Loss of smell can hint at how severe your COVID infection is, study finds
Loss of smell, clinically known as anosmia, is often one of the first symptoms felt by people infected with the coronavirus, and often one of the only ones to show up.
Now, a new study of about 2,500 COVID-19 patients found that a faulty nose affects mostly those with mild cases — nearly 86% — while only slightly affecting people with moderate illnesses (4.5%) and severe-to-critical cases (6.9%).
Although 95% of people included in the study redeemed their sense of smell by six months post infection, some experienced the symptom for longer.
The findings were published Wednesday in the Journal of Internal Medicine.
Researchers analyzed self-reported answers to an online questionnaire from 2,581 COVID-19 patients staying in 18 different European hospitals between March 22 and June 3. The majority of patients included in the study were white.
Most cases of anosmia were found in patients with mild COVID-19 cases — those without evidence of viral pneumonia or abnormally low oxygen levels — and appear to happen more frequently in young patients than older ones, according to the study.
The lack of smell lasted for an average of about 22 days, but nearly a quarter of affected patients said they didn’t get their sense back until about two months later. Over a third of patients reported smell recovery within two weeks of losing it.
The researchers aren’t sure why people with milder cases are more likely to lose their smell, but they say it might have something to do with their immune response.
Patients with mild COVID-19 infections might be better able to fight the virus locally, meaning the pathogen doesn’t spread much beyond the upper respiratory tract. This creates some inflammation that interferes with nearby cells that help process smells, blocking their ability to do their job.
People who lack their sense of smell for longer periods of time have likely suffered more “injuries” to their olfactory cells, the researchers said, but regeneration of these cells is possible, it just might take “several months.”
Many coronavirus patients also report nasal congestion symptoms similar to the common cold, which sometimes includes a lack of smell for about two to three weeks, the team said. Temporarily clogged noses during coronavirus infection could “partly explain” why some people recover their sense of smell more quickly than others.
The researchers compared the self-reported answers to objective tests that confirmed if patients lost their sense of smell and also found anosmia to be more prevalent in individuals with mild COVID-19 cases (55%) and in those with moderate illnesses (37%) — people with clinical signs of pneumonia such as fever, cough and fast breathing.
Although just slightly annoying to some, permanently losing one’s sense of smell can lead to depression and anxiety in others, past research has found, but a group of neuroscientists at Harvard Medical School doubts this is the case for people who have recovered from COVID-19.
Their study found that the coronavirus doesn’t directly infect and/or damage sensory neurons that detect and send senses of smell to the brain, but rather affects supporting cells around them.
That’s “good news” because it means COVID-19 is unlikely to lead to permanent loss of smell, according to study author Sandeep Robert Datta, associate professor of neurobiology in the Blavatnik Institute at Harvard Medical School.
This story was originally published January 7, 2021 at 11:33 AM with the headline "Loss of smell can hint at how severe your COVID infection is, study finds."
