The loss of smell due to Covid-19 is much more common in those with a mild form of the virus than in moderate or severe forms.
And while that may be an initial consolation to patients, it is inevitable that they will want to know: When will I get my sense of smell back?
Research published in the Journal of Internal Medicine earlier this month attempts to answer that question.
After analyzing data from 2,500 patients in 18 European hospitals, the researchers found that all but 15.3 percent of those suffering a loss of smell had recovered it within two months and fewer than 5 percent remained without it after six months.
“Olfactory dysfunction is more prevalent in mild COVID-19 forms than in moderate-to-critical forms, and 95 percent of patients recover their sense of smell at 6-months post-infection,” said lead author Jerome R. Lechien, MD, PhD, MS, of Paris Saclay University.
Can take as little as two weeks
They found that more than a third of patients had regained their sense of smell within two weeks, which fits with how quickly people recover from simple nasal congestion due to a cold.
“The high prevalence of nasal symptoms could partly explain the occurrence of short OD (olfactory dysfunction) in some patients who rapidly recovered olfaction once the nasal symptoms disappeared,” they note. “Typically, OD occurring as part of the common cold is related to nasal congestion, rhinorrhea and olfactory cleft oedema and lasts 2‐3 weeks.”
While longer-lasting effects suggest a more extensive injury to olfactory cells, “the neurogenesis of the olfactory cells is possible but may take several months.”
For those patients, the authors point out that the vast majority (from 75 to 85 percent) have recovered within two months.
More common in younger patients
Among their other findings:
- Anosmia appeared to affect younger patients more than older ones.
- The loss of smell developed after the onset of other symptoms in 45 percent of the cases.
- Nearly 56 percent of the patients with OD also reported dysgeusia, an impairment of salty, sweet, bitter and sour tastes.
- Of the 1,363 patients with OD, 328 reported they had not regained their sense of smell within sixty days of when it started.