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Association between loss of smell in after SARS-CoV-2 infection and cognitive impairment

Older adults frequently suffer persistent cognitive impairment after recovery from SARS-CoV-2 infection and this is correlated with persistent loss of smell (anosmia), according to a cohort study in Argentina by the University of Texas.

Researchers at UT Health San Antonio are studying COVID-19 patients, to understand why cognitive problems persist and whether the disease changes brains in ways that elevate the risk of developing Alzheimer's disease, writes Jon Hamilton for NPR. Their findings so far are worrying, writes NPR.

For example, PET scans taken before and after a person develops COVID-19 suggest that the infection can cause changes that overlap those seen in Alzheimer's. And genetic studies are finding that some of the same genes that increase a person's risk of getting severe COVID-19 also increase the risk of developing Alzheimer's.

Alzheimer's diagnoses also appear to be more common in patients in their 60s and 70s who've had severe COVID-19, says Dr Gabriel de Erausquin, a professor of neurology at University of Texas Health San Antonio. “It's downright scary,” he said, adding that he and his colleagues had noticed that mental problems seem to be more common in COVID-19 patients who lose their sense of smell, perhaps because the disease has affected a brain area called the olfactory bulb.

“Persistent lack of smell, it's associated with brain changes not just in the olfactory bulb but those places that are connected one way or another to the smell sense,” he says. Those places include areas involved in memory, thinking, planning and mood.

COVID-19's effects on the brain also seem to vary with age, he noted. Even people in their 30s seem more likely to develop anxiety and depression. “In older people, people over 60, the foremost manifestation is forgetfulness,” he says. “These folks tend to forget where they placed things, they tend to forget names, they tend to forget phone numbers. They also have trouble with language; they begin forgetting words.”

The symptoms are similar to those of early Alzheimer's and doctors sometimes describe these patients as having an Alzheimer's-like syndrome that can persist for many months.

“Those people look really bad right now,” De Erausquin says. “And the expectation is that it may behave as Alzheimer's behaves, in a progressive fashion. But the true answer is we don't know.”

Dr Sudha Seshadri, founding director of the Glenn Biggs Institute for Alzheimer's and Neurodegenerative Diseases at UT Health San Antonio, said the possibility that COVID-19 might increase the risk of Alzheimer's is alarming.

“Even if the effect is small, it's something we're going to have to factor in because the population is quite large,” she says.

In the US alone, millions of people have developed persistent cognitive or mood problems after getting COVID-19. It may take a decade to know whether these people are more likely than uninfected people to develop Alzheimer's in their 60s and 70s, Seshadri says.

Studies of people who have had COVID-19 may help scientists understand the role infections play in Alzheimer's and other brain diseases. Previous research has suggested that exposure to certain viruses, including herpes, can trigger an immune response in the brain that may set the stage for Alzheimer's.

“If one understands how the immune response to this virus is accelerating [Alzheimer's] disease, we may learn about the impact of other viruses,” Seshadri says.

Study details

Olfactory dysfunction and chronic cognitive impairment following SARS-CoV-2 infection in a sample of older adults from the Andes mountains of Argentina.

Hernan P. Zamponi, Leonardo Juarez-Aguaysol, Gabriela Kukoc, Maria Eugenia Dominguez, Belén Pini, Eduardo G Padilla, Maria Calvó, Silvia Beatriz Molina-Rangeon, Gonzalo Guerrero, Mariana Figueredo-Aguiar, Emiliano Fumagalli,
Agustín Yécora, Traolach S Brugha, Sudha Seshadri, Heather M. Snyder.
Gabriel A. de Erausquin,

Presented at AAIC 29 July 2021

Abstract

Background
COVID-19 has affected more than 150 million people. The causal coronavirus, SARS-CoV-2 has infected twice as many individuals who have remained asymptomatic. COVID-19 includes central nervous system (CNS) manifestations and may result in chronic neuropsychiatric sequelae. Risk factors for COVID-19 sequelae overlap with those for Alzheimer’s disease (AD), particularly older age and ApoE4 status. The Alzheimer’s Association Consortium on Chronic Neuropsychiatric Sequelae of SARS-CoV-2 infection (CNS SC2) established harmonized definitions, ascertainment and assessment methodologies to evaluate and longitudinally follow up cohorts of older adults with variable exposure to COVID-19. We present preliminary data from CNS SC2 in a prospective cohort of 234 older adult Amerindians from Argentina.

Method
Participants are ≥ 60 years recruited from the health registry of the Province of Jujuy containing all SARS-CoV-2 testing data (regardless of clinical status and of the result of the testing). We randomly invite older adults stratified by testing status regardless of symptom severity, a minimum of 3 months after clinical recovery (maximum 6 months); refusal to participate is <45%. Assessment includes interview with the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) and Clinical Dementia Rating scale; neurocognitive assessment; emotional reactivity scale; and neurological assessment including semiquantitative olfactory function test, motor function, coordination and gait. We present here the results of olfactory testing and cognitive assessments.

Result
We assessed 233 infected participants and 64 controls. Average duration of formal learning is 9.35 ± 2.6 years and mean age is 66.7 ± 5.13 years. Normative data for the local population were available for Word list, Corsi Blocks, Oral Trails and Five Digit Tests and were used to normalize Z-scores and categorize the sample in 3 groups: normal cognition (NC,44.6%); memory only impairment (MOI,21%); and multiple domain impairment (MDI,34.4%). Individuals with MDI presented severe alterations in short-term memory; semantic memory; naming; executive function and attention compared to NC or MO groups (Table 1). Severity of cognitive impairment was significantly correlated with severity of olfactory dysfunction (χ2 = 13.82; p= 0.003) but not severity of acute COVID-19.

Conclusion
Older adults frequently suffer persistent cognitive impairment after recovery from SARS-CoV-2 infection; cognitive impairment is correlated with persistent anosmia.

 

Full article Doctors Worry That Memory Problems After COVID-19 May Set The Stage For Alzheimer's – NPR (Open access)

 

AAIC presentation – Olfactory dysfunction and chronic cognitive impairment following SARS-CoV-2 infection in a sample of older adults from the Andes mountains of Argentina (Open access)

 

See more from MedicalBrief archives:

 

Increased risk of death and serious illness among COVID-19 survivors

 

One-in-10 have long-term effects 8 months after mild COVID-19 — Swedish study
30% of COVID-19 patients have lingering symptoms 6 months later — Washington study

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