Michael Hunter, MD on Medika Life

Covid: Why Do Some Lose Smell?

RESEARCHERS ARE CLOSER TO UNDERSTANDING why some people lose their smell sense after contracting Covid-19. Researchers recently identified a genetic risk factor associated with smell loss, taking us much closer to much-needed treatment for those who suffer from the condition.

Approximately six months after experiencing a Covid-19 infection, upwards of 1.6 million people in the USA still have alterations in their smell sensation.

The cells lining the inside of our node are known as the olfactory (nose) epithelium. These cells protect the olfactory nerves that help us to smell.

Covid: Why do some lose smell? Genetics.

Now comes a study published journal Nature Genetics that reports a genetic risk factor linked to smell loss of smell after a Covid infection. We are closer to solving the mystery of why some Covid sufferers experience a loss of smell.

Photo by Ajay Karpur on Unsplash

Why do some individuals who get a Covid-19 infection lose their smell while others retain it? We may have some new clues:

A genetic spot, near two genes for smell, is associated with Covid-induced loss of smell and taste. A change in this gene increases the chances (by 1.1-times) a person infected with Covid-19 will lose their smell.

Fortunately, about 80 percent of those with Covid-19 will regain their sense of smell, some experience long-term loss of the senses of smell and taste.

The genomics and biotechnology company 23andMe researched subjects living in the United States in the United Kingdom. Of the nearly 70,000 individuals who self-reported receiving a positive Covid-19 test, 68 percent experienced a loss of smell or taste.

After looking at the genetic differences between those who lost smell and those who did not, the researchers identified a genetic difference near two genes, UGT2A1 and UGT2A2. Nasal tissue involved with smell expresses these genes.

The researchers demonstrate how access to a massive database can help identify genetic differences. Now, researchers will try to figure out how the two genes are involved in losing smell.

Women appeared slightly more likely to have a loss of smell, while African-Americans and those of East Asian descent were significantly less likely to report loss of smell or taste. Genetic variation in the identified region does not explain the differences.

Covid: Why do some lose smell? Final thoughts

The 23andMe researchers open the door to a better understanding of why some experience long-term Covid-19 symptoms such as a loss of smell. Inherited genetics may play a role.

Smell and taste researcher Danielle Reed offers that previous studies hinted that the loss of these senses is secondary to a failure to protect the sensory cells of the nose and tongue from viral infection.

Instead, the current study points to an alternative explanation — “The pathways that break down the chemicals that cause taste and smell in the first place might be over or underactive, reducing or distorting the ability to taste and smell.”

My take

I have some issues with the study, including that the subjects self-reported having a Covid-19 infection.

separate study showed age under 40 and nasal congestion at the time of viral infection is predictive of a higher chance of smell recovery. Difficulty breathing at the time of infection and prior head trauma decreases the chances for recovery.

Finally, early research suggests loss of smell and taste is less likely with the omicron variant. Thank you for joining me today.

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Michael Hunter, MD
I received an undergraduate degree from Harvard, a medical degree from Yale, and trained in radiation oncology at the University of Pennsylvania. I practice radiation oncology in the Seattle area.

Michael Hunter, MD

I received an undergraduate degree from Harvard, a medical degree from Yale, and trained in radiation oncology at the University of Pennsylvania. I practice radiation oncology in the Seattle area.

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