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About 5% of adults who have been infected with COVID-19 globally (at least 27 million people) may lose their sense of smell or taste for the long term, new research published in The BMJ indicates.
Researchers found that loss of smell may be long-lasting in 5.6% of patients, and 4.4% may not recover their sense of taste. At 30 days after infection, only 74% of patients reported smell recovery and 79% of patients reported taste recovery. After 180 days, those numbers increased to 96% and 98%, respectively.
Sensitivity analyses of the data suggest this could be an underestimate, say the authors, led by Benjamin Kye Jyn Tan, MBBS, Yong Loo Lin School of Medicine, National University of Singapore.
In an accompanying editorial, Paolo Boscolo-Rizzo, MD, Department of Medical, Surgical and Health Sciences, Section of Otolaryngology, University of Trieste, Italy, and colleagues write that the findings suggest health systems may not be prepared for the resulting treatment needs.
They note that loss of smell and taste reduce quality of life with loss of everyday pleasures. People can also experience anorexia, aversion to some foods, anxiety, depression, and malnutrition without the senses.
“[G]iven that an estimated 550 million cases of covid-19 have been reported worldwide as of July 2022, large numbers of patients will be seeking care for these disabling morbidities. Health systems should therefore be ready to provide support to these patients who often report feeling isolated when their symptoms are overlooked by clinicians,” Boscolo-Rizzo and colleagues write.
More Women Affected
Tan’s team found that women may be particularly affected. The data show that female sex was associated with poorer recovery of both smell and taste. Also, people who had greater initial severity of dysfunction and nasal congestion were associated with poorer smell recovery only.
“While most patients are expected to recover their sense of smell or taste within the first three 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 for associated sequelae.”
The findings of the study, published online Wednesday, may help general practitioners and otolaryngologists counsel patients with smell and taste disorders after their COVID infections.
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 for whom the risk is more prevalent.
The international team 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 total, 18 observational studies involving 3699 patients met the study criteria. Most of the studies (14) were conducted in hospitalized patients, and four came from the community setting.
The researchers then used a technique known as “cure modelling” 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.
Limitations include that the studies analyzed varied in quality and depended on self-reports.
Authors and editorialists report no relevant financial relationships.
Marcia Frellick is a freelance journalist based in Chicago. She has previously written for the Chicago Tribune, Science News, and Nurse.com, and was an editor at the Chicago Sun-Times, the Cincinnati Enquirer, and the St. Cloud (Minnesota) Times. Follow her on Twitter at @mfrellick.