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"The pressure of suffering is enormous"

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Experts estimate that up to 70 percent of COVID-19 patients suffer from smell and taste disorders. We spoke with Kathrin Ohla from the Jülich Research Center about an underestimated symptom.

Kathrin Ohla heads the "Cognitive Neurophysiology" working group at the Institute of Neuroscience and Medicine at Forschungszentrum Jülich. The psychologist is a member of the steering group of the Global Consortium for Chemosensory Research (GCCR).

We have already had a conversation about your studies on olfactory and gustatory disorders in COVID-19 at the beginning of July. Since then, numerous sufferers have commented on this interview, the tenor being, "Finally, I'm finding something about my symptoms!" This has almost resulted in a kind of self-help group. What do you think about the reactions?

They show how enormous the pressure of suffering is. And I am pleased that we have been able to strengthen the backs of so many who now know: "I am not imagining this."

It is often mentioned that some family doctors and ENT specialists fob patients off - especially if they suffer from bad odors - with: "You're imagining it!"

I find this no longer comprehensible. Many colleagues, just like myself, have successfully fought for the National Institute of Health (USA) to include loss of smell and taste as a COVID-19 symptom. The World Health Organization (WHO) did the same quite a while ago. The data situation could not be much clearer: there are the first meta-analyses showing that seven out of ten corona patients - i.e. 70 percent - are at least temporarily affected.

But the 70 percent refers only to infected people who also show other symptoms?

The prevalence - i.e. the frequency of a disease - can only be determined with a random sample. Our online survey, on the other hand, inevitably attracts people who have problems with smelling and tasting. A recent study looked at 34 publications where samples ranged from 15 to 7,178 COVID-19 patients. The averaged prevalence of loss of smell in these studies was 50 percent when patients were interviewed and 77 percent when they were examined with an objective test. This is probably very close to the prevalence. You always have to keep in mind that the really severe cases are not diagnosed for loss of smell. There one has completely different problems than still another smell test to make.

When I read the stories of suffering in the comments under our first interview, I have the impression that this is still the milder variant compared to parosmia. What sufferers report about the worst smells that they suddenly perceive - you'd rather not smell anything.

That sounds harsh, but it's true. Because parosmia means exactly that: things suddenly smell different. Usually, it is not accompanied by pleasant smells. It's actually always reports of foul odors: Feces, sewage, burnt things.

Why did nature set it up that way? Is it a warning mechanism?

Kathrin Ohla heads the "Cognitive Neurophysiology" working group at the Institute of Neuroscience and Medicine at Forschungszentrum Jülich. The psychologist is part of the steering group of the Global Consortium for Chemosensory Research (GCCR). Image: Forschungszentrum Jülich

That is an interesting question. It is the interaction of different odor molecules that makes up the typical smell of bananas, for example. It is often the case that odor molecules can activate different olfactory receptors in our nose. The pattern of activations that results is then interpreted by the brain as, "That's banana smell." Now imagine that in this patterned tapestry of neurons, every third one fails, and the result is no longer "banana." The signal to the brain is suddenly quite different. My hypothesis is therefore that parosmias are simply malfunctions and not warning mechanisms.  

Since our first conversation, do you know more about the time periods when the sense of smell returns to normal?

In our studies, we specifically looked for participants who were acutely ill or had been ill in the last 14 days. So we can only say something about a longer period of time to a limited extent. In the recovered group, smell and taste disturbances were still present in about half of the cases. We fear: Those who are not yet healthy after 30 days are likely to have their impairments last longer. In addition, we asked a sample of our participants again after a few months how their symptoms had developed. We started this a month ago, and we already have a few thousand responses. We hope that this and other parallel studies will provide us with more concrete information.

Are there also COVID-19 patients who were sick in March and still can't smell?

Yes. It is now important to assess whether these are a few extreme exceptions. But if even one percent of millions of people with the disease permanently lose their sense of smell, that's obviously a lot of cases that need to be treated further.

Many report fluctuations: First the sense of smell and taste improved again, then they deteriorated again. Is that typical?

I find it rather surprising. However, I am not a medical doctor who specializes in this area. You also have to consider: If the smell fails, it leads to an enormous stress to observe oneself very closely. To objectify this a little, we have brought out the smell check, where everyone can smell things in their own household and evaluate this impression. We want to use it to give a regular stimulus to measure: How is it really changing? We already have more than 7,000 participants. That's where we're preparing the first analyses.

You mentioned that doctors can confirm with tests, "This person has a loss of smell." But I can tell that myself. Where is the added value?

Not every ENT doctor has these tests available. As a rule, you go to a specialized olfactory and taste clinic, such as the one in Dresden. Patients are presented with different concentrations of scents in a sequence they are not familiar with. This makes it possible to find out how sensitive the patient is. These tests are normalized, which means you have a lot of data about how this age, this gender should perform. And then you look at how much the patient deviates from that.

Can you also test for parosmia?

Yes, for example with an olfactory identification test: The patient is given a clearly smellable scent and has to say what it smells like. If he says something completely different, this is an indication that parosmia is present. It helps some patients to have a doctor tell them, "We have the test result, it behaves exactly as you say."

But what do you do then? Can one rely only on the time factor? On the fact that the cells will renew themselves again?

It is a terrible statement from a medical point of view. But "Be patient!" is a phrase that is used a lot. There is no miracle drug. But there are studies that suggest that smell training might help. Now we need to study whether that also helps with COVID-19-related olfactory disorders. So there's nothing more that can be done at this point except to give hope.

And to continue to do research?

Yes, more clinical trials are needed to look: What does it look like prospectively? The problem is: The clinics that care for the patients and test them must also have the interest to re-enroll them even later and examine them. And we will always lack the values from before the disease. It remains exciting. At least the great importance of smelling and tasting is now finally becoming clearer, which many doctors had dismissed as secondary compared to seeing and hearing.

Global Consortium for Chemosensory Research (GCCR) online survey.

The GCCR survey has been online since April 7, 2020 and in 32 languages. All adults who are currently suffering or have suffered from a respiratory illness such as COVID-19, flu, or cold in the past two weeks are eligible to participate. The questionnaire assesses the sense of smell, the sense of taste and the sense of certain sensations in the mouth. These include burning, cold or tingling sensations, such as when coming into contact with chili, peppermint candy or carbon dioxide. The GCCR experts call this third sense irritation. Participants are asked to indicate on a scale between 0 and 100 how well they rate their perceptions with each sense before and during the disease.

The GCCR's more than 500 members aim to promote global collaboration in research on the chemical senses of smell and taste - in coordination with local laboratories, scientists and clinics.

Link to participate: https://gcchemosensr.org/surveys/

Kathrin Ohla and her team have also developed a smell and taste test for everyone. With this, anyone interested can continuously measure their ability to smell and taste at home:www.riech-check.de

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