More than a million people in the US may not have regained the sense of smell for months after Covid-19 infection, study estimates – Community News
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More than a million people in the US may not have regained the sense of smell for months after Covid-19 infection, study estimates

The research published in JAMA Otolaryngology-Head & Neck Surgery estimates that between 700,000 and 1.6 million people in the US who had Covid-19 have lost their sense of smell or have had a change in their sense of smell that lasts for more than 6 months. This is likely an underestimate, the authors of Washington University School of Medicine in St. Louis said.

The study suggests that most people eventually regain their sense of smell, but some may never regain it. The authors consider this a concern because, by comparison, prior to the pandemic, only 13.3 million adults aged 40 and older had what scientists call olfactory dysfunction (OD) or chronic olfactory dysfunction (COD).

“These data suggest an emerging public health problem of OD and the urgent need for research focused on the treatment of COVID-19 COD,” the study said.

A survey from last year found that 72% of people with Covid-19 recovered their sense of smell after a month, but for some it is a much slower process.

“With the long-term burden of disease from this, we’re going to be dealing with this for literally decades,” said John Hayes, director of the Sensory Evaluation Center at Penn State’s College of Agricultural Sciences. Hayes did not participate in this investigation, but did conduct research in the area.

He thinks the estimated number of people in the study with this problem is conservative and the problem could affect many millions more.

While a long-term loss of sense of smell may sound trivial compared to other symptoms of long-term Covid, such as chronic fatigue or heart problems, not being able to smell could be dangerous, he said. A 2014 study found that people who have lost their sense of smell are more than twice as likely to experience dangers, such as eating spoiled food, than those who did have a sense of smell. A loss of sense of smell has also been linked to depression in previous studies.
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“It’s really a result of appetite and social relationships, as people who have lost their sense of smell may not be able to detect if they have body odor, and it could also affect diet,” Hayes said.

Hayes said his research with Covid-19 patients has shown that they have experienced three different types of long-term olfactory disorders.

Some lose or have a decreased sense of smell. Some have a poor sense of smell, where instead of flowers, for example, someone would smell foul-smelling feet. Others may have what Hayes calls a sort of “ghost limb syndrome” for sense of smell, where people smell things that aren’t there, such as a lingering chemical or burning odor.

dr. Sandeep Robert Datta, a neurobiologist at Harvard Medical School who has studied why people with Covid-19 lose their sense of smell, said this is an important line of research.

“We’ve never really made a formal estimate of how many people are struggling with this,” Datta said. “This is truly an unusual event in terms of olfactory dysfunction and an unprecedented consequence of a pandemic never seen before.”

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Unless someone breaks their nose in an accident or has had some other type of head trauma, it’s uncommon for younger people to lose their sense of smell, especially due to a virus. As people get older, some lose some sense of smell. One study found that 60 to 70% of people aged 80 and older have some degree of smell impairment. Other studies suggest it may affect fewer people, but this loss usually happens slowly over time; an acute loss is unusual.
Scientists are still trying to figure out why people with Covid-19 lose their sense of smell. Datta said the consensus seems to be that there is a disruption in the support cells in the nose. He said the neurons responsible for detecting odors are unlikely to be directly attacked by the virus.

“After that, there’s still a lot of mystery about what’s going on and in a lot of labs, including mine, we’re continuing to work on this problem,” Datta said.

Understanding how Covid-19 has distorted a person’s sense of smell will be important for scientists to determine how they can help regain the sense of smell, if it doesn’t return on its own.

Some Covid clinics have long offered some sort of physiotherapy for the nose and train people’s sense of smell by exposing them to certain smells so they can try to relearn them. Studies show that this may work for some people, but not everyone.

“I recently had a patient call me and ask what could be done and frankly I don’t have any good recommendations yet,” Hayes said.

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