13 April 2022

Study Advances Understanding Of COVID-Related Loss Of Taste And Smell (Genetic Risk)

Written by Chloe Garnham

Losing your sense of taste or smell with COVID-19 is a frustrating phenomenon that researchers are working to better understand.  This loss is temporary for some, and more long-term for others (six months or longer).

In 2020, a systematic review¹ of 24 studies about smell and taste dysfunction indicated that 40% of people lose their sense of taste (dysgeusia) or smell (anosmia) during a COVID infection.

A different multicenter study² conducted in 2021 found that the number may be as high as 74%. Additionally, impairment seems to be more common in people with mild COVID-19 than in moderate-to-severe cases.,

Another study³ reports that the ability to smell and taste comes back to most people within a few weeks to a month. The same researchers also report that nearly three-quarters of people will “recover to normal or near-normal within two months.” In September 2021, two members of the Department of Otolaryngology–Head and Neck Surgery at Washington University School of Medicine published a research letter⁴, estimating that 1.6 million people in the US have experienced smell and taste dysfunction because of COVID.

More recently, the personal genetics company 23andMe.com recruited 69,841 study participants from the US and UK to investigate further. In their study titled The UGT2A1/UGT2A2 locus is associated with COVID-19-related loss of smell or taste; researchers compared SARS-CoV-2 test-positive individuals who self-reported ‘loss of smell or taste’ versus test-positive individuals who did not.

The study’s findings are in a Nature Genetics article⁵ published on January 17th, 2022.  The data suggests that a particular location near two specific genes, ‘UGT2A1’ and ‘UGT2A2’ has an influence on why some people infected with COVID will experience loss of smell and taste, while others will not.

The genes in question are in the olfactory epithelium — more commonly known as nasal tissue. Out of nearly 70,000 people, 68% of the COVID-infected survey participants reported a loss of smell or taste as a symptom.

The same study⁵ also revealed additional risks factors:

  • Females were more likely to report loss of taste or smell than males (72% versus 61%)

  • The affected group skewed younger (73% were in their mid-twenties to mid-thirties)

Why this research discovery matters

If you’ve had COVID and your sense of smell or taste has changed, you might wonder why you’re experiencing this dysfunction while others around you are not.

This uncertainty may cause a degree of anxiety or worry. But, now, rather than wonder, “why me?”, there is evidence pointing to a genetic factor.

Additionally, a clear understanding of the root cause(s) for loss of taste and smell from COVID will help scientists and medical professionals better assist with recovery. This includes improving treatment options and the ability to predict recovery time with greater accuracy.

Limitations of the study Some constraints on The UGT2A1/UGT2A2 locus is associated with COVID-19-related loss of smell or taste include:

  • Participants self-reporting the data by an online survey (which may skew data, as participants who suffer symptoms may be more likely to respond)

  • Sample bias toward individuals of European ancestry 

  • A lack of replication (proof that study data can be reproduced)

  • The survey was streamlined into one question, asking about loss of smell and taste together (instead of using separate questions)

How does COVID alter the sense of taste or smell?

On Feb 1st, 2022, researchers from NYU Grossman School of Medicine and Columbia University also announced the discovery of an underlying mechanism to blame for the inability to taste or smell things as usual.

The researchers suggest that COVID infection downregulates the sensitive receptors in your nose. Downregulation refers to reducing or suppressing response to stimuli — the stimuli, in this case, being a smell or taste.

In the related press release⁶, Dr. tenOever stated, “The realization that the sense of smell relies on ‘fragile’ genomic interactions between chromosomes has important implications[...]providing early signals that the COVID-19 virus is damaging brain tissue before other symptoms present, and suggesting new ways to treat it.”

The complete study is published in a Cell.com article⁷.

Health and wellness implications for the loss of taste or smell

Sense of smell and taste pertain to so many aspects of life’s enjoyment — namely eating. But, there are times when losing these two senses (even temporarily) can be more severe or have safety implications.

For example, what if you’re unable to detect that a piece of food is no longer fresh? How about noticing the distinctive smell of a gas leak in your house? These are instances in which you would usually rely on your sense of smell or taste to keep you safe. 

So, suppose you’re experiencing a loss of taste or smell from COVID. In that case, it’s imperative to check the best-by-date on packaged food and make sure you have fresh batteries in household smoke and carbon monoxide detectors. 

