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Forgetfulness persisted in more than half of the older adults studied between 3 and 6 months after COVID-19, while one in four had additional cognitive problems, including language and executive disorders.
These issues correlated with persistent problems related to olfactory function, but not the severity of the original COVID-19 infection, according to results presented at the Alzheimer’s Association International Conference.
Several studies presented during the International conference of the Alzheimer’s Association examined cognitive problems in patients after COVID-19. Source: Adobe Stock
A second study on COVID-19 presented during the meeting showed that biological markers for brain injury, neuroinflammation and Alzheimer’s disease were “strongly” linked to neurological symptoms in patients with COVID-19. Additionally, a third study showed that people with cognitive decline after COVID-19 infection were more likely to have low blood oxygen levels after limited exercise and in poor general physical condition.
“We see clear links between COVID-19 and cognitive problems months after being infected.” Gabriel de Erausquin, MD, PhD, MSc, a specialist in neurology and psychiatry at the University of Texas Health Science Center at the San Antonio Long School of Medicine said in a press release. “It is imperative that we continue to study this population and others around the world over an extended period of time to better understand the long-term neurological effects of COVID-19.”
Cognitive impairment persists after COVID-19
In the first study, de Erausquin and colleagues looked at cognition and smell in adults aged 60 and over from Argentina who had COVID-19 infection. Researchers conducted interviews using the Schedules for Clinical Assessment in Neuropsychiatry (SCAN) and the clinical dementia rating scale; a neurocognitive assessment; a rating on an emotional reactivity scale; and a neurological exam that included a semiquantitative olfactory function test and tests of motor skills, coordination and gait.
The researchers studied 233 patients with COVID-19 and 64 control subjects; The mean age of the study population was 66.7 years. The reported mean duration of formal learning in the study cohort was 9.35 years. According to the results of the study, normative data was available for the local population for word lists, Corsi blocks, oral trails and five-digit tests. De Erausquin and colleagues used this information to normalize the Z-scores and classify the sample into three groups: normal cognition (44.6%), memory impairment only (21%), and multiple domain disorder (34.4%).
Individuals with multiple domain impairment experienced “severe changes” in short-term memory, semantic memory, naming, executive functions, and attention compared to individuals with normal cognitive or memory-only disabilities. The researchers found that the severity of cognitive impairment was significantly linked to the severity of olfactory dysfunction (P = 0.003), but not to the severity of acute COVID-19 infection.
“Older adults often experience persistent cognitive impairment after recovery from [COVID-19] Infection, ”wrote the researchers. “Cognitive impairment correlates with persistent anosmia.”
COVID-19 May accelerate AD-related symptoms, pathology
In another study presented during the Alzheimer’s Association International Conference, the researchers found that serum biomarkers for neuronal damage, neuroinflammation, and Alzheimer’s disease such as neurofilament light (NfL), total tau (t-tau), ubiquitin carboxyl -terminal hydrolase L1 (UCH-L1), glial fibrillary acid protein (GFAP), and phosphorylated tau (pTau-181) strongly correlate with neurological symptoms in patients with COVID-19. These results showed that patients who had COVID-19, according to the study results of Thomas M. Wisniewski, MD, Gerald J. and Dorothy R. Friedman Professor at New York University’s Alzheimer’s Disease Center and Professor of Neurology, Pathology, and Psychiatry at New York University’s Grossman School of Medicine and colleagues.
The researchers looked at patients admitted to three locations in New York University’s Langone Health System. They analyzed plasma from 310 patients, including 158 with positive COVID-19 test and neurological symptoms and 152 with positive COVID-19 test without neurological symptoms, and performed plasma biomarker assays for t-Tau, NfL, GFAP, UCH- L1, amyloid through beta 40, amyloid beta 42 and pTau-181.
Plasma biomarker assays for t-tau, NfL, GFAP and UCH-L1 showed a “significant increase” in patients with COVID-19 who had neurological symptoms compared to those with COVID-19 and had no neurological symptoms: NfL (bilateral t-test, P = 0.0003), GFAP (two-tailed t-test, P = 0.0098), UCH-L1 (two-tailed t-test, P = .0138) and t-tau (two-tailed t-test, P = .04). Study results showed that pTau-181 was also elevated in patients with COVID-19 who exhibited neurological symptoms (two-tailed t-test, P = .0141).
Thomas M. Wisniewski
Wisniewski and colleagues did not observe any significant differences with amyloid beta 1-40. However, both amyloid beta 1-42 and the pTau / amyloid beta 42 ratio showed significant differences between patients with neurological symptoms (two-sided t-test, P = 0.049 and P = 0.0017, respectively).
“These results suggest that patients who have had COVID-19 may have an acceleration in symptoms and pathology related to Alzheimer’s,” said Wisniewski. “However, more longitudinal research is needed to examine how these biomarkers affect the cognition of people with long-term COVID-19 illness.”
Lack of oxygen can contribute to cognitive problems
A third study on COVID-19, presented at the Alzheimer’s Association International Conference, looked at cognitive impairment and related health measures in 32 patients hospitalized with mild to moderate COVID-19. The researchers examined these patients two months after they were discharged.
George Vavougios, MD, PhD, a postdoctoral fellow at the University of Thessaly in Greece and colleagues found that 56.2% of these patients had cognitive decline. They also observed that short-term memory impairments and multi-domain impairments without short-term memory deficits were “the predominant patterns of cognitive impairment,” according to the press release. The Montreal Cognitive Assessment results correlated with age (P = 0.003), waist circumference (P = 0.028), waist-to-hip ratio (P = 0.042), and oxygen saturation during the 6-minute walk test (1st, 4th, and 6th minutes ; P <0.05). Several linear regression models showed that after adjustments for age and gender, oxygen saturation in the 6th minute of the 6-minute walk test correlated independently with the values of the Montreal Cognitive Assessment (beta = 0.579; P = 0.001).
“A brain without oxygen is not healthy, and persistent deficiency can very well contribute to cognitive difficulties,” Vavougios said in the press release. “These data suggest some common biological mechanisms between the dycognitive spectrum of COVID-19 and post-COVID-19 fatigue that have been anecdotally reported in the past few months.”
Relation:
Alzheimer’s Association. COVID-19 linked to long-term cognitive dysfunction, acceleration of Alzheimer’s symptoms. Available at: https://www.alz.org/aaic/releases_2021/covid-19-cognitive-impact.asp. Accessed July 29, 2021.
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Heather M. Snyder, PhD
As we work to understand the enduring effects of COVID-19 on our brains, there is a message for all of us: don’t get COVID-19. To be vaccinated. Follow guidelines from the CDC or your local health department.
It is important to note that even if you do get COVID-19, you will not experience definitive changes in the brain. Some people who have had COVID-19 experience brain changes. New research presented at the Alzheimer’s Association International Conference suggests that some individuals may have memory changes for extended periods of time. Other studies suggest that there are changes in the brain associated with the underlying AD pathology. What this means for long-term risk, whether it is reversible or persistent, is an unanswered question.
Heather M. Snyder, PhD
Vice President, Medical and Scientific Relations
Alzheimer’s Association
Disclosure: Snyder does not report any relevant financial information.
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