One of the telltale symptoms of COVID-19 is loss of smell and taste. And some patients are left with long-term loss of smell or even smell distortions.
It’s why the topic of smell training and other potential therapies have come to the forefront of many conversations regarding regaining the ability to smell, a sense that is much more important than some may think.
Dr. Steven Munger — director of the University of Florida’s Center for Smell and Taste, and co-director of the UF Health Smell Disorders Program — said a loss of sense of smell from COVID-19 or smell disorders are more common than many realize.
In fact, 12.4% of people over 40 years old, or more than 16 million people, in the United States suffer from either the inability to smell (anosmia) or distorted smell (parosmia). That’s about four times the prevalence of uncorrectable vision impairments in the same age group.
What’s more, the diagnosis can present much more significant concerns than merely the inability to enjoy your favorite scents.
“Smell disorders are serious health issues,” Munger said. “They impact nutrition as your perceptions of food flavors are altered. They put you in danger of hazards (such as) fires, gas leaks and spoiled foods. And they disconnect you from the world around you, changing the way you interact with other people and your environment. Depression is not uncommon with the advent of a smell disorder like anosmia.”
Aside from smell disorders, scientists are still working to pinpoint exactly how COVID-19 causes the loss of smell.
“Our best evidence at the moment suggests that the virus infects supporting cells in the olfactory epithelium, the tissue inside your nose containing the sensory cells that can detect odors and send that signal to your brain,” Munger said. “We suspect that this infection of the sensory cells disrupts the local environment and damages the sensory cells, hampering their ability to pass on the odor signal.”
Munger even wrote an op-ed for USA Today last month explaining why a loss of smell from COVID-19 deserves more attention. Anosmia, he said, is much more than just an inconvenience. For example, those suffering with loss of smell might find meals unpalatable and a chore to eat without an accompanying aroma.
“Good nutrition is compromised, as some increase their intake of sugar, fat and salt to enhance food palatability while others find it challenging to eat at all,” Munger wrote in his op-ed. “Older adults with hyposmia or anosmia even have a significantly higher rate of death over the long term. These are consequential health issues that cannot go unaddressed.”
Although COVID-19 has wreaked havoc on millions worldwide, Munger wrote, the pandemic may give scientists the opportunity to finally help millions of people who have suffered without smell long before the coronavirus was a thought.
The problem with regaining sense of smell is that therapeutic options are limited and vary depending on the cause, Munger said.
For example, those whose loss of smell stems from nasal polyps and other impediments to proper air flow in the nose might find success in surgical treatments. Topical steroids may be effective in some cases of inflammatory sinonasal disease, he said. However, there is no clear-cut therapy for lose of smell stemming from viral infections such as COVID-19.
“A process called ‘smell training’ has shown some promise to improve smell function in some individuals with post-viral smell loss, but more studies are needed to confirm its effectiveness (especially in COVID-19 cases) and to understand for what types of cases it might be most effective,” Munger said.
Smell training, or olfactory training, involves actively sniffing the same four scents every day, concentrating on spending around 20 seconds on each scent.
There is hope, though, and scientists are hard at work researching ways to treat anosmia. Munger said laboratories in the UFCST are developing gene-therapy strategies to treat anosmia in those born without a sense of smell, and stem-cell therapies also hold great promise, though both are still in the preclinical research stage.
“At the UFCST, we are also working to develop better smell testing that will make it easier to diagnose smell disorders or even to screen for associated health issues such as COVID-19,” he said.