Research finds sensory disorders linked to memory problems in post-COVID patients

A new report analyzing hundreds of COVID patients has found that those who experience loss of smell or taste also demonstrate issues in cognitive function.

The study, published in the journal, European Archives of Psychiatry and Clinical Neuroscience, was conducted by researchers at University of São Paulo in Brazil. Investigators analyzed clinical data from 701 patients treated for moderate or severe COVID at Hospital das Clínicas, the hospital run by the University of São Paulo's Medical School (FM-USP) in São Paulo City, Brazil, between March and August 2020. 

According to the study, researchers assessed these patients’ smell and taste by means of questionnaires six months after they were discharged from the hospital. They found patients with the most severe post-COVID smell and taste disorders performed worst on cognitive tests, especially when these involved memory, and that test results did not correlate with the severity of their condition in the acute stage of the disease. 

The average age of the patients evaluated was 55.3 and on average, the group of patients stayed at the hospital 17.6 days. Just over half of these patients (52.4 percent) were male and 56.4 percent required intensive care for complications of the disease, and a little more than a third were intubated, according to the study.

Researchers found severe gustatory deficit (a reduced sense of taste) was the most frequently reported sensory complication (20 percent), followed by a moderate or severe olfactory deficit (18 percent), a moderate or severe deficit of both smell and taste (11 percent), and nine percent experienced parosmia, a distortion of olfactory perception.

Psychiatric symptoms such as anxiety and depression were evaluated, also using standardized questionnaires, and neuropsychological tests were applied to measure cognitive functions such as memory, attention, and speed of reasoning. Researchers used statistical techniques to analyze all the results with the aim of detecting correlations between neuropsychiatric symptoms and sensory dysfunctions. 

They found that subjects reporting parosmia six to nine months after COVID infection, had worse memory perception than the rest, while those with a moderate or severe gustatory deficit performed significantly worse in 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. 

“When older people start losing their sense of smell, it could be an early sign of dementia,” said Rodolfo Damiano, PhD candidate at FM-USP and first author of the report, in a statement. “They should see a physician for an assessment. People who notice moderate or severe loss of smell after having COVID, as well as their close relatives, should watch for signs of memory loss in the next few years.”