- There is growing concern about the effects of COVID-19 on many parts of a person’s body besides the respiratory system.
- Researchers have shown that COVID-19 symptoms can persist after recovery and lead to neurological problems.
- Research presented at the Alzheimer’s Association International Conference (AAIC) 2021 further confirms these findings, including making links between COVID-19 and signs of Alzheimer’s disease.
Scientists presenting research at the AAIC 2021, held online and in Denver, CO, have found links between COVID-19 and longer-term cognitive issues, including biological signs of Alzheimer’s disease.
The findings lay the ground for larger longitudinal studies to explore in more detail the neurological effects of COVID-19.
Long COVID
COVID-19 is primarily a respiratory condition. The Centers for Disease Control and Prevention (CDC) note that COVID-19 symptoms can include mild respiratory problems, more severe low oxygen levels and shortness of breath, and life threatening issues affecting multiple organs across a person’s body.
Much research has been done to understand these acute symptoms, and there are now many different treatment options open to clinicians.
However, the effects of COVID-19 do not always end after the acute phase of the condition.
As the pandemic progressed, anecdotal evidence suggested many people who had recovered from COVID-19 were still experiencing a variety of symptoms. This became known as long COVID.
According to Dr. A. V. Raveendran, of the Government Medical College in Manjeri, India, and his colleagues, symptoms of long COVID can include “profound fatigue, breathlessness, cough, chest pain, palpitations, headache, joint pain, myalgia and weakness, insomnia, pins and needles, diarrhea, rash or hair loss, impaired balance and gait, neurocognitive issues, including memory and concentration problems, and worsened quality of life.”
Neurological issues under the spotlight
At the AAIC 2021, researchers presented a number of studies that focus on the neurological issues associated with the longer-term effects of COVID-19.
According to Dr. Heather M. Snyder, Alzheimer’s Association vice president of medical and scientific relations, “[t]hese new data point to disturbing trends showing COVID-19 infections leading to lasting cognitive impairment and even Alzheimer’s symptoms.”
“With more than 190 million cases and nearly 4 million deaths worldwide, COVID-19 has devastated the entire world. It is imperative that we continue to study what this virus is doing to our bodies and brains. The Alzheimer’s Association and its partners are leading, but more research is needed,” she said.
Cognitive issues
In one study, Dr. Gabriel De Erausquin, of the University of Texas Health Science Center at San Antonio Long School of Medicine, as well as colleagues from the Alzheimer’s Association leading a consortium on links between COVID-19 and the nervous system, looked at neurological issues in Amerindians from Argentina who had recovered from acute COVID-19.
The 300 participants were assessed 3–6 months after having COVID-19. The researchers found that more than 50% of the participants had issues with forgetfulness and that around 25% also experienced executive dysfunction and language issues.
The researchers noted an association between these cognitive issues and loss of smell but not with the severity of the initial SARS-CoV-2 infection.
According to Dr. Erausquin, “[we are] starting to see clear connections between COVID-19 and problems with cognition months after infection.”
“[It is] imperative we continue to study this population, and others around the world, for a longer period of time to further understand the long-term neurological impacts of COVID-19.”
Signs of Alzheimer’s disease
In another study presented at the conference, Prof. Thomas M. Wisniewski, professor of neurology, pathology, and psychiatry at New York University Grossman School of Medicine, and his colleagues explored the possible links between COVID-19 and clinical signs of Alzheimer’s disease.
The researchers took blood plasma samples from 310 people who had been admitted to hospital with COVID-19. Of those, 158 had neurological symptoms associated with COVID-19 — most frequently, confusion — while 152 did not.
In the patients who did not have cognitive issues prior to developing COVID-19 but then did develop neurological symptoms, the researchers found an increase in biological markers associated with Alzheimer’s disease, brain injury, and neuroinflammation, compared with the patients who did not have neurological symptoms.
These included total tau, neurofilament light, glial fibrillary acid protein, phosphorylated tau, and ubiquitin carboxyl-terminal hydrolase L1. The researchers also noted a correlation between some of these markers and C-reactive peptide.
Prof. Wisniewski explains: “These findings suggest that patients who had COVID-19 may have an acceleration of Alzheimer’s-related symptoms and pathology. However, more longitudinal research is needed to study how these biomarkers impact cognition in individuals who had COVID-19 in the long term.”
Oxygen deprivation
Researchers also presented findings looking at the relationship between cognitive issues linked to COVID-19, and people’s physical condition and blood oxygen levels.
Dr. George D. Vavougios, a postdoctoral researcher for the University of Thessaly in Greece, and his colleagues recruited 32 people who had been hospitalized with mild or moderate COVID-19 and then discharged 2 months later.
Just over half of the participants had issues with cognitive decline, including short-term memory impairment as well as multidomain impairment without short-term memory issues.
The researchers found a correlation between worse levels of cognitive scores and being older, having a larger waist circumference, and a higher waist-to-hip ratio.
The participants also took a 6-minute walking test. After accounting for sex and age, the researchers found a link between worse memory and thinking scores and lower blood oxygen levels.
Dr. Vavougios says: “A brain deprived of oxygen is not healthy, and persistent deprivation may very well contribute to cognitive difficulties. These data suggest some common biological mechanisms between COVID-19’s dyscognitive spectrum and post-COVID-19 fatigue that have been anecdotally reported over the last several months.”
Growing body of evidence
The research presented at the conference is also supported by a new study published in The Lancet, which drew on data from over 80,000 participants. Having accounted for a range of factors, the researchers behind this study found that people who had recovered from COVID-19 had significant cognitive issues compared with a control group.
Speaking to Medical News Today, Dr. Adam Hampshire, of the Department of Brain Sciences, Dementia Research Institute, Care Research and Technology Centre, Imperial College London in the United Kingdom, and the corresponding author of the study, said the study emerged out of ongoing research he was conducting when the pandemic took hold.
“By coincidence, when the pandemic accelerated in the U.K., I was in the process of collecting one of the largest online surveys of cognitive abilities to have been conducted.”
He went on to say: “Several peers wrote to me noting that the study could be extended to address questions about the potential impact of the virus, and of the pandemic more broadly, on cognition and mental health. I had been thinking along similar lines so decided to try and help address this important question.”
Dr. Hampshire said that the findings make clear a link between cognitive dysfunction and COVID-19 but that more research needs to be done to confirm these findings, explore them in more detail, and understand what, if any, causal mechanisms may be underlying them.
“We have identified a worrying association between [COVID-19] illness and cognitive deficits. We also have ruled out many potentially confounding factors.”
“What is needed is a combination of longitudinal studies that determine how long these deficits last and to disentangle causality, as well as brain imaging studies to understand the underlying neural basis. Such work is underway, and some of those studies are using our assessment software, which I have made available for this purpose.”
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