Scientists from the National University of Singapore found that about 5% of adults may develop long-lasting changes to their sense of smell or taste after COVID-19 infection.
With more than 550 million confirmed COVID-19 cases to date, this means that at least 15 million and 12 million adult patients may experience long-term smell and taste deficiencies, respectively.
Given the huge impact that loss of smell and taste can have on the quality of life and general health, this could contribute to the rising burden of long COVID.
The research is published in The BMJ and was conducted by Benjamin Kye Jyn Tan et al.
Change in the sense of smell and taste is common in patients with COVID-19, with 40-50% of people on average reporting these symptoms globally.
In the study, researchers analyzed 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.
In all, 18 studies involving 3,699 patients were included. Four of the studies were conducted in the community setting and 14 studies in the hospital setting.
The researchers then used a mathematical technique known as cure modeling to estimate self-reported rates of smell and taste recovery and identify key factors associated with the duration and likelihood of recovery.
They found that 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 with each passing month, reaching a peak of 96% for smell and 98% for taste after six months.
The team found women were less likely to recover their sense of smell and taste than men, while patients with greater initial severity of smell loss and those with nasal congestion were less likely to recover their sense of smell.
One patient the researchers spoke to said she has yet to recover her sense of smell, even though it has been over 27 months since the initial infection.
However, they note that the virus variant of SARS-CoV-2 was not reported in association with smell or taste recovery.
The researchers say that while most patients are expected to recover their sense of smell or taste within the first three months, many people might develop long-lasting dysfunction.
If you care about COVID, please read studies about a new drug that could prevent COVID-19, and scientists find antibodies that can neutralize Omicron.
For more information about COVID, please see recent studies that new air filters could rapidly kill COVID-19, and results showing many people with COVID-19 get deadly ‘black fungus’ disease.
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