normal hearing’. So we used a very strict definition of that or and cut off. And then the second thing that we tried to do was a look or that we did was look at DPOAE growth functions, which is basically looking at DPOAEs measured across a range of stimulus levels, to really try to look at a wider auditory function over a wider dynamic, a wider range.

Brian Taylor 13:39
Right. So maybe tell us a little bit about the design of the study what you were, you know, how you conducted the study the population that you look that was evaluated?

Courtney Coburn Glavin 13:50
Sure. So in essence, we took a bunch of people from a database that already existed as part of a larger study that was conducted by Dr. Sumit Dhar and Dr. Jonathan Segal at Northwestern. So in this large database, there were 1000s of people. And we selected those for analysis only who had normal clinical thresholds, like I said, We lumped these people into age groups, by decade of life, so we looked at 10 to 19 year olds as our baseline age group, and of like the, normal, the young, healthy ear. And then we looked at progressively older age groups, 20 to 29 year olds, 30, to 39 year olds, etc, all the way up to what we called the 50 plus year old age group, which included 50 to 59 year olds, and then a couple of people in their 60s, and I think it’s telling to begin with that. We could only find a couple of people in their 60s who had normal behavioral thresholds, but that’s kind of a side note. Yeah, so, so then we had all these people lumped by age group, and we looked at their thresholds on the audiogram. And we looked at their DPOAE growth functions.

Brian Taylor 15:13
And what did you find?

Courtney Coburn Glavin 15:17
Essentially, we found that DPOAE growth functions decline significantly and systematically with age, even in these people who have perfectly normal audiograms, and ‘normal’, I should put in quotes. And I think very interestingly, we saw that these declines show up in people as young as 30 years old. And this decline was greatest at the highest frequencies that we tested in the study. So a couple of things. I mean, we generally don’t think of age related hearing loss as being a problem for somebody until they reach the age of 60, 70, etc. And to see these systematic and clear declines in DPOAEs in people in the fourth decade of life, so aged 30 to 39, is really, really astounding. Because if these people in any of age groups that we tested, went into the clinic today and had an audiogram done, it would be normal. And that is a big issue, but also a big opportunity. I think for us.

Brian Taylor 16:34
Well it’s a little bit depressing to think that you start to have a note that you have a decline in your hearing when you’re in your 30s. But, the science is the science as they would say, but from a clinician standpoint, it’s good to know that kind of an off the cuff question I have Courtney is, what would a clinician, you know, given the limitations of the audiogram, as you mentioned, you wouldn’t see these patients should really necessarily show up on a audiogram result, are there other tests like maybe QuickSIN quick speech in noise tests that might give you an indication that this person is, you know, starting to show a decline in their hearing? What are your thoughts on that?

Courtney Coburn Glavin 17:18
Yeah, I think that’s a really good question that we could unpack a lot. I don’t know the answer, because we did not look at any functional measures of hearing as part of this study. So you know, there’s what we can measure in the clinic, and then a patient’s functional experience. And those are two different things. However, I do think that it is possible and likely that these people have or are starting to notice problems, whether the QuickSIN in particular could detect that is a long conversation to be had. But I think, kind of using those other clinical tools that maybe we don’t rely on us heavily traditionally, like QuickSIN is an important step for clinicians. You know, because when a patient comes in telling you that they have a complaint, we need to figure out as best as we can, what’s going on and try to help them and think outside of the box a little bit.

Brian Taylor 18:21
Yeah, I know that there was an article, I think it was also in American Journal of Audiology. It was a survey done of clinicians, that was like 200 clinicians around the country, about this hidden hearing loss or subclinical hearing loss. And I don’t remember exactly, but it’s routine for clinicians to see these patients with normal audiogram and self reported difficulty. But one of the other findings in that study was something like a third of the individuals when you informed that they had normal told them they had normal hearing, they were really frustrated by that result, because you weren’t able to kind of identify the problem that brought them into clinic. So it’s an interesting finding. But you mentioned before a lot of clinicians have distortion product otoacoustic emissions in their, in their clinic, would they be able to use that equipment to kind of get some of the same results that you got? Because it would seem this growth function is not exactly something you could tease out of in a routine clinical visit?

Courtney Coburn Glavin 19:22
Sure. And I wouldn’t necessarily say that all clinicians to start measuring growth functions today, because there’s a lot more that we need to understand about them, including how individual variability impacts growth functions, but then stepping away from the details of the research a little bit. I do think that OAEs could be used today in patients who are coming in with normal hearing, or a quote unquote ‘normal hearing’ on the audiogram. If they’re complaining of something and they want more answers, I do think that if your monitoring someone over time. OAEs are a potential tool that a clinician could use. And there’s not necessarily something special that they need to do to use that tool today.

Brian Taylor 20:13
Right. Well, any other guidance that you have for clinicians that are trying to identify these types of patients early on?

