Smell disorders and COVID-19

How many people have had their sense of smell affected in the long-term by COVID-19? What does it mean for them? Did some COVID-19 waves have a greater effect on sense of smell than others? How can people regain their sense of smell? Prof. Carl Philpott joins Gavin and Jessamy to discuss anosmia and parosmia.

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Transcript

This transcript was automatically generated using speech recognition technology and may differ from the original audio. In citing or otherwise referring to the contents of this podcast, please ensure that you are quoting the recorded audio rather than this transcript.

Gavin: Hello, welcome to another episode of The Lancet Voice. I'm Gavin Cleaver, it's June 2022 and I'm here with my co host Jessamy Bagunel. Cast your mind back, if you want to of course, to March 2020. As COVID 19 circled the globe, it quickly became clear that one of the more prominent harbingers of a COVID 19 infection was a sudden loss or change of a person's ability to smell.

Anyway, who better to talk to for this than Professor Karl Philpott, who's an ENT surgeon at the University of East Anglia, and he specialises in smell and taste disorders. Professor Philpott established the UK's first smell and taste clinic, and he is research lead for the British Rhinological Society.

Carl sat down to speak with me about the burden of smell disorders as a result of COVID 19.

Carl, it's a pleasure to have you on the podcast today. And we're here to talk about the kind of burden of a change of sense of smell following COVID 19. How serious is this? How many people are left with long term ramifications in their sense of smell after getting COVID?

Carl: Going by the number of infections in the UK and by the number of people we think are left with persistent changes and that has varied with the different variants over the course of the pandemic, but the estimates are that about a million people in the UK are now affected by long term smell disorders.

And up to half of those are affected by smell distortion that we call parosmia. So things smelling usually unpleasant when they should smell otherwise. 

Gavin: Yeah, so you mentioned parosmia there. What are some of the different smell disorders that people have been experiencing following COVID? 

Carl: Typically at the onset of the infection, they've been experiencing sudden onset of anosmia, so that's complete loss of smell.

People obviously report loss of taste as well. One of the difficulties with how we use the word taste colloquially is that we tend to use that to refer to flavor perception. And when we're eating, when we breathe out the smell of food. through our nose. We actually smell the food and a large portion of that accounts for flavor.

And then we've got the basic taste of salt, sweet, sour, bitter, and umami, which we get from the tongue. Most people's true taste isn't affected. There is some evidence, however, that true taste may have been affected by COVID. The difficulty always is with being certain about that is you need to go for more testing.

And of course, we don't want to get close to people with COVID 19 because of obvious reasons of a transmission of infection. So the evidence for that is obviously a bit weaker but if you, ask detailed questions and try and pick that out a bit. There is suggestion that there were some issues with true taste performance that may have been short lived, but the smell issues appear to be the more pertinent ones.

The issue of parosmia, the smell distortion is often a delayed feature of those being affected by the condition the longer term. And the reasons for that may be varied, but a part of it may be because as a sense of smell starts to recover then they go through this sort of process where they're getting partial smell function and in conjunction with that smell distortion, and we can talk about the nuances of that, but, for some people, obviously the porosimia may come in at the beginning, but but it is quite variable and we know from previous viruses in the past that porosimia as a symptom is most commonly found in viral smell disorders compared to other types of smell loss. 

Gavin: So in terms of research of smell disorders as a result of COVID, I think, like everything to do with COVID, it's still at quite an early stage.

Carl: Yes, there's lots of activity going on. And in fact we're about to commence a trial here at the University of East Anglia, looking at vitamin A drops as a potential treatment for smell loss. And as part of that trial, we're going to be doing a sub study looking at people.

In the trial who have got paralysmia and looking at their sort of brain functionality compared to those that haven't got it. So we'll get a better understanding of perhaps some more of the nuances of this smell distortion because the global study that I've been part of through the global consortium of chemosensory research.

