Sense of smell can be altered for 5 months or more after acute SARS-CoV-2 infection, Canadian researchers reported.
Nearly one in five healthcare workers who had a compromised sense of smell when they first were infected reported persistent olfactory changes 150 days later, said Johannes Frasnelli, MD, of the University of Quebec at Trois-Rivieres, and colleagues, in a preliminary report released in advance of the American Academy of Neurology annual meeting.
The findings are based on 813 Quebec healthcare workers who tested positive for SARS-CoV-and completed online questionnaires and home chemosensory tests an average of 5 months after diagnosis. Most participants (84%) were women.
“These were workers who were in the middle-age range,” co-author Nicolas Dupre, MD, of CHU de Quebec-Laval University in Quebec City, told MedPage Today. “The vast majority of them had mild COVID symptoms.”
The questionnaires evaluated 64 items involving olfactory, gustatory, and trigeminal impairments. Participants rated their senses on a scale from 0 to 10, with 0 representing no perception of taste or smell, and 10 representing a very strong perception.
Part of the home chemosensory test involved smelling or tasting common household items like peanut butter, jam, vinegar, or coffee, Frasnelli said. Smell and taste were evaluated only at the post-COVID period; participants described their pre-COVID and acute COVID senses retrospectively.
Average self-reported smell ratings were 8.98 before COVID-19, 2.85 during acute COVID, and 7.41 when the respondents answered the questionnaire. These numbers were 9.20, 3.59, and 8.05, respectively, for taste.
A total of 580 respondents said they had a compromised sense of smell during their COVID-19 acute phase; about half (51.2%) said they had not regained olfactory functions at the time of testing. When assessed with home chemosensory tests, 134 of 810 respondents (18.4%) showed a persistent loss of smell.
It’s not clear what these early results mean, said Jerome Lechien, MD, PhD, of Paris Saclay University in France, who wasn’t part of the study. “The authors assessed self-reported sense dysfunction without psychophysical testing,” Lechien noted. “This is particularly problematic because there would exist a mismatch between the patient’s sense of perception (subjective) and the real perception (semi-objective or psychophysical testing),” he told MedPage Today.
“We demonstrated that many patients have reported that they completely lost their smell, but at the psychophysical testing, they smell, reporting results in a range of normative data,” Lechien said. Earlier this year, Lechien led research in Europe that showed about 24% of COVID-19 patients did not subjectively recover olfaction 60 days after dysfunction started. When a smaller group was evaluated with objective olfactory tests, 15.3% still showed deficiency at 60 days and 4.7% had not recovered olfaction at 6 months.
In-depth laboratory tests are part of next steps for this cohort, especially for people who reported persistent deficits, Dupre noted. The researchers also plan to follow these participants to see whether any other COVID-related problems linger.
“Will they describe difficulties with their memory, with their concentration, with their ability to do different tasks?” Dupre asked. “At this stage, we do not believe that there will be a long-term impact, other than on smell. But we need follow-up and detailed assessment before we can conclude.”
The study was supported by the Foundation of the University of Quebec at Trois-Rivieres and the Province of Quebec.