One study⁸ found that those who experienced long-term changed sense of taste or smell experienced altered eating, appetite loss, weight changes, a lack of pleasure in eating, and even altered relationships.

Participants also reported feeling a marked lack of support, commenting:

“It’s scary to just not be sure of what is going to happen next with my post-COVID body… it’s a new symptom/feeling every week it seems.”

and

Sometimes this thing occupies my mind so much I just want to tell people about it, to try to compare what I smell/taste with what they do, and just to express how it feels to hate things that I used to love, but they don’t want to hear it.”

How can I get my sense of smell back?

If you’re experiencing a loss of ability to smell or taste, it’s essential to self-isolate and get tested—these symptoms are some of the more common early COVID-19 indicators. The first thing to do is speak to a doctor. They may refer you to an Ear, Nose, and Throat (ENT) specialist for further treatment.

In addition to consulting with a qualified medical professional, here are a few additional tips for hastening your recovery:

Retrain your nose

Your nose can be “taught” to recognize smells again using olfactory training (OT).  A charitable organization dedicated to helping people affected by taste and smell disorders has published OT guidelines and a sample regimen⁹. A 2015 study¹⁰ found that OT therapy has better outcomes when the therapy is prolonged and when the odors are changed.

Act quickly

If your sense of smell or taste has been affected by COVID and lasts longer than a few weeks, it’s ideal to act quickly and begin nose retraining straight away.  Jennifer Reavis Decker, MD at the UC Health Ear, Nose, and Throat Clinic in Colorado, recommends that people start retraining their senses as soon as possible. In a Denver Post article¹¹, Dr. Decker says, “Your best shot at improving your sense of smell is during the first six weeks after losing it.” She also notes, “The best way to avoid losing your sense of smell (to COVID-19) is to get vaccinated.

Engage your memory

Dr. Decker also notes, “The sense of smell is closely linked to memory, especially pleasant memories.” So, think about whether you have a favorite scent you could use in OT therapy. Maybe a particular perfume, flower, or food that usually activates happy memories?

The lowdown

It is frustrating and upsetting to lose your sense of taste and smell, but scientists are making meaningful headway in understanding genetic factors that predispose a person to this dysfunction caused by COVID-19.

Researchers have identified a specific location on a chromosome that is now associated with a genetic risk factor for loss of smell and taste. These findings stand to advance treatment options and allow doctors to estimate recovery time more accurately.

If you’ve lost your sense of smell or taste, it’s vital to attend to both your physical and emotional recovery, which starts with speaking to a qualified healthcare professional. Recovery is usually relatively quick (within a few weeks), but for some, it takes longer.

Using olfactory training (OT) to retrain your senses can be an effective, low-cost at-home measure. Additional ways to support your recovery include finding a qualified counselor, psychologist, dietician, or nutritionist to help you navigate related concerns like anxiety, depression, and undereating.

When it comes to preventing loss of taste or smell from COVID, to begin with, getting vaccinated is the best measure to take.

The information provided is designed to support, not replace, the relationship that exists between a patient/site visitor and their existing health care professional(s).

Other sources:
  1. Smell and taste dysfunction in patients with COVID-19: A systematic review and meta-analysis (2020)

  2. Prevalence and 6-month recovery of olfactory dysfunction: A multicentre study of 1363 COVID-19 patients (2021)

  3. Subjective smell and taste changes during the COVID-19 pandemic: Short term recovery (2020)

  4. Growing public health concern of COVID-19 chronic olfactory dysfunction (2021)

  5. The UGT2A1/UGT2A2 locus is associated with COVID-19-related loss of smell or taste (2022)

  6. Mechanism revealed behind loss of smell with COVID-19 | NYU Langone Health

  7. Non-cell-autonomous disruption of nuclear architecture as a potential cause of COVID-19-induced anosmia (2022)

  8. Altered smell and taste: Anosmia, parosmia and the impact of long Covid-19 (2021)

  9. Using what you have at home | Fifth Sense

  10. Modified olfactory training in patients with postinfectious olfactory loss (2015)

  11. Recipes for loss of smell, taste after COVID-19 | The Denver Post

General source:

Chloe Garnham is a writer exploring a broad range of topics, including healthcare, education, and technology.

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