Our collective data internationally as shown that parosmia is tied in quite well with brain fog as a sort of long term symptom of non COVID. The information we get from our trial work and we're doing sort of brain imaging and functional brain imaging will be really see if we get a better understanding of that.

Gavin: That's interesting. So do you think it's like a similar mechanism maybe? 

Carl: Yeah, possibly. It's interesting because the the biobank data that was published recently from the Oxford group where they had a group of people who had an MRI scan before COVID and then they re scanned them after COVID showed a huge kind of a significant group of people that were affected by changes in the smell parts of their brain.

We, it's clear that the cave is having an impact on those sort of areas of the brain. Obviously, one of the things is with parosomies, we don't fully understand the mechanism of how it works at the moment. There's kind of two main theories. One is that because not all the smell receptors are working properly and we smell things as mixtures, if we're missing pieces of the jigsaw, therefore we don't smell things properly and therefore you get a distortion of the smell.

The other theory is that as the olfactory receptors regrow at the top of the nose, they connect or they rewire incorrectly to the area above it called the olfactory bulb. Because there's a sort of mapping process of all those receptors into specific connections within the bulb, if that rewiring was to go wrong then you again you get a distorted signal.

One of the ways we're looking at it is the results in our trial is to look at structural connectivity in the brain and we've got some sort of clever techniques and some of my colleagues will be looking at that specifically. We'll get a better understanding, hopefully, of whether there's something different in the people with parosma compared to those without.

Gavin: So a bit of crossover between you and the kind of neurology side of things. 

Carl: Yeah, exactly. That's right. Yeah. 

Gavin: Before COVID, how widespread were parosmia and anosmia? 

Carl: Based on studies from other countries our estimates have been that about 5 percent of the population were affected by anosmia, so complete loss of smell.

And then up to 20 percent of people affected by some sort of smell disorder, which includes parosmia, hyposmia, so reduced sense of smell. or phantosomia, which is where you get hallucinations of smell without a smell stimulus. And if you go above the age of 65, increasing rates of smell loss in, certainly over 20 percent and perhaps over 50 percent in those over the age of 80.

There obviously is a natural decline in smell with age. And then you've got, of course, you've got the increase of things like Alzheimer's and Parkinson's in older age, which can significantly affect smell performance as well. 

Gavin: Is there a different sort of age profile then for people with there 

Carl: is.

Yes. It was one of the key things we've seen is that is the younger demographic that's been affected now, whether that's the way COVID's worked or whether it's just because certainly if in the UK, what we've done is we've Told the old and infirm to stay at home out, out of harm's way and to be barricaded in indoors.

We've then vaccinated the elderly first and we've then gone down the age range. So whether we've forced the problem into the younger generations I'm not sure. But certainly over the last six or 12 months I've been frequently seeing children come to my clinic with SMO and Smia.

Which, I can tell you over the last decade and fingers of one hand, the number of children I've seen for viral smell loss. I, it's just rare as hen's teeth in children previously, and now it's become a common feature. And through the charity I work with Fifth Sense, we've also seen an increasing number of, contacts and referrals in for people with who are having children experiencing these symptoms.

Gavin: So that's quite practice changing for you. 

Carl: Yeah, it is. Yeah. Yeah. And obviously, just bring implications in because when you see children practice, you have different considerations with testing and also with the setup you have in clinic to see them as well. 

Gavin: I wanted to talk about the kind of, we touched on it there by talking about children having it, the kind of impact that perosmir and anosmia have on people's lives, it feels like it would be quite a disorienting thing.

Carl: Yes. I think the smell distortion is particularly repugnant for people when it comes to food time, so they really feel disabled about the process of eating, enjoyment of food. And some really struggle to to find a way around that, and about a third of people affected with paralysmia will lose weight.

But if you look at smell loss more generally we, we realize that in terms of, managing food, about a third of the people lose weight because they can't smell and they have no appetite. About a third of the people gain weight because they just go out and try and eat anything as possible to try and seek some sort of stimulus and they keep eating stuff hoping that something will work.

