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Why does covid cause long term loss of smell? Scientists have a theory.

Why does covid cause long term loss of smell? Scientists have a theory.

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The permanent loss of smell has left some Covid-19 survivors longing for the scent of their freshly bathed child or a whiff of their once favorite dish. It leaves others accustomed to the stench of garbage and accidental drinking spoiled milk. “Anosmia,” as experts call it, is one of the strangest symptoms of the long-running covid — and researchers may be one step closer to figuring out what causes it and how to fix it.

A small study published online Wednesday at Scientific Translational Medicine and led by researchers from Duke University, Harvard and the University of California, San Diego, offers a theory and new insight into the long-term loss of smell.

The scientists analyzed samples of olfactory epithelial tissue — where olfactory cells live — from 24 biopsies, nine of which were from post-Covid patients struggling with permanent loss of smell. Although the sample was small, the results show that the sensory deficit is linked to an ongoing immune attack on the cells responsible for smell – which continues even after the virus is gone – and a reduction in the number of olfactory nerve cells.

Bradley Goldstein, an associate professor in Duke’s Department of Head and Neck Surgery and Communication Sciences and Department of Neurobiology, author of the paper, called the results “striking” and said in statement“It almost looks like an autoimmune process in the nose.”

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While there is research that looks at short-term smell loss and uses animal models, the new study is notable because it focuses on permanent smell loss and uses high-tech molecular analysis of human tissue.

The study reflects the enduring interest in the mysterious symptom. In July, researchers estimated that at least 5.6 percent of Covid-19 patients develop chronic olfactory problems. This study, published in the peer-reviewed medical trade publication BMJ, also suggests that women, as well as those who had more severe initial dysfunction, were less likely to regain their sense of smell. The elderly are also particularly vulnerable, The Post claims reported.

Earlier this month, anot a small study of covid-19 patients It has been suggested that long-term olfactory dysfunction may lead to changes in brain regions corresponding to olfaction. Research published in Februaryon which the Duke study is based, found that people who died of covid-19 had fewer membrane-embedded odor-detecting receptors than expected.

Loss of smell can have significant consequences. It’s a threat detection mechanism, from the gas stove you accidentally left on to the stomach-churning smell of a rotten egg. And it is a feeling closely related to memories.

Carol Yan, an otolaryngologist and head and neck surgeon at the University of California, San Diego as well as an author of the new study, has treated patients with permanent loss of smell. “It’s pretty devastating for them. And many times, at that point, it’s been more than two years of loss of smell,” she says. “They wonder, ‘Why me?’ Why do I still have a loss of smell compared to so many of my friends, colleagues, family members who have recovered?’

Doctors are struggling to explain what causes it. “Clinically, when you look at these patients and look into their noses, everything looks pristine,” she says. “So it’s happening at the molecular level.”

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The study offers some hope, Yang says, because while some have suggested that the olfactory deficit is related to the central nervous system, this research offers evidence that at least part of the problem is due to inflammation in the nose, where the virus first attacked. This could mean there is potential for an easier, topical treatment.

For Yang, research on the localized immune response supports others research she has done in platelet-rich plasma as a treatment for loss of smell. “What we found in the clinical trial was actually that PRP was more likely to improve outcomes for Covid 19-related loss of smell compared to placebo,” she says, cautioning that PRP, which has anti-inflammatory properties , is not a “magic bullet” and needs more research – but it looks promising.

And the stakes are high. With smell, Jan says, comes your ability to enjoy food and the environment around you. It even affects how you relate to others. “I’ve had patients actually come to see me and say, ‘I’m a little embarrassed to come see you. I didn’t think it was a big deal. I just lost my sense of smell, but it greatly affected my quality of life.”




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