The findings illustrate that olfactory problems are common not only during the acute COVID-19 phase but also “in the long run” and that these problems should be “taken into consideration” when following up these patients, study investigator Johannes Frasnelli, MD, professor, department of anatomy, Université du Québec à Trois-Rivières, said in an interview.
Loss of the sense of smell can affect quality of life because it affects eating and drinking, and may even be dangerous, said Dr. Frasnelli. “If your sense of smell is impaired, you may unknowingly eat spoiled food, or you may not smell smoke or gas in your home,” he said. In addition, Dr. Frasnelli noted that an impaired sense of smell is associated with higher rates of depression. The findings will be presented at the annual meeting of the American Academy of Neurology in April.
Research shows that about 60% of patients with COVID-19 lose their sense of smell to some degree during the acute phase of the disease. “But we wanted to go further and look at the longer-term effects of loss of smell and taste,” said Dr. Frasnelli.
The analysis included 813 health care workers in the province of Quebec. For all the patients, SARS-CoV-2 infection was confirmed through testing with a nasopharyngeal viral swab.
Participants completed a 64-item online questionnaire that asked about three senses: olfactory; gustatory, which includes tastes such as sweet, sour, bitter, salty, savory and umami; and trigeminal, which includes sensations such as spiciness of hot peppers and “coolness” of mint.
They were asked to rate these on a scale of 0 (no perception) to 10 (very strong perception) before the infection, during the infection, and currently. They were also asked about other symptoms, including fatigue.
Most respondents had been infected in the first wave of the virus in March and April of 2020 and responded to the questionnaire an average of 5 months later.
The vast majority of respondents (84.1%) were women, which Dr. Frasnelli said was not surprising because women predominate in the health care field.
The analysis showed that average smell ratings were 8.98 before infection, 2.85 during the acute phase, and 7.41 when respondents answered the questionnaire. The sense of taste was less affected and recovered faster than did the sense of smell. Results for taste were 9.20 before infection, 3.59 during the acute phase, and 8.05 after COVID-19.
Among 580 respondents who indicated a compromised sense of smell during the acute phase, the average smell rating when answering the questionnaire was 6.89, compared to 9.03 before the infection. More than half (51.2%) reported not regaining full olfactory function.
The fact that the sense of smell had not returned to normal for half the participants so long after being infected is “novel and quite striking,” said Dr. Frasnelli.
However, he noted, this doesn’t necessarily mean all those with a compromised sense of smell “have huge problems.” In some cases, he said, the problem “is more subtle.”