Millions still without a sense of smell or taste after Covid-19

Are you still struggling with your sense of smell after a fight with Covid-19? You are far from alone.

An estimated 5% of patients with confirmed cases of Covid-19 – some 27 million people worldwide – have experienced a long-lasting loss of smell or taste, according to a new analysis.

In which Analysis published in The BMJ on Wednesday (the peer-reviewed medical journal of the British Medical Association), Researchers evaluated 18 previous studies on smell and taste loss across multiple continents and across different demographic groups. About three quarters of those affected by loss of taste or smell regained these senses within 30 days.

Recovery rates improved over time, but around 5% of people reported “persistent dysfunction” six months after being infected with Covid-19.

The analysis suggests that the loss of smell and taste could be an ongoing problem that requires more research and healthcare resources for patients struggling with long-term symptoms.

Loss of smell has been linked to higher mortality rates in older adults and has been shown to have major impacts on people’s emotional and psychological well-being, said Dr. Zara Patel, a rhinologist at Stanford University who was not involved in the BMJ research.

“That there are now millions of people around the world with reduced olfactory ability — that could just be a new public health crisis,” Patel said.

Loss of smell was one of the clearest markers of Covid-19 in the early days of the pandemic.

“You could follow the pandemic around the world” by analyzing Google searches for smell loss, Patel said.

The BMJ analysis provides a broad overview of odor studies around the world and over time. Data from nearly 3,700 patients were included in the analysis.

Studies from North America, Europe, and Asia were all included in the analysis, which found that women are less likely than men to regain their sense of smell and taste. Patients with more severe nasal congestion were also less likely to recover.

The analysis showed a steady increase in the proportion of patients who regained their sense of smell over time. After 30 days, about 74% of patients had recovered; after 90 days it was up to 90%. After six months, around 96% of patients said they could smell again.

Scientists are beginning to understand how Covid-19 affects olfactory function.

The coronavirus often causes swelling in the olfactory cleft, that is, in the passages the upper part of the nasal cavity where humans perceive smell and process taste beyond basic tastes like sour or bitter.

The researchers believe the virus doesn’t initially infect the olfactory neurons, but instead attaches itself to supporting cells that help the neurons provide a signaling pathway.

Patients who have experienced a loss of smell after Covid-19 represent a unique subgroup, said Dr. Aria Jafari, a rhinologist at the UW Medicine Sinus Center in Seattle, who was not involved in the new analysis. “They tend to get better and get better quite quickly, which makes sense based on the cells affected.”

Jafari said about half of his patients who lack the sense of smell likely had Covid-19 at some point. Many experienced a dramatic impact on their well-being as a result of the loss.

“They tend to be upset by the loss of their sense of smell. It’s such an important part of our everyday lives and what makes us human,” Jafari said, adding that he’s treated a professional chef, a chocolatier and others whose livelihoods depend on their ability to determine smell and taste. “The most common thing I hear is that it leads to social isolation and a feeling of being disconnected from the world and society as you know it. And that can be really annoying.”


Jafari said many patients also describe a transitional period “that can be distressing” when their senses return, in which they smell things that aren’t there — like burning rubber or smoke — or notice unusual foul smells.

People who are unable to smell or sense aromas may be more likely to suffer from psychiatric disorders, depression and anxiety, Jafari said. In one extreme case, Jafari said he treated a patient who was malnourished after losing his sense of smell and taste.

Smell underlies how we interact with each other and navigate the world, and dictates “your first impression of other people, the people we choose for sexual encounters or for lifelong partners,” Patel said. cues from smells could subconsciously affect people’s attraction to others based on their underlying genetics, Studies suggest.

The analysis is based on studies with data provided by patients themselves. Patel said this may underestimate the true toll of olfactory disorders and skew some of the research, as people are sometimes unable to appreciate how much sensitivity they’ve lost.

The authors of the study agreed.

“Many previous studies have shown that objective smell tests can identify far more people with smell loss than if we asked them to self-report,” wrote Professor Song Tar Toh, study author and head of the Department of Otorhinolaryngology & Neck Surgery at Singapore General Hospital, in an email. “The actual number of people affected is likely to be far higher than our estimate.”

Patel suspects the true rate of odor disorders in those who have experienced Covid-19 may be over 20%. It may be that women are not more likely to struggle with recovery, but are more aware of a prolonged deficit in their ability to smell.

“Females, on average, have a more keen sense of smell than males,” Patel said. “We know that people with more keen senses of smell and taste are much more likely to recognize when they have a loss and are more likely to care about a loss.”

Jafari said the BMJ analysis is generally consistent with his clinical experience and observations of patient recovery.

“It’s nice to bring together data from around the world to better understand what’s going on and to take some variability out of these analyzes that are specific to a patient population or institution,” Jafari said. “It increases the overall body of evidence to support what we as sinus surgeons are seeing in our offices.”

Initial versions of the Omicron variant appeared to affect the sense of smell less than previous waves of Covid-19, Patel said.

But the latest sub-variant, BA.5, could reverse this trend.

“We don’t have enough data to know for sure yet,” Patel said. “I now see an upward trend again in my clinic.”

Treatments are available for people who have lost their sense of taste and smell due to Covid-19.

Structured smell training — in which patients sniff essential oils like lemon, clove, eucalyptus, and rose twice a day to stimulate different types of neurons — can teach the brain to recognize different smells. Doctors often prescribe a steroid flush for the sinuses to reduce inflammation and aid in exercise.

Some emerging evidence suggests that omega-3 fatty acid supplements may be helpful for patients with olfactory disorders.

Patel et al are investigating other treatments, including nasal injections of platelet-rich plasma and electrical stimulation.

Patel said she hopes research funding and public interest in odor and taste disorders will continue to grow, allowing researchers to dig deeper and unlock new treatments.

Before the pandemic, “it was the orphan, Cinderella feel,” Patel said. “Only after so many millions of people have been affected or loved ones have been affected do people understand the tremendous impact smell and taste have on your quality of life.” Millions still without a sense of smell or taste after Covid-19

Fry Electronics Team

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