New research Thursday aims to quantify a life-altering aftereffect of covid-19: a lingering loss of smell, also known as anosmia. The study estimates that up to 1.6 million people in the U.S. have experienced chronic anosmia lasting at least six months following their coronavirus infection.
Anosmia can be caused by different things, including respiratory viral infections like covid-19. But it took some time before anosmia was recognized as a clear symptom of covid-19—one that might even be more common among mild cases. Often, this loss of smell is accompanied by a loss of taste, the two senses being closely dependent on each other. Sometimes, people can also experience parosmia, or a distorted sense of smell that can cause everyday scents to smell like trash, sewage, or other putrid odors.
Studies have estimated that anywhere from 30% to 80% of covid-19 sufferers can develop some level of anosmia. But research has indicated that most (upwards of 90%) regain their sniffer sense in as little as two weeks, possibly because the infection tends not to damage the olfactory nerve itself but the cells supporting it. Since so many people have contracted covid-19 in the U.S, though, even a relatively rare complication like long-term anosmia can still affect plenty of people.
This new study, published Thursday in JAMA Otolaryngology – Head & Neck Surgery, seems to be one of the first to try gauging the toll of chronic covid-related anosmia in the U.S. The authors were compelled to study the issue after seeing many of these patients in their clinics.
“In the last couple of months, my colleagues and I noted a dramatic increase in the number of patients seeking medical attention for olfactory dysfunction.” study author Jay Piccirillo, a otolaryngologist at Washington University in St. Louis and an editor at JAMA Otolaryngology, told Gizmodo in an email.
Piccirillo and his team estimated a range of cases, based on projections of covid-19’s spread, the odds of someone developing anosmia from infection, and the likelihood of chronic anosmia. In the most likely scenarios, somewhere between 700,000 to 1.6 million Americans (as of August 2021) have experienced a loss or change in their sense of smell lasting more than six months as a result of covid-19 so far, they found. This tally includes those who have parosmia, though no specific numbers are available for that group. It’s possible these numbers are an underestimate, the authors say, and the pandemic isn’t over—many more Americans may contract covid-19 in the months to come.
There are treatments that are thought to improve a person’s chances of recovering from covid-related anosmia, such as smell training, and there are clinical trials ongoing now that are testing out experimental treatments. But for those unlucky enough to still have trouble smelling things months down the road, the odds of recovery are slim.
“Most cases (~90%) of viral associated anosmia resolve within two weeks—including covid. The prognosis for long-term olfactory dysfunction (ie. >6 months) is not good. Less than 20% can expect to recover smell after 6 months,” Piccirillo said. Ultimately, he added, about 5% of all anosmia cases will lose some or all of their sense of smell permanently.
There have been many direct and indirect impacts of the pandemic, from millions of covid-19 deaths to the resurgence of other diseases. But permanent anosmia may be one of the most distinct lifelong consequences of infection. A recent study by French researchers this month even found that anosmia may be the long-term symptom most likely to be associated with a lab-confirmed case of covid-19. Long after the pandemic has faded away, many people will no longer be able to enjoy certain basic pleasures of life, like a delicious meal or the familiar scents of loved ones.