- A recent study found that many people recovering from COVID-19 still lack the sense of smell up to 5 months later.
- Experts say having COVID-19 can cause inflammation that damage key nerves. It can even affect a part of the brain that deals with senses.
- Despite the long recovery time, experts stress that most people will regain their sense of smell and taste.
With the start of the COVID-19 pandemic, one symptom has stood out for being a distinctive marker of the disease: the loss of smell.
Even in mild cases people often reported being unable to smell and subsequently experience a loss of taste.
A recent study presented by the American Academy of Neurology found that many people recovering from COVID-19 still lack these senses up to 5 months later.
What the study found
The study involved 813 healthcare workers who tested positive for COVID-19. Of these, 580 people lost their sense of smell during the initial illness.
And of this group, nearly 300 participants, or 51 percent, still hadn't regained their sense of smell 5 months later. Of the total number of participants, 527 had lost their sense of taste and 200 people, or 38 percent, had still not regained their sense of taste 5 months later.
Researchers found that the majority of those tested didn't regain their sense of smell entirely. Sense of taste returned to about 8 out of 10 among those tested.
Why do people lose their sense of taste and smell with COVID-19?
Temporary loss of smell is known as anosmia. It's a neurological symptom and one of the earliest and most commonly reported indicators of COVID-19.
In fact, some studies suggest that it's one of the strongest indicators of COVID-19 compared to other symptoms like fever and cough.
Anosmia can be caused by something as simple as the common cold, which irritates the nose's lining, or it can be the result of a more serious infection that affects the brain or nerves.
“Sense of taste is linked to sense of smell,” said Dr. David Goldberg, internist and infectious disease specialist with NewYork-Presbyterian Medical Group Westchester. “Most of us think taste is linked to the tongue and mouth, but smell contributes a huge amount to taste. If you lose your sense of smell, you will lose your sense of taste. They really are inseparable.”
Why are these senses slow to recover?
Goldberg pointed out that the loss of smell indicates nerve damage.
“The olfactory nerve is involved in the sense of smell,” Goldberg said. “With nerve damage, whether it's loss of smell with COVID-19 or a stroke, the recovery is slow. Any kind of neurological damage has slow recovery. It is measured in months or years.”
Dr. Robert Glatter, emergency physician at Lenox Hill Hospital, said that another possibility for the lingering symptoms could be the damage to cells in the brain.
“With COVID-19 we know that the virus can penetrate a small area of the brain known as the olfactory bulb, which is integral for the sense of smell,” he said. “The virus likely leads to death of some of the cells in the olfactory bulb, leading to a prolonged effect we are seeing in these patients.”
A sign of long COVID-19
The lingering of these symptoms brings them under the umbrella term of long-haul COVID-19, which is a subsequent health issue that doctors are still learning about.
Long-haul COVID-19 refers to the lingering of symptoms for several months after the virus has been cleared from the body. In addition to the loss of smell and taste, other long-haul COVID-19 symptoms include fatigue, brain fog, and memory issues.
Glatter pointed out that the virus will cause inflammation that affects the cells.
“Loss of smell and taste is linked to inflammation resulting from SARS-CoV-2,” Glatter said. “The inflammation leading to loss of smell or taste is part of the ongoing constellation of symptoms we refer to as long COVID.”
Researchers in Switzerland found that as many as 1 in 3 people who had milder COVID-19 experienced lingering symptoms after 6 weeks.
Another study found that of those hospitalized in Italy, more than 87 percent reported experiencing at least one symptom 2 months after being released from the hospital. The lingering loss of the sense of smell and taste is yet another symptom of long COVID-19.
“These findings are pretty consistent with my experience,” Goldberg added. “Most of us who are infectious disease specialists have seen many cases of coronavirus and my sense is that these findings are right. Half of the people with COVID-19 more or less do lose sense of smell and/or taste, and many are still not 100 percent in 5 months.”
How to treat loss of smell and/or taste
There's no current treatment for the loss of the sense of smell and taste with respect to COVID-19.
“It's the damage — it has been done. Let it heal,” Goldberg said. “Nothing we know of will help it get better faster. People may make a full recovery in 1 to 2 years. But if we extrapolate from other nerve damage, people can continue to improve after 5 months, and some people never will.”
While not a life-threatening side effect, it's certainly one that can deeply impact the quality of life.
“When we think about senses, we think about sight and hearing. We take the others for granted,” Goldberg said. “Taste and smell have a huge impact on quality of life. If you can't enjoy your food, it's terrible. People are distressed by this. It's an awful complication.”
It can also put patients at risk for other potential problems. Imagine not being able to smell gas or smoke in a home, or not being able to taste spoiled food.
“These are things we take for granted that can place us in the crosshairs of significant danger,” Glatter said.
While there's no way to speed up the healing process, Glatter believes that 80 to 90 percent of people who are affected by this will recover. However, some may be dealing with it over a longer period of time.