And about the other third somehow manage to plow and even furrow through it. But beyond food, there's lots of impacts that we see in, in, in the studies we've done talking to patients about their experiences. So. Relationships is a key one. So people find a sort of disconnect with their partners because, there's a sort of attraction through smell to our partners.

And actually we're we're wired up to be attracted to people with an opposite genetic profile to us, which is obviously designed to improve the gene pool. There's the sort of connection between parents and children. I hear a lot of female patients talking about, the lack of being able to smell their children, and particularly babies, or and also in grandparents.

Grandparents, missing out on the feeling of the smell of the newborn, grandchildren. That, that's a key one. A lot of people's concern about this sort of, their general well being and their, their own personal hygiene. So they feel very self conscious in their, work environment and social environments.

And they feel disadvantaged in, social settings when there's discussions around food that they can't, that they can be part of anymore. So even if it's not just about eating the food, it's about talking about it in the first place. And memories is another one because our sense of smell is directly connected to the limbic system in the brain, which is where we lay down memories, and that doesn't go through the midbrain, so there's a sort of fast track in and also a fast track out people lose that ability to lay down memory around smell and although they can sometimes recall memories that give them a sensation of smell that obviously starts to fade over time.

Yeah, there's lots of ways in which and I guess the other key thing is that depression and anxiety are very common in people with small disorders. Probably about two thirds of people with small disorders experience depression or anxiety. If you compare that to the general population, that's about 10 percent of the general population.

It's a, it's a massive shift to how people are impacted by this. 

Gavin: Yeah, a lot of stuff that we take for granted. When we're talking about porosmirin and osmirin, are we thinking of quite a strong gradient? I'd imagine it goes all the way from like slight distortion, all the way through to complete lack of a sense of smell.

Carl: Yeah, absolutely. So there's a huge range in there. And that you test people, some people you come in and say, oh, my sense of smell is terrible. And you test them and go actually, you're on the borderline of being normal, but it's just relative to where they were that they feel they've come down.

I guess people who use a sense of smell professionally will particularly feel any kind of reduction as a sort of, a major impact to them. Obviously some people, they're just, they're nothing at all. You can stick stuff under their nose and there's just no reaction whatsoever. So yeah, we see a huge range and it also depends on the cause because there are.

Some causes where things fluctuate, so sinus disease is one of the most common reasons I see people smell loss. The amount of sweating in their nose can fluctuate day to day, so they may get some days where they're really bad and other days where they're actually getting a little bit of something.

Compared to someone who's had a head injury and their brains scarred over completely in the smell area. And they're just it's just gone completely, so they just, they're getting nothing at all. 

Gavin: Is there a kind of general profile that you've noticed in terms of smell returning after a COVID infection?

Carl: I guess the general profile is that people will get the initial insult, they'll notice it go very quickly and in a lot of cases, I know one of my anaesthetic colleagues that I work with saying that, he got up, had a coffee in the morning and then two hours later, he suddenly thought, I can't say anything anymore.

And it was just gone that very instantly. But then he, he experienced within about 10 days, suddenly it came back almost as quickly. as it disappears. It was like a sort of switch turning off, turning on again. But I guess for those who are getting persistent problems, it's they feel that the thing goes and they feel that something comes back a little bit and then they go for a period where they just seem to coast along thinking maybe it's okay and then suddenly the parosmia kicks in and suddenly they're like, wow, what's this going on?

Suddenly everything smells terrible. My plate of food smells like garbage and they suddenly start to feel very alarmed about their symptoms. And that, that timescale is, usually between sort of a month and three months for after the original infection.

Based on the sort of experiences that I've seen people describe. 

Gavin: Did you notice any differences in the different waves, like the different variants? I know anecdotally More friends of mine tended to lose their sense of smell in the original COVID wave. 

Carl: Yeah the sort of early on in the pandemic in 2020, we were seeing that it was about 60 to 70 percent of people getting infected were losing the sense of smell.

