Hearing Loss and Cognition: What Does the Research Actually Tell Us?

Brian Taylor 0:10
Hello, and welcome to another edition of This Week in Hearing. I’m Brian Taylor. And our topic this week is hearing loss and cognition. What does the research tell us? I’m here today to discuss this important topic is Danielle Powell. Danielle is both an audiologist and an epidemiologist at Johns Hopkins University School of Public Health. Dr. Powell, I want to welcome you to This Week in Hearing.

Danielle Powell 0:33
Thank you for having me.

Brian Taylor 0:34
And before we dive into the topic, I just want to let our audience know that what piqued my interest in this was a couple of things. Actually, I saw you and your team had an outstanding podium session at the February American auditory Society meeting. And then around that same time, I read a paper that you published in, I think it was Frontiers of Aging Neuroscience, not exactly something that rolls off the tip of the tongue of an audiologist. But it’s a really, I thought it was an excellent kind of overview of research the direction we need to go. And anyway, before we dive into that, I thought, if you could maybe share a little bit about your background And what has interested you in this topic of combining hearing loss and cognition.

Danielle Powell 1:23
Sure, yeah, absolutely. So my background as an audiologist actually more started with more direct training in pediatrics, I was on some various trainings, traineeships during my AuD program, and then did my clinical externships at a children’s hospital. So I’ve kind of found my way into focusing on older adults and hearing, you know, some of my first jobs out of school was on working with primarily older adults in a city based setting. So kind of a broad range of a patient population, which was really informative, it kind of led me towards the path that I’ve currently ended up on. Yeah, I was getting patients from across income levels from across educational backgrounds. And I was starting to get questions from my patients. And then thinking about, well, how does hearing loss affect me as I’m aging? as I’m getting older, both as a professional as I retire, different things that they were considering and realizing that we don’t know as much about what hearing loss and how it impacts aging, we know a lot about it in kids. But the strength of the research that we know and older adult isn’t isn’t quite as much there. And I was working at a time when a lot of the research on hearing loss and cognition and dementia was really picking up steam and getting picked up by mainstream media and news outlets as well. And so my patients were coming in with these questions. And all of this kind of led me thinking about, you know, hearing loss from a broader approach a life course perspective, so to speak, and what does that mean for us as we age and what can we do about it? And that’s what kind of led me towards the research that I am now part of it was the the research group that I was able to join at Johns Hopkins, this was one of the primary areas of research that they were focused on. But it really tied in nicely to some of my own areas that I was kind of developing just from this anecdotal experience as well.

Brian Taylor 3:12
I see. Well, I think like a lot of clinicians out there, I have what I think is kind of a cursory knowledge of the relationship between hearing loss and cognition. But one of the things I really liked about this recent article that I cited, was that I thought you reviewed quite nicely some of the more recent findings, that that talk about this linkage. So maybe if you could get our colleagues out there in the clinical world, up to speed on some of the current findings that talk about this linkage between hearing loss and cognition.

