Nearly one in four COVID-19 patients with olfactory dysfunction reported that they did not regain their sense of smell 60 days after their loss, a large prospective study in Europe showed.
Among nearly 2,600 people with confirmed SARS-CoV-2 infection, the frequency of olfactory reporting in patients with olfactory dysfunction was 85.9% in mild COVID-19 cases, 4.5% in moderate cases, and 6.9% in severe cases. urgent, Jerome Lechien reported. , MD, PhD, from the University of Paris Saclay in France, and co – authors in the Journal of Internal Medicine.
Approximately 24% of patients did not receive topical treatment 60 days after onset of dysfunction. When a smaller sample of patients was evaluated with objective olfactory tests, 15.3% still showed deficiency at 60 days and 4.7% had not recovered at 6 months.
“Olfactory dysfunction is more common in mild forms of COVID-19 than in moderate-to-diagnostic forms, and 95% of patients regain their sense of smell at 6 months after infection,” Lechien said. in a statement.
The study evaluated 2,581 mobile and hospitalized COVID-19 patients identified at 18 European hospitals between March 22 and June 3, 2020. In total, 2,194 patients (85.0%) had moderate disease, 110 had moderate disease. (4.3%), and 277 (10.7%) had COVID-19 hypertension. Mild, moderate, severe, and acute patients were defined using WHO COVID-19 severity scoring.
The majority of participants were female (62.9%), but the proportion of females was higher in the mild patient group than in others (P.= 0.001). Patients with mild COVID-19 had an average age of 42; mean age was 69 for moderate COVID-19 and 72 for severe disease. About 84% of the sample was Caucasian.
Participants answered olfactory and gustatory questions based on the smell and taste component of the CDC Health and Nutrition Examination Survey. The average duration of olfactory dysfunction reported by patients was 21.6 days.
Of the total patients in the study, 233 completed objective olfactory assessments, including 181 with moderate and 52 with moderate-to-diagnostic COVID-19. Target assessments identified hyposmia or anosmia in 54.7% of patients with mild disease and 36.6% of patients with moderate-to-severe disease (P.= 0.001).
Average values on the Sniffin Sticks test – olfactory assessment using 16 odor pens – were significantly lower in the mild patient group than in patients with moderate-to-severe COVID-19 (P.= 0.001). Baseline average values of Sniffin Sticks tests improved significantly after 30 and 60 days of follow-up (P.= 0.001). A higher baseline prognosis of objective olfactory masses predicted a strong 2-month loss (P.<0.001).
The main idea underlying the higher incidence of anosmia in mild COVID-19, according to Lechien and colleagues, is that milder conditions develop a stronger local immune response to disease. The inflammation associated with that response, however, could lead to a stronger weakening in olfactory cells, the researchers suggested.
That olfactory dose in COVID-19 is so common that it supports the need for primary care physicians, ENT specialists, and neurologists to advise patients about the likelihood of recovery and people who are at risk of recognizing persistent olfactory dysfunction, said Lechien and colleagues. “Considering both thematic and fair data, we may suggest that the 60-day recovery rate ranges from 75% to 85%,” they wrote.
The study has several limitations, including a lack of clinical or imaging olfactory examination at the time of infection. Many critically ill patients had a nasogastric feeding tube, which delayed assessment and may have skewed some of the results.
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The study was unfunded.
The researchers did not report any disclosure.