So it was a really common feature. And, it was strange that, of course, it took the government about two, three months to formally recognize that despite the amount of lobbying that we were talking about hey, look, this is a key symptom of the pandemic.

But now I think with the Omicron variants we've seen at the moment, it's around about 10, 15 percent and that. That data kind of pool comes from the Office of National Statistics where they're collecting ongoing data about the pandemic and we can see much lower rates of smell loss.

And I'm seeing much less new referrals coming through now clinically for smell loss in relation to the new variants. 

Gavin: That's a huge drop off, isn't it? 

Carl: It is yeah. I guess that kind of reflects the sort of the sort of, the way that the the variants have changed their, the severity of the illness they produce and and their sort of transmissibility.

Obviously we've seen increasing transmissibility, but we're now seeing, were, I think we're all thinking less about COVID in terms of going about our daily lives than we were a year ago. 

Gavin: You were author on a paper looking at recommendations for management of the condition of patients with new onset smell disorders.

What were some of the conclusions from for, for best management techniques? 

Carl: So the key conclusion in terms of first steps are, if people have problems that they should go and be assessed by a specialist ideally with smell and if necessary, taste testing and examination of the nose.

And then if, if the sort of dis, disorder is confirmed the first port of call really is smell training, which is a rehabilitation technique that's been well established over the last decade. And obviously that's a simple kind of conservative technique that people can do without any huge costs or worry about side effects.

They can do it at home themselves. The recommendations around that are that it should be done for up to a year, after the after commencing it because the benefits of it can take some time to manifest. Beyond that, if people are not getting results from smell training obviously, vitamin A we've, I've mentioned that we're doing this trial at UEA to look into that in more detail.

There is some early data that suggests that might be beneficial. One of the key recommendations we made was that we don't believe steroids have a direct role to play in this condition unless there is another condition in the nose, such as sinus disease, allergic rhinitis, where steroids have a role to play in managing that and may help.

Such things as rehabilitation through smell training. But we don't think it necessarily influences the disorder itself per se. Perhaps if you were to give steroids at the very onset of infection, when people are getting acutely infected, that actually might help, reduce the impact of infection.

But of course, if you gave it to everybody who got COVID 19, you'd be massively over treating all the people that don't need it because they get better anyway. So that's a major difficulty with steroids. Other things that we talked about in the consensus paper where other treatments that have yet to go through rigorous clinical trials but from early studies have shown potential benefit.

Those include things like intranasal theophylline and sodium citrate nasal spray, which some early data suggests may have some benefit. 

Gavin: So has that treatment profile changed since COVID 19? Were some of the things that aren't recommended for for regaining smell following COVID were they previously quite highly recommended?

Carl: I think one of the major problems we have in this area was that there was a real sort of lack of good quality randomized controlled trials for smell and taste disorders. In the background, I've been doing some work with the clinical olfactory working group, establishing a core outcome set to, to make sure that future trials are done with much more rigor and so with similar standards so that results are comparable.

But it's all about funding really, and we need to get more funding to get these sort of treatments, which, some of us as specialists in the field have been, using and trying, but we need to get harder evidence about them working, but also to get to, to develop new treatments and that comes through better understanding what's going on with with the small disorders themselves.

Again, the background work we're doing to understand what's happening in people's brains and smell pathways will help further those those goals. The other bit of work we've done through Fifth Sense as the charity is to develop a set of research priorities working in conjunction with the James Lend Alliance, which is a priority setting partnership with doctors and patients and any other stakeholders involved in the condition to develop research priorities, which then we hope funding bodies will take forward and develop new research avenues.

Gavin: How accessible is olfactory training generally for people? 

Carl: It's very accessible, really. So we've got a section on the the 5th Sense website where you can go in and have a look and there are things in your kitchen cupboard which you can pull out and do at home. There are kits you can buy and you can pay, spend money on, but you don't really need to spend any money at all if you've got things, unless you've got bare cupboards at home.