Danielle Powell 3:43
Yeah, absolutely. So um, one of the things that I referenced a lot in that paper that really has does the best job that we have so far, and summarizing the strong evidence that we have, was done by a large commission from the Lancet, which is a very well known, highly, highly reputable kind of health related journal that had a commission both in 2017, and then 2020, they updated their report on dementia prevention, intervention and care. And in 2020, they kind of really highlighted 12 identifiable risk risk factors for dementia that we could potentially modify, meaning that we could maybe do something about to where we could potentially delay or prevent cases of dementia. And most specifically, an interesting is that hearing loss was one of those12 risk factors identified, that also potentially has the largest potential for prevention of dementia cases, they estimated that maybe up to about 9% of dementia cases could be prevented by intervening on hearing loss. And in summary with that, you know, part of the strength of the evidence that we have has been the growing number of research studies that are supporting this association. Now, what’s been changing more recently is that we’re getting larger research studies. We’re getting a better understanding across a broader population of the strength of association. And what we know so far is that it has kind of led to three to four different kinds of theories of why do we see- why are individuals with hearing loss at a greater risk for either cognitive decline or dementia? And there’s some theories kind of driving that. So some of you might be familiar with this. But it’s important when we think about, you know, what do we do about hearing loss that might lead to dementia prevention, for example. You know, one of these theories is that there might be something that we call a common cause. Which that leads to both hearing loss and dementia, this could be something like neuro degeneration of the brain like vascular, vascular-related factors that can impact both, or maybe a genetic related component that can impact both there’s a lot of kind of emerging research about the genetic aspects specifically that we still just don’t really understand. It’s also this idea of that we call some people have called the social- social deprivation. For example, I’m sorry, sensory deprivation, for example. And this idea that more recent lab based medical imaging has really kind of helped support is that with prolonged sensory deprivation, or have auditory deprivation, in particular in the brain can lead to changes in brain structure and function, decrease synapses, that sort of thing that can really impact the already existing dementia related pathology that’s existing in the brain and kind of lead to this presentation of cognitive changes with dementia symptoms. You know, that’s more of a direct permanent change to the brain. Additionally, there’s more of kind of an indirect maybe we can actually do something about these changes thought process. That leads to the idea that this impaired speech signal that’s going up to the brain, enough difficulty with speech and noise, taxes the cognitive processing and ability that we already have an idea that is commonly called your cog… it’s like leads to, takes into account what we call your cognitive load, I’m trying not to throw a lot of jargon out there. But sometimes I trip myself up, as you can guess. So your brain’s and your cognitive processing ability to kind of compensate for changes in cognition, that pathology that might already be there, you know, when you have a hard time and need to focus a lot more and challenging listening environments, for example, that takes away from that cognitive processing and ability. Another thing that we’re starting to the evidence is a little bit more more mixed. But we’re seeing kind of this continual connection and association in studies is that that of social isolation, or decreased social engagement, we all know that with hearing loss, you can, an individual can become more isolated withdraw from that social engagement and interactions with others. But that type of interaction and engagement can really be protective against cognitive changes or dementia.

And so there’s kind of these overarching theories of why might we be seeing this greater association between the two, most likely more than one of these are at play, it could be all of them, we don’t really know. And that’s what a lot of this research is really starting to try to tease out a little bit more. What’s really starting to change more recently is the strength of the research that we have. So there are some, you know, a lot of these studies are based on what we call observational data. So it’s where we’re taking a group of people in public health and epidemiology, that’s a population based level, so not an individual level. And we’re trying to make an understanding of you know, I have given exposure hearing loss, for example, I want to understand, you know, are you at a greater risk, are you more likely to develop dementia, we can’t necessarily control for all of these other factors. We can’t give someone hearing loss, we can’t give someone a hearing aid necessarily. That type of strong evidence is comes from a clinical trial. And there’s a lot of those with longer standing studies where we have a lot more control of the environment that’s happening, that can give us the best sight and understanding. Specifically, I’m wondering about, you know, hearing aid use as an intervention for dementia or cognition later on.

Brian Taylor 9:05
Yeah. We’ll talk maybe a little more about hearing aids in a minute. But yeah, your explanation of those different theories, I think makes it much easier to see this linkage between hearing loss and cognitive function,

Danielle Powell 9:17
A lot of those, the other thing I want to point out as a lot of us are thinking about hearing loss, a sense in the sense of peripheral hearing loss. And there’s reason why there’s so much more evidence related to that, too, is because when we’re thinking about, you know, central auditory performance, central auditory function that is very much dependent on your cognitive abilities and cognitive processing. And so it can become very hard to tease out these differences of what contributes to where, but it’s really interesting when you think about, you know, what does that mean big picture on how someone functions. So the evidence that we have right now is on peripheral hearing, it’s easier to isolate the independent effects of hearing a cognition. There’s more interest kind of growing on the central auditory or a function ability and what that might mean for what we think about cognition and dementia. But it’s, it’s messy, and there’s a lot to kind of tease out. So with that,

Brian Taylor 10:08
given how the central auditory system works, I can see how that would be really tough to tease that out

Danielle Powell 10:14
Yeah. Yeah, absolutely.

Brian Taylor 10:16
So one thing I’m really curious about, and I think a lot of our viewers would be too, because I think they, they see they’ve, you know, it’s not this, this relationship has been talked about in our profession for at least a decade. Yeah. And I think the challenge, and maybe this is just me talking, but I think other people share this sentiment, and that is, how do you talk about these things, this linkage with your patients? Like, how would you talk about it? I’m guessing there’s probably a difference in how you might talk about this with somebody who’s maybe 60 versus somebody who’s 90 years old? So can you maybe share some insights with our viewers on how you would talk about this linkage in a way that’s understandable and relatable to patients?

