One of the most distressing symptoms of COVID-19, loss of taste, is a separate entity, not a side effect of loss of smell. And one of the most common symptoms of coronavirus infection. This was confirmed by research by scientists from the Monell Chemical Senses Center in the USA. The results of the study were published in the journal Chemical Senses.
In the article, scientists described a meta-analysis of the frequency of loss of taste in patients suffering from COVID-19. This is the largest such analysis so far, as it covered as many as 241 previous studies, published between May 2022 and June 2022. A total of 139,000 people participated in these studies.
According to the scientists, 32,918 reported some form of loss of taste among the patients studied. The analysis shows that the overall assessment of the frequency of the loss of this sense was 37%. "So about 4 in 10 COVID-19 patients experience this symptom," says lead author Dr. Mackenzie Hannum.
Loss of taste has been reported as one of the main symptoms of COVID-19 from the beginning of the pandemic. It comes in a variety of forms: from mild disturbances to partial and complete losses. Despite the fact that it is a troublesome and quite disturbing symptom, researchers did not know for a long time whether it was a derivative of the loss of smell or a separate disease entity. Doubts arose from the fact that before the pandemic, "pure" loss of taste was quite a rare phenomenon and in most cases it was only associated with a disturbance in the perception of smells, e.g. with a runny nose.
After analyzing all the data, the Monell researchers also found that age and gender had a large influence on the occurrence of loss of taste. Middle-aged people (36 to 50 years old) experienced it most often in all age groups, and women more often than men.
Scientists used different approaches to assess the loss of taste: self-descriptive reports or direct measurements. "The description itself is more subjective and is made through questionnaires, interviews, and medical records," explains Dr. Hannum. - At the other extreme, we have direct taste measurements. These are definitely more objective, and they are carried out with the help of test kits containing various sweet, s alty, sometimes bitter-sour solutions administeredparticipants in the form of, for example, drops or sprays ".
Based on their previous findings on loss of smell, the Monell researchers expected that direct testing would be a more sensitive measure of taste loss than their own reports.
This time, however, it turned out that whether the study used self-reports or direct measurements did not affect the estimated frequency of loss of flavor. In other words: Objective Direct Measurements and Subjective Self Reports were equally effective in detecting loss of taste.
"First of all, our study showed that loss of taste is a real, clear symptom of COVID-19 that should not be linked to loss of smell," emphasizes co-author Dr. Vicente Ramirez. - Especially since there is a huge difference in the treatment of these two symptoms. "
Scientists emphasize that taste assessment should become standard clinical practice, e.g. during routine annual checkups. It is an important symptom of several serious medical problems: in addition to COVID-129, it can be caused by certain medications, chemotherapy, aging, multiple sclerosis, certain inflammatory and vascular diseases of the brain, Alzheimer's disease or even stroke.
"Now is the time to find out why COVID-19 affects taste so strongly and begin to reverse or repair the losses it causes," the authors conclude.