Gavin: Yeah, and it's not really something that requires medical supervision. 

Carl: No, exactly. Exactly. If you follow the instructions on our charity's website, yeah, you could, you can do this for yourself. You're not going to cause any harm by doing it exactly. It doesn't require to put anything in your nose.

It's just smelling things and instead of working with that on a daily basis. 

Gavin: Do you think there's much greater awareness of smell conditions now following COVID? 

Carl: Oh, definitely. Yeah. I think it's certainly raised the spotlight on it and if there's ever been a sort of a silver lining to a cloud, then I think one of the benefits for those of us working in the field from COVID 19 is to see that the profile being raised I just hope now we can convert that into, ongoing momentum to, to develop research in this area, particularly for treatments for smell loss, because, I've been working in this field for the best part of two decades now, and it's been a really frustrating sort of time prior to COVID because people are just going to go smell loss.

Okay why is that important? There's bigger fish to fry. Hopefully now we can have, enough people to have experienced smell loss through COVID 19 that actually, more people understand that actually until you get smell loss, it's an experience. It's it's pretty unpleasant stuff.

And actually, being without a sense of smell or having a distorted sense of smell is another thing you want to be able to live with. 

Gavin: Yeah, so you'd say that, it is proven how impactful this, these conditions are on people's lives. 

Carl: Yeah, exactly. I've, we, when we publish studies before interviewing patients, talking to patients prior to the pandemic and there's been lots of stuff that's been published since the pandemic that, you know, and our charity website has lots of anecdotes about, people's own experiences.

We know these are things that are having significant impacts on people's day to day lives and hopefully we can do more to change that in the future. 

Gavin: Yeah, and that statistic about depression is really striking, I think. 

Carl: Yeah absolutely. It's a, it's a sort of hidden, problem, really, which people are often just, Tuck away and they suffer in silence.

And it is interesting when I first got into this field and we did a sort of public event for the first time in Norwich in 2012. And people came to the event thinking that they were the only person in the world that suffered smell loss. And it was to see their faces and to see their eyes.

Light up to think actually there was a community of people out there that also experienced this. Certainly COVID has accentuated that because of social media now being so accessible and people talking to each other about these problems. But yeah, people used to think that, they were just on their own with this sort of rare condition and it's not rare at all.

The data is out there even before COVID it wasn't a rare problem, but now it's definitely not a rare problem anymore. And it's very widespread. 

Gavin: It's been really interesting chatting with you, Carl, and thanks so much for speaking with me today on the Lancet podcast. 

Carl: No problem at all.

Thanks for having me.

Gavin: Smell disorders, which is a kind of wider bracket, isn't it? Anosmia, which is smell loss. Parosmia, which is a change in smell. Phantomosmia, or something along those lines, which is smelling things that aren't there anymore. And then hyposmia, which is a reduced sense of smell. So I'm really, I'm impressed I've remembered all of those.

Jessamy: I'm extremely impressed that you've remembered all of those. And I think that's what I liked about your conversation was. You know how something which you think is probably quite benign actually when you unpack it the multiple layers in which it impacts patients and people in general and you know the rest of Their lives all of the other consequences on mental health and food and confidence Everything else it's a huge burden.

Gavin: Yeah, and I find it really fascinating I think I guess you know not knowing a huge amount about infectious disease I'd never really imagined that a change in smell was on the table for diseases like this, and I think when it first went through London in March 2020, a couple of close friends completely lost their sense of smell.

In fact, one of them, it took him six months to get it back, and he had to retrain himself on various on various things. Actually, we talked about that in the podcast of the of the retraining the sense of smell. And it really fascinated me because It sounded so debilitating, he completely lost his appetite.

He didn't want to eat anymore. And for me, eating is one of the great joys of life. So I can't, I was really going to myself early on in COVID, I might get COVID, but I really hope it doesn't affect my sense of smell. 

