More than 27 million adults worldwide could experience long-term changes to their sense of smell or taste after having COVID-19, research suggests today.
Researchers led by the National University of Singapore say this is about 5% of the 550 million confirmed COVID-19 cases to date.
Globally, about 40-50% of people report a loss of taste and / or smell after having COVID-19, but little is known about the clinical course of these symptoms or how many patients develop persistent problems.
An international research team trawled databases for studies of adults with COVID-19 related changes to smell or taste and studies that described factors associated with these changes and time to recovery.
They found 18 observational studies involving 3,699 patients that met their criteria, four of which were conducted in the community setting and 14 in a hospital setting.
The team used cure modelling to estimate self-reported rates of smell and taste recovery and identify key factors associated with the duration and likelihood of recovery.
They found smell loss may persist in 5.6% of patients, while 4.4% may not recover their sense of taste. At 30 days after initial infection, only 74% of patients reported smell recovery and 79% of patients reported taste recovery.
Recovery rates increased each month, reaching a peak of 96% for smell and 98% for taste after six months.
However, women were less likely to recover their sense of smell and taste than men.
The researchers acknowledge several limitations in their analysis but say it was a well designed study with rigorous search methods, with robust findings.
“Our findings are likely to be of substantial relevance to general doctors and otolaryngologists in the counselling of patients with smell and taste disorders post-COVID-19,” they conclude.
Tan BKJ, Han R, Zhao JJ et al. Prognosis and persistence of smell and taste dysfunction in patients with COVID-19: meta-analysis with parametric cure modelling of recovery curves. *BMJ* 28 July 2022. DOI: 10.1136/bmj 2021 069503
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