A presentation planned for the American Academy of Neurology’s 73rd Annual Meeting, being held virtually in April, suggests the sense of smell and taste could be lost for up to 5 months after infection.
“While COVID-19 is a new disease, previous research shows that most people lose their sense of smell and taste in early stages of the illness,” said study author Johannes Frasnelli, MD, of the University of Quebec at Trois-Rivieres in Canada. “We wanted to go further and look at how long that loss of smell and taste lingers, and how severe it is in people with COVID-19.”
The study team evaluated COVID-19–related persistent chemosensory dysfunction (CD) in a cohort of more than 800 Quebec healthcare workers. “CD is now recognized as a major symptom of COVID-19,” the authors wrote. “While published studies have investigated and quantified persistent CD in up to 20% of patients, very few have examined the duration, severity and trajectory of chemosensory impairments in patients with persisting CD.”
The cross-sectional observational study focused on healthcare workers, 84.1% women, who received a positive diagnosis for SARS-CoV-2 with a nasopharyngeal viral swab; they all were recruited through the Quebec National Institute of Public Health, 4 months after diagnosis.
Researchers used an online 64-item questionnaire examining self-evaluated olfactory, gustatory, and trigeminal impairments, as well as clinical and epidemiological consequences of the infection, including a previously validated CD-home test (CD-HT).
The questionnaire evaluated both smell and taste on a scale from 0 to 10 (0: no perception; 10: very strong perception).
Participants answered the questionnaire on average 150.1 (standard deviation [SD]: 31.1) days postdiagnosis. Results indicate that average self-reported smell ratings were 8.98 (1.62) pre-infection, 2.85 (3.74) during the acute phase, and 7.41 (2.46) when the participants responded. Corresponding results were 9.20 (1.34), 3.59 (3.67), and 8.05 (2.20) for taste.
In 580 respondents who indicated a compromised sense of smell during the acute phase, average smell rating at the time they answered the questionnaire was 6.89 (SD 2.52) compared with 9.03 (1.61) before the infection. In fact, researchers noted that 51.2% of respondents reported not regaining olfactory functions at the time of testing. When assessed with the CD-HT, 18.4% had persistent loss of smell. The authors added that no significant sex differences were observed in acute or persistent smell loss.
On average, patients ranked their sense of smell at a 7 out of 10 after the illness, compared with a 9 out of 10 before the infection.
“Our results show that an impaired sense of smell and taste may persist in a number of people with COVID-19,” Dr. Frasnelli said. “This emphasizes the importance of following up with people who have been infected, and the need for further research to discover the extent of neurological problems associated with COVID-19.”
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