Long Covid: What we know about loss of smell and taste

CNN
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One morning after recovering from Covid-19, you wake up to coffee that smells like unwashed socks, eggs that smell of feces, and orange juice that tastes metallic. is good. It’s a sign that your sense of smell is working, even if it’s miswired in your brain.

The sense of smell may be completely lost, which is called anosmia. Without warning, you will no longer be able to inhale the sweet smell of your baby’s skin, your partner’s gift of roses, or the pungent smell of your workout clothes.

Because taste and smell are intertwined, food may be bland or tasteless. Malnutrition, cognitive decline When depression.

Danger also lurks. Without the smell, you might not notice the signs of a fire, natural gas leak, toxic chemicals, or spoiled food or drink.

This is the reality that about 5% of Covid-19 survivors worldwide currently have long-lasting taste and smell problems. According to a 2022 studyMore than two years after the pandemic, researchers find an estimated 15 million people may still have problems with smell perception, and 12 million may have problems with taste. Did.

support and advocacy groups such as absence When five senses mobilized, supported and offered positive and hope, Olfactory training tips and even recipe to increase appetite.

Dr. Zara Patel, a rhinologist and professor of otolaryngology, head and neck surgery at Stanford University School of Medicine, says that smell and olfactory training encourage people to sniff essential oils twice a day.

“The way I explain to my patients is that if you have a stroke and you can’t move your arm, go to physical therapy and do rehab,” Patel said. is.”

Dr. Justin Turner, a rhinologist and associate professor of otolaryngology, head and neck surgery at Vanderbilt University, said that as science learns more about how Covid-19 attacks and disrupts the sense of smell, it will become “more accurate.” I think we will see interventions that target the Nashville Medical Center.

For those still struggling with the loss of their sense of smell and taste, “you have to think positively and assume your sense of smell will come back,” Turner said. We don’t want them to ignore it, we want them to take it seriously.”

People have lost their sense of smell and taste for centuries.Common cold and flu viruses, nasal polyps, thyroid disease, severe allergies, sinus infections, neurological disorders, etc. Alzheimer’s, Parkinson’s, and multiple sclerosis can all impair your sense of smell and taste.

So are head trauma, exposure to harmful chemicals, cancer treatments, smoking, gum disease, antibiotics, various blood pressure, cholesterol, reflux, allergy medications, and more. According to the Cleveland Clinic.

Aging is a major cause of olfactory loss due to the reduced ability of olfactory sensory neurons to regenerate.a A study conducted in 1984 More than 50% of people between the ages of 65 and 80 were found to suffer from ‘severe olfactory impairment’.That number he exceeded 75% For those over 80 years old.

When the virus that causes Covid-19 entered our lives, the condition, which was relatively rare among people under the age of 50, expanded exponentially, affecting all age groups. rice field.

“Covid-19 has affected adolescents far more than other forms of post-viral smell loss,” he said. Surgeon Dr. Eric Holbrook is Associate Professor of Otolaryngology and Head and Neck Surgery at Harvard Medical School. “For example, loss of sense of smell is not common in the pediatric population, but is now very common.”

In fact, smell loss was so prevalent early in the pandemic that it was considered the canary in the coal mine. This was thought to be an early sign of Covid-19 infection, even in the absence of other symptoms.

Not today.a study A study published in May found that 17% of people infected with the Omicron variant lose their sense of smell. The dominant variant of the virus that causes Covid-19 in late 2021. (may change again when the virus mutates. )

In contrast, people who were fed up with the two original variants, alpha and beta, were 50% more likely to lose their sense of smell and taste. Delta got about as bad – 44% of people were affected, According to research.

Statistics show most people recover their sense of taste and smell.Ann Analysis of August Of the 267 people who lost their sense of smell and taste at least two years ago, the majority fully (38.2%) or partially (54.3%) regained their ability to smell and taste. Applied to people under

but 7.5% Two years after being cured of the Covid-19 infection, my sense of smell and taste had not returned. Those least likely to recover included those with pre-existing nasal congestion, more women than men, and those with greater initial severity of smell loss.

How does Covid-19 damage the olfactory system? Initially, scientists believed it infected neurons in the nose responsible for transmitting odors from the environment to the brain. These neurons are located in the olfactory bulb at the top of each nostril and send out axons or cables to specific sensory spots in the brain.

Research soon discovered that the virus never entered those neurons.instead it attacks supporting cells, Also known as supporting cells that provide nutrition and protection to nerve cells from birth. Unlike many other cells, neurons in her nose are reborn every two to three months.

“(Covid-19) infection of these supporting cells could have some long-term effects on the ability of those neurons to regenerate over time,” Turner said.

“This is one of the reasons why we sometimes see a delayed effect: there is a reversible loss of smell, and then a second episode of loss of smell, paresthesia, or other symptoms due to dysfunctional regenerative capacity.” There can be waves,” he said.

Parosmia is the medical term for a distorted odor that can often be quite unpleasant.

“Unfortunately, there are classic categories of smells and tastes that are really bad,” she said. Oh, and rotten meat is another common category.

For many people, dysosmia tends to occur or recur at the three-month mark, when olfactory neurons naturally regenerate, experts told CNN.

“Once the reconnection goes off-target and reaches a different location in the brain reserved for another smell, the perception of the smell is completely screwed up,” says Holbrook.

“We have to rely on the ability of these axons to contract and find their way to the right place,” he added. , the new neuron will come back and find the right place.”

Science continues to discover ways viruses attack.a study from February damages olfactory receptors Located on the surface of nerve cells in the nose. These receptors bind odors and trigger nerve impulses that transmit information to the brain.

There may also be a genetic component.a study in january We discovered that two overlapping genes, UGT2A1 and UGT2A2, have mutations and are involved in odor metabolism. People with the mutation may be prone to losing their sense of smell, but more research is needed to determine the virus’ impact. Association In genes – if any.

People who are older and have chronic conditions that affect the nervous system, such as diabetes, are often more susceptible to smell disorders, Patel said.

“Diabetes affects the very small blood vessels in the body, including the nose, and disrupts the flow of blood, nutrients and oxygen to these olfactory nerves,” she said. Anything that makes it difficult for our system to recover, such as people with sinuses or allergic inflammation, can be at increased risk as well.”