Jessamy: Yeah. I thought there's just some of the statistics that he reeled out were incredible in terms of two thirds of people within Osmia then, going on to have some form of depression or.

anxiety. And, when you unpack it in the way that he did and discuss it and all of the different consequences, it makes complete sense, but it's not something that initially you really think about. 

Gavin: What I was going to say, actually, is that one of the things that really interested me during the pandemic and I think showed how widespread change in sense of smell was the Yankee Candle Index.

Did you see that? 

Jessamy: No, I didn't. But I love a Yankee Candle. So tell me. 

Gavin: There were a couple of papers released about it, but it was largely observational. So not entirely, scientifically reliable, but essentially. There was a very strong relationship between one star online reviews of Yankee Candles and coming waves of COVID 19.

So people would log on and review the candle and say, Oh, I couldn't smell anything. This candle's broken. You sent me a candle that doesn't smell. And, while that may well have been the case, maybe Yankee Candle did send out a bunch of candles that didn't smell of anything. The waves of those reviews completely correlated with oncoming waves of COVID 19.

They were actually quite a good predictor before the waves hit of how severe they were going to be. 

Jessamy: It sounds like a, maybe a Christmas content type paper. I liked it. 

Gavin: Oh yes, given Yankee Candles are so often Christmas gifts. It reminds me of one of my other favourite Strange Spurious Indexes, which is the Waffle House Index, which I assume, again, you haven't heard of because it's bizarre.

The Waffle House Index is a kind of index that shows how hard areas have been hit by a natural disaster in the US. So Waffle House is a chain of restaurants that are made to be open 24 7. And they're made to run on extremely low power, so they're very durable. And, you can tell, according, and this is a FEMA index, how badly an area's been hit by how many Waffle Houses have been forced to close by the natural disaster.

Because they're so resilient. So I'm really behind these kind of unexpected indexes. 

Jessamy: I can see, Gavin. I feel like there's some kind of like general quiz, pub quiz, knowledge game that could be played, like spun out from this conversation. 

Gavin: I think so. That's something I should definitely look into.

Jessamy: I think that would be worthwhile. 

Gavin: It's just fascinating, isn't it? To think of, this is one very small aspect. of the kind of burden of, and we talked about long COVID a few weeks ago the burden of disease that is now left by COVID 19. And it's huge burden. It's affected everyone around the world.

And there's so many people left with disease, with issues that they didn't have beforehand that are now chronic. 

Jessamy: Yes, I think that's right and I suppose we're in this time now and we've reflected on it previously where we've got multiple crises going on and we're in many areas moving into a place where COVID 19 is not so acute and not such a problem and the issues and the burden that it has left behind, economically, socially, clinically are Bye.

People's attention has been drawn elsewhere and actually there's a real need to analyze and understand what the burden is in each of these different sections so that we can really situate ourselves again and understand the landscape and the sort of environment that we're in right now. And I don't feel that we, that anybody really has the time or the space to, because we're dealing with so many other crises at the same time and the sort of new cycle is so fast.

Yes, 

Gavin: it's the sort of kind of unsexy public health side of things, isn't it? That's so vital. 

Jessamy: Yeah. And I think, the push to keep pandemic preparedness at the forefront, that's obviously crucial. But, just outside of that, also just understanding where we are in terms of the impact on health systems, waiting lists, mental health burden, lost follow up, lost.

Cancer appointments, the list goes on. W we need some very careful kind of cataloging about that kind of thing of which, smell disorders and the sort of impact that's had on people's lives, obviously part of it.

Gavin: That's it for this episode of The Lancet Voice. If you want to carry on the conversation, you can find Jessee and I on Twitter on our handles at Gavin Cleaver and at Jessee Baggin. You can subscribe to the Lance voice if you're not already. wherever you usually get your podcasts. And if you're a specialist in a particular field, why not check out our In Conversation With series of podcasts, tied to each of the Lancet specialty journals, where we look in depth at one new article per month.

Thanks so much for listening, and we'll see you again next time.