Danielle Powell 10:55
Yeah, no, absolutely, um, you know, some of the things would be the same, depending on the age other things obviously, would be different. And some of it would also depend on, you know, the future research. And hopefully teasing out, you know, what pathway are we talking about, that relates to this association, because that would matter to, you know, we want to be careful about saying is, you know, it’s not accurate to say, you have hearing loss, you’re going to get dementia, that’s what’s not accurate, we want to be clear with our patients so that we don’t, you know, be alarmist or something like that. What we can say so far is that, you know, based on the studies and the data that we have, on average, what we’re seeing is individuals with hearing loss are at a greater risk, or potentially more likely to develop dementia later. But that’s thinking about a bigger picture level, we don’t want to take that information and put it on an individual. What our information does allow us to do is allow providers, primary care providers to try to have an understanding of those who might be at a greater risk of developing dementia later, and therefore thinking about ways that we can maybe mitigate that risk. So that’s my big picture of how we talked about it with patients, you know, you’re at a greater risk, it doesn’t mean you’re necessarily going to get dementia, but maybe these are some things that we can do to potentially mitigate the risk that you’re here in my present. Now, that being said, you know, there’s a lot of studies showing hearing aids, hopefully, the strength of those studies, again, is going to be supported even further in the coming year or two with the clinical trial evidence that will be out, cochlear implants too we’re seeing some emerging studies that are still limited, but that are supporting improvements for dementia patients with cochlear implantation as well. You know, for some of your younger adults with hearing loss, there’s a lot of things that you can talk about. One is simply well, actually for any age, you know, hearing and dementia is one thing. But we also are seeing more and more evidence to support that treating or managing hearing loss has a broad impact on your quality of life, not just with cognition, but with depression, with isolation, with falls, there’s a lot of different things that your hearing can impact and one of my primary goals is to help other people, both patients and other professions, have health care professionals kind of understand that. So for your you know, for your younger patient, for example, one of the biggest things is treating hearing, if they have hearing loss, understanding that the earlier that you do something about it, the better we say this all the time to our patients, but where there’s more and more evidence to show, you know, especially with some of those pathways that I talked about, prolongs sensory deprivation and can lead to changes in the brain structure and function. That’s something that once that happens, we can’t necessarily do anything about. Alternatively, you know, the other pathway that I talked about where it’s this increased cognitive load this taking away of your cognitive resources that you have to kind of support you in other areas that can be beneficial at any age, you know, whether you’re a younger adult and a working professional, or you’re an older adult who’s already demonstrating some changes in cognition, to making it easier for you to hear, allow some for more of that cognitive processing in the general environment. Same thing with social isolation and that kind of thing that can help at any age. Well, we are seeing that I think a lot of providers and even patients and particularly caregivers, is important to know is that even for those with already presenting cognitive changes, dementia, various stages, we are still seeing some benefit from management of hearing loss. But that benefit really does come when you meet the patient and the family where they are. You know, for some people, that’s a hearing aid for other people’s that might be a pocket talker. But what is more evidence is showing is that there’s improvement in depression, anxiety, those kind of more negative dementia related behaviors that can be really challenging for families and providers to kind of work through. There are some studies that are starting to show that some of those can be decreased as well with hearing with hearing intervention. So the end of the day can really help at any age, but We don’t yet know is, you know, it’s a little bit pathway specific. And that’s where a lot of research can really help us kind of individualize and target, what might be the best for people. But lots of research to account for that. So yeah.

Brian Taylor 15:14
Another question I wanted to ask you is, you hear a lot about dementia, like the Lancet study mentioned, they talked about dementia. And then other studies, in other places, they talked about cognitive decline. Could you help us better understand the difference between those two?

