Two international studies confirm that for the majority of patients with respiratory infections who lose the sense of smell, this is due to COVID-19. The disease also often results in both loss of taste and the other senses in the mouth. A researcher from Aarhus University has contributed to the new results.
If you have had COVID-19, then forget about enjoying the smell of freshly made coffee. At any rate, two major international studies document that there is frequently a loss of smell and that this often lasts for a long time in cases of COVID-19
Alexander Wieck Fjaeldstad, is associate professor in olfaction and gustation at Aarhus University, and is behind the Danish part of the study.
The study shows that the average loss of the sense of smell was 79.7 on a scale from 0-100 - which indicates a large to complete sensory loss, says the researcher. In addition, the studies show that the loss of smell is very probably the best predictor of COVID-19 among patients with symptoms of respiratory diseases.
"This emphasises how important it is to be aware of this symptom, as it may be the only symptom of the disease," says Alexander Wieck Fjaeldstad, who also stresses only around half of patients with a loss of smell have gotten their sense of smell back after forty days.
"This differs from the picture we see with other viral infections and causes long-term discomfort for patients, both in relation to food and social contact, while at the same time causing them worry."
In addition to the loss of the sense of smell, the sense of taste was also significantly reduced, to 69.0 on a scale from 0-100, just as the remaining sense of feeling in the mouth was also reduced, this time to 37.3 on a scale from 0-100.
"While the loss of smell in itself removes the ability to sense the aroma of food, the simultaneous loss of the other senses make it difficult to register what you're eating. Putting food in your mouth can therefore become a decidedly unpleasant experience," explains Alexander Wieck Fjaeldstad.
A total of 23 nationalities and over 4,500 COVID-19 patients from all over the world have responded to the researchers' questionnaire.
"The study is of interest both to patients suffering sensory loss as well as clinicians and researchers who work with diagnostics and following-up on COVID-19. It shows that the loss of smell is specific to COVID-19, which is both relevant in relation to recognising the infection, and because it indicates that the sense of smell is closely linked to how SARS-CoV-2 infects the body."
Previously, researchers have based the correlation between COVID-19 and the loss of the chemical senses on smaller studies, while these studies collect large amounts of data from countries all over the world.
"The collaboration on the projects also entails a dialogue between researchers from all over the world, which makes it possible to share knowledge and ideas in order to promote the research field," says Alexander Wieck Fjaeldstad and continues: "The results are in line with our own national studies and pave the way for future studies on risk factors for permanent sensory loss, along with a better understanding of the consequences of these sensory losses for the patients. Among the aspects being studied are which factors are associated with a milder or briefer loss of the sense of smell and how this loss is associated with the rest of the course of the disease. The collection of data is continuing and will result in additional publications with even more participants."
The results have been published in the scientific journal Chemical Senses.
Background for the results
The studies are based on a survey translated into 23 languages and answered by more than 4,500 people infected with Covid-19.
The studies have been carried out in collaboration with the Global Consortium for Chemosensory Research.
Funded by James and Helen Zallie.
Alexander Wieck Fjældstad
Department of Clinical Medicine