In the study, published in the journal BMJ, researchers say that loss of smell may be long-lasting in almost 6% of patients, and more than 4% may not recover their sense of taste.
About 5% of adults who have been infected with COVID-19 (at least 27 million cases around the world) may lose their sense of smell or taste for the long term, new research suggests. Thirty days after being infected, only 74% of patients had regained their sense of smell and 79% said they could taste again. After 180 days, those numbers increased to 96% and 98%, respectively.
Researchers believe the true numbers could be worse, say the authors.
In an accompanying editorial, other scientists say the findings suggest health systems may not be prepared for the treatment needs of these patients. They note that loss of smell and taste reduces the quality of life with the loss of everyday pleasures. People can also experience anorexia, aversion to some foods, anxiety, depression, and malnutrition without the senses.
The research team found that women may be particularly affected. The data shows that women had poorer recovery of both smell and taste.
“While most patients are expected to recover their sense of smell or taste within the first 3 months, a major subpopulation of patients might develop long-lasting dysfunction,” the authors write. “These patients require timely identification, [personalized] treatment, and long-term follow-up.”
Changes in the ability to smell or taste are common with COVID-19; about 40%-50% of people report these changes globally. But little is known about how long the changes last and who is more at risk. The international team of researchers combed databases for studies of adults with COVID-19-related changes to smell or taste and studies that described factors associated with these changes and how long it took people to recover.
In all, 18 studies involving 3699 patients met the study criteria. Most of the studies (14) were conducted on hospitalized patients.
The researchers then used a technique known as “cure modeling” to estimate self-reported rates of smell and taste recovery and identify key factors associated with length and likelihood of recovery. Recovery rates increased with each month, reaching a peak of 96% for smell and 98% for taste after 6 months, the authors write.
The findings of the study may help doctors counsel patients with smell and taste disorders after their COVID-19 infections.
Parvathy Sukumaran 