Courtney Coburn Glavin 20:24
Yeah, I would say that, again, it’s all about listening to a patient’s experience and knowing the limitations of the audiogram. And even though we can’t address every single limitation of the audiogram, with the tools that we have available today, there are there are still things that we can do. I think any audiologist that’s practicing would be the first to tell you that just because two different people have the same audiogram doesn’t mean that they’re going to have the same experience in day to day life. And the experience that the patient ultimately has, is going to be impacted by a lot of things, including kind of what types of environments they’re in, but also what’s actually going on under the hood in their auditory system. And it’s up to the clinician, I think, to establish personalized care for the patients, and not just tell them, they have normal hearing come back in five to 10 years. Ultimately, that type of patient is going to be the one that leaves the clinic still has difficulty and then is searching around on Google and finds a solution that’s likely to be suboptimal for them. So I think trying to work with these patients and finding options for them that might not be the traditional route is what is needed.

Brian Taylor 21:50
Right. I know, the point of I’m curious, what’s your take on interventions for these individuals? I mean, obviously wanted on a case by case individual basis, but is it beyond the pale to fit hearing aids on patients like this? Are there any other kinds of you know, interventions that might be on the horizon? What are your thoughts?

Courtney Coburn Glavin 22:13
Yeah, as far as current interventions like hearing aids, I don’t think it’s necessarily outlandish to say we could fit someone with like a 25 dBHL hearing loss with a mild gain hearing aid, whether or not that would be appropriate for them and would work for them and be valuable for them is going to be like a conversation the audiologist needs to have on a case by case basis, I wouldn’t really recommend that everyone get fit with a hearing aid. So there’s that, then we can also consider things like PSAPs, or over the counter devices that are coming out. I mean, perhaps those types of things will be appropriate for patients who are experiencing some difficulty in some situations, and need a little bit of help but don’t have the money or don’t want to commit to hearing aid traditional hearing aids. And so that’s kind of the landscape today. But further on down the line, I think we also have to start to reimagine what treatments for hearing loss might look like in a decade, two decades, three decades from now. Stem cell and genetic therapies, emerging. And really, I mean, those are our reality now and going to be a reality on the market very soon. And imagine a world where a patient is coming in, not at age 70, when they’ve already been having difficulty for 10 years communicating with their loved ones, but at age 30, saying, I want to make sure that my hearing is looking good. Let’s start monitoring now. Am I a candidate for these types of treatments, etc, etc. And I think the audiologist has an important role to play there.

Brian Taylor 24:09
Right, I think that, that is a something to be excited about. If you’re a clinician, and especially if you’re a younger adult who is concerned about your hearing, I do know that This Week in Hearing in the next month or so is going to be having a couple of episodes with some of the startup companies that are bringing some of these pharmacological interventions to market. So that’s exciting. And I think your work is kind of setting the stage for why these interventions would be so useful. Yeah. Now that we’re kind of wrapping things up, Courtney, any other any other information that you want to share about? This DPOAE study that we’ve been talking about. For those of you that want to read the study, I can tell you it’s in the journal The Association for Research in otolaryngology Jaro, J-A-R-O, and not a lot of folks probably read that. But, uh, it’s, uh, you know, very, it’s an excellent journal. Congratulations for getting that study published in that. But do you have any other final thoughts on the work you’ve been doing in this area?

Courtney Coburn Glavin 25:23
Thank you. I guess my final thought is this: If you’re not someone who reached Jaro, I don’t blame you necessarily. I know that that’s not the most accessible journal for clinicians. However, I do have a full text link that I can send to anyone who is interested in reading it. And I’d also be happy to chat about the findings in more detail with anyone who’s interested to they don’t have to do a deep dive into DPOAEs, like I said, but we can talk through anything that someone wants to talk to, talk through. And I guess the final thing I would say is that, is just reminding everyone how important age related hearing loss is to address and keeping in mind the limitations of the audiogram. When a patient comes into your clinic, how might you treat them differently than you have treated someone else in the past and in using out of the box approaches? I think is going to be very valuable.

Brian Taylor 26:28
Yeah, what’s really interesting from my perspective about this topic is that so I became a clinician back 30 years ago in the early 90s. And at that time, there was a lot of energy, a lot of interest in using OAEs for infant screening. And now you’re seeing that same kind of commitment, that same type of energy to look at age related hearing loss and younger and middle aged people. It just kind of shows you how audiology evolves and how our thinking shifts and moves from one area to another. So it’s an exciting time to be involved in the profession. And, Courtney, we can’t thank you enough for all the great work you, professor Dhar and others at Northwestern University are doing.

Courtney Coburn Glavin 27:10
Thank you very much. And again, I’m glad to be here and talk about it with people.

Brian Taylor 27:14
Again, Courtney Coburn Glavine, PhD candidate Northwestern University. Thanks for sharing your insights on your research.