Researchers Found a Potential Risk Factor for Loss of Taste and Smell from COVID-19

·4 min read
Genetic risk factor for loss of taste smell
Genetic risk factor for loss of taste smell

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Among the many symptoms commonly associated with COVID-19 exists a peculiar one: the loss of smell and/or taste, which sometimes lingers for weeks to months after recovery. It's impacted as many as 1.6 million Americans for longer than six months after they have contracted the virus, according to a November 2021 report issued by JAMA Otolaryngology. A new study has further shed light on the topic, which has proven to be one of the virus' telltale — and most talked about — symptoms.

The new study, conducted by researchers at 23andMe and published in the journal Nature Genetics, linked a genetic risk factor to the loss of smell and/or taste after a COVID-19 infection. To this point, scientists haven't been able to understand exactly why so many COVID patients have reported anosmia or ageusia, aka loss of smell or taste, respectively. The new study zeroed in on a potential genetic link between those who have experienced the puzzling symptoms.

Experimental studies have suggested that the virus causes damage to cells of the olfactory epithelium, which is the part of the nose responsible for the ability to smell. These cells protect olfactory neurons, i.e. the information messengers in the naval cavity that are activated when airborne molecules bind to their receptors. While this new study doesn't confirm why some people experience changes to their ability to smell and taste for so long after recovery, it does pinpoint a genetic locus — aka a specific physical location of a gene or other DNA sequence on a chromosome, like a "genetic street address" — near the olfactory genes that increases the likelihood a person will lose their sense of smell when infected with COVID-19 by as much as 11 percent. (Related: TikTok Users Are Flicking Each Other In the Head to Regain Taste and Smell After COVID-19 — But Does It Work?)

It seems those who have these loci are more susceptible to losing their sense of smell and/or taste as a result of the virus — though it's still unclear why it happens, if there's any way to prevent it from happening should you catch COVID-19, or if there's any way to help bring the senses back should you find you've lost them after infection. (Related: TikTok Swears This Remedy Helps You Regain Taste and Smell After COVID-19 — But Is It Legit?)

The study included 69,841 individuals from the US and the UK who self-reported that they'd received a positive COVID test. Sixty-eight percent of the participants reported that they'd also experienced a loss of smell or taste. Researchers compared the genetic differences between those who lost their sense of smell and those who reported that they hadn't, noting a significant number of participants who'd lost their senses had two specific genes. They were UGT2A1 and UGT2A2, genes within tissue inside the nose that are involved in the ability to smell and metabolize odorants (substances that give off an odor). How these specific genes are involved is still unclear, according to the researchers, but the lead author of the study and 23andMe's vice president of human genetics Adam Auton told NBC News that the presence of those specific genes "may play a role in the physiology of infected cells" and why they lead to the loss of smell. Though the study didn't differentiate between loss of smell and loss of taste, the two are frequently intertwined because the olfactory neurons in the nose are responsible for both. (Related: What Is COVID Tongue, and Is It a Sign You've Been Infected With the Virus?)

The study had some limitations — for one thing participants outside the US and UK were not included. But one thing that's already been established is that the symptom can not only impact general well-being (e.g., the ability to smell a fresh bouquet of flowers or taste freshly baked cookies) but safety as well (think: the ability to detect toxic, polluted, or smoke-filled air, or rancid food).

As for what patients can glean from this study, Danielle Reed, associate director of the Monell Chemical Senses Center, told NBC News, "it helps answer the question of 'why me' when it comes to taste and smell loss with COVID-19. Some people have it and some do not. Inborn genetics [from birth] may partially explain why." The findings might also help health experts develop future treatments so that those who do experience these losses can get them back sooner rather than later.

The information in this story is accurate as of press time. As updates about coronavirus COVID-19 continue to evolve, it's possible that some information and recommendations in this story have changed since initial publication. We encourage you to check in regularly with resources such as the CDC, the WHO, and your local public health department for the most up-to-date data and recommendations.