A study published in the scientific journal European Archives of Psychiatry and Clinical Neuroscience found a link between loss of smell or taste after passing COVID-19 with memory problems.
Studies conducted before the COVID-19 pandemic showed that loss of smell could be a early sign of the impending onset of Alzheimer’s disease.
There is evidence in the scientific literature that this sensory disorder may appear years before the first cognitive symptomssuggesting a link between the brain regions responsible for memory and the interpretation of olfactory stimuli.
In this new work, a group of Brazilian researchers analyzed the clinical data of 701 patients treated for moderate or severe COVID-19 at the Hospital das Clínicas between March and August 2020.
Evaluations conducted six months after hospital discharge showed that patients with the most severe taste and smell disorders post-COVID-19 achieved the worse results in cognitive tests, especially when these involved memory, and that the results of the tests did not correlate with the severity of their condition in the acute phase of the disease.
“Smell is an important link with the outside world and is closely related to past experiences”
“The smell is an important link to the outside world and is closely related to past experiences. The smell of a cake can evoke memories of a grandmother, for example. In terms of brain connections, smell interacts much more strongly with memory than with sight and hearing,” says otorhinolaryngologist Fábio Pinna, last author of the article that collects the study.
The mean hospital stay for the entire group of patients studied was 17.6 days. Their mean age was 55.3 years. Just over half (52.4%) were men. A slightly higher proportion (56.4%) required intensive care for complications of the disease, and just over a third (37.4%) were intubated.
Smell and taste were evaluated six months after hospital discharge through questionnaires previously standardized for this type of study and that also covered aspects related to quality of life.
Moderate or severe gustatory deficit (reduced sense of taste) was the most frequent sensory complication (20%), followed by moderate or severe olfactory deficit (18%), moderate or severe deficit in both smell and taste (11 %), and parosmia (9%), which is a distortion of olfactory perception, so that a smell that was previously enjoyed becomes unpleasant, for example.
Up to 12 of the participants reported having olfactory hallucinations (perceiving odors unknown to others) and nine gustatory hallucinations (perceiving flavors without eating anything). In both cases, the majority said that the hallucinations only occurred after suffering from COVID-19. In response to a question about their general health status, 10.1 percent chose poor or very poor, 38.5 percent chose fair, and 51.4 percent chose good or very good.
were investigated psychiatric symptoms such as anxiety and depressionalso through standardized questionnaires, and neuropsychological tests were applied to measure cognitive functions such as memory, attention and speed of reasoning.
Finally, statistical techniques were used to analyze all the results in order to detect correlations between the neuropsychiatric symptoms and sensory dysfunctions.
Subjects reporting parosmia were found to have more memory problems than others, while those with moderate or severe taste deficits performed significantly worse on a test used to assess episodic memory and attention. Subjects who reported moderate or severe loss of both smell and taste were also found to have significantly impaired episodic memory.
“We did not find no psychiatric symptoms [como la ansiedad o la depresión] that was associated with loss of smell and taste, but as expected, we observed that attention and episodic memory were more impaired in patients with more chemosensory alterations.
This finding supports the hypothesis that COVID affects cognitionand that the damage in this area does not only have psychosocial or environmental causes”, details Rodolfo Damiano, first author of the article.
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