Danielle Powell 15:29
Sure, yeah, absolutely. It’s nuanced. And it’s tricky. And you know, there’s no cut point across all of it, you can think about cognitive abilities for adults are really any just kind of a continuum. They go from this normal cognitive abilities with age to dementia, or more severe dementia, and anyone can fall kind of anywhere across that continuum, there are, you know, cognitive decline specifically then would be represented change in functioning from a person’s prior ability, and that prior ability matters all not starting at the same place. You know, there are certain expectations of how a person might function based off of their age and education level, we expect some changes to happen with age, just as the brain is taxed over many years, there’s a lot of health, environmental, all kinds of factors that can come with that. And so cognitive decline is kind of representing a change over time. Now that change can be you know, more minimal, it can be severe to, like dementia, like it indicated, there’s this phase kind of in between those that’s called mild cognitive impairment. What that is, is kind of thinking about, you know, the someone’s it’s a symptomatic phase of dementia. So various aspects of dementia can kind of the pathological changes can be happening kind of quietly word or in the in the background, so to speak, where someone’s not actually demonstrating any clinical presentation. But mild cognitive impairment is where they’re demonstrating some brain changes. It’s not exactly interfering with independence, but the family, the individual is noticing something different, you know, someone progresses to dementia, where there’s changes are substantial enough where it’s interfering with their independence and their ability to kind of function day to day, all of this is determined, again, there’s not a clear cut point. It’s very, it’s a complicated kind of determination that goes from, you know, a physician’s interview neurocognitive tests, if it’s available, some lab work, or imaging, it’s a kind of a compilation of information and based off of expert opinion, you know, there’s a lot of some changes in, in particular, I said, the imaging and the lab work that biomarker related changes, that are really starting to help us understand that underlying dimension where it could be coming from and how we kind of use that with the clinical presentation is one of the things that there’s a lot of new work that’s happening, and maybe one day, the you know, what we can contribute in the hearing world might be able to kind of fit into that puzzle piece. But that’s what we’re still under. And it was well, interesting.

Brian Taylor 18:00
Well, I have more of an epidemiologic question for you. And you see this a lot in the in the research about odds ratios. And I think, in the in the, in that paper in that article from Frontiers in aging neuroscience, you talk about the odds for cognitive impairment, I think is 1.22. And the odds of dementia are 1.28. So can you unpack that for us? What… You know, I don’t want to go too far into detail here. But, you know, given your expertise as a researcher, I think you might be able to inform clinicians on what these odds might mean.

Danielle Powell 18:35
Yeah, so an odds ratio. You know, we say odds in papers Most commonly, and I’m gonna, I’m gonna generalize here, but we’re talking about an odds ratio. And so that means you could think about odds is like a likelihood. So your likelihood of having a given outcome, if you have hearing loss, for example, compared to those that don’t have hearing loss. It’s a point of comparison between the two. So one way that you can think about, like the Lancet Commission that I mentioned, had an odds ratio of 1.9 for hearing loss. So those who have hearing loss are 1.9 times more likely, for example, to develop dementia, you can also think about it as 90%, more likely, you know that what you referenced is I think I was referencing another study in that in the paper where it was 1.2 to 1.28. You know, an odds ratio of one means there is no, you’re not more likely you’re not less likely, there’s no real difference. Anything above one indicates that you’re more likely. So an odds ratio of 1.22 to 1.28 is not drastically different between the two, but it’s suggesting a higher likelihood. You know, to put it into perspective, you know, we all are well aware of the association between smoking and lung cancer. That Association has been referenced anywhere from, you know, an odds of 15 to 30, you know, a much larger scale than what we’re talking about, but I don’t want to downplay you know, our 1.2 or 1.9. That’s still important in the grand scheme of things. But it’s talking about like, how likely might you be in comparison that comparison point is always important in the, you know, statistical epi world, we always compare, we always are interested in who are we comparing to? I don’t know if that’s helpful. So yeah. And the difference is, again, that cognitive impairment, I think, is what I said versus dementia. That’s the specificity of impairment could be anything, it could be mild cognitive impairment could be dementia, versus that distinction is where what those were kind of getting out. And all of that matters to when we’re thinking about intervention.

Brian Taylor 20:31
No, that’s a good explanation. Thank you, that helps, especially to get that frame of reference from smoking to lung cancer. Yeah,

Danielle Powell 20:37
that’s that’s one that we’re all familiar with. Very established, ya know, that same paper, though, you know, they referenced the odds ratio for hypertension, which a lot of people are familiar with that being a risk factor for dementia and cognition. And that’s at 1.6. So at 1.9, our likelihood from hearing loss, I say are like, yeah, as a field are greater than what what has already been presented within hypertension, which I think is really interesting.

Brian Taylor 21:08
That is interesting. Yeah, I didn’t know I didn’t even I didn’t put the two together. That’s good to know. I wanted to ask you another question that I think you’ll be able to help our viewers with, and that is screening for cognitive function. That’s a kind of a hot topic in the field right now. What’s your advice to clinicians around – You know, should they add a cognitive screen to their clinical protocol? What are your thoughts on that?

Danielle Powell 21:38
Yeah, you know, I’m, frankly, I’m torn. I think that there’s a great opportunity for us to be included, and potential for audiologists to kind of help support our fellow care providers of primary care physicians, gerontologists, you know, those that have a similar interest of the general health and well being of our patients in mind, what I’m hesitant about is I don’t feel like we currently have the right pathway set up for this to actually be beneficial for our patients. You know, we I want to make sure that right now, there’s kind of a limited dialogue between ourselves and these providers that actually, we would do something about any screening that we have. So we wanted to make sure that one we understand what a screener is, how to interpret a screener. There are many different types of screeners that we have a connect direct connection and relationship with those like the primary care the gerontologist, those who specialize in these types of things, neurologists, for example, and that we understand how to communicate the results and how to communicate to those other providers as well. You know, if we, if we do a screener, and we get, you know, a score that would indicate some level of cognitive impairment, well, what are we going to do about it is my is what I’m wanting to make sure that path is in place. You know, there are some very well known validated screeners for general screeners for cognition, the mini mental state exam is one that’s used, commonly the Montreal cognitive assessment, those are commonly used, and have the potential that we could employ them, there’s been some studies that are showing the fidelity and validity of their use, and individuals with sensory loss to which is important. We want to make sure whatever we’re using, both within our population of those with hearing impairments, since most of those are an oral administration is maintained. Same thing for those who are, you know, for your geriatricians, we want to make sure that they’re factoring in hearing loss, for example, when they’re administering these assessments. So at the end of the day, you know, thinking about also, you know, what we can provide for those individuals beyond just a screener? You know, the the hearing loss, we’re gaining our support or evidence for that. As far as peripheral hearing loss, you know, there’s like I mentioned before, there’s a lot of interests thinking about, well, maybe we can use our speech in noise assessments. Our central auditory performance as a way suggested to be a marker of cognitive performance. Some people have suggested it might be an early marker that we could maybe one day add to kind of these neurocognitive test matters, I say, add to in the sense of, you know, combine that with the other information and not to stand alone. So I think there’s a lot of potential there. And I’m excited for that potential. But I think what is primarily missing right now, before we actually actually engage in that is that cross collaboration, you know, because us providing the screen or without the next steps or the right communication, it doesn’t really help our patients and might confuse them or harm, kind of what we’re actually trying to do. And that’s my concern.

Brian Taylor 24:37
Yeah, I share that concern. I think it’s really difficult to know sometimes what to do with the information that you have. Yeah. And I think as a profession, we still haven’t completely, we haven’t standardized that. And I think that’s always a little bit of a problem.

Danielle Powell 24:50
Yeah, yeah. Exactly. If you look at the research that’s out there, there’s there’s you know, there’s neuroscience doing similar research that will our auditory scientists are doing, but they’ve stayed siloed. And I think that’s part of the reason why we’ve been talking about this for decades, but we actually haven’t really gotten a lot further in our progress of what we’re doing about it. And so part of my goal is kind of bridging the gap between these two, to try to move us a little bit further forward and highlighting Well, this is what we know, what do we actually what what’s going to help us move further, faster, so to speak.

Brian Taylor 25:27
The next thing I wanted to ask you about, and we already kind of alluded to it earlier, and that is this relationship between intervening with hearing aids and, you know, possibly slowing down cognitive decline. What is the latest research say? What, what’s your take on on all that research?

Danielle Powell 25:46
Yeah, yeah. So it’s, um, you know, the, the research that we have, so far, we have some small trials that have gone on for a few months, a, you know, a couple dozen, a couple dozen, you know, maybe 100 people or so that are generally overall support the use of hearing aids to either delay, cognitive change, or cognitive, cognitive changes, specifically, most of the research that we have for hearing aids or cochlear implants, really, but especially hearing aids, what I alluded to earlier, is the observational research. So it’s thinking about, you know, does this person already have hearing aids, yes or no? What is their cognitive change over a period of time, what we, that there’s a lot of power, there’s a lot of strength in our observational studies, that tells us what we should focus on further, what we can’t necessarily do is have a lot of control over all of these different factors. When we call confounders, for example, if you’re unfamiliar with that, that can also kind of influence this association, the best way that we can do that is through a clinical trial, where we have direct control over who gets a hearing aid, who doesn’t part of the concern of that is those who are more likely to have hearing aids are usually higher income and better education, all of these other things that can be protected against cognitive change, as well. So a clinical trial gives us a lot better confidence that we’re really just looking at as best that we can through all of these various tools. How does that hearing aid influence changes? One of the longest and largest clinical trials for that, I’m putting in a little plug here, because it’s my my colleagues are part of the reason to do this is the ACHIEVE clinical trial. That’s in a larger group of people looking at cognitive change over three years. And those results should be out within the next year or two. Kind of soon, hopefully, that’s going to be kind of the strongest evidence that we can have, of how does hearing aids influence cognitive change with dementia, a lot of what we have so far, it really is suggesting that and again, and again, and same thing, the limit information you have on cochlear implants, I don’t want to I don’t want to minimize that it’s just a smaller, both research base and population that we’re talking about. And so as far as kind of how that could influence it, like I said before, it really depends on that pathway that we’re talking about, whether it’s a short term change, a long term change, there’s a lot of potential different things that could influence. It could influence social isolation, social isolation, like I said, risk for depression, a lot of different things. And we talked about hearing aids, but there’s also a lot of information about hearing management in general. So there’s some more recent interest in, you know, thinking about hearing devices in general, you know, with the changes in and policy coming up in the future, it’s not going to be specific hearing these, there’s going to be other things that we have to factor into, including just general communication strategies, all of this for things that we need to kind of grow our evidence base, if we want to kind of move things along the

Brian Taylor 28:43
right. I mean, care in general, yeah, simple, like just having a hearing aid in wearing and a couple hours a day, you’re gonna get the same results as if all day worn, you know. So there’s a lot of unknowns. Which brings me to the last question that I want to ask you. And that is, given all your experience as a researcher, as a clinician, what’s one big question that you’d like to try to answer in this area over the next few years with your research?

Danielle Powell 29:09
Yeah, well, my research, I think I’ve already alluded to the biggest questions that we need to answer and one is do hearing aids actually changed cognition like we just talked about? And two, how is this association actually happening? Those are two of the biggest things that are going to help us understand what we can do for, like how we manage and treat our patients. You know, there are other kinds of more nuanced things that I think are important for our understanding and the strength of the evidence that we can present. And all of this evidence matters because it informs our clinical care, and it informs our policymakers, having strong kind of cohesive evidence can help maybe, you know, get hearing aid coverage, get hearing services covered that kind of thing. And right now, we don’t know if hearing aids for sure. Do anything we assume they do based off the evidence we have but we need the strong evidence. We don’t exactly know how it works, we have ideas that could be multiple different ways that it works. But that’s all going to matter as far as what we do with our patients. And then again, wanting to make sure that whatever we’re doing is meeting the patients where they are both, as far as ensuring the testing that we’re doing is valid and accurate still, and that we’re working together to kind of provide that person or family centered care that’s really going to move things forward. Until we kind of do that cross collaboration and talk with other professionals and specialties. There’s still going to be some gaps in what we’re doing. So in my opinion, kind of those are the biggest areas that are needed to move us forward.

Brian Taylor 30:43
Well we look, we look forward to more work in this area for you and your team. And thank you for all the valuable work that you’ve already done and contributed to the field. We appreciate it. Yeah, thank you. clinicians out there. Yeah, all right. Yeah. So Danielle Powell, epidemiologist, audiologist at Johns Hopkins University, in Baltimore, School of Public Health. Thank you for your time. And I want to let the viewers know that a couple of her Open Access articles that we referenced here will be in the in the show notes and you can look for those, click on the link and it’ll take you to the Open Access article. So thanks again, Dr. Powell, we appreciate your time.

Danielle Powell 31:24
Thank you