COVID odor loss tops its lead as a predictor of cognitive impairment

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Preliminary results of new research indicate that loss of smell, rather than disease severity, predicts persistent cognitive impairment one year after SARS-CoV-2 infection.

The findings provide important insight into the long-term cognitive impact of COVID-19, said study researcher Gabriela Gonzalez Aleman, PhD, professor at the Pontifical Catholic University of Argentina, Buenos Aires, Medscape Medical News.

The more information that can be gathered about the factors that increase the risk of this cognitive effect, “the better we can track it and begin to develop ways to prevent it,” she said.

The results were presented at the Alzheimer’s Association International Conference (AAIC) 2022.

Memory and attention problems

COVID-19 has infected more than 570 million people worldwide. Gonzalez Aleman said the related infection may lead to long-term sequelae, including neuropsychiatric symptoms.

In the elderly, sequelae of COVID-19 may resemble early Alzheimer’s disease (AD), and the two conditions may share risk factors and blood biomarkers.

Dr. Gabriela Gonzalez Aleman

The new study highlights one-year results from a large prospective cohort study from Argentina. The researchers used measures to assess the long-term consequences of COVID-19 in older adults recommended by the Alzheimer’s Association Consortium on Chronic Neuropsychiatric Consequences of SARS-CoV-2 (CNS SC2) infection.

Gonzalez Aleman said harmonizing definitions and methodologies for studying the impact of COVID-19 on the brain allows consortium members to compare study results.

The investigators used the health registry in the province of Jujuy, located in the far northwest of Argentina. The registry includes all SARS-CoV-2 test data for the entire region.

The investigators randomly invited adults aged 60 years and over from the registry to participate in the study. The current analysis included 766 adults aged 55–95 years (median age 66.9 years; 57% female) with a median of 10.4 years of education. Argentina’s education system includes 12 years of pre-university study.

The researchers arranged the subjects by polymerase chain reaction (PCR) test condition. Of the total, 88.4% contracted COVID and 11.6% had controls (people without COVID).

The participants’ neurocognitive assessment included four cognitive domains: memory, attention, language, and executive function, and an olfactory test that quantifies the degree of olfactory impairment. Cognitive impairment was defined as Z-scores below – 2.

The researchers divided the participants into groups according to cognitive performance. These included normal cognition, memory impairment only (single domain; 11.7%), impairment of attention and executive function without memory impairment (two domains; 8.3%), and multiple domain impairment (11.6%).

“Participants showed a predominance of memory impairment as can be seen in Alzheimer’s disease,” notes Gonzalez Aleman. “A large group showed a range of memory and attention problems.”

About 40% of the study sample – but no controls – had an olfactory defect.

“All people with severe cognitive impairment also have anemia [loss of smell]“We established an association between poor olfactory performance and cognitive performance and impairment,” Gonzalez Aleman said.

The analysis showed that severity of olfactory loss, but not clinical status, significantly predicted cognitive impairment. “Therefore, loss of smell can be a good indicator of cognitive impairment after infection with the COVID-19 virus,” Gonzalez Aleman said..

For individuals over 60, she added, cognitive impairment can be permanent, as can olfactory dysfunction.

Results of a one-year telephone survey showed that about 71.8% of people had received three doses of the vaccine and 24.9% had received two doses. About 12.5% ​​of those who took three doses got infected again and 23.3% of those who took two doses got it again.

Longest follow up so far

Comment on searching for Medscape Medical NewsHeather Snyder, PhD, vice president of medical and scientific relations at the Alzheimer’s Association, noted that the study is the “longest follow-up we’ve seen” looking at the relationship between persistent loss of smell and cognitive changes after COVID-19 infection.

Snyder said the study had a “fairly large” sample size and was “unique” in that it was set up in a part of the country with central testing.

Snyder said the Argentine group is among the most advanced of those associated with CNS SC2.

Members of this Alzheimer’s Association consortium, Snyder said, regularly share updates of ongoing studies, which are in various stages and looking at the various neuropsychiatric effects of COVID-19. It is important to bring these groups together to determine what those effects are, she said, “because no single group will be able to do it alone.”

“We saw very early on that some individuals had changes in the brain, or changes in perception, and loss of the sense of smell or taste, which suggests a link to the brain.”

However, she added, “there’s still a lot we don’t know” about that connection.

The study was funded by the Alzheimer’s Association and FULTRA.

Alzheimer’s Association International Conference (AAIC) 2022. Abstract 66868. Filed July 31, 2022.

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