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Study reveals clues as to why some people are more at risk of losing their sense of smell and taste from COVID-19

2022-01-18T13:30:52.332Z


As many as 1.6 million people in the US remain unable to smell or have experienced changes in their ability to smell six months after contracting the coronavirus.


By Sarah

Sloat

Scientists are figuring out why some people lose their sense of smell after contracting COVID-19.

A study published Monday in the journal Nature Genetics has identified a genetic risk factor associated with loss of smell following coronavirus infection, a discovery that brings experts closer to understanding this puzzling pattern and may point the way to treatments. much needed. 

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Six months after contracting COVID-19, up to 1.6 million people in the United States remain unable to smell or have experienced a change in their ability to smell.

The exact cause of COVID-19-related sensory loss is unknown, but scientists believe it is due to damage from infected cells in a part of the nose called the olfactory epithelium.

These cells protect the olfactory neurons, which help humans smell. 

"How you go from infection to loss of smell is still unclear," said Dr. Justin Turner, an associate professor of otolaryngology at Vanderbilt University who was not involved in the study.

"Early data suggest that the support cells of the olfactory epithelium are the ones that are being infected the most by the virus, and presumably this leads to the death of the neurons themselves," he said.

"But we don't really know why and when that happens, and why it seems to happen preferentially in certain individuals."

he added.

According to the study, a genetic locus close to two olfactory genes is associated with coronavirus-induced loss of smell and taste.

A locus is the fixed position of a gene on a chromosome. 

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This genetic risk factor increases the probability that a person infected with SARS-CoV-2 will experience a loss of smell or taste by 11%.

Although some estimates indicate that 4 in 5 COVID-19 patients regain these senses, research suggests that persistent inability or reduced ability to smell and taste affects relationships, physical health, and psychological well-being. 

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Researchers at the genomics and biotech company 23andMe conducted the study as part of a larger coronavirus project.

All participants lived in the United States or the United Kingdom. 

Within a group of 69,841 individuals who self-reported having received a positive COVID-19 test, 68% reported a loss of smell or taste as a symptom.

Loss of smell and taste were combined as a single survey question.

This pooling and the use of self-reported data are limitations of the study.

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After comparing the genetic differences between those who lost their sense of smell and those who did not suffer from this symptom, the study team found a region of the genome associated with this division that is located near two genes, UGT2A1 and UGT2A2.

Both genes are expressed in the tissue inside the nose related to smell and play a role in the metabolism of odorants. 

A woman gets tested for COVID-19 at a testing center on January 7, 2022 in Houston, Texas. Brandon Bell/Getty Images

“It was this beautiful example of science where, from a large group of participants who have undergone this 23andMe trial, we were able to rapidly gain biological information about this disease that would otherwise be very, very hard to come by,” he said. Adam Auton, vice president of human genetics at 23andMe and the study's lead author. 

It's unclear how UGT2A1 and UGT2A2 are involved in this process, although he and his colleagues hypothesize that the genes "may play a role in the physiology of infected cells" and the resulting impairment that leads to loss of smell. 

To use these findings, scientists need to learn more about how these genes are expressed and what their roles are in olfactory signaling, Turner said.

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Certain trends also emerged among participants who reported loss of smell and taste: Women, for example, were 11% more likely than men to experience this.

On the other hand, adults between 26 and 35 years old constituted 73% of this group. 

The study team also found that people of "East Asian or African American descent were significantly less likely to report loss of smell or taste."

The cause of this observation is not yet known, but Auton said it is probably not explained by genetic variants at this specific locus.

The team also notes that the study is biased toward people of European descent due to limited baseline data. 

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These findings can help patients in two ways, said Danielle Reed, associate director of the Monell Chemical Senses Center.

She studies differences between people in loss of smell and taste due to COVID-19 and was not involved in the new work. 

First, "it helps answer the 'why me' question when it comes to loss of taste and smell after getting COVID-19," he said.

“Some people have it and some don't.

Innate genetics may partly explain why," he said.

The study may also help scientists find treatments.

Previous research suggests that the loss of these senses is related to a "failure to protect sensory cells in the nose and tongue from viral infections," Reed said. 

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"This study suggests a different direction," he said.

"The pathways that break down the chemicals that cause taste and smell in the first place could be overactive or underactive, reducing or distorting the ability to taste and smell." 

For most of the coronavirus pandemic, loss of smell and taste have been known as hallmark symptoms.

Early research suggests that loss of smell and taste is rarer with the omicron variant, but it's not entirely unlikely: in a study of 81 omicron cases in Norway, 12% reported reduced smell and 23% reduced loss of taste. taste.

Source: telemundo

All news articles on 